diff --git a/crates/server-api/src/lib.rs b/crates/server-api/src/lib.rs
index 3b448d409..cf8da3c28 100644
--- a/crates/server-api/src/lib.rs
+++ b/crates/server-api/src/lib.rs
@@ -225,6 +225,10 @@ impl_openapi_schema!(
     PasskeyLoginOptionsResponse,
     PasskeyLoginCompleteRequest,
     PasskeyAdditionOptionsRequest,
+    PasskeySummary,
+    PasskeyListResponse,
+    PasskeyAdditionResultRequest,
+    PasskeyAdditionResultResponse,
     PasskeyRegistrationOptionsRequest,
     PasskeyRegistrationOptionsResponse,
     PasskeyRegistrationCompleteRequest,
@@ -648,6 +652,33 @@ pub trait ServerApi {
         #[body] request: PasskeyRegistrationCompleteRequest,
     ) -> Result<server_api_responses::AuthPasskeyRegistrationComplete, RepositoryApiError>;
 
+    #[get(
+        "/api/auth/passkeys",
+        status = 200,
+        error_status = 400,
+        additional_error_statuses = [403, 500],
+        bearer_auth = true,
+        browser_auth = true
+    )]
+    async fn auth_passkey_list(
+        &self,
+        #[extension] context: ServerRequestContext,
+    ) -> Result<PasskeyListResponse, RepositoryApiError>;
+
+    #[post(
+        "/api/auth/passkeys/addition/result",
+        status = 200,
+        error_status = 400,
+        additional_error_statuses = [403, 500],
+        bearer_auth = true,
+        browser_auth = true
+    )]
+    async fn auth_passkey_addition_result(
+        &self,
+        #[extension] context: ServerRequestContext,
+        #[body] request: PasskeyAdditionResultRequest,
+    ) -> Result<PasskeyAdditionResultResponse, RepositoryApiError>;
+
     #[post(
         "/api/auth/passkeys/addition/options",
         status = 200,
@@ -4115,6 +4146,8 @@ impl RequestActor {
 pub struct WhoamiResponse {
     pub actor: Option<RequestActor>,
     pub session: BrowserSessionState,
+    /// Non-secret comparison evidence, never an authentication credential.
+    pub authentication_reference: Option<String>,
 }
 
 /// Browser navigation evidence, not an authorization grant or a generic 401 classification.
@@ -4142,6 +4175,8 @@ pub struct AuthBootstrapUserRequest {
 #[serde(deny_unknown_fields)]
 pub struct AuthUserResponse {
     pub user: AuthenticatedUser,
+    /// Comparison evidence for the exact newly issued session, not a credential.
+    pub authentication_reference: String,
 }
 
 /// Starts new-account registration only; an existing handle is never interpreted as key addition.
@@ -4158,16 +4193,64 @@ pub struct PasskeyRegistrationOptionsRequest {
     pub browser_origin: Option<String>,
 }
 
-/// Adds a credential to the current authenticated actor; target identity is never public input.
+/// Adds to the current actor. Expected identity/binding fields only fence stale UI;
+/// they never select an owner or authorize an addition.
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 #[serde(deny_unknown_fields)]
 pub struct PasskeyAdditionOptionsRequest {
+    pub expected_user_id: String,
+    pub expected_account_id: String,
+    pub expected_authentication_reference: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     #[cfg_attr(feature = "typescript", ts(optional = nullable))]
     pub browser_origin: Option<String>,
 }
 
+/// Safe account metadata. Neither the WebAuthn credential ID nor key material is exposed.
+/// Normal-login verification is observed verifier success, not inferred discoverability.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(deny_unknown_fields)]
+pub struct PasskeySummary {
+    pub key_reference: String,
+    pub created_at: String,
+    pub last_used_at: Option<String>,
+    pub normal_login_verified_at: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(deny_unknown_fields)]
+pub struct PasskeyListResponse {
+    pub user: AuthenticatedUser,
+    pub keys: Vec<PasskeySummary>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(deny_unknown_fields)]
+pub struct PasskeyAdditionResultRequest {
+    pub challenge_id: String,
+    pub expected_user_id: String,
+    pub expected_account_id: String,
+    /// Original options authentication reference; the current same-owner session may differ.
+    pub expected_authentication_reference: String,
+}
+
+/// Unknown is not proof that registration failed: completion may still be in flight.
+/// Saved proves the credential commit, not session issuance or current session health.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
+#[serde(tag = "status", rename_all = "snake_case", deny_unknown_fields)]
+pub enum PasskeyAdditionResultResponse {
+    Unknown {},
+    Saved {
+        user: AuthenticatedUser,
+        key: PasskeySummary,
+    },
+}
+
 #[derive(Debug, Serialize, Deserialize, JsonSchema)]
 #[cfg_attr(feature = "typescript", derive(ts_rs::TS))]
 #[serde(deny_unknown_fields)]
@@ -11642,6 +11725,10 @@ pub fn auth_api_typescript() -> String {
         AuthBootstrapUserRequest::decl(&config),
         AuthUserResponse::decl(&config),
         PasskeyAdditionOptionsRequest::decl(&config),
+        PasskeySummary::decl(&config),
+        PasskeyListResponse::decl(&config),
+        PasskeyAdditionResultRequest::decl(&config),
+        PasskeyAdditionResultResponse::decl(&config),
         PasskeyRegistrationOptionsRequest::decl(&config),
         PasskeyRegistrationOptionsResponse::decl(&config),
         PasskeyRegistrationCompleteRequest::decl(&config),
@@ -14069,7 +14156,8 @@ mod tests {
                 "display_name": "Hare",
                 "auth_method": "browser_session"
             },
-            "session": { "kind": "authenticated", "expires_at": "2026-10-20T00:00:00Z" }
+            "session": { "kind": "authenticated", "expires_at": "2026-10-20T00:00:00Z" },
+            "authentication_reference": "synthetic-session-reference"
         });
         let decoded = serde_json::from_value::<WhoamiResponse>(whoami.clone())
             .expect("server whoami fixture should match shared DTO");
@@ -14091,7 +14179,8 @@ mod tests {
                 "account_id": "account-1",
                 "handle": "hare",
                 "display_name": "Hare"
-            }
+            },
+            "authentication_reference": "synthetic-session-reference"
         });
         let decoded = serde_json::from_value::<AuthUserResponse>(auth_user.clone())
             .expect("server auth-user fixture should match shared DTO");
@@ -14264,7 +14353,7 @@ mod tests {
             serde_json::json!({"kind":"expired"}),
             serde_json::json!({"kind":"authenticated", "expires_at":null}),
         ] {
-            let value = serde_json::json!({"actor":null, "session":session});
+            let value = serde_json::json!({"actor":null, "session":session, "authentication_reference": null});
             let response: WhoamiResponse = serde_json::from_value(value.clone()).unwrap();
             assert_eq!(serde_json::to_value(response).unwrap(), value);
         }
@@ -14802,10 +14891,28 @@ mod openapi_artifact_tests {
             );
         }
         assert!(
-            serde_json::from_value::<PasskeyAdditionOptionsRequest>(serde_json::json!({})).is_ok()
+            serde_json::from_value::<PasskeyAdditionOptionsRequest>(serde_json::json!({})).is_err()
         );
     }
 
+    #[test]
+    fn passkey_addition_requires_expected_owner_and_binding() {
+        let expected = serde_json::json!({
+            "expected_user_id": "user-a", "expected_account_id": "account-a",
+            "expected_authentication_reference": "reference"
+        });
+        assert!(serde_json::from_value::<PasskeyAdditionOptionsRequest>(expected.clone()).is_ok());
+        for field in [
+            "expected_user_id",
+            "expected_account_id",
+            "expected_authentication_reference",
+        ] {
+            let mut missing = expected.clone();
+            missing.as_object_mut().unwrap().remove(field);
+            assert!(serde_json::from_value::<PasskeyAdditionOptionsRequest>(missing).is_err());
+        }
+    }
+
     #[test]
     fn auth_workspace_catalog_and_typed_header_contract_is_strict() {
         let document = canonical_openapi_document().expect("canonical OpenAPI contract must build");
diff --git a/crates/workspace-server/src/assignment_tracking_tests.rs b/crates/workspace-server/src/assignment_tracking_tests.rs
index 2e9085438..68af0424b 100644
--- a/crates/workspace-server/src/assignment_tracking_tests.rs
+++ b/crates/workspace-server/src/assignment_tracking_tests.rs
@@ -476,7 +476,8 @@ fn tracking_store_real_schema91_to92_retains_queue_cases_principals_audit_receip
                     (99, "Explicit hosting administrators and self-registration policy".into()),
                     (100, "Provisional users and scoped passkey activation".into()),
                     (101, "Durable explicit Subject body release".into()),
-                    (102, "Durable failed Subject creation recovery".into())
+                    (102, "Durable failed Subject creation recovery".into()),
+                    (103, "Passkey metadata and atomic addition results".into())
                 ]
             );
             for (table, rows) in retained.iter().zip(original.iter()) {
diff --git a/crates/workspace-server/src/auth.rs b/crates/workspace-server/src/auth.rs
index c46c54926..be0198975 100644
--- a/crates/workspace-server/src/auth.rs
+++ b/crates/workspace-server/src/auth.rs
@@ -228,13 +228,21 @@ fn resolve_whoami_sync(
     use server_api::{BrowserSessionState, WhoamiResponse};
     let anonymous = || WhoamiResponse {
         actor: None,
+        authentication_reference: None,
         session: BrowserSessionState::Anonymous {},
     };
     // Preserve the existing API-token precedence and fallback rules, including expired tokens.
     if let Some((actor, expires_at)) =
-        resolve_credentials_sync(store, bearer, session_token.clone())?
+        resolve_credentials_sync(store, bearer.clone(), session_token.clone())?
     {
+        let credential = match actor.auth_method {
+            ActorAuthMethod::ApiToken => bearer.as_deref(),
+            ActorAuthMethod::BrowserSession => session_token.as_deref(),
+        }
+        .ok_or_else(|| auth_error("auth_required", "authentication binding missing"))?;
+        let authentication_reference = Some(authentication_reference(&token_hash(credential)));
         return Ok(WhoamiResponse {
+            authentication_reference,
             actor: Some(actor),
             session: BrowserSessionState::Authenticated { expires_at },
         });
@@ -255,6 +263,7 @@ fn resolve_whoami_sync(
     if within_session_expiry_grace(&session.expires_at, Utc::now()) {
         return Ok(WhoamiResponse {
             actor: None,
+            authentication_reference: None,
             session: BrowserSessionState::Expired {},
         });
     }
@@ -262,6 +271,13 @@ fn resolve_whoami_sync(
     Ok(anonymous())
 }
 
+/// Domain-separated public comparison value; never accepted as a credential.
+pub(crate) fn authentication_reference(credential_hash: &str) -> String {
+    token_hash(&format!(
+        "passkey-authentication-reference:{credential_hash}"
+    ))
+}
+
 fn within_session_expiry_grace(expires_at: &str, now: DateTime<Utc>) -> bool {
     DateTime::parse_from_rfc3339(expires_at).is_ok_and(|expires_at| {
         expires_at <= now && now < expires_at + Duration::seconds(SESSION_EXPIRY_GRACE_SECONDS)
diff --git a/crates/workspace-server/src/implementation_result_tests.rs b/crates/workspace-server/src/implementation_result_tests.rs
index c5a7cd7d2..a669573e0 100644
--- a/crates/workspace-server/src/implementation_result_tests.rs
+++ b/crates/workspace-server/src/implementation_result_tests.rs
@@ -381,6 +381,10 @@ async fn implementation_result_v97_to_v98_preserves_legacy_bytes_receipts_and_no
             DROP TABLE ticket_implementation_results;
             DROP TABLE ticket_implementation_delegations;
             DROP TABLE merge_request_source_observations;
+            DROP TRIGGER passkey_metadata_insert;
+            DROP TABLE passkey_addition_receipts;
+            DROP TABLE passkey_metadata;
+            UPDATE __yoi_schema_migrations SET version=102 WHERE version=103;
             DROP TABLE subject_create_recoveries;
             UPDATE __yoi_schema_migrations SET version=101 WHERE version=102;
             DROP TABLE subject_worker_releases;
@@ -517,6 +521,10 @@ async fn mr_notification_upgrade_recovers_events_not_comments_and_retains_unknow
         // Reconstruct the prior composition before its new business capture existed.
         conn.execute_batch("DROP TRIGGER notification_mr_event; DROP TRIGGER notification_mr_source; DROP TRIGGER notification_implementation_result; DROP TRIGGER IF EXISTS implementation_delegation_capture;
             DROP TABLE ticket_implementation_results; DROP TABLE ticket_implementation_delegations; DROP TABLE merge_request_source_observations;
+            DROP TRIGGER passkey_metadata_insert;
+            DROP TABLE passkey_addition_receipts;
+            DROP TABLE passkey_metadata;
+            UPDATE __yoi_schema_migrations SET version=102 WHERE version=103;
             DROP TABLE subject_create_recoveries;
             UPDATE __yoi_schema_migrations SET version=101 WHERE version=102;
             DROP TABLE subject_worker_releases;
@@ -679,7 +687,11 @@ async fn mr_event_actors_preserve_self_suppression_in_capture_and_backfill() {
             if historical {
                 conn.execute_batch("DROP TRIGGER notification_mr_event; DROP TRIGGER notification_mr_source; DROP TRIGGER notification_implementation_result; DROP TRIGGER IF EXISTS implementation_delegation_capture;
                     DROP TABLE ticket_implementation_results; DROP TABLE ticket_implementation_delegations; DROP TABLE merge_request_source_observations;
-                    DROP TABLE subject_create_recoveries;
+                    DROP TRIGGER passkey_metadata_insert;
+            DROP TABLE passkey_addition_receipts;
+            DROP TABLE passkey_metadata;
+            UPDATE __yoi_schema_migrations SET version=102 WHERE version=103;
+            DROP TABLE subject_create_recoveries;
             UPDATE __yoi_schema_migrations SET version=101 WHERE version=102;
             DROP TABLE subject_worker_releases;
             UPDATE __yoi_schema_migrations SET version=100 WHERE version=101;
diff --git a/crates/workspace-server/src/passkey_results_schema.sql b/crates/workspace-server/src/passkey_results_schema.sql
new file mode 100644
index 000000000..6a670a615
--- /dev/null
+++ b/crates/workspace-server/src/passkey_results_schema.sql
@@ -0,0 +1,18 @@
+CREATE TABLE passkey_metadata (
+    credential_id TEXT PRIMARY KEY REFERENCES passkey_credentials(credential_id) ON DELETE CASCADE,
+    key_reference TEXT NOT NULL UNIQUE,
+    normal_login_verified_at TEXT
+);
+INSERT INTO passkey_metadata(credential_id, key_reference)
+    SELECT credential_id, lower(hex(randomblob(16))) FROM passkey_credentials;
+CREATE TRIGGER passkey_metadata_insert AFTER INSERT ON passkey_credentials
+BEGIN
+    INSERT INTO passkey_metadata(credential_id, key_reference)
+        VALUES (NEW.credential_id, lower(hex(randomblob(16))));
+END;
+CREATE TABLE passkey_addition_receipts (
+    challenge_id TEXT PRIMARY KEY,
+    credential_id TEXT NOT NULL UNIQUE REFERENCES passkey_credentials(credential_id) ON DELETE CASCADE,
+    user_id TEXT NOT NULL REFERENCES users(user_id) ON DELETE CASCADE,
+    authentication_reference TEXT NOT NULL
+);
diff --git a/crates/workspace-server/src/server.rs b/crates/workspace-server/src/server.rs
index c006bb28c..8ce931a21 100644
--- a/crates/workspace-server/src/server.rs
+++ b/crates/workspace-server/src/server.rs
@@ -6970,6 +6970,12 @@ fn generated_auth_contract_router(service: ServerApiContractService) -> Router {
         .merge(server_api::server_api_axum::hosting_settings_update(
             service.clone(),
         ))
+        .merge(server_api::server_api_axum::auth_passkey_list(
+            service.clone(),
+        ))
+        .merge(server_api::server_api_axum::auth_passkey_addition_result(
+            service.clone(),
+        ))
         .merge(server_api::server_api_axum::auth_passkey_addition_options(
             service.clone(),
         ))
@@ -8179,6 +8185,65 @@ impl server_api::ServerApi for ServerApiContractService {
         )
     }
 
+    async fn auth_passkey_list(
+        &self,
+        context: server_api::ServerRequestContext,
+    ) -> std::result::Result<server_api::PasskeyListResponse, server_api::RepositoryApiError> {
+        let headers = contract_request_headers(&context)?;
+        let api = self.auth_api();
+        api.store
+            .db_executor()
+            .run(move || {
+                let (user, _) = passkey_owner_authority(&api, &headers, false)?;
+                Ok::<_, ApiError>(server_api::PasskeyListResponse {
+                    keys: api.store.list_passkey_summaries(&user.user_id)?,
+                    user: user_response(user),
+                })
+            })
+            .await
+            .map_err(ApiError::into_repository_api_error)
+    }
+
+    async fn auth_passkey_addition_result(
+        &self,
+        context: server_api::ServerRequestContext,
+        request: server_api::PasskeyAdditionResultRequest,
+    ) -> std::result::Result<
+        server_api::PasskeyAdditionResultResponse,
+        server_api::RepositoryApiError,
+    > {
+        let headers = contract_request_headers(&context)?;
+        let api = self.auth_api();
+        api.store
+            .db_executor()
+            .run(move || {
+                let (user, _) = passkey_addition_authority(&api, &headers)?;
+                if user.user_id != request.expected_user_id
+                    || user.account_id != request.expected_account_id
+                {
+                    return Err(auth_error(
+                        "passkey_authentication_changed",
+                        "current authenticated owner does not match the operation owner",
+                    )
+                    .into());
+                }
+                let key = api.store.read_passkey_addition_result(
+                    &user.user_id,
+                    &request.expected_authentication_reference,
+                    &request.challenge_id,
+                )?;
+                Ok::<_, ApiError>(match key {
+                    Some(key) => server_api::PasskeyAdditionResultResponse::Saved {
+                        user: user_response(user),
+                        key,
+                    },
+                    None => server_api::PasskeyAdditionResultResponse::Unknown {},
+                })
+            })
+            .await
+            .map_err(ApiError::into_repository_api_error)
+    }
+
     async fn auth_passkey_addition_options(
         &self,
         context: server_api::ServerRequestContext,
@@ -8191,6 +8256,13 @@ impl server_api::ServerApi for ServerApiContractService {
             .db_executor()
             .run(move || {
                 let (user, authentication) = passkey_addition_authority(&api, &headers)?;
+                require_expected_passkey_owner(
+                    &user,
+                    &authentication,
+                    &request.expected_user_id,
+                    &request.expected_account_id,
+                    &request.expected_authentication_reference,
+                )?;
                 start_passkey_registration(
                     &api,
                     &headers,
@@ -30161,6 +30233,14 @@ async fn post_passkey_registration_options(
 fn passkey_addition_authority(
     api: &ServerAuthApi,
     headers: &HeaderMap,
+) -> ApiResult<(UserRecord, PasskeyAuthenticationBinding)> {
+    passkey_owner_authority(api, headers, true)
+}
+
+fn passkey_owner_authority(
+    api: &ServerAuthApi,
+    headers: &HeaderMap,
+    require_origin: bool,
 ) -> ApiResult<(UserRecord, PasskeyAuthenticationBinding)> {
     let auth = auth_public_config(&api.config);
     let actor = crate::auth::resolve_request_actor_sync(
@@ -30176,7 +30256,7 @@ fn passkey_addition_authority(
     })?;
     let binding = match actor.auth_method {
         ActorAuthMethod::BrowserSession => {
-            if request_origin(headers).as_deref() != Some(auth.origin.as_str()) {
+            if require_origin && request_origin(headers).as_deref() != Some(auth.origin.as_str()) {
                 return Err(Error::WorkspacePermissionDenied(
                     "cookie-authenticated passkey addition requires the configured Browser origin"
                         .into(),
@@ -30208,6 +30288,26 @@ fn passkey_addition_authority(
     Ok((user, binding))
 }
 
+fn require_expected_passkey_owner(
+    user: &UserRecord,
+    binding: &PasskeyAuthenticationBinding,
+    expected_user_id: &str,
+    expected_account_id: &str,
+    expected_authentication_reference: &str,
+) -> ApiResult<()> {
+    if user.user_id != expected_user_id
+        || user.account_id != expected_account_id
+        || binding.reference() != expected_authentication_reference
+    {
+        return Err(auth_error(
+            "passkey_authentication_changed",
+            "authentication changed; refresh account before starting another operation",
+        )
+        .into());
+    }
+    Ok(())
+}
+
 fn start_passkey_registration(
     api: &ServerAuthApi,
     headers: &HeaderMap,
@@ -30289,7 +30389,11 @@ fn start_passkey_registration(
 /// Credential commit precedes session issuance. If issuing the session or
 /// delivering the response fails, the credential can already exist: log in with
 /// that key rather than overwriting it or replaying the consumed completion.
-/// After an unknown commit outcome, try login first. Restart new-account
+/// Own additions save a receipt atomically with the credential: a currently
+/// authenticated same owner can inspect it using the original operation binding
+/// reference even if the response body was lost after Set-Cookie took effect.
+/// This read does not authorize a completion or prove current session health.
+/// For unknown new-account outcomes, try login first. Restart new-account
 /// enrollment with fresh options only for an unused handle with no persisted
 /// identity; legacy pre-created identities follow the migration policy on
 /// [`PasskeyRegistrationEnvelope`]. Neither recovery path requires DB edits.
@@ -30313,6 +30417,7 @@ fn complete_passkey_enrollment(
     request: PasskeyRegistrationCompleteRequest,
     completion: EnrollmentCompletion<'_>,
 ) -> ApiResult<(AuthUserResponse, server_api::SetCookieHeader)> {
+    let is_addition = matches!(&completion, EnrollmentCompletion::Addition(_));
     let authority = match completion {
         EnrollmentCompletion::Addition(headers) => Some(passkey_addition_authority(api, headers)?),
         _ => None,
@@ -30398,7 +30503,7 @@ fn complete_passkey_enrollment(
                 &error.to_string(),
             )
         })?;
-    api.store.register_verified_passkey(
+    api.store.register_verified_passkey_with_result(
         &envelope.target,
         &PasskeyCredentialRecord {
             credential_id: passkey_credential_id(&passkey)?,
@@ -30411,6 +30516,7 @@ fn complete_passkey_enrollment(
             created_at: crate::auth::now_rfc3339(),
             last_used_at: None,
         },
+        is_addition.then_some(request.challenge_id.as_str()),
     )?;
     issue_browser_session(api, user)
 }
@@ -30580,6 +30686,7 @@ fn complete_passkey_login(
         .into());
     }
     let webauthn = webauthn_for_challenge(&api.config, &challenge)?;
+    let normal_login = matches!(state, PasskeyLoginState::Discoverable(_));
     let auth_result = match state {
         PasskeyLoginState::Discoverable(state) => {
             // userHandle is unsigned routing data, never identity authority. The
@@ -30635,7 +30742,7 @@ fn complete_passkey_login(
         .map_err(|error| auth_error("webauthn_state_serialize_failed", &error.to_string()))?;
     api.store
         .upsert_passkey_credential(&PasskeyCredentialRecord {
-            credential_id,
+            credential_id: credential_id.clone(),
             user_id: user.user_id.clone(),
             public_key_cose,
             transports_json: stored.transports_json,
@@ -30643,6 +30750,10 @@ fn complete_passkey_login(
             created_at: stored.created_at,
             last_used_at: Some(crate::auth::now_rfc3339()),
         })?;
+    if normal_login {
+        api.store
+            .mark_passkey_normal_login_verified(&credential_id, &crate::auth::now_rfc3339())?;
+    }
     issue_browser_session(api, user)
 }
 
@@ -30668,6 +30779,9 @@ fn issue_browser_session(
     Ok((
         AuthUserResponse {
             user: user_response(user),
+            authentication_reference: crate::auth::authentication_reference(&token_hash(
+                &session_token,
+            )),
         },
         server_api::SetCookieHeader::new(cookie),
     ))
@@ -52401,6 +52515,7 @@ mod tests {
 
         include!("server_activation_tests.rs");
         include!("server_discoverable_tests.rs");
+        include!("server_passkey_results_tests.rs");
 
         const ORIGIN_URL: &str = "https://workspace.test";
         type Authenticator = ResidentAuthenticator;
@@ -52454,9 +52569,61 @@ mod tests {
                 origin: Option<&str>,
                 body: Value,
             ) -> (StatusCode, HeaderMap, Value) {
+                let mut body = body;
+                if path == "/api/auth/passkeys/addition/options"
+                    && body.get("expected_user_id").is_none()
+                {
+                    let expected = self.expected_owner(cookie, bearer).await;
+                    for (field, value) in expected.as_object().unwrap() {
+                        body[field] = value.clone();
+                    }
+                }
                 Self::post_to(self.app.clone(), path, cookie, bearer, origin, body).await
             }
 
+            async fn get_authenticated(
+                &self,
+                path: &str,
+                cookie: Option<&str>,
+                bearer: Option<&str>,
+            ) -> (StatusCode, Value) {
+                let mut request = Request::builder().uri(path);
+                if let Some(cookie) = cookie {
+                    request = request.header(axum::http::header::COOKIE, cookie);
+                }
+                if let Some(bearer) = bearer {
+                    request = request.header(
+                        axum::http::header::AUTHORIZATION,
+                        format!("Bearer {bearer}"),
+                    );
+                }
+                let response = self
+                    .app
+                    .clone()
+                    .oneshot(request.body(Body::empty()).unwrap())
+                    .await
+                    .unwrap();
+                assert_eq!(response.headers()[CACHE_CONTROL], "no-store");
+                let status = response.status();
+                let body = serde_json::from_slice(
+                    &to_bytes(response.into_body(), usize::MAX).await.unwrap(),
+                )
+                .unwrap();
+                (status, body)
+            }
+
+            async fn expected_owner(&self, cookie: Option<&str>, bearer: Option<&str>) -> Value {
+                let (status, whoami) = self
+                    .get_authenticated("/api/auth/whoami", cookie, bearer)
+                    .await;
+                assert_eq!(status, StatusCode::OK);
+                serde_json::json!({
+                    "expected_user_id": whoami["actor"]["user_id"].as_str().unwrap_or("absent"),
+                    "expected_account_id": whoami["actor"]["account_id"].as_str().unwrap_or("absent"),
+                    "expected_authentication_reference": whoami["authentication_reference"].as_str().unwrap_or("absent"),
+                })
+            }
+
             async fn post_to(
                 app: Router,
                 path: &str,
@@ -52612,6 +52779,14 @@ mod tests {
                     .next()
                     .unwrap()
                     .to_string();
+                let (status, whoami) = self
+                    .get_authenticated("/api/auth/whoami", Some(&cookie), None)
+                    .await;
+                assert_eq!(status, StatusCode::OK);
+                assert!(
+                    body["authentication_reference"] == whoami["authentication_reference"],
+                    "completion must identify its exact issued session"
+                );
                 (
                     cookie,
                     serde_json::from_value::<AuthUserResponse>(body)
@@ -52699,6 +52874,14 @@ mod tests {
                     .next()
                     .unwrap()
                     .to_string();
+                let (status, whoami) = self
+                    .get_authenticated("/api/auth/whoami", Some(&cookie), None)
+                    .await;
+                assert_eq!(status, StatusCode::OK);
+                assert!(
+                    body["authentication_reference"] == whoami["authentication_reference"],
+                    "login completion must identify its exact issued session"
+                );
                 (
                     cookie,
                     serde_json::from_value::<AuthUserResponse>(body)
@@ -53222,6 +53405,9 @@ mod tests {
                 .auth_passkey_addition_options(
                     context,
                     server_api::PasskeyAdditionOptionsRequest {
+                        expected_user_id: user.user_id.clone(),
+                        expected_account_id: user.account_id.clone(),
+                        expected_authentication_reference: "not-authority".into(),
                         browser_origin: Some(ORIGIN_URL.into()),
                     },
                 )
@@ -53236,6 +53422,9 @@ mod tests {
                 .auth_passkey_addition_options(
                     context,
                     server_api::PasskeyAdditionOptionsRequest {
+                        expected_user_id: user.user_id.clone(),
+                        expected_account_id: user.account_id.clone(),
+                        expected_authentication_reference: "not-authority".into(),
                         browser_origin: Some(ORIGIN_URL.into()),
                     },
                 )
@@ -54241,7 +54430,7 @@ mod tests {
                     .header(axum::http::header::COOKIE, &marker)
                     .header(ORIGIN, &auth.origin)
                     .header(CONTENT_TYPE, "application/json")
-                    .body(Body::from("{}"))
+                    .body(Body::from(r#"{"expected_user_id":"absent","expected_account_id":"absent","expected_authentication_reference":"absent"}"#))
                     .unwrap(),
             )
             .await
diff --git a/crates/workspace-server/src/server_passkey_results_tests.rs b/crates/workspace-server/src/server_passkey_results_tests.rs
new file mode 100644
index 000000000..9562e5af2
--- /dev/null
+++ b/crates/workspace-server/src/server_passkey_results_tests.rs
@@ -0,0 +1,399 @@
+// Integration boundary: generated HTTP admission -> real WebAuthn verifier ->
+// SQLite credential/receipt transaction -> real session issuance. Only the
+// authenticator is synthetic; failures are SQLite triggers, not success fakes.
+
+impl Fixture {
+    async fn addition_result(&self, cookie: &str, challenge_id: &str) -> (StatusCode, Value) {
+        let mut request = self.expected_owner(Some(cookie), None).await;
+        request["challenge_id"] = challenge_id.into();
+        let (status, _, body) = self
+            .post(
+                "/api/auth/passkeys/addition/result",
+                Some(cookie),
+                Some(ORIGIN_URL),
+                request,
+            )
+            .await;
+        (status, body)
+    }
+}
+
+#[tokio::test]
+async fn addition_receipt_is_atomic_and_recovers_credential_commit_not_session_success() {
+    for failure in [
+        "before_credential",
+        "receipt_insert",
+        "session_insert",
+        "lost_response",
+        "lost_body_accepted_cookie",
+    ] {
+        let f = Fixture::new().await;
+        let mut original = authenticator();
+        let (cookie, owner) = f.enroll("registration", None, "owner", &mut original).await;
+        let original_expectation = f.expected_owner(Some(&cookie), None).await;
+        let options = f.options("addition", Some(&cookie), "").await;
+        let challenge_id = options.challenge_id.clone();
+        let mut added = authenticator();
+        let request = Fixture::credential(options, &mut added);
+        let (status, result) = f.addition_result(&cookie, &challenge_id).await;
+        assert_eq!(status, StatusCode::OK);
+        assert_eq!(result["status"], "unknown");
+        let table = match failure {
+            "before_credential" => Some("passkey_credentials"),
+            "receipt_insert" => Some("passkey_addition_receipts"),
+            "session_insert" => Some("browser_sessions"),
+            _ => None,
+        };
+        if let Some(table) = table {
+            f.api.config_store.with_conn(|conn| {
+                conn.execute_batch(&format!("CREATE TRIGGER inject_passkey_failure BEFORE INSERT ON {table} BEGIN SELECT RAISE(ABORT, 'synthetic failure'); END;"))?;
+                Ok(())
+            }).unwrap();
+        }
+        // Discard the completion body; one variant still accepts Set-Cookie.
+        let (status, headers, _) = f
+            .post(
+                "/api/auth/passkeys/addition/complete",
+                Some(&cookie),
+                Some(ORIGIN_URL),
+                request.clone(),
+            )
+            .await;
+        assert_eq!(
+            status,
+            if matches!(failure, "lost_response" | "lost_body_accepted_cookie") {
+                StatusCode::OK
+            } else {
+                StatusCode::INTERNAL_SERVER_ERROR
+            }
+        );
+        if !matches!(failure, "lost_response" | "lost_body_accepted_cookie") {
+            assert!(!headers.contains_key(axum::http::header::SET_COOKIE));
+        }
+        let saved = matches!(
+            failure,
+            "session_insert" | "lost_response" | "lost_body_accepted_cookie"
+        );
+        if failure == "lost_body_accepted_cookie" {
+            let accepted_cookie = headers[axum::http::header::SET_COOKIE]
+                .to_str()
+                .unwrap()
+                .split(';')
+                .next()
+                .unwrap();
+            let current = f.expected_owner(Some(accepted_cookie), None).await;
+            assert!(
+                current["expected_authentication_reference"]
+                    != original_expectation["expected_authentication_reference"],
+                "addition issued a distinct session"
+            );
+            let mut recovery = original_expectation.clone();
+            recovery["challenge_id"] = challenge_id.clone().into();
+            let (status, _, result) = f
+                .post(
+                    "/api/auth/passkeys/addition/result",
+                    Some(accepted_cookie),
+                    Some(ORIGIN_URL),
+                    recovery,
+                )
+                .await;
+            assert_eq!(status, StatusCode::OK);
+            assert_eq!(result["status"], "saved");
+            assert_eq!(result["user"]["user_id"], owner.user_id);
+        }
+        let (status, result) = f.addition_result(&cookie, &challenge_id).await;
+        assert_eq!(status, StatusCode::OK);
+        assert_eq!(result["status"], if saved { "saved" } else { "unknown" });
+        assert_eq!(f.credentials(&owner).len(), if saved { 2 } else { 1 });
+        let receipt_count = f
+            .api
+            .config_store
+            .with_conn(|conn| {
+                Ok(conn.query_row(
+                    "SELECT COUNT(*) FROM passkey_addition_receipts",
+                    [],
+                    |row| row.get::<_, u64>(0),
+                )?)
+            })
+            .unwrap();
+        assert_eq!(receipt_count, u64::from(saved));
+        if saved {
+            assert_eq!(result["user"]["user_id"], owner.user_id);
+            let (_, listed) = f
+                .get_authenticated("/api/auth/passkeys", Some(&cookie), None)
+                .await;
+            let reference = result["key"]["key_reference"].as_str().unwrap();
+            assert!(
+                listed["keys"]
+                    .as_array()
+                    .unwrap()
+                    .iter()
+                    .any(|key| key["key_reference"] == reference)
+            );
+            assert!(result["key"]["normal_login_verified_at"].is_null());
+        }
+        if table.is_some() {
+            f.api
+                .config_store
+                .with_conn(|conn| {
+                    conn.execute_batch("DROP TRIGGER inject_passkey_failure")?;
+                    Ok(())
+                })
+                .unwrap();
+        }
+        // Consumed completion is not retry authority, even after a transaction failure.
+        let (status, headers, _) = f
+            .post(
+                "/api/auth/passkeys/addition/complete",
+                Some(&cookie),
+                Some(ORIGIN_URL),
+                request,
+            )
+            .await;
+        assert_eq!(status, StatusCode::BAD_REQUEST);
+        assert!(!headers.contains_key(axum::http::header::SET_COOKIE));
+        assert_eq!(f.credentials(&owner).len(), if saved { 2 } else { 1 });
+        if saved {
+            assert_eq!(f.discoverable_login(&mut added).await, owner);
+        }
+    }
+}
+
+#[tokio::test]
+async fn stale_displayed_owner_or_session_cannot_start_addition_or_read_another_binding_result() {
+    let f = Fixture::new().await;
+    let mut alice_key = authenticator();
+    let (alice_cookie, alice) = f
+        .enroll("registration", None, "alice", &mut alice_key)
+        .await;
+    let (bob_cookie, _) = f
+        .enroll("registration", None, "bob", &mut authenticator())
+        .await;
+    let expected = f.expected_owner(Some(&alice_cookie), None).await;
+    let (replacement_cookie, _) = f.login_session("alice", &mut alice_key).await;
+    let count_challenges = || {
+        f.api
+            .config_store
+            .with_conn(|conn| {
+                Ok(
+                    conn.query_row("SELECT COUNT(*) FROM auth_challenges", [], |row| {
+                        row.get::<_, u64>(0)
+                    })?,
+                )
+            })
+            .unwrap()
+    };
+    let before = count_challenges();
+    for cookie in [&bob_cookie, &replacement_cookie] {
+        let (status, _, _) = f
+            .post(
+                "/api/auth/passkeys/addition/options",
+                Some(cookie),
+                Some(ORIGIN_URL),
+                expected.clone(),
+            )
+            .await;
+        assert_eq!(status, StatusCode::BAD_REQUEST);
+        assert_eq!(
+            count_challenges(),
+            before,
+            "stale options must not persist a ceremony"
+        );
+    }
+    let options = f.options("addition", Some(&alice_cookie), "").await;
+    let challenge_id = options.challenge_id.clone();
+    let request = Fixture::credential(options, &mut authenticator());
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/addition/complete",
+            Some(&alice_cookie),
+            Some(ORIGIN_URL),
+            request
+        )
+        .await
+        .0,
+        StatusCode::OK
+    );
+    assert_eq!(
+        f.addition_result(&alice_cookie, &challenge_id).await.1["status"],
+        "saved"
+    );
+    // Current owner authorization is separate from original operation binding.
+    let mut recovery = expected.clone();
+    recovery["challenge_id"] = challenge_id.clone().into();
+    let (status, _, result) = f
+        .post(
+            "/api/auth/passkeys/addition/result",
+            Some(&replacement_cookie),
+            Some(ORIGIN_URL),
+            recovery.clone(),
+        )
+        .await;
+    assert_eq!(status, StatusCode::OK);
+    assert_eq!(result["status"], "saved");
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/addition/result",
+            Some(&bob_cookie),
+            Some(ORIGIN_URL),
+            recovery.clone()
+        )
+        .await
+        .0,
+        StatusCode::BAD_REQUEST
+    );
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/addition/result",
+            None,
+            Some(ORIGIN_URL),
+            recovery.clone()
+        )
+        .await
+        .0,
+        StatusCode::FORBIDDEN
+    );
+    recovery["expected_authentication_reference"] = "changed-original-reference".into();
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/addition/result",
+            Some(&replacement_cookie),
+            Some(ORIGIN_URL),
+            recovery
+        )
+        .await
+        .0,
+        StatusCode::BAD_REQUEST
+    );
+    // Bob's own expected fields cannot discover Alice's operation either.
+    let (status, result) = f.addition_result(&bob_cookie, &challenge_id).await;
+    assert_eq!(status, StatusCode::OK);
+    assert_eq!(result, serde_json::json!({"status":"unknown"}));
+    assert_eq!(f.credentials(&alice).len(), 2);
+    assert_eq!(
+        f.post(
+            "/api/auth/logout",
+            Some(&alice_cookie),
+            Some(ORIGIN_URL),
+            serde_json::json!({})
+        )
+        .await
+        .0,
+        StatusCode::OK
+    );
+    let mut request = expected;
+    request["challenge_id"] = challenge_id.into();
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/addition/result",
+            Some(&alice_cookie),
+            Some(ORIGIN_URL),
+            request
+        )
+        .await
+        .0,
+        StatusCode::FORBIDDEN
+    );
+}
+
+#[tokio::test]
+async fn own_key_list_is_safe_and_only_verified_normal_login_marks_confirmation() {
+    let f = Fixture::new().await;
+    let mut key = authenticator();
+    let (cookie, owner) = f.enroll("registration", None, "owner", &mut key).await;
+    let (other_cookie, _) = f
+        .enroll("registration", None, "other", &mut authenticator())
+        .await;
+    assert_eq!(
+        f.get_authenticated("/api/auth/passkeys", None, None)
+            .await
+            .0,
+        StatusCode::FORBIDDEN
+    );
+    let (status, list) = f
+        .get_authenticated("/api/auth/passkeys", Some(&cookie), None)
+        .await;
+    assert_eq!(status, StatusCode::OK);
+    assert_eq!(list["user"]["user_id"], owner.user_id);
+    assert_eq!(list["keys"].as_array().unwrap().len(), 1);
+    let summary = &list["keys"][0];
+    assert!(summary["normal_login_verified_at"].is_null());
+    assert!(summary["last_used_at"].is_null());
+    let reference = summary["key_reference"].as_str().unwrap();
+    assert_eq!(reference.len(), 32);
+    assert_ne!(reference, f.credentials(&owner)[0].credential_id);
+    assert_eq!(
+        summary
+            .as_object()
+            .unwrap()
+            .keys()
+            .map(String::as_str)
+            .collect::<std::collections::BTreeSet<_>>(),
+        [
+            "key_reference",
+            "created_at",
+            "last_used_at",
+            "normal_login_verified_at"
+        ]
+        .into_iter()
+        .collect()
+    );
+    let (_, other) = f
+        .get_authenticated("/api/auth/passkeys", Some(&other_cookie), None)
+        .await;
+    assert_ne!(other["keys"][0]["key_reference"], reference);
+    assert_eq!(f.login("owner", &mut key).await, owner);
+    let (_, legacy) = f
+        .get_authenticated("/api/auth/passkeys", Some(&cookie), None)
+        .await;
+    assert!(legacy["keys"][0]["last_used_at"].is_string());
+    assert!(legacy["keys"][0]["normal_login_verified_at"].is_null());
+    // Rejected normal assertion does not produce confirmation metadata.
+    let mut invalid = f.discoverable_request(&mut key).await;
+    invalid.credential.response.signature = vec![0u8; 64].into();
+    assert_eq!(
+        f.post(
+            "/api/auth/passkeys/login/complete",
+            None,
+            Some(ORIGIN_URL),
+            serde_json::to_value(invalid).unwrap()
+        )
+        .await
+        .0,
+        StatusCode::BAD_REQUEST
+    );
+    assert!(
+        f.api.store.list_passkey_summaries(&owner.user_id).unwrap()[0]
+            .normal_login_verified_at
+            .is_none()
+    );
+    assert_eq!(f.discoverable_login(&mut key).await, owner);
+    let (_, confirmed) = f
+        .get_authenticated("/api/auth/passkeys", Some(&cookie), None)
+        .await;
+    assert_eq!(confirmed["keys"][0]["key_reference"], reference);
+    assert!(confirmed["keys"][0]["normal_login_verified_at"].is_string());
+}
+
+#[tokio::test]
+async fn unknown_transport_metadata_does_not_discard_verified_registration() {
+    let f = Fixture::new().await;
+    let options = f.options("registration", None, "future-transport").await;
+    let mut key = authenticator();
+    let mut request = Fixture::credential(options, &mut key);
+    request["credential"]["response"]["transports"] =
+        serde_json::json!(["internal", "future-transport", "test"]);
+    let (status, _, body) = f
+        .post(
+            "/api/auth/passkeys/registration/complete",
+            None,
+            Some(ORIGIN_URL),
+            request,
+        )
+        .await;
+    assert_eq!(status, StatusCode::OK);
+    let user = serde_json::from_value::<AuthUserResponse>(body)
+        .unwrap()
+        .user;
+    assert_eq!(f.discoverable_login(&mut key).await, user);
+}
diff --git a/crates/workspace-server/src/store.rs b/crates/workspace-server/src/store.rs
index f12c54334..adc833d00 100644
--- a/crates/workspace-server/src/store.rs
+++ b/crates/workspace-server/src/store.rs
@@ -119,7 +119,7 @@ pub use ticket::{
 };
 
 const OLDEST_SCHEMA_VERSION: i64 = 50;
-const LATEST_SCHEMA_VERSION: i64 = 102;
+const LATEST_SCHEMA_VERSION: i64 = 103;
 const WORKSPACE_DRIVE_GRANTS_MIGRATION_NAME: &str = "durable Workspace Drive grants";
 const WORKSPACE_CONFIG_GRANTS_MIGRATION_NAME: &str = "Workspace config grants and logical Workdirs";
 const SCHEMA_BASELINE_NAME: &str = "workspace schema baseline";
@@ -437,6 +437,11 @@ const MIGRATIONS: &[Migration] = &[
         name: "Durable failed Subject creation recovery",
         apply: migrate_subject_create_recovery_v101_to_v102,
     },
+    Migration {
+        version: 103,
+        name: "Passkey metadata and atomic addition results",
+        apply: migrate_passkey_results_v102_to_v103,
+    },
 ];
 
 #[derive(Clone, Copy)]
@@ -749,6 +754,15 @@ pub enum PasskeyAuthenticationBinding {
     ApiToken(String),
 }
 
+impl PasskeyAuthenticationBinding {
+    pub(crate) fn reference(&self) -> String {
+        let hash = match self {
+            Self::BrowserSession(hash) | Self::ApiToken(hash) => hash,
+        };
+        crate::auth::authentication_reference(hash)
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub struct PasskeyCredentialRecord {
     pub credential_id: String,
@@ -1713,6 +1727,27 @@ pub trait ControlPlaneStore: Send + Sync + WorkspaceDeletionStore {
         &self,
         target: &PasskeyRegistrationTarget,
         credential: &PasskeyCredentialRecord,
+    ) -> Result<()> {
+        self.register_verified_passkey_with_result(target, credential, None)
+    }
+    /// Receipt and credential commit together; no receipt claims session issuance.
+    fn register_verified_passkey_with_result(
+        &self,
+        target: &PasskeyRegistrationTarget,
+        credential: &PasskeyCredentialRecord,
+        addition_challenge_id: Option<&str>,
+    ) -> Result<()>;
+    fn list_passkey_summaries(&self, user_id: &str) -> Result<Vec<server_api::PasskeySummary>>;
+    fn read_passkey_addition_result(
+        &self,
+        user_id: &str,
+        original_authentication_reference: &str,
+        challenge_id: &str,
+    ) -> Result<Option<server_api::PasskeySummary>>;
+    fn mark_passkey_normal_login_verified(
+        &self,
+        credential_id: &str,
+        verified_at: &str,
     ) -> Result<()>;
     fn upsert_passkey_credential(&self, record: &PasskeyCredentialRecord) -> Result<()>;
     fn get_passkey_credential(
@@ -6972,10 +7007,11 @@ impl ControlPlaneStore for SqliteWorkspaceStore {
         })
     }
 
-    fn register_verified_passkey(
+    fn register_verified_passkey_with_result(
         &self,
         target: &PasskeyRegistrationTarget,
         credential: &PasskeyCredentialRecord,
+        addition_challenge_id: Option<&str>,
     ) -> Result<()> {
         self.with_immediate_transaction(|tx| {
             let user = match target {
@@ -7042,6 +7078,15 @@ impl ControlPlaneStore for SqliteWorkspaceStore {
                 "INSERT INTO passkey_credentials (credential_id, user_id, public_key_cose, transports_json, sign_count, created_at, last_used_at) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)",
                 params![credential.credential_id, credential.user_id, credential.public_key_cose, credential.transports_json, credential.sign_count, credential.created_at, credential.last_used_at],
             )?;
+            if let Some(challenge_id) = addition_challenge_id {
+                let PasskeyRegistrationTarget::Addition { user, authentication } = target else {
+                    return Err(crate::auth::auth_error("passkey_target_mismatch", "receipt requires an addition"));
+                };
+                tx.execute(
+                    "INSERT INTO passkey_addition_receipts(challenge_id, credential_id, user_id, authentication_reference) VALUES (?1, ?2, ?3, ?4)",
+                    params![challenge_id, credential.credential_id, user.user_id, authentication.reference()],
+                )?;
+            }
             if let PasskeyRegistrationTarget::Activation { user, issuance_id } = target {
                 if tx.execute("DELETE FROM user_activations WHERE user_id=?1 AND issuance_id=?2", params![user.user_id, issuance_id])? != 1 {
                     return Err(crate::auth::auth_error("activation_code_invalid", "activation issuance no longer exists"));
@@ -7051,6 +7096,57 @@ impl ControlPlaneStore for SqliteWorkspaceStore {
         })
     }
 
+    fn list_passkey_summaries(&self, user_id: &str) -> Result<Vec<server_api::PasskeySummary>> {
+        self.with_conn(|conn| {
+            let mut stmt = conn.prepare(
+                "SELECT m.key_reference, c.created_at, c.last_used_at, m.normal_login_verified_at
+                 FROM passkey_credentials c JOIN passkey_metadata m USING(credential_id)
+                 WHERE c.user_id = ?1 ORDER BY c.created_at, m.key_reference",
+            )?;
+            let rows = stmt.query_map([user_id], read_passkey_summary)?;
+            rows.collect::<std::result::Result<Vec<_>, _>>()
+                .map_err(Error::from)
+        })
+    }
+
+    fn read_passkey_addition_result(
+        &self,
+        user_id: &str,
+        original_authentication_reference: &str,
+        challenge_id: &str,
+    ) -> Result<Option<server_api::PasskeySummary>> {
+        self.with_conn(|conn| {
+            // Current authenticated ownership authorizes reading. The original
+            // binding reference identifies the saved operation, not the current
+            // session: Set-Cookie may have arrived even if its body was lost.
+            let result = conn.query_row(
+                "SELECT m.key_reference, c.created_at, c.last_used_at, m.normal_login_verified_at, r.authentication_reference
+                 FROM passkey_addition_receipts r
+                 JOIN passkey_credentials c USING(credential_id)
+                 JOIN passkey_metadata m USING(credential_id)
+                 WHERE r.challenge_id = ?1 AND r.user_id = ?2 AND c.user_id = ?2",
+                params![challenge_id, user_id],
+                |row| Ok((read_passkey_summary(row)?, row.get::<_, String>(4)?)),
+            ).optional()?;
+            match result {
+                Some((key, reference)) if reference == original_authentication_reference => Ok(Some(key)),
+                Some(_) => Err(crate::auth::auth_error("passkey_result_binding_mismatch", "original operation authentication reference does not match")),
+                None => Ok(None),
+            }
+        })
+    }
+
+    fn mark_passkey_normal_login_verified(
+        &self,
+        credential_id: &str,
+        verified_at: &str,
+    ) -> Result<()> {
+        self.with_conn(|conn| {
+            conn.execute("UPDATE passkey_metadata SET normal_login_verified_at = ?2 WHERE credential_id = ?1", params![credential_id, verified_at])?;
+            Ok(())
+        })
+    }
+
     fn upsert_passkey_credential(&self, record: &PasskeyCredentialRecord) -> Result<()> {
         self.with_immediate_transaction(|conn| {
             activation::require_active(conn, &record.user_id)?;
@@ -11911,6 +12007,15 @@ fn passkey_select_sql(where_clause: &str) -> String {
     )
 }
 
+fn read_passkey_summary(row: &rusqlite::Row<'_>) -> rusqlite::Result<server_api::PasskeySummary> {
+    Ok(server_api::PasskeySummary {
+        key_reference: row.get(0)?,
+        created_at: row.get(1)?,
+        last_used_at: row.get(2)?,
+        normal_login_verified_at: row.get(3)?,
+    })
+}
+
 fn read_passkey_credential_record(
     row: &rusqlite::Row<'_>,
 ) -> rusqlite::Result<PasskeyCredentialRecord> {
@@ -15164,6 +15269,22 @@ fn migrate_result_reports_v97_to_v98(conn: &Connection) -> Result<()> {
     Ok(())
 }
 
+fn migrate_passkey_results_v102_to_v103(conn: &Connection) -> Result<()> {
+    if current_schema_version(conn)? != 102 {
+        return Err(Error::Store(
+            "Passkey results migration requires schema 102".into(),
+        ));
+    }
+    let tx = conn.unchecked_transaction()?;
+    tx.execute_batch(include_str!("passkey_results_schema.sql"))?;
+    tx.execute(
+        "INSERT INTO __yoi_schema_migrations(version,name) VALUES(103,?1)",
+        ["Passkey metadata and atomic addition results"],
+    )?;
+    tx.commit()?;
+    Ok(())
+}
+
 fn migrate_subject_create_recovery_v101_to_v102(conn: &Connection) -> Result<()> {
     if current_schema_version(conn)? != 101 {
         return Err(Error::Store(
@@ -15255,6 +15376,7 @@ fn create_latest_workspace_schema(conn: &Connection) -> Result<()> {
 fn create_workspace_schema_structure(conn: &Connection) -> Result<()> {
     create_workspace_schema_structure_from_sql(conn, include_str!("latest_schema.sql"), true)?;
     conn.execute_batch(include_str!("activation_schema.sql"))?;
+    conn.execute_batch(include_str!("passkey_results_schema.sql"))?;
     Ok(())
 }
 
@@ -18948,6 +19070,7 @@ CREATE UNIQUE INDEX ticket_current_worker_role_idx
                 WorkspaceSchemaMigrationStep {version:100, name:"Provisional users and scoped passkey activation".into()},
                 WorkspaceSchemaMigrationStep {version:101, name:"Durable explicit Subject body release".into()},
                 WorkspaceSchemaMigrationStep {version:102, name:"Durable failed Subject creation recovery".into()},
+                WorkspaceSchemaMigrationStep {version:103, name:"Passkey metadata and atomic addition results".into()},
             ]
         );
 
@@ -19060,6 +19183,7 @@ CREATE UNIQUE INDEX ticket_current_worker_role_idx
 (100, "Provisional users and scoped passkey activation".to_string()),
 (101, "Durable explicit Subject body release".to_string()),
 (102, "Durable failed Subject creation recovery".to_string()),
+(103, "Passkey metadata and atomic addition results".to_string()),
                     ]
                 );
                 assert!(!table_exists(conn, "trusted_runtime_records")?);
@@ -21288,6 +21412,83 @@ CREATE UNIQUE INDEX ticket_current_worker_role_idx
         );
     }
 
+    #[test]
+    fn passkey_results_migration_preserves_old_keys_unknown_confirmation_and_rolls_back() {
+        for baseline in [50, 102] {
+            let dir = tempfile::tempdir().unwrap();
+            let database = dir.path().join("server.db");
+            if baseline == 50 {
+                prepare_schema_v50(&database, None);
+            } else {
+                prepare_retained_schema(&database, baseline);
+            }
+            let conn = Connection::open(&database).unwrap();
+            configure_sqlite(&conn).unwrap();
+            conn.execute_batch(r#"INSERT INTO accounts(account_id, kind, handle, display_name, created_at, updated_at)
+                VALUES('account-old', 'user', 'old', 'Old', 'created', 'updated');
+                INSERT INTO users(user_id, account_id, handle, display_name, created_at, updated_at)
+                VALUES('user-old', 'account-old', 'old', 'Old', 'created', 'updated');
+                INSERT INTO passkey_credentials(credential_id, user_id, public_key_cose, transports_json, sign_count, created_at, last_used_at)
+                VALUES('old-key', 'user-old', 'unchanged-key-material', '["internal"]', 7, 'created-key', 'used-key');"#)
+                .unwrap();
+            if baseline == 102 {
+                conn.execute_batch("CREATE TRIGGER interrupt_passkey_migration BEFORE INSERT ON __yoi_schema_migrations
+                    WHEN NEW.version=103 BEGIN SELECT RAISE(ABORT, 'synthetic migration interruption'); END;").unwrap();
+                assert!(migrate_passkey_results_v102_to_v103(&conn).is_err());
+                assert_eq!(current_schema_version(&conn).unwrap(), 102);
+                assert!(!table_exists(&conn, "passkey_metadata").unwrap());
+                assert!(!table_exists(&conn, "passkey_addition_receipts").unwrap());
+                conn.execute_batch("DROP TRIGGER interrupt_passkey_migration")
+                    .unwrap();
+            }
+            drop(conn);
+            let preflight = SqliteWorkspaceStore::migration_plan(&database).unwrap();
+            assert!(preflight.migration_required());
+            // Preflight must not install metadata in the source database.
+            let conn = Connection::open(&database).unwrap();
+            assert!(!table_exists(&conn, "passkey_metadata").unwrap());
+            drop(conn);
+            let migrated = SqliteWorkspaceStore::open_for_test(&database).unwrap();
+            let record = migrated.get_passkey_credential("old-key").unwrap().unwrap();
+            assert_eq!(record.public_key_cose, "unchanged-key-material");
+            assert_eq!(record.sign_count, 7);
+            assert_eq!(record.last_used_at.as_deref(), Some("used-key"));
+            let summary = migrated
+                .list_passkey_summaries("user-old")
+                .unwrap()
+                .remove(0);
+            assert_eq!(summary.created_at, "created-key");
+            assert_eq!(summary.last_used_at.as_deref(), Some("used-key"));
+            assert!(summary.normal_login_verified_at.is_none());
+            assert_eq!(summary.key_reference.len(), 32);
+            let fresh = SqliteWorkspaceStore::in_memory_for_test().unwrap();
+            let schema = |conn: &Connection| -> Result<Vec<(String, String)>> {
+                let mut stmt = conn.prepare("SELECT name, sql FROM sqlite_schema WHERE name IN
+                    ('passkey_metadata', 'passkey_metadata_insert', 'passkey_addition_receipts') ORDER BY name")?;
+                Ok(stmt
+                    .query_map([], |row| Ok((row.get(0)?, row.get(1)?)))?
+                    .collect::<std::result::Result<Vec<_>, _>>()?)
+            };
+            assert_eq!(
+                migrated.with_conn(schema).unwrap(),
+                fresh.with_conn(schema).unwrap()
+            );
+            migrated.with_conn(|conn| {
+                assert!(conn.execute("INSERT INTO passkey_metadata(credential_id,key_reference) VALUES('missing-key','ref')", []).is_err());
+                assert!(conn.execute("INSERT INTO passkey_addition_receipts(challenge_id,credential_id,user_id,authentication_reference)
+                    VALUES('operation','missing-key','user-old','{}')", []).is_err());
+                assert_eq!(conn.query_row("SELECT count(*) FROM pragma_foreign_key_check", [], |row| row.get::<_, u64>(0))?, 0);
+                Ok(())
+            }).unwrap();
+            drop(migrated);
+            let reopened = SqliteWorkspaceStore::open_for_test(&database).unwrap();
+            assert_eq!(
+                reopened.list_passkey_summaries("user-old").unwrap(),
+                vec![summary]
+            );
+        }
+    }
+
     #[test]
     fn subject_create_recovery_migration_is_atomic_and_matches_fresh_schema() {
         let dir = tempfile::tempdir().unwrap();
@@ -21327,7 +21528,7 @@ CREATE UNIQUE INDEX ticket_current_worker_role_idx
         drop(conn);
         let reopened = SqliteWorkspaceStore::open_for_test(&database).unwrap();
         reopened
-            .with_conn(|c| verify_schema_history(c, 102))
+            .with_conn(|c| verify_schema_history(c, LATEST_SCHEMA_VERSION))
             .unwrap();
     }
 
@@ -22266,7 +22467,8 @@ CREATE UNIQUE INDEX ticket_current_worker_role_idx
                          (99, "Explicit hosting administrators and self-registration policy".into()),
                          (100, "Provisional users and scoped passkey activation".into()),
                          (101, "Durable explicit Subject body release".into()),
-                         (102, "Durable failed Subject creation recovery".into())]);
+                         (102, "Durable failed Subject creation recovery".into()),
+                         (103, "Passkey metadata and atomic addition results".into())]);
                 for (table, rows) in unchanged.iter().zip(before.iter()) {
                     assert_eq!(&stored_fixture_rows(conn, table), rows, "preserve {table}");
                 }
diff --git a/openapi/server-api.json b/openapi/server-api.json
index 720c13a72..3965becc3 100644
--- a/openapi/server-api.json
+++ b/openapi/server-api.json
@@ -298,12 +298,17 @@
       "AuthUserResponse": {
         "additionalProperties": false,
         "properties": {
+          "authentication_reference": {
+            "description": "Comparison evidence for the exact newly issued session, not a credential.",
+            "type": "string"
+          },
           "user": {
             "$ref": "#/components/schemas/AuthenticatedUser"
           }
         },
         "required": [
-          "user"
+          "user",
+          "authentication_reference"
         ],
         "type": "object"
       },
@@ -6709,15 +6714,112 @@
       },
       "PasskeyAdditionOptionsRequest": {
         "additionalProperties": false,
-        "description": "Adds a credential to the current authenticated actor; target identity is never public input.",
+        "description": "Adds to the current actor. Expected identity/binding fields only fence stale UI;\nthey never select an owner or authorize an addition.",
         "properties": {
           "browser_origin": {
             "type": [
               "string",
               "null"
             ]
+          },
+          "expected_account_id": {
+            "type": "string"
+          },
+          "expected_authentication_reference": {
+            "type": "string"
+          },
+          "expected_user_id": {
+            "type": "string"
           }
         },
+        "required": [
+          "expected_user_id",
+          "expected_account_id",
+          "expected_authentication_reference"
+        ],
+        "type": "object"
+      },
+      "PasskeyAdditionResultRequest": {
+        "additionalProperties": false,
+        "properties": {
+          "challenge_id": {
+            "type": "string"
+          },
+          "expected_account_id": {
+            "type": "string"
+          },
+          "expected_authentication_reference": {
+            "description": "Original options authentication reference; the current same-owner session may differ.",
+            "type": "string"
+          },
+          "expected_user_id": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "challenge_id",
+          "expected_user_id",
+          "expected_account_id",
+          "expected_authentication_reference"
+        ],
+        "type": "object"
+      },
+      "PasskeyAdditionResultResponse": {
+        "description": "Unknown is not proof that registration failed: completion may still be in flight.\nSaved proves the credential commit, not session issuance or current session health.",
+        "oneOf": [
+          {
+            "additionalProperties": false,
+            "properties": {
+              "status": {
+                "const": "unknown",
+                "type": "string"
+              }
+            },
+            "required": [
+              "status"
+            ],
+            "type": "object"
+          },
+          {
+            "additionalProperties": false,
+            "properties": {
+              "key": {
+                "$ref": "#/components/schemas/PasskeySummary"
+              },
+              "status": {
+                "const": "saved",
+                "type": "string"
+              },
+              "user": {
+                "$ref": "#/components/schemas/AuthenticatedUser"
+              }
+            },
+            "required": [
+              "status",
+              "user",
+              "key"
+            ],
+            "type": "object"
+          }
+        ]
+      },
+      "PasskeyListResponse": {
+        "additionalProperties": false,
+        "properties": {
+          "keys": {
+            "items": {
+              "$ref": "#/components/schemas/PasskeySummary"
+            },
+            "type": "array"
+          },
+          "user": {
+            "$ref": "#/components/schemas/AuthenticatedUser"
+          }
+        },
+        "required": [
+          "user",
+          "keys"
+        ],
         "type": "object"
       },
       "PasskeyLoginCompleteRequest": {
@@ -6820,6 +6922,35 @@
         ],
         "type": "object"
       },
+      "PasskeySummary": {
+        "additionalProperties": false,
+        "description": "Safe account metadata. Neither the WebAuthn credential ID nor key material is exposed.\nNormal-login verification is observed verifier success, not inferred discoverability.",
+        "properties": {
+          "created_at": {
+            "type": "string"
+          },
+          "key_reference": {
+            "type": "string"
+          },
+          "last_used_at": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "normal_login_verified_at": {
+            "type": [
+              "string",
+              "null"
+            ]
+          }
+        },
+        "required": [
+          "key_reference",
+          "created_at"
+        ],
+        "type": "object"
+      },
       "PasteArtifactAvailability": {
         "enum": [
           "available",
@@ -15143,6 +15274,13 @@
               }
             ]
           },
+          "authentication_reference": {
+            "description": "Non-secret comparison evidence, never an authentication credential.",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
           "session": {
             "$ref": "#/components/schemas/BrowserSessionState"
           }
@@ -18155,7 +18293,7 @@
   "info": {
     "title": "Yoi Server API",
     "version": "0.1.0",
-    "x-yoi-source-digest": "sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7"
+    "x-yoi-source-digest": "sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23"
   },
   "openapi": "3.1.0",
   "paths": {
@@ -18589,6 +18727,61 @@
         }
       }
     },
+    "/api/auth/passkeys": {
+      "get": {
+        "operationId": "auth_passkey_list",
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/PasskeyListResponse"
+                }
+              }
+            },
+            "description": "Successful response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "403": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "500": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          }
+        },
+        "security": [
+          {
+            "bearerAuth": []
+          },
+          {
+            "browserSession": []
+          }
+        ]
+      }
+    },
     "/api/auth/passkeys/addition/complete": {
       "post": {
         "operationId": "auth_passkey_addition_complete",
@@ -18736,6 +18929,71 @@
         ]
       }
     },
+    "/api/auth/passkeys/addition/result": {
+      "post": {
+        "operationId": "auth_passkey_addition_result",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/PasskeyAdditionResultRequest"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/PasskeyAdditionResultResponse"
+                }
+              }
+            },
+            "description": "Successful response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "403": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "500": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          }
+        },
+        "security": [
+          {
+            "bearerAuth": []
+          },
+          {
+            "browserSession": []
+          }
+        ]
+      }
+    },
     "/api/auth/passkeys/login/complete": {
       "post": {
         "operationId": "auth_passkey_login_complete",
diff --git a/tests/e2e/README.md b/tests/e2e/README.md
index f2a9414ae..24bbc5823 100644
--- a/tests/e2e/README.md
+++ b/tests/e2e/README.md
@@ -9,6 +9,7 @@
 - [`WorkerE2eEnvironment`]: Backend／Runtime用プロセスとfixtureの管理。
 - [`FixtureSource`]: 提供資産の全ファイルSHA-256記録、独立copy、原本不変の検証。
 - [`WorkerSessionSubscription`]: 公開Worker WebSocketの初期full Snapshot照合と停止確認。モデル呼出しは行わない。
+- `tests/auth_passkeys/native_migration.rs`・`browser/native_passkey_migration.ts`: 実Backend／本番shell／Chromium native CTAP2の旧鍵移行。fixture境界・未確認範囲・明示選択コマンドはmoduleに置く。通常suiteやsoftware authenticatorの成功で代替しない。
 
 ## 固定Workerの段階起動
 
diff --git a/tests/e2e/browser/auth_sessions.ts b/tests/e2e/browser/auth_sessions.ts
index 226ae9e76..4990cbbb0 100644
--- a/tests/e2e/browser/auth_sessions.ts
+++ b/tests/e2e/browser/auth_sessions.ts
@@ -4,7 +4,7 @@
 // 固定expiry/短命cookieを作る明示fixtureだけが発行境界を代替し、実分類はBackendへ委ねる。
 // navigator.credentialsのみRustのResidentAuthenticatorへ接続する（物理認証器ではない）。
 import { assert, assertEquals } from "@std/assert";
-import { extname, join, normalize } from "@std/path";
+import { serveProductionShell } from "./static_shell.ts";
 import { type Browser, type BrowserContext, chromium } from "playwright";
 
 const [backend, origin, build, handle] = Deno.args;
@@ -13,82 +13,43 @@ if (!backend || !origin || !build || !handle) {
     "Expected isolated Backend URL, browser origin, production build, handle",
   );
 }
-await Deno.stat(join(build, "index.html")); // 暗黙buildや別asset rootへのfallbackはしない。
-const mime: Record<string, string> = {
-  ".html": "text/html; charset=utf-8",
-  ".js": "text/javascript",
-  ".css": "text/css",
-  ".json": "application/json",
-  ".svg": "image/svg+xml",
-  ".png": "image/png",
-  ".woff2": "font/woff2",
-  ".ico": "image/x-icon",
-};
-const server = Deno.serve({
-  hostname: "127.0.0.1",
-  port: Number(new URL(origin).port),
-  onListen() {},
-}, async (request) => {
-  const url = new URL(request.url);
-  if (url.pathname === "/__e2e/expired-session" && request.method === "POST") {
-    if (request.headers.get("origin") !== origin) {
-      return new Response(null, { status: 403 });
+const server = await serveProductionShell(
+  backend,
+  origin,
+  build,
+  async (request) => {
+    const url = new URL(request.url);
+    if (
+      url.pathname === "/__e2e/expired-session" && request.method === "POST"
+    ) {
+      if (request.headers.get("origin") !== origin) {
+        return new Response(null, { status: 403 });
+      }
+      // Rustは環境専用DBの実登録userへ公開store APIで保存する。secretをbody/ログへ出さない。
+      const fixture = await bridge("expired-session", {}) as {
+        set_cookies: string[];
+      };
+      const headers = new Headers({ "cache-control": "no-store" });
+      for (const cookie of fixture.set_cookies) {
+        headers.append("set-cookie", cookie);
+      }
+      return new Response(null, { status: 204, headers });
     }
-    // Rustは環境専用DBの実登録userへ公開store APIで保存する。secretをbody/ログへ出さない。
-    const fixture = await bridge("expired-session", {}) as {
-      set_cookies: string[];
-    };
-    const headers = new Headers({ "cache-control": "no-store" });
-    for (const cookie of fixture.set_cookies) {
-      headers.append("set-cookie", cookie);
+    if (
+      url.pathname === "/__e2e/primary-cookie-present" &&
+      request.method === "GET"
+    ) {
+      // HTTPで受け取ったprimaryの有無だけを返す。値、marker、DB状態は公開しない。
+      const present = request.headers.get("cookie")?.split(";").some((pair) =>
+        pair.trim().split("=", 1)[0] === "yoi_workspace_session"
+      ) ?? false;
+      return Response.json(present, {
+        headers: { "cache-control": "no-store" },
+      });
     }
-    return new Response(null, { status: 204, headers });
-  }
-  if (
-    url.pathname === "/__e2e/primary-cookie-present" && request.method === "GET"
-  ) {
-    // HTTPで受け取ったprimaryの有無だけを返す。値、marker、DB状態は公開しない。
-    const present = request.headers.get("cookie")?.split(";").some((pair) =>
-      pair.trim().split("=", 1)[0] === "yoi_workspace_session"
-    ) ?? false;
-    return Response.json(present, { headers: { "cache-control": "no-store" } });
-  }
-  if (url.pathname.startsWith("/api/")) {
-    const headers = new Headers(request.headers);
-    headers.delete("host");
-    headers.delete("connection");
-    // OriginとCookieを保持し、Set-Cookieを含む実応答をそのまま返す。
-    return await fetch(new URL(url.pathname + url.search, backend), {
-      method: request.method,
-      headers,
-      body: ["GET", "HEAD"].includes(request.method)
-        ? undefined
-        : await request.arrayBuffer(),
-      redirect: "manual",
-    });
-  }
-  const relative = normalize(url.pathname.replace(/^\/+/, "") || "index.html");
-  if (relative.startsWith("..")) {
-    return new Response("not found", { status: 404 });
-  }
-  let file = join(build, relative);
-  try {
-    if ((await Deno.stat(file)).isDirectory) file = join(file, "index.html");
-    return new Response(await Deno.readFile(file), {
-      headers: {
-        "content-type": mime[extname(file)] ?? "application/octet-stream",
-      },
-    });
-  } catch (error) {
-    if (!(error instanceof Deno.errors.NotFound)) throw error;
-    if (url.pathname.startsWith("/_app/")) {
-      return new Response("not found", { status: 404 });
-    }
-    return new Response(await Deno.readFile(join(build, "index.html")), {
-      headers: { "content-type": mime[".html"] },
-    });
-  }
-});
+    return undefined;
+  },
+);
 
 // 逐次ceremony/fixtureだけを扱う短いNDJSON bridge。署名/cookieをartifactへ記録しない。
 const input = Deno.stdin.readable.pipeThrough(new TextDecoderStream())
@@ -313,7 +274,8 @@ try {
 
   // 14日実時間の前進ではない。固定expiry実store recordとMax-Age=2のHTTP cookieで、
   // 自然消失後のmarker→実whoami→製品loader/router→実署名loginの接続を検証する。
-  const expiredTarget = "/dashboard?view=workspaces&filter=a%2Fb&ratio=100%25#selected%25";
+  const expiredTarget =
+    "/dashboard?view=workspaces&filter=a%2Fb&ratio=100%25#selected%25";
   const catalogResponse = () =>
     page.waitForResponse((response) =>
       new URL(response.url()).pathname === "/api/workspaces" &&
@@ -360,6 +322,7 @@ try {
   assert(expiredCookieNames.includes(marker.name));
   assertEquals(await whoami(), {
     actor: null,
+    authentication_reference: null,
     session: { kind: "expired" },
   });
   privateRequests.length = 0;
@@ -383,7 +346,11 @@ try {
     [],
     "expired reload must gate the real private catalog loader",
   );
-  assertEquals(await whoami(), { actor: null, session: { kind: "expired" } });
+  assertEquals(await whoami(), {
+    actor: null,
+    authentication_reference: null,
+    session: { kind: "expired" },
+  });
   await page.reload();
   await at(expiredLogin);
   await page.getByRole("button", { name: "Log in with passkey", exact: true })
@@ -416,7 +383,11 @@ try {
   // authenticatedにもexpiredにもならない。これを14日経過の成功とは数えない。
   await context.clearCookies({ name: session.name });
   const partial = await whoami();
-  assertEquals(partial, { actor: null, session: { kind: "anonymous" } });
+  assertEquals(partial, {
+    actor: null,
+    authentication_reference: null,
+    session: { kind: "anonymous" },
+  });
   await page.reload();
   await at("/");
   await context.clearCookies();
diff --git a/tests/e2e/browser/native_passkey_migration.ts b/tests/e2e/browser/native_passkey_migration.ts
new file mode 100644
index 000000000..79c2d52b7
--- /dev/null
+++ b/tests/e2e/browser/native_passkey_migration.ts
@@ -0,0 +1,611 @@
+/// <reference lib="dom" />
+// 実Backend + 本番static shell + Chromium native WebAuthn/CTAP2の旧鍵移行matrix。
+// navigator.credentials、HTTP応答、暗号検証を置換しない。CDPは合成認証器の
+// 能力/本人確認/タッチだけを制御し、credentialのexport/import/deleteはしない。
+// 旧鍵fixtureだけは実optionsのuser.idとresident指定を変更してnative createする。
+// 登録attestationはuser handleを署名しないため、本番verifier/storeで保存できる。
+// 現行製品の登録動作の再現ではなく、旧random handle保存状態の明示的な合成である。
+// 実スマホ/OSのprovider選択/物理鍵は対象外。mobileはChromiumのviewportのみ。
+import { join } from "@std/path";
+import { type Browser, type CDPSession, chromium, type Page } from "playwright";
+import { serveProductionShell } from "./static_shell.ts";
+
+const [backend, origin, build, handlePrefix, artifacts] = Deno.args;
+if (!backend || !origin || !build || !handlePrefix || !artifacts) {
+  throw new Error(
+    "Expected owned Backend, origin, production build, synthetic handle prefix, artifacts",
+  );
+}
+const started = performance.now();
+const server = await serveProductionShell(backend, origin, build);
+let browser: Browser | undefined;
+let phase = "launch";
+const rows: {
+  resident: boolean;
+  authenticator: string;
+  outcome: string;
+  elapsed_ms: number;
+}[] = [];
+class NativeCheckError extends Error {}
+function check(condition: unknown, diagnostic: string): asserts condition {
+  // 値をdumpするassertEqualsは使わない。例外/HTTP本文/credential/cookieをログに残さない。
+  if (!condition) throw new NativeCheckError(diagnostic);
+}
+type User = { user_id: string; account_id: string; handle: string };
+type Key = {
+  key_reference: string;
+  normal_login_verified_at: string | null;
+  last_used_at: string | null;
+};
+async function whoami(page: Page) {
+  const response = await page.request.get(`${origin}/api/auth/whoami`);
+  check(response.status() === 200, "whoami status");
+  return await response.json() as {
+    actor: User | null;
+    authentication_reference: string | null;
+    session: { kind: string };
+  };
+}
+async function owner(page: Page, user: User, reference?: string) {
+  const current = await whoami(page);
+  check(
+    current.session.kind === "authenticated" &&
+      current.actor?.user_id === user.user_id &&
+      current.actor.account_id === user.account_id &&
+      current.actor.handle === user.handle,
+    "authenticated owner mismatch",
+  );
+  check(
+    typeof current.authentication_reference === "string",
+    "missing authentication reference",
+  );
+  if (reference) {
+    check(
+      current.authentication_reference === reference,
+      "issued authentication mismatch",
+    );
+  }
+  return current;
+}
+async function keys(page: Page, user: User): Promise<Key[]> {
+  const response = await page.request.get(`${origin}/api/auth/passkeys`);
+  check(response.status() === 200, "key list status");
+  const result = await response.json();
+  check(
+    result.user.user_id === user.user_id &&
+      result.user.account_id === user.account_id,
+    "key list owner",
+  );
+  return result.keys;
+}
+async function presence(
+  cdp: CDPSession,
+  authenticatorId: string,
+  enabled: boolean,
+) {
+  await cdp.send("WebAuthn.setAutomaticPresenceSimulation", {
+    authenticatorId,
+    enabled,
+  });
+}
+async function authenticator(
+  cdp: CDPSession,
+  resident: boolean,
+  automaticPresenceSimulation = true,
+) {
+  return (await cdp.send("WebAuthn.addVirtualAuthenticator", {
+    options: {
+      protocol: "ctap2",
+      transport: "usb",
+      hasResidentKey: resident,
+      hasUserVerification: true,
+      isUserVerified: true,
+      automaticPresenceSimulation,
+    },
+  })).authenticatorId;
+}
+async function account(page: Page) {
+  await page.goto(origin + "/account");
+  await page.getByRole("heading", { name: "Account", exact: true }).waitFor();
+  await page.getByRole("button", { name: "Log out", exact: true }).waitFor();
+}
+async function logout(page: Page) {
+  await account(page);
+  await page.getByRole("button", { name: "Log out", exact: true }).click();
+  await page.waitForURL((url) => url.origin === origin && url.pathname === "/");
+  check(
+    (await whoami(page)).session.kind === "anonymous",
+    "logout must clear authentication",
+  );
+}
+async function login(page: Page, user: User, legacy: boolean) {
+  await page.goto(origin + "/login?returnTo=%2Faccount");
+  const button = page.getByRole("button", {
+    name: legacy ? "Log in with older key" : "Log in with passkey",
+    exact: true,
+  });
+  if (legacy) {
+    await page.getByText("Use an older key with account ID", { exact: true })
+      .click();
+    await page.getByLabel("Account ID (handle)", { exact: true }).fill(
+      user.handle,
+    );
+  } else {
+    // 互換入口は閉じたまま。通常loginのrequestにhandle/user/accountが入らないことも検査する。
+    check(
+      !await page.getByLabel("Account ID (handle)", { exact: true })
+        .isVisible(),
+      "normal login asks for ID",
+    );
+  }
+  const options = page.waitForResponse((r) =>
+    new URL(r.url()).pathname === "/api/auth/passkeys/login/options"
+  );
+  const complete = page.waitForResponse((r) =>
+    new URL(r.url()).pathname === "/api/auth/passkeys/login/complete"
+  );
+  await button.click();
+  const optionResponse = await options;
+  check(optionResponse.status() === 200, "login options status");
+  const input = optionResponse.request().postDataJSON();
+  if (!legacy) {
+    check(
+      Object.keys(input).every((key) => key === "browser_origin"),
+      "normal login selected an account",
+    );
+    const wire = await optionResponse.json();
+    check(
+      !wire.public_key.publicKey.allowCredentials?.length,
+      "normal login sends an allow-list",
+    );
+  }
+  const response = await complete;
+  check(response.status() === 200, "native login complete status");
+  const issued = await response.json();
+  check(
+    issued.user.user_id === user.user_id &&
+      issued.user.account_id === user.account_id,
+    "login returned wrong owner",
+  );
+  await page.waitForURL((url) => url.pathname === "/account");
+  await owner(page, user, issued.authentication_reference);
+}
+
+const terminate = () => {
+  void (async () => {
+    await browser?.close();
+    await server.shutdown();
+    Deno.exit(143);
+  })();
+};
+Deno.addSignalListener("SIGTERM", terminate);
+try {
+  browser = await chromium.launch({ headless: true, timeout: 15_000 });
+  for (const resident of [false, true]) {
+    const context = await browser.newContext({
+      viewport: { width: 1280, height: 900 },
+      serviceWorkers: "block",
+    });
+    context.setDefaultTimeout(12_000);
+    // 製品もfixtureも外部通信しない。loopback proxy以外へのbrowser requestは拒否する。
+    await context.route(
+      "**/*",
+      (route) =>
+        new URL(route.request().url()).origin === origin
+          ? route.continue()
+          : route.abort(),
+    );
+    let page = await context.newPage();
+    let pageErrors = 0;
+    page.on("pageerror", () => ++pageErrors);
+    let cdp = await context.newCDPSession(page);
+    await cdp.send("WebAuthn.enable", { enableUI: false });
+    // 両行とも認証器はresident key対応にする。residentは旧credentialの作成指定だけを変え、
+    // resident必須の追加が能力不足で拒否されるケースとduplicate exclusionを混同しない。
+    const old = await authenticator(cdp, true);
+    let completionPosts = 0;
+    const completions = () => completionPosts;
+    page.on("request", (r) => {
+      if (
+        new URL(r.url()).pathname === "/api/auth/passkeys/addition/complete"
+      ) ++completionPosts;
+    });
+    try {
+      phase = `legacy-fixture-resident-${resident}`;
+      await page.goto(origin + "/register");
+      // 生options/credentialはpage内にとどめる。user.id/residency以外はServerの要求を維持する。
+      const fixture = await page.evaluate(async ({ handle, resident }) => {
+        const post = async (path: string, body: unknown) => {
+          const response = await fetch(path, {
+            method: "POST",
+            headers: { "content-type": "application/json" },
+            body: JSON.stringify(body),
+          });
+          if (!response.ok) {
+            throw new Error("synthetic legacy fixture HTTP rejected");
+          }
+          return await response.json();
+        };
+        const wire = await post("/api/auth/passkeys/registration/options", {
+          handle,
+          display_name: "Synthetic native migration",
+          browser_origin: location.origin,
+        });
+        const bytes = (value: string) =>
+          Uint8Array.from(
+            atob(value.replaceAll("-", "+").replaceAll("_", "/")),
+            (c) => c.charCodeAt(0),
+          );
+        const options = wire.public_key.publicKey;
+        const random = crypto.getRandomValues(new Uint8Array(32));
+        const stable = bytes(options.user.id);
+        const differs = stable.length !== random.length ||
+          stable.some((byte: number, index: number) => byte !== random[index]);
+        options.challenge = bytes(options.challenge);
+        options.user.id = random;
+        options.excludeCredentials = options.excludeCredentials?.map((
+          item: { id: string },
+        ) => ({ ...item, id: bytes(item.id) }));
+        options.authenticatorSelection = {
+          ...options.authenticatorSelection,
+          residentKey: resident ? "required" : "discouraged",
+          requireResidentKey: resident,
+        };
+        const credential = await navigator.credentials.create({
+          publicKey: options,
+        }) as PublicKeyCredential | null;
+        if (
+          !credential ||
+          !(credential.response instanceof AuthenticatorAttestationResponse)
+        ) throw new Error("native attestation missing");
+        const encode = (value: ArrayBuffer) =>
+          btoa(String.fromCharCode(...new Uint8Array(value))).replaceAll(
+            "+",
+            "-",
+          ).replaceAll("/", "_").replaceAll("=", "");
+        const issued = await post("/api/auth/passkeys/registration/complete", {
+          challenge_id: wire.challenge_id,
+          credential: {
+            id: credential.id,
+            rawId: encode(credential.rawId),
+            type: credential.type,
+            response: {
+              attestationObject: encode(credential.response.attestationObject),
+              clientDataJSON: encode(credential.response.clientDataJSON),
+              transports: credential.response.getTransports(),
+            },
+            extensions: credential.getClientExtensionResults(),
+          },
+        });
+        return {
+          user: issued.user,
+          authentication_reference: issued.authentication_reference,
+          randomDiffersFromStable: differs,
+        };
+      }, {
+        handle: `${handlePrefix}-${resident ? "resident" : "nonresident"}`,
+        resident,
+      });
+      check(
+        fixture.randomDiffersFromStable,
+        "fixture must use a legacy random handle",
+      );
+      const user: User = fixture.user;
+      await owner(page, user, fixture.authentication_reference);
+      const initial = await keys(page, user);
+      check(
+        initial.length === 1 && initial[0].normal_login_verified_at === null,
+        "legacy key initially unverified",
+      );
+      const oldReference = initial[0].key_reference;
+      await logout(page);
+      phase = `older-key-login-before-resident-${resident}`;
+      await login(page, user, true);
+
+      phase = `same-authenticator-excluded-resident-${resident}`;
+      const sameStarted = performance.now();
+      const add = () =>
+        page.getByRole("button", {
+          name: `Add passkey to ${user.handle}`,
+          exact: true,
+        });
+      const optionsResponse = page.waitForResponse((r) =>
+        new URL(r.url()).pathname === "/api/auth/passkeys/addition/options"
+      );
+      await add().click();
+      check(
+        (await optionsResponse).status() === 200,
+        "addition options status",
+      );
+      const excluded = page.getByRole("alert").filter({
+        hasText: "[authenticator/excluded]",
+      });
+      await excluded.waitFor({ state: "visible" });
+      check(
+        (await excluded.innerText()).includes(
+          "different device, security key, or passkey provider",
+        ),
+        "exclusion needs a concrete alternative",
+      );
+      check(
+        (await excluded.innerText()).includes("do not delete"),
+        "exclusion must preserve working access",
+      );
+      check(
+        completions() === 0,
+        "native exclusion must not submit completion",
+      );
+      const afterExcluded = await keys(page, user);
+      check(
+        afterExcluded.length === 1 &&
+          afterExcluded[0].key_reference === oldReference,
+        "exclusion changed old key",
+      );
+      await owner(page, user);
+      rows.push({
+        resident,
+        authenticator: "same",
+        outcome: "native-exclusion-no-completion-old-key-preserved",
+        elapsed_ms: Math.round(performance.now() - sameStarted),
+      });
+
+      phase = `other-authenticator-pending-resident-${resident}`;
+      const otherStarted = performance.now();
+      // CDPの仮想認証器選択は物理providerの選択UIを再現しない。別targetに別認証器を置き、
+      // 旧targetと旧鍵は生存させる。共有contextの既存sessionを使い、cookie/鍵の移送はしない。
+      const legacyPage = page;
+      const legacyCdp = cdp;
+      page = await context.newPage();
+      page.on("pageerror", () => ++pageErrors);
+      page.on("request", (r) => {
+        if (
+          new URL(r.url()).pathname === "/api/auth/passkeys/addition/complete"
+        ) ++completionPosts;
+      });
+      cdp = await context.newCDPSession(page);
+      await cdp.send("WebAuthn.enable", { enableUI: false });
+      const newer = await authenticator(cdp, true, false);
+      await account(page);
+      // options応答後、native操作はCTAPのpresence=falseで止める。timeout/sleepでpromptを推測しない。
+      const beforeAddition = await owner(page, user);
+      const additionOptions = page.waitForResponse((r) =>
+        new URL(r.url()).pathname === "/api/auth/passkeys/addition/options"
+      );
+      const additionComplete = page.waitForResponse((r) =>
+        new URL(r.url()).pathname === "/api/auth/passkeys/addition/complete"
+      );
+      await add().click();
+      const optionResponse = await additionOptions;
+      check(
+        optionResponse.status() === 200,
+        "other authenticator options status",
+      );
+      let optionsInput = optionResponse.request().postDataJSON();
+      check(
+        optionsInput.expected_user_id === user.user_id &&
+          optionsInput.expected_account_id === user.account_id &&
+          optionsInput.expected_authentication_reference ===
+            beforeAddition.authentication_reference,
+        "addition must fence displayed owner and session",
+      );
+      let wire = await optionResponse.json();
+      check(
+        wire.public_key.publicKey.excludeCredentials.length === 1,
+        "old credential must remain excluded",
+      );
+      check(
+        wire.public_key.publicKey.authenticatorSelection.userVerification ===
+          "required",
+        "addition must require UV",
+      );
+      check(
+        wire.public_key.publicKey.authenticatorSelection.residentKey ===
+          "required",
+        "product addition must require residency",
+      );
+      const pending = page.getByRole("status").filter({
+        hasText: "Waiting for passkey addition",
+      });
+      await pending.waitFor({ state: "visible" });
+      check(
+        await page.getByRole("heading", { name: "Account", exact: true })
+          .isVisible(),
+        "account hidden while native pending",
+      );
+      check(
+        await add().isDisabled() && completions() === 0,
+        "pending must prevent duplicate/early completion",
+      );
+      for (
+        const viewport of [{ width: 1280, height: 900 }, {
+          width: 390,
+          height: 844,
+        }]
+      ) {
+        await page.setViewportSize(viewport);
+        await pending.scrollIntoViewIfNeeded();
+        check(
+          await pending.isVisible(),
+          "pending must remain visible at viewport",
+        );
+        await page.screenshot({
+          path: join(
+            artifacts,
+            `native-addition-pending-${resident}-${viewport.width}.png`,
+          ),
+          fullPage: false,
+        });
+      }
+      await page.setViewportSize({ width: 1280, height: 900 });
+      // presence=falseで既に待機中のCTAP要求を後からtrueにして解放できるとは仮定しない。
+      // pending/取消と成功を分ける。送信前の停止を確認し、別ceremonyを明示開始する。
+      await page.getByRole("button", { name: "Stop waiting", exact: true })
+        .click();
+      await page.getByRole("alert").filter({
+        hasText: "Completion was not sent.",
+      }).waitFor();
+      check(
+        completions() === 0 && (await keys(page, user)).length === 1,
+        "cancel before touch must not save or complete",
+      );
+      await presence(cdp, newer, true);
+      const freshOptions = page.waitForResponse((r) =>
+        new URL(r.url()).pathname === "/api/auth/passkeys/addition/options"
+      );
+      await add().click();
+      const freshResponse = await freshOptions;
+      check(freshResponse.status() === 200, "fresh addition options status");
+      optionsInput = freshResponse.request().postDataJSON();
+      wire = await freshResponse.json();
+      phase = `other-authenticator-completion-resident-${resident}`;
+      const complete = await additionComplete;
+      check(complete.status() === 200, "native addition complete status");
+      const issued = await complete.json();
+      check(
+        issued.user.user_id === user.user_id &&
+          issued.user.account_id === user.account_id &&
+          typeof issued.authentication_reference === "string",
+        "addition complete owner/reference",
+      );
+      await page.getByRole("status").filter({
+        hasText: "Passkey added to your account",
+      }).waitFor({ state: "visible" });
+      await owner(page, user, issued.authentication_reference);
+      check(completions() === 1, "addition must submit exactly once");
+      // 元のbinding referenceはreceipt照合用。Cookie発行後も同じ現在ownerから確認する。
+      const receipt = await page.request.post(
+        `${origin}/api/auth/passkeys/addition/result`,
+        {
+          headers: { Origin: origin },
+          data: {
+            challenge_id: wire.challenge_id,
+            expected_user_id: user.user_id,
+            expected_account_id: user.account_id,
+            expected_authentication_reference:
+              optionsInput.expected_authentication_reference,
+          },
+        },
+      );
+      check(
+        receipt.status() === 200,
+        "saved addition receipt after Cookie issuance",
+      );
+      const saved = await receipt.json();
+      check(
+        saved.status === "saved" && saved.user.user_id === user.user_id &&
+          saved.user.account_id === user.account_id,
+        "receipt must identify saved owner",
+      );
+      const added = await keys(page, user);
+      check(
+        added.length === 2 &&
+          added.some((key) => key.key_reference === oldReference),
+        "addition must retain older key",
+      );
+      const newKey = added.find((key) => key.key_reference !== oldReference);
+      check(
+        newKey && saved.key.key_reference === newKey.key_reference &&
+          newKey.normal_login_verified_at === null,
+        "storage must not assert normal login",
+      );
+      await logout(page);
+      phase = `handle-free-login-resident-${resident}`;
+      await login(page, user, false);
+      const verified = await keys(page, user);
+      check(
+        verified.length === 2 &&
+          verified.find((key) => key.key_reference === newKey.key_reference)
+              ?.normal_login_verified_at != null,
+        "actual handle-free verifier success must mark the new key",
+      );
+      check(
+        verified.find((key) => key.key_reference === oldReference)
+          ?.normal_login_verified_at === null,
+        "normal login must not mark the unused legacy key",
+      );
+      await logout(page);
+      phase = `older-key-login-after-resident-${resident}`;
+      await presence(cdp, newer, false);
+      page = legacyPage;
+      cdp = legacyCdp;
+      await presence(cdp, old, true);
+      await login(page, user, true);
+      const retained = await keys(page, user);
+      check(
+        retained.length === 2 &&
+          retained.find((key) => key.key_reference === oldReference)
+              ?.last_used_at != null,
+        "older key must remain usable after migration",
+      );
+      check(
+        retained.find((key) => key.key_reference === newKey.key_reference)
+          ?.normal_login_verified_at != null,
+        "older login must preserve new key verification",
+      );
+      check(pageErrors === 0, "product page emitted an uncaught error");
+      rows.push({
+        resident,
+        authenticator: "other",
+        outcome:
+          "saved-correct-owner-handle-free-verified-older-login-preserved",
+        elapsed_ms: Math.round(performance.now() - otherStarted),
+      });
+    } finally {
+      await context.close();
+    }
+  }
+  await Deno.writeTextFile(
+    join(artifacts, "native-migration-result.json"),
+    JSON.stringify(
+      {
+        status: "passed",
+        boundary:
+          "real Backend/static shell/native Chromium CTAP2; synthetic legacy creation override only",
+        chromium: browser.version(),
+        rows,
+        elapsed_ms: Math.round(performance.now() - started),
+        viewports: ["1280x900", "390x844"],
+        physical_smartphone: "unconfirmed",
+        physical_authenticator: "unconfirmed",
+      },
+      null,
+      2,
+    ),
+  );
+  console.error(
+    `native-migration: PASS ${rows.length} matrix rows; ${
+      Math.round(performance.now() - started)
+    }ms`,
+  );
+} catch (error) {
+  const diagnostic = error instanceof NativeCheckError
+    ? error.message
+    : "browser-or-tool-operation-failed";
+  await Deno.writeTextFile(
+    join(artifacts, "native-migration-result.json"),
+    JSON.stringify(
+      {
+        status: "failed",
+        phase,
+        diagnostic,
+        rows,
+        elapsed_ms: Math.round(performance.now() - started),
+        physical_smartphone: "unconfirmed",
+        physical_authenticator: "unconfirmed",
+      },
+      null,
+      2,
+    ),
+  );
+  // Playwrightの例外にはrequest/引数を含み得るため本文やstackを保存しない。
+  console.error(
+    `native-migration: FAIL phase=${phase}; completed_rows=${rows.length}; elapsed_ms=${
+      Math.round(performance.now() - started)
+    }`,
+  );
+  Deno.exitCode = 1;
+} finally {
+  Deno.removeSignalListener("SIGTERM", terminate);
+  await browser?.close();
+  await server.shutdown();
+}
diff --git a/tests/e2e/browser/static_shell.ts b/tests/e2e/browser/static_shell.ts
new file mode 100644
index 000000000..c603bc533
--- /dev/null
+++ b/tests/e2e/browser/static_shell.ts
@@ -0,0 +1,76 @@
+// 実Backendへの透過proxyと本番SPA配信をbrowser suite間で共有する。
+// Cookie/Origin/署名検証/認可は置換しない。fixture入口は呼出側が明示的に渡す。
+import { extname, join, normalize } from "@std/path";
+
+export async function serveProductionShell(
+  backend: string,
+  origin: string,
+  build: string,
+  fixture?: (request: Request) => Promise<Response | undefined>,
+) {
+  for (const address of [backend, origin]) {
+    const url = new URL(address);
+    if (
+      url.protocol !== "http:" ||
+      !["localhost", "127.0.0.1"].includes(url.hostname) || !url.port
+    ) {
+      throw new Error("Browser E2E requires explicit owned loopback endpoints");
+    }
+  }
+  await Deno.stat(join(build, "index.html")); // 暗黙buildや別asset rootへのfallbackはしない。
+  const mime: Record<string, string> = {
+    ".html": "text/html; charset=utf-8",
+    ".js": "text/javascript",
+    ".css": "text/css",
+    ".json": "application/json",
+    ".svg": "image/svg+xml",
+    ".png": "image/png",
+    ".woff2": "font/woff2",
+    ".ico": "image/x-icon",
+  };
+  return Deno.serve({
+    hostname: "127.0.0.1",
+    port: Number(new URL(origin).port),
+    onListen() {},
+  }, async (request) => {
+    const url = new URL(request.url);
+    const special = await fixture?.(request);
+    if (special) return special;
+    if (url.pathname.startsWith("/api/")) {
+      const headers = new Headers(request.headers);
+      headers.delete("host");
+      headers.delete("connection");
+      return await fetch(new URL(url.pathname + url.search, backend), {
+        method: request.method,
+        headers,
+        body: ["GET", "HEAD"].includes(request.method)
+          ? undefined
+          : await request.arrayBuffer(),
+        redirect: "manual",
+      });
+    }
+    const relative = normalize(
+      url.pathname.replace(/^\/+/, "") || "index.html",
+    );
+    if (relative.startsWith("..")) {
+      return new Response("not found", { status: 404 });
+    }
+    let file = join(build, relative);
+    try {
+      if ((await Deno.stat(file)).isDirectory) file = join(file, "index.html");
+      return new Response(await Deno.readFile(file), {
+        headers: {
+          "content-type": mime[extname(file)] ?? "application/octet-stream",
+        },
+      });
+    } catch (error) {
+      if (!(error instanceof Deno.errors.NotFound)) throw error;
+      if (url.pathname.startsWith("/_app/")) {
+        return new Response("not found", { status: 404 });
+      }
+      return new Response(await Deno.readFile(join(build, "index.html")), {
+        headers: { "content-type": mime[".html"] },
+      });
+    }
+  });
+}
diff --git a/tests/e2e/src/worker_environment.rs b/tests/e2e/src/worker_environment.rs
index 14e01d73d..4ec279c14 100644
--- a/tests/e2e/src/worker_environment.rs
+++ b/tests/e2e/src/worker_environment.rs
@@ -1074,6 +1074,27 @@ impl WorkerE2eEnvironment {
         Ok(output)
     }
 
+    /// browser toolだけに必要なtool探索設定を引き継ぎ、profile・HOME・XDG・一時領域は
+    /// このfixtureへ閉じ込める。DENO_DIR/PLAYWRIGHT_BROWSERS_PATHはインストール済みtoolの
+    /// 供給元であり、製品データや認証情報を引き継ぐ経路にはしない。
+    pub fn browser_command(&self, binary: &Path) -> Result<Command> {
+        let snapshot: std::collections::HashMap<_, _> = std::env::vars_os().collect();
+        let mut command = self.isolated_command(binary);
+        for name in ["PATH", "DENO_DIR", "PLAYWRIGHT_BROWSERS_PATH"] {
+            if let Some(value) = snapshot.get(std::ffi::OsStr::new(name)) {
+                command.env(name, value);
+            }
+        }
+        let temporary = self.root.join("browser-tmp");
+        let cache = self.root.join("browser-cache");
+        fs::create_dir_all(&temporary)?;
+        fs::create_dir_all(&cache)?;
+        command
+            .env("TMPDIR", temporary)
+            .env("XDG_CACHE_HOME", cache);
+        Ok(command)
+    }
+
     fn isolated_command(&self, binary: &Path) -> Command {
         let mut command = Command::new(binary);
         command
diff --git a/tests/e2e/tests/auth_passkeys.rs b/tests/e2e/tests/auth_passkeys.rs
index 7195bb3bb..a6ccaa3db 100644
--- a/tests/e2e/tests/auth_passkeys.rs
+++ b/tests/e2e/tests/auth_passkeys.rs
@@ -4,8 +4,9 @@
 //! `cargo test -p yoi-e2e --features e2e --test auth_passkeys`で明示選択する。
 //! binary供給、HOME/XDG/DB/動的port、readiness、ログ、RAII回収は共有harnessが所有する。
 //! 通常ケースのHTTPはproxy／redirect／cookie storeなし、各要求にtimeoutを設ける。
-//! 実Server CLIにはstatic assets設定経路がない。追加の明示選択browser_sessionsだけが
-//! 本番static shellをloopback proxyで実Backendへ接続し、Cookieの自然消失と復帰を検証する。
+//! 実Server CLIにはstatic assets設定経路がない。明示選択browser_sessionsは本番static shellを
+//! loopback proxyで実Backendへ接続し、Cookieの自然消失と復帰を検証する。
+//! native_migrationは同じshellと実BackendをChromium native WebAuthn/CTAP2へ接続する。
 //! 固定expiry sessionを公開store APIで作るfixture境界と、14日実時間経過の未検証は同moduleに記す。
 
 use std::error::Error;
@@ -21,8 +22,8 @@ use serde::Deserialize;
 use serde::de::DeserializeOwned;
 use serde_json::{Value, json};
 use server_api::{
-    ActorAuthMethod, AuthUserResponse, AuthenticatedUser, PasskeyLoginCompleteRequest,
-    PasskeyLoginOptionsResponse, PasskeyRegistrationCompleteRequest,
+    ActorAuthMethod, AuthUserResponse, AuthenticatedUser, PasskeyAdditionOptionsRequest,
+    PasskeyLoginCompleteRequest, PasskeyLoginOptionsResponse, PasskeyRegistrationCompleteRequest,
     PasskeyRegistrationOptionsResponse, WhoamiResponse,
 };
 #[path = "../src/resident_authenticator.rs"]
@@ -30,8 +31,12 @@ mod resident_model;
 use resident_model::ResidentAuthenticator;
 use yoi_e2e::WorkerE2eEnvironment;
 
+#[path = "auth_passkeys/browser_process.rs"]
+mod browser_process;
 #[path = "auth_passkeys/browser_sessions.rs"]
 mod browser_sessions;
+#[path = "auth_passkeys/native_migration.rs"]
+mod native_migration;
 
 type Result<T = ()> = std::result::Result<T, Box<dyn Error>>;
 const BROWSER_ORIGIN: &str = "http://localhost:5173";
@@ -270,6 +275,29 @@ fn logout(client: &Client, base: &str, artifacts: &Path, cookie: &str) -> Result
     Ok(())
 }
 
+// fixtureも現在の本人/認証bindingをwhoamiから取得する。期待値は対象を選ぶ権限ではない。
+fn addition_expectation(
+    request: RequestBuilder,
+    artifacts: &Path,
+) -> Result<PasskeyAdditionOptionsRequest> {
+    let identity: WhoamiResponse = decode(send(
+        request,
+        "read addition owner and authentication reference",
+        artifacts,
+    )?)?;
+    let actor = identity
+        .actor
+        .ok_or("addition fixture requires an authenticated actor")?;
+    Ok(PasskeyAdditionOptionsRequest {
+        expected_user_id: actor.user_id,
+        expected_account_id: actor.account_id,
+        expected_authentication_reference: identity
+            .authentication_reference
+            .ok_or("missing addition authentication reference")?,
+        browser_origin: Some(BROWSER_ORIGIN.to_owned()),
+    })
+}
+
 fn host_admin_login(
     environment: &WorkerE2eEnvironment,
     client: &Client,
@@ -291,11 +319,17 @@ fn host_admin_login(
     let bearer = setup["access_token"]
         .as_str()
         .ok_or("host setup omitted initial bearer")?;
+    let addition_body = addition_expectation(
+        client
+            .get(format!("{base}/api/auth/whoami"))
+            .bearer_auth(bearer),
+        artifacts,
+    )?;
     let options: PasskeyRegistrationOptionsResponse = decode(send(
         client
             .post(format!("{base}/api/auth/passkeys/addition/options"))
             .bearer_auth(bearer)
-            .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+            .json(&addition_body),
         "host-created administrator bearer starts actor-derived passkey addition",
         artifacts,
     )?)?;
@@ -348,6 +382,12 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
     policy(&client, base, artifacts, false)?;
     let mut admin_key = ResidentAuthenticator::new(true);
     let (admin, admin_cookie) = host_admin_login(&environment, &client, &mut admin_key)?;
+    let admin_addition = addition_expectation(
+        client
+            .get(format!("{base}/api/auth/whoami"))
+            .header(COOKIE, &admin_cookie),
+        artifacts,
+    )?;
     policy(&client, base, artifacts, false)?;
     set_policy(&client, base, artifacts, &admin_cookie, true)?;
     let whoami: Value = decode(send(
@@ -379,7 +419,7 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
             client
                 .post(format!("{base}/api/auth/passkeys/addition/options"))
                 .header(ORIGIN, BROWSER_ORIGIN)
-                .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+                .json(&admin_addition),
             "unauthenticated addition options",
             artifacts,
         )?,
@@ -445,12 +485,18 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
     )?)?;
     assert!(options.public_key.public_key.allow_credentials.is_empty());
 
+    let addition_body = addition_expectation(
+        client
+            .get(format!("{base}/api/auth/whoami"))
+            .header(COOKIE, &cookie),
+        artifacts,
+    )?;
     for (field, value) in [
         ("handle", &other.user.handle),
         ("user_id", &other.user.user_id),
         ("account_id", &other.user.account_id),
     ] {
-        let mut body = json!({"browser_origin": BROWSER_ORIGIN});
+        let mut body = serde_json::to_value(&addition_body)?;
         body[field] = json!(value);
         rejected(
             send(
@@ -470,7 +516,7 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
         let mut request = client
             .post(format!("{base}/api/auth/passkeys/addition/options"))
             .header(COOKIE, &cookie)
-            .json(&json!({"browser_origin": BROWSER_ORIGIN}));
+            .json(&addition_body);
         if let Some(origin) = origin {
             request = request.header(ORIGIN, origin);
         }
@@ -490,7 +536,7 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
             .post(format!("{base}/api/auth/passkeys/addition/options"))
             .header(COOKIE, &cookie)
             .header(ORIGIN, BROWSER_ORIGIN)
-            .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+            .json(&addition_body),
         "authenticated self addition options",
         artifacts,
     )?)?;
@@ -591,7 +637,7 @@ fn disabled_registration_preserves_existing_login_self_addition_and_workspace_ow
                     .post(format!("{base}/api/auth/passkeys/addition/options"))
                     .header(COOKIE, revoked_cookie)
                     .header(ORIGIN, BROWSER_ORIGIN)
-                    .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+                    .json(&addition_body),
                 "logout prevents further self addition with the old cookie",
                 artifacts,
             )?,
@@ -1797,7 +1843,8 @@ fn activation_codes_challenges_and_unverified_state_cannot_cross_account_or_purp
             client.post(format!("{base}/api/auth/device-login/approve")).header(ORIGIN, BROWSER_ORIGIN)
                 .json(&json!({"user_code": flow["user_code"]})),
             client.post(format!("{base}/api/auth/passkeys/addition/options")).header(ORIGIN, BROWSER_ORIGIN)
-                .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+                .json(&json!({"browser_origin": BROWSER_ORIGIN, "expected_user_id": issue.user.user_id,
+                    "expected_account_id": issue.user.account_id, "expected_authentication_reference": "unauthenticated-fixture-not-a-credential"})),
         ];
         for mut request in requests {
             if let Some(bearer) = bearer {
@@ -1901,7 +1948,12 @@ fn activation_codes_challenges_and_unverified_state_cannot_cross_account_or_purp
             .post(format!("{base}/api/auth/passkeys/addition/options"))
             .header(COOKIE, &cookie)
             .header(ORIGIN, BROWSER_ORIGIN)
-            .json(&json!({"browser_origin": BROWSER_ORIGIN})),
+            .json(&addition_expectation(
+                client
+                    .get(format!("{base}/api/auth/whoami"))
+                    .header(COOKIE, &cookie),
+                artifacts,
+            )?),
         "start distinct authenticated self-addition ceremony",
         artifacts,
     )?)?;
diff --git a/tests/e2e/tests/auth_passkeys/browser_process.rs b/tests/e2e/tests/auth_passkeys/browser_process.rs
new file mode 100644
index 000000000..5a624b4c0
--- /dev/null
+++ b/tests/e2e/tests/auth_passkeys/browser_process.rs
@@ -0,0 +1,58 @@
+//! browser suiteの子process回収と実行期限を共有する。診断にraw IPCを複製しない。
+use super::*;
+use std::process::{Child, ExitStatus};
+use std::sync::mpsc;
+
+pub(super) struct BrowserProcess(pub(super) Option<Child>);
+impl BrowserProcess {
+    pub(super) fn child(&mut self) -> &mut Child {
+        self.0.as_mut().expect("browser process retained")
+    }
+
+    pub(super) fn wait_bounded(mut self, timeout: Duration) -> Result<ExitStatus> {
+        let mut child = self.0.take().expect("browser process retained");
+        let pid = child.id() as libc::pid_t;
+        let (send, receive) = mpsc::channel();
+        let waiter = std::thread::spawn(move || {
+            let _ = send.send(child.wait());
+        });
+        let result = receive.recv_timeout(timeout);
+        if result.is_err() {
+            unsafe {
+                libc::kill(pid, libc::SIGTERM);
+            }
+            if receive.recv_timeout(Duration::from_secs(3)).is_err() {
+                unsafe {
+                    libc::kill(pid, libc::SIGKILL);
+                }
+            }
+        }
+        let _ = waiter.join();
+        Ok(result.map_err(|_| "browser E2E timed out; see sanitized browser diagnostic")??)
+    }
+}
+impl Drop for BrowserProcess {
+    fn drop(&mut self) {
+        let Some(mut child) = self.0.take() else {
+            return;
+        };
+        if matches!(child.try_wait(), Ok(Some(_))) {
+            return;
+        }
+        let pid = child.id() as libc::pid_t;
+        // Denoのsignal handlerがPlaywright/HTTPを閉じる猶予を与える。
+        unsafe {
+            libc::kill(pid, libc::SIGTERM);
+        }
+        let (send, receive) = mpsc::channel();
+        let waiter = std::thread::spawn(move || {
+            let _ = send.send(child.wait());
+        });
+        if receive.recv_timeout(Duration::from_secs(3)).is_err() {
+            unsafe {
+                libc::kill(pid, libc::SIGKILL);
+            }
+        }
+        let _ = waiter.join();
+    }
+}
diff --git a/tests/e2e/tests/auth_passkeys/browser_sessions.rs b/tests/e2e/tests/auth_passkeys/browser_sessions.rs
index 7207e4124..86cdb92b2 100644
--- a/tests/e2e/tests/auth_passkeys/browser_sessions.rs
+++ b/tests/e2e/tests/auth_passkeys/browser_sessions.rs
@@ -8,10 +8,11 @@
 //! Deno/Playwright Chromiumと最新production buildが必要な明示選択suite:
 //! `cargo test -p yoi-e2e --features e2e --test auth_passkeys real_backend_browser -- --ignored`
 //! 通常auth_passkeysの成功/ignoreを、このbrowser接続の実行成功とは数えない。
+use super::browser_process::BrowserProcess;
 use super::*;
 use std::io::{BufRead, BufReader, Read};
 use std::net::TcpListener;
-use std::process::{Child, Command, Stdio};
+use std::process::Stdio;
 use std::sync::mpsc;
 use std::time::Instant;
 use yoi_workspace_server::auth::{
@@ -62,38 +63,6 @@ fn expired_session_fixture(environment: &WorkerE2eEnvironment) -> Result<Value>
     ]}))
 }
 
-struct BrowserProcess(Option<Child>);
-impl BrowserProcess {
-    fn child(&mut self) -> &mut Child {
-        self.0.as_mut().expect("browser process retained")
-    }
-}
-impl Drop for BrowserProcess {
-    fn drop(&mut self) {
-        let Some(mut child) = self.0.take() else {
-            return;
-        };
-        if matches!(child.try_wait(), Ok(Some(_))) {
-            return;
-        }
-        let pid = child.id() as libc::pid_t;
-        // Denoのsignal handlerがPlaywright/HTTPを閉じる猶予を与える。
-        unsafe {
-            libc::kill(pid, libc::SIGTERM);
-        }
-        let (send, receive) = mpsc::channel();
-        let waiter = std::thread::spawn(move || {
-            let _ = send.send(child.wait());
-        });
-        if receive.recv_timeout(Duration::from_secs(3)).is_err() {
-            unsafe {
-                libc::kill(pid, libc::SIGKILL);
-            }
-        }
-        let _ = waiter.join();
-    }
-}
-
 #[test]
 #[ignore = "requires production Web assets, Deno and Playwright Chromium"]
 fn real_backend_browser_cookies_preserve_identity_expiry_return_url_and_explicit_logout() -> Result
@@ -132,7 +101,8 @@ fn real_backend_browser_cookies_preserve_identity_expiry_return_url_and_explicit
     drop(reservation);
     let stderr = std::fs::File::create(environment.artifacts_dir.join("browser.stderr.log"))?;
     let mut process = BrowserProcess(Some(
-        Command::new("deno")
+        environment
+            .browser_command(Path::new("deno"))?
             .current_dir(&root)
             .args([
                 "run",
diff --git a/tests/e2e/tests/auth_passkeys/native_migration.rs b/tests/e2e/tests/auth_passkeys/native_migration.rs
new file mode 100644
index 000000000..6b774b4db
--- /dev/null
+++ b/tests/e2e/tests/auth_passkeys/native_migration.rs
@@ -0,0 +1,110 @@
+//! 実Backend・本番SPA・Chromium native WebAuthn + CTAP2による旧鍵移行。
+//! random user handle × resident=false/true × 同じ/別の認証器を検査する。
+//! 旧鍵fixtureのuser.id/residency指定だけを変更し、実attestationを本番verifier/storeへ送る。
+//! 現行登録を旧挙動と偽らず、SQL直書き・認証API/mock navigator置換はしない。
+//! 起動/DB/HOME/XDG/port/回収はWorkerE2eEnvironment、browser profileはその一時領域が所有する。
+//! DenoとPlaywright Chromium、最新production assets/binariesを呼出側が用意する。
+//! `cargo test -p yoi-e2e --features e2e --test auth_passkeys native_ctap2 -- --ignored`
+//! 暗黙buildを避ける実行時は既存providerの3つのbinary overrideを全て指定する。
+//! DENO_DIR/PLAYWRIGHT_BROWSERS_PATHは事前取得済みtoolの供給元として明示する。
+//! 物理鍵/実スマホ/provider選択は未確認。CI自動配線の代用にはしない。
+use super::browser_process::BrowserProcess;
+use super::*;
+use std::net::TcpListener;
+use std::process::Stdio;
+
+#[test]
+#[ignore = "requires production assets/binaries, cached Deno dependencies and Playwright Chromium"]
+fn native_ctap2_legacy_random_handle_residency_exclusion_and_other_authenticator_migration()
+-> Result {
+    let root = Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("../..")
+        .canonicalize()?;
+    let build = root.join("web/workspace/build");
+    if !build.join("index.html").is_file() {
+        return Err("native browser E2E requires an existing production Web build".into());
+    }
+    let mut environment = WorkerE2eEnvironment::new()?;
+    let reservation = TcpListener::bind("127.0.0.1:0")?;
+    let origin = format!("http://localhost:{}", reservation.local_addr()?.port());
+    std::fs::write(
+        &environment.server_config,
+        format!("[browser]\npublic_url = \"{origin}\"\n"),
+    )?;
+    environment.start_empty_backend()?;
+    let admin =
+        environment.setup_hosting_admin(&format!("{}-admin", environment.account_handle), true)?;
+    let bearer = admin["access_token"]
+        .as_str()
+        .ok_or("missing setup token")?;
+    let base = environment
+        .server_url
+        .as_deref()
+        .ok_or("missing Backend URL")?;
+    let response = http_client()?
+        .put(format!("{base}/api/hosting/settings"))
+        .bearer_auth(bearer)
+        .json(&json!({"self_registration_enabled": true}))
+        .send()?;
+    if !response.status().is_success() {
+        return Err("native fixture could not enable synthetic self-registration".into());
+    }
+    // Server public_urlと同一originを使う。API proxyだけでOrigin/Cookieを書き換えない。
+    drop(reservation);
+    let stderr =
+        std::fs::File::create(environment.artifacts_dir.join("native-browser.stderr.log"))?;
+    let mut command = environment.browser_command(Path::new("deno"))?;
+    command
+        .current_dir(&root)
+        .args([
+            "run",
+            "--config",
+            "tools/web-ux/deno.json",
+            "--no-lock",
+            "--cached-only",
+            "--allow-env",
+            "--allow-net=127.0.0.1,localhost",
+            "--allow-read",
+            "--allow-write",
+            "--allow-run",
+            "--allow-sys",
+            "tests/e2e/browser/native_passkey_migration.ts",
+            base,
+            &origin,
+            build.to_str().ok_or("non-UTF8 build path")?,
+            &environment.account_handle,
+            environment
+                .artifacts_dir
+                .to_str()
+                .ok_or("non-UTF8 artifacts path")?,
+        ])
+        .stdin(Stdio::null())
+        .stdout(Stdio::null())
+        .stderr(stderr);
+    let process = BrowserProcess(Some(command.spawn()?));
+    let status = process.wait_bounded(Duration::from_secs(180))?;
+    if !status.success() {
+        return Err(format!(
+            "native CTAP2 matrix failed; sanitized diagnostics: {}",
+            environment
+                .artifacts_dir
+                .join("native-browser.stderr.log")
+                .display()
+        )
+        .into());
+    }
+    let report: Value = serde_json::from_slice(&std::fs::read(
+        environment
+            .artifacts_dir
+            .join("native-migration-result.json"),
+    )?)?;
+    if report["status"] != "passed" || report["rows"].as_array().map(Vec::len) != Some(4) {
+        return Err("native browser did not confirm all four matrix rows".into());
+    }
+    let cleanup = environment.cleanup()?;
+    assert!(
+        cleanup.cleanup_success,
+        "owned native browser environment cleanup failed"
+    );
+    Ok(())
+}
diff --git a/web/workspace/deno.json b/web/workspace/deno.json
index 6b4622ebe..7384240af 100644
--- a/web/workspace/deno.json
+++ b/web/workspace/deno.json
@@ -21,7 +21,7 @@
     "check:repository-api": "cd ../.. && cargo run -q -p server-api --example generate_repository_openapi_types -- --check",
     "generate:ticket-api": "cd ../.. && cargo run -q -p server-api --example generate_ticket_api_types",
     "check:ticket-api": "cd ../.. && cargo run -q -p server-api --example generate_ticket_api_types -- --check",
-    "test:browser:auth": "mkdir -p ../../target/web-ux/tmp && TMPDIR=../../target/web-ux/tmp deno test --config ../../tools/web-ux/deno.json --allow-env --allow-net --allow-read --allow-write --allow-run --allow-sys test/auth-browser/auth-shell.browser.test.ts",
+    "test:browser:auth": "mkdir -p ../../target/web-ux/tmp && TMPDIR=../../target/web-ux/tmp deno test --config ../../tools/web-ux/deno.json --allow-env --allow-net --allow-read --allow-write --allow-run --allow-sys test/auth-browser/auth-shell.browser.test.ts test/auth-browser/passkey-state.browser.test.ts",
     "test:browser:entry": "mkdir -p ../../target/web-ux/tmp && TMPDIR=../../target/web-ux/tmp deno test --config ../../tools/web-ux/deno.json --allow-env --allow-net --allow-read --allow-write --allow-run --allow-sys test/auth-browser/entry-shell.browser.test.ts test/auth-browser/sidebar-shell.browser.test.ts"
   },
   "imports": {
diff --git a/web/workspace/src/lib/generated/auth-api.ts b/web/workspace/src/lib/generated/auth-api.ts
index 788ded8eb..cdd06d005 100644
--- a/web/workspace/src/lib/generated/auth-api.ts
+++ b/web/workspace/src/lib/generated/auth-api.ts
@@ -21,13 +21,33 @@ export type RequestActor = { user_id: string, account_id: string, handle: string
 
 export type BrowserSessionState = { "kind": "anonymous", } | { "kind": "authenticated", expires_at: string | null, } | { "kind": "expired", };
 
-export type WhoamiResponse = { actor: RequestActor | null, session: BrowserSessionState, };
+export type WhoamiResponse = { actor: RequestActor | null, session: BrowserSessionState,
+/**
+ * Non-secret comparison evidence, never an authentication credential.
+ */
+authentication_reference: string | null, };
 
 export type AuthBootstrapUserRequest = { handle: string, display_name?: string | null, };
 
-export type AuthUserResponse = { user: AuthenticatedUser, };
+export type AuthUserResponse = { user: AuthenticatedUser,
+/**
+ * Comparison evidence for the exact newly issued session, not a credential.
+ */
+authentication_reference: string, };
 
-export type PasskeyAdditionOptionsRequest = { browser_origin?: string | null, };
+export type PasskeyAdditionOptionsRequest = { expected_user_id: string, expected_account_id: string, expected_authentication_reference: string, browser_origin?: string | null, };
+
+export type PasskeySummary = { key_reference: string, created_at: string, last_used_at: string | null, normal_login_verified_at: string | null, };
+
+export type PasskeyListResponse = { user: AuthenticatedUser, keys: Array<PasskeySummary>, };
+
+export type PasskeyAdditionResultRequest = { challenge_id: string, expected_user_id: string, expected_account_id: string,
+/**
+ * Original options authentication reference; the current same-owner session may differ.
+ */
+expected_authentication_reference: string, };
+
+export type PasskeyAdditionResultResponse = { "status": "unknown", } | { "status": "saved", user: AuthenticatedUser, key: PasskeySummary, };
 
 export type PasskeyRegistrationOptionsRequest = { handle: string, display_name?: string | null, browser_origin?: string | null, };
 
diff --git a/web/workspace/src/lib/generated/companion-api.ts b/web/workspace/src/lib/generated/companion-api.ts
index ecd2b3f5d..88701f292 100644
--- a/web/workspace/src/lib/generated/companion-api.ts
+++ b/web/workspace/src/lib/generated/companion-api.ts
@@ -1,6 +1,6 @@
 // @generated by yoi-companion-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7)
+// Input contract: 0.1.0 (sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23)
 // Options: companion-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/companion-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_companion_api_types -- --check
diff --git a/web/workspace/src/lib/generated/repository-api.ts b/web/workspace/src/lib/generated/repository-api.ts
index bc61338f5..7e62713af 100644
--- a/web/workspace/src/lib/generated/repository-api.ts
+++ b/web/workspace/src/lib/generated/repository-api.ts
@@ -1,6 +1,6 @@
 // @generated by yoi-repository-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7)
+// Input contract: 0.1.0 (sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23)
 // Options: repository-operation-schema-closure,openapi-3.1,format:uint64=safe-number,strict-safe-integers,sorted-output
 // Output: web/workspace/src/lib/generated/repository-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_repository_openapi_types -- --check
diff --git a/web/workspace/src/lib/generated/runtime-api.ts b/web/workspace/src/lib/generated/runtime-api.ts
index 72647613a..5f678586c 100644
--- a/web/workspace/src/lib/generated/runtime-api.ts
+++ b/web/workspace/src/lib/generated/runtime-api.ts
@@ -1,6 +1,6 @@
 // @generated by yoi-runtime-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7)
+// Input contract: 0.1.0 (sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23)
 // Options: runtime-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/runtime-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_runtime_api_types -- --check
diff --git a/web/workspace/src/lib/generated/ticket-api.ts b/web/workspace/src/lib/generated/ticket-api.ts
index 18b0a6804..063ddd5ba 100644
--- a/web/workspace/src/lib/generated/ticket-api.ts
+++ b/web/workspace/src/lib/generated/ticket-api.ts
@@ -1,6 +1,6 @@
 // @generated by yoi-ticket-browser-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7)
+// Input contract: 0.1.0 (sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23)
 // Options: ticket-objective-merge-request-browser-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/ticket-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_ticket_api_types -- --check
diff --git a/web/workspace/src/lib/generated/worker-launch-api.ts b/web/workspace/src/lib/generated/worker-launch-api.ts
index 8dd4a964b..2497421ab 100644
--- a/web/workspace/src/lib/generated/worker-launch-api.ts
+++ b/web/workspace/src/lib/generated/worker-launch-api.ts
@@ -1,6 +1,6 @@
 // @generated by yoi-worker-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:5de3f3b716555717d3274b8c6a385fb66624585941628a53b8b3050cb58f8ab7)
+// Input contract: 0.1.0 (sha256:3e33a924668d7f7c07611d45b2fda7f1115c66431b741c94e1ff4e8e3e559b23)
 // Options: worker-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/worker-launch-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_worker_launch_api_types -- --check
diff --git a/web/workspace/src/lib/workspace/auth/AuthEntry.svelte b/web/workspace/src/lib/workspace/auth/AuthEntry.svelte
index 46e41c345..7023137e9 100644
--- a/web/workspace/src/lib/workspace/auth/AuthEntry.svelte
+++ b/web/workspace/src/lib/workspace/auth/AuthEntry.svelte
@@ -108,7 +108,7 @@
       <details class="legacy-login" bind:open={legacyOpen}>
         <summary>Use an older key with account ID</summary>
         <form onsubmit={(event) => { event.preventDefault(); void submit(true); }}>
-          <p class="muted">If an older key is not listed or cannot sign in above, use compatibility login. After login, open <a href="/account">Account</a> and add a discoverable passkey for ID-free login. Your existing keys are preserved.</p>
+          <p class="muted">If an older key is not listed or cannot sign in above, use compatibility login. After login, open <a href="/account">Account</a> to inspect keys and verify migration. Adding with the same older-key authenticator may be excluded; use a different saved-key provider or authenticator. Keep older keys until normal ID-free login to the intended account is tested.</p>
           <label>Account ID (handle)
             <input bind:value={handle} required maxlength="128" autocomplete="username" autocapitalize="off" spellcheck="false" disabled={auth.busy} aria-describedby="legacy-id-help" />
           </label>
@@ -131,6 +131,7 @@
     {/if}
   {/if}
   {#if auth.status}<p role="status">{auth.status}</p>{/if}
+  {#if auth.busy}<button type="button" onclick={() => auth.cancel()}>Stop waiting</button>{/if}
   {#if auth.error}<p role="alert" class="error">{auth.error}</p>{/if}
   <nav aria-label="Authentication">
     {#if mode === 'login' && auth.session.kind === 'ready' && !auth.actor}
diff --git a/web/workspace/src/lib/workspace/auth/SessionBoundary.svelte b/web/workspace/src/lib/workspace/auth/SessionBoundary.svelte
index 943d782e7..cdb5314fe 100644
--- a/web/workspace/src/lib/workspace/auth/SessionBoundary.svelte
+++ b/web/workspace/src/lib/workspace/auth/SessionBoundary.svelte
@@ -56,7 +56,7 @@
 {#if !protectedPage}
   {@render children()}
 {:else}
-  {#if session.kind === 'loading'}
+  {#if session.kind === 'loading' && !admitted}
     <div class="auth-page"><p role="status">Loading session…</p></div>
   {:else if session.kind === 'error'}
     <div class="auth-page">
@@ -66,7 +66,7 @@
     </div>
   {/if}
   {#if session.kind === 'ready' ? session.value.session.kind === 'authenticated' && sameActor : admitted}
-    <!-- 再確認中は表示/操作を停止し、進行中のlogout等をunmountで取消さない。 -->
-    <div hidden={session.kind !== 'ready'} inert={session.kind !== 'ready'}>{@render children()}</div>
+    <!-- 再確認中は既存内容と操作進捗を可視に保ち、操作だけをinertで停止する。 -->
+    <div hidden={session.kind === 'error'} inert={session.kind !== 'ready'}>{@render children()}</div>
   {/if}
 {/if}
diff --git a/web/workspace/src/lib/workspace/auth/activation.test.ts b/web/workspace/src/lib/workspace/auth/activation.test.ts
index acb1d0781..de5562a3b 100644
--- a/web/workspace/src/lib/workspace/auth/activation.test.ts
+++ b/web/workspace/src/lib/workspace/auth/activation.test.ts
@@ -1,10 +1,18 @@
 declare const Deno: { test(name: string, fn: () => Promise<void>): void };
+import { browserSession } from "./session-state.ts";
 import { activateWithPasskey } from "./activation.ts";
 import {
   authUser,
   credentialFixture,
   registrationOptions,
 } from "./api.test-fixtures.ts";
+function confirmedSession() {
+  return {
+    actor: { ...authUser, auth_method: "browser_session" },
+    authentication_reference: "fixture-authentication",
+    session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+  };
+}
 function equal(a: unknown, b: unknown) {
   if (JSON.stringify(a) !== JSON.stringify(b)) throw new Error("Values differ");
 }
@@ -52,9 +60,14 @@ Deno.test("activation uses only dedicated endpoints and confirms normalized targ
   await boundary(async (input, init) => {
     requests.push({ path: String(input), init: init! });
     return Response.json(
-      String(input).endsWith("/options")
+      String(input) === "/api/auth/whoami"
+        ? confirmedSession()
+        : String(input).endsWith("/options")
         ? registrationOptions
-        : { user: authUser },
+        : {
+          user: authUser,
+          authentication_reference: "fixture-authentication",
+        },
     );
   }, async (options) => {
     equal(options.signal === signal, true);
@@ -67,16 +80,21 @@ Deno.test("activation uses only dedicated endpoints and confirms normalized targ
     equal(requests.map((r) => r.path), [
       "/api/auth/activation/options",
       "/api/auth/activation/complete",
+      "/api/auth/whoami",
     ]);
-    for (const { init } of requests) {
-      equal(init.method, "POST");
+    for (const { path, init } of requests) {
+      equal(init.method ?? "GET", path === "/api/auth/whoami" ? "GET" : "POST");
+      equal(init.signal === signal, true);
       equal(init.credentials, "same-origin");
       equal(init.redirect, "error");
       equal(init.mode, "same-origin");
       equal(init.cache, "no-store");
-      equal(init.referrerPolicy, "no-referrer");
+      if (path !== "/api/auth/whoami") {
+        equal(init.referrerPolicy, "no-referrer");
+      }
       equal(new Headers(init.headers).has("authorization"), false);
     }
+    equal(requests[2].init.body, undefined);
     equal(JSON.parse(String(requests[0].init.body)), {
       handle: "alice",
       code: "synthetic-input-only",
@@ -125,9 +143,10 @@ Deno.test("activation sanitizes HTTP transport malformed and mismatched completi
           return Response.json({ unexpected: "synthetic-input-only" });
         }
         return Response.json(
-          String(input).endsWith("/options")
-            ? registrationOptions
-            : { user: { ...authUser, handle: "other" } },
+          String(input).endsWith("/options") ? registrationOptions : {
+            user: { ...authUser, handle: "other" },
+            authentication_reference: "fixture-authentication",
+          },
         );
       },
       async () => credentialFixture(),
@@ -173,3 +192,201 @@ Deno.test("activation invalid IDs and oversized code are rejected before network
     },
   );
 });
+
+for (
+  const mode of [
+    "anonymous",
+    "bob",
+    "account-mismatch",
+    "reference-mismatch",
+    "api-token",
+    "unavailable",
+  ] as const
+) {
+  Deno.test(
+    "activation rejects " + mode +
+      " whoami after successful completion without retry",
+    async () => {
+      const paths: string[] = [];
+      await boundary(
+        async (input) => {
+          const path = String(input);
+          paths.push(path);
+          if (path === "/api/auth/activation/options") {
+            return Response.json(registrationOptions);
+          }
+          if (path === "/api/auth/activation/complete") {
+            return Response.json({
+              user: authUser,
+              authentication_reference: "fixture-authentication",
+            });
+          }
+          if (path !== "/api/auth/whoami") {
+            throw new Error("Unexpected endpoint");
+          }
+          if (mode === "unavailable") {
+            return new Response("private whoami diagnostic", { status: 503 });
+          }
+          if (mode === "anonymous") {
+            return Response.json({
+              actor: null,
+              authentication_reference: null,
+              session: { kind: "anonymous" },
+            });
+          }
+          const confirmation = confirmedSession();
+          if (mode === "bob") {
+            confirmation.actor = {
+              ...confirmation.actor,
+              user_id: "user-bob",
+              account_id: "account-bob",
+              handle: "bob",
+              display_name: "Bob",
+            };
+          }
+          if (mode === "account-mismatch") {
+            confirmation.actor.account_id = "account-bob";
+          }
+          if (mode === "reference-mismatch") {
+            confirmation.authentication_reference = "another-authentication";
+          }
+          if (mode === "api-token") {
+            confirmation.actor.auth_method = "api_token";
+          }
+          return Response.json(confirmation);
+        },
+        async () => credentialFixture(),
+        async () => {
+          await rejects(
+            activateWithPasskey(
+              "alice",
+              "synthetic-input-only",
+              new AbortController().signal,
+            ),
+          );
+          equal(paths, [
+            "/api/auth/activation/options",
+            "/api/auth/activation/complete",
+            "/api/auth/whoami",
+          ]);
+        },
+      );
+    },
+  );
+}
+
+for (const stage of ["prompt", "completion", "confirmation"] as const) {
+  Deno.test(
+    "activation session generation change during " + stage +
+      " fences stale work",
+    async () => {
+      const paths: string[] = [];
+      await boundary(async (input) => {
+        const path = String(input);
+        paths.push(path);
+        if (path === "/api/auth/activation/options") {
+          return Response.json(registrationOptions);
+        }
+        if (path === "/api/auth/activation/complete") {
+          if (stage === "completion") browserSession.invalidate();
+          return Response.json({
+            user: authUser,
+            authentication_reference: "fixture-authentication",
+          });
+        }
+        if (path === "/api/auth/whoami") {
+          if (stage === "confirmation") browserSession.invalidate();
+          return Response.json(confirmedSession());
+        }
+        throw new Error("Unexpected endpoint");
+      }, async () => {
+        if (stage === "prompt") browserSession.invalidate();
+        return credentialFixture();
+      }, async () => {
+        await rejects(
+          activateWithPasskey(
+            "alice",
+            "synthetic-input-only",
+            new AbortController().signal,
+          ),
+        );
+        equal(paths, [
+          "/api/auth/activation/options",
+          ...(stage === "prompt" ? [] : ["/api/auth/activation/complete"]),
+          ...(stage === "confirmation" ? ["/api/auth/whoami"] : []),
+        ]);
+      });
+    },
+  );
+}
+
+for (
+  const phase of ["options", "prompt", "complete", "confirmation"] as const
+) {
+  for (const reason of ["logout", "authentication"] as const) {
+    Deno.test(`activation fences shared ${reason} stamp during ${phase} before event delivery`, async () => {
+      const previous = Object.getOwnPropertyDescriptor(
+        globalThis,
+        "localStorage",
+      );
+      let stamp = "initial-operation-stamp";
+      Object.defineProperty(globalThis, "localStorage", {
+        configurable: true,
+        value: { getItem: () => stamp },
+      });
+      const generation = browserSession.authenticationGeneration;
+      const paths: string[] = [];
+      try {
+        await boundary(async (input) => {
+          const path = String(input);
+          paths.push(path);
+          if (
+            (phase === "options" && path.endsWith("/options")) ||
+            (phase === "complete" && path.endsWith("/complete")) ||
+            (phase === "confirmation" && path === "/api/auth/whoami")
+          ) {
+            stamp = JSON.stringify({ id: "other-tab", reason });
+          }
+          return Response.json(
+            path.endsWith("/options")
+              ? registrationOptions
+              : path.endsWith("/complete")
+              ? {
+                user: authUser,
+                authentication_reference: "fixture-authentication",
+              }
+              : confirmedSession(),
+          );
+        }, async () => {
+          if (phase === "prompt") {
+            stamp = JSON.stringify({ id: "other-tab", reason });
+          }
+          return credentialFixture();
+        }, async () => {
+          await rejects(
+            activateWithPasskey(
+              "alice",
+              "synthetic-input-only",
+              new AbortController().signal,
+            ),
+          );
+          equal(browserSession.authenticationGeneration, generation);
+          equal(stamp === "initial-operation-stamp", false);
+          equal(
+            paths.filter((path) => path.endsWith("/complete")).length,
+            phase === "complete" || phase === "confirmation" ? 1 : 0,
+          );
+          equal(paths.includes("/api/auth/whoami"), phase === "confirmation");
+        });
+      } finally {
+        if (previous) {
+          Object.defineProperty(
+            globalThis,
+            "localStorage",
+            previous,
+          );
+        } else Reflect.deleteProperty(globalThis, "localStorage");
+      }
+    });
+  }
+}
diff --git a/web/workspace/src/lib/workspace/auth/activation.ts b/web/workspace/src/lib/workspace/auth/activation.ts
index 53a66b1c6..a17550fd9 100644
--- a/web/workspace/src/lib/workspace/auth/activation.ts
+++ b/web/workspace/src/lib/workspace/auth/activation.ts
@@ -2,7 +2,8 @@ import type {
   ActivationOptionsRequest,
   PasskeyRegistrationCompleteRequest,
 } from "#lib/generated/auth-api.ts";
-import { readBoundedAuthResponseJson } from "./api.ts";
+import { loadWhoami, readBoundedAuthResponseJson } from "./api.ts";
+import { browserSession } from "./session-state.ts";
 import { normalizeActivationHandle } from "./hosting-accounts.ts";
 import {
   type AuthUser,
@@ -19,6 +20,16 @@ export async function activateWithPasskey(
   code: string,
   signal: AbortSignal,
 ): Promise<AuthUser> {
+  const generation = browserSession.authenticationGeneration;
+  const stamp = browserSession.authenticationStamp;
+  // 別tabのstorage event配送より先にcredential/応答が返っても送信・適用しない。
+  const assertCurrent = () => {
+    signal.throwIfAborted();
+    if (
+      generation !== browserSession.authenticationGeneration ||
+      stamp !== browserSession.authenticationStamp
+    ) throw new Error("Activation superseded");
+  };
   try {
     handle = normalizeActivationHandle(handle);
     if (window.isSecureContext !== true || !code || code.length > 4096) {
@@ -28,7 +39,7 @@ export async function activateWithPasskey(
       path: "/api/auth/activation/options" | "/api/auth/activation/complete",
       body: ActivationOptionsRequest | PasskeyRegistrationCompleteRequest,
     ): Promise<unknown> => {
-      signal.throwIfAborted();
+      assertCurrent();
       const response = await fetch(path, {
         method: "POST",
         credentials: "same-origin",
@@ -44,7 +55,9 @@ export async function activateWithPasskey(
         await response.body?.cancel();
         throw new Error("Activation rejected");
       }
-      return await readBoundedAuthResponseJson(response);
+      const result = await readBoundedAuthResponseJson(response);
+      assertCurrent();
+      return result;
     };
     const options = await request("/api/auth/activation/options", {
       handle,
@@ -54,22 +67,33 @@ export async function activateWithPasskey(
     code = "";
     const publicKey = prepareRegistrationOptions(options);
     const challengeId = (options as { challenge_id: string }).challenge_id;
-    signal.throwIfAborted();
+    assertCurrent();
     const credential = await navigator.credentials.create({
       publicKey,
       signal,
     });
     if (!credential) throw new Error("Registration cancelled");
-    signal.throwIfAborted();
+    assertCurrent();
     const result = parseAuthUserResponse(
       await request("/api/auth/activation/complete", {
         challenge_id: challengeId,
         credential: registrationCredentialToJson(credential),
       }),
-    ).user;
-    signal.throwIfAborted();
-    if (result.handle !== handle) throw new Error("Activation target mismatch");
-    return result;
+    );
+    assertCurrent();
+    if (result.user.handle !== handle) {
+      throw new Error("Activation target mismatch");
+    }
+    const current = await loadWhoami(signal);
+    assertCurrent();
+    if (
+      current.session.kind !== "authenticated" ||
+      current.actor?.auth_method !== "browser_session" ||
+      current.actor.user_id !== result.user.user_id ||
+      current.actor.account_id !== result.user.account_id ||
+      current.authentication_reference !== result.authentication_reference
+    ) throw new Error("Activation session unconfirmed");
+    return result.user;
   } catch {
     // HTTP/WebAuthn/JSON例外はsecretを含む可能性があるため、本文も例外も転載しない。
     throw new Error("Activation could not be confirmed.");
diff --git a/web/workspace/src/lib/workspace/auth/api.test-fixtures.ts b/web/workspace/src/lib/workspace/auth/api.test-fixtures.ts
index 3cbac0ddf..d09c39ce1 100644
--- a/web/workspace/src/lib/workspace/auth/api.test-fixtures.ts
+++ b/web/workspace/src/lib/workspace/auth/api.test-fixtures.ts
@@ -67,6 +67,7 @@ export function credentialFixture(authentication = false): Credential {
 export function whoamiPayload(actor: unknown = null) {
   return {
     actor,
+    authentication_reference: actor === null ? null : "fixture-authentication",
     session: actor === null
       ? { kind: "anonymous" }
       : { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
diff --git a/web/workspace/src/lib/workspace/auth/api.ts b/web/workspace/src/lib/workspace/auth/api.ts
index 73678fed5..b953bae09 100644
--- a/web/workspace/src/lib/workspace/auth/api.ts
+++ b/web/workspace/src/lib/workspace/auth/api.ts
@@ -1,6 +1,7 @@
 import type {
   DeviceLoginApproveRequest,
   PasskeyAdditionOptionsRequest,
+  PasskeyAdditionResultRequest,
   PasskeyLoginCompleteRequest,
   PasskeyLoginOptionsRequest,
   PasskeyRegistrationCompleteRequest,
@@ -8,24 +9,38 @@ import type {
 } from "#lib/generated/auth-api.ts";
 import {
   authenticationCredentialToJson,
-  type AuthUser,
+  AuthPayloadError,
   type DeviceApprovalResponse,
+  parseAdditionResult,
   parseAuthUserResponse,
   parseDeviceApprovalResponse,
   parseLogoutResponse,
+  parsePasskeyList,
   parseWhoamiResponse,
+  type PasskeyUserResponse,
   prepareLoginOptions,
   prepareRegistrationOptions,
   registrationCredentialToJson,
   type WhoamiResponse,
 } from "#lib/workspace/auth/model.ts";
 
+import {
+  authCheckpoint,
+  AuthOperationError,
+  type AuthStage,
+  classifyAuthFailure,
+  expectedAuthSession,
+  recordAdditionAttempt,
+} from "./operation.ts";
+
 export class AuthRequestError extends Error {
-  constructor(readonly status: number) {
+  constructor(readonly status: number, readonly code: string | null = null) {
     super(`Auth request failed (${status}).`);
   }
 }
 
+class AuthResponseError extends Error {}
+
 const MAX_AUTH_RESPONSE_BYTES = 256 * 1024;
 
 export async function readBoundedAuthResponseJson(
@@ -39,13 +54,15 @@ export async function readBoundedAuthResponseJson(
       parsed > MAX_AUTH_RESPONSE_BYTES
     ) {
       await response.body?.cancel();
-      throw new Error(
+      throw new AuthResponseError(
         "Invalid auth response: response body exceeds the size limit.",
       );
     }
   }
   if (response.body === null) {
-    throw new Error("Invalid auth response: response body is missing.");
+    throw new AuthResponseError(
+      "Invalid auth response: response body is missing.",
+    );
   }
 
   const reader = response.body.getReader();
@@ -58,7 +75,7 @@ export async function readBoundedAuthResponseJson(
       totalBytes += value.byteLength;
       if (totalBytes > MAX_AUTH_RESPONSE_BYTES) {
         await reader.cancel();
-        throw new Error(
+        throw new AuthResponseError(
           "Invalid auth response: response body exceeds the size limit.",
         );
       }
@@ -79,7 +96,9 @@ export async function readBoundedAuthResponseJson(
       new TextDecoder("utf-8", { fatal: true }).decode(bytes),
     ) as unknown;
   } catch {
-    throw new Error("Invalid auth response: response body is not valid JSON.");
+    throw new AuthResponseError(
+      "Invalid auth response: response body is not valid JSON.",
+    );
   }
 }
 
@@ -96,8 +115,27 @@ async function requestJson(path: string, init?: RequestInit): Promise<unknown> {
     },
   });
   if (!response.ok) {
-    await response.body?.cancel();
-    throw new AuthRequestError(response.status);
+    let code: string | null = null;
+    try {
+      const value = await readBoundedAuthResponseJson(response);
+      const message = typeof value === "object" && value !== null
+        ? (value as { message?: unknown }).message
+        : null;
+      if (typeof message === "string") {
+        code = [
+          "auth_required",
+          "passkey_authentication_changed",
+          "passkey_registration_binding_mismatch",
+          "webauthn_registration_verification_failed",
+          "webauthn_login_verification_failed",
+          "invalid_passkey_challenge",
+          "expired_passkey_challenge",
+          "self_registration_disabled",
+          "passkey_activation_required",
+        ].find((code) => message.startsWith(code + ":")) ?? null;
+      }
+    } catch { /* 本文・解析例外は保存しない。statusだけでも失敗として扱う。 */ }
+    throw new AuthRequestError(response.status, code);
   }
   return await readBoundedAuthResponseJson(response);
 }
@@ -122,7 +160,7 @@ export async function registerPasskey(
   handle: string,
   displayName?: string,
   signal?: AbortSignal,
-): Promise<AuthUser> {
+): Promise<PasskeyUserResponse> {
   const optionsRequest: PasskeyRegistrationOptionsRequest = {
     handle,
     display_name: displayName ?? null,
@@ -131,8 +169,21 @@ export async function registerPasskey(
   return await createPasskey("registration", optionsRequest, signal);
 }
 
-export async function addPasskey(signal?: AbortSignal): Promise<AuthUser> {
+export async function addPasskey(
+  signal?: AbortSignal,
+): Promise<PasskeyUserResponse> {
+  const expected = expectedAuthSession(signal) ?? await loadWhoami(signal);
+  if (!expected.actor || !expected.authentication_reference) {
+    throw new AuthOperationError(
+      "session-check",
+      "session-changed",
+      "not-sent",
+    );
+  }
   const optionsRequest: PasskeyAdditionOptionsRequest = {
+    expected_user_id: expected.actor.user_id,
+    expected_account_id: expected.actor.account_id,
+    expected_authentication_reference: expected.authentication_reference,
     browser_origin: window.location.origin,
   };
   return await createPasskey("addition", optionsRequest, signal);
@@ -144,51 +195,88 @@ async function createPasskey(
     | PasskeyRegistrationOptionsRequest
     | PasskeyAdditionOptionsRequest,
   signal?: AbortSignal,
-): Promise<AuthUser> {
-  const options = await requestJson(`/api/auth/passkeys/${purpose}/options`, {
-    method: "POST",
-    body: JSON.stringify(optionsRequest),
-    signal,
-  });
-  const optionsRecord = typeof options === "object" && options !== null
-    ? options as Record<string, unknown>
-    : null;
-  const challengeId = optionsRecord?.challenge_id;
-  if (typeof challengeId !== "string" || challengeId.length === 0) {
-    throw new Error(
-      "Invalid auth payload: registration_options.challenge_id is required.",
-    );
-  }
-  signal?.throwIfAborted();
-  if (typeof navigator.credentials?.create !== "function") {
-    throw new DOMException("Passkeys unavailable", "NotSupportedError");
-  }
-  const credential = await navigator.credentials.create({
-    signal,
-    publicKey: prepareRegistrationOptions(options),
-  });
-  if (!credential) {
-    throw new DOMException("Passkey cancelled", "NotAllowedError");
-  }
-
-  signal?.throwIfAborted();
-  const completeRequest: PasskeyRegistrationCompleteRequest = {
-    challenge_id: challengeId,
-    credential: registrationCredentialToJson(credential),
-  };
-  const result = parseAuthUserResponse(
-    await requestJson(`/api/auth/passkeys/${purpose}/complete`, {
+): Promise<PasskeyUserResponse> {
+  let stage: AuthStage = "options";
+  let sent = false;
+  try {
+    await authCheckpoint(signal, stage);
+    const options = await requestJson(`/api/auth/passkeys/${purpose}/options`, {
       method: "POST",
-      body: JSON.stringify(completeRequest),
+      body: JSON.stringify(optionsRequest),
       signal,
-    }),
-  );
-  return result.user;
+    });
+    const publicKey = prepareRegistrationOptions(options);
+    const challengeId = (options as { challenge_id: string }).challenge_id;
+    stage = "authenticator";
+    await authCheckpoint(signal, stage);
+    if (typeof navigator.credentials?.create !== "function") {
+      throw new DOMException("", "NotSupportedError");
+    }
+    const credential = await navigator.credentials.create({
+      signal,
+      publicKey,
+    });
+    if (!credential) throw new DOMException("", "NotAllowedError");
+    signal?.throwIfAborted();
+    stage = "conversion";
+    await authCheckpoint(signal, stage);
+    const completeRequest: PasskeyRegistrationCompleteRequest = {
+      challenge_id: challengeId,
+      credential: registrationCredentialToJson(credential),
+    };
+    stage = "before-complete";
+    await authCheckpoint(signal, stage);
+    stage = "complete";
+    await authCheckpoint(signal, stage);
+    if (purpose === "addition") {
+      const expected = optionsRequest as PasskeyAdditionOptionsRequest;
+      recordAdditionAttempt(signal, {
+        challenge_id: challengeId,
+        expected_user_id: expected.expected_user_id,
+        expected_account_id: expected.expected_account_id,
+        expected_authentication_reference:
+          expected.expected_authentication_reference,
+      });
+    }
+    sent = true;
+    const result = parseAuthUserResponse(
+      await requestJson(`/api/auth/passkeys/${purpose}/complete`, {
+        method: "POST",
+        body: JSON.stringify(completeRequest),
+        signal,
+      }),
+    );
+    signal?.throwIfAborted();
+    return result;
+  } catch (error) {
+    if (error instanceof AuthRequestError) {
+      throw new AuthOperationError(
+        stage,
+        error.code === "auth_required" ||
+          error.code === "passkey_authentication_changed" ||
+          error.code === "passkey_registration_binding_mismatch"
+          ? "session-changed"
+          : "rejected",
+        sent ? error.status >= 500 ? "unknown" : "rejected" : "not-sent",
+        error.status,
+      );
+    }
+    if (
+      error instanceof AuthResponseError || error instanceof AuthPayloadError
+    ) {
+      throw new AuthOperationError(
+        stage,
+        stage === "conversion" ? "conversion" : "invalid-response",
+        sent ? "unknown" : "not-sent",
+      );
+    }
+    throw classifyAuthFailure(error, stage, sent);
+  }
 }
 
 export async function loginWithPasskey(
   signal?: AbortSignal,
-): Promise<AuthUser> {
+): Promise<PasskeyUserResponse> {
   return await authenticateWithPasskey({
     browser_origin: window.location.origin,
   }, signal);
@@ -197,7 +285,7 @@ export async function loginWithPasskey(
 export async function loginWithLegacyPasskey(
   handle: string,
   signal?: AbortSignal,
-): Promise<AuthUser> {
+): Promise<PasskeyUserResponse> {
   const loginHandle = handle.trim();
   if (!loginHandle) {
     throw new Error("User handle is required for legacy passkey login.");
@@ -211,52 +299,77 @@ export async function loginWithLegacyPasskey(
 async function authenticateWithPasskey(
   optionsRequest: PasskeyLoginOptionsRequest,
   signal?: AbortSignal,
-): Promise<AuthUser> {
-  const options = await requestJson("/api/auth/passkeys/login/options", {
-    method: "POST",
-    body: JSON.stringify(optionsRequest),
-    signal,
-  });
-  const optionsRecord = typeof options === "object" && options !== null
-    ? options as Record<string, unknown>
-    : null;
-  const challengeId = optionsRecord?.challenge_id;
-  if (typeof challengeId !== "string" || challengeId.length === 0) {
-    throw new Error(
-      "Invalid auth payload: login_options.challenge_id is required.",
-    );
-  }
-  signal?.throwIfAborted();
-  if (typeof navigator.credentials?.get !== "function") {
-    throw new DOMException("Passkeys unavailable", "NotSupportedError");
-  }
-  const credential = await navigator.credentials.get({
-    signal,
-    publicKey: prepareLoginOptions(options),
-  });
-  if (!credential) {
-    throw new DOMException("Passkey cancelled", "NotAllowedError");
-  }
-
-  signal?.throwIfAborted();
-  const completeRequest: PasskeyLoginCompleteRequest = {
-    challenge_id: challengeId,
-    credential: authenticationCredentialToJson(credential),
-  };
-  const result = parseAuthUserResponse(
-    await requestJson("/api/auth/passkeys/login/complete", {
+): Promise<PasskeyUserResponse> {
+  let stage: AuthStage = "options";
+  let sent = false;
+  try {
+    await authCheckpoint(signal, stage);
+    const options = await requestJson("/api/auth/passkeys/login/options", {
       method: "POST",
-      body: JSON.stringify(completeRequest),
+      body: JSON.stringify(optionsRequest),
       signal,
-    }),
-  );
-  return result.user;
+    });
+    const publicKey = prepareLoginOptions(options);
+    const challengeId = (options as { challenge_id: string }).challenge_id;
+    stage = "authenticator";
+    await authCheckpoint(signal, stage);
+    if (typeof navigator.credentials?.get !== "function") {
+      throw new DOMException("", "NotSupportedError");
+    }
+    const credential = await navigator.credentials.get({ signal, publicKey });
+    if (!credential) throw new DOMException("", "NotAllowedError");
+    signal?.throwIfAborted();
+    stage = "conversion";
+    await authCheckpoint(signal, stage);
+    const completeRequest: PasskeyLoginCompleteRequest = {
+      challenge_id: challengeId,
+      credential: authenticationCredentialToJson(credential),
+    };
+    stage = "before-complete";
+    await authCheckpoint(signal, stage);
+    stage = "complete";
+    await authCheckpoint(signal, stage);
+    sent = true;
+    const result = parseAuthUserResponse(
+      await requestJson("/api/auth/passkeys/login/complete", {
+        method: "POST",
+        body: JSON.stringify(completeRequest),
+        signal,
+      }),
+    );
+    signal?.throwIfAborted();
+    return result;
+  } catch (error) {
+    if (error instanceof AuthRequestError) {
+      throw new AuthOperationError(
+        stage,
+        error.code === "auth_required" ||
+          error.code === "passkey_authentication_changed" ||
+          error.code === "passkey_registration_binding_mismatch"
+          ? "session-changed"
+          : "rejected",
+        sent ? error.status >= 500 ? "unknown" : "rejected" : "not-sent",
+        error.status,
+      );
+    }
+    if (
+      error instanceof AuthResponseError || error instanceof AuthPayloadError
+    ) {
+      throw new AuthOperationError(
+        stage,
+        stage === "conversion" ? "conversion" : "invalid-response",
+        sent ? "unknown" : "not-sent",
+      );
+    }
+    throw classifyAuthFailure(error, stage, sent);
+  }
 }
 
 export async function approveDeviceLogin(
   userCode: string,
   signal?: AbortSignal,
 ): Promise<DeviceApprovalResponse> {
+  await authCheckpoint(signal, "before-complete");
   const request: DeviceLoginApproveRequest = { user_code: userCode };
   return parseDeviceApprovalResponse(
     await requestJson("/api/auth/device-login/approve", {
@@ -266,3 +379,19 @@ export async function approveDeviceLogin(
     }),
   );
 }
+
+export async function loadPasskeys(signal?: AbortSignal) {
+  return parsePasskeyList(await requestJson("/api/auth/passkeys", { signal }));
+}
+export async function readAdditionResult(
+  request: PasskeyAdditionResultRequest,
+  signal?: AbortSignal,
+) {
+  return parseAdditionResult(
+    await requestJson("/api/auth/passkeys/addition/result", {
+      method: "POST",
+      body: JSON.stringify(request),
+      signal,
+    }),
+  );
+}
diff --git a/web/workspace/src/lib/workspace/auth/browser-session.svelte.ts b/web/workspace/src/lib/workspace/auth/browser-session.svelte.ts
index 9adc8e0cc..e11a9a980 100644
--- a/web/workspace/src/lib/workspace/auth/browser-session.svelte.ts
+++ b/web/workspace/src/lib/workspace/auth/browser-session.svelte.ts
@@ -1,11 +1,18 @@
-import { AuthRequestError } from "./api.ts";
+import type { PasskeyAdditionResultRequest } from "#lib/generated/auth-api.ts";
+import { AuthRequestError, loadWhoami, readAdditionResult } from "./api.ts";
 import {
   browserSession,
   observeBrowserSession,
   sessionMutation,
 } from "./session-state.ts";
 import { notifySessionChanged } from "./hosting.ts";
-import type { RequestActor, WhoamiResponse } from "./model.ts";
+import type { AuthUser, RequestActor, WhoamiResponse } from "./model.ts";
+import {
+  AuthOperationError,
+  type AuthStage,
+  observeAuthOperation,
+  operationErrorMessage,
+} from "./operation.ts";
 
 export type BrowserSession =
   | { kind: "loading" }
@@ -13,41 +20,60 @@ export type BrowserSession =
   | ({ kind: "ready" } & WhoamiResponse);
 
 export function authErrorMessage(error: unknown): string {
+  if (error instanceof AuthOperationError) return operationErrorMessage(error);
   if (error instanceof AuthRequestError) {
-    if (error.status === 401) {
-      return "Authentication request was rejected. Check your session or restart the Passkey operation.";
-    }
-    if (error.status === 400 || error.status === 410) {
-      return "The request or authentication challenge is invalid or expired. Restart the operation.";
-    }
-    return error.message;
+    return `Authentication request was rejected (${error.status}). Check your session or restart the operation.`;
   }
-  if (error instanceof DOMException && error.name === "NotSupportedError") {
-    return "This browser or key cannot complete this passkey operation. Use a supported device or key with saved passkeys and PIN or biometric verification. Completion is not confirmed.";
-  }
-  if (error instanceof DOMException && error.name === "NotAllowedError") {
-    return "Passkey operation was cancelled or timed out, or no matching key was found. Completion is not confirmed. Use a supported device and try again.";
-  }
-  if (error instanceof DOMException && error.name === "AbortError") {
-    return "Operation stopped. Completion is not confirmed; check your session before retrying.";
-  }
-  // Browser/transport例外の本文を表示せず、credentialや外部応答を診断へ複写しない。
-  return "Authentication could not be confirmed. Check your session before retrying the operation.";
+  // 例外本文/causeや外部応答は表示にも診断にも複写しない。
+  return "Authentication could not be confirmed. Check your session and the operation result before retrying.";
+}
+function sameUser(a: AuthUser | null, b: AuthUser | null): boolean {
+  return a === null
+    ? b === null
+    : b !== null && a.user_id === b.user_id && a.account_id === b.account_id;
+}
+function sameSession(a: WhoamiResponse, b: WhoamiResponse): boolean {
+  // anonymous/expiredはいずれも認証主体もbindingもない。別tabのlogoutでexpiredの
+  // 表示だけが古くなっても、新たな明示loginを拒否しない。認証済みへの変化は拒否する。
+  if (
+    !a.actor && !b.actor && a.session.kind !== "authenticated" &&
+    b.session.kind !== "authenticated"
+  ) return true;
+  return sameUser(a.actor, b.actor) && a.session.kind === b.session.kind &&
+    (a.session.kind !== "authenticated" ||
+      a.authentication_reference === b.authentication_reference &&
+        b.session.kind === "authenticated" &&
+        a.session.expires_at === b.session.expires_at &&
+        a.actor?.auth_method === b.actor?.auth_method);
+}
+function returnedUser(value: unknown): AuthUser | null {
+  if (typeof value !== "object" || value === null) return null;
+  const user = (value as { user?: Partial<AuthUser> }).user;
+  return user && typeof user.user_id === "string" &&
+      typeof user.account_id === "string" && typeof user.handle === "string" &&
+      typeof user.display_name === "string"
+    ? user as AuthUser
+    : null;
 }
-
 export class BrowserAuth {
   session = $state<BrowserSession>({ kind: "loading" });
   busy = $state(false);
   error = $state("");
   status = $state("");
+  additionAttempt = $state<PasskeyAdditionResultRequest | null>(null);
+  additionSaved = $state(false);
   private unsubscribe: () => void;
   private disposed = false;
   private controller: AbortController | null = null;
+  private operationGeneration: number | null = null;
 
   constructor() {
     observeBrowserSession();
     this.unsubscribe = browserSession.subscribe((snapshot) => {
-      // 操作pendingはsession確認中と別。formを消してfocus/入力を失わず、busyで再操作を止める。
+      if (
+        this.operationGeneration !== null &&
+        this.operationGeneration !== browserSession.authenticationGeneration
+      ) this.controller?.abort();
       if (this.busy && snapshot.kind === "loading") return;
       if (!this.disposed) {
         this.session = snapshot.kind === "ready"
@@ -56,75 +82,239 @@ export class BrowserAuth {
       }
     });
   }
-
   get actor(): RequestActor | null {
     return this.session.kind === "ready" ? this.session.actor : null;
   }
-
   async ensure(): Promise<void> {
-    if (this.busy || this.disposed) return;
-    await browserSession.ensure();
+    if (!this.busy && !this.disposed) await browserSession.ensure();
   }
-
   async refresh(): Promise<void> {
-    if (this.busy || this.disposed) return;
-    await browserSession.refresh();
+    if (!this.busy && !this.disposed) await browserSession.refresh();
+  }
+  cancel(): void {
+    this.controller?.abort();
   }
-
   async run(
     pending: string,
     success: string,
     operation: (signal: AbortSignal) => Promise<unknown>,
-    intent: "authentication" | "logout" = "authentication",
+    intent: "authentication" | "logout" | "device-approval" = "authentication",
   ): Promise<boolean> {
     if (
       this.busy || this.disposed ||
       (intent !== "logout" && this.session.kind !== "ready")
-    ) {
-      return false;
-    }
+    ) return false;
+    const mutationReason = intent === "logout" ? "logout" : "authentication";
+    const expected = this.session.kind === "ready" ? this.session : null;
     this.busy = true;
-    sessionMutation(intent);
-    const authenticationGeneration = browserSession.authenticationGeneration;
+    sessionMutation(mutationReason, true);
+    const generation = browserSession.authenticationGeneration;
+    const stamp = browserSession.authenticationStamp;
+    let acceptedGeneration = generation;
+    let acceptedStamp = stamp;
+    let submittedAddition = false;
     const controller = new AbortController();
     this.controller = controller;
+    this.operationGeneration = generation;
     this.error = "";
     this.status = pending;
+    const verifySession = async () => {
+      if (stamp !== browserSession.authenticationStamp) controller.abort();
+      controller.signal.throwIfAborted();
+      let current: WhoamiResponse;
+      try {
+        current = await loadWhoami(controller.signal);
+      } catch {
+        throw new AuthOperationError(
+          "session-check",
+          "session-changed",
+          "not-sent",
+        );
+      }
+      if (stamp !== browserSession.authenticationStamp) controller.abort();
+      controller.signal.throwIfAborted();
+      if (!expected || !sameSession(expected, current)) {
+        throw new AuthOperationError(
+          "session-check",
+          "session-changed",
+          "not-sent",
+        );
+      }
+    };
+    observeAuthOperation(controller.signal, {
+      verifySession,
+      expected,
+      additionAttempt: (attempt) => {
+        submittedAddition = true;
+        this.additionAttempt = attempt;
+        this.additionSaved = false;
+      },
+      phase: (stage: AuthStage) => {
+        if (!this.disposed) {
+          this.status = stage === "authenticator"
+            ? pending
+            : stage === "complete"
+            ? "Confirming the operation with the server…"
+            : stage === "before-complete"
+            ? "Checking the account before completion…"
+            : stage === "options"
+            ? "Checking the account and requesting passkey options…"
+            : "Preparing the authenticator response…";
+        }
+      },
+    });
     try {
-      await operation(controller.signal);
-      const superseded =
-        authenticationGeneration !== browserSession.authenticationGeneration;
-      sessionMutation(intent);
+      if (intent === "device-approval") await verifySession();
+      const result = await operation(controller.signal);
+      const user = returnedUser(result);
+      const issuedReference = typeof result === "object" && result !== null
+        ? (result as { authentication_reference?: unknown })
+          .authentication_reference
+        : null;
+      controller.signal.throwIfAborted();
+      if (
+        this.disposed ||
+        generation !== browserSession.authenticationGeneration ||
+        stamp !== browserSession.authenticationStamp
+      ) return false;
+      // 自身の再確認によるinvalidateと、他の操作が行ったinvalidateを混同しない。
+      this.operationGeneration = null;
+      sessionMutation(mutationReason, true);
       const confirmationGeneration = browserSession.authenticationGeneration;
+      acceptedGeneration = confirmationGeneration;
+      const confirmationStamp = browserSession.authenticationStamp;
+      acceptedStamp = confirmationStamp;
+      this.status = "Confirming the expected browser session…";
       await browserSession.refresh();
       if (
-        this.disposed || superseded ||
-        confirmationGeneration !== browserSession.authenticationGeneration
+        this.disposed || controller.signal.aborted ||
+        confirmationGeneration !== browserSession.authenticationGeneration ||
+        confirmationStamp !== browserSession.authenticationStamp
       ) {
         if (!this.disposed) this.status = "";
         return false;
       }
+      const snapshot = browserSession.snapshot;
+      const confirmed = snapshot.kind === "ready" &&
+        (intent === "logout"
+          ? snapshot.value.actor === null &&
+            snapshot.value.session.kind !== "authenticated"
+          : intent === "device-approval"
+          ? snapshot.value.session.kind === "authenticated" && user !== null &&
+            sameUser(user, expected?.actor ?? null) &&
+            sameUser(user, snapshot.value.actor) &&
+            snapshot.value.authentication_reference ===
+              expected?.authentication_reference &&
+            typeof result === "object" && result !== null &&
+            (result as { status?: unknown }).status === "approved"
+          : snapshot.value.session.kind === "authenticated" &&
+            snapshot.value.actor?.auth_method === "browser_session" &&
+            user !== null && typeof issuedReference === "string" &&
+            issuedReference === snapshot.value.authentication_reference &&
+            sameUser(user, snapshot.value.actor) &&
+            (!expected?.actor || sameUser(expected.actor, user)));
+      if (!confirmed) {
+        throw new AuthOperationError(
+          "confirmation",
+          "session-changed",
+          "saved-session-unconfirmed",
+        );
+      }
       notifySessionChanged();
-      const confirmed = this.session.kind === "ready";
-      this.status = confirmed ? success : "";
-      return confirmed;
+      if (submittedAddition) this.additionSaved = true;
+      this.status = success;
+      return true;
     } catch (error) {
       if (!this.disposed) {
         this.error = authErrorMessage(error);
         this.status = "";
       }
-      // 失効/応答不明でも既存actorを操作権限として保持せず、正本を読み直す。
-      sessionMutation(intent);
-      await browserSession.refresh();
+      // 古い処理から新しいログアウト/主体確認をinvalidateしない。
+      if (
+        !this.disposed &&
+        acceptedGeneration === browserSession.authenticationGeneration &&
+        acceptedStamp === browserSession.authenticationStamp
+      ) {
+        this.operationGeneration = null;
+        sessionMutation(mutationReason, true);
+        await browserSession.refresh();
+      }
       return false;
     } finally {
+      this.operationGeneration = null;
+      this.controller = null;
+      if (!this.disposed) this.busy = false;
+    }
+  }
+  async checkAddition(): Promise<void> {
+    const attempt = this.additionAttempt;
+    if (!attempt || this.busy || this.disposed) return;
+    this.busy = true;
+    this.error = "";
+    this.status = "Checking the saved addition result…";
+    // 保存の履歴は失敗に戻さないが、過去の照合で再追加を許可しない。
+    this.additionSaved = false;
+    const generation = browserSession.authenticationGeneration;
+    const stamp = browserSession.authenticationStamp;
+    const controller = new AbortController();
+    this.controller = controller;
+    this.operationGeneration = generation;
+    const assertCurrent = () => {
+      controller.signal.throwIfAborted();
+      if (
+        this.disposed ||
+        generation !== browserSession.authenticationGeneration ||
+        stamp !== browserSession.authenticationStamp
+      ) {
+        throw new AuthOperationError(
+          "confirmation",
+          "session-changed",
+          "unknown",
+        );
+      }
+    };
+    try {
+      const before = await loadWhoami(controller.signal);
+      assertCurrent();
+      if (
+        !before.actor || before.actor.user_id !== attempt.expected_user_id ||
+        before.actor.account_id !== attempt.expected_account_id
+      ) {
+        throw new AuthOperationError(
+          "confirmation",
+          "session-changed",
+          "unknown",
+        );
+      }
+      const result = await readAdditionResult(attempt, controller.signal);
+      assertCurrent();
+      const after = await loadWhoami(controller.signal);
+      assertCurrent();
+      if (!sameSession(before, after)) {
+        throw new AuthOperationError(
+          "confirmation",
+          "session-changed",
+          "unknown",
+        );
+      }
+      if (result.status === "saved" && sameUser(result.user, before.actor)) {
+        this.additionSaved = true;
+        this.status =
+          "This addition saved a key to your account. Your current session was checked; the session issued by completion is not confirmed. Test ID-free login with that key before retiring older-key access.";
+      } else {this.status =
+          "The addition result is still unknown. Completion may still be in flight. Do not add another key yet; check again or use the registered-key list and ID-free login to verify access.";}
+    } catch {
       if (!this.disposed) {
-        this.busy = false;
-        this.controller = null;
+        this.error =
+          "The addition result could not be read with the current account/session. This does not prove failure. Return to the intended account and check its key list or ID-free login; do not recreate the original session or add blindly.";
+        this.status = "";
       }
+    } finally {
+      this.operationGeneration = null;
+      this.controller = null;
+      if (!this.disposed) this.busy = false;
     }
   }
-
   dispose(): void {
     this.disposed = true;
     this.unsubscribe();
diff --git a/web/workspace/src/lib/workspace/auth/hosting-accounts.ts b/web/workspace/src/lib/workspace/auth/hosting-accounts.ts
index ac8cb6713..f4280878f 100644
--- a/web/workspace/src/lib/workspace/auth/hosting-accounts.ts
+++ b/web/workspace/src/lib/workspace/auth/hosting-accounts.ts
@@ -1,7 +1,7 @@
 import type { ActivationCodeResponse } from "#lib/generated/auth-api.ts";
 import { readBoundedAuthResponseJson } from "./api.ts";
 import { HostingRequestError } from "./hosting.ts";
-import { parseAuthUserResponse } from "./model.ts";
+import { parseAuthUser } from "./model.ts";
 
 // Serverのnormalize_handleと同じASCII正規化。Unicode case foldingはしない。
 export function normalizeActivationHandle(value: string): string {
@@ -57,7 +57,7 @@ export async function issueActivationCode(
       typeof record.expires_at !== "string" ||
       !Number.isFinite(Date.parse(record.expires_at))
     ) throw new Error();
-    const user = parseAuthUserResponse({ user: record.user }).user;
+    const user = parseAuthUser(record.user);
     if (user.handle !== handle) throw new Error();
     signal.throwIfAborted();
     return { user, code: record.code, expires_at: record.expires_at };
diff --git a/web/workspace/src/lib/workspace/auth/hosting-enrollment.test.ts b/web/workspace/src/lib/workspace/auth/hosting-enrollment.test.ts
index b4810aae2..b166f8013 100644
--- a/web/workspace/src/lib/workspace/auth/hosting-enrollment.test.ts
+++ b/web/workspace/src/lib/workspace/auth/hosting-enrollment.test.ts
@@ -7,6 +7,16 @@ import {
   registrationOptions,
 } from "./api.test-fixtures.ts";
 
+const bearerIdentity = {
+  actor: { ...authUser, auth_method: "api_token" },
+  authentication_reference: "fixture-bearer-authentication",
+  session: { kind: "authenticated", expires_at: null },
+};
+const completion = {
+  user: authUser,
+  authentication_reference: "fixture-issued-authentication",
+};
+
 function equal(actual: unknown, expected: unknown): void {
   if (JSON.stringify(actual) !== JSON.stringify(expected)) {
     throw new Error("Values differ");
@@ -65,9 +75,11 @@ Deno.test("host enrollment sends bearer only to same-origin addition endpoints,
   await boundary(async (input, init) => {
     requests.push({ path: String(input), init: init! });
     return Response.json(
-      String(input).endsWith("/options")
+      String(input).endsWith("/whoami")
+        ? bearerIdentity
+        : String(input).endsWith("/options")
         ? registrationOptions
-        : { user: authUser },
+        : completion,
     );
   }, async () => {
     equal(
@@ -75,11 +87,13 @@ Deno.test("host enrollment sends bearer only to same-origin addition endpoints,
       authUser,
     );
     equal(requests.map((request) => request.path), [
+      "/api/auth/whoami",
       "/api/auth/passkeys/addition/options",
       "/api/auth/passkeys/addition/complete",
     ]);
-    for (const { init } of requests) {
-      equal(init.method, "POST");
+    for (const { path, init } of requests) {
+      equal(init.method, path.endsWith("/whoami") ? "GET" : "POST");
+      equal(new Headers(init.headers).has("cookie"), false);
       equal(init.credentials, "omit");
       equal(init.mode, "same-origin");
       equal(init.redirect, "error");
@@ -91,10 +105,15 @@ Deno.test("host enrollment sends bearer only to same-origin addition endpoints,
       );
       equal(String(init.body).includes("host-test-token"), false);
     }
-    equal(JSON.parse(String(requests[0].init.body)), {
+    equal(requests[0].init.body, undefined);
+    equal(JSON.parse(String(requests[1].init.body)), {
+      expected_user_id: authUser.user_id,
+      expected_account_id: authUser.account_id,
+      expected_authentication_reference:
+        bearerIdentity.authentication_reference,
       browser_origin: "https://yoi.example",
     });
-    const complete = JSON.parse(String(requests[1].init.body));
+    const complete = JSON.parse(String(requests[2].init.body));
     equal(Object.keys(complete).sort(), ["challenge_id", "credential"]);
     equal(complete.challenge_id, registrationOptions.challenge_id);
     equal(complete.credential.response.attestationObject, "AQID");
@@ -151,29 +170,46 @@ Deno.test("host enrollment validates options before opening credential prompt",
     }]
   ) {
     let calls = 0;
-    await boundary(async () => Response.json(payload), async () => {
-      await rejects(
-        enrollHostingPasskey("host-test-token", new AbortController().signal),
-      );
-      equal(calls, 0);
-    }, async () => {
-      calls++;
-      return credentialFixture();
-    });
+    await boundary(
+      async (input) =>
+        Response.json(
+          String(input).endsWith("/whoami") ? bearerIdentity : payload,
+        ),
+      async () => {
+        await rejects(
+          enrollHostingPasskey("host-test-token", new AbortController().signal),
+        );
+        equal(calls, 0);
+      },
+      async () => {
+        calls++;
+        return credentialFixture();
+      },
+    );
   }
 });
 
 Deno.test("host enrollment cancellation and teardown prevent completion", async () => {
   for (const abort of [false, true]) {
     const controller = new AbortController();
-    let requests = 0;
-    await boundary(async () => {
-      requests++;
-      return Response.json(registrationOptions);
+    const requests: string[] = [];
+    let prompts = 0;
+    await boundary(async (input) => {
+      requests.push(String(input));
+      return Response.json(
+        String(input).endsWith("/whoami")
+          ? bearerIdentity
+          : registrationOptions,
+      );
     }, async () => {
       await rejects(enrollHostingPasskey("host-test-token", controller.signal));
-      equal(requests, 1);
+      equal(requests, [
+        "/api/auth/whoami",
+        "/api/auth/passkeys/addition/options",
+      ]);
+      equal(prompts, 1);
     }, async () => {
+      prompts++;
       if (abort) {
         controller.abort();
         return credentialFixture();
@@ -188,6 +224,9 @@ Deno.test("host enrollment cannot confirm a rejected, lost or malformed completi
     let calls = 0;
     await boundary(async (input) => {
       calls++;
+      if (String(input).endsWith("/whoami")) {
+        return Response.json(bearerIdentity);
+      }
       if (String(input).endsWith("/options")) {
         return Response.json(registrationOptions);
       }
@@ -201,7 +240,7 @@ Deno.test("host enrollment cannot confirm a rejected, lost or malformed completi
       await rejects(
         enrollHostingPasskey("host-test-token", new AbortController().signal),
       );
-      equal(calls, 2);
+      equal(calls, 3);
     });
   }
 });
diff --git a/web/workspace/src/lib/workspace/auth/hosting-enrollment.ts b/web/workspace/src/lib/workspace/auth/hosting-enrollment.ts
index 4983bcaba..2fd7f624d 100644
--- a/web/workspace/src/lib/workspace/auth/hosting-enrollment.ts
+++ b/web/workspace/src/lib/workspace/auth/hosting-enrollment.ts
@@ -6,6 +6,7 @@ import { readBoundedAuthResponseJson } from "./api.ts";
 import {
   type AuthUser,
   parseAuthUserResponse,
+  parseWhoamiResponse,
   prepareRegistrationOptions,
   registrationCredentialToJson,
 } from "./model.ts";
@@ -26,13 +27,14 @@ export async function enrollHostingPasskey(
     }
     const request = async (
       path:
+        | "/api/auth/whoami"
         | "/api/auth/passkeys/addition/options"
         | "/api/auth/passkeys/addition/complete",
-      body: PasskeyAdditionOptionsRequest | PasskeyRegistrationCompleteRequest,
+      body?: PasskeyAdditionOptionsRequest | PasskeyRegistrationCompleteRequest,
     ): Promise<unknown> => {
       signal.throwIfAborted();
       const response = await fetch(path, {
-        method: "POST",
+        method: path === "/api/auth/whoami" ? "GET" : "POST",
         // Bearerの失効を既存cookieで補わない。設定用tokenだけで本人を決め、
         // completionのcookieも受け取らず、次の明示Passkey loginでsessionを作る。
         credentials: "omit",
@@ -53,7 +55,12 @@ export async function enrollHostingPasskey(
       }
       return await readBoundedAuthResponseJson(response);
     };
+    const identity = parseWhoamiResponse(await request("/api/auth/whoami"));
+    if (!identity.actor || !identity.authentication_reference || identity.actor.auth_method !== "api_token") throw new Error("Setup identity unconfirmed");
     const options = await request("/api/auth/passkeys/addition/options", {
+      expected_user_id: identity.actor.user_id,
+      expected_account_id: identity.actor.account_id,
+      expected_authentication_reference: identity.authentication_reference,
       browser_origin: window.location.origin,
     });
     const publicKey = prepareRegistrationOptions(options);
diff --git a/web/workspace/src/lib/workspace/auth/login.test.ts b/web/workspace/src/lib/workspace/auth/login.test.ts
index 7b6356d2f..88cd06cfa 100644
--- a/web/workspace/src/lib/workspace/auth/login.test.ts
+++ b/web/workspace/src/lib/workspace/auth/login.test.ts
@@ -4,6 +4,7 @@ declare const Deno: {
   test(name: string, fn: () => void | Promise<void>): void;
 };
 
+import { AuthOperationError } from "./operation.ts";
 import { loginWithLegacyPasskey, loginWithPasskey } from "./api.ts";
 import {
   authUser,
@@ -64,7 +65,12 @@ async function boundary(
             Response.json(body.handle ? legacyLoginOptions : loginOptions),
           );
         }
-        return Promise.resolve(Response.json({ user: authUser }));
+        return Promise.resolve(
+          Response.json({
+            user: authUser,
+            authentication_reference: "fixture-authentication",
+          }),
+        );
       },
     },
   });
@@ -97,7 +103,7 @@ for (const legacy of [false, true]) {
         await (legacy
           ? loginWithLegacyPasskey(" alice ", signal)
           : loginWithPasskey(signal)),
-        authUser,
+        { user: authUser, authentication_reference: "fixture-authentication" },
       );
       equal(state.requests.map(({ path }) => path), [
         "/api/auth/passkeys/login/options",
@@ -131,8 +137,10 @@ for (const legacy of [false, true]) {
             : loginWithPasskey(controller.signal));
           throw new Error("Unexpected login success");
         } catch (error) {
-          if (!(error instanceof DOMException)) throw error;
-          equal(error.name, late ? "AbortError" : "NotAllowedError");
+          if (!(error instanceof AuthOperationError)) throw error;
+          equal(error.stage, "authenticator");
+          equal(error.reason, late ? "stopped" : "cancelled-or-unavailable");
+          equal(error.outcome, "not-sent");
         }
         equal(state.requests.length, 1);
       });
diff --git a/web/workspace/src/lib/workspace/auth/model.test.ts b/web/workspace/src/lib/workspace/auth/model.test.ts
index 4c17c2df3..63006f4d2 100644
--- a/web/workspace/src/lib/workspace/auth/model.test.ts
+++ b/web/workspace/src/lib/workspace/auth/model.test.ts
@@ -2,6 +2,7 @@ import {
   authenticationCredentialToJson,
   base64UrlToBuffer,
   bufferToBase64Url,
+  parseAuthUserResponse,
   parseDeviceLoginPollResponse,
   parseDeviceLoginStartResponse,
   parseWhoamiResponse,
@@ -119,12 +120,21 @@ Deno.test("prepareLoginOptions decodes challenge and allowed credential ids", ()
 
 Deno.test("whoami rejects unknown auth methods and extra fields", () => {
   assertEquals(
-    parseWhoamiResponse({ actor: null, session: { kind: "anonymous" } }),
-    { actor: null, session: { kind: "anonymous" } },
+    parseWhoamiResponse({
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "anonymous" },
+    }),
+    {
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "anonymous" },
+    },
   );
   assertThrows(
     () =>
       parseWhoamiResponse({
+        authentication_reference: "fixture-authentication",
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
         actor: {
           user_id: "user-1",
@@ -137,7 +147,12 @@ Deno.test("whoami rejects unknown auth methods and extra fields", () => {
     "unknown auth method",
   );
   assertThrows(
-    () => parseWhoamiResponse({ actor: null, token: "secret" }),
+    () =>
+      parseWhoamiResponse({
+        actor: null,
+        authentication_reference: null,
+        token: "secret",
+      }),
     "unexpected whoami field",
   );
 });
@@ -197,7 +212,11 @@ Deno.test("auth validation enforces cumulative budgets without echoing unknown k
 
   const attackerKey = `secret-${"x".repeat(512)}`;
   try {
-    parseWhoamiResponse({ actor: null, [attackerKey]: true });
+    parseWhoamiResponse({
+      actor: null,
+      authentication_reference: null,
+      [attackerKey]: true,
+    });
     throw new Error("expected an error");
   } catch (error) {
     if (!(error instanceof Error) || error.message.includes(attackerKey)) {
@@ -248,23 +267,153 @@ Deno.test("whoami fails closed on actor-state mismatch and malformed expiry", ()
   };
   for (
     const payload of [
-      { actor, session: { kind: "anonymous" } },
-      { actor, session: { kind: "expired" } },
+      { actor, authentication_reference: null, session: { kind: "anonymous" } },
+      { actor, authentication_reference: null, session: { kind: "expired" } },
       {
         actor: null,
+        authentication_reference: null,
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
       },
-      { actor, session: { kind: "authenticated", expires_at: null } },
-      { actor, session: { kind: "authenticated", expires_at: "tomorrow" } },
-      { actor: null, session: { kind: "future" } },
+      {
+        actor,
+        authentication_reference: "fixture-authentication",
+        session: { kind: "authenticated", expires_at: null },
+      },
+      {
+        actor,
+        authentication_reference: "fixture-authentication",
+        session: { kind: "authenticated", expires_at: "tomorrow" },
+      },
       {
         actor: null,
+        authentication_reference: null,
+        session: { kind: "future" },
+      },
+      {
+        actor: null,
+        authentication_reference: null,
         session: { kind: "expired", expires_at: "2099-01-01T00:00:00Z" },
       },
     ]
   ) assertThrows(() => parseWhoamiResponse(payload), "inconsistent whoami");
   assertEquals(
-    parseWhoamiResponse({ actor: null, session: { kind: "expired" } }),
-    { actor: null, session: { kind: "expired" } },
+    parseWhoamiResponse({
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "expired" },
+    }),
+    {
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "expired" },
+    },
+  );
+});
+
+Deno.test("whoami and completion require explicit consistent authentication references", () => {
+  const user = {
+    user_id: "u",
+    account_id: "a",
+    handle: "alice",
+    display_name: "Alice",
+  };
+  const authenticated = {
+    actor: { ...user, auth_method: "browser_session" },
+    session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+  } as const;
+  for (const reference of [undefined, null, "", 42, "x".repeat(16385)]) {
+    assertThrows(
+      () =>
+        parseWhoamiResponse({
+          ...authenticated,
+          authentication_reference: reference,
+        }),
+      "invalid authenticated reference",
+    );
+    assertThrows(
+      () =>
+        parseAuthUserResponse({ user, authentication_reference: reference }),
+      "invalid issuance reference",
+    );
+  }
+  for (const kind of ["anonymous", "expired"]) {
+    assertThrows(
+      () => parseWhoamiResponse({ actor: null, session: { kind } }),
+      "missing anonymous reference",
+    );
+    assertThrows(
+      () =>
+        parseWhoamiResponse({
+          actor: null,
+          authentication_reference: "issued",
+          session: { kind },
+        }),
+      "anonymous reference must be null",
+    );
+  }
+  const completion = { user, authentication_reference: "issued" };
+  assertEquals(parseAuthUserResponse(completion), completion);
+  assertEquals(
+    parseWhoamiResponse({
+      ...authenticated,
+      authentication_reference: "issued",
+    }),
+    {
+      actor: authenticated.actor,
+      authentication_reference: "issued",
+      session: authenticated.session,
+    },
+  );
+});
+
+Deno.test("bounded future transports do not discard a created credential and required crypto bytes stay validated", () => {
+  const bytes = new Uint8Array([1, 2, 3]).buffer;
+  const credential = {
+    id: "AQID",
+    rawId: bytes,
+    type: "public-key",
+    getClientExtensionResults: () => ({
+      credProps: { rk: true },
+      prf: { results: { first: bytes } },
+      largeBlob: { blob: bytes },
+    }),
+    response: {
+      clientDataJSON: bytes,
+      attestationObject: bytes,
+      getTransports: () => ["internal", "hybrid", "future-bounded-transport"],
+    },
+  };
+  const converted = registrationCredentialToJson(credential) as {
+    response: { transports: string[] };
+    clientExtensionResults: unknown;
+  };
+  assertEquals(converted.response.transports, ["internal", "hybrid"]);
+  assertEquals(converted.clientExtensionResults, { credProps: { rk: true } });
+  assertThrows(
+    () =>
+      registrationCredentialToJson({
+        ...credential,
+        response: { ...credential.response, clientDataJSON: "not-binary" },
+      }),
+    "required client data remains binary",
+  );
+  assertThrows(
+    () =>
+      registrationCredentialToJson({
+        ...credential,
+        response: {
+          ...credential.response,
+          getTransports: () => ["x".repeat(16385)],
+        },
+      }),
+    "transport bound remains enforced",
+  );
+  assertThrows(
+    () =>
+      registrationCredentialToJson({
+        ...credential,
+        getClientExtensionResults: () => ({ credProps: { rk: bytes } }),
+      }),
+    "supported JSON extension never silently converts binary to an empty object",
   );
 });
diff --git a/web/workspace/src/lib/workspace/auth/model.ts b/web/workspace/src/lib/workspace/auth/model.ts
index 5923f32b8..21969cdb2 100644
--- a/web/workspace/src/lib/workspace/auth/model.ts
+++ b/web/workspace/src/lib/workspace/auth/model.ts
@@ -8,6 +8,9 @@ import type {
   DeviceLoginPollStatus,
   DeviceLoginStartResponse,
   LogoutResponse,
+  PasskeyListResponse,
+  PasskeySummary,
+  PasskeyAdditionResultResponse,
   PasskeyLoginOptionsResponse,
   PasskeyRegistrationOptionsResponse,
   RequestActor,
@@ -21,6 +24,9 @@ export type {
   AuthPublicConfig,
   DeviceLoginPollResponse,
   DeviceLoginStartResponse,
+  PasskeyListResponse,
+  PasskeySummary,
+  PasskeyAdditionResultResponse,
   PasskeyLoginOptionsResponse,
   PasskeyRegistrationOptionsResponse,
   RequestActor,
@@ -37,8 +43,10 @@ const MAX_DEVICE_LOGIN_SECONDS = 24 * 60 * 60;
 const MAX_WEBAUTHN_TIMEOUT_MS = 10 * 60 * 1000;
 const BASE64URL_PATTERN = /^[A-Za-z0-9_-]+={0,2}$/;
 
+export class AuthPayloadError extends Error {}
+
 function invalid(path: string, reason: string): never {
-  throw new Error(`Invalid auth payload: ${path} ${reason}.`);
+  throw new AuthPayloadError(`Invalid auth payload: ${path} ${reason}.`);
 }
 
 function asRecord(value: unknown, path: string): Record<string, unknown> {
@@ -119,6 +127,7 @@ function boundedJson(
   if (budget.remainingNodes < 0) invalid(path, "has too many values");
   if (depth > MAX_AUTH_VALUE_DEPTH) invalid(path, "is too deeply nested");
   if (value === null || typeof value === "boolean") return;
+  if (value instanceof ArrayBuffer || ArrayBuffer.isView(value)) invalid(path, "contains unsupported binary data");
   if (typeof value === "string") {
     boundedString(value, path, { allowEmpty: true });
     budget.remainingStringUnits -= value.length;
@@ -205,10 +214,10 @@ export function bufferToBase64Url(value: ArrayBuffer): string {
 function parseAuthenticatorTransport(
   value: unknown,
   path: string,
-): AuthenticatorTransport {
+): AuthenticatorTransport | null {
   const transport = boundedString(value, path);
   if (!["ble", "hybrid", "internal", "nfc", "usb"].includes(transport)) {
-    invalid(path, "contains an unknown authenticator transport");
+    return null;
   }
   return transport as AuthenticatorTransport;
 }
@@ -229,9 +238,10 @@ function parseCredentialDescriptor(
     if (descriptor.transports.length > MAX_AUTH_ARRAY_LENGTH) {
       invalid(`${path}.transports`, "has too many items");
     }
-    return descriptor.transports.map((transport, index) =>
-      parseAuthenticatorTransport(transport, `${path}.transports[${index}]`)
-    );
+    return descriptor.transports.flatMap((transport, index) => {
+      const parsed = parseAuthenticatorTransport(transport, `${path}.transports[${index}]`);
+      return parsed === null ? [] : [parsed];
+    });
   })();
   return {
     type: "public-key",
@@ -463,7 +473,8 @@ function parseActor(value: unknown, path: string): RequestActor {
 
 export function parseWhoamiResponse(value: unknown): WhoamiResponse {
   const response = asRecord(value, "whoami");
-  requireExactKeys(response, "whoami", ["actor", "session"]);
+  requireExactKeys(response, "whoami", ["actor", "session", "authentication_reference"]);
+  const authentication_reference = optionalString(response.authentication_reference, "whoami.authentication_reference");
   const actor = response.actor === null
     ? null
     : parseActor(response.actor, "whoami.actor");
@@ -487,7 +498,8 @@ export function parseWhoamiResponse(value: unknown): WhoamiResponse {
         "must identify the server session expiry",
       );
     }
-    return { actor, session: { kind: "authenticated", expires_at: expiry } };
+    if (authentication_reference === null) invalid("whoami", "authenticated session requires comparison evidence");
+    return { actor, authentication_reference, session: { kind: "authenticated", expires_at: expiry } };
   }
   requireExactKeys(session, "whoami.session", ["kind"]);
   if (
@@ -496,7 +508,8 @@ export function parseWhoamiResponse(value: unknown): WhoamiResponse {
   ) {
     invalid("whoami", "inconsistent actor or session state");
   }
-  return { actor: null, session: { kind: session.kind } };
+  if (authentication_reference !== null) invalid("whoami", "anonymous session cannot identify authentication");
+  return { actor: null, authentication_reference: null, session: { kind: session.kind } };
 }
 
 export function parseAuthPublicConfig(value: unknown): AuthPublicConfig {
@@ -537,10 +550,38 @@ export function parseAuthPublicConfig(value: unknown): AuthPublicConfig {
   return result;
 }
 
+export function parseAuthUser(value: unknown): AuthUser {
+  return parseAuthenticatedUser(value, "auth_user.user");
+}
+
 export function parseAuthUserResponse(value: unknown): PasskeyUserResponse {
   const response = asRecord(value, "auth_user");
-  requireExactKeys(response, "auth_user", ["user"]);
-  return { user: parseAuthenticatedUser(response.user, "auth_user.user") };
+  requireExactKeys(response, "auth_user", ["user", "authentication_reference"]);
+  return { user: parseAuthenticatedUser(response.user, "auth_user.user"), authentication_reference: boundedString(response.authentication_reference, "auth_user.authentication_reference") };
+}
+
+function parsePasskeySummary(value: unknown): PasskeySummary {
+  const key = asRecord(value, "passkey_summary");
+  requireExactKeys(key, "passkey_summary", ["key_reference", "created_at", "last_used_at", "normal_login_verified_at"]);
+  const date = (value: unknown): string => {
+    const text = boundedString(value, "passkey_summary.timestamp");
+    if (!Number.isFinite(Date.parse(text))) invalid("passkey_summary.timestamp", "must be a timestamp");
+    return text;
+  };
+  return { key_reference: boundedString(key.key_reference, "passkey_summary.key_reference"), created_at: date(key.created_at), last_used_at: key.last_used_at === null ? null : date(key.last_used_at), normal_login_verified_at: key.normal_login_verified_at === null ? null : date(key.normal_login_verified_at) };
+}
+export function parsePasskeyList(value: unknown): PasskeyListResponse {
+  const list = asRecord(value, "passkey_list");
+  requireExactKeys(list, "passkey_list", ["user", "keys"]);
+  if (!Array.isArray(list.keys) || list.keys.length > MAX_AUTH_ARRAY_LENGTH) invalid("passkey_list.keys", "must be a bounded array");
+  return { user: parseAuthenticatedUser(list.user, "passkey_list.user"), keys: list.keys.map(parsePasskeySummary) };
+}
+export function parseAdditionResult(value: unknown): PasskeyAdditionResultResponse {
+  const result = asRecord(value, "addition_result");
+  if (result.status === "unknown") { requireExactKeys(result, "addition_result", ["status"]); return { status: "unknown" }; }
+  requireExactKeys(result, "addition_result", ["status", "user", "key"]);
+  if (result.status !== "saved") invalid("addition_result", "contains an unknown status");
+  return { status: "saved", user: parseAuthenticatedUser(result.user, "addition_result.user"), key: parsePasskeySummary(result.key) };
 }
 
 export function prepareRegistrationOptions(
@@ -583,11 +624,14 @@ function clientExtensionResults(
   const value = (credential.getClientExtensionResults as () => unknown).call(
     credential,
   );
-  boundedJson(value, "credential.clientExtensionResults");
-  return asRecord(
-    value,
-    "credential.clientExtensionResults",
-  ) as AuthenticationExtensionsClientOutputs;
+  const output = asRecord(value, "credential.clientExtensionResults");
+  // 現Serverが消費するJSON拡張だけを転送する。PRF/largeBlob等の未要求binary
+  // outputsをJSON.stringifyで{}へ変えたり、未使用機能として有効化したりしない。
+  const supported = Object.fromEntries(
+    ["appid", "credProps", "hmacSecret", "credProtect", "minPinLength"].filter(key => key in output).map(key => [key, output[key]]),
+  );
+  boundedJson(supported, "credential.clientExtensionResults");
+  return supported as AuthenticationExtensionsClientOutputs;
 }
 
 export function registrationCredentialToJson(credential: unknown): unknown {
@@ -605,12 +649,12 @@ export function registrationCredentialToJson(credential: unknown): unknown {
   ) {
     invalid("credential.response.transports", "must be a bounded array");
   }
-  const transports = transportsValue.map((transport, index) =>
-    parseAuthenticatorTransport(
-      transport,
-      `credential.response.transports[${index}]`,
-    )
-  );
+  // transportは補助hint。Serverのwebauthn-rsも未知値をUnknownとして無視する。
+  // boundedな新値を理由に、端末上で作成済みの暗号credential全体を捨てない。
+  const transports = transportsValue.flatMap((value, index) => {
+    const transport = boundedString(value, `credential.response.transports[${index}]`);
+    return ["ble", "hybrid", "internal", "nfc", "usb"].includes(transport) ? [transport] : [];
+  });
   const authenticatorAttachment = optionalString(
     core.authenticatorAttachment,
     "credential.authenticatorAttachment",
diff --git a/web/workspace/src/lib/workspace/auth/operation.ts b/web/workspace/src/lib/workspace/auth/operation.ts
new file mode 100644
index 000000000..37e2e3b6d
--- /dev/null
+++ b/web/workspace/src/lib/workspace/auth/operation.ts
@@ -0,0 +1,140 @@
+import type { PasskeyAdditionResultRequest } from "#lib/generated/auth-api.ts";
+import type { WhoamiResponse } from "./model.ts";
+
+export type AuthStage =
+  | "session-check"
+  | "options"
+  | "authenticator"
+  | "conversion"
+  | "before-complete"
+  | "complete"
+  | "confirmation";
+export type AuthFailure =
+  | "cancelled-or-unavailable"
+  | "excluded"
+  | "unsupported"
+  | "environment"
+  | "conversion"
+  | "session-changed"
+  | "rejected"
+  | "transport"
+  | "invalid-response"
+  | "stopped";
+export type AuthOutcome =
+  | "not-sent"
+  | "rejected"
+  | "unknown"
+  | "saved-session-unconfirmed";
+
+// 診断は固定分類だけを持つ。cause、例外本文、HTTP body、credentialやceremony IDを保持しない。
+export class AuthOperationError extends Error {
+  constructor(
+    readonly stage: AuthStage,
+    readonly reason: AuthFailure,
+    readonly outcome: AuthOutcome,
+    readonly httpStatus?: number,
+  ) {
+    super(`Passkey ${stage}: ${reason} (${outcome}).`);
+  }
+}
+type Observer = {
+  phase: (stage: AuthStage) => void;
+  verifySession: () => Promise<void>;
+  expected: WhoamiResponse | null;
+  additionAttempt: (attempt: PasskeyAdditionResultRequest) => void;
+};
+const observers = new WeakMap<AbortSignal, Observer>();
+export function observeAuthOperation(
+  signal: AbortSignal,
+  observer: Observer,
+): void {
+  observers.set(signal, observer);
+}
+export function recordAdditionAttempt(
+  signal: AbortSignal | undefined,
+  attempt: PasskeyAdditionResultRequest,
+): void {
+  if (signal) observers.get(signal)?.additionAttempt(attempt);
+}
+export function expectedAuthSession(
+  signal?: AbortSignal,
+): WhoamiResponse | null {
+  return signal ? observers.get(signal)?.expected ?? null : null;
+}
+export async function authCheckpoint(
+  signal: AbortSignal | undefined,
+  stage: AuthStage,
+): Promise<void> {
+  signal?.throwIfAborted();
+  const observer = signal ? observers.get(signal) : undefined;
+  observer?.phase(stage);
+  if (stage === "options" || stage === "before-complete") {
+    await observer?.verifySession();
+  }
+  signal?.throwIfAborted();
+}
+export function classifyAuthFailure(
+  error: unknown,
+  stage: AuthStage,
+  sent: boolean,
+): AuthOperationError {
+  if (error instanceof AuthOperationError) return error;
+  const outcome = sent ? "unknown" : "not-sent";
+  if (
+    error instanceof DOMException &&
+    (stage === "authenticator" || error.name === "AbortError")
+  ) {
+    switch (error.name) {
+      case "AbortError":
+        return new AuthOperationError(stage, "stopped", outcome);
+      case "InvalidStateError":
+        return new AuthOperationError(stage, "excluded", outcome);
+      case "NotAllowedError":
+        return new AuthOperationError(
+          stage,
+          "cancelled-or-unavailable",
+          outcome,
+        );
+      case "NotSupportedError":
+        return new AuthOperationError(stage, "unsupported", outcome);
+      case "SecurityError":
+        return new AuthOperationError(stage, "environment", outcome);
+    }
+  }
+  return new AuthOperationError(
+    stage,
+    stage === "conversion" ? "conversion" : "transport",
+    outcome,
+  );
+}
+export function operationErrorMessage(error: AuthOperationError): string {
+  const reason: Record<AuthFailure, string> = {
+    "cancelled-or-unavailable":
+      "The browser did not complete verification. It may have been cancelled, timed out, or found no usable key; the browser does not distinguish these reasons.",
+    excluded:
+      "The authenticator reported an existing key (duplicate exclusion). Keep the older key and choose a different device, security key, or passkey provider; do not delete your only working key.",
+    unsupported:
+      "This browser or key cannot complete this passkey operation. Use a supported device that can save passkeys and verify with a PIN or biometrics.",
+    environment:
+      "The browser blocked this operation because of an origin, security, or environment constraint. Check that you are using the intended secure site; the exact cause is not known.",
+    conversion:
+      "The device may have created a key, but its response could not be converted for the server. Registration was not sent. Keep existing keys; a device-side entry alone does not mean it was saved to this account.",
+    "session-changed":
+      "The account or session changed, or could not be confirmed. The result cannot be applied to the previously displayed account.",
+    rejected:
+      "The server rejected the request or verification. A challenge may be invalid or expired. Check your account and the operation result before starting a new ceremony.",
+    transport: "Communication could not be confirmed.",
+    "invalid-response": "The server response could not be confirmed.",
+    stopped: "Operation stopped.",
+  };
+  const outcome = error.outcome === "not-sent"
+    ? "Completion was not sent."
+    : error.outcome === "rejected"
+    ? "The server did not accept completion."
+    : error.outcome === "saved-session-unconfirmed"
+    ? "The server confirmed the operation, but the expected browser session is not confirmed."
+    : "Completion may already have reached the server. Its result is unknown; check the operation result before adding another key. Stopping the browser does not undo a submitted request.";
+  return `${reason[error.reason]} ${outcome} [${error.stage}/${error.reason}${
+    error.httpStatus ? `/HTTP-${error.httpStatus}` : ""
+  }]`;
+}
diff --git a/web/workspace/src/lib/workspace/auth/page-session.browser.spec.ts b/web/workspace/src/lib/workspace/auth/page-session.browser.spec.ts
index 456b5d3eb..9f4bf8a74 100644
--- a/web/workspace/src/lib/workspace/auth/page-session.browser.spec.ts
+++ b/web/workspace/src/lib/workspace/auth/page-session.browser.spec.ts
@@ -59,7 +59,7 @@ for (const kind of ["anonymous", "expired"] as const) {
     await browserSession.ensure();
     expect(fetcher).toHaveBeenCalledTimes(1);
     fetcher.mockResolvedValueOnce(
-      Response.json({ actor: null, session: { kind } }),
+      Response.json({ authentication_reference: null, actor: null, session: { kind } }),
     );
     await expect(requirePageSession(target)).rejects.toMatchObject({
       status: 307,
diff --git a/web/workspace/src/lib/workspace/auth/passkey-results.browser.spec.ts b/web/workspace/src/lib/workspace/auth/passkey-results.browser.spec.ts
new file mode 100644
index 000000000..bf4f7f469
--- /dev/null
+++ b/web/workspace/src/lib/workspace/auth/passkey-results.browser.spec.ts
@@ -0,0 +1,624 @@
+// @vitest-environment happy-dom
+// BrowserAuth→本番adapterの競合/結果判定。HTTPと認証器のみをgate付きで代替し、
+// Server検証/保存の根拠にはしない。秘密の本文は診断へ保存しない。
+import { afterEach, expect, test, vi } from "vitest";
+import { BrowserAuth } from "./browser-session.svelte.ts";
+import { browserSession, sessionMutation } from "./session-state.ts";
+import { addPasskey, loginWithPasskey, logout } from "./api.ts";
+import {
+  authUser,
+  credentialFixture,
+  loginOptions,
+  registrationOptions,
+} from "./api.test-fixtures.ts";
+
+const owners: BrowserAuth[] = [];
+afterEach(() => {
+  for (const owner of owners.splice(0)) owner.dispose();
+  browserSession.invalidate();
+  vi.unstubAllGlobals();
+  vi.restoreAllMocks();
+});
+function gate<T>() {
+  let resolve!: (value: T) => void;
+  const promise = new Promise<T>((done) => {
+    resolve = done;
+  });
+  return { promise, resolve };
+}
+function identity(user: typeof authUser | null) {
+  return Response.json({
+    authentication_reference: user ? "fixture-authentication" : null,
+    actor: user ? { ...user, auth_method: "browser_session" } : null,
+    session: user
+      ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
+      : { kind: "anonymous" },
+  });
+}
+function harness() {
+  const state = { user: authUser as typeof authUser | null, completed: false };
+  const create = vi.fn<CredentialsContainer["create"]>().mockResolvedValue(
+    credentialFixture(),
+  );
+  const get = vi.fn<CredentialsContainer["get"]>().mockResolvedValue(
+    credentialFixture(true),
+  );
+  vi.stubGlobal("navigator", { credentials: { create, get } });
+  const fetcher = vi.fn<typeof fetch>().mockImplementation(async (input) => {
+    const path = String(input);
+    if (path === "/api/auth/whoami") return identity(state.user);
+    if (path.endsWith("/options")) {
+      return Response.json(
+        path.includes("login") ? loginOptions : registrationOptions,
+      );
+    }
+    if (path.endsWith("/complete")) {
+      state.completed = true;
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
+    }
+    if (path === "/api/auth/logout") {
+      state.user = null;
+      return Response.json({ status: "logged_out" });
+    }
+    throw new Error("Unexpected synthetic endpoint");
+  });
+  vi.stubGlobal("fetch", fetcher);
+  const auth = new BrowserAuth();
+  owners.push(auth);
+  return { state, create, get, fetcher, auth };
+}
+function savedAddition() {
+  return Response.json({
+    status: "saved",
+    user: authUser,
+    key: {
+      key_reference: "safe-opaque-reference",
+      created_at: "2026-01-01T00:00:00Z",
+      last_used_at: null,
+      normal_login_verified_at: null,
+    },
+  });
+}
+async function recoveryHarness() {
+  const context = harness();
+  await context.auth.refresh();
+  context.auth.additionAttempt = {
+    challenge_id: "synthetic-addition",
+    expected_user_id: authUser.user_id,
+    expected_account_id: authUser.account_id,
+    expected_authentication_reference: "original-operation-reference",
+  };
+  return context;
+}
+for (const phase of ["initial-whoami", "receipt", "final-whoami"] as const) {
+  for (const reason of ["logout", "authentication"] as const) {
+    test(`recovery ${phase} rejects a shared ${reason} stamp before event delivery`, async () => {
+      const { auth, fetcher } = await recoveryHarness();
+      const started = gate<void>(), response = gate<Response>();
+      let whoami = 0, receiptReads = 0;
+      fetcher.mockImplementation(async (input, init) => {
+        const path = String(input);
+        if (path === "/api/auth/whoami") {
+          ++whoami;
+          if (phase === (whoami === 1 ? "initial-whoami" : "final-whoami")) {
+            started.resolve();
+            return response.promise;
+          }
+          return identity(authUser);
+        }
+        if (path.endsWith("/addition/result")) {
+          ++receiptReads;
+          expect(
+            JSON.parse(String(init?.body)).expected_authentication_reference,
+          )
+            .toBe("original-operation-reference");
+          if (phase === "receipt") {
+            started.resolve();
+            return response.promise;
+          }
+          return savedAddition();
+        }
+        throw new Error("Unexpected recovery endpoint");
+      });
+      const generation = browserSession.authenticationGeneration;
+      const stamp = browserSession.authenticationStamp;
+      const checking = auth.checkAddition();
+      await started.promise;
+      await auth.checkAddition(); // busy recovery cannot issue a second read
+      const changed = JSON.stringify({
+        id: `recovery-${phase}-${reason}`,
+        reason,
+      });
+      localStorage.setItem("yoi.browser-auth-generation", changed);
+      expect(browserSession.authenticationStamp).not.toBe(stamp);
+      expect(browserSession.authenticationGeneration).toBe(generation);
+      response.resolve(
+        phase === "receipt" ? savedAddition() : identity(authUser),
+      );
+      await checking;
+      expect(auth.additionSaved).toBe(false);
+      expect(auth.additionAttempt?.expected_authentication_reference)
+        .toBe("original-operation-reference");
+      expect(auth.status).not.toContain("current session was checked");
+      expect(auth.error).toContain("does not prove failure");
+      expect(receiptReads).toBe(phase === "initial-whoami" ? 0 : 1);
+      expect(whoami).toBe(phase === "final-whoami" ? 2 : 1);
+      expect(localStorage.getItem("yoi.browser-auth-generation")).toBe(changed);
+      expect(
+        fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+      )
+        .toBe(false);
+    });
+  }
+}
+for (const phase of ["receipt", "final-whoami"] as const) {
+  for (const invalidation of ["cancel", "dispose", "generation"] as const) {
+    test(`recovery ${phase} ignores a delayed saved response after ${invalidation}`, async () => {
+      const { auth, fetcher } = await recoveryHarness();
+      const started = gate<void>(), response = gate<Response>();
+      let whoami = 0;
+      fetcher.mockImplementation(async (input) => {
+        const path = String(input);
+        if (path === "/api/auth/whoami") {
+          if (++whoami === 2 && phase === "final-whoami") {
+            started.resolve();
+            return response.promise;
+          }
+          return identity(authUser);
+        }
+        if (path.endsWith("/addition/result")) {
+          if (phase === "receipt") {
+            started.resolve();
+            return response.promise;
+          }
+          return savedAddition();
+        }
+        throw new Error("Unexpected recovery endpoint");
+      });
+      const checking = auth.checkAddition();
+      await started.promise;
+      if (invalidation === "cancel") auth.cancel();
+      else if (invalidation === "dispose") auth.dispose();
+      else sessionMutation();
+      response.resolve(
+        phase === "receipt" ? savedAddition() : identity(authUser),
+      );
+      await checking;
+      expect(auth.additionSaved).toBe(false);
+      expect(auth.additionAttempt).not.toBeNull();
+      expect(auth.status).not.toContain("current session was checked");
+      expect(whoami).toBe(phase === "receipt" ? 1 : 2);
+      expect(
+        fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+      )
+        .toBe(false);
+    });
+  }
+}
+test("failed recheck cannot retain repeat-add permission from an older saved confirmation", async () => {
+  const { auth, fetcher } = await recoveryHarness();
+  auth.additionSaved = true;
+  fetcher.mockResolvedValue(identity(null));
+  await auth.checkAddition();
+  expect(auth.additionSaved).toBe(false);
+  expect(auth.additionAttempt).not.toBeNull();
+  expect(auth.error).toContain("does not prove failure");
+});
+test("unknown receipt retains the unresolved attempt and never permits blind repetition", async () => {
+  const { auth, fetcher } = await recoveryHarness();
+  fetcher.mockImplementation(async (input) =>
+    String(input).endsWith("/addition/result")
+      ? Response.json({ status: "unknown" })
+      : identity(authUser)
+  );
+  await auth.checkAddition();
+  expect(auth.additionSaved).toBe(false);
+  expect(auth.additionAttempt).not.toBeNull();
+  expect(auth.status).toContain("still unknown");
+  expect(auth.error).toBe("");
+});
+for (const outcome of ["anonymous", "other-actor", "unavailable"] as const) {
+  test(`addition response is not Added when confirming whoami is ${outcome}`, async () => {
+    const { auth, state, fetcher } = harness();
+    await auth.refresh();
+    const request = fetcher.getMockImplementation()!;
+    fetcher.mockImplementation(async (input, init) => {
+      if (state.completed && String(input) === "/api/auth/whoami") {
+        if (outcome === "unavailable") {
+          throw new TypeError("private network detail");
+        }
+        return identity(
+          outcome === "anonymous" ? null : {
+            ...authUser,
+            user_id: "bob-user",
+            account_id: "bob-account",
+            handle: "bob",
+          },
+        );
+      }
+      return await request(input, init);
+    });
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(auth.status).not.toBe("Added");
+    expect(auth.error).not.toContain("private network detail");
+  });
+}
+for (const invalidation of ["logout", "dispose", "account-change"] as const) {
+  test(`${invalidation} during native prompt never posts a delayed login credential`, async () => {
+    const { auth, state, get, fetcher } = harness();
+    state.user = null;
+    await auth.refresh();
+    const prompted = gate<void>();
+    const credential = gate<Credential | null>();
+    get.mockImplementation(() => {
+      prompted.resolve();
+      return credential.promise;
+    });
+    const run = auth.run("Waiting", "Logged in", loginWithPasskey);
+    await prompted.promise;
+    if (invalidation === "dispose") auth.dispose();
+    else if (invalidation === "account-change") sessionMutation();
+    else {
+      const signout = new BrowserAuth();
+      owners.push(signout);
+      await signout.run("Logging out", "Logged out", logout, "logout");
+    }
+    credential.resolve(credentialFixture(true));
+    expect(await run).toBe(false);
+    expect(
+      fetcher.mock.calls.some(([path]) =>
+        String(path).endsWith("/login/complete")
+      ),
+    ).toBe(false);
+    expect(state.completed).toBe(false);
+  });
+}
+
+const bob = {
+  ...authUser,
+  user_id: "bob-user",
+  account_id: "bob-account",
+  handle: "bob",
+};
+for (const changeAt of ["start", "before-complete"] as const) {
+  test(`stale Alice with Bob cookie at ${changeAt} cannot add to Bob`, async () => {
+    const { auth, state, create, fetcher } = harness();
+    await auth.refresh();
+    if (changeAt === "start") state.user = bob;
+    else {create.mockImplementationOnce(async () => {
+        state.user = bob;
+        return credentialFixture();
+      });}
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(state.completed).toBe(false);
+    expect(
+      fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+    ).toBe(false);
+    if (changeAt === "start") expect(create).not.toHaveBeenCalled();
+    expect(auth.error).toContain("session-changed");
+  });
+}
+test("same owner but different authentication binding before complete is not the expected session", async () => {
+  const { auth, create, fetcher } = harness();
+  await auth.refresh();
+  let changed = false;
+  create.mockImplementationOnce(async () => {
+    changed = true;
+    return credentialFixture();
+  });
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation(async (input, init) =>
+    String(input) === "/api/auth/whoami" && changed
+      ? Response.json({
+        ...(await identity(authUser).json()),
+        authentication_reference: "different-binding",
+      })
+      : request(input, init)
+  );
+  expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+  expect(
+    fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+  ).toBe(false);
+});
+test("returned owner alone does not prove the issued browser session", async () => {
+  const { auth, fetcher } = harness();
+  await auth.refresh();
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation(async (input, init) =>
+    String(input).endsWith("/complete")
+      ? Response.json({
+        user: authUser,
+        authentication_reference: "issued-but-not-current",
+      })
+      : request(input, init)
+  );
+  expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+  expect(auth.error).toContain("expected browser session is not confirmed");
+});
+for (
+  const reason of [
+    "InvalidStateError",
+    "NotAllowedError",
+    "SecurityError",
+    "NotSupportedError",
+  ] as const
+) {
+  test(`native ${reason} has a safe stage-specific classification without raw exceptions`, async () => {
+    const { auth, create } = harness();
+    await auth.refresh();
+    create.mockRejectedValueOnce(
+      new DOMException("RAW-CREDENTIAL-TOKEN-COOKIE", reason),
+    );
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(auth.error).not.toContain("RAW-CREDENTIAL-TOKEN-COOKIE");
+    expect(auth.error).toContain("authenticator/");
+    expect(auth.error).toContain("Completion was not sent");
+    if (reason === "InvalidStateError") {
+      expect(auth.error).toContain("duplicate exclusion");
+    }
+    if (reason === "NotAllowedError") {
+      expect(auth.error).toContain("does not distinguish");
+    }
+  });
+}
+test("device creation followed by conversion failure never sends complete or claims registration", async () => {
+  const { auth, create, fetcher } = harness();
+  await auth.refresh();
+  create.mockResolvedValueOnce(
+    {
+      ...credentialFixture(),
+      rawId: "private-invalid-value",
+    } as unknown as Credential,
+  );
+  expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+  expect(auth.error).toContain("conversion");
+  expect(auth.error).toContain("device may have created");
+  expect(auth.error).not.toContain("private-invalid-value");
+  expect(
+    fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+  ).toBe(false);
+});
+test("duplicate operations are fenced and explicit cancellation stops late credentials before submission", async () => {
+  const { auth, create, fetcher } = harness();
+  await auth.refresh();
+  const started = gate<void>(), credential = gate<Credential | null>();
+  create.mockImplementationOnce(() => {
+    started.resolve();
+    return credential.promise;
+  });
+  const first = auth.run("Waiting", "Added", addPasskey);
+  await started.promise;
+  const duplicate = vi.fn(async () => ({}));
+  expect(await auth.run("Duplicate", "Wrong", duplicate)).toBe(false);
+  expect(duplicate).not.toHaveBeenCalled();
+  auth.cancel();
+  credential.resolve(credentialFixture());
+  expect(await first).toBe(false);
+  expect(
+    fetcher.mock.calls.some(([path]) => String(path).endsWith("/complete")),
+  ).toBe(false);
+});
+test("abort after complete dispatch remains an unknown submitted addition with a recoverable operation", async () => {
+  const { auth, fetcher } = harness();
+  await auth.refresh();
+  const started = gate<void>(), response = gate<Response>();
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation((input, init) => {
+    if (String(input).endsWith("/complete")) {
+      started.resolve();
+      return response.promise;
+    }
+    return request(input, init);
+  });
+  const run = auth.run("Waiting", "Added", addPasskey);
+  await started.promise;
+  auth.cancel();
+  response.resolve(
+    Response.json({
+      user: authUser,
+      authentication_reference: "fixture-authentication",
+    }),
+  );
+  expect(await run).toBe(false);
+  expect(auth.additionAttempt).not.toBeNull();
+  expect(auth.error).toContain("result is unknown");
+  expect(auth.error).not.toContain("Completion was not sent");
+});
+for (
+  const current of [
+    "original-session",
+    "cookie-updated",
+    "anonymous",
+    "bob",
+    "unavailable",
+  ] as const
+) {
+  test(`lost completion body with ${current} distinguishes saved, session evidence and unavailable authority`, async () => {
+    const { auth, state, fetcher } = harness();
+    await auth.refresh();
+    let dispatched = false, resultReads = 0;
+    const request = fetcher.getMockImplementation()!;
+    fetcher.mockImplementation(async (input, init) => {
+      const path = String(input);
+      if (path.endsWith("/complete")) {
+        dispatched = true;
+        throw new TypeError("RAW-HTTP-BODY-TOKEN");
+      }
+      if (path === "/api/auth/whoami" && dispatched) {
+        if (current === "unavailable") throw new TypeError("RAW-WHOAMI-ERROR");
+        if (current === "anonymous") return identity(null);
+        if (current === "bob") return identity(bob);
+        if (current === "cookie-updated") {
+          return Response.json({
+            ...(await identity(authUser).json()),
+            authentication_reference: "new-live-session",
+          });
+        }
+      }
+      if (path.endsWith("/addition/result")) {
+        ++resultReads;
+        expect(JSON.parse(String(init?.body)).expected_authentication_reference)
+          .toBe("fixture-authentication");
+        return Response.json({
+          status: "saved",
+          user: authUser,
+          key: {
+            key_reference: "safe-opaque-reference",
+            created_at: "2026-01-01T00:00:00Z",
+            last_used_at: null,
+            normal_login_verified_at: null,
+          },
+        });
+      }
+      return request(input, init);
+    });
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(auth.additionAttempt).not.toBeNull();
+    expect(auth.error).not.toContain("RAW-");
+    expect(auth.error).toContain("result is unknown");
+    await auth.checkAddition();
+    if (current === "original-session" || current === "cookie-updated") {
+      expect(auth.additionSaved).toBe(true);
+      expect(auth.status).toContain("saved a key");
+      expect(auth.status).toContain(
+        "session issued by completion is not confirmed",
+      );
+      expect(resultReads).toBe(1);
+    } else {
+      expect(auth.additionSaved).toBe(false);
+      expect(resultReads).toBe(0);
+      expect(auth.error).toContain("does not prove failure");
+    }
+    expect(state.completed).toBe(false); // synthetic boundary never acts as the real store
+  });
+}
+
+test("storage mutation arriving before the storage event fences prompt completion even if whoami stays anonymous", async () => {
+  const { auth, state, get, fetcher } = harness();
+  state.user = null;
+  await auth.refresh();
+  get.mockImplementationOnce(async () => {
+    localStorage.setItem(
+      "yoi.browser-auth-generation",
+      JSON.stringify({ id: "another-tab", reason: "logout" }),
+    );
+    return credentialFixture(true);
+  });
+  expect(await auth.run("Waiting", "Logged in", loginWithPasskey)).toBe(false);
+  expect(
+    fetcher.mock.calls.some(([path]) =>
+      String(path).endsWith("/login/complete")
+    ),
+  ).toBe(false);
+});
+
+for (const phase of ["options", "complete"] as const) {
+  test(`malformed ${phase} response records the stage without leaking body or inventing completion`, async () => {
+    const { auth, fetcher } = harness();
+    await auth.refresh();
+    const request = fetcher.getMockImplementation()!;
+    fetcher.mockImplementation((input, init) =>
+      String(input).endsWith(`/${phase}`)
+        ? Promise.resolve(
+          new Response("RAW-CHALLENGE-COOKIE", {
+            headers: { "content-type": "application/json" },
+          }),
+        )
+        : request(input, init)
+    );
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(auth.error).toContain(`${phase}/invalid-response`);
+    expect(auth.error).not.toContain("RAW-CHALLENGE-COOKIE");
+    expect(auth.additionAttempt === null).toBe(phase === "options");
+    if (phase === "options") {
+      expect(auth.error).toContain("Completion was not sent");
+    } else expect(auth.error).toContain("result is unknown");
+  });
+}
+for (
+  const code of [
+    "passkey_authentication_changed",
+    "webauthn_registration_verification_failed",
+  ] as const
+) {
+  test(`HTTP rejection classifies allowlisted ${code} without retaining HTTP body`, async () => {
+    const { auth, fetcher } = harness();
+    await auth.refresh();
+    const request = fetcher.getMockImplementation()!;
+    fetcher.mockImplementation((input, init) =>
+      String(input).endsWith("/complete")
+        ? Promise.resolve(
+          Response.json({
+            message: `${code}: RAW-EXCEPTION-BODY`,
+            secret: "RAW-TOKEN",
+          }, { status: 401 }),
+        )
+        : request(input, init)
+    );
+    expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+    expect(auth.error).not.toContain("RAW-");
+    expect(auth.error).toContain(
+      code === "passkey_authentication_changed"
+        ? "session-changed"
+        : "rejected",
+    );
+    expect(auth.error).toContain("HTTP-401");
+    expect(auth.error).not.toContain("Completion was not sent");
+  });
+}
+
+test("successful logout never marks an earlier unknown addition as saved", async () => {
+  const { auth, fetcher } = harness();
+  await auth.refresh();
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation((input, init) =>
+    String(input).endsWith("/complete")
+      ? Promise.reject(new TypeError("response lost"))
+      : request(input, init)
+  );
+  expect(await auth.run("Waiting", "Added", addPasskey)).toBe(false);
+  expect(auth.additionAttempt).not.toBeNull();
+  expect(auth.additionSaved).toBe(false);
+  expect(await auth.run("Logging out", "Logged out", logout, "logout")).toBe(
+    true,
+  );
+  expect(auth.additionSaved).toBe(false);
+});
+
+test("explicit login from stale expired display remains allowed after another tab cleared the cookie", async () => {
+  const { auth, state, fetcher } = harness();
+  state.user = null;
+  fetcher.mockResolvedValueOnce(
+    Response.json({
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "expired" },
+    }),
+  );
+  await auth.refresh();
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation(async (input, init) => {
+    if (String(input).endsWith("/complete")) state.user = authUser;
+    return await request(input, init);
+  });
+  expect(await auth.run("Waiting", "Logged in", loginWithPasskey)).toBe(true);
+  expect(auth.status).toBe("Logged in");
+});
+test("explicit login from expired display does not replace another tab's authenticated account", async () => {
+  const { auth, state, fetcher, get } = harness();
+  fetcher.mockResolvedValueOnce(
+    Response.json({
+      actor: null,
+      authentication_reference: null,
+      session: { kind: "expired" },
+    }),
+  );
+  await auth.refresh();
+  state.user = bob;
+  expect(await auth.run("Waiting", "Logged in", loginWithPasskey)).toBe(false);
+  expect(get).not.toHaveBeenCalled();
+  expect(state.completed).toBe(false);
+});
diff --git a/web/workspace/src/lib/workspace/auth/session-boundary.browser.spec.ts b/web/workspace/src/lib/workspace/auth/session-boundary.browser.spec.ts
index 80530ea4d..37d21fcba 100644
--- a/web/workspace/src/lib/workspace/auth/session-boundary.browser.spec.ts
+++ b/web/workspace/src/lib/workspace/auth/session-boundary.browser.spec.ts
@@ -43,7 +43,7 @@ test("active expired state removes private content and preserves browser query a
   vi.stubGlobal(
     "fetch",
     vi.fn(async () =>
-      Response.json({ actor: null, session: { kind: "expired" } })
+      Response.json({ authentication_reference: null, actor: null, session: { kind: "expired" } })
     ),
   );
   await browserSession.refresh();
@@ -62,7 +62,7 @@ test("navigation admission does not redirect to the old page return URL", async
   vi.stubGlobal(
     "fetch",
     vi.fn(async () =>
-      Response.json({ actor: null, session: { kind: "expired" } })
+      Response.json({ authentication_reference: null, actor: null, session: { kind: "expired" } })
     ),
   );
   await browserSession.refresh();
diff --git a/web/workspace/src/lib/workspace/auth/session-state.browser.spec.ts b/web/workspace/src/lib/workspace/auth/session-state.browser.spec.ts
index 238024265..ee5acbaf7 100644
--- a/web/workspace/src/lib/workspace/auth/session-state.browser.spec.ts
+++ b/web/workspace/src/lib/workspace/auth/session-state.browser.spec.ts
@@ -13,13 +13,14 @@ afterEach(() => {
   localStorage.clear();
 });
 const anonymous: WhoamiResponse = {
-  actor: null,
+  actor: null, authentication_reference: null,
   session: { kind: "anonymous" },
 };
-const expired: WhoamiResponse = { actor: null, session: { kind: "expired" } };
+const expired: WhoamiResponse = { actor: null, authentication_reference: null, session: { kind: "expired" } };
 const authenticated = (
   expires_at: string | null = "2099-01-01T00:00:00Z",
 ): WhoamiResponse => ({
+  authentication_reference: "fixture-authentication",
   actor: { ...authUser, auth_method: "browser_session" },
   session: { kind: "authenticated", expires_at },
 });
diff --git a/web/workspace/src/lib/workspace/auth/session-state.ts b/web/workspace/src/lib/workspace/auth/session-state.ts
index 202398363..3a115bdeb 100644
--- a/web/workspace/src/lib/workspace/auth/session-state.ts
+++ b/web/workspace/src/lib/workspace/auth/session-state.ts
@@ -17,6 +17,10 @@ export class SessionState {
   private listeners = new Set<(state: SessionSnapshot) => void>();
   private stale = true;
 
+  get authenticationStamp(): string | null {
+    return storageStamp();
+  }
+
   get authenticationGeneration(): number {
     return this.generation;
   }
@@ -38,7 +42,7 @@ export class SessionState {
     ++this.generation;
     this.pending = null;
     this.stale = true;
-    if (!preserveSnapshot) this.publish({ kind: "loading" });
+    this.publish(preserveSnapshot ? this.snapshot : { kind: "loading" });
   }
 
   // Page load owns freshness. Components mounted after it reuse that result.
@@ -100,8 +104,9 @@ export const browserSession = new SessionState();
 
 export function sessionMutation(
   reason: "authentication" | "logout" = "authentication",
+  preserveSnapshot = false,
 ): void {
-  browserSession.invalidate();
+  browserSession.invalidate(preserveSnapshot);
   const message = JSON.stringify({ id: crypto.randomUUID(), reason });
   try {
     localStorage.setItem(GENERATION_KEY, message);
diff --git a/web/workspace/src/lib/workspace/auth/session.browser.spec.ts b/web/workspace/src/lib/workspace/auth/session.browser.spec.ts
index 559b97782..dde48c8a3 100644
--- a/web/workspace/src/lib/workspace/auth/session.browser.spec.ts
+++ b/web/workspace/src/lib/workspace/auth/session.browser.spec.ts
@@ -35,6 +35,7 @@ function session() {
 
 function whoami(authenticated: boolean) {
   return Response.json({
+    authentication_reference: authenticated ? "fixture-authentication" : null,
     session: authenticated
       ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
       : { kind: "anonymous" },
@@ -75,7 +76,10 @@ function boundary(authenticated = false) {
         return new Response(null, { status: state.completeStatus });
       }
       state.authenticated = true;
-      return Response.json({ user: authUser });
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
     }
     throw new Error(`Unexpected API: ${path}`);
   });
@@ -106,6 +110,7 @@ test("loading and failed whoami are not anonymous readiness and cannot start aut
   expect(auth.session).toEqual({
     kind: "ready",
     actor: null,
+    authentication_reference: null,
     session: { kind: "anonymous" },
   });
 });
@@ -162,6 +167,7 @@ test("a delayed pre-logout whoami cannot resurrect the previous actor", async ()
   expect(auth.session).toEqual({
     kind: "ready",
     actor: null,
+    authentication_reference: null,
     session: { kind: "anonymous" },
   });
   oldResponse.resolve(whoami(true));
@@ -169,6 +175,7 @@ test("a delayed pre-logout whoami cannot resurrect the previous actor", async ()
   expect(auth.session).toEqual({
     kind: "ready",
     actor: null,
+    authentication_reference: null,
     session: { kind: "anonymous" },
   });
   expect(auth.status).toBe("Logged out");
@@ -183,26 +190,34 @@ test("busy login rejects duplicate operations and refresh until its post-complet
   const confirmingStarted = gate<void>();
   const request = fetcher.getMockImplementation()!;
   fetcher.mockImplementation((input, init) => {
-    if (String(input) === "/api/auth/whoami") {
+    if (String(input) === "/api/auth/passkeys/login/options") {
+      return options.promise;
+    }
+    if (
+      String(input) === "/api/auth/whoami" &&
+      paths(fetcher).includes("/api/auth/passkeys/login/complete")
+    ) {
       confirmingStarted.resolve();
       return confirming.promise;
     }
     return request(input, init);
   });
-  fetcher.mockReturnValueOnce(options.promise);
   const run = auth.run(
     "Waiting",
     "Logged in",
     (signal) => loginWithPasskey(signal),
   );
   expect(auth.busy).toBe(true);
-  expect(auth.status).toBe("Waiting");
+  expect(auth.status).toMatch(/Checking the account/);
   const duplicate = vi.fn(async () => {});
   expect(await auth.run("duplicate", "incorrect", duplicate)).toBe(false);
   await auth.refresh();
   expect(duplicate).not.toHaveBeenCalled();
-  expect(paths(fetcher)).toEqual([
-    "/api/auth/whoami",
+  // Preflight is asynchronous; wait for the options stage, not an HTTP ordinal.
+  await vi.waitFor(() =>
+    expect(paths(fetcher)).toContain("/api/auth/passkeys/login/options")
+  );
+  expect(paths(fetcher).filter((path) => path !== "/api/auth/whoami")).toEqual([
     "/api/auth/passkeys/login/options",
   ]);
   options.resolve(Response.json(loginOptions));
@@ -212,15 +227,17 @@ test("busy login rejects duplicate operations and refresh until its post-complet
   expect(await auth.run("duplicate", "incorrect", duplicate)).toBe(false);
   await auth.refresh();
   expect(paths(fetcher).filter((path) => path === "/api/auth/whoami"))
-    .toHaveLength(2);
+    .toHaveLength(4);
   confirming.resolve(whoami(true));
   expect(await run).toBe(true);
   expect(auth.busy).toBe(false);
   expect(auth.actor?.handle).toBe("alice");
   expect(auth.status).toBe("Logged in");
   expect(paths(fetcher)).toEqual([
+    "/api/auth/whoami",
     "/api/auth/whoami",
     "/api/auth/passkeys/login/options",
+    "/api/auth/whoami",
     "/api/auth/passkeys/login/complete",
     "/api/auth/whoami",
   ]);
@@ -236,16 +253,16 @@ for (const status of [400, 401, 410]) {
     expect(result).toBe(false);
     expect(auth.busy).toBe(false);
     expect(auth.status).toBe("");
-    expect(auth.error).toMatch(
-      status === 401
-        ? /Authentication request was rejected/
-        : /The request or authentication challenge is invalid or expired/,
-    );
+    expect(auth.error).toMatch(/server rejected the request or verification/);
+    expect(auth.error).toContain(`[complete/rejected/HTTP-${status}]`);
+    expect(auth.error).toContain("server did not accept completion");
     expect(auth.session.kind).toBe("ready");
     expect(auth.actor?.handle ?? null).toBe(status === 401 ? null : "alice");
     expect(paths(fetcher)).toEqual([
+      "/api/auth/whoami",
       "/api/auth/whoami",
       "/api/auth/passkeys/addition/options",
+      "/api/auth/whoami",
       "/api/auth/passkeys/addition/complete",
       "/api/auth/whoami",
     ]);
@@ -278,22 +295,25 @@ for (
     ).toBe(false);
     expect(auth.error).toMatch(
       name === "NotAllowedError"
-        ? /cancelled or timed out/
+        ? /cancelled, timed out, or found no usable key/
         : name === "NotSupportedError"
-        ? /Completion is not confirmed/
+        ? /supported device/
         : name === "AbortError"
-        ? /Completion is not confirmed/
-        : /Authentication could not be confirmed/,
+        ? /Operation stopped/
+        : /Communication could not be confirmed/,
     );
+    expect(auth.error).toContain("Completion was not sent.");
     expect(auth.error).not.toContain("secret credential detail");
     expect(auth.status).toBe("");
     expect(auth.busy).toBe(false);
     expect(auth.session).toEqual({
       kind: "ready",
       actor: null,
+      authentication_reference: null,
       session: { kind: "anonymous" },
     });
     expect(paths(fetcher)).toEqual([
+      "/api/auth/whoami",
       "/api/auth/whoami",
       "/api/auth/passkeys/login/options",
       "/api/auth/whoami",
@@ -314,14 +334,21 @@ test("completion does not confirm authentication when the subsequent whoami fail
   const { fetcher } = boundary();
   const auth = session();
   await auth.refresh();
+  let completed = false;
   fetcher.mockImplementation(async (input) => {
     const path = String(input);
-    if (path === "/api/auth/whoami") return new Response(null, { status: 503 });
+    if (path === "/api/auth/whoami") {
+      return completed ? new Response(null, { status: 503 }) : whoami(false);
+    }
     if (path === "/api/auth/passkeys/login/options") {
       return Response.json(loginOptions);
     }
     if (path === "/api/auth/passkeys/login/complete") {
-      return Response.json({ user: authUser });
+      completed = true;
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
     }
     throw new Error(`Unexpected API: ${path}`);
   });
@@ -385,14 +412,15 @@ test("dispose aborts WebAuthn without accepting late credentials, while shared s
   expect(auth.session).toEqual({
     kind: "ready",
     actor: null,
+    authentication_reference: null,
     session: { kind: "anonymous" },
   });
   expect(auth.status).toBe("Waiting");
   expect(auth.error).toBe("");
   expect(paths(fetcher)).toEqual([
     "/api/auth/whoami",
-    "/api/auth/passkeys/login/options",
     "/api/auth/whoami",
+    "/api/auth/passkeys/login/options",
   ]);
   expect(
     dispatch.mock.calls.filter(([event]) =>
@@ -409,6 +437,7 @@ test("dispose ignores a completion response even when the HTTP boundary does not
   const started = gate<AbortSignal>();
   fetcher.mockImplementation(async (input, init) => {
     const path = String(input);
+    if (path === "/api/auth/whoami") return whoami(false);
     if (path === "/api/auth/passkeys/login/options") {
       return Response.json(loginOptions);
     }
@@ -427,16 +456,22 @@ test("dispose ignores a completion response even when the HTTP boundary does not
   const signal = await started.promise;
   auth.dispose();
   expect(signal.aborted).toBe(true);
-  response.resolve(Response.json({ user: authUser }));
+  response.resolve(
+    Response.json({
+      user: authUser,
+      authentication_reference: "fixture-authentication",
+    }),
+  );
   expect(await run).toBe(false);
   expect(auth.actor).toBeNull();
-  expect(auth.status).toBe("Waiting");
+  expect(auth.status).toBe("Confirming the operation with the server…");
   expect(auth.error).toBe("");
   expect(paths(fetcher)).toEqual([
     "/api/auth/whoami",
-    "/api/auth/passkeys/login/options",
-    "/api/auth/passkeys/login/complete",
     "/api/auth/whoami",
+    "/api/auth/passkeys/login/options",
+    "/api/auth/whoami",
+    "/api/auth/passkeys/login/complete",
   ]);
   expect(
     dispatch.mock.calls.filter(([event]) =>
@@ -451,15 +486,21 @@ test("dispose during the post-operation whoami prevents its late actor from beco
   await auth.refresh();
   const response = gate<Response>();
   const started = gate<void>();
+  let completed = false;
   fetcher.mockImplementation(async (input) => {
     const path = String(input);
     if (path === "/api/auth/passkeys/login/options") {
       return Response.json(loginOptions);
     }
     if (path === "/api/auth/passkeys/login/complete") {
-      return Response.json({ user: authUser });
+      completed = true;
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
     }
     if (path === "/api/auth/whoami") {
+      if (!completed) return whoami(false);
       started.resolve();
       return await response.promise;
     }
@@ -489,7 +530,10 @@ for (const newer of ["logout", "another-actor"] as const) {
     const started = gate<void>();
     const request = fetcher.getMockImplementation()!;
     fetcher.mockImplementation((input, init) => {
-      if (String(input) === "/api/auth/whoami") {
+      if (
+        String(input) === "/api/auth/whoami" &&
+        paths(fetcher).includes("/api/auth/passkeys/login/complete")
+      ) {
         started.resolve();
         return confirming.promise;
       }
@@ -509,6 +553,7 @@ for (const newer of ["logout", "another-actor"] as const) {
       sessionMutation(newer === "logout" ? "logout" : "authentication");
       fetcher.mockResolvedValueOnce(
         newer === "logout" ? whoami(false) : Response.json({
+          authentication_reference: "other-authentication",
           actor: {
             ...authUser,
             user_id: "other-user",
@@ -552,7 +597,8 @@ for (const purpose of ["login", "addition"] as const) {
           purpose === "login" ? loginWithPasskey(signal) : addPasskey(signal),
       ),
     ).toBe(false);
-    expect(auth.error).toMatch(/cancelled or timed out/);
+    expect(auth.error).toMatch(/cancelled, timed out, or found no usable key/);
+    expect(auth.error).toContain("Completion was not sent.");
     expect(paths(fetcher).some((path) => path.endsWith("/complete"))).toBe(
       false,
     );
diff --git a/web/workspace/src/lib/workspace/sidebar/hosting-navigation.browser.spec.ts b/web/workspace/src/lib/workspace/sidebar/hosting-navigation.browser.spec.ts
index d94f83c3f..068bf193f 100644
--- a/web/workspace/src/lib/workspace/sidebar/hosting-navigation.browser.spec.ts
+++ b/web/workspace/src/lib/workspace/sidebar/hosting-navigation.browser.spec.ts
@@ -20,6 +20,7 @@ for (
     const fetcher = vi.fn<typeof fetch>().mockImplementation(async (input) => {
       if (String(input) === "/api/auth/whoami") {
         return Response.json({
+          authentication_reference: actor ? "fixture-authentication" : null,
           session: actor
             ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
             : { kind: "anonymous" },
diff --git a/web/workspace/src/routes/account/+page.svelte b/web/workspace/src/routes/account/+page.svelte
index d86a4f0ba..2a54e0948 100644
--- a/web/workspace/src/routes/account/+page.svelte
+++ b/web/workspace/src/routes/account/+page.svelte
@@ -1,30 +1,72 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import { goto } from '$app/navigation';
-  import { addPasskey, logout } from '#lib/workspace/auth/api.ts';
+  import type { PasskeyListResponse } from '#lib/generated/auth-api.ts';
+  import { addPasskey, logout, loadPasskeys, loadWhoami } from '#lib/workspace/auth/api.ts';
   import { BrowserAuth } from '#lib/workspace/auth/browser-session.svelte.ts';
+  import { browserSession } from '#lib/workspace/auth/session-state.ts';
   import { loginUrl } from '#lib/workspace/auth/routes.ts';
   import '#lib/workspace/auth/auth-page.css';
 
   const auth = new BrowserAuth();
-  async function refresh() {
-    await auth.refresh();
+  let keys = $state<PasskeyListResponse | null>(null);
+  let keysError = $state('');
+  let keysLoading = $state(false);
+  let keyRead = 0;
+  let active = true;
+  let keyController: AbortController | null = null;
+  function time(value: string | null) { return value ? new Date(value).toLocaleString() : 'Not recorded'; }
+  async function refreshKeys() {
+    const actor = auth.actor;
+    if (!actor || !active) return;
+    keyController?.abort();
+    const controller = new AbortController();
+    keyController = controller;
+    const read = ++keyRead;
+    const generation = browserSession.authenticationGeneration;
+    const stamp = browserSession.authenticationStamp;
+    const assertCurrent = () => {
+      controller.signal.throwIfAborted();
+      if (!active || read !== keyRead || generation !== browserSession.authenticationGeneration || stamp !== browserSession.authenticationStamp) throw new Error('Session changed');
+    };
+    keysLoading = true; keysError = '';
+    try {
+      const before = await loadWhoami(controller.signal);
+      assertCurrent();
+      if (before.actor?.user_id !== actor.user_id || before.actor.account_id !== actor.account_id) throw new Error('Account changed');
+      const result = await loadPasskeys(controller.signal);
+      assertCurrent();
+      const after = await loadWhoami(controller.signal);
+      assertCurrent();
+      if (result.user.user_id !== actor.user_id || result.user.account_id !== actor.account_id ||
+          after.actor?.user_id !== actor.user_id || after.actor.account_id !== actor.account_id ||
+          before.authentication_reference !== after.authentication_reference) throw new Error('Session changed');
+      keys = result;
+    } catch {
+      if (active && read === keyRead && !controller.signal.aborted) { keys = null; keysError = 'Registered keys could not be confirmed for this account. Refresh your session before trying again.'; }
+    } finally { if (read === keyRead) keysLoading = false; }
   }
+  async function refresh() { await auth.refresh(); await refreshKeys(); }
   async function add() {
-    if (!auth.actor) return;
-    await auth.run('Waiting for passkey addition…', 'Passkey added to your account.', addPasskey);
+    if (!auth.actor || auth.additionAttempt && !auth.additionSaved) return;
+    await auth.run('Waiting for passkey addition…', 'Passkey added to your account; the expected session was confirmed.', addPasskey);
+    await refreshKeys();
   }
+  async function checkAddition() { await auth.checkAddition(); await refreshKeys(); }
   async function signOut() {
     if (!auth.actor) return;
     const confirmed = await auth.run('Logging out…', 'Logged out.', logout, 'logout');
     if (confirmed && !auth.actor) await goto('/', { replaceState: true });
   }
-  onMount(() => { void auth.ensure(); return () => auth.dispose(); });
+  onMount(() => { void auth.ensure().then(refreshKeys); return () => { active = false; ++keyRead; keyController?.abort(); auth.dispose(); }; });
 </script>
 
 <svelte:head><title>Account · Yoi</title></svelte:head>
 <div class="auth-page" data-sveltekit-preload-data="off">
   <h1>Account</h1>
+  {#if auth.status}<p role="status">{auth.status}</p>{/if}
+  {#if auth.busy}<button type="button" onclick={() => auth.cancel()}>Stop waiting</button>{/if}
+  {#if auth.error}<p role="alert" class="error">{auth.error}</p>{/if}
   {#if auth.session.kind === 'loading'}
     <p class="muted" role="status">Loading session…</p>
   {:else if auth.session.kind === 'error'}
@@ -37,8 +79,41 @@
     </dl>
     <section aria-label="Your Passkeys">
       <h2>Passkeys</h2>
-      <p class="muted">Add a discoverable passkey for login without an account ID. Use a device or key that can save passkeys and verify you with a PIN or biometrics. Existing keys are preserved; do not remove them before confirming the new key works.</p>
-      <button type="button" disabled={auth.busy} onclick={add}>Add passkey to {auth.actor.handle}</button>
+      <p class="muted">Add a passkey for login without an account ID. Use a device or key that saves passkeys and verifies you with a PIN or biometrics. Existing keys are preserved.</p>
+      <p>If an older key is in the same authenticator or saved-key provider, duplicate exclusion can block addition there. Choose a different device, security key, or passkey provider. A different provider on the same device may work only if it does not contain an excluded key. Do not delete an older key to bypass this check.</p>
+      <button type="button" disabled={auth.busy || !!auth.additionAttempt && !auth.additionSaved} onclick={add}>Add passkey to {auth.actor.handle}</button>
+      {#if auth.additionAttempt}
+        <button type="button" disabled={auth.busy} onclick={checkAddition}>Check addition result</button>
+        <p class="muted">A saved result confirms this addition's server record, not that ID-free login works. If the session changed, result access may be unavailable; do not restore an old session or add blindly.</p>
+      {/if}
+      {#if keysLoading}<p role="status">Checking registered keys…</p>{/if}
+      {#if keysError}<p role="alert" class="error">{keysError}</p>{/if}
+      {#if keys && keys.user.user_id === auth.actor.user_id && keys.user.account_id === auth.actor.account_id}
+        <ul class="passkey-list" aria-label="Registered keys">
+          {#each keys.keys as key (key.key_reference)}
+            <li>
+              <dl>
+                <div><dt>Created</dt><dd>{time(key.created_at)}</dd></div>
+                <div><dt>Last used</dt><dd>{time(key.last_used_at)}</dd></div>
+                <div><dt>ID-free login</dt><dd>{key.normal_login_verified_at ? `Verified ${time(key.normal_login_verified_at)}` : 'Not yet verified — storage alone does not prove support'}</dd></div>
+              </dl>
+              <details><summary>Key reference</summary><code>{key.key_reference}</code></details>
+            </li>
+          {/each}
+        </ul>
+        {#if keys.keys.length === 0}<p>No registered keys were returned for this account.</p>{/if}
+      {/if}
+      <button type="button" disabled={auth.busy || keysLoading} onclick={refreshKeys}>Refresh registered keys</button>
+      <details>
+        <summary>Verify migration before retiring older-key login</summary>
+        <ol>
+          <li>Keep this working session and every working older key. If addition is excluded, use a different saved-key provider or authenticator; removing your last key first can lock you out.</li>
+          <li>In a separate browser profile or private window, open <a href="/login" target="_blank" rel="noopener">normal passkey login</a>. Do not open the older-key/ID form. Select the newly saved key and complete verification.</li>
+          <li>Confirm the intended account ID in that window's Account page. Refresh the key list here and check that the chosen key now records verified ID-free login. Repeat for every key and device you intend to rely on; a stored key or resident-key hint alone is not proof.</li>
+          <li>Retain a tested independent way back in before ceasing to rely on an older key. If any required device cannot complete normal login, keep the older-key path available. Do not delete old keys as a prerequisite.</li>
+        </ol>
+        <p>Removing the older-key entry for the service is not safe based on one account's success. The operator must first confirm migration and a working alternative for every affected account/device, keep a rollback path to the older-key entry, and verify normal login before retiring that entry. This page does not delete keys or disable compatibility login.</p>
+      </details>
     </section>
     <div class="actions">
       <button type="button" disabled={auth.busy} onclick={signOut}>Log out</button>
@@ -48,7 +123,12 @@
     <p>No browser session is active.</p>
     <a href={loginUrl('/account')}>Log in to your account</a>
   {/if}
-  {#if auth.status}<p role="status">{auth.status}</p>{/if}
-  {#if auth.error}<p role="alert" class="error">{auth.error}</p>{/if}
   <a href="/dashboard">Dashboard / Workspaces</a>
 </div>
+<style>
+  .passkey-list { padding-inline-start: var(--space-5); display: grid; gap: var(--space-4); }
+  .passkey-list li { min-width: 0; }
+  code { overflow-wrap: anywhere; }
+  ol { padding-inline-start: var(--space-5); }
+  li + li { margin-block-start: var(--space-2); }
+</style>
diff --git a/web/workspace/src/routes/account/account.browser.spec.ts b/web/workspace/src/routes/account/account.browser.spec.ts
index caf68c1fb..6ac7d506d 100644
--- a/web/workspace/src/routes/account/account.browser.spec.ts
+++ b/web/workspace/src/routes/account/account.browser.spec.ts
@@ -63,6 +63,9 @@ function boundary({
         return new Response(null, { status: state.whoamiStatus });
       }
       return Response.json({
+        authentication_reference: state.authenticated
+          ? "fixture-authentication"
+          : null,
         session: state.authenticated
           ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
           : { kind: "anonymous" },
@@ -71,6 +74,9 @@ function boundary({
           : null,
       });
     }
+    if (path === "/api/auth/passkeys") {
+      return Response.json({ user: authUser, keys: [] });
+    }
     if (path === "/api/auth/registration-policy") {
       if (state.policy === "loading") return await policyResponse.promise;
       if (state.policy === "error") return new Response(null, { status: 503 });
@@ -97,7 +103,10 @@ function boundary({
         return new Response(null, { status: state.completeStatus });
       }
       state.authenticated = true;
-      return Response.json({ user: authUser });
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
     }
     if (path === "/api/auth/logout") {
       state.authenticated = false;
@@ -149,6 +158,143 @@ async function submit(name: string) {
   await fireEvent.submit(screen.getByRole("button", { name }).closest("form")!);
 }
 
+for (const phase of ["initial-whoami", "list", "final-whoami"] as const) {
+  for (const reason of ["logout", "authentication"] as const) {
+    test(`registered-key ${phase} confirmation rejects shared ${reason} before event delivery`, async () => {
+      const { fetcher } = boundary({ authenticated: true });
+      render(Account);
+      await screen.findByText(
+        "No registered keys were returned for this account.",
+      );
+      const request = fetcher.getMockImplementation()!;
+      const started = gate<void>(), response = gate<Response>();
+      let whoami = 0, listReads = 0;
+      const metadata = () =>
+        Response.json({
+          user: authUser,
+          keys: [{
+            key_reference: "delayed-key-metadata",
+            created_at: "2026-01-01T00:00:00Z",
+            last_used_at: null,
+            normal_login_verified_at: null,
+          }],
+        });
+      fetcher.mockImplementation(async (input, init) => {
+        const path = String(input);
+        if (path === "/api/auth/whoami") {
+          ++whoami;
+          if (phase === (whoami === 1 ? "initial-whoami" : "final-whoami")) {
+            started.resolve();
+            return response.promise;
+          }
+        }
+        if (path === "/api/auth/passkeys") {
+          ++listReads;
+          if (phase === "list") {
+            started.resolve();
+            return response.promise;
+          }
+          return metadata();
+        }
+        return request(input, init);
+      });
+      const generation = browserSession.authenticationGeneration;
+      const stamp = browserSession.authenticationStamp;
+      await fireEvent.click(
+        screen.getByRole("button", { name: "Refresh registered keys" }),
+      );
+      await started.promise;
+      const changed = JSON.stringify({ id: `keys-${phase}-${reason}`, reason });
+      localStorage.setItem("yoi.browser-auth-generation", changed);
+      expect(browserSession.authenticationStamp).not.toBe(stamp);
+      expect(browserSession.authenticationGeneration).toBe(generation);
+      response.resolve(
+        phase === "list" ? metadata() : await request("/api/auth/whoami"),
+      );
+      await screen.findByText(/Registered keys could not be confirmed/);
+      expect(screen.queryByText("delayed-key-metadata")).toBeNull();
+      expect(listReads).toBe(phase === "initial-whoami" ? 0 : 1);
+      expect(whoami).toBe(phase === "final-whoami" ? 2 : 1);
+      expect(localStorage.getItem("yoi.browser-auth-generation")).toBe(changed);
+      expect(posted(fetcher)).toEqual([]);
+    });
+  }
+}
+
+for (const reason of ["logout", "authentication"] as const) {
+  test(`stale receipt confirmation after shared ${reason} leaves visible repeat-add disabled`, async () => {
+    const { fetcher } = boundary({ authenticated: true });
+    render(Account);
+    await screen.findByText(
+      "No registered keys were returned for this account.",
+    );
+    const request = fetcher.getMockImplementation()!;
+    const started = gate<void>(), response = gate<Response>();
+    let receiptRead = false;
+    fetcher.mockImplementation(async (input, init) => {
+      const path = String(input);
+      if (path.endsWith("/addition/complete")) {
+        throw new TypeError("lost response");
+      }
+      if (path.endsWith("/addition/result")) {
+        receiptRead = true;
+        expect(JSON.parse(String(init?.body)).expected_authentication_reference)
+          .toBe("fixture-authentication");
+        return Response.json({
+          status: "saved",
+          user: authUser,
+          key: {
+            key_reference: "saved-but-session-unconfirmed",
+            created_at: "2026-01-01T00:00:00Z",
+            last_used_at: null,
+            normal_login_verified_at: null,
+          },
+        });
+      }
+      if (path === "/api/auth/whoami" && receiptRead) {
+        receiptRead = false;
+        started.resolve();
+        return response.promise;
+      }
+      return request(input, init);
+    });
+    const add = screen.getByRole("button", {
+      name: /Add passkey to/,
+    }) as HTMLButtonElement;
+    await fireEvent.click(add);
+    await screen.findByText(/result is unknown/);
+    await waitFor(() =>
+      expect(screen.queryByText("Checking registered keys…")).toBeNull()
+    );
+    expect(add.disabled).toBe(true);
+    const checking = screen.getByRole("button", {
+      name: "Check addition result",
+    });
+    await waitFor(() =>
+      expect((checking as HTMLButtonElement).disabled).toBe(false)
+    );
+    await fireEvent.click(checking);
+    await started.promise;
+    const generation = browserSession.authenticationGeneration;
+    localStorage.setItem(
+      "yoi.browser-auth-generation",
+      JSON.stringify({ id: `visible-${reason}`, reason }),
+    );
+    expect(browserSession.authenticationGeneration).toBe(generation);
+    response.resolve(await request("/api/auth/whoami"));
+    await screen.findByText(/The addition result could not be read/);
+    await waitFor(() =>
+      expect((checking as HTMLButtonElement).disabled).toBe(false)
+    );
+    expect(screen.queryByText(/Your current session was checked/)).toBeNull();
+    expect(add.disabled).toBe(true);
+    await fireEvent.click(add);
+    expect(
+      posted(fetcher).filter(({ path }) => path.endsWith("/addition/complete")),
+    ).toHaveLength(1);
+  });
+}
+
 test("normal login needs no account ID and links separate registration and code activation", async () => {
   const { fetcher } = boundary({ policy: true });
   page.url = new URL("https://example.test/login?returnTo=%2Faccount");
@@ -231,19 +377,23 @@ for (
     expect(get).toHaveBeenCalledOnce();
     expect(create).not.toHaveBeenCalled();
     expect(apiPaths(fetcher).filter((path) => path === "/api/auth/whoami"))
-      .toHaveLength(2);
+      .toHaveLength(4);
     expect(apiPaths(fetcher)).not.toContain("/api/auth/device-login/approve");
   });
 }
 
 test("successful login completion without confirmed whoami never navigates", async () => {
-  const { state, get } = boundary();
+  const { state, fetcher } = boundary();
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation(async (input, init) => {
+    const response = await request(input, init);
+    if (String(input) === "/api/auth/passkeys/login/complete") {
+      state.whoamiStatus = 503;
+    }
+    return response;
+  });
   render(Login);
   await enterIdentity();
-  get.mockImplementationOnce(async () => {
-    state.whoamiStatus = 503;
-    return credentialFixture(true);
-  });
   await submit("Log in with passkey");
   await screen.findByText(/Your session could not be loaded/);
   expect(goto).not.toHaveBeenCalled();
@@ -347,7 +497,7 @@ test("policy disabled during WebAuthn rejects registration, reloads policy and n
   await waitFor(() => expect(create).toHaveBeenCalledOnce());
   state.completeStatus = 403;
   credential.resolve(credentialFixture());
-  await screen.findByText("Auth request failed (403).");
+  await screen.findByText(/\[complete\/rejected\/HTTP-403\]/);
   await screen.findByText(/New account registration is disabled/);
   expect(screen.queryByRole("button", { name: "Register new account" }))
     .toBeNull();
@@ -376,7 +526,9 @@ test("account displays the current identity without editable target fields and a
   await fireEvent.click(
     screen.getByRole("button", { name: "Add passkey to alice" }),
   );
-  await screen.findByText("Passkey added to your account.");
+  await screen.findByText(
+    "Passkey added to your account; the expected session was confirmed.",
+  );
   await waitFor(() =>
     expect(
       (screen.getByRole("button", { name: "Log out" }) as HTMLButtonElement)
@@ -388,7 +540,12 @@ test("account displays the current identity without editable target fields and a
     "/api/auth/passkeys/addition/options",
     "/api/auth/passkeys/addition/complete",
   ]);
-  expect(requests[0].body).toEqual({ browser_origin: window.location.origin });
+  expect(requests[0].body).toEqual({
+    browser_origin: window.location.origin,
+    expected_user_id: authUser.user_id,
+    expected_account_id: authUser.account_id,
+    expected_authentication_reference: "fixture-authentication",
+  });
   expect(Object.keys(requests[1].body).sort()).toEqual([
     "challenge_id",
     "credential",
@@ -485,11 +642,18 @@ test("logout confirms the server session is cleared and returns to the public ho
   expect(posted(fetcher)).toEqual([
     { path: "/api/auth/logout", body: {}, credentials: "same-origin" },
   ]);
-  expect(apiPaths(fetcher)).toEqual([
+  const paths = apiPaths(fetcher);
+  expect(paths[0]).toBe("/api/auth/whoami");
+  expect(paths.slice(paths.indexOf("/api/auth/logout") + 1)).toContain(
     "/api/auth/whoami",
-    "/api/auth/logout",
-    "/api/auth/whoami",
-  ]);
+  );
+  expect(
+    paths.every((path) =>
+      ["/api/auth/whoami", "/api/auth/logout", "/api/auth/passkeys"].includes(
+        path,
+      )
+    ),
+  ).toBe(true);
   expect(screen.queryByRole("button", { name: /Add passkey/ })).toBeNull();
 });
 
@@ -499,10 +663,14 @@ test("expired addition revokes stale identity without silently retrying as regis
   await fireEvent.click(
     await screen.findByRole("button", { name: "Add passkey to alice" }),
   );
-  await screen.findByText(/Authentication request was rejected/);
+  await screen.findByText(/server rejected the request or verification/);
   await screen.findByRole("link", { name: "Log in to your account" });
   expect(screen.queryByRole("button", { name: /Add passkey/ })).toBeNull();
-  expect(screen.queryByText("Passkey added to your account.")).toBeNull();
+  expect(
+    screen.queryByText(
+      "Passkey added to your account; the expected session was confirmed.",
+    ),
+  ).toBeNull();
   expect(posted(fetcher).map(({ path }) => path)).toEqual([
     "/api/auth/passkeys/addition/options",
     "/api/auth/passkeys/addition/complete",
@@ -545,7 +713,13 @@ test("WebAuthn cancellation is visible, sends no completion, and allows an expli
   await enterIdentity();
   await submit("Log in with passkey");
   await screen.findByText(
-    "Passkey operation was cancelled or timed out, or no matching key was found. Completion is not confirmed. Use a supported device and try again.",
+    /cancelled, timed out, or found no usable key/,
+  );
+  expect(screen.getByRole("alert").textContent).toContain(
+    "Completion was not sent.",
+  );
+  expect(screen.getByRole("alert").textContent).toContain(
+    "[authenticator/cancelled-or-unavailable]",
   );
   await waitFor(() =>
     expect(
@@ -651,7 +825,12 @@ test("device approval locks its code and rejects a second submit while the serve
     name: "Approve device login",
   });
   const response = gate<Response>();
-  fetcher.mockReturnValueOnce(response.promise);
+  const request = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation((input, init) =>
+    String(input) === "/api/auth/device-login/approve"
+      ? response.promise
+      : request(input, init)
+  );
   const form = approve.closest("form")!;
   await fireEvent.submit(form);
   await screen.findByText("Approving device login…");
@@ -659,9 +838,11 @@ test("device approval locks its code and rejects a second submit while the serve
   expect((screen.getByLabelText("User code") as HTMLInputElement).disabled)
     .toBe(true);
   await fireEvent.submit(form);
-  expect(posted(fetcher).map(({ path }) => path)).toEqual([
-    "/api/auth/device-login/approve",
-  ]);
+  await waitFor(() =>
+    expect(posted(fetcher).map(({ path }) => path)).toEqual([
+      "/api/auth/device-login/approve",
+    ])
+  );
   response.resolve(Response.json({ status: "approved", user: authUser }));
   await screen.findByText("Device login approved. You can return to the CLI.");
   expect(posted(fetcher)).toHaveLength(1);
@@ -679,11 +860,8 @@ for (const status of [401, 410]) {
       (await screen.findByRole("button", { name: "Approve device login" }))
         .closest("form")!,
     );
-    await screen.findByText(
-      status === 401
-        ? /Authentication request was rejected/
-        : /The request or authentication challenge is invalid or expired/,
-    );
+    await screen.findByText(/Authentication request was rejected/);
+    expect(screen.getByRole("alert").textContent).toContain("(" + status + ")");
     expect(
       screen.queryByText("Device login approved. You can return to the CLI."),
     ).toBeNull();
@@ -721,7 +899,7 @@ test("compatibility login keeps its selected form and ID after cancellation and
     target: { value: "alice" },
   });
   await submit("Log in with older key");
-  await screen.findByText(/cancelled or timed out/);
+  await screen.findByText(/cancelled, timed out, or found no usable key/);
   await screen.findByText("Use an older key with account ID");
   expect(
     (screen.getByText("Use an older key with account ID").closest(
diff --git a/web/workspace/src/routes/activate/+page.svelte b/web/workspace/src/routes/activate/+page.svelte
index 84eaaaefb..9c864169d 100644
--- a/web/workspace/src/routes/activate/+page.svelte
+++ b/web/workspace/src/routes/activate/+page.svelte
@@ -3,6 +3,7 @@
   import { activateWithPasskey } from '#lib/workspace/auth/activation.ts';
   import { normalizeActivationHandle } from '#lib/workspace/auth/hosting-accounts.ts';
   import { notifySessionChanged } from '#lib/workspace/auth/hosting.ts';
+  import { browserSession } from '#lib/workspace/auth/session-state.ts';
   import type { AuthUser } from '#lib/workspace/auth/model.ts';
 
   let handle = $state('');
@@ -19,12 +20,15 @@
     try { handle = normalizeActivationHandle(handle); }
     catch { error = 'Check the account ID supplied by your administrator.'; return; }
     const current = ++generation;
+    const authGeneration = browserSession.authenticationGeneration;
+    const authStamp = browserSession.authenticationStamp;
     controller = new AbortController(); busy = true; error = '';
     const pending = activateWithPasskey(handle, code, controller.signal);
     code = '';
     try {
       const confirmed = await pending;
       if (current !== generation) return;
+      if (authGeneration !== browserSession.authenticationGeneration || authStamp !== browserSession.authenticationStamp) throw new Error('Activation superseded');
       user = confirmed;
       notifySessionChanged();
     } catch {
diff --git a/web/workspace/src/routes/activate/activation.browser.spec.ts b/web/workspace/src/routes/activate/activation.browser.spec.ts
index 61dd10376..6df8f1490 100644
--- a/web/workspace/src/routes/activate/activation.browser.spec.ts
+++ b/web/workspace/src/routes/activate/activation.browser.spec.ts
@@ -7,6 +7,11 @@ import {
   waitFor,
 } from "@testing-library/svelte";
 import { afterEach, expect, test, vi } from "vitest";
+import {
+  browserSession,
+  sessionMutation,
+} from "#lib/workspace/auth/session-state.ts";
+import { SESSION_CHANGED_EVENT } from "#lib/workspace/auth/hosting.ts";
 import Activate from "./+page.svelte";
 import {
   authUser,
@@ -15,9 +20,34 @@ import {
 } from "#lib/workspace/auth/api.test-fixtures.ts";
 afterEach(() => {
   cleanup();
+  browserSession.invalidate();
   vi.unstubAllGlobals();
 });
-function boundary(mode: "success" | "pending" | "cancel" | "unknown") {
+function gate<T>() {
+  let resolve!: (value: T) => void;
+  const promise = new Promise<T>((done) => {
+    resolve = done;
+  });
+  return { promise, resolve };
+}
+function confirmedSession() {
+  return {
+    actor: { ...authUser, auth_method: "browser_session" },
+    authentication_reference: "fixture-authentication",
+    session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+  };
+}
+function boundary(
+  mode:
+    | "success"
+    | "pending"
+    | "cancel"
+    | "unknown"
+    | "anonymous"
+    | "bob"
+    | "reference-mismatch"
+    | "unavailable",
+) {
   Object.defineProperty(window, "isSecureContext", {
     configurable: true,
     value: true,
@@ -34,7 +64,36 @@ function boundary(mode: "success" | "pending" | "cancel" | "unknown") {
     }
     if (String(input) === "/api/auth/activation/complete") {
       if (mode === "unknown") throw new Error("private diagnostic");
-      return Response.json({ user: authUser });
+      return Response.json({
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
+    }
+    if (String(input) === "/api/auth/whoami") {
+      if (mode === "unavailable") {
+        return new Response("private diagnostic", { status: 503 });
+      }
+      if (mode === "anonymous") {
+        return Response.json({
+          actor: null,
+          authentication_reference: null,
+          session: { kind: "anonymous" },
+        });
+      }
+      const confirmation = confirmedSession();
+      if (mode === "bob") {
+        confirmation.actor = {
+          ...confirmation.actor,
+          user_id: "user-bob",
+          account_id: "account-bob",
+          handle: "bob",
+          display_name: "Bob",
+        };
+      }
+      if (mode === "reference-mismatch") {
+        confirmation.authentication_reference = "another-authentication";
+      }
+      return Response.json(confirmation);
     }
     throw new Error("Unexpected endpoint");
   });
@@ -54,12 +113,29 @@ async function submit() {
 }
 test("activation page shows signed in only after complete confirmation and clears code before browser prompt", async () => {
   const { fetcher } = boundary("success");
+  const confirmation = gate<Response>();
+  const started = gate<void>();
+  const original = fetcher.getMockImplementation()!;
+  fetcher.mockImplementation((input, init) => {
+    if (String(input) === "/api/auth/whoami") {
+      started.resolve();
+      return confirmation.promise;
+    }
+    return original(input, init);
+  });
   render(Activate);
   await submit();
+  await started.promise;
+  expect(screen.queryByText(/You are signed in/)).toBeNull();
+  expect(screen.queryByRole("link", { name: "Open Account" })).toBeNull();
+  expect((screen.getByLabelText("Activation code") as HTMLInputElement).value)
+    .toBe("");
+  confirmation.resolve(Response.json(confirmedSession()));
   await screen.findByText(/registration and activation confirmed/);
   expect(fetcher.mock.calls.map(([input]) => input)).toEqual([
     "/api/auth/activation/options",
     "/api/auth/activation/complete",
+    "/api/auth/whoami",
   ]);
   expect(screen.queryByLabelText("Activation code")).toBeNull();
   expect(JSON.parse(String(fetcher.mock.calls[0][1]?.body)).handle).toBe(
@@ -99,3 +175,106 @@ for (const mode of ["cancel", "unknown"] as const) {
       .toBe("");
   });
 }
+
+for (
+  const mode of [
+    "anonymous",
+    "bob",
+    "reference-mismatch",
+    "unavailable",
+  ] as const
+) {
+  test(
+    "activation " + mode +
+      " confirmation never claims signed in after successful completion",
+    async () => {
+      const { fetcher, create } = boundary(mode);
+      const changed = vi.fn();
+      window.addEventListener(SESSION_CHANGED_EVENT, changed);
+      try {
+        render(Activate);
+        await submit();
+        await screen.findByRole("alert");
+        expect(fetcher.mock.calls.map(([input]) => input)).toEqual([
+          "/api/auth/activation/options",
+          "/api/auth/activation/complete",
+          "/api/auth/whoami",
+        ]);
+        expect(create).toHaveBeenCalledOnce();
+        expect(screen.getByRole("alert").textContent).toContain(
+          "Passkey login",
+        );
+        expect(screen.getByRole("alert").textContent).not.toContain(
+          "private diagnostic",
+        );
+        expect(screen.queryByText(/You are signed in/)).toBeNull();
+        expect(screen.queryByRole("link", { name: "Open Account" })).toBeNull();
+        expect(
+          (screen.getByLabelText("Activation code") as HTMLInputElement).value,
+        ).toBe("");
+        expect(changed).not.toHaveBeenCalled();
+      } finally {
+        window.removeEventListener(SESSION_CHANGED_EVENT, changed);
+      }
+    },
+  );
+}
+
+test("logout during the activation prompt fences a late credential before completion", async () => {
+  const { fetcher, create } = boundary("success");
+  const credential = gate<Credential>();
+  create.mockReturnValueOnce(credential.promise);
+  render(Activate);
+  await submit();
+  await waitFor(() => expect(create).toHaveBeenCalledOnce());
+  sessionMutation("logout");
+  credential.resolve(credentialFixture());
+  await screen.findByRole("alert");
+  expect(fetcher.mock.calls.map(([input]) => input)).toEqual([
+    "/api/auth/activation/options",
+  ]);
+  expect(screen.queryByText(/You are signed in/)).toBeNull();
+  expect(screen.queryByRole("link", { name: "Open Account" })).toBeNull();
+});
+
+for (const phase of ["prompt", "confirmation"] as const) {
+  for (const reason of ["logout", "authentication"] as const) {
+    test(`activation UI rejects shared ${reason} stamp during ${phase} before event delivery`, async () => {
+      const { create, fetcher } = boundary("success");
+      const started = gate<void>();
+      const pending = gate<void>();
+      const request = fetcher.getMockImplementation()!;
+      if (phase === "prompt") {
+        create.mockImplementation(async () => {
+          started.resolve();
+          await pending.promise;
+          return credentialFixture();
+        });
+      } else {fetcher.mockImplementation(async (input, init) => {
+          if (String(input) === "/api/auth/whoami") {
+            started.resolve();
+            await pending.promise;
+          }
+          return await request(input, init);
+        });}
+      render(Activate);
+      await submit();
+      await started.promise;
+      const generation = browserSession.authenticationGeneration;
+      localStorage.setItem(
+        "yoi.browser-auth-generation",
+        JSON.stringify({ id: crypto.randomUUID(), reason }),
+      );
+      expect(browserSession.authenticationGeneration).toBe(generation);
+      pending.resolve();
+      await screen.findByRole("alert");
+      expect(screen.queryByRole("link", { name: "Open Account" })).toBeNull();
+      expect(screen.queryByText(/You are signed in/)).toBeNull();
+      expect(
+        fetcher.mock.calls.filter(([path]) =>
+          path === "/api/auth/activation/complete"
+        ),
+      ).toHaveLength(phase === "prompt" ? 0 : 1);
+    });
+  }
+}
diff --git a/web/workspace/src/routes/entry.browser.spec.ts b/web/workspace/src/routes/entry.browser.spec.ts
index 42e938741..5c93b0b09 100644
--- a/web/workspace/src/routes/entry.browser.spec.ts
+++ b/web/workspace/src/routes/entry.browser.spec.ts
@@ -53,6 +53,7 @@ function boundary() {
         if (state.sessionGate) return state.sessionGate.promise;
         return state.whoamiStatus === 200
           ? Response.json({
+            authentication_reference: state.signedIn ? "fixture-authentication" : null,
             session: state.signedIn
               ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
               : { kind: "anonymous" },
@@ -326,6 +327,7 @@ test("pending create remains single during an explicit authentication change and
   expect(goto).not.toHaveBeenCalled();
   state.sessionGate.resolve(
     Response.json({
+      authentication_reference: "fixture-authentication",
       session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
       actor: { ...authUser, auth_method: "browser_session" },
     }),
diff --git a/web/workspace/src/routes/hosting/accounts/accounts.browser.spec.ts b/web/workspace/src/routes/hosting/accounts/accounts.browser.spec.ts
index 1d2bed0e8..a9c214e19 100644
--- a/web/workspace/src/routes/hosting/accounts/accounts.browser.spec.ts
+++ b/web/workspace/src/routes/hosting/accounts/accounts.browser.spec.ts
@@ -22,6 +22,7 @@ function boundary(
   const fetcher = vi.fn<typeof fetch>(async (input, init) => {
     if (input === "/api/auth/whoami") {
       return Response.json({
+        authentication_reference: mode !== "anonymous" ? "fixture-authentication" : null,
         session: mode !== "anonymous"
           ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
           : { kind: "anonymous" },
diff --git a/web/workspace/src/routes/hosting/settings/settings.browser.spec.ts b/web/workspace/src/routes/hosting/settings/settings.browser.spec.ts
index 334f15e30..788b2c843 100644
--- a/web/workspace/src/routes/hosting/settings/settings.browser.spec.ts
+++ b/web/workspace/src/routes/hosting/settings/settings.browser.spec.ts
@@ -27,6 +27,7 @@ function boundary(
       const path = String(input);
       if (path === "/api/auth/whoami") {
         return Response.json({
+          authentication_reference: persona !== "anonymous" ? "fixture-authentication" : null,
           session: persona !== "anonymous"
             ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
             : { kind: "anonymous" },
diff --git a/web/workspace/src/routes/hosting/setup/+page.svelte b/web/workspace/src/routes/hosting/setup/+page.svelte
index 81b63c8c7..03c621a53 100644
--- a/web/workspace/src/routes/hosting/setup/+page.svelte
+++ b/web/workspace/src/routes/hosting/setup/+page.svelte
@@ -1,7 +1,8 @@
 <script lang="ts">
   import { onDestroy, onMount } from 'svelte';
   import { browserSession, observeBrowserSession, sessionMutation } from "#lib/workspace/auth/session-state.ts";
-  import { loginWithPasskey } from '#lib/workspace/auth/api.ts';
+  import { loginWithPasskey, loadWhoami } from '#lib/workspace/auth/api.ts';
+  import { observeAuthOperation } from '#lib/workspace/auth/operation.ts';
   import { enrollHostingPasskey } from '#lib/workspace/auth/hosting-enrollment.ts';
   import { loadHostingAccess, notifySessionChanged } from '#lib/workspace/auth/hosting.ts';
   import type { AuthUser } from '#lib/workspace/auth/model.ts';
@@ -12,10 +13,12 @@
   let verifiedLogin = $state(false);
   let error = $state('');
   const controller = new AbortController();
+  let loginController: AbortController | null = null;
   let active = true;
 
   let verifiedGeneration: number | null = null;
-  const isCurrent = (generation: number) => active && generation === browserSession.authenticationGeneration;
+  let verifiedStamp: string | null = null;
+  const isCurrent = (generation: number, stamp: string | null) => active && generation === browserSession.authenticationGeneration && stamp === browserSession.authenticationStamp;
   // 初期Bearerでの鍵追加はcookieを使わない。明示Passkey loginのsessionを検証する。
   function matchesSession(expected: AuthUser): boolean {
     const snapshot = browserSession.snapshot;
@@ -28,9 +31,10 @@
     return browserSession.subscribe(() => {
       // 公開pageにはprivate SessionBoundaryの取消がない。成功表示も確認した世代に限る。
       // 後続の再確認/失効/主体変更では明示loginとaccess確認からやり直す。
-      if (!user || verifiedGeneration !== browserSession.authenticationGeneration || !matchesSession(user)) {
+      if (!user || verifiedGeneration !== browserSession.authenticationGeneration || verifiedStamp !== browserSession.authenticationStamp || !matchesSession(user)) {
         verifiedLogin = false;
         verifiedGeneration = null;
+        verifiedStamp = null;
       }
     });
   });
@@ -61,34 +65,56 @@
     error = '';
     sessionMutation();
     let generation = browserSession.authenticationGeneration;
+    let stamp = browserSession.authenticationStamp;
+    const operation = new AbortController();
+    loginController = operation;
+    let promptGeneration: number | null = generation;
+    const unsubscribe = browserSession.subscribe(() => {
+      if (promptGeneration !== null && !isCurrent(promptGeneration, stamp)) operation.abort();
+    });
     try {
-      const signedIn = await loginWithPasskey(controller.signal);
-      if (!isCurrent(generation)) throw new Error('Login superseded');
-      if (signedIn.user_id !== expected.user_id || signedIn.account_id !== expected.account_id) {
+      const initial = await loadWhoami(operation.signal);
+      if (!isCurrent(generation, stamp)) throw new Error('Login superseded');
+      observeAuthOperation(operation.signal, {
+        expected: initial, phase: () => {}, additionAttempt: () => {},
+        verifySession: async () => {
+          if (!isCurrent(generation, stamp)) operation.abort();
+          operation.signal.throwIfAborted();
+          const current = await loadWhoami(operation.signal);
+          if (!isCurrent(generation, stamp) || initial.actor?.user_id !== current.actor?.user_id || initial.actor?.account_id !== current.actor?.account_id || initial.authentication_reference !== current.authentication_reference) throw new Error('Session changed');
+        },
+      });
+      const signedIn = await loginWithPasskey(operation.signal);
+      if (!isCurrent(generation, stamp)) throw new Error('Login superseded');
+      if (signedIn.user.user_id !== expected.user_id || signedIn.user.account_id !== expected.account_id) {
         throw new Error('Unexpected login actor');
       }
       // Set-Cookie後の確認を共有状態へ発行し、操作前/操作中のreadを再利用しない。
+      promptGeneration = null;
       sessionMutation();
       generation = browserSession.authenticationGeneration;
+      stamp = browserSession.authenticationStamp;
       await browserSession.refresh();
-      if (!isCurrent(generation) || !matchesSession(expected)) throw new Error('Session not verified');
+      if (!isCurrent(generation, stamp) || !matchesSession(expected) || browserSession.snapshot.kind !== 'ready' || browserSession.snapshot.value.authentication_reference !== signedIn.authentication_reference) throw new Error('Session not verified');
       const access = await loadHostingAccess();
-      if (!isCurrent(generation) || !access.is_admin) throw new Error('Access not verified');
+      if (!isCurrent(generation, stamp) || !access.is_admin) throw new Error('Access not verified');
       // accessのawait中にもcookie/actorは変わり得る。success公開前の最終確認を行う。
       await browserSession.refresh();
-      if (!isCurrent(generation) || !matchesSession(expected)) throw new Error('Session superseded');
+      if (!isCurrent(generation, stamp) || !matchesSession(expected) || browserSession.snapshot.kind !== 'ready' || browserSession.snapshot.value.authentication_reference !== signedIn.authentication_reference) throw new Error('Session superseded');
       verifiedGeneration = generation;
+      verifiedStamp = stamp;
       verifiedLogin = true;
       notifySessionChanged();
     } catch {
       if (active) error = 'Passkey login or hosting administrator access could not be verified. Try signing in again, or ask the host operator to check this account.';
       // 応答不明時の再確認は自身がまだ現世代の時だけ。古いfinallyで新logout/loginを
       // invalidateしたり、その確定結果を再取得のloadingへ戻したりしない。
-      if (isCurrent(generation)) {
+      if (isCurrent(generation, stamp)) {
         sessionMutation();
         await browserSession.refresh();
       }
     } finally {
+      promptGeneration = null; unsubscribe(); loginController = null;
       if (active) busy = false;
     }
   }
@@ -97,6 +123,7 @@
     active = false;
     token = '';
     controller.abort();
+    loginController?.abort();
   });
 </script>
 
diff --git a/web/workspace/src/routes/hosting/setup/hosting-setup.browser.spec.ts b/web/workspace/src/routes/hosting/setup/hosting-setup.browser.spec.ts
index 8f85ab28c..41d5f6459 100644
--- a/web/workspace/src/routes/hosting/setup/hosting-setup.browser.spec.ts
+++ b/web/workspace/src/routes/hosting/setup/hosting-setup.browser.spec.ts
@@ -36,37 +36,56 @@ function boundary(
   const create = vi.fn(async () => credentialFixture());
   const get = vi.fn(async () => credentialFixture(true));
   vi.stubGlobal("navigator", { credentials: { create, get } });
-  const fetcher = vi.fn<typeof fetch>().mockImplementation(async (input) => {
-    const path = String(input);
-    if (path === "/api/auth/whoami") {
-      return Response.json({
-        session: actor
-          ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
-          : { kind: "anonymous" },
-        actor: actor ? { ...authUser, auth_method: "browser_session" } : null,
-      });
-    }
-    if (path === "/api/hosting/access") {
-      return Response.json({ is_admin: admin });
-    }
-    if (path === "/api/auth/passkeys/addition/options") {
-      return status === 200
-        ? Response.json(registrationOptions)
-        : new Response("host-test-token", { status });
-    }
-    if (path === "/api/auth/passkeys/addition/complete") {
-      return Response.json({ user: authUser });
-    }
-    if (path === "/api/auth/passkeys/login/options") {
-      return Response.json(loginOptions);
-    }
-    if (path === "/api/auth/passkeys/login/complete") {
-      return failLogin
-        ? new Response(null, { status: 401 })
-        : Response.json({ user: authUser });
-    }
-    throw new Error(`Unexpected API: ${path}`);
-  });
+  const fetcher = vi.fn<typeof fetch>().mockImplementation(
+    async (input, init) => {
+      const path = String(input);
+      if (
+        path === "/api/auth/whoami" &&
+        new Headers(init?.headers).has("authorization")
+      ) {
+        return status === 200
+          ? Response.json({
+            actor: { ...authUser, auth_method: "api_token" },
+            authentication_reference: "fixture-bearer-authentication",
+            session: { kind: "authenticated", expires_at: null },
+          })
+          : new Response("host-test-token", { status });
+      }
+      if (path === "/api/auth/whoami") {
+        return Response.json({
+          authentication_reference: actor ? "fixture-authentication" : null,
+          session: actor
+            ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
+            : { kind: "anonymous" },
+          actor: actor ? { ...authUser, auth_method: "browser_session" } : null,
+        });
+      }
+      if (path === "/api/hosting/access") {
+        return Response.json({ is_admin: admin });
+      }
+      if (path === "/api/auth/passkeys/addition/options") {
+        return status === 200
+          ? Response.json(registrationOptions)
+          : new Response("host-test-token", { status });
+      }
+      if (path === "/api/auth/passkeys/addition/complete") {
+        return Response.json({
+          user: authUser,
+          authentication_reference: "fixture-authentication",
+        });
+      }
+      if (path === "/api/auth/passkeys/login/options") {
+        return Response.json(loginOptions);
+      }
+      if (path === "/api/auth/passkeys/login/complete") {
+        return failLogin ? new Response(null, { status: 401 }) : Response.json({
+          user: authUser,
+          authentication_reference: "fixture-authentication",
+        });
+      }
+      throw new Error(`Unexpected API: ${path}`);
+    },
+  );
   vi.stubGlobal("fetch", fetcher);
   return { fetcher, create, get };
 }
@@ -117,8 +136,10 @@ test("enrollment clears token and omits cookies, then verifies an actual passkey
   for (const [path, init] of requests) {
     expect(String(path)).not.toContain("host-test-token");
     expect(String(init?.body)).not.toContain("host-test-token");
+    expect(init?.credentials).toBe("omit");
+    expect(new Headers(init?.headers).has("cookie")).toBe(false);
     expect(new Headers(init?.headers).get("authorization")).toBe(
-      String(path).includes("/addition/") ? "Bearer host-test-token" : null,
+      "Bearer host-test-token",
     );
   }
   await fireEvent.click(
@@ -130,7 +151,7 @@ test("enrollment clears token and omits cookies, then verifies an actual passkey
   expect(settings.getAttribute("href")).toBe("/hosting/settings");
   expect(get).toHaveBeenCalledTimes(1);
   expect(fetcher.mock.calls.filter(([path]) => path === "/api/auth/whoami"))
-    .toHaveLength(2);
+    .toHaveLength(6);
   expect(fetcher.mock.calls.filter(([path]) => path === "/api/hosting/access"))
     .toHaveLength(1);
   expect(
@@ -179,8 +200,10 @@ test("a different cookie actor cannot be accepted as the enrolled administrator"
   const { fetcher } = boundary();
   const original = fetcher.getMockImplementation()!;
   fetcher.mockImplementation(async (input, init) =>
-    String(input) === "/api/auth/whoami"
+    String(input) === "/api/auth/whoami" &&
+      !new Headers(init?.headers).has("authorization")
       ? Response.json({
+        authentication_reference: "fixture-authentication",
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
         actor: {
           ...authUser,
@@ -221,7 +244,12 @@ test("leaving during the passkey prompt aborts enrollment and prevents later com
   unmount();
   expect(signal.aborted).toBe(true);
   resolve(credentialFixture());
-  await waitFor(() => expect(fetcher).toHaveBeenCalledTimes(1));
+  await waitFor(() =>
+    expect(fetcher.mock.calls.map(([path]) => path)).toEqual([
+      "/api/auth/whoami",
+      "/api/auth/passkeys/addition/options",
+    ])
+  );
   const { unmount: unmountAgain } = render(Setup);
   expect((screen.getByLabelText("Host setup token") as HTMLInputElement).value)
     .toBe("");
@@ -248,7 +276,7 @@ test("completion response loss does not claim success and points to login before
   );
   expect((screen.getByLabelText("Host setup token") as HTMLInputElement).value)
     .toBe("");
-  expect(fetcher).toHaveBeenCalledTimes(2);
+  expect(fetcher).toHaveBeenCalledTimes(3);
   expect(screen.queryByRole("button", { name: "Sign in with new passkey" }))
     .toBeNull();
 });
@@ -259,6 +287,7 @@ test("API token identity is not mistaken for a verified browser session", async
   fetcher.mockImplementation(async (input, init) =>
     String(input) === "/api/auth/whoami"
       ? Response.json({
+        authentication_reference: "fixture-authentication",
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
         actor: { ...authUser, auth_method: "api_token" },
       })
@@ -292,6 +321,7 @@ const replacedActor = {
 function identityResponse(actor: typeof setupActor | null) {
   return Response.json({
     actor,
+    authentication_reference: actor ? "fixture-authentication" : null,
     session: actor
       ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
       : { kind: "anonymous" },
@@ -317,15 +347,25 @@ for (const phase of ["login", "whoami", "access", "confirmation"] as const) {
       const started = gate<void>();
       const pending = gate<Response>();
       let current: typeof setupActor | null = setupActor;
-      let reads = 0;
+      let loginCompleted = false;
+      let accessRead = false;
+      let held = false;
       fetcher.mockImplementation((input, init) => {
         const path = String(input);
+        // Bearer identity resolution belongs to enrollment, never the cookie-login gates.
+        if (new Headers(init?.headers).has("authorization")) {
+          return original(input, init);
+        }
+        if (path === "/api/auth/passkeys/login/complete") loginCompleted = true;
+        if (path === "/api/hosting/access") accessRead = true;
         if (path === "/api/auth/whoami") {
-          ++reads;
           if (
-            (phase === "whoami" && reads === 1) ||
-            (phase === "confirmation" && reads === 2)
+            !held && loginCompleted && (
+              (phase === "whoami" && !accessRead) ||
+              (phase === "confirmation" && accessRead)
+            )
           ) {
+            held = true;
             started.resolve();
             return pending.promise;
           }
@@ -357,7 +397,10 @@ for (const phase of ["login", "whoami", "access", "confirmation"] as const) {
           phase === "access"
             ? Response.json({ is_admin: true })
             : phase === "login"
-            ? Response.json({ user: authUser })
+            ? Response.json({
+              user: authUser,
+              authentication_reference: "fixture-authentication",
+            })
             : identityResponse(setupActor),
         );
         await waitFor(() =>
@@ -421,3 +464,154 @@ for (const replacement of [null, replacedActor]) {
     ).toBe(false);
   });
 }
+
+test("setup logout during native login prompt aborts and never submits the late credential", async () => {
+  const { get, fetcher } = boundary();
+  const prompted = gate<void>();
+  const credential = gate<Credential>();
+  get.mockImplementation(() => {
+    prompted.resolve();
+    return credential.promise;
+  });
+  render(Setup);
+  await enroll();
+  await fireEvent.click(
+    await screen.findByRole("button", { name: "Sign in with new passkey" }),
+  );
+  await prompted.promise;
+  await changedInAnotherTab(null);
+  const signal = (get.mock.calls[0] as unknown as [CredentialRequestOptions])[0]
+    .signal!;
+  expect(signal.aborted).toBe(true);
+  credential.resolve(credentialFixture(true));
+  await screen.findByRole("alert");
+  expect(
+    fetcher.mock.calls.some(([path]) =>
+      path === "/api/auth/passkeys/login/complete"
+    ),
+  ).toBe(false);
+  expect(screen.queryByRole("link", { name: "Open hosting settings" }))
+    .toBeNull();
+});
+
+test("setup final confirmation rejects replacement session for the same owner", async () => {
+  const { fetcher } = boundary();
+  const request = fetcher.getMockImplementation()!;
+  let accessRead = false;
+  fetcher.mockImplementation(async (input, init) => {
+    if (String(input) === "/api/hosting/access") accessRead = true;
+    if (String(input) === "/api/auth/whoami" && accessRead) {
+      return Response.json({
+        actor: setupActor,
+        authentication_reference: "same-owner-different-session",
+        session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+      });
+    }
+    return await request(input, init);
+  });
+  render(Setup);
+  await enroll();
+  await fireEvent.click(
+    await screen.findByRole("button", { name: "Sign in with new passkey" }),
+  );
+  await screen.findByRole("alert");
+  expect(screen.queryByRole("link", { name: "Open hosting settings" }))
+    .toBeNull();
+});
+
+for (
+  const phase of [
+    "initial",
+    "options",
+    "prompt",
+    "pre-complete",
+    "complete",
+    "whoami",
+    "access",
+    "confirmation",
+  ] as const
+) {
+  for (const reason of ["logout", "authentication"] as const) {
+    test(`setup fences shared ${reason} stamp during ${phase} before event delivery`, async () => {
+      const { fetcher, get } = boundary();
+      const request = fetcher.getMockImplementation()!;
+      const started = gate<void>();
+      const pending = gate<void>();
+      let optionsRead = false,
+        promptReturned = false,
+        completionSent = false,
+        accessRead = false,
+        held = false;
+      const hold = async () => {
+        held = true;
+        started.resolve();
+        await pending.promise;
+      };
+      get.mockImplementation(async () => {
+        if (phase === "prompt") await hold();
+        promptReturned = true;
+        return credentialFixture(true);
+      });
+      fetcher.mockImplementation(async (input, init) => {
+        if (new Headers(init?.headers).has("authorization")) {
+          return await request(input, init);
+        }
+        const path = String(input);
+        const point = path === "/api/auth/whoami"
+          ? !optionsRead
+            ? "initial"
+            : !completionSent && promptReturned
+            ? "pre-complete"
+            : accessRead
+            ? "confirmation"
+            : "whoami"
+          : path.endsWith("/login/options")
+          ? "options"
+          : path.endsWith("/login/complete")
+          ? "complete"
+          : path === "/api/hosting/access"
+          ? "access"
+          : null;
+        if (point === "options") optionsRead = true;
+        if (point === "complete") completionSent = true;
+        if (point === "access") accessRead = true;
+        const response = await request(input, init);
+        if (!held && point === phase) await hold();
+        return response;
+      });
+      render(Setup);
+      await enroll();
+      await fireEvent.click(
+        await screen.findByRole("button", { name: "Sign in with new passkey" }),
+      );
+      await started.promise;
+      const generation = browserSession.authenticationGeneration;
+      const stamp = JSON.stringify({ id: crypto.randomUUID(), reason });
+      // 同一documentのsetItemはstorage eventを配送しない。generationを直接変えず順序を固定する。
+      localStorage.setItem("yoi.browser-auth-generation", stamp);
+      expect(browserSession.authenticationGeneration).toBe(generation);
+      pending.resolve();
+      await screen.findByRole("alert");
+      await waitFor(() =>
+        expect(
+          (screen.getByRole("button", {
+            name: "Sign in with new passkey",
+          }) as HTMLButtonElement).disabled,
+        ).toBe(false)
+      );
+      expect(
+        fetcher.mock.calls.filter(([path]) =>
+          path === "/api/auth/passkeys/login/complete"
+        ),
+      ).toHaveLength(
+        ["complete", "whoami", "access", "confirmation"].includes(phase)
+          ? 1
+          : 0,
+      );
+      expect(screen.queryByRole("link", { name: "Open hosting settings" }))
+        .toBeNull();
+      // 古いcatchが新tabのstampを自身のsessionMutationで上書きしない。
+      expect(browserSession.authenticationStamp).toBe(stamp);
+    });
+  }
+}
diff --git a/web/workspace/src/routes/login/device/+page.svelte b/web/workspace/src/routes/login/device/+page.svelte
index adfa5a87e..1116496e1 100644
--- a/web/workspace/src/routes/login/device/+page.svelte
+++ b/web/workspace/src/routes/login/device/+page.svelte
@@ -13,11 +13,12 @@
   async function approve() {
     if (auth.busy || !auth.actor || approved || !userCode.trim()) return;
     const code = userCode.trim().toUpperCase();
-    await auth.run('Approving device login…', 'Device login approved. You can return to the CLI.', async (signal) => {
+    const confirmed = await auth.run('Approving device login…', 'Device login approved. You can return to the CLI.', async (signal) => {
       const result = await approveDeviceLogin(code, signal);
       if (result.status !== 'approved') throw new Error('Device approval not confirmed');
-      approved = true;
-    });
+      return result;
+    }, 'device-approval');
+    if (confirmed) approved = true;
   }
   onMount(() => {
     userCode = page.url.searchParams.get('user_code') ?? page.url.searchParams.get('code') ?? '';
diff --git a/web/workspace/src/routes/sidebar-fold.browser.spec.ts b/web/workspace/src/routes/sidebar-fold.browser.spec.ts
index d6f68ba3c..a847f4541 100644
--- a/web/workspace/src/routes/sidebar-fold.browser.spec.ts
+++ b/web/workspace/src/routes/sidebar-fold.browser.spec.ts
@@ -57,7 +57,7 @@ beforeEach(() => {
     "fetch",
     vi.fn(async (input) => {
       if (String(input) === "/api/auth/whoami") {
-        return Response.json({ session: { kind: "anonymous" }, actor: null });
+        return Response.json({ session: { kind: "anonymous" }, authentication_reference: null, actor: null });
       }
       throw new Error(`Unexpected request ${input}`);
     }),
diff --git a/web/workspace/test/activation-browser/fixture-server.ts b/web/workspace/test/activation-browser/fixture-server.ts
index b448f4183..3859f8c7e 100644
--- a/web/workspace/test/activation-browser/fixture-server.ts
+++ b/web/workspace/test/activation-browser/fixture-server.ts
@@ -41,6 +41,7 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
   if (path === "/api/workspaces") return new Response(null, { status: 503 });
   if (path === "/api/auth/whoami") {
     return Response.json({
+      authentication_reference: mode !== "anonymous" ? "fixture-authentication" : null,
       session: mode !== "anonymous"
         ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
         : { kind: "anonymous" },
@@ -89,7 +90,7 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
     if (mode === "activation-unknown") {
       return new Response(null, { status: 503 });
     }
-    return Response.json({ user });
+    return Response.json({ user, authentication_reference: "fixture-authentication" });
   }
   if (path.startsWith("/api/")) return new Response(null, { status: 404 });
   const file = join(root, decodeURIComponent(path));
diff --git a/web/workspace/test/auth-browser/auth-shell.browser.test.ts b/web/workspace/test/auth-browser/auth-shell.browser.test.ts
index bdbe8d5db..5882fe2e2 100644
--- a/web/workspace/test/auth-browser/auth-shell.browser.test.ts
+++ b/web/workspace/test/auth-browser/auth-shell.browser.test.ts
@@ -34,6 +34,11 @@ const register = async (page: Page) => {
   await page.getByRole("button", { name: "Register new account", exact: true })
     .click();
 };
+const additionConfirmed = (page: Page) =>
+  page.getByRole("status").filter({
+    hasText:
+      /^Passkey added to your account; the expected session was confirmed\.$/,
+  });
 const count = (mutations: Mutation[], path: string) =>
   mutations.filter((entry) => entry.path === path).length;
 const at = async (page: Page, path: string) => {
@@ -151,7 +156,7 @@ Deno.test("standalone auth separates login, registration, own account and explic
       readyUrl: `${origin}/health`,
     }],
     `${root}/tools/web-ux/scenarios/anonymous-entry.json`,
-    `${root}/target/web-ux/t767-validation/auth-interactions/processes`,
+    `${root}/target/t783/web-shell-final/processes`,
     [],
   );
   let browser: Browser | undefined;
@@ -229,9 +234,7 @@ Deno.test("standalone auth separates login, registration, own account and explic
               name: "Add passkey to alice",
               exact: true,
             }).click();
-            await page.getByRole("status").filter({
-              hasText: /added|registered/i,
-            }).waitFor();
+            await additionConfirmed(page).waitFor();
             const additions = mutations.filter((entry) =>
               entry.path.includes("/addition/")
             );
@@ -239,7 +242,12 @@ Deno.test("standalone auth separates login, registration, own account and explic
               "/api/auth/passkeys/addition/options",
               "/api/auth/passkeys/addition/complete",
             ]);
-            assertEquals(additions[0].keys, ["browser_origin"]);
+            assertEquals(additions[0].keys, [
+              "browser_origin",
+              "expected_account_id",
+              "expected_authentication_reference",
+              "expected_user_id",
+            ]);
             assertEquals(additions[1].keys, ["challenge_id", "credential"]);
             assertEquals(
               mutations.some((entry) => entry.path.includes("/registration/")),
@@ -357,8 +365,7 @@ Deno.test("standalone auth separates login, registration, own account and explic
               name: "Add passkey to alice",
               exact: true,
             }).click();
-            await page.getByRole("status").filter({ hasText: /added/i })
-              .waitFor();
+            await additionConfirmed(page).waitFor();
             assertEquals(
               count(mutations, "/api/auth/passkeys/addition/complete"),
               1,
@@ -784,9 +791,7 @@ Deno.test("standalone auth separates login, registration, own account and explic
                 .__authFixtureRelease()
             );
             if (purpose === "addition") {
-              await page.getByRole("status").filter({
-                hasText: /added|registered/i,
-              }).waitFor();
+              await additionConfirmed(page).waitFor();
             } else await at(page, "/dashboard");
             assertEquals(
               count(mutations, `/api/auth/passkeys/${purpose}/options`),
@@ -813,8 +818,18 @@ Deno.test("standalone auth separates login, registration, own account and explic
             name: "Approve device login",
             exact: true,
           }).click();
-          await page.getByRole("alert").filter({ hasText: /invalid|expired/i })
-            .waitFor();
+          await page.getByRole("alert").filter({
+            hasText:
+              /^Authentication request was rejected \(400\)\. Check your session or restart the operation\.$/,
+          }).waitFor();
+          assertEquals(new URL(page.url()).pathname, "/login/device");
+          assertEquals(
+            await page.getByText(
+              "Device login approved. You can return to the CLI.",
+              { exact: true },
+            ).count(),
+            0,
+          );
           assertEquals(count(mutations, "/api/auth/device-login/approve"), 1);
         }),
     );
diff --git a/web/workspace/test/auth-browser/entry-shell.browser.test.ts b/web/workspace/test/auth-browser/entry-shell.browser.test.ts
index c1b398692..25d187824 100644
--- a/web/workspace/test/auth-browser/entry-shell.browser.test.ts
+++ b/web/workspace/test/auth-browser/entry-shell.browser.test.ts
@@ -554,7 +554,7 @@ Deno.test("public entry isolates Workspace authority and authenticated dashboard
             },
           );
           await step(
-            "SPA page access checks once without hiding the admitted page",
+            "SPA page access checks once and fences key-list reads without hiding the admitted page",
             async (page) => {
               let checks = 0;
               page.on("request", (request) => {
@@ -582,6 +582,7 @@ Deno.test("public entry isolates Workspace authority and authenticated dashboard
                 await page.getByRole("link", { name: "Account", exact: true })
                   .click();
                 await requested;
+                assertEquals(checks, 2);
                 assertEquals(
                   await page.getByRole("heading", {
                     name: "Dashboard",
@@ -599,7 +600,10 @@ Deno.test("public entry isolates Workspace authority and authenticated dashboard
                   exact: true,
                 }).waitFor();
                 assertEquals(new URL(page.url()).pathname, "/account");
-                assertEquals(checks, 2);
+                await page.getByRole("list", { name: "Registered keys" })
+                  .waitFor();
+                // page入場の一回に加え、本人鍵一覧は読取りの前後で本人bindingを確認する。
+                assertEquals(checks, 4);
               } finally {
                 release();
               }
diff --git a/web/workspace/test/auth-browser/fixture-server.ts b/web/workspace/test/auth-browser/fixture-server.ts
index e156ef458..ed77d0ccd 100644
--- a/web/workspace/test/auth-browser/fixture-server.ts
+++ b/web/workspace/test/auth-browser/fixture-server.ts
@@ -158,9 +158,17 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
       return new Response(null, { status: 503 });
     }
     if (mode === "session-malformed") {
-      return Response.json({ actor: { handle: "untrusted" } });
+      return Response.json({
+        authentication_reference: state.signedIn
+          ? "fixture-authentication"
+          : null,
+        actor: { handle: "untrusted" },
+      });
     }
     return Response.json({
+      authentication_reference: state.signedIn
+        ? "fixture-authentication"
+        : null,
       actor: state.signedIn
         ? { ...user, auth_method: "browser_session" }
         : null,
@@ -168,11 +176,25 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
         ? {
           kind: "authenticated",
           expires_at: state.expiresAt ??
-            new Date(Date.now() + 86_400_000).toISOString(),
+            "2099-01-01T00:00:00Z",
         }
         : { kind: state.expired ? "expired" : "anonymous" },
     });
   }
+  if (path === "/api/auth/passkeys") {
+    return Response.json({
+      user,
+      keys: [{
+        key_reference: "synthetic-safe-key-reference",
+        created_at: "2026-01-01T00:00:00Z",
+        last_used_at: null,
+        normal_login_verified_at: null,
+      }],
+    });
+  }
+  if (path === "/api/auth/passkeys/addition/result") {
+    return Response.json({ status: "unknown" });
+  }
   if (path === "/api/auth/registration-policy") {
     if (mode === "policy-loading") return await new Promise<Response>(() => {});
     if (mode === "policy-error") return new Response(null, { status: 503 });
@@ -227,7 +249,11 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
   }
   if (path === "/api/auth/device-login/approve") {
     if (!state.signedIn) return new Response(null, { status: 401 });
-    if (mode === "device-expired") return new Response(null, { status: 410 });
+    if (mode === "device-expired") {
+      return Response.json({
+        message: "expired_device_login: device login code expired",
+      }, { status: 400 });
+    }
     return Response.json({ status: "approved", user });
   }
   const passkey = path.match(
@@ -263,7 +289,10 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
     state.expired = false;
     state.cookieSession = false;
     state.expiresAt = null;
-    return Response.json({ user });
+    return Response.json({
+      user,
+      authentication_reference: "fixture-authentication",
+    });
   }
   if (path === "/api/auth/activation/options") {
     return Response.json(options(false));
@@ -273,7 +302,10 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
     state.expired = false;
     state.cookieSession = false;
     state.expiresAt = null;
-    return Response.json({ user });
+    return Response.json({
+      user,
+      authentication_reference: "fixture-authentication",
+    });
   }
   // Workspace画面の既存fixtureを再利用する。認証/登録/作成APIの代わりにはしない。
   if (workspaceFixture && path.startsWith("/api/w/")) {
diff --git a/web/workspace/test/auth-browser/passkey-state.browser.test.ts b/web/workspace/test/auth-browser/passkey-state.browser.test.ts
new file mode 100644
index 000000000..964282426
--- /dev/null
+++ b/web/workspace/test/auth-browser/passkey-state.browser.test.ts
@@ -0,0 +1,208 @@
+/// <reference lib="dom" />
+// 本番shellと可視状態の試験。HTTP/認証器を合成fixtureへ置換するため、暗号/保存の成功根拠ではない。
+// native CTAP2 + 実Backend経路はtests/e2eの別suiteが所有する。
+import { assert, assertEquals } from "@std/assert";
+import { resolve } from "@std/path";
+import { type Browser, chromium } from "playwright";
+import {
+  startOwnedProcesses,
+  stopOwnedProcesses,
+} from "../../../../tools/web-ux/src/processes.ts";
+
+Deno.test("account addition keeps pending and recovery visible at desktop and mobile widths", async (t) => {
+  const root = resolve(import.meta.dirname!, "../../../..");
+  const reservation = Deno.listen({ hostname: "127.0.0.1", port: 0 });
+  const port = (reservation.addr as Deno.NetAddr).port;
+  reservation.close();
+  const origin = `http://127.0.0.1:${port}`;
+  const out = `${root}/target/web-ux/t783-after`;
+  const processes = await startOwnedProcesses(
+    [{
+      id: "passkey-state",
+      command: "deno",
+      cwd: root,
+      args: [
+        "run",
+        "--config",
+        "tools/web-ux/deno.json",
+        "--allow-read",
+        "--allow-net",
+        "web/workspace/test/auth-browser/fixture-server.ts",
+        String(port),
+        "web/workspace/build",
+      ],
+      readyUrl: `${origin}/health`,
+    }],
+    `${root}/tools/web-ux/scenarios/anonymous-entry.json`,
+    `${out}/processes`,
+    [],
+  );
+  let browser: Browser | undefined;
+  const records: unknown[] = [];
+  try {
+    browser = await chromium.launch();
+    for (const theme of ["light", "dark"] as const) {
+      for (const width of [1440, 768, 390]) {
+        const passed = await t.step(
+          `${theme}/${width}: visible pending, stop and migration metadata`,
+          async () => {
+            const context = await browser!.newContext({
+              viewport: { width, height: 900 },
+              colorScheme: theme,
+              reducedMotion: "reduce",
+            });
+            try {
+              const page = await context.newPage();
+              page.setDefaultTimeout(5000);
+              const pageErrors: string[] = [];
+              const statuses: number[] = [];
+              const consoleErrors: string[] = [];
+              const requestErrors: string[] = [];
+              page.on(
+                "requestfailed",
+                () => requestErrors.push("request-failed"),
+              );
+              page.on("pageerror", () => pageErrors.push("page-error"));
+              page.on("console", (msg) => {
+                if (msg.type() === "error") {
+                  consoleErrors.push("console-error");
+                }
+              });
+              page.on("response", (response) => {
+                if (response.status() >= 400) statuses.push(response.status());
+              });
+              await context.route(
+                "**/*",
+                (route) =>
+                  new URL(route.request().url()).origin === origin
+                    ? route.continue()
+                    : route.abort(),
+              );
+              await page.request.get(`${origin}/?fixture=addition-pending`);
+              const documentResponse = await page.goto(`${origin}/account`);
+              const add = page.getByRole("button", {
+                name: "Add passkey to alice",
+                exact: true,
+              });
+              await add.waitFor();
+              await page.getByRole("list", { name: "Registered keys" })
+                .waitFor();
+              await page.screenshot({
+                path: `${out}/account-${theme}-${width}.png`,
+                fullPage: true,
+              });
+              await add.click();
+              const pending = page.getByRole("status").filter({
+                hasText: "Waiting for passkey addition",
+              });
+              await pending.waitFor({ state: "visible" });
+              const box = await pending.boundingBox();
+              assert(
+                box && box.y >= 0 && box.y + box.height <= 900,
+                "pending must be in the initial visible viewport",
+              );
+              assertEquals(await add.isDisabled(), true);
+              assertEquals(
+                await page.getByText("Loading session…", { exact: true })
+                  .isVisible(),
+                false,
+              );
+              await page.screenshot({
+                path: `${out}/pending-${theme}-${width}.png`,
+                fullPage: true,
+              });
+              const pendingAccessibility = await page.locator("main")
+                .ariaSnapshot();
+              await page.getByRole("button", {
+                name: "Stop waiting",
+                exact: true,
+              }).click();
+              await page.evaluate(() =>
+                (window as unknown as { __authFixtureRelease: () => void })
+                  .__authFixtureRelease()
+              );
+              await page.getByRole("alert").filter({
+                hasText: "Completion was not sent",
+              }).waitFor();
+              await page.getByRole("button", {
+                name: "Refresh registered keys",
+                exact: true,
+              }).click();
+              await page.getByText(
+                "Not yet verified — storage alone does not prove support",
+                { exact: true },
+              ).waitFor();
+              await page.getByText(
+                "Verify migration before retiring older-key login",
+                { exact: true },
+              ).click();
+              await page.screenshot({
+                path: `${out}/migration-${theme}-${width}.png`,
+                fullPage: true,
+              });
+              assertEquals(
+                await page.evaluate(() =>
+                  document.documentElement.scrollWidth > innerWidth
+                ),
+                false,
+              );
+              assertEquals(documentResponse?.status(), 200);
+              assertEquals(pageErrors, []);
+              assertEquals(consoleErrors, []);
+              assertEquals(statuses, []);
+              assertEquals(requestErrors, []);
+              const images = [];
+              for (
+                const name of [
+                  `account-${theme}-${width}.png`,
+                  `pending-${theme}-${width}.png`,
+                  `migration-${theme}-${width}.png`,
+                ]
+              ) {
+                const digest = await crypto.subtle.digest(
+                  "SHA-256",
+                  await Deno.readFile(`${out}/${name}`),
+                );
+                images.push({
+                  name,
+                  sha256: Array.from(
+                    new Uint8Array(digest),
+                    (byte) => byte.toString(16).padStart(2, "0"),
+                  ).join(""),
+                });
+              }
+              records.push({
+                route: "/account",
+                actor: "synthetic Alice",
+                theme,
+                width,
+                documentStatus: documentResponse?.status(),
+                pageErrors,
+                consoleErrors,
+                requestErrors,
+                statuses,
+                pendingAccessibility,
+                visible: await page.locator("main").innerText(),
+                images,
+              });
+            } finally {
+              await context.close();
+            }
+          },
+        );
+        if (!passed) {
+          throw new Error(
+            "Stop on the first failed visibility condition; investigate before repeating the matrix",
+          );
+        }
+      }
+    }
+  } finally {
+    await browser?.close();
+    await stopOwnedProcesses(processes);
+    await Deno.writeTextFile(
+      `${out}/review-context.json`,
+      JSON.stringify(records, null, 2),
+    );
+  }
+});
diff --git a/web/workspace/test/auth-browser/session-navigation.ts b/web/workspace/test/auth-browser/session-navigation.ts
index 0442b6c79..5999f1cc3 100644
--- a/web/workspace/test/auth-browser/session-navigation.ts
+++ b/web/workspace/test/auth-browser/session-navigation.ts
@@ -239,6 +239,10 @@ export async function sessionNavigation(
           name: "Add passkey to alice",
           exact: true,
         }).waitFor();
+        // Accountの初期metadata確認はwhoamiを前後で読む。完了を可視結果で
+        // 待ち、短命cookieの観測へ初期requestを混入させない。
+        await page.getByRole("list", { name: "Registered keys", exact: true })
+          .waitFor();
         const armed = await control(page, "arm-cookie");
         assert(armed.headers()["set-cookie"].includes("Max-Age=3"));
         const cookie = (await page.context().cookies()).find((c) =>
@@ -361,6 +365,10 @@ export async function sessionNavigation(
       await go("/account?tab=keys#stale", "account");
       await page.getByRole("button", { name: "Log out", exact: true })
         .waitFor();
+      // 保留するのは明示refresh。初期metadata requestは離脱時にabortされる
+      // 別のlifetimeなので、先に完了させる。
+      await page.getByRole("list", { name: "Registered keys", exact: true })
+        .waitFor();
       let started!: () => void;
       let failed!: (error: unknown) => void;
       let release!: () => void;
@@ -433,7 +441,7 @@ export async function sessionNavigation(
     },
   );
   await step(
-    "challenge 401 leaves an authenticated account in place and permits retry",
+    "challenge 401 leaves an authenticated account in place but requires result recovery before another addition",
     async ({ page, go }) => {
       const target = "/account?tab=keys#challenge";
       await go(target, "addition-expired");
@@ -453,7 +461,21 @@ export async function sessionNavigation(
           name: "Add passkey to alice",
           exact: true,
         }).isEnabled(),
-        true,
+        false,
+      );
+      await page.getByRole("button", {
+        name: "Check addition result",
+        exact: true,
+      }).click();
+      await page.getByRole("status").filter({
+        hasText: "addition result is still unknown",
+      }).waitFor();
+      assertEquals(
+        await page.getByRole("button", {
+          name: "Add passkey to alice",
+          exact: true,
+        }).isEnabled(),
+        false,
       );
     },
   );
@@ -466,7 +488,11 @@ export async function sessionNavigation(
       await at(page, "/");
       const wire = await (await page.request.get(`${origin}/api/auth/whoami`))
         .json();
-      assertEquals(wire, { actor: null, session: { kind: "anonymous" } });
+      assertEquals(wire, {
+        actor: null,
+        authentication_reference: null,
+        session: { kind: "anonymous" },
+      });
       await page.evaluate(() => {
         localStorage.clear();
         sessionStorage.clear();
@@ -487,6 +513,9 @@ export async function sessionNavigation(
           name: "Add passkey to alice",
           exact: true,
         }).waitFor();
+        // 初期metadata確認のwhoamiをlifecycle event由来と誤計数しない。
+        await page.getByRole("list", { name: "Registered keys", exact: true })
+          .waitFor();
         await control(page, "expire");
         let checks = 0;
         page.on("request", (request) => {
diff --git a/web/workspace/test/hosting-browser/fixture-server.ts b/web/workspace/test/hosting-browser/fixture-server.ts
index 845556bd7..a7799fcc1 100644
--- a/web/workspace/test/hosting-browser/fixture-server.ts
+++ b/web/workspace/test/hosting-browser/fixture-server.ts
@@ -19,7 +19,7 @@ const mime: Record<string, string> = {
 };
 const policies = new Map<string, boolean>();
 // 各fixture processはscenarioを逐次実行する。setupのBearer-only要求はcookieを
-// 送らないので、秘密やheadersを読まず直前の合成page条件で応答を選ぶ。
+// 送らないので、Bearer有無と直前の合成page条件で応答を選ぶ。header値は読まない。
 let setupMode: string | null = null;
 Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
   const url = new URL(request.url);
@@ -28,19 +28,27 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
   if (url.pathname === "/hosting/setup" && selected?.startsWith("setup-")) {
     setupMode = selected;
   }
+  const tokenRequest = request.headers.has("authorization");
   const mode = selected ??
+    (tokenRequest ? setupMode : null) ??
     request.headers.get("cookie")?.match(/ui-fixture=([\w-]+)/)?.[1] ??
     (url.pathname.startsWith("/api/auth/passkeys/addition/")
       ? setupMode
       : null) ??
     "admin-on";
   if (selected) policies.delete(mode);
-  const setup = setupProjectionResponse(url.pathname, mode, selected !== null);
+  const setup = setupProjectionResponse(
+    url.pathname,
+    mode,
+    selected !== null,
+    tokenRequest,
+  );
   if (setup) return setup;
   const anonymous = mode.startsWith("anonymous") || mode.startsWith("account-");
   const ordinary = mode.startsWith("ordinary");
   if (url.pathname === "/api/auth/whoami") {
     return Response.json({
+      authentication_reference: anonymous ? null : "fixture-authentication",
       session: !anonymous
         ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
         : { kind: "anonymous" },
@@ -53,6 +61,17 @@ Deno.serve({ hostname: "127.0.0.1", port: Number(port) }, async (request) => {
       },
     });
   }
+  if (url.pathname === "/api/auth/passkeys") {
+    return Response.json({
+      user: {
+        user_id: "fixture-user",
+        account_id: "fixture-account",
+        handle: "alice",
+        display_name: "Alice",
+      },
+      keys: [],
+    });
+  }
   if (url.pathname === "/api/workspaces") return Response.json([]);
   if (url.pathname === "/api/hosting/access") {
     return Response.json({ is_admin: !ordinary && !anonymous });
diff --git a/web/workspace/test/hosting-browser/setup-projection.ts b/web/workspace/test/hosting-browser/setup-projection.ts
index bb4b93222..b2e70a465 100644
--- a/web/workspace/test/hosting-browser/setup-projection.ts
+++ b/web/workspace/test/hosting-browser/setup-projection.ts
@@ -19,6 +19,7 @@ export function setupProjectionResponse(
   path: string,
   mode: string,
   reset: boolean,
+  tokenRequest = false,
 ): Response | null {
   if (!mode.startsWith("setup-")) return null;
   if (reset) stages.delete(mode);
@@ -28,7 +29,17 @@ export function setupProjectionResponse(
     });
   }
   if (path === "/api/auth/whoami") {
+    if (tokenRequest) {
+      return Response.json({
+        actor: { ...user, auth_method: "api_token" },
+        authentication_reference: "fixture-token-binding",
+        session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+      });
+    }
     return Response.json({
+      authentication_reference: stages.get(mode) === "login"
+        ? "fixture-authentication"
+        : null,
       session: stages.get(mode) === "login"
         ? { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" }
         : { kind: "anonymous" },
@@ -56,7 +67,10 @@ export function setupProjectionResponse(
   }
   if (path === "/api/auth/passkeys/addition/complete") {
     stages.set(mode, "enrolled");
-    return Response.json({ user });
+    return Response.json({
+      user,
+      authentication_reference: "fixture-authentication",
+    });
   }
   if (path === "/api/auth/passkeys/login/options") {
     return Response.json({
@@ -66,7 +80,10 @@ export function setupProjectionResponse(
   }
   if (path === "/api/auth/passkeys/login/complete") {
     stages.set(mode, "login");
-    return Response.json({ user });
+    return Response.json({
+      user,
+      authentication_reference: "fixture-authentication",
+    });
   }
   return null;
 }
diff --git a/web/workspace/test/spa-shell.test.ts b/web/workspace/test/spa-shell.test.ts
index 646f42817..8afd9b736 100644
--- a/web/workspace/test/spa-shell.test.ts
+++ b/web/workspace/test/spa-shell.test.ts
@@ -26,6 +26,7 @@ Deno.test("authentication and hosting shells never require Workspace catalog aut
           display_name: "Alice",
           auth_method: "browser_session",
         },
+        authentication_reference: "fixture-authentication",
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
       });
     browserSession.invalidate();
@@ -60,6 +61,7 @@ Deno.test("account loads its sidebar catalog without making catalog failure an a
           display_name: "Alice",
           auth_method: "browser_session",
         },
+        authentication_reference: "fixture-authentication",
         session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
       });
     browserSession.invalidate();
@@ -106,7 +108,11 @@ Deno.test("root admission never starts private catalog while anonymous, expired,
         if (condition === "loading") await pending;
         return condition === "error" || condition === "loading"
           ? new Response(null, { status: 503 })
-          : Response.json({ actor: null, session: { kind: condition } });
+          : Response.json({
+            actor: null,
+            authentication_reference: null,
+            session: { kind: condition },
+          });
       };
       let privateCalls = 0;
       const event = {
diff --git a/web/workspace/tests/auth-api.test.ts b/web/workspace/tests/auth-api.test.ts
index c2f9d5630..2663782f7 100644
--- a/web/workspace/tests/auth-api.test.ts
+++ b/web/workspace/tests/auth-api.test.ts
@@ -168,35 +168,62 @@ for (const purpose of ["registration", "addition"] as const) {
     await withBrowserBoundary(async (input, init) => {
       requests.push({ path: String(input), init: init! });
       return Response.json(
-        requests.length === 1 ? registrationOptions : { user: authUser },
+        String(input) === "/api/auth/whoami"
+          ? {
+            actor: { ...authUser, auth_method: "browser_session" },
+            authentication_reference: "fixture-authentication",
+            session: {
+              kind: "authenticated",
+              expires_at: "2099-01-01T00:00:00Z",
+            },
+          }
+          : String(input).endsWith("/options")
+          ? registrationOptions
+          : {
+            user: authUser,
+            authentication_reference: "fixture-authentication",
+          },
       );
     }, async (calls) => {
       const user = purpose === "registration"
         ? await registerPasskey("alice", "Alice")
         : await addPasskey();
-      assertEquals(user, authUser);
+      assertEquals(user, {
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      });
       assertEquals(calls, { create: 1, get: 0 });
     });
     assertEquals(requests.map(({ path }) => path), [
+      ...(purpose === "addition" ? ["/api/auth/whoami"] : []),
       `/api/auth/passkeys/${purpose}/options`,
       `/api/auth/passkeys/${purpose}/complete`,
     ]);
-    for (const { init } of requests) {
-      assertEquals(init.method, "POST");
+    for (const { path, init } of requests) {
+      assertEquals(
+        init.method ?? "GET",
+        path.endsWith("/whoami") ? "GET" : "POST",
+      );
       assertEquals(init.credentials, "same-origin");
       assertEquals(init.headers, { "content-type": "application/json" });
     }
+    const ceremony = requests.filter(({ path }) => !path.endsWith("/whoami"));
     assertEquals(
-      JSON.parse(String(requests[0].init.body)),
+      JSON.parse(String(ceremony[0].init.body)),
       purpose === "registration"
         ? {
           handle: "alice",
           display_name: "Alice",
           browser_origin: "https://yoi.example",
         }
-        : { browser_origin: "https://yoi.example" },
+        : {
+          expected_user_id: authUser.user_id,
+          expected_account_id: authUser.account_id,
+          expected_authentication_reference: "fixture-authentication",
+          browser_origin: "https://yoi.example",
+        },
     );
-    const complete = JSON.parse(String(requests[1].init.body));
+    const complete = JSON.parse(String(ceremony[1].init.body));
     assertEquals(Object.keys(complete).sort(), ["challenge_id", "credential"]);
     assertEquals(complete.challenge_id, registrationOptions.challenge_id);
     assertEquals(complete.credential.response.attestationObject, "AQID");
@@ -208,13 +235,21 @@ Deno.test("addition rejects expired-session completion without falling back to r
   const paths: string[] = [];
   await withBrowserBoundary(async (input) => {
     paths.push(String(input));
-    return paths.length === 1
+    if (String(input).endsWith("/whoami")) {
+      return Response.json({
+        actor: { ...authUser, auth_method: "browser_session" },
+        authentication_reference: "fixture-authentication",
+        session: { kind: "authenticated", expires_at: "2099-01-01T00:00:00Z" },
+      });
+    }
+    return String(input).endsWith("/options")
       ? Response.json(registrationOptions)
       : new Response(null, { status: 401 });
   }, async () => {
-    await assertRejects(addPasskey(), "Auth request failed (401).");
+    await assertRejects(addPasskey(), "Passkey complete: rejected (rejected).");
   });
   assertEquals(paths, [
+    "/api/auth/whoami",
     "/api/auth/passkeys/addition/options",
     "/api/auth/passkeys/addition/complete",
   ]);
@@ -226,7 +261,10 @@ Deno.test("existing-handle registration rejection never starts WebAuthn or retri
     paths.push(String(input));
     return new Response(null, { status: 409 });
   }, async (calls) => {
-    await assertRejects(registerPasskey("alice"), "Auth request failed (409).");
+    await assertRejects(
+      registerPasskey("alice"),
+      "Passkey options: rejected (not-sent).",
+    );
     assertEquals(calls, { create: 0, get: 0 });
   });
   assertEquals(paths, ["/api/auth/passkeys/registration/options"]);
@@ -251,10 +289,16 @@ Deno.test("login sends the explicit trimmed handle and serializes the assertion"
   await withBrowserBoundary(async (input, init) => {
     requests.push({ path: String(input), init: init! });
     return Response.json(
-      requests.length === 1 ? loginOptions : { user: authUser },
+      requests.length === 1 ? loginOptions : {
+        user: authUser,
+        authentication_reference: "fixture-authentication",
+      },
     );
   }, async (calls) => {
-    assertEquals(await loginWithLegacyPasskey(" alice "), authUser);
+    assertEquals(await loginWithLegacyPasskey(" alice "), {
+      user: authUser,
+      authentication_reference: "fixture-authentication",
+    });
     assertEquals(calls, { create: 0, get: 1 });
   });
   assertEquals(requests.map(({ path }) => path), [