feat: migrate protocol and HTTP to structured interface references

T-20: identify interfaces by exact scope/name pairs; add optional opaque scope_ref metadata and separate shape validation from path-dependent scope compatibility. Preserve call error precedence, strict JSON, validators and transport boundaries. Mechanically migrate consumers and document API/wire compatibility and deferred lifecycle semantics.

Validation: cargo fmt --all --check; git diff --check; cargo check --workspace --all-targets; cargo test -p wip-protocol -p wip-http; cargo test --workspace (221 passing tests including doctests); cargo test --workspace --all-targets; nix develop --command cargo clippy --workspace --all-targets -- -D warnings; RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps. All pass. cargo/rustc 1.95.0; development-shell Clippy/rustc 1.97.1.

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 All notable changes to the published WIP Rust crates are documented here.
 
+## Unreleased
+
+- Breaking Protocol/HTTP migration from opaque Interface reference strings to
+  exact `(scope, name)` records in Objects, fetches and calls, with optional
+  opaque `scope_ref` metadata. Adds shape and placement-aware scope validation
+  without changing routes, validators or the wire error-code set.
+- Mechanically migrates workspace consumers and fixtures. See [MIGRATION.md](MIGRATION.md)
+  for API/wire examples and the deferred Host/Client lifecycle semantics.
+
 ## 0.1.0
 
 Initial public release of:

MIGRATION.md

@@ -0,0 +1,130 @@
+# Structured Interface reference migration
+
+This unreleased API/wire change follows `wip-reference` canonical Core Model,
+Protocol and WIP over HTTP at `6086f3c5ef10aa1464ce9c824750d7f667217bfd`.
+It replaces the earlier opaque Interface reference contract; HTTP routes and
+error codes have **not** changed. Peers must upgrade together: the codec does
+not accept legacy strings or display shorthand as Protocol references.
+
+## Rust API
+
+`Object.interfaces` is now `Vec<InterfaceReference>`.
+`FetchInterfaceRequest.interface`, `FetchInterfaceResponse.interface`, and
+`InterfaceTarget.reference` all use the same record:
+
+```rust
+use wip_protocol::{FetchInterfaceRequest, InterfaceReference, InterfaceTarget};
+
+let reference = InterfaceReference {
+    scope: "/github".into(),
+    name: "issue.read".into(),
+};
+reference.validate()?; // reference shape, no target Object path needed
+let fetch = FetchInterfaceRequest { interface: reference.clone() };
+let target = InterfaceTarget {
+    reference,
+    scope_ref: Some("opaque-scope-object-ref".into()),
+    validator: None,
+};
+# Ok::<(), wip_protocol::ValidationError>(())
+```
+
+Construct scope and name explicitly from your Worldspace publication context.
+There is no implicit conversion from a string, delimiter parser, normalization,
+case folding, or URL decoding. A name may contain `/`, `.`, `::`, `#`, or Unicode;
+only an empty name is invalid. Scope must be a canonical absolute Worldspace
+path: `/`, or nonempty slash-separated segments other than `.` and `..`, with
+no empty segments or trailing slash. `%2F` is ordinary field text, not an escape
+for a Worldspace path separator.
+
+Equality, hashing and ordering operate on both fields, independent of member
+order/JSON escape spelling. Use the record itself as a membership/cache key;
+identical names in different scopes are different references. The descriptor
+still contains only format, documentation, types and operations, not identity.
+
+`FetchInterfaceResponse` and `InterfaceTarget` additionally require the Rust
+field `scope_ref: Option<String>` in struct literals. Use `None` when omitted,
+not an invented identity. This is an opaque scope Object ref observation/call
+precondition, **not** a third Interface identity component or a validator.
+The scope-ref lifecycle/atomic Host enforcement and Client cache-recovery
+semantics are follow-up work (T-21/T-22); this migration supplies the data model
+and codec, not a completed lifecycle implementation.
+
+## Validation boundaries
+
+- `InterfaceReference::validate()` and `FetchInterfaceRequest::validate()`
+  check reference shape independently of a target Object path.
+- `Object::validate()` checks shape and duplicate `(scope, name)` pairs;
+  `Object::validate_at_path()` additionally checks placement, including scope.
+  `ObserveRequest::validate_response()` checks every derived node path,
+  including the depth boundary. Invalid success responses are Client-local
+  `InvalidResponse`, not Host-returned Protocol errors.
+- `InterfaceReference::validate_for_path(path)` checks ancestor-or-self scope
+  compatibility by path segments. Root and self scope are valid; `/a` is not
+  an ancestor of `/ab`. This has no indexability dependency.
+- `CallOperationRequest::validate()` checks descriptor-independent shape.
+  `validate_with()` adds operation/argument checks but does not replace Host
+  publication lookup. Host interface selection checks scope compatibility and
+  exact membership **after** target lookup: invalid reference shape is
+  `InvalidRequest`, but a valid reference outside the target's scope is
+  `InterfaceMismatch`, with `NotFound` retaining precedence.
+
+## HTTP wire
+
+All four reference positions use an exact object with required string fields:
+
+```json
+{"scope":"/github","name":"issue.read"}
+```
+
+For example:
+
+```json
+{
+  "interface": {"scope":"/github","name":"issue.read"},
+  "scope_ref": "opaque-scope-object-ref",
+  "descriptor": {"format":"wip-interface/1","types":[],"operations":[]}
+}
+```
+
+A call uses:
+
+```json
+{
+  "target": {"path":"/github/issues/123"},
+  "interface": {
+    "reference": {"scope":"/github","name":"issue.read"},
+    "scope_ref": "opaque-scope-object-ref"
+  },
+  "operation":"refresh",
+  "arguments":{}
+}
+```
+
+Unknown/duplicate members, missing fields, null fields, relative scopes, empty
+names, legacy `"interface-v1"` and shorthand `"/github::issue.read"` strings
+are rejected. Field order and JSON escaping do not affect decoded identity.
+`scope_ref` is a normal opaque string, **not Base64**; omission is allowed but
+explicit null and nonstrings are invalid. An empty string is a valid opaque
+ref. Validators remain canonical padded standard Base64.
+
+Descriptor-independent HTTP call metadata decoding enforces reference shape
+and the same strict JSON rules without turning scope compatibility into early
+`InvalidRequest`. Normal descriptor-bound encode/decode uses the same reference
+codec. Request violations retain the existing `400 invalid_request` boundary;
+malformed success responses retain Client-local `InvalidResponse`. Standard
+`POST v1/observe`, `v1/fetch_interface`, `v1/call_operation`, error-code/status
+mapping and Transport failure classification are unchanged.
+
+## Downstream status
+
+The workspace Client, Host, filesystem server, TUI and public-API example
+are mechanically migrated to structured protocol values and updated fixtures.
+The existing Host's generated opaque registration handle is bridged explicitly
+to scope `/` with its full handle as the name; no delimiter parsing or scope
+registration/lifetime model is introduced here. The existing Client keys use
+structured values; this change does not implement scope deletion/replacement
+cache recovery. TUI formatting is only the type-compatibility adaptation, not
+the full canonical Text View work (T-24). Filesystem/TUI semantics integration
+remains T-23. Interface authoring/macros are descriptor-only and require no
+identity fields or declaration changes.

README.md

@@ -79,6 +79,13 @@ maps standard routes/envelopes to `CallOperationRequest` and
 `CallOperationResponse` without placing transport-specific types in descriptors
 or application traits.
 
+## Structured Interface references
+
+The unreleased Protocol/HTTP API uses explicit `InterfaceReference { scope,
+name }` records and optional `scope_ref` observation/precondition metadata.
+Legacy opaque-string wire references are rejected. See [MIGRATION.md](MIGRATION.md)
+for construction examples, validation boundaries and downstream migration status.
+
 ## End-to-end example
 
 [`crates/wip-public-api-example/src/lib.rs`](crates/wip-public-api-example/src/lib.rs)
@@ -91,7 +98,7 @@ runs it. It demonstrates all of the following:
 2. two public traits declared with `#[wip::interface]`;
 3. a private host struct implementing both traits;
 4. explicit publication of both interfaces as an ordered set on one object;
-5. separate observation of opaque interface references, descriptors, and
+5. separate observation of structured interface references, descriptors, and
    descriptor validators;
 6. calls qualified by `target.path`, object validator, interface reference and
    validator, operation, and schema-neutral `Value` arguments;

crates/wip-client/README.md

@@ -11,6 +11,8 @@ wip-client = "0.1.0"
 
 Applications provide the HTTP adapter and presentation layer, send each prepared request exactly as owned by the runtime, then return the corresponding response for completion.
 
+Interface acquisition and call APIs use `wip_protocol::InterfaceReference { scope, name }` directly. Interface caches and Object membership compare the complete structured value, so equal names in different scopes remain distinct. Interface observations retain the optional `scope_ref`, and calls copy it into `InterfaceTarget` unchanged. Scope-identity recovery is not implemented by this mechanical migration.
+
 See the [API documentation](https://docs.rs/wip-client) for session, acquisition, cache, and call APIs.
 
 Licensed under either of Apache-2.0 or MIT at your option.

crates/wip-client/src/lib.rs

@@ -21,8 +21,8 @@ use wip_http::{
 };
 use wip_protocol::{
     CallOperationRequest, CallOperationResponse, FetchInterfaceRequest, InterfaceDescriptor,
-    InterfaceTarget, Object, ObjectObservation as ProtocolObjectObservation, ObserveRequest,
-    OperationDeclaration, ProtocolError, ProtocolErrorCode, Target, Value,
+    InterfaceReference, InterfaceTarget, Object, ObjectObservation as ProtocolObjectObservation,
+    ObserveRequest, OperationDeclaration, ProtocolError, ProtocolErrorCode, Target, Value,
 };
 
 /// Monotonic identity assigned to one logical request.
@@ -226,12 +226,14 @@ pub struct TreeObservation {
 /// Cached interface descriptor observation.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InterfaceObservation {
-    /// Opaque interface reference.
-    pub reference: String,
+    /// Structured interface reference.
+    pub reference: InterfaceReference,
     /// Last accepted descriptor, if one has been received.
     pub descriptor: Option<InterfaceDescriptor>,
     /// Optional interface validator. Absence makes the reference immutable.
     pub validator: Option<Vec<u8>>,
+    /// Optional opaque identity of the interface scope Object.
+    pub scope_ref: Option<String>,
     /// Current observation lifecycle.
     pub state: ObservationState,
 }
@@ -404,7 +406,7 @@ struct Session {
     objects: BTreeMap<u64, ObjectRecord>,
     refs: BTreeMap<String, u64>,
     trees: BTreeMap<String, TreeObservation>,
-    interfaces: BTreeMap<String, InterfaceRecord>,
+    interfaces: BTreeMap<InterfaceReference, InterfaceRecord>,
     calls: VecDeque<CallRecord>,
     diagnostics: VecDeque<Diagnostic>,
     next_object_key: u64,
@@ -596,7 +598,11 @@ impl Client {
 
     /// Returns the current interface observation.
     #[must_use]
-    pub fn interface(&self, session: &SessionId, reference: &str) -> Option<&InterfaceObservation> {
+    pub fn interface(
+        &self,
+        session: &SessionId,
+        reference: &InterfaceReference,
+    ) -> Option<&InterfaceObservation> {
         self.sessions
             .get(session)?
             .interfaces
@@ -762,9 +768,8 @@ impl Client {
     pub fn ensure_interface(
         &mut self,
         session: &SessionId,
-        reference: impl Into<String>,
+        reference: InterfaceReference,
     ) -> Result<Option<PreparedRequest>, ClientError> {
-        let reference = reference.into();
         let state = self.session(session)?;
         if state.interfaces.contains_key(&reference)
             || state.interfaces.len() >= self.limits.interfaces_per_session
@@ -782,11 +787,11 @@ impl Client {
     pub fn prepare_interface(
         &mut self,
         session: &SessionId,
-        reference: impl Into<String>,
+        reference: InterfaceReference,
     ) -> Result<PreparedRequest, ClientError> {
         self.ensure_capacity()?;
         let request = FetchInterfaceRequest {
-            interface: reference.into(),
+            interface: reference,
         };
         let endpoint = session_endpoint(session)?;
         let encoded = encode_fetch_interface_request(&endpoint, &request, self.wire_limits)
@@ -804,6 +809,7 @@ impl Client {
             .or_insert(InterfaceRecord {
                 observation: InterfaceObservation {
                     reference: request.interface.clone(),
+                    scope_ref: None,
                     descriptor: None,
                     validator: None,
                     state: ObservationState::Loading(id),
@@ -833,7 +839,7 @@ impl Client {
         &mut self,
         session: &SessionId,
         path: &str,
-        interface: &str,
+        interface: &InterfaceReference,
         operation: impl Into<String>,
         arguments: BTreeMap<String, Value>,
     ) -> Result<PreparedRequest, ClientError> {
@@ -900,7 +906,8 @@ impl Client {
                     validator: object.validator.clone(),
                 },
                 interface: InterfaceTarget {
-                    reference: interface.to_owned(),
+                    reference: interface.clone(),
+                    scope_ref: interface_observation.scope_ref.clone(),
                     validator: interface_observation.validator.clone(),
                 },
                 operation,
@@ -1182,6 +1189,7 @@ impl Client {
                 let touched = state.tick();
                 let observation = InterfaceObservation {
                     reference: value.interface,
+                    scope_ref: value.scope_ref,
                     descriptor: Some(value.descriptor),
                     validator: value.validator,
                     state: ObservationState::Fresh,
@@ -1466,7 +1474,7 @@ impl Client {
     fn interface_request_is_current(
         &self,
         session: &SessionId,
-        reference: &str,
+        reference: &InterfaceReference,
         id: RequestId,
     ) -> bool {
         matches!(
@@ -1511,7 +1519,7 @@ impl Client {
 #[derive(Debug)]
 enum RetrievalSubject {
     Observe(ObserveRequest),
-    Interface(String),
+    Interface(InterfaceReference),
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -1617,7 +1625,7 @@ fn set_observe_subject_state(
 
 fn ensure_interface_slot(
     state: &mut Session,
-    reference: &str,
+    reference: &InterfaceReference,
     maximum: usize,
 ) -> Result<(), ClientError> {
     if state.interfaces.contains_key(reference) || state.interfaces.len() < maximum {

crates/wip-client/tests/adapter.rs

@@ -1,3 +1,10 @@
+fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+    wip_protocol::InterfaceReference {
+        scope: "/".into(),
+        name: name.into(),
+    }
+}
+
 use std::collections::BTreeMap;
 
 use wip_client::{
@@ -39,7 +46,7 @@ fn object() -> Object {
     Object {
         name: "item".into(),
         description: None,
-        interfaces: vec!["math".into()],
+        interfaces: vec![root_reference("math")],
         r#ref: None,
         validator: Some(b"object-v1".to_vec()),
     }
@@ -72,7 +79,7 @@ fn malformed_json_unknown_fields_duplicates_and_invalid_success_are_invalid_resp
     let cases: &[&[u8]] = &[
         b"{not json",
         br#"{"name":"item","interfaces":[],"unknown":true}"#,
-        br#"{"name":"item","interfaces":["math","math"]}"#,
+        br#"{"name":"item","interfaces":[{"scope":"/","name":"math"},{"scope":"/","name":"math"}]}"#,
         br#"{"name":"wrong","interfaces":[]}"#,
     ];
     for body in cases {
@@ -181,12 +188,15 @@ fn non_success_without_valid_envelope_remains_transport_failure() {
 #[test]
 fn unsupported_descriptor_format_is_distinct_from_invalid_response() {
     let (mut client, session) = setup();
-    let request = client.prepare_interface(&session, "math").unwrap();
+    let request = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
     let logical = FetchInterfaceRequest {
-        interface: "math".into(),
+        interface: root_reference("math"),
     };
     let value = FetchInterfaceResponse {
-        interface: "math".into(),
+        scope_ref: None,
+        interface: root_reference("math"),
         descriptor: descriptor("future-format/2"),
         validator: Some(b"v2".to_vec()),
     };
@@ -216,16 +226,19 @@ fn malformed_call_success_after_dispatch_is_outcome_unknown_and_stales_object()
             .unwrap(),
         )
         .unwrap();
-    let interface = client.prepare_interface(&session, "math").unwrap();
+    let interface = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
     client
         .complete(
             interface.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &FetchInterfaceResponse {
-                    interface: "math".into(),
+                    scope_ref: None,
+                    interface: root_reference("math"),
                     descriptor: descriptor(INTERFACE_FORMAT_V1),
                     validator: None,
                 },
@@ -238,7 +251,7 @@ fn malformed_call_success_after_dispatch_is_outcome_unknown_and_stales_object()
         .prepare_call(
             &session,
             "/item",
-            "math",
+            &root_reference("math"),
             "calculate",
             BTreeMap::from([("value".into(), Value::Integer(2))]),
         )
@@ -293,16 +306,19 @@ fn plain_413_after_call_dispatch_is_unknown_transport_outcome() {
             .unwrap(),
         )
         .unwrap();
-    let interface = client.prepare_interface(&session, "math").unwrap();
+    let interface = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
     client
         .complete(
             interface.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &FetchInterfaceResponse {
-                    interface: "math".into(),
+                    scope_ref: None,
+                    interface: root_reference("math"),
                     descriptor: descriptor(INTERFACE_FORMAT_V1),
                     validator: None,
                 },
@@ -315,7 +331,7 @@ fn plain_413_after_call_dispatch_is_unknown_transport_outcome() {
         .prepare_call(
             &session,
             "/item",
-            "math",
+            &root_reference("math"),
             "calculate",
             BTreeMap::from([("value".into(), Value::Integer(2))]),
         )

crates/wip-client/tests/runtime.rs

@@ -1,3 +1,10 @@
+fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+    wip_protocol::InterfaceReference {
+        scope: "/".into(),
+        name: name.into(),
+    }
+}
+
 use std::collections::BTreeMap;
 
 use wip_client::{
@@ -65,7 +72,7 @@ fn object(name: &str, reference: Option<&str>, validator: &[u8]) -> Object {
     Object {
         name: name.into(),
         description: Some(format!("object {name}")),
-        interfaces: vec!["math".into()],
+        interfaces: vec![root_reference("math")],
         r#ref: reference.map(str::to_owned),
         validator: Some(validator.to_vec()),
     }
@@ -296,12 +303,18 @@ fn ensure_interface_deduplicates_loading_fresh_and_retained_failure() {
         .unwrap();
 
     let request = client
-        .ensure_interface(&session, "math")
+        .ensure_interface(&session, root_reference("math"))
         .unwrap()
         .expect("missing descriptor starts a fetch");
-    assert!(client.ensure_interface(&session, "math").unwrap().is_none());
+    assert!(
+        client
+            .ensure_interface(&session, root_reference("math"))
+            .unwrap()
+            .is_none()
+    );
     let value = FetchInterfaceResponse {
-        interface: "math".into(),
+        scope_ref: None,
+        interface: root_reference("math"),
         descriptor: descriptor(TypeExpr::Integer),
         validator: Some(b"math-v1".to_vec()),
     };
@@ -310,7 +323,7 @@ fn ensure_interface_deduplicates_loading_fresh_and_retained_failure() {
             request.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &value,
                 wire_limits(),
@@ -318,10 +331,15 @@ fn ensure_interface_deduplicates_loading_fresh_and_retained_failure() {
             .unwrap(),
         )
         .unwrap();
-    assert!(client.ensure_interface(&session, "math").unwrap().is_none());
+    assert!(
+        client
+            .ensure_interface(&session, root_reference("math"))
+            .unwrap()
+            .is_none()
+    );
 
     let failed = client
-        .ensure_interface(&session, "broken")
+        .ensure_interface(&session, root_reference("broken"))
         .unwrap()
         .expect("new descriptor starts a fetch");
     assert_eq!(
@@ -333,7 +351,7 @@ fn ensure_interface_deduplicates_loading_fresh_and_retained_failure() {
     );
     assert!(
         client
-            .ensure_interface(&session, "broken")
+            .ensure_interface(&session, root_reference("broken"))
             .unwrap()
             .is_none(),
         "retained interface failures require an explicit refresh"
@@ -348,7 +366,10 @@ fn ensure_interface_waits_for_request_and_cache_capacity_without_evicting() {
         .unwrap();
     let pending_object = client.refresh_object(&session, "/busy").unwrap();
     assert!(
-        client.ensure_interface(&session, "math").unwrap().is_none(),
+        client
+            .ensure_interface(&session, root_reference("math"))
+            .unwrap()
+            .is_none(),
         "lookahead waits while the in-flight bound is full"
     );
     client
@@ -359,11 +380,12 @@ fn ensure_interface_waits_for_request_and_cache_capacity_without_evicting() {
         .unwrap();
 
     let request = client
-        .ensure_interface(&session, "math")
+        .ensure_interface(&session, root_reference("math"))
         .unwrap()
         .expect("lookahead resumes after capacity becomes available");
     let value = FetchInterfaceResponse {
-        interface: "math".into(),
+        scope_ref: None,
+        interface: root_reference("math"),
         descriptor: descriptor(TypeExpr::Integer),
         validator: None,
     };
@@ -372,7 +394,7 @@ fn ensure_interface_waits_for_request_and_cache_capacity_without_evicting() {
             request.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &value,
                 wire_limits(),
@@ -383,18 +405,32 @@ fn ensure_interface_waits_for_request_and_cache_capacity_without_evicting() {
 
     assert!(
         client
-            .ensure_interface(&session, "other")
+            .ensure_interface(&session, root_reference("other"))
             .unwrap()
             .is_none(),
         "lookahead does not churn a full descriptor cache"
     );
-    assert!(client.interface(&session, "math").is_some());
-    assert!(client.interface(&session, "other").is_none());
+    assert!(
+        client
+            .interface(&session, &root_reference("math"))
+            .is_some()
+    );
+    assert!(
+        client
+            .interface(&session, &root_reference("other"))
+            .is_none()
+    );
 
-    let explicit = client.prepare_interface(&session, "other").unwrap();
-    assert!(client.interface(&session, "math").is_none());
+    let explicit = client
+        .prepare_interface(&session, root_reference("other"))
+        .unwrap();
+    assert!(
+        client
+            .interface(&session, &root_reference("math"))
+            .is_none()
+    );
     assert!(matches!(
-        client.interface(&session, "other").unwrap().state,
+        client.interface(&session, &root_reference("other")).unwrap().state,
         ObservationState::Loading(id) if id == explicit.id
     ));
 }
@@ -408,7 +444,9 @@ fn independent_retrievals_run_concurrently_and_complete_out_of_order() {
 
     let first = client.refresh_observed(&session, "/one", 0).unwrap();
     let second = client.refresh_observed(&session, "/two", 0).unwrap();
-    let interface = client.prepare_interface(&session, "math").unwrap();
+    let interface = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
 
     assert_eq!(first.request.uri().path(), "/wip/v1/observe");
     assert_eq!(second.request.uri().path(), "/wip/v1/observe");
@@ -426,10 +464,11 @@ fn independent_retrievals_run_concurrently_and_complete_out_of_order() {
             interface.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &FetchInterfaceResponse {
-                    interface: "math".into(),
+                    scope_ref: None,
+                    interface: root_reference("math"),
                     descriptor: descriptor(TypeExpr::Integer),
                     validator: Some(b"math-v1".to_vec()),
                 },
@@ -454,7 +493,10 @@ fn independent_retrievals_run_concurrently_and_complete_out_of_order() {
         ObservationState::Fresh
     );
     assert_eq!(
-        client.interface(&session, "math").unwrap().state,
+        client
+            .interface(&session, &root_reference("math"))
+            .unwrap()
+            .state,
         ObservationState::Fresh
     );
     assert_eq!(client.in_flight_len(), 0);
@@ -941,14 +983,21 @@ fn call_context_fixes_membership_validators_descriptor_and_result_validation() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: Some(b"interface-v1".to_vec()),
         },
     );
 
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(7))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(7),
+        )
         .unwrap();
     assert_eq!(
         client
@@ -965,7 +1014,8 @@ fn call_context_fixes_membership_validators_descriptor_and_result_validation() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::String),
             validator: Some(b"interface-v2".to_vec()),
         },
@@ -981,7 +1031,8 @@ fn call_context_fixes_membership_validators_descriptor_and_result_validation() {
                         validator: Some(b"object-v1".to_vec()),
                     },
                     interface: wip_protocol::InterfaceTarget {
-                        reference: "math".into(),
+                        scope_ref: None,
+                        reference: root_reference("math"),
                         validator: Some(b"interface-v1".to_vec()),
                     },
                     operation: "calculate".into(),
@@ -1015,7 +1066,10 @@ fn call_context_fixes_membership_validators_descriptor_and_result_validation() {
     );
     assert!(matches!(history_context.outcome, CallOutcome::Success(_)));
     assert_eq!(
-        client.interface(&session, "math").unwrap().descriptor,
+        client
+            .interface(&session, &root_reference("math"))
+            .unwrap()
+            .descriptor,
         Some(descriptor(TypeExpr::String))
     );
     let observation = client.object(&session, "/item").unwrap();
@@ -1039,14 +1093,21 @@ fn successful_call_without_validator_preserves_observed_validator() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: None,
         },
     );
 
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(1))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(1),
+        )
         .unwrap();
     let request = client
         .pending_call_context(call.id)
@@ -1080,7 +1141,13 @@ fn successful_call_without_validator_preserves_observed_validator() {
     assert_eq!(observation.validator, Some(b"object-v1".to_vec()));
 
     let next = client
-        .prepare_call(&session, "/item", "math", "calculate", args(2))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(2),
+        )
         .unwrap();
     assert_eq!(
         client
@@ -1109,14 +1176,21 @@ fn newer_observation_prevents_older_success_validator_overwrite() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: None,
         },
     );
 
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(1))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(1),
+        )
         .unwrap();
     let request = client
         .pending_call_context(call.id)
@@ -1173,7 +1247,8 @@ fn older_retrieval_cannot_overwrite_success_validator() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: Some(b"interface-v1".to_vec()),
         },
@@ -1181,7 +1256,13 @@ fn older_retrieval_cannot_overwrite_success_validator() {
 
     let older_alias = client.refresh_observed(&session, "/alias/item", 0).unwrap();
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(7))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(7),
+        )
         .unwrap();
     let request = client
         .pending_call_context(call.id)
@@ -1227,7 +1308,13 @@ fn older_retrieval_cannot_overwrite_success_validator() {
     assert_eq!(alias.validator, Some(b"object-v2".to_vec()));
     assert_eq!(
         client
-            .prepare_call(&session, "/alias/item", "math", "calculate", args(1))
+            .prepare_call(
+                &session,
+                "/alias/item",
+                &root_reference("math"),
+                "calculate",
+                args(1)
+            )
             .unwrap_err()
             .kind,
         ClientErrorKind::MissingObservation
@@ -1243,7 +1330,13 @@ fn older_retrieval_cannot_overwrite_success_validator() {
         .refresh_observed(&session, "/second/item", 0)
         .unwrap();
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(8))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(8),
+        )
         .unwrap();
     client.mark_dispatched(call.id).unwrap();
     let unknown = ProtocolError {
@@ -1292,13 +1385,20 @@ fn in_flight_calls_pin_target_identity_until_staleness_is_applied() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: Some(b"interface-v1".to_vec()),
         },
     );
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(7))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(7),
+        )
         .unwrap();
     client.mark_dispatched(call.id).unwrap();
 
@@ -1350,13 +1450,20 @@ fn validator_mismatch_stales_only_its_observation_and_never_retries() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: Some(b"i1".to_vec()),
         },
     );
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(1))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(1),
+        )
         .unwrap();
     client.mark_dispatched(call.id).unwrap();
     let error = ProtocolError {
@@ -1369,7 +1476,10 @@ fn validator_mismatch_stales_only_its_observation_and_never_retries() {
     client.complete(call.id, response).unwrap();
 
     assert_eq!(
-        client.interface(&session, "math").unwrap().state,
+        client
+            .interface(&session, &root_reference("math"))
+            .unwrap()
+            .state,
         ObservationState::Stale
     );
     assert_eq!(
@@ -1384,7 +1494,8 @@ fn validator_mismatch_stales_only_its_observation_and_never_retries() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: Some(b"i2".to_vec()),
         },
@@ -1404,14 +1515,21 @@ fn protocol_and_transport_unknown_outcomes_stale_without_retry() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: None,
         },
     );
 
     let call = client
-        .prepare_call(&session, "/item", "math", "calculate", args(1))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(1),
+        )
         .unwrap();
     client.mark_dispatched(call.id).unwrap();
     let unknown = ProtocolError {
@@ -1447,7 +1565,13 @@ fn protocol_and_transport_unknown_outcomes_stale_without_retry() {
 
     observe_object(&mut client, &session, "/item", object("item", None, b"v2"));
     let second = client
-        .prepare_call(&session, "/item", "math", "calculate", args(2))
+        .prepare_call(
+            &session,
+            "/item",
+            &root_reference("math"),
+            "calculate",
+            args(2),
+        )
         .unwrap();
     client.mark_dispatched(second.id).unwrap();
     let completion = client
@@ -1695,8 +1819,12 @@ fn superseded_transport_failure_does_not_poison_newer_refresh() {
         )
         .unwrap();
 
-    let old = client.prepare_interface(&session, "math").unwrap();
-    let newer = client.prepare_interface(&session, "math").unwrap();
+    let old = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
+    let newer = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
     assert_eq!(
         client
             .fail_transport(old.id, "old connection failed")
@@ -1704,11 +1832,12 @@ fn superseded_transport_failure_does_not_poison_newer_refresh() {
         Completion::StaleResponseRejected(old.id)
     );
     assert!(matches!(
-        client.interface(&session, "math").unwrap().state,
+        client.interface(&session, &root_reference("math")).unwrap().state,
         ObservationState::Loading(id) if id == newer.id
     ));
     let value = FetchInterfaceResponse {
-        interface: "math".into(),
+        scope_ref: None,
+        interface: root_reference("math"),
         descriptor: descriptor(TypeExpr::Integer),
         validator: Some(b"current".to_vec()),
     };
@@ -1717,7 +1846,7 @@ fn superseded_transport_failure_does_not_poison_newer_refresh() {
             newer.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &value,
                 wire_limits(),
@@ -1737,15 +1866,19 @@ fn validator_free_interface_observation_remains_immutable() {
         &mut client,
         &session,
         FetchInterfaceResponse {
-            interface: "math".into(),
+            scope_ref: None,
+            interface: root_reference("math"),
             descriptor: descriptor(TypeExpr::Integer),
             validator: None,
         },
     );
 
-    let refresh = client.prepare_interface(&session, "math").unwrap();
+    let refresh = client
+        .prepare_interface(&session, root_reference("math"))
+        .unwrap();
     let contradictory = FetchInterfaceResponse {
-        interface: "math".into(),
+        scope_ref: None,
+        interface: root_reference("math"),
         descriptor: descriptor(TypeExpr::Integer),
         validator: Some(b"became-mutable".to_vec()),
     };
@@ -1754,7 +1887,7 @@ fn validator_free_interface_observation_remains_immutable() {
             refresh.id,
             encode_fetch_interface_response(
                 &FetchInterfaceRequest {
-                    interface: "math".into(),
+                    interface: root_reference("math"),
                 },
                 &contradictory,
                 wire_limits(),
@@ -1763,7 +1896,13 @@ fn validator_free_interface_observation_remains_immutable() {
         )
         .unwrap_err();
     assert_eq!(error.kind, ClientErrorKind::InvalidResponse);
-    assert_eq!(client.interface(&session, "math").unwrap().validator, None);
+    assert_eq!(
+        client
+            .interface(&session, &root_reference("math"))
+            .unwrap()
+            .validator,
+        None
+    );
 }
 
 #[test]
@@ -1876,3 +2015,64 @@ fn in_flight_and_history_are_bounded() {
         .unwrap_err();
     assert_eq!(client.diagnostics(&session).unwrap().len(), 1);
 }
+
+#[test]
+fn structured_interface_keys_membership_and_scope_ref_are_preserved() {
+    let mut client = client(8, 8, 8, 8);
+    let session = client
+        .open_session("https://example.test/wip", SecurityContext::new("subject"))
+        .unwrap();
+    let root = root_reference("same#::操作");
+    let local = wip_protocol::InterfaceReference {
+        scope: "/item".into(),
+        name: root.name.clone(),
+    };
+    let mut value = object("item", None, b"object-v1");
+    value.interfaces = vec![local.clone()];
+    observe_object(&mut client, &session, "/item", value);
+    for (reference, scope_ref) in [
+        (root.clone(), None),
+        (local.clone(), Some("scope-identity".into())),
+    ] {
+        observe_interface(
+            &mut client,
+            &session,
+            FetchInterfaceResponse {
+                interface: reference,
+                descriptor: descriptor(TypeExpr::Integer),
+                scope_ref,
+                validator: None,
+            },
+        );
+    }
+    assert!(client.interface(&session, &root).is_some());
+    assert_eq!(
+        client
+            .interface(&session, &local)
+            .unwrap()
+            .scope_ref
+            .as_deref(),
+        Some("scope-identity")
+    );
+    assert_eq!(
+        client
+            .prepare_call(&session, "/item", &root, "calculate", args(1))
+            .unwrap_err()
+            .kind,
+        ClientErrorKind::InvalidRequest
+    );
+    let call = client
+        .prepare_call(&session, "/item", &local, "calculate", args(1))
+        .unwrap();
+    let context = client.pending_call_context(call.id).unwrap();
+    assert_eq!(context.request().interface.reference, local);
+    assert_eq!(
+        context.request().interface.scope_ref.as_deref(),
+        Some("scope-identity")
+    );
+    assert_eq!(
+        context.interface().scope_ref.as_deref(),
+        Some("scope-identity")
+    );
+    assert_eq!(client.interface(&session, &root).unwrap().scope_ref, None);
+}

crates/wip-fs-server/README.md

@@ -23,8 +23,9 @@ For an external backend/composition:
 
 1. Implement `BackendEntry` on a local, cloneable, root-confined stable capability.
    Its `WipObject` metadata is public-only; its validator binds identity and the
-   protected state. Implement `FilesystemBackend` to resolve capabilities,
-   enumerate bounded children, and execute against an already-resolved entry.
+   protected state. Implement `FilesystemBackend` to resolve one connected
+   `ResolvedEntry<Entry>` (root-to-parent ancestry plus pinned target), enumerate
+   bounded children, and execute against that already-resolved lineage.
 2. Register generated `#[wip_interface::interface]` definitions using the existing
    `wip_host::InterfaceRegistry`. `DefaultInterfaces::register` optionally supplies
    reusable built-in tokens; using those tokens does not force their publication.
@@ -55,10 +56,26 @@ listener, a global object registry, or dynamic plugin loading.
 ### Extension security contract
 
 Backend implementations and Operation authors are trusted code, not sandboxed
-plugins. `FilesystemBackend::execute` must refresh state/validators **inside** its
-transaction or lock before calling the engine callback, retain the same resolved
-target through validation and dispatch, and return the committed post-operation
-validator. Confirm rollback only after rollback succeeds. Pre-dispatch failures
+plugins. `FilesystemBackend::resolve` returns `ResolvedEntry::new(ancestors, target)`
+from one connected backend traversal/snapshot, not independent path-prefix
+resolutions. A root target has no ancestors; other targets retain the root first,
+then intermediate parent containers. This is backend-private context, never wire
+metadata. Backend `resolve` and `execute` signatures both carry this type;
+compositions still receive only the exact scoped target `Entry`.
+
+`FilesystemBackend::execute` must validate ancestor membership/identity and
+refresh **all** lineage state/validators inside its transaction or lock before
+calling the engine callback, retaining the same target and connected ancestry
+through validation and dispatch. Replaced/detached ancestors must return
+`NotFound` without callback invocation, even when the replacement is visible.
+The engine evaluates Object visibility for every refreshed ancestor and target
+inside that same boundary; a hidden ancestor rejects the entire subtree before
+publication/typed dispatch. Never fix a changed lineage by resolving the raw path
+again and substituting capabilities. Participating policy-relevant backend state
+changes must be serialized by this boundary, not just target-content writes.
+Return the committed post-operation validator. Retained ancestry is subject to
+handle/work ceilings; resource exhaustion is an error, not missing ancestry.
+Confirm rollback only after rollback succeeds. Pre-dispatch failures
 must never commit; failed started operations without a non-commit guarantee remain
 `OperationOutcomeUnknown`. Object implementations must delegate validators to
 that entry and declare requirements per `(InterfaceRef, operation)`, rather than
@@ -68,13 +85,16 @@ cancellation and resource budgets throughout backend work and report effects
 truthfully. POSIX symlinks, identity, atomic mutations and locking cannot be assumed
 for other backends.
 
-The default Linux backend uses advisory exclusive locks on regular files,
-refreshes validators after acquiring the lock and holds it through post-dispatch
-state observation. This serializes cooperating library calls; it does **not**
-promise transactional isolation from unrelated processes ignoring `flock`.
-Descriptor-relative pinned handles still prevent replacement from redirecting an
-operation to a different file. Linux capabilities only expose bounded methods,
-not raw descriptors or backend paths.
+The default Linux backend acquires advisory exclusive locks in root-to-parent
+order and then on the lockable target (directory or regular file). It compares
+retained ancestor identity to no-follow descriptor-relative lookup results,
+refreshes lineage snapshots after acquiring the locks, and holds the guards
+through post-dispatch state observation. The configured root remains its pinned
+capability even if its textual path is renamed; replaced intermediate ancestors
+are rejected. Leaf path replacement never redirects execution to a new inode.
+This serializes cooperating library calls; it does **not** promise transactional
+isolation from unrelated processes ignoring `flock`. Linux capabilities only
+expose bounded methods, not raw descriptors or backend paths.
 
 A policy must be stable/deterministic within one effective Worldspace view.
 Interface/operation visibility is uniform per registered reference within that
@@ -175,13 +195,15 @@ curl -sS -X POST http://127.0.0.1:8080/wip/v1/observe \
   --data '{"path":"/","depth":2}'
 ```
 
-A regular-file observation returns the opaque read interface reference and an object
-validator. Retrieve that descriptor with:
+A regular-file observation returns a structured read interface reference and an
+object validator. Built-in legacy registrations use scope `/` and copy the opaque
+registration string verbatim into `name`; they do not emit `scope_ref`. Copy the
+complete reference from the observation to retrieve that descriptor:
 
 ```console
 curl -sS -X POST http://127.0.0.1:8080/wip/v1/fetch_interface \
   -H 'Content-Type: application/json' -H 'Accept: application/json' \
-  --data '{"interface":"<read-interface-from-observation>"}'
+  --data '{"interface":{"scope":"/","name":"<read-interface-name-from-observation>"}}'
 ```
 
 Then call a bounded range read:
@@ -191,7 +213,7 @@ curl -sS -X POST http://127.0.0.1:8080/wip/v1/call_operation \
   -H 'Content-Type: application/json' -H 'Accept: application/json' \
   --data '{
     "target":{"path":"/notes.txt","validator":"<base64-validator>"},
-    "interface":{"reference":"<read-interface>"},
+    "interface":{"reference":{"scope":"/","name":"<read-interface-name>"}},
     "operation":"read",
     "arguments":{"offset":0,"length":4096}
   }'
@@ -205,7 +227,7 @@ curl -sS -X POST http://127.0.0.1:8080/wip/v1/call_operation \
   -H 'Content-Type: application/json' -H 'Accept: application/json' \
   --data '{
     "target":{"path":"/notes.txt","validator":"<base64-validator>"},
-    "interface":{"reference":"<write-interface>"},
+    "interface":{"reference":{"scope":"/","name":"<write-interface-name>"}},
     "operation":"replace",
     "arguments":{"contents":"dXBkYXRlZA=="}
   }'

crates/wip-fs-server/src/engine.rs

@@ -32,6 +32,39 @@ pub trait BackendEntry: WipObject + Clone {
     fn kind(&self) -> EntryKind;
 }
 
+/// A single resolved target together with its retained root-to-parent lineage.
+///
+/// The backend must resolve a connected lineage, never independent raw-path
+/// prefixes. At execution it validates ancestor membership/identity, refreshes
+/// their policy metadata, and pins that snapshot through dispatch. Target
+/// replacement must not redirect the original capability. This value is private
+/// backend context, not protocol metadata.
+#[derive(Clone)]
+pub struct ResolvedEntry<E> {
+    ancestors: Vec<E>,
+    target: E,
+}
+
+impl<E> ResolvedEntry<E> {
+    /// Create backend resolution context. `/` has no ancestors; a non-root target
+    /// has the pinned root first, followed by its intermediate parent containers.
+    pub fn new(ancestors: Vec<E>, target: E) -> Self {
+        Self { ancestors, target }
+    }
+    /// Pinned ancestor capabilities, ordered from the root to the direct parent.
+    pub fn ancestors(&self) -> &[E] {
+        &self.ancestors
+    }
+    /// The original resolved target capability, never a redirected replacement.
+    pub fn target(&self) -> &E {
+        &self.target
+    }
+    /// Consume this snapshot for refresh or request-time publication.
+    pub fn into_parts(self) -> (Vec<E>, E) {
+        (self.ancestors, self.target)
+    }
+}
+
 /// Trusted backend boundary. Implementations need not use POSIX semantics.
 ///
 /// Resolve and enumerate pinned capabilities within the configured root. Enforce
@@ -39,17 +72,28 @@ pub trait BackendEntry: WipObject + Clone {
 /// advertise capabilities the backend cannot guarantee. Errors must not include
 /// backend paths, credentials or hidden metadata.
 ///
-/// `execute` must retain the same target and serialize validator observation,
-/// publication, validation, typed dispatch and commit/rollback. Refresh entry
-/// validators *inside* the boundary before invoking the callback, and return the
-/// committed post-operation validator on success. Never upgrade an unknown
-/// outcome except after confirmed rollback. Locks only protect against actors
-/// participating in that locking protocol; document any external-writer limits.
+/// `execute` must retain the same target and complete lineage and serialize
+/// ancestor identity/membership checks, policy metadata, validator observation,
+/// publication, validation, typed dispatch and commit/rollback. Changed/detached
+/// ancestors must return `NotFound` before the callback; never substitute a new
+/// ancestor or redirect the target by re-resolving its raw path. Refresh *all*
+/// lineage metadata/validators inside the boundary and retain that snapshot
+/// through dispatch, then return the committed post-operation validator. Never
+/// upgrade an unknown outcome except after confirmed rollback. Locks only protect
+/// actors participating in the protocol; document any external-writer limits.
 pub trait FilesystemBackend {
     /// Stable capability supplied to the composition.
     type Entry: BackendEntry;
-    /// Resolve a canonical WIP path without escaping the configured root.
-    fn resolve(&self, context: &ExecutionContext, path: &str) -> ProviderResult<Self::Entry>;
+    /// Resolve a canonical WIP path and retain its connected ancestry.
+    ///
+    /// Obtain the target and lineage in one backend traversal/snapshot. Enforce
+    /// configured handle/work budgets while retaining ancestors; do not silently
+    /// omit ancestry on resource exhaustion.
+    fn resolve(
+        &self,
+        context: &ExecutionContext,
+        path: &str,
+    ) -> ProviderResult<ResolvedEntry<Self::Entry>>;
     /// Enumerate direct children, at most `maximum`; excess must fail, not truncate.
     fn children(
         &self,
@@ -61,8 +105,8 @@ pub trait FilesystemBackend {
     fn execute(
         &self,
         context: &ExecutionContext,
-        entry: Self::Entry,
-        operation: impl FnOnce(Self::Entry) -> OperationAttempt,
+        entry: ResolvedEntry<Self::Entry>,
+        operation: impl FnOnce(ResolvedEntry<Self::Entry>) -> OperationAttempt,
     ) -> ProviderResult<OperationAttempt>;
 }
 
@@ -205,39 +249,40 @@ where
     C: Composition<B::Entry>,
     P: ProjectionPolicy<B::Entry, C::Object>,
 {
-    fn resolve(&self, context: &ExecutionContext, path: &str) -> ProviderResult<B::Entry> {
+    fn resolve(
+        &self,
+        context: &ExecutionContext,
+        path: &str,
+    ) -> ProviderResult<ResolvedEntry<B::Entry>> {
         if let Err(error) = preflight(context) {
             return ProviderResult::Failure(error);
         }
         if wip_protocol::validate_path(path).is_err() {
             return ProviderResult::NotFound;
         }
-        // Check ancestors as well: guessing a descendant cannot bypass hidden parents.
-        let mut end = 1;
-        loop {
-            let prefix = if end == 1 { "/" } else { &path[..end] };
-            let entry = match self.projection.backend.resolve(context, prefix) {
-                ProviderResult::Found(entry) => entry,
-                ProviderResult::NotFound => return ProviderResult::NotFound,
-                ProviderResult::Failure(error) => return ProviderResult::Failure(error),
-            };
-            if !self
-                .projection
-                .policy
-                .object_visible(self.principal, &entry)
-            {
-                return ProviderResult::NotFound;
+        match self.projection.backend.resolve(context, path) {
+            ProviderResult::Found(resolved) => {
+                if !lineage_matches_path(&resolved, path) {
+                    return ProviderResult::Failure(internal());
+                }
+                if !self.lineage_visible(&resolved) {
+                    return ProviderResult::NotFound;
+                }
+                ProviderResult::Found(resolved)
             }
-            if prefix == path {
-                return ProviderResult::Found(entry);
-            }
-            let start = if end == 1 { 1 } else { end + 1 };
-            end = path[start..]
-                .find('/')
-                .map_or(path.len(), |index| start + index);
+            ProviderResult::NotFound => ProviderResult::NotFound,
+            ProviderResult::Failure(error) => ProviderResult::Failure(error),
         }
     }
 
+    fn lineage_visible(&self, resolved: &ResolvedEntry<B::Entry>) -> bool {
+        resolved
+            .ancestors()
+            .iter()
+            .chain(std::iter::once(resolved.target()))
+            .all(|entry| self.projection.policy.object_visible(self.principal, entry))
+    }
+
     fn publication(
         &self,
         entry: B::Entry,
@@ -342,6 +387,7 @@ where
             }
             ProviderResult::Failure(error) => return Err(read_error(error)),
         };
+        let (_ancestors, entry) = entry.into_parts();
         let mut remaining = u64::from(self.projection.limits.max_observation_nodes)
             .min(context.resource_budget().unwrap_or(u64::MAX));
         let response = self.observe_entry(context, entry, request.depth, &mut remaining)?;
@@ -426,10 +472,13 @@ where
         operation: impl FnOnce(&PublishedObject<Self::Object>) -> R,
     ) -> ProviderResult<R> {
         match self.resolve(context, path) {
-            ProviderResult::Found(entry) => match self.publication(entry, context) {
-                Ok(publication) => ProviderResult::Found(operation(&publication)),
-                Err(error) => ProviderResult::Failure(error),
-            },
+            ProviderResult::Found(resolved) => {
+                let (_ancestors, entry) = resolved.into_parts();
+                match self.publication(entry, context) {
+                    Ok(publication) => ProviderResult::Found(operation(&publication)),
+                    Err(error) => ProviderResult::Failure(error),
+                }
+            }
             ProviderResult::NotFound => ProviderResult::NotFound,
             ProviderResult::Failure(error) => ProviderResult::Failure(error),
         }
@@ -445,16 +494,16 @@ where
             ProviderResult::NotFound => return ProviderResult::NotFound,
             ProviderResult::Failure(error) => return ProviderResult::Failure(error),
         };
-        self.projection.backend.execute(context, entry, |entry| {
-            // Recheck visibility using the atomic-boundary snapshot.
-            // Failure here is still pre-dispatch, with no operation effects.
-            if !self
-                .projection
-                .policy
-                .object_visible(self.principal, &entry)
-            {
+        self.projection.backend.execute(context, entry, |resolved| {
+            // Backend validates retained lineage membership/identity and refreshes
+            // all metadata before this callback under the same boundary as dispatch.
+            if !lineage_matches_path(&resolved, path) {
+                return OperationAttempt::reject(wip_host::CallErrorKind::Internal);
+            }
+            if !self.lineage_visible(&resolved) {
                 return OperationAttempt::reject(wip_host::CallErrorKind::NotFound);
             }
+            let (_ancestors, entry) = resolved.into_parts();
             if let Err(error) = preflight(context) {
                 return OperationAttempt::reject(match error.kind() {
                     wip_host::HostErrorKind::Internal => wip_host::CallErrorKind::Internal,
@@ -544,6 +593,24 @@ where
     }
 }
 
+fn lineage_matches_path<E: BackendEntry>(resolved: &ResolvedEntry<E>, path: &str) -> bool {
+    let names: Vec<_> = if path == "/" {
+        vec![""]
+    } else {
+        std::iter::once("").chain(path[1..].split('/')).collect()
+    };
+    if resolved.ancestors().len() + 1 != names.len()
+        || resolved.target().name() != names[names.len() - 1]
+    {
+        return false;
+    }
+    resolved
+        .ancestors()
+        .iter()
+        .zip(names)
+        .all(|(entry, name)| entry.kind() == EntryKind::Directory && entry.name() == name)
+}
+
 fn read_boundary<T>(
     operation: impl FnOnce() -> Result<T, ProtocolError>,
 ) -> Result<T, ProtocolError> {

crates/wip-fs-server/src/lib.rs

@@ -58,7 +58,7 @@ use std::time::Duration;
 pub use defaults::{DefaultComposition, DefaultInterfaces, DefaultObject, default_projection};
 pub use engine::{
     BackendEntry, Composition, DefaultPolicy, EntryKind, FilesystemBackend, Projection,
-    ProjectionPolicy, ProjectionView,
+    ProjectionPolicy, ProjectionView, ResolvedEntry,
 };
 pub use http_adapter::HttpAdapter;
 pub use interfaces::{

crates/wip-fs-server/src/projection.rs

@@ -7,12 +7,12 @@ use std::sync::{Arc, Mutex, MutexGuard, TryLockError};
 
 use crate::engine::{BackendEntry, EntryKind, FilesystemBackend};
 use crate::interfaces::{FileRead, FileWrite, SymlinkInspect};
-use crate::{AccessMode, ResourceLimits};
+use crate::{AccessMode, ResolvedEntry, ResourceLimits};
 use rustix::fs::{
     CWD, FileType, FlockOperation, Mode as FsMode, OFlags, RawDir, flock, fstat, ftruncate, openat,
     readlinkat,
 };
-use rustix::io::{dup, pread, pwrite};
+use rustix::io::{pread, pwrite};
 use wip_host::{
     EffectGuarantee, ExecutionContext, HostError, OperationAttempt, ProviderResult, Validator,
     WipObject,
@@ -130,6 +130,7 @@ impl LinuxEntry {
 
     fn refresh_validator(&mut self) -> Result<(), ProjectionError> {
         let stat = fstat(self.fd()).map_err(|_| ProjectionError::Internal)?;
+        self.kind = entry_kind(stat.st_mode);
         let validator = matches!(self.kind, EntryKind::Regular | EntryKind::Symlink)
             .then(|| validator_from_stat(&stat));
         self.initial_validator = validator.clone();
@@ -180,10 +181,12 @@ enum FailureInjection {
 
 /// Linux filesystem backend using pinned, no-follow handles.
 ///
-/// Regular-file execution holds an advisory exclusive `flock` across validator
-/// refresh, dispatch, and post-operation observation. Serialization only covers
-/// actors that participate in this locking protocol; external writers can still
-/// modify the inode without taking the lock. Symlinks are inspected, not followed.
+/// Execution holds advisory exclusive `flock` guards on directories in
+/// root-to-parent order and on directory or regular-file targets across lineage
+/// validation, validator refresh, dispatch, and post-operation observation.
+/// Serialization only covers actors that participate in this locking protocol;
+/// external writers can still mutate entries without taking the locks. Symlinks
+/// are inspected, not followed.
 pub struct LinuxBackend {
     root: OwnedFd,
     access: AccessMode,
@@ -220,22 +223,28 @@ impl LinuxBackend {
         &self,
         context: &ExecutionContext,
         path: &str,
-    ) -> Result<LinuxEntry, ProjectionError> {
+    ) -> Result<ResolvedEntry<LinuxEntry>, ProjectionError> {
         check_context(context)?;
         wip_protocol::validate_path(path).map_err(|_| ProjectionError::NotFound)?;
+        let root = self.entry(
+            context,
+            String::new(),
+            reopen(&self.root, OFlags::RDONLY | OFlags::DIRECTORY)?,
+        )?;
         if path == "/" {
-            let fd = reopen(&self.root, OFlags::RDONLY | OFlags::DIRECTORY)?;
-            return self.entry(context, String::new(), fd);
+            return Ok(ResolvedEntry::new(Vec::new(), root));
         }
-        let mut parent = dup(&self.root).map_err(|_| ProjectionError::Internal)?;
+        // Retain the exact directories traversed, rather than resolving prefixes again.
+        let mut ancestors = vec![root];
         let mut segments = path[1..].split('/').peekable();
         while let Some(segment) = segments.next() {
             check_context(context)?;
             if segment.as_bytes().contains(&0) {
                 return Err(ProjectionError::NotFound);
             }
+            let parent = ancestors.last().ok_or(ProjectionError::Internal)?;
             let probe = openat(
-                &parent,
+                parent.fd(),
                 segment,
                 OFlags::PATH | OFlags::NOFOLLOW | OFlags::CLOEXEC,
                 FsMode::empty(),
@@ -243,14 +252,15 @@ impl LinuxBackend {
             .map_err(classify_lookup)?;
             let stat = fstat(&probe).map_err(|_| ProjectionError::Internal)?;
             let kind = entry_kind(stat.st_mode);
+            if segments.peek().is_some() && kind != EntryKind::Directory {
+                return Err(ProjectionError::NotFound);
+            }
+            let fd = self.reopen_final(probe, kind)?;
+            let entry = self.entry(context, segment.to_owned(), fd)?;
             if segments.peek().is_some() {
-                if kind != EntryKind::Directory {
-                    return Err(ProjectionError::NotFound);
-                }
-                parent = reopen(&probe, OFlags::RDONLY | OFlags::DIRECTORY)?;
+                ancestors.push(entry);
             } else {
-                let fd = self.reopen_final(probe, kind)?;
-                return self.entry(context, segment.to_owned(), fd);
+                return Ok(ResolvedEntry::new(ancestors, entry));
             }
         }
         Err(ProjectionError::NotFound)
@@ -323,6 +333,49 @@ impl LinuxBackend {
         })
     }
 
+    fn validate_ancestry(
+        &self,
+        context: &ExecutionContext,
+        ancestors: &[LinuxEntry],
+        target: &LinuxEntry,
+    ) -> Result<(), ProjectionError> {
+        check_context(context)?;
+        let root = ancestors.first().unwrap_or(target);
+        let configured = fstat(&self.root).map_err(|_| ProjectionError::Internal)?;
+        let retained = fstat(root.fd()).map_err(|_| ProjectionError::Internal)?;
+        // The configured root is a capability, not its possibly renamed textual path.
+        if entry_kind(retained.st_mode) != EntryKind::Directory
+            || retained.st_dev != configured.st_dev
+            || retained.st_ino != configured.st_ino
+        {
+            return Err(ProjectionError::NotFound);
+        }
+        for pair in ancestors.windows(2) {
+            check_context(context)?;
+            let parent = &pair[0];
+            let child = &pair[1];
+            let visible = openat(
+                parent.fd(),
+                child.name.as_str(),
+                OFlags::PATH | OFlags::NOFOLLOW | OFlags::CLOEXEC,
+                FsMode::empty(),
+            )
+            .map_err(classify_lookup)?;
+            let visible = fstat(&visible).map_err(|_| ProjectionError::Internal)?;
+            let retained = fstat(child.fd()).map_err(|_| ProjectionError::Internal)?;
+            if entry_kind(visible.st_mode) != EntryKind::Directory
+                || entry_kind(retained.st_mode) != EntryKind::Directory
+                || visible.st_dev != retained.st_dev
+                || visible.st_ino != retained.st_ino
+            {
+                return Err(ProjectionError::NotFound);
+            }
+        }
+        // Deliberately do not look up the target name: leaf replacement must not
+        // redirect execution away from its original pinned inode.
+        check_context(context)
+    }
+
     #[cfg(test)]
     fn set_injection(&self, injection: FailureInjection) {
         *self
@@ -341,7 +394,11 @@ impl BackendEntry for LinuxEntry {
 impl FilesystemBackend for LinuxBackend {
     type Entry = LinuxEntry;
 
-    fn resolve(&self, context: &ExecutionContext, path: &str) -> ProviderResult<LinuxEntry> {
+    fn resolve(
+        &self,
+        context: &ExecutionContext,
+        path: &str,
+    ) -> ProviderResult<ResolvedEntry<LinuxEntry>> {
         match self.resolve_entry(context, path) {
             Ok(entry) => ProviderResult::Found(entry),
             Err(error) => error.host(),
@@ -393,16 +450,32 @@ impl FilesystemBackend for LinuxBackend {
     fn execute(
         &self,
         context: &ExecutionContext,
-        mut entry: LinuxEntry,
-        callback: impl FnOnce(LinuxEntry) -> OperationAttempt,
+        resolved: ResolvedEntry<LinuxEntry>,
+        callback: impl FnOnce(ResolvedEntry<LinuxEntry>) -> OperationAttempt,
     ) -> ProviderResult<OperationAttempt> {
         if let Err(error) = check_context(context) {
             return error.host();
         }
-        let lock_entry = Arc::clone(&entry.inner);
-        let _lock = if entry.kind == EntryKind::Regular {
-            match lock_with_context(&lock_entry, context, self.limits.request_timeout) {
-                Ok(lock) => Some(lock),
+        let (mut ancestors, mut entry) = resolved.into_parts();
+        // Independent resolutions have independent open-file descriptions; clones
+        // also need the per-entry mutex because flock alone treats them as one owner.
+        // Always acquire directories root-to-parent, then the target (if lockable).
+        let mut lock_entries: Vec<_> = ancestors
+            .iter()
+            .map(|ancestor| Arc::clone(&ancestor.inner))
+            .collect();
+        if matches!(entry.kind, EntryKind::Directory | EntryKind::Regular) {
+            lock_entries.push(Arc::clone(&entry.inner));
+        }
+        let started = std::time::Instant::now();
+        let mut locks = Vec::with_capacity(lock_entries.len());
+        for inner in &lock_entries {
+            let remaining = self
+                .limits
+                .request_timeout
+                .saturating_sub(started.elapsed());
+            match lock_with_context(inner, context, remaining) {
+                Ok(lock) => locks.push(lock),
                 Err(ProjectionError::Resource) => {
                     return ProviderResult::Failure(HostError::resource_limit(
                         "filesystem lock deadline exceeded",
@@ -416,15 +489,22 @@ impl FilesystemBackend for LinuxBackend {
                     ));
                 }
             }
-        } else {
-            None
-        };
-        // Both snapshots must describe the state under the lock, not at resolve time.
+        }
+        if let Err(error) = self.validate_ancestry(context, &ancestors, &entry) {
+            return error.host();
+        }
+        for ancestor in &mut ancestors {
+            if ancestor.refresh_validator().is_err() {
+                return ProviderResult::Failure(internal_not_committed());
+            }
+            ancestor.context = context.clone();
+        }
+        // Both snapshots must describe the state under the locks, not at resolve time.
         if entry.refresh_validator().is_err() {
             return ProviderResult::Failure(internal_not_committed());
         }
         entry.context = context.clone();
-        let mut attempt = callback(entry.clone());
+        let mut attempt = callback(ResolvedEntry::new(ancestors, entry.clone()));
         if let OperationAttempt::Started(Ok(result)) = &mut attempt {
             if entry.refresh_validator().is_err() {
                 return ProviderResult::Failure(HostError::internal(
@@ -735,7 +815,7 @@ mod tests {
     use super::{FailureInjection, FlockOperation, LinuxBackend, LinuxEntry};
     use crate::engine::{DefaultPolicy, FilesystemBackend, Projection};
     use crate::interfaces::{FileRead, FileWrite};
-    use crate::{AccessMode, DefaultComposition, ResourceLimits};
+    use crate::{AccessMode, DefaultComposition, ResolvedEntry, ResourceLimits};
 
     type DefaultProjection = Projection<LinuxBackend, DefaultComposition, DefaultPolicy>;
 
@@ -747,7 +827,7 @@ mod tests {
         projection: &DefaultProjection,
         path: &str,
         validator: Option<Vec<u8>>,
-        interface: String,
+        interface: wip_protocol::InterfaceReference,
         operation: &str,
         arguments: BTreeMap<String, Value>,
     ) -> Result<wip_protocol::CallOperationResponse, wip_host::CallError> {
@@ -757,6 +837,7 @@ mod tests {
                 validator,
             },
             interface: InterfaceTarget {
+                scope_ref: None,
                 reference: interface,
                 validator: None,
             },
@@ -765,7 +846,11 @@ mod tests {
         })
     }
 
-    fn resolved(backend: &LinuxBackend, context: &ExecutionContext, path: &str) -> LinuxEntry {
+    fn resolved(
+        backend: &LinuxBackend,
+        context: &ExecutionContext,
+        path: &str,
+    ) -> ResolvedEntry<LinuxEntry> {
         match backend.resolve(context, path) {
             ProviderResult::Found(entry) => entry,
             ProviderResult::NotFound => panic!("entry should resolve"),
@@ -786,8 +871,8 @@ mod tests {
         .expect("open backend");
         let context = ExecutionContext::new();
         let entry = resolved(&backend, &context, "/file");
-        let original = entry.initial_validator.clone();
-        let pinned = entry.clone();
+        let original = entry.target().initial_validator.clone();
+        let pinned = entry.target().clone();
         // Simulate a cooperating writer committing between resolution and execution.
         fs::write(&path, b"changed before lock acquisition").expect("external mutation");
         let lock_probe = fs::OpenOptions::new()
@@ -796,7 +881,8 @@ mod tests {
             .open(&path)
             .expect("open independent lock probe");
         let mut callback_validator = None;
-        let attempt = backend.execute(&context, entry, |entry| {
+        let attempt = backend.execute(&context, entry, |resolved| {
+            let entry = resolved.target();
             assert!(std::sync::Arc::ptr_eq(&entry.inner, &pinned.inner));
             assert_ne!(entry.initial_validator, original);
             assert_eq!(
@@ -824,7 +910,9 @@ mod tests {
         assert_ne!(result.validator, callback_validator);
         assert_eq!(
             result.validator,
-            resolved(&backend, &context, "/file").initial_validator,
+            resolved(&backend, &context, "/file")
+                .target()
+                .initial_validator,
         );
         assert_eq!(fs::read(&path).expect("read written file"), b"new");
         // The retained clone must not keep the operation's flock held.
@@ -846,10 +934,11 @@ mod tests {
         .expect("open backend");
         let context = ExecutionContext::new();
         let entry = resolved(&backend, &context, "/file");
-        let pinned = entry.clone();
+        let pinned = entry.target().clone();
         fs::remove_file(&path).expect("unlink pinned entry");
         fs::write(&path, b"replacement").expect("replace path");
-        let attempt = backend.execute(&context, entry, |entry| {
+        let attempt = backend.execute(&context, entry, |resolved| {
+            let entry = resolved.target();
             assert!(std::sync::Arc::ptr_eq(&entry.inner, &pinned.inner));
             entry
                 .replace(wip_interface::Bytes(b"pinned write".to_vec()))
@@ -870,6 +959,239 @@ mod tests {
         );
     }
 
+    #[test]
+    fn detached_or_replaced_ancestors_reject_before_callback_without_effects() {
+        // Exercise both the immediate parent and a higher ancestor, with a
+        // visible directory replacement, no replacement, and a symlink replacement.
+        for ancestor in ["a", "a/b"] {
+            for replacement in ["directory", "missing", "symlink"] {
+                let temporary = tempdir().expect("temporary root");
+                fs::create_dir_all(temporary.path().join("a/b")).expect("create lineage");
+                fs::write(temporary.path().join("a/b/file"), b"original").expect("write original");
+                let backend = LinuxBackend::open(
+                    temporary.path(),
+                    AccessMode::ReadWrite,
+                    ResourceLimits::default(),
+                )
+                .expect("open backend");
+                let context = ExecutionContext::new();
+                let entry = resolved(&backend, &context, "/a/b/file");
+                let pinned = entry.target().clone();
+                let detached = temporary.path().join("detached");
+                let ancestor_path = temporary.path().join(ancestor);
+                fs::rename(&ancestor_path, &detached).expect("detach ancestor");
+                if replacement == "directory" {
+                    fs::create_dir(&ancestor_path).expect("replace directory");
+                } else if replacement == "symlink" {
+                    std::os::unix::fs::symlink(&detached, &ancestor_path)
+                        .expect("replace ancestor with symlink to original");
+                }
+                let visible_leaf =
+                    ancestor_path.join(if ancestor == "a" { "b/file" } else { "file" });
+                if replacement == "directory" {
+                    fs::create_dir_all(visible_leaf.parent().expect("leaf parent"))
+                        .expect("create replacement lineage");
+                    fs::write(&visible_leaf, b"replacement").expect("write replacement");
+                }
+                let mut called = false;
+                let attempt = backend.execute(&context, entry, |entry| {
+                    called = true;
+                    entry
+                        .target()
+                        .replace(wip_interface::Bytes(b"bad".to_vec()))
+                        .expect("would write pinned inode");
+                    OperationAttempt::reject(CallErrorKind::ValidatorMismatch)
+                });
+                assert!(
+                    matches!(attempt, ProviderResult::NotFound),
+                    "{ancestor}: {replacement}"
+                );
+                assert!(!called);
+                assert_eq!(
+                    pinned.read(None, None).expect("read original inode").0,
+                    b"original"
+                );
+                if replacement != "missing" {
+                    assert_eq!(
+                        fs::read(&visible_leaf).expect("read visible leaf"),
+                        if replacement == "directory" {
+                            b"replacement".as_slice()
+                        } else {
+                            b"original".as_slice()
+                        }
+                    );
+                }
+                // Rejection releases every guard, even while the target is retained.
+                let root_probe = fs::File::open(temporary.path()).expect("open root probe");
+                rustix::fs::flock(&root_probe, FlockOperation::NonBlockingLockExclusive)
+                    .expect("rejection released root guard");
+            }
+        }
+    }
+
+    #[test]
+    fn execution_retains_and_refreshes_ancestors_under_ordered_directory_guards() {
+        let temporary = tempdir().expect("temporary root");
+        fs::create_dir_all(temporary.path().join("a/b")).expect("create lineage");
+        fs::write(temporary.path().join("a/b/file"), b"original").expect("write file");
+        let backend = LinuxBackend::open(
+            temporary.path(),
+            AccessMode::ReadOnly,
+            ResourceLimits::default(),
+        )
+        .expect("open backend");
+        let context = ExecutionContext::new();
+        let entry = resolved(&backend, &context, "/a/b/file");
+        assert_eq!(
+            entry
+                .ancestors()
+                .iter()
+                .map(WipObject::name)
+                .collect::<Vec<_>>(),
+            ["", "a", "b"]
+        );
+        let pinned_ancestors = entry.ancestors().to_vec();
+        let (mut ancestors, target) = entry.into_parts();
+        // Stale snapshots must not escape the execution boundary.
+        for ancestor in &mut ancestors {
+            ancestor.validator = Some(wip_host::Validator::new(vec![1]));
+            ancestor.initial_validator = Some(vec![1]);
+        }
+        let probes: Vec<_> = ["", "a", "a/b", "a/b/file"]
+            .into_iter()
+            .map(|path| fs::File::open(temporary.path().join(path)).expect("open lock probe"))
+            .collect();
+        let attempt = backend.execute(&context, ResolvedEntry::new(ancestors, target), |entry| {
+            for (ancestor, pinned) in entry.ancestors().iter().zip(&pinned_ancestors) {
+                assert!(std::sync::Arc::ptr_eq(&ancestor.inner, &pinned.inner));
+                assert!(ancestor.validator().is_none());
+                assert!(ancestor.initial_validator.is_none());
+            }
+            for probe in &probes {
+                assert_eq!(
+                    rustix::fs::flock(probe, FlockOperation::NonBlockingLockExclusive),
+                    Err(rustix::io::Errno::WOULDBLOCK)
+                );
+            }
+            OperationAttempt::reject(CallErrorKind::ValidatorMismatch)
+        });
+        assert!(matches!(attempt, ProviderResult::Found(_)));
+        for probe in &probes {
+            rustix::fs::flock(probe, FlockOperation::NonBlockingLockExclusive)
+                .expect("guard released after callback");
+            rustix::fs::flock(probe, FlockOperation::Unlock).expect("unlock probe");
+        }
+    }
+
+    #[test]
+    fn configured_root_stays_pinned_after_textual_rename_and_replacement() {
+        let temporary = tempdir().expect("temporary parent");
+        let configured = temporary.path().join("root");
+        fs::create_dir_all(configured.join("dir")).expect("create original root");
+        fs::write(configured.join("dir/file"), b"original").expect("write original file");
+        let backend = LinuxBackend::open(
+            &configured,
+            AccessMode::ReadWrite,
+            ResourceLimits::default(),
+        )
+        .expect("open backend");
+        let context = ExecutionContext::new();
+        let root = resolved(&backend, &context, "/");
+        assert!(root.ancestors().is_empty());
+        let file = resolved(&backend, &context, "/dir/file");
+        let moved = temporary.path().join("moved");
+        fs::rename(&configured, &moved).expect("rename configured root");
+        fs::create_dir_all(configured.join("dir")).expect("replace textual root");
+        fs::write(configured.join("dir/file"), b"replacement").expect("write replacement file");
+        for entry in [
+            root,
+            resolved(&backend, &context, "/"),
+            resolved(&backend, &context, "/dir"),
+        ] {
+            let attempt = backend.execute(&context, entry, |entry| {
+                assert_eq!(entry.target().kind, crate::EntryKind::Directory);
+                OperationAttempt::reject(CallErrorKind::ValidatorMismatch)
+            });
+            assert!(
+                matches!(attempt, ProviderResult::Found(_)),
+                "root/directory locks once"
+            );
+        }
+        let attempt = backend.execute(&context, file, |entry| {
+            entry
+                .target()
+                .replace(wip_interface::Bytes(b"pinned write".to_vec()))
+                .expect("write beneath original root");
+            OperationAttempt::Started(Ok(wip_host::CallResult {
+                result: Value::Bytes(Vec::new()),
+                validator: None,
+            }))
+        });
+        assert!(matches!(
+            attempt,
+            ProviderResult::Found(OperationAttempt::Started(Ok(_)))
+        ));
+        assert_eq!(
+            fs::read(moved.join("dir/file")).expect("read original root"),
+            b"pinned write"
+        );
+        assert_eq!(
+            fs::read(configured.join("dir/file")).expect("read textual replacement"),
+            b"replacement"
+        );
+        assert_eq!(
+            resolved(&backend, &context, "/dir/file")
+                .target()
+                .read(None, None)
+                .expect("resolution still uses pinned root")
+                .0,
+            b"pinned write"
+        );
+    }
+
+    #[test]
+    fn deep_resolution_counts_all_retained_ancestors_against_handle_budget() {
+        let temporary = tempdir().expect("temporary root");
+        fs::create_dir_all(temporary.path().join("a/b")).expect("create lineage");
+        fs::write(temporary.path().join("a/b/file"), b"original").expect("write file");
+        let context = ExecutionContext::new();
+        for maximum in [3, 4] {
+            let backend = LinuxBackend::open(
+                temporary.path(),
+                AccessMode::ReadOnly,
+                ResourceLimits {
+                    max_open_handles: maximum,
+                    ..ResourceLimits::default()
+                },
+            )
+            .expect("open backend");
+            match backend.resolve(&context, "/a/b/file") {
+                ProviderResult::Failure(error) if maximum == 3 => {
+                    assert_eq!(error.kind(), wip_host::HostErrorKind::ResourceLimitExceeded);
+                    assert_eq!(
+                        error.effect_guarantee(),
+                        wip_host::EffectGuarantee::NotCommitted
+                    );
+                }
+                ProviderResult::Found(entry) if maximum == 4 => {
+                    assert_eq!(entry.ancestors().len(), 3);
+                    assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 4);
+                    let cloned =
+                        ResolvedEntry::new(entry.ancestors().to_vec(), entry.target().clone());
+                    drop(entry);
+                    assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 4);
+                    drop(cloned);
+                }
+                _ => panic!("unexpected resolution outcome for budget {maximum}"),
+            }
+            assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 0);
+            let root = resolved(&backend, &context, "/");
+            assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 1);
+            drop(root);
+            assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 0);
+        }
+    }
+
     #[test]
     fn rejected_execution_releases_lock_even_when_callback_retains_entry() {
         let temporary = tempdir().expect("temporary root");
@@ -914,7 +1236,7 @@ mod tests {
         .expect("open backend");
         let context = ExecutionContext::new();
         let entry = resolved(&backend, &context, "/file");
-        let cloned = entry.clone();
+        let cloned = ResolvedEntry::new(entry.ancestors().to_vec(), entry.target().clone());
         let attempt = backend.execute(&context, entry, |entry| {
             let started = std::time::Instant::now();
             let nested = backend.execute(&context, entry, |_| {
@@ -956,10 +1278,10 @@ mod tests {
         .expect("open backend");
         let context = ExecutionContext::new();
         let root = resolved(&backend, &context, "/");
-        assert!(backend.children(&context, &root, 1).is_err());
+        assert!(backend.children(&context, root.target(), 1).is_err());
         assert_eq!(backend.handles.current.load(super::Ordering::Acquire), 1);
         let children = backend
-            .children(&context, &root, 2)
+            .children(&context, root.target(), 2)
             .expect("complete children");
         assert_eq!(children.len(), 2);
         let cloned = children[0].clone();
@@ -986,13 +1308,14 @@ mod tests {
         .expect("open backend");
         let context = ExecutionContext::new();
         let entry = resolved(&backend, &context, "/file");
-        assert_eq!(entry.access_mode(), AccessMode::ReadOnly);
-        assert!(entry.supports_file_read());
-        assert!(!entry.supports_file_write());
-        assert!(!entry.supports_symlink_inspect());
-        assert!(entry.read(None, None).is_err());
-        assert_eq!(entry.read(None, Some(2)).expect("bounded read").0, b"ol");
-        assert!(entry.replace(wip_interface::Bytes(Vec::new())).is_err());
+        let target = entry.target();
+        assert_eq!(target.access_mode(), AccessMode::ReadOnly);
+        assert!(target.supports_file_read());
+        assert!(!target.supports_file_write());
+        assert!(!target.supports_symlink_inspect());
+        assert!(target.read(None, None).is_err());
+        assert_eq!(target.read(None, Some(2)).expect("bounded read").0, b"ol");
+        assert!(target.replace(wip_interface::Bytes(Vec::new())).is_err());
         assert_eq!(fs::read(&path).expect("read unchanged file"), b"old");
         let cancellation = wip_host::CancellationToken::new();
         cancellation.cancel();

crates/wip-fs-server/tests/end_to_end.rs

@@ -98,6 +98,7 @@ fn real_listener_serves_three_core_interactions_and_write() {
             validator: file.validator.clone(),
         },
         interface: InterfaceTarget {
+            scope_ref: None,
             reference: file.interfaces[0].clone(),
             validator: None,
         },
@@ -141,6 +142,7 @@ fn real_listener_serves_three_core_interactions_and_write() {
             validator: file.validator,
         },
         interface: InterfaceTarget {
+            scope_ref: None,
             reference: file.interfaces[1].clone(),
             validator: None,
         },
@@ -412,7 +414,7 @@ fn call_argument_decoding_does_not_mask_missing_target() {
     let config = ServerConfig::for_root(temporary.path());
     let server = WipFsServer::new(config).expect("build server");
     let endpoint = Endpoint::parse("http://localhost/wip").expect("endpoint");
-    let body = br#"{"target":{"path":"/missing"},"interface":{"reference":"unknown"},"operation":"missing","arguments":{"bytes":"not-base64"}}"#;
+    let body = br#"{"target":{"path":"/missing"},"interface":{"reference":{"scope":"/","name":"unknown"}},"operation":"missing","arguments":{"bytes":"not-base64"}}"#;
     let request = http::Request::builder()
         .method(http::Method::POST)
         .uri(endpoint.route(Route::CallOperation).as_str())
@@ -490,6 +492,7 @@ fn read_response_size_failure_is_transport_local() {
             validator: file.validator,
         },
         interface: InterfaceTarget {
+            scope_ref: None,
             reference: file.interfaces[0].clone(),
             validator: None,
         },

crates/wip-fs-server/tests/extensions.rs

@@ -5,7 +5,7 @@ use std::time::{Duration, Instant};
 
 use wip_fs_server::{
     BackendEntry, Composition, DefaultInterfaces, EntryKind, FileRead, FilesystemBackend,
-    HttpAdapter, Projection, ProjectionPolicy, ResourceLimits,
+    HttpAdapter, Projection, ProjectionPolicy, ResolvedEntry, ResourceLimits,
 };
 use wip_host::{
     CancellationToken, EffectGuarantee, ExecutionContext, HostError, InterfaceRef,
@@ -77,15 +77,20 @@ struct Entry {
     path: String,
     node: Arc<Node>,
     validator: Validator,
+    hidden: bool,
 }
 impl Entry {
     fn snapshot(path: String, node: Arc<Node>) -> Self {
-        let revision = node.data.lock().unwrap().revision;
+        let data = node.data.lock().unwrap();
+        let revision = data.revision;
+        let hidden = data.hidden;
+        drop(data);
         let validator = Validator::new(format!("{}:{revision}", node.id).into_bytes());
         Self {
             path,
             node,
             validator,
+            hidden,
         }
     }
 }
@@ -118,6 +123,8 @@ struct Seen {
 struct Controls {
     bump_before_execute: bool,
     hide_before_execute: bool,
+    hide_ancestor: Option<String>,
+    replace_ancestor: Option<String>,
     replace_mapping: bool,
     rollback: bool,
     cancel_on_execute: bool,
@@ -168,7 +175,11 @@ fn check_context(context: &ExecutionContext) -> Result<(), HostError> {
 }
 impl FilesystemBackend for MemoryBackend {
     type Entry = Entry;
-    fn resolve(&self, context: &ExecutionContext, path: &str) -> ProviderResult<Entry> {
+    fn resolve(
+        &self,
+        context: &ExecutionContext,
+        path: &str,
+    ) -> ProviderResult<ResolvedEntry<Entry>> {
         self.0.record("resolve", path, context);
         if let Err(error) = check_context(context) {
             return ProviderResult::Failure(error);
@@ -179,11 +190,33 @@ impl FilesystemBackend for MemoryBackend {
                 EffectGuarantee::NotCommitted,
             ));
         }
-        // Map lookup only: there is no host path to reopen or escape.
-        match self.0.nodes.lock().unwrap().get(path).cloned() {
-            Some(node) => ProviderResult::Found(Entry::snapshot(path.into(), node)),
-            None => ProviderResult::NotFound,
+        // One connected map snapshot, serialized with participating mutations.
+        let _transaction = self.0.transaction.lock().unwrap();
+        let nodes = self.0.nodes.lock().unwrap();
+        let Some(node) = nodes.get(path) else {
+            return ProviderResult::NotFound;
+        };
+        let mut ancestors = Vec::new();
+        if path != "/" {
+            let prefixes = std::iter::once("/").chain(
+                path.match_indices('/')
+                    .skip(1)
+                    .map(|(index, _)| &path[..index]),
+            );
+            for prefix in prefixes {
+                let Some(parent) = nodes.get(prefix) else {
+                    return ProviderResult::NotFound;
+                };
+                if parent.kind != EntryKind::Directory {
+                    return ProviderResult::NotFound;
+                }
+                ancestors.push(Entry::snapshot(prefix.into(), parent.clone()));
+            }
         }
+        ProviderResult::Found(ResolvedEntry::new(
+            ancestors,
+            Entry::snapshot(path.into(), node.clone()),
+        ))
     }
     fn children(
         &self,
@@ -224,10 +257,11 @@ impl FilesystemBackend for MemoryBackend {
     fn execute(
         &self,
         context: &ExecutionContext,
-        entry: Entry,
-        operation: impl FnOnce(Entry) -> OperationAttempt,
+        resolved: ResolvedEntry<Entry>,
+        operation: impl FnOnce(ResolvedEntry<Entry>) -> OperationAttempt,
     ) -> ProviderResult<OperationAttempt> {
         let _lock = self.0.transaction.lock().unwrap();
+        let (ancestors, entry) = resolved.into_parts();
         self.0.record("execute", &entry.path, context);
         if let Err(error) = check_context(context) {
             return ProviderResult::Failure(error);
@@ -243,6 +277,24 @@ impl FilesystemBackend for MemoryBackend {
         if controls.hide_before_execute {
             entry.node.data.lock().unwrap().hidden = true;
         }
+        if let Some(path) = controls.hide_ancestor.take() {
+            self.0.node(&path).data.lock().unwrap().hidden = true;
+        }
+        if let Some(path) = controls.replace_ancestor.take() {
+            self.0.nodes.lock().unwrap().insert(
+                path,
+                Arc::new(Node {
+                    id: 1000,
+                    kind: EntryKind::Directory,
+                    data: Mutex::new(Data {
+                        bytes: b"replacement ancestor".to_vec(),
+                        revision: 1,
+                        hidden: false,
+                    }),
+                    calls: Mutex::new(Vec::new()),
+                }),
+            );
+        }
         if controls.replace_mapping {
             // The callback must still receive the original capability, not this decoy.
             self.0.nodes.lock().unwrap().insert(
@@ -265,9 +317,25 @@ impl FilesystemBackend for MemoryBackend {
         }
         let rollback = controls.rollback;
         drop(controls);
+        // Verify lineage identity/membership within the same transaction. The
+        // callback cannot see a substituted ancestor, nor a redirected target.
+        let nodes = self.0.nodes.lock().unwrap();
+        for ancestor in &ancestors {
+            if !nodes
+                .get(&ancestor.path)
+                .is_some_and(|node| Arc::ptr_eq(node, &ancestor.node))
+            {
+                return ProviderResult::NotFound;
+            }
+        }
+        drop(nodes);
+        let refreshed_ancestors = ancestors
+            .into_iter()
+            .map(|ancestor| Entry::snapshot(ancestor.path, ancestor.node))
+            .collect();
         let before = entry.node.data.lock().unwrap().clone();
         let refreshed = Entry::snapshot(entry.path.clone(), entry.node.clone());
-        let attempt = operation(refreshed);
+        let attempt = operation(ResolvedEntry::new(refreshed_ancestors, refreshed));
         let attempt = match attempt {
             OperationAttempt::Started(Ok(mut result)) => {
                 result.validator = Some(
@@ -437,8 +505,7 @@ struct Policy {
 impl ProjectionPolicy<Entry, Object> for Policy {
     type Principal = Principal;
     fn object_visible(&self, principal: &Principal, entry: &Entry) -> bool {
-        !entry.node.data.lock().unwrap().hidden
-            && (!matches!(principal, Principal::Limited) || entry.path != "/secret")
+        !entry.hidden && (!matches!(principal, Principal::Limited) || entry.path != "/secret")
     }
     fn interface_visible(&self, principal: &Principal, interface: &InterfaceRef) -> bool {
         !(matches!(principal, Principal::Limited) && self.hide_read && interface == &self.read)
@@ -509,7 +576,7 @@ fn observation_and_fetch_policy_panics_remain_sanitized_read_failures() {
         let mut registry = InterfaceRegistry::new();
         let defaults = DefaultInterfaces::register(&mut registry).unwrap();
         let custom = registry.register(MemoryOperationsDefinition, None).unwrap();
-        let reference = custom.reference().as_str().to_owned();
+        let reference = custom.reference().protocol_reference();
         let engine = Projection::new(
             MemoryBackend(fixture.shared.clone()),
             registry,
@@ -549,8 +616,8 @@ type Engine = Projection<MemoryBackend, MemoryComposition, Policy>;
 struct Fixture {
     engine: Engine,
     shared: Arc<Shared>,
-    custom: String,
-    read: String,
+    custom: wip_protocol::InterfaceReference,
+    read: wip_protocol::InterfaceReference,
     limits: ResourceLimits,
 }
 impl Fixture {
@@ -629,8 +696,8 @@ impl Fixture {
                 limits,
             ),
             shared,
-            custom: custom_ref.as_str().into(),
-            read: read_ref.as_str().into(),
+            custom: custom_ref.protocol_reference(),
+            read: read_ref.protocol_reference(),
             limits,
         }
     }
@@ -640,7 +707,11 @@ impl Fixture {
             .observe(&ExecutionContext::new(), &observe_request(path, depth))
             .unwrap()
     }
-    fn descriptor(&self, principal: &Principal, reference: &str) -> InterfaceDescriptor {
+    fn descriptor(
+        &self,
+        principal: &Principal,
+        reference: &wip_protocol::InterfaceReference,
+    ) -> InterfaceDescriptor {
         self.engine
             .view(principal)
             .fetch_interface(&fetch_request(reference))
@@ -650,7 +721,7 @@ impl Fixture {
     fn request(
         &self,
         path: &str,
-        reference: &str,
+        reference: &wip_protocol::InterfaceReference,
         operation: &str,
         validator: Option<Vec<u8>>,
     ) -> CallOperationRequest {
@@ -660,7 +731,8 @@ impl Fixture {
                 validator,
             },
             interface: InterfaceTarget {
-                reference: reference.into(),
+                scope_ref: None,
+                reference: reference.clone(),
                 validator: None,
             },
             operation: operation.into(),
@@ -690,15 +762,118 @@ impl Fixture {
         (response, decoded)
     }
 }
+#[test]
+fn ancestor_visibility_refresh_inside_boundary_prevents_descendant_invocation_and_effects() {
+    for (target, ancestor) in [
+        ("/added", "/"),
+        ("/secret/nested/data", "/"),
+        ("/secret/nested/data", "/secret"),
+        ("/secret/nested/data", "/secret/nested"),
+    ] {
+        for operation in ["denied", "read", "change"] {
+            let fixture = Fixture::new();
+            let observation = fixture.observe(&Principal::Admin, target, 0);
+            let descriptor = fixture.descriptor(&Principal::Admin, &fixture.custom);
+            let mut request = fixture.request(
+                target,
+                &fixture.custom,
+                operation,
+                observation.object.validator,
+            );
+            if operation == "change" {
+                request
+                    .arguments
+                    .insert("contents".into(), Value::Bytes(b"must not commit".to_vec()));
+            }
+            let leaf = fixture.shared.node(target);
+            let before = leaf.data.lock().unwrap().clone();
+            fixture.shared.controls.lock().unwrap().hide_ancestor = Some(ancestor.into());
+            let (wire, response) = fixture.http_call(
+                &Principal::Admin,
+                &request,
+                &descriptor,
+                &ExecutionContext::new(),
+            );
+            wire_error(response, ProtocolErrorCode::NotFound);
+            assert!(leaf.calls.lock().unwrap().is_empty());
+            assert_eq!(*leaf.data.lock().unwrap(), before);
+            assert!(!String::from_utf8_lossy(wire.body()).contains(BACKEND_SECRET));
+            let error = fixture
+                .engine
+                .view(&Principal::Admin)
+                .observe(&ExecutionContext::new(), &observe_request(target, 0))
+                .unwrap_err();
+            assert_eq!(error.code, ProtocolErrorCode::NotFound);
+            // The entire target resolves once, not as unrelated path prefixes.
+            let seen = fixture.shared.seen.lock().unwrap();
+            assert!(
+                seen.iter()
+                    .filter(|event| event.stage == "resolve")
+                    .all(|event| event.path == target)
+            );
+        }
+    }
+}
+
+#[test]
+fn replaced_visible_ancestors_reject_without_redirecting_or_dispatching_the_pinned_target() {
+    for (target, ancestor) in [
+        ("/added", "/"),
+        ("/secret/nested/data", "/secret"),
+        ("/secret/nested/data", "/secret/nested"),
+    ] {
+        let fixture = Fixture::new();
+        let observation = fixture.observe(&Principal::Admin, target, 0);
+        let descriptor = fixture.descriptor(&Principal::Admin, &fixture.custom);
+        let mut request = fixture.request(
+            target,
+            &fixture.custom,
+            "change",
+            observation.object.validator,
+        );
+        request
+            .arguments
+            .insert("contents".into(), Value::Bytes(b"must not commit".to_vec()));
+        let leaf = fixture.shared.node(target);
+        let original_ancestor = fixture.shared.node(ancestor);
+        let before = leaf.data.lock().unwrap().clone();
+        fixture.shared.controls.lock().unwrap().replace_ancestor = Some(ancestor.into());
+        let (_, response) = fixture.http_call(
+            &Principal::Admin,
+            &request,
+            &descriptor,
+            &ExecutionContext::new(),
+        );
+        wire_error(response, ProtocolErrorCode::NotFound);
+        assert!(leaf.calls.lock().unwrap().is_empty());
+        assert_eq!(*leaf.data.lock().unwrap(), before);
+        assert!(!Arc::ptr_eq(
+            &original_ancestor,
+            &fixture.shared.node(ancestor)
+        ));
+        assert!(
+            fixture
+                .shared
+                .node(ancestor)
+                .calls
+                .lock()
+                .unwrap()
+                .is_empty()
+        );
+        // A replacement is visible but cannot authorize a previously resolved lineage.
+        assert!(!fixture.shared.node(ancestor).data.lock().unwrap().hidden);
+    }
+}
+
 fn observe_request(path: &str, depth: u32) -> ObserveRequest {
     ObserveRequest {
         path: path.into(),
         depth,
     }
 }
-fn fetch_request(reference: &str) -> FetchInterfaceRequest {
+fn fetch_request(reference: &wip_protocol::InterfaceReference) -> FetchInterfaceRequest {
     FetchInterfaceRequest {
-        interface: reference.into(),
+        interface: reference.clone(),
     }
 }
 fn success<T: std::fmt::Debug>(response: DecodedResponse<T>) -> T {
@@ -868,8 +1043,8 @@ fn principal_views_hide_children_and_guessed_descendants_for_observation_and_cal
             .lock()
             .unwrap()
             .iter()
-            .all(|seen| !seen.path.starts_with("/secret/")),
-        "hidden descendants were resolved"
+            .all(|seen| seen.stage == "resolve"),
+        "hidden lineage was published, enumerated, or dispatched"
     );
     assert!(
         fixture
@@ -1634,8 +1809,8 @@ fn policy_panics_and_guessed_operation_diagnostics_do_not_leak_to_http() {
     // This valid metadata names a nonexistent operation; bypass client-side
     // descriptor validation to exercise server diagnostics for untrusted names.
     let body = format!(
-        r#"{{"target":{{"path":"/added"}},"interface":{{"reference":"{}"}},"operation":"{}","arguments":{{}}}}"#,
-        fixture.custom, POLICY_SECRET
+        r#"{{"target":{{"path":"/added"}},"interface":{{"reference":{{"scope":"{}","name":"{}"}}}},"operation":"{}","arguments":{{}}}}"#,
+        fixture.custom.scope, fixture.custom.name, POLICY_SECRET
     );
     let request = http::Request::builder()
         .method(http::Method::POST)

crates/wip-host/README.md

@@ -10,6 +10,10 @@ wip-host = "0.1.0"
 wip-interface = "0.1.0"
 ```
 
+Protocol publication and dispatch use `wip_protocol::InterfaceReference { scope, name }` and compare both fields exactly. The legacy `InterfaceRef` registration token remains Host-private: `protocol_reference()` maps its opaque string verbatim to the name at root scope `/`, without parsing it. Registry lookup and fetch accept structured references; non-root references do not resolve legacy registrations. Legacy responses omit `scope_ref`.
+
+Malformed interface-reference shapes fail calls as `InvalidRequest` before object resolution. A well-shaped reference outside the target path's ancestor-or-self scope fails at the membership check as `InterfaceMismatch`.
+
 See the [API documentation](https://docs.rs/wip-host) for publication, provider, execution-context, and effect-guarantee boundaries.
 
 Licensed under either of Apache-2.0 or MIT at your option.

crates/wip-host/src/lib.rs

@@ -49,8 +49,8 @@ pub use wip_protocol::{
     Target,
 };
 use wip_protocol::{
-    FetchInterfaceRequest, FetchInterfaceResponse, InterfaceDescriptor, Object, ProtocolError,
-    ProtocolErrorCode, ValidationError, Value,
+    FetchInterfaceRequest, FetchInterfaceResponse, InterfaceDescriptor, InterfaceReference, Object,
+    ProtocolError, ProtocolErrorCode, ValidationError, Value,
 };
 
 /// Opaque bytes used as a conditional execution precondition.
@@ -192,11 +192,22 @@ impl ExecutionContext {
 pub struct InterfaceRef(String);
 
 impl InterfaceRef {
-    /// Returns the opaque reference for a protocol transport.
+    /// Returns the legacy opaque registration reference.
     #[must_use]
     pub fn as_str(&self) -> &str {
         &self.0
     }
+
+    /// Maps the legacy registration reference to a root-scoped protocol reference.
+    ///
+    /// The opaque registration string is copied as the name without parsing it.
+    #[must_use]
+    pub fn protocol_reference(&self) -> InterfaceReference {
+        InterfaceReference {
+            scope: "/".into(),
+            name: self.0.clone(),
+        }
+    }
 }
 
 /// One atomic observation of an interface reference, descriptor, and validator.
@@ -229,13 +240,14 @@ impl InterfaceObservation {
     /// local validation error.
     pub fn protocol_response(&self) -> Result<FetchInterfaceResponse, ProtocolError> {
         let response = FetchInterfaceResponse {
-            interface: self.reference.0.clone(),
+            interface: self.reference.protocol_reference(),
             descriptor: self.descriptor.clone(),
+            scope_ref: None,
             validator: self.validator.as_ref().map(|validator| validator.0.clone()),
         };
         response
             .validate_for(&FetchInterfaceRequest {
-                interface: self.reference.0.clone(),
+                interface: self.reference.protocol_reference(),
             })
             .map_err(|_| ProtocolError {
                 code: ProtocolErrorCode::Internal,
@@ -354,10 +366,16 @@ impl InterfaceRegistry {
         })
     }
 
-    /// Resolves a transport-provided opaque reference string in this registry.
+    /// Resolves a structured protocol reference to a legacy registration token.
+    ///
+    /// Legacy artifacts are published only at root scope. The name is looked up
+    /// verbatim; no scope or name parsing is performed.
     #[must_use]
-    pub fn resolve(&self, reference: &str) -> Option<InterfaceRef> {
-        let reference = InterfaceRef(reference.to_owned());
+    pub fn resolve(&self, reference: &InterfaceReference) -> Option<InterfaceRef> {
+        if reference.scope != "/" {
+            return None;
+        }
+        let reference = InterfaceRef(reference.name.clone());
         self.artifacts.contains_key(&reference).then_some(reference)
     }
 
@@ -367,14 +385,20 @@ impl InterfaceRegistry {
         self.artifacts.get(reference).map(Self::observation)
     }
 
-    /// Implements canonical `fetch_interface` semantics for an opaque reference.
+    /// Implements canonical `fetch_interface` semantics for a structured reference.
     ///
-    /// Unknown and currently unpublished references map to `InterfaceNotFound`,
-    /// not object membership errors or authorization failures.
-    pub fn fetch_interface(&self, reference: &str) -> Result<InterfaceObservation, ProtocolError> {
-        let reference = InterfaceRef(reference.to_owned());
-        self.artifacts
-            .get(&reference)
+    /// Malformed references map to `InvalidRequest`. Unknown and currently
+    /// unpublished references (including non-root scopes) map to `InterfaceNotFound`.
+    pub fn fetch_interface(
+        &self,
+        reference: &InterfaceReference,
+    ) -> Result<InterfaceObservation, ProtocolError> {
+        reference.validate().map_err(|error| ProtocolError {
+            code: ProtocolErrorCode::InvalidRequest,
+            message: error.to_string(),
+        })?;
+        self.resolve(reference)
+            .and_then(|reference| self.artifacts.get(&reference))
             .map(Self::observation)
             .ok_or_else(|| ProtocolError {
                 code: ProtocolErrorCode::InterfaceNotFound,
@@ -625,7 +649,7 @@ impl<T: WipObject> PublishedObject<T> {
             interfaces: self
                 .interfaces
                 .iter()
-                .map(|bound| bound.artifact.reference.0.clone())
+                .map(|bound| bound.artifact.reference.protocol_reference())
                 .collect(),
             r#ref: self.implementation.reference().map(str::to_owned),
             validator: self
@@ -678,10 +702,17 @@ impl<T: WipObject> PublishedObject<T> {
             );
         }
 
+        if interface.reference.validate_for_path(&target.path).is_err() {
+            return pre_dispatch_failure(
+                CallErrorKind::InterfaceMismatch,
+                "interface scope is not an ancestor of the target path",
+            );
+        }
+
         let Some(bound) = self
             .interfaces
             .iter()
-            .find(|bound| bound.artifact.reference.as_str() == interface.reference.as_str())
+            .find(|bound| bound.artifact.reference.protocol_reference() == interface.reference)
         else {
             return pre_dispatch_failure(
                 CallErrorKind::InterfaceMismatch,
@@ -1039,6 +1070,11 @@ pub trait ObjectProvider {
     ) -> Result<CallResult, CallError> {
         wip_protocol::validate_path(&request.target.path)
             .map_err(|error| CallError::new(CallErrorKind::InvalidRequest, error.to_string()))?;
+        request
+            .interface
+            .reference
+            .validate()
+            .map_err(|error| CallError::new(CallErrorKind::InvalidRequest, error.to_string()))?;
         let path = request.target.path.clone();
         let execution = catch_unwind(AssertUnwindSafe(|| {
             self.execute_operation(context, &path, |publication| {
@@ -1088,6 +1124,10 @@ pub trait ObjectProvider {
     ) -> Result<CallResult, CallError> {
         wip_protocol::validate_path(&target.path)
             .map_err(|error| CallError::new(CallErrorKind::InvalidRequest, error.to_string()))?;
+        interface
+            .reference
+            .validate()
+            .map_err(|error| CallError::new(CallErrorKind::InvalidRequest, error.to_string()))?;
         let path = target.path.clone();
         let execution = catch_unwind(AssertUnwindSafe(|| {
             self.execute_operation(context, &path, |publication| {

crates/wip-host/tests/host.rs

@@ -35,7 +35,10 @@ fn principal_projection_orders_subsets_and_rejects_unimplemented_or_duplicate_to
         .unwrap();
     assert_eq!(
         projected.protocol_object().interfaces,
-        vec![write.reference().as_str(), read.reference().as_str()]
+        vec![
+            write.reference().protocol_reference(),
+            read.reference().protocol_reference()
+        ]
     );
     assert!(
         publication()
@@ -58,14 +61,18 @@ fn principal_projection_orders_subsets_and_rejects_unimplemented_or_duplicate_to
             .interfaces
             .is_empty()
     );
-    let full = registry.fetch_interface(read.reference().as_str()).unwrap();
+    let full = registry
+        .fetch_interface(&read.reference().protocol_reference())
+        .unwrap();
     let filtered = full
         .clone()
         .project_operations(|operation| operation == "label");
     assert_eq!(filtered.descriptor.operations.len(), 1);
     assert_eq!(full.descriptor.operations.len(), 3);
     assert_eq!(
-        registry.fetch_interface(read.reference().as_str()).unwrap(),
+        registry
+            .fetch_interface(&read.reference().protocol_reference())
+            .unwrap(),
         full
     );
 }
@@ -478,7 +485,8 @@ fn request(
             validator: object_validator.map(<[u8]>::to_vec),
         },
         interface: InterfaceTarget {
-            reference: reference.as_str().to_owned(),
+            reference: reference.protocol_reference(),
+            scope_ref: None,
             validator: interface_validator.map(<[u8]>::to_vec),
         },
         operation: operation.into(),
@@ -497,17 +505,22 @@ fn registry_returns_atomic_canonical_observation_without_rewriting_descriptor()
     let reference = provider.reader.reference();
 
     assert_ne!(reference.as_str(), "Reader");
-    let observation = registry.fetch_interface(reference.as_str()).unwrap();
+    let observation = registry
+        .fetch_interface(&reference.protocol_reference())
+        .unwrap();
     assert_eq!(observation.reference, *reference);
     assert_eq!(observation.descriptor, ReaderDefinition::descriptor());
     assert_eq!(observation.validator, Some(Validator::new(b"schema-v1")));
     let response = observation.protocol_response().unwrap();
-    assert_eq!(response.interface, reference.as_str());
+    assert_eq!(response.interface, reference.protocol_reference());
+    assert_eq!(response.scope_ref, None);
     assert_eq!(response.descriptor, ReaderDefinition::descriptor());
     assert_eq!(response.validator.as_deref(), Some(b"schema-v1".as_slice()));
     response.descriptor.validate().unwrap();
 
-    let mut invalid_observation = registry.fetch_interface(reference.as_str()).unwrap();
+    let mut invalid_observation = registry
+        .fetch_interface(&reference.protocol_reference())
+        .unwrap();
     let duplicate_operation = invalid_observation.descriptor.operations[0].clone();
     invalid_observation
         .descriptor
@@ -516,7 +529,12 @@ fn registry_returns_atomic_canonical_observation_without_rewriting_descriptor()
     let invalid_response = invalid_observation.protocol_response().unwrap_err();
     assert_eq!(invalid_response.code, ProtocolErrorCode::Internal);
 
-    let error = registry.fetch_interface("unknown").unwrap_err();
+    let error = registry
+        .fetch_interface(&wip_protocol::InterfaceReference {
+            scope: "/".into(),
+            name: "unknown".into(),
+        })
+        .unwrap_err();
     assert_eq!(error.code, ProtocolErrorCode::InterfaceNotFound);
 }
 
@@ -532,8 +550,8 @@ fn canonical_object_projection_supports_optional_metadata_and_ordered_sets() {
     assert_eq!(
         object.interfaces,
         vec![
-            provider.writer.reference().as_str().to_owned(),
-            provider.reader.reference().as_str().to_owned(),
+            provider.writer.reference().protocol_reference(),
+            provider.reader.reference().protocol_reference(),
         ]
     );
     assert!(!format!("{object:?}").contains("secret-handle"));
@@ -814,7 +832,8 @@ fn descriptor_guided_decoder_runs_inside_canonical_resolution_boundary() {
                 validator: Some(b"stale".to_vec()),
             },
             InterfaceTarget {
-                reference: hidden.reference().as_str().into(),
+                reference: hidden.reference().protocol_reference(),
+                scope_ref: None,
                 validator: None,
             },
             "missing".into(),
@@ -832,7 +851,8 @@ fn descriptor_guided_decoder_runs_inside_canonical_resolution_boundary() {
                 validator: Some(b"stale".to_vec()),
             },
             InterfaceTarget {
-                reference: hidden.reference().as_str().into(),
+                reference: hidden.reference().protocol_reference(),
+                scope_ref: None,
                 validator: None,
             },
             "hidden".into(),
@@ -850,7 +870,8 @@ fn descriptor_guided_decoder_runs_inside_canonical_resolution_boundary() {
                 validator: Some(b"object-v1".to_vec()),
             },
             InterfaceTarget {
-                reference: hidden.reference().as_str().into(),
+                reference: hidden.reference().protocol_reference(),
+                scope_ref: None,
                 validator: None,
             },
             "hidden".into(),
@@ -868,7 +889,8 @@ fn descriptor_guided_decoder_runs_inside_canonical_resolution_boundary() {
                 validator: Some(b"object-v1".to_vec()),
             },
             InterfaceTarget {
-                reference: provider.reader.reference().as_str().into(),
+                reference: provider.reader.reference().protocol_reference(),
+                scope_ref: None,
                 validator: Some(b"schema-v1".to_vec()),
             },
             "add".into(),
@@ -1122,3 +1144,100 @@ fn execution_context_is_propagated_and_preflight_prevents_invocation() {
     );
     assert_eq!(provider.calls.get(), calls);
 }
+
+#[test]
+fn legacy_registry_boundaries_copy_names_verbatim_and_match_exact_scope() {
+    let (registry, provider, _) = registry_and_provider();
+    let legacy = provider.writer.reference();
+    let reference = legacy.protocol_reference();
+    assert_eq!(reference.scope, "/");
+    assert_eq!(reference.name, legacy.as_str());
+    // The registry's colon-delimited name remains opaque, not parsed.
+    assert!(reference.name.starts_with("wip-interface:"));
+    assert_eq!(registry.resolve(&reference).as_ref(), Some(legacy));
+    let nested = wip_protocol::InterfaceReference {
+        scope: "/open".into(),
+        name: reference.name.clone(),
+    };
+    assert!(registry.resolve(&nested).is_none());
+    assert_eq!(
+        registry.fetch_interface(&nested).unwrap_err().code,
+        ProtocolErrorCode::InterfaceNotFound
+    );
+    let malformed = wip_protocol::InterfaceReference {
+        scope: "relative".into(),
+        name: reference.name,
+    };
+    assert_eq!(
+        registry.fetch_interface(&malformed).unwrap_err().code,
+        ProtocolErrorCode::InvalidRequest
+    );
+}
+
+#[test]
+fn call_reference_shape_precedes_resolution_and_scope_membership_is_exact() {
+    let (_, provider, _) = registry_and_provider();
+    for (scope, name) in [("relative", "valid"), ("/", ""), ("/bad/", "valid")] {
+        let mut call = request(
+            "/open",
+            None,
+            provider.writer.reference(),
+            None,
+            "label",
+            BTreeMap::new(),
+        );
+        call.interface.reference = wip_protocol::InterfaceReference {
+            scope: scope.into(),
+            name: name.into(),
+        };
+        assert_eq!(
+            provider.call_operation(call.clone()).unwrap_err().kind(),
+            CallErrorKind::InvalidRequest
+        );
+        assert_eq!(
+            provider
+                .call_operation_with_context_and_decoder(
+                    &ExecutionContext::new(),
+                    call.target,
+                    call.interface,
+                    call.operation,
+                    |_| Ok::<_, ()>(BTreeMap::new()),
+                )
+                .unwrap_err()
+                .kind(),
+            CallErrorKind::InvalidRequest
+        );
+    }
+    assert_eq!(provider.resolutions.get(), 0);
+    // /other is outside the target scope; /open is self but has no legacy artifact.
+    for scope in ["/other", "/open"] {
+        let mut call = request(
+            "/open",
+            None,
+            provider.writer.reference(),
+            None,
+            "label",
+            BTreeMap::new(),
+        );
+        call.interface.reference.scope = scope.into();
+        assert_eq!(
+            provider.call_operation(call.clone()).unwrap_err().kind(),
+            CallErrorKind::InterfaceMismatch
+        );
+        assert_eq!(
+            provider
+                .call_operation_with_context_and_decoder(
+                    &ExecutionContext::new(),
+                    call.target,
+                    call.interface,
+                    call.operation,
+                    |_| -> Result<BTreeMap<String, Value>, ()> { panic!("must not decode") },
+                )
+                .unwrap_err()
+                .kind(),
+            CallErrorKind::InterfaceMismatch
+        );
+    }
+    assert_eq!(provider.calls.get(), 0);
+    assert_eq!(provider.authorization_checks.get(), 0);
+}

crates/wip-http/README.md

@@ -26,6 +26,27 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 }
 ```
 
+## Interface references and scope identity
+
+Every interface reference is encoded as an exact JSON object with required
+`scope` and `name` strings, for example `{"scope":"/github","name":"issue.read"}`.
+This applies to `Object.interfaces` elements, fetch request/response `interface`,
+and call `interface.reference`. Scope must be a canonical absolute Worldspace
+path and name must be nonempty. Legacy opaque strings, short-form strings,
+relative scopes, missing fields, and extra members are rejected. Unicode, `::`,
+and `#` in names remain literal data; comparison uses decoded field values,
+independent of JSON member order and escapes. HTTP endpoint prefixes do not
+change Worldspace scope.
+
+Fetch responses and call interface targets additionally carry optional
+`scope_ref`, an opaque string copied from the scope Object's `ref` observation.
+It is not base64 and is not part of interface identity. Absent values are omitted;
+null and nonstring values are rejected. Descriptor-independent call metadata
+validates reference shape, but leaves scope ancestry and identity preconditions
+to the Host's `InterfaceMismatch` check, preserving protocol error precedence.
+Invalid success responses remain client-local `InvalidResponse` errors; protocol
+error envelopes and transport failures retain their existing classification.
+
 See the [API documentation](https://docs.rs/wip-http) for codec and failure-boundary details.
 
 Licensed under either of Apache-2.0 or MIT at your option.

crates/wip-http/src/codec.rs

@@ -296,11 +296,14 @@ pub fn decode_observe_request(body: &[u8], limits: Limits) -> Result<ObserveRequ
 }
 
 /// Encodes a `fetch_interface` HTTP request.
+///
+/// Validates reference shape without requiring a target Object path.
 pub fn encode_fetch_interface_request(
     endpoint: &Endpoint,
     value: &FetchInterfaceRequest,
     limits: Limits,
 ) -> Result<Request<Vec<u8>>, EncodeHttpError> {
+    value.interface.validate().map_err(CodecError::from)?;
     let body = json::serialize(
         &json::fetch_interface_request_to_json(value),
         BodyKind::Request,
@@ -358,6 +361,10 @@ impl CallOperationMetadata {
 }
 
 /// Decodes descriptor-independent `call_operation` routing metadata.
+///
+/// Reference shape is validated, but scope ancestry and `scope_ref` identity
+/// are left to Host resolution so `NotFound`, validator failures, and
+/// `InterfaceMismatch` retain their protocol precedence.
 pub fn decode_call_operation_metadata(
     body: &[u8],
     limits: Limits,

crates/wip-http/src/json.rs

@@ -8,9 +8,9 @@ use serde_json::{Map, Number, Value as Json};
 use wip_protocol::{
     CallOperationRequest, CallOperationResponse, Documentation, EnumCase, FetchInterfaceRequest,
     FetchInterfaceResponse, FieldDeclaration, INTERFACE_FORMAT_V1, InterfaceDescriptor,
-    InterfaceTarget, MAX_SAFE_INTEGER, MIN_SAFE_INTEGER, Object, ObjectObservation, ObserveRequest,
-    ObserveResponse, OperationDeclaration, ParameterDeclaration, ReturnDeclaration, Target,
-    TypeDeclaration, TypeExpr, UnionCase, Value,
+    InterfaceReference, InterfaceTarget, MAX_SAFE_INTEGER, MIN_SAFE_INTEGER, Object,
+    ObjectObservation, ObserveRequest, ObserveResponse, OperationDeclaration, ParameterDeclaration,
+    ReturnDeclaration, Target, TypeDeclaration, TypeExpr, UnionCase, Value,
 };
 
 use crate::{BodyKind, CodecError, Limits};
@@ -285,8 +285,25 @@ pub(crate) fn observe_request_from_json(value: &Json) -> Result<ObserveRequest,
     Ok(request)
 }
 
+fn interface_reference_to_json(reference: &InterfaceReference) -> Json {
+    serde_json::json!({"scope": reference.scope, "name": reference.name})
+}
+
+fn interface_reference_from_json(
+    value: &Json,
+    field: &str,
+) -> Result<InterfaceReference, CodecError> {
+    let fields = exact_object(value, field, &["scope", "name"])?;
+    let reference = InterfaceReference {
+        scope: string(required(fields, "scope")?, &qualified(field, "scope"))?,
+        name: string(required(fields, "name")?, &qualified(field, "name"))?,
+    };
+    reference.validate()?;
+    Ok(reference)
+}
+
 pub(crate) fn fetch_interface_request_to_json(request: &FetchInterfaceRequest) -> Json {
-    serde_json::json!({"interface": request.interface})
+    serde_json::json!({"interface": interface_reference_to_json(&request.interface)})
 }
 
 pub(crate) fn fetch_interface_request_from_json(
@@ -294,7 +311,7 @@ pub(crate) fn fetch_interface_request_from_json(
 ) -> Result<FetchInterfaceRequest, CodecError> {
     let fields = exact_object(value, "request", &["interface"])?;
     Ok(FetchInterfaceRequest {
-        interface: string(required(fields, "interface")?, "interface")?,
+        interface: interface_reference_from_json(required(fields, "interface")?, "interface")?,
     })
 }
 
@@ -308,8 +325,7 @@ pub(crate) fn object_to_json(object: &Object) -> Json {
             object
                 .interfaces
                 .iter()
-                .cloned()
-                .map(Json::String)
+                .map(interface_reference_to_json)
                 .collect(),
         ),
     );
@@ -327,7 +343,7 @@ pub(crate) fn object_from_json(value: &Json, field: &str) -> Result<Object, Code
     let interfaces = array(required(fields, "interfaces")?, "interfaces")?
         .iter()
         .enumerate()
-        .map(|(index, value)| string(value, &format!("interfaces[{index}]")))
+        .map(|(index, value)| interface_reference_from_json(value, &format!("interfaces[{index}]")))
         .collect::<Result<Vec<_>, _>>()?;
     let object = Object {
         name: string(required(fields, "name")?, "name")?,
@@ -745,7 +761,11 @@ pub(crate) fn descriptor_from_json(
 
 pub(crate) fn fetch_interface_response_to_json(response: &FetchInterfaceResponse) -> Json {
     let mut fields = Map::new();
-    fields.insert("interface".into(), Json::String(response.interface.clone()));
+    fields.insert(
+        "interface".into(),
+        interface_reference_to_json(&response.interface),
+    );
+    insert_optional_string(&mut fields, "scope_ref", &response.scope_ref);
     fields.insert(
         "descriptor".into(),
         descriptor_to_json(&response.descriptor),
@@ -757,8 +777,15 @@ pub(crate) fn fetch_interface_response_to_json(response: &FetchInterfaceResponse
 pub(crate) fn fetch_interface_response_from_json(
     value: &Json,
 ) -> Result<FetchInterfaceResponse, CodecError> {
-    let fields = exact_object(value, "response", &["interface", "descriptor", "validator"])?;
-    let interface = string(required(fields, "interface")?, "interface")?;
+    let fields = exact_object(
+        value,
+        "response",
+        &["interface", "scope_ref", "descriptor", "validator"],
+    )?;
+    let interface = interface_reference_from_json(required(fields, "interface")?, "interface")?;
+    let scope_ref = optional(fields, "scope_ref")?
+        .map(|value| string(value, "scope_ref"))
+        .transpose()?;
     let validator = optional(fields, "validator")?
         .map(|value| base64_decode(value, "validator"))
         .transpose()?;
@@ -780,6 +807,7 @@ pub(crate) fn fetch_interface_response_from_json(
     };
     Ok(FetchInterfaceResponse {
         interface,
+        scope_ref,
         descriptor,
         validator,
     })
@@ -1121,18 +1149,25 @@ fn target_from_json(value: &Json, field: &str) -> Result<Target, CodecError> {
 
 fn interface_target_to_json(target: &InterfaceTarget) -> Json {
     let mut fields = Map::new();
-    fields.insert("reference".into(), Json::String(target.reference.clone()));
+    fields.insert(
+        "reference".into(),
+        interface_reference_to_json(&target.reference),
+    );
+    insert_optional_string(&mut fields, "scope_ref", &target.scope_ref);
     insert_optional_bytes(&mut fields, "validator", &target.validator);
     Json::Object(fields)
 }
 
 fn interface_target_from_json(value: &Json, field: &str) -> Result<InterfaceTarget, CodecError> {
-    let fields = exact_object(value, field, &["reference", "validator"])?;
+    let fields = exact_object(value, field, &["reference", "scope_ref", "validator"])?;
     Ok(InterfaceTarget {
-        reference: string(
+        reference: interface_reference_from_json(
             required(fields, "reference")?,
             &qualified(field, "reference"),
         )?,
+        scope_ref: optional(fields, "scope_ref")?
+            .map(|value| string(value, &qualified(field, "scope_ref")))
+            .transpose()?,
         validator: optional(fields, "validator")?
             .map(|value| base64_decode(value, &qualified(field, "validator")))
             .transpose()?,

crates/wip-http/src/lib.rs

@@ -12,6 +12,14 @@
 //! encoded in JSON bodies using canonical RFC 4648 Section 4 base64; this crate
 //! does not infer WIP validator semantics from `ETag` or `If-Match`.
 //!
+//! Interface references use exact JSON objects with required `scope` and `name`
+//! strings in every position. Legacy strings and display shorthand are rejected.
+//! Scope is a canonical absolute Worldspace path, not an HTTP endpoint prefix.
+//! Optional `scope_ref` metadata on fetch responses and call interface targets is
+//! an opaque string, never base64; absent fields are omitted and null is rejected.
+//! Call metadata validates reference shape without resolving scope ancestry or
+//! identity, which remain Host checks with `InterfaceMismatch` precedence.
+//!
 //! ```
 //! use wip_http::{Endpoint, Limits, encode_observe_request};
 //! use wip_protocol::ObserveRequest;

crates/wip-http/tests/codecs.rs

@@ -4,9 +4,9 @@ use wip_http::http::StatusCode;
 use wip_http::wip_protocol::{
     CallOperationRequest, CallOperationResponse, Documentation, EnumCase, FetchInterfaceRequest,
     FetchInterfaceResponse, FieldDeclaration, INTERFACE_FORMAT_V1, InterfaceDescriptor,
-    InterfaceTarget, MAX_SAFE_INTEGER, Object, ObjectObservation, ObserveRequest,
-    OperationDeclaration, ParameterDeclaration, ReturnDeclaration, Target, TypeDeclaration,
-    TypeExpr, UnionCase, Value,
+    InterfaceReference, InterfaceTarget, MAX_SAFE_INTEGER, Object, ObjectObservation,
+    ObserveRequest, OperationDeclaration, ParameterDeclaration, ReturnDeclaration, Target,
+    TypeDeclaration, TypeExpr, UnionCase, Value,
 };
 use wip_http::{
     ClientResponseError, CodecError, DecodedResponse, Endpoint, InvalidResponseKind, Limits,
@@ -25,11 +25,18 @@ fn endpoint() -> Endpoint {
     Endpoint::parse("https://example.test/wip").unwrap()
 }
 
+fn reference(scope: &str, name: &str) -> InterfaceReference {
+    InterfaceReference {
+        scope: scope.into(),
+        name: name.into(),
+    }
+}
+
 fn object(name: &str, validator: &[u8]) -> Object {
     Object {
         name: name.into(),
         description: Some("description".into()),
-        interfaces: vec!["interface-v1".into()],
+        interfaces: vec![reference("/", "interface-v1")],
         r#ref: Some(format!("object:{name}")),
         validator: Some(validator.to_vec()),
     }
@@ -152,7 +159,8 @@ fn call_request() -> CallOperationRequest {
             validator: Some(vec![0, 1, 2, 255]),
         },
         interface: InterfaceTarget {
-            reference: "interface-v1".into(),
+            reference: reference("/", "interface-v1"),
+            scope_ref: None,
             validator: Some(vec![9, 8, 7]),
         },
         operation: "everything".into(),
@@ -206,7 +214,7 @@ fn every_single_interaction_request_accepts_json() {
     let fetch_interface = encode_fetch_interface_request(
         &endpoint(),
         &FetchInterfaceRequest {
-            interface: "interface-v1".into(),
+            interface: reference("/", "interface-v1"),
         },
         limits(),
     )
@@ -286,7 +294,7 @@ fn observe_and_interface_round_trip_nested_logical_models() {
     );
 
     let interface_request = FetchInterfaceRequest {
-        interface: "interface-v1".into(),
+        interface: reference("/", "interface-v1"),
     };
     let encoded_request =
         encode_fetch_interface_request(&endpoint(), &interface_request, limits()).unwrap();
@@ -296,6 +304,7 @@ fn observe_and_interface_round_trip_nested_logical_models() {
     );
     let interface = FetchInterfaceResponse {
         interface: interface_request.interface.clone(),
+        scope_ref: None,
         descriptor: descriptor(),
         validator: Some(vec![4, 5, 6, 255]),
     };
@@ -383,7 +392,7 @@ fn malformed_unknown_null_and_noncanonical_base64_are_rejected() {
     let descriptor = descriptor();
     let body = serde_json::to_vec(&serde_json::json!({
         "target": {"path": "/items/123", "validator": null},
-        "interface": {"reference": "interface-v1"},
+        "interface": {"reference": {"scope": "/", "name": "interface-v1"}},
         "operation": "everything",
         "arguments": {}
     }))
@@ -443,10 +452,11 @@ fn caller_limits_remain_local_codec_failures() {
 #[test]
 fn unsupported_descriptor_format_is_client_local() {
     let request = FetchInterfaceRequest {
-        interface: "interface-v1".into(),
+        interface: reference("/", "interface-v1"),
     };
     let mut interface = FetchInterfaceResponse {
         interface: request.interface.clone(),
+        scope_ref: None,
         descriptor: descriptor(),
         validator: None,
     };
@@ -462,7 +472,7 @@ fn unsupported_descriptor_format_is_client_local() {
         .status(StatusCode::OK)
         .header("content-type", "application/json; charset=utf-8")
         .body(
-            br#"{"interface":"interface-v1","descriptor":{"format":"wip-interface/2","future_shape":true}}"#
+            br#"{"interface":{"scope":"/","name":"interface-v1"},"descriptor":{"format":"wip-interface/2","future_shape":true}}"#
                 .to_vec(),
         )
         .unwrap();
@@ -473,8 +483,8 @@ fn unsupported_descriptor_format_is_client_local() {
     ));
 
     for malformed in [
-        br#"{"interface":"wrong","descriptor":{"format":"wip-interface/2"}}"#.as_slice(),
-        br#"{"interface":"interface-v1","descriptor":{"format":"wip-interface/2"},"validator":null}"#
+        br#"{"interface":{"scope":"/","name":"wrong"},"descriptor":{"format":"wip-interface/2"}}"#.as_slice(),
+        br#"{"interface":{"scope":"/","name":"interface-v1"},"descriptor":{"format":"wip-interface/2"},"validator":null}"#
             .as_slice(),
     ] {
         let response = wip_http::http::Response::builder()

crates/wip-http/tests/references.rs

@@ -0,0 +1,740 @@
+use std::collections::BTreeMap;
+
+use serde_json::{Value as Json, json};
+use wip_http::http::{Response, StatusCode};
+use wip_http::wip_protocol::{
+    CallOperationRequest, FetchInterfaceRequest, FetchInterfaceResponse, INTERFACE_FORMAT_V1,
+    InterfaceDescriptor, InterfaceReference, InterfaceTarget, Object, ObjectObservation,
+    ObserveRequest, OperationDeclaration, ProtocolError, ProtocolErrorCode, ProtocolInteraction,
+    ReturnDeclaration, Target, TypeExpr,
+};
+use wip_http::{
+    ClientResponseError, CodecError, DecodedResponse, Endpoint, InvalidResponseKind, Limits,
+    TransportFailureKind, decode_call_operation_metadata, decode_call_operation_request,
+    decode_call_operation_response, decode_fetch_interface_request,
+    decode_fetch_interface_response, decode_observe_response, encode_call_operation_request,
+    encode_fetch_interface_request, encode_fetch_interface_response, encode_observe_response,
+    encode_protocol_error_response,
+};
+
+fn limits() -> Limits {
+    Limits::new(64 * 1024, 64 * 1024, 64).unwrap()
+}
+
+fn endpoint() -> Endpoint {
+    Endpoint::parse("https://example.test/deployment/prefix").unwrap()
+}
+
+fn reference(scope: &str, name: &str) -> InterfaceReference {
+    InterfaceReference {
+        scope: scope.into(),
+        name: name.into(),
+    }
+}
+
+fn descriptor() -> InterfaceDescriptor {
+    InterfaceDescriptor {
+        format: INTERFACE_FORMAT_V1.into(),
+        documentation: None,
+        types: vec![],
+        operations: vec![OperationDeclaration {
+            name: "run#::操作".into(),
+            documentation: None,
+            parameters: vec![],
+            returns: ReturnDeclaration {
+                documentation: None,
+                r#type: TypeExpr::Unit,
+            },
+        }],
+    }
+}
+
+fn call(reference: InterfaceReference, scope_ref: Option<String>) -> CallOperationRequest {
+    CallOperationRequest {
+        target: Target {
+            path: "/世界::#/item".into(),
+            validator: Some(vec![0, 255]),
+        },
+        interface: InterfaceTarget {
+            reference,
+            scope_ref,
+            validator: Some(vec![1, 255]),
+        },
+        operation: "run#::操作".into(),
+        arguments: BTreeMap::new(),
+    }
+}
+
+fn observation(references: Vec<InterfaceReference>) -> ObjectObservation {
+    ObjectObservation {
+        object: Object {
+            name: "item".into(),
+            description: None,
+            interfaces: references,
+            r#ref: None,
+            validator: None,
+        },
+        children: None,
+    }
+}
+
+fn observe_request() -> ObserveRequest {
+    ObserveRequest {
+        path: "/世界::#/item".into(),
+        depth: 0,
+    }
+}
+
+fn response(status: StatusCode, value: Json) -> Response<Vec<u8>> {
+    raw_response(status, &serde_json::to_vec(&value).unwrap())
+}
+
+fn raw_response(status: StatusCode, body: &[u8]) -> Response<Vec<u8>> {
+    Response::builder()
+        .status(status)
+        .header("content-type", "application/json")
+        .body(body.to_vec())
+        .unwrap()
+}
+
+fn fetch_json(interface: Json) -> Json {
+    json!({
+        "interface": interface,
+        "descriptor": {"format": INTERFACE_FORMAT_V1, "types": [], "operations": []}
+    })
+}
+
+fn call_json(reference: Json) -> Json {
+    json!({
+        "target": {"path": "/世界::#/item"},
+        "interface": {"reference": reference},
+        "operation": "run#::操作",
+        "arguments": {}
+    })
+}
+
+fn invalid_success<T: std::fmt::Debug>(result: Result<T, ClientResponseError>) {
+    assert!(matches!(
+        result.unwrap_err(),
+        ClientResponseError::InvalidResponse {
+            kind: InvalidResponseKind::InvalidSuccessBody,
+            ..
+        }
+    ));
+}
+
+#[test]
+fn exact_structured_reference_is_encoded_and_round_tripped_in_every_position() {
+    let interface_ref = reference("/世界::#", "é::接口#read/with\"quote\\slash");
+    let expected = json!({"scope": interface_ref.scope, "name": interface_ref.name});
+    let fetch_request = FetchInterfaceRequest {
+        interface: interface_ref.clone(),
+    };
+    let encoded = encode_fetch_interface_request(&endpoint(), &fetch_request, limits()).unwrap();
+    assert_eq!(
+        encoded.uri().path(),
+        "/deployment/prefix/v1/fetch_interface"
+    );
+    assert_eq!(
+        serde_json::from_slice::<Json>(encoded.body()).unwrap(),
+        json!({"interface": expected})
+    );
+    assert_eq!(
+        decode_fetch_interface_request(encoded.body(), limits()).unwrap(),
+        fetch_request
+    );
+
+    let fetch_response = FetchInterfaceResponse {
+        interface: interface_ref.clone(),
+        scope_ref: Some("opaque:世界::# not base64!".into()),
+        descriptor: descriptor(),
+        validator: Some(vec![1, 255]),
+    };
+    let encoded =
+        encode_fetch_interface_response(&fetch_request, &fetch_response, limits()).unwrap();
+    let body: Json = serde_json::from_slice(encoded.body()).unwrap();
+    assert_eq!(body["interface"], expected);
+    assert_eq!(body["scope_ref"], "opaque:世界::# not base64!");
+    assert_eq!(body["validator"], "Af8=");
+    assert_eq!(
+        decode_fetch_interface_response(&fetch_request, &encoded, limits()).unwrap(),
+        DecodedResponse::Success(fetch_response)
+    );
+
+    let observation = observation(vec![interface_ref.clone(), reference("/", "root")]);
+    let encoded = encode_observe_response(&observe_request(), &observation, limits()).unwrap();
+    let body: Json = serde_json::from_slice(encoded.body()).unwrap();
+    assert_eq!(
+        body["object"]["interfaces"],
+        json!([expected, {"scope": "/", "name": "root"}])
+    );
+    assert_eq!(
+        decode_observe_response(&observe_request(), &encoded, limits()).unwrap(),
+        DecodedResponse::Success(observation)
+    );
+
+    let request = call(interface_ref, Some("opaque:世界::# not base64!".into()));
+    let encoded =
+        encode_call_operation_request(&endpoint(), &request, &descriptor(), limits()).unwrap();
+    let body: Json = serde_json::from_slice(encoded.body()).unwrap();
+    assert_eq!(body["interface"]["reference"], expected);
+    assert_eq!(body["interface"]["scope_ref"], "opaque:世界::# not base64!");
+    assert_eq!(body["interface"]["validator"], "Af8=");
+    assert_eq!(body["target"]["validator"], "AP8=");
+    assert_eq!(body["operation"], "run#::操作");
+    assert_eq!(
+        decode_call_operation_request(encoded.body(), &descriptor(), limits()).unwrap(),
+        request
+    );
+    assert_eq!(
+        decode_call_operation_metadata(encoded.body(), limits())
+            .unwrap()
+            .interface,
+        request.interface
+    );
+}
+
+#[test]
+fn malformed_reference_corpus_is_rejected_in_all_positions() {
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "interface-v1"),
+    };
+    for bad in [
+        json!("interface-v1"),
+        json!("/::interface-v1"),
+        json!("interface-v1#run"),
+        Json::Null,
+        json!(false),
+        json!(1),
+        json!([]),
+        json!({}),
+        json!({"name": "interface-v1"}),
+        json!({"scope": "/"}),
+        json!({"scope": null, "name": "interface-v1"}),
+        json!({"scope": 1, "name": "interface-v1"}),
+        json!({"scope": "/", "name": null}),
+        json!({"scope": "/", "name": []}),
+        json!({"scope": "/", "name": ""}),
+        json!({"scope": "/", "name": "interface-v1", "extra": true}),
+        json!({"scope": "/", "name": "interface-v1", "scope_ref": "identity"}),
+        json!({"Scope": "/", "name": "interface-v1"}),
+        json!({"scope": "", "name": "interface-v1"}),
+        json!({"scope": "relative", "name": "interface-v1"}),
+        json!({"scope": ".", "name": "interface-v1"}),
+        json!({"scope": "..", "name": "interface-v1"}),
+        json!({"scope": "/a/", "name": "interface-v1"}),
+        json!({"scope": "//a", "name": "interface-v1"}),
+        json!({"scope": "/a//b", "name": "interface-v1"}),
+        json!({"scope": "/a/./b", "name": "interface-v1"}),
+        json!({"scope": "/a/../b", "name": "interface-v1"}),
+    ] {
+        let body = serde_json::to_vec(&json!({"interface": bad})).unwrap();
+        assert!(
+            decode_fetch_interface_request(&body, limits()).is_err(),
+            "{bad}"
+        );
+        let body = serde_json::to_vec(&call_json(bad.clone())).unwrap();
+        assert!(
+            decode_call_operation_metadata(&body, limits()).is_err(),
+            "{bad}"
+        );
+        assert!(
+            decode_call_operation_request(&body, &descriptor(), limits()).is_err(),
+            "{bad}"
+        );
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &response(StatusCode::OK, fetch_json(bad.clone())),
+            limits(),
+        ));
+        let mut future = fetch_json(bad.clone());
+        future["descriptor"] = json!({"format": "future-format", "future": true});
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &response(StatusCode::OK, future),
+            limits(),
+        ));
+        invalid_success(decode_observe_response(
+            &observe_request(),
+            &response(
+                StatusCode::OK,
+                json!({"object": {"name": "item", "interfaces": [bad]}}),
+            ),
+            limits(),
+        ));
+    }
+}
+
+#[test]
+fn duplicate_reference_members_are_rejected_even_when_escaped_or_equal() {
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "x"),
+    };
+    for bad in [
+        r#"{"scope":"/","scope":"/","name":"x"}"#,
+        r#"{"scope":"/","name":"x","name":"x"}"#,
+        r#"{"scope":"/","name":"x","na\u006de":"x"}"#,
+    ] {
+        let fetch = format!(r#"{{"interface":{bad}}}"#);
+        assert!(matches!(
+            decode_fetch_interface_request(fetch.as_bytes(), limits()).unwrap_err(),
+            CodecError::InvalidJson(_)
+        ));
+        let call = format!(
+            r#"{{"target":{{"path":"/"}},"interface":{{"reference":{bad}}},"operation":"run","arguments":{{}}}}"#
+        );
+        assert!(matches!(
+            decode_call_operation_metadata(call.as_bytes(), limits()).unwrap_err(),
+            CodecError::InvalidJson(_)
+        ));
+        assert!(matches!(
+            decode_call_operation_request(call.as_bytes(), &descriptor(), limits()).unwrap_err(),
+            CodecError::InvalidJson(_)
+        ));
+        let fetch_response = format!(
+            r#"{{"interface":{bad},"descriptor":{{"format":"wip-interface/1","types":[],"operations":[]}}}}"#
+        );
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &raw_response(StatusCode::OK, fetch_response.as_bytes()),
+            limits(),
+        ));
+        let observe = format!(r#"{{"object":{{"name":"item","interfaces":[{bad}]}}}}"#);
+        invalid_success(decode_observe_response(
+            &observe_request(),
+            &raw_response(StatusCode::OK, observe.as_bytes()),
+            limits(),
+        ));
+    }
+}
+
+#[test]
+fn member_order_and_json_escapes_do_not_change_reference_identity() {
+    let expected = reference("/世界::#", "é::接口#");
+    let raw_reference = r#"{"name":"\u00e9::\u63a5\u53e3#","scope":"\/\u4e16\u754c::#"}"#;
+    let fetch = format!(r#"{{"interface":{raw_reference}}}"#);
+    let request = decode_fetch_interface_request(fetch.as_bytes(), limits()).unwrap();
+    assert_eq!(request.interface, expected);
+    let fetch_response = format!(
+        r#"{{"descriptor":{{"operations":[],"types":[],"format":"wip-interface/1"}},"interface":{raw_reference}}}"#
+    );
+    assert!(
+        matches!(decode_fetch_interface_response(&request, &raw_response(StatusCode::OK, fetch_response.as_bytes()), limits()).unwrap(), DecodedResponse::Success(value) if value.interface == expected)
+    );
+    let call = format!(
+        r#"{{"arguments":{{}},"operation":"run#::操作","interface":{{"reference":{raw_reference}}},"target":{{"path":"/世界::#/item"}}}}"#
+    );
+    assert_eq!(
+        decode_call_operation_metadata(call.as_bytes(), limits())
+            .unwrap()
+            .interface
+            .reference,
+        expected
+    );
+    assert_eq!(
+        decode_call_operation_request(call.as_bytes(), &descriptor(), limits())
+            .unwrap()
+            .interface
+            .reference,
+        expected
+    );
+    let observe = format!(r#"{{"object":{{"interfaces":[{raw_reference}],"name":"item"}}}}"#);
+    assert!(
+        matches!(decode_observe_response(&observe_request(), &raw_response(StatusCode::OK, observe.as_bytes()), limits()).unwrap(), DecodedResponse::Success(value) if value.object.interfaces == vec![expected])
+    );
+}
+
+#[test]
+fn reference_comparison_is_exact_without_normalization_case_or_url_decoding() {
+    for different in [
+        reference("/", "e\u{301}"),
+        reference("/", "É"),
+        reference("/", "%C3%A9"),
+        reference("/other", "é"),
+    ] {
+        let request = FetchInterfaceRequest {
+            interface: reference("/", "é"),
+        };
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &response(
+                StatusCode::OK,
+                fetch_json(json!({"scope": different.scope, "name": different.name})),
+            ),
+            limits(),
+        ));
+    }
+    let request = FetchInterfaceRequest {
+        interface: reference("/%2E", "é"),
+    };
+    let encoded = encode_fetch_interface_request(&endpoint(), &request, limits()).unwrap();
+    assert_eq!(
+        decode_fetch_interface_request(encoded.body(), limits()).unwrap(),
+        request
+    );
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "."),
+    };
+    assert!(encode_fetch_interface_request(&endpoint(), &request, limits()).is_ok());
+}
+
+#[test]
+fn request_encoding_rejects_invalid_reference_shape_without_needing_a_fetch_target() {
+    for bad in [
+        reference("relative", "x"),
+        reference("", "x"),
+        reference("/a/../b", "x"),
+        reference("/", ""),
+    ] {
+        assert!(
+            encode_fetch_interface_request(
+                &endpoint(),
+                &FetchInterfaceRequest {
+                    interface: bad.clone()
+                },
+                limits()
+            )
+            .is_err()
+        );
+        assert!(
+            encode_call_operation_request(&endpoint(), &call(bad, None), &descriptor(), limits())
+                .is_err()
+        );
+    }
+    let request = FetchInterfaceRequest {
+        interface: reference("/unrelated/scope", "x"),
+    };
+    let encoded = encode_fetch_interface_request(&endpoint(), &request, limits()).unwrap();
+    assert_eq!(
+        decode_fetch_interface_request(encoded.body(), limits()).unwrap(),
+        request
+    );
+}
+
+#[test]
+fn call_metadata_leaves_valid_out_of_scope_references_and_identity_to_host_resolution() {
+    let request = call(
+        reference("/elsewhere", "x"),
+        Some("not-current-identity".into()),
+    );
+    let encoded =
+        encode_call_operation_request(&endpoint(), &request, &descriptor(), limits()).unwrap();
+    let metadata = decode_call_operation_metadata(encoded.body(), limits()).unwrap();
+    assert_eq!(metadata.interface, request.interface);
+    assert_eq!(
+        metadata
+            .decode_request(encoded.body(), &descriptor(), limits())
+            .unwrap(),
+        request
+    );
+
+    // Neither an unknown operation nor descriptor-bound argument values are
+    // resolved by the metadata boundary before Host precondition checks.
+    let mut body: Json = serde_json::from_slice(encoded.body()).unwrap();
+    body["operation"] = json!("missing");
+    body["arguments"] = json!({"not_declared": [null, {"anything": true}]});
+    let metadata =
+        decode_call_operation_metadata(&serde_json::to_vec(&body).unwrap(), limits()).unwrap();
+    assert_eq!(metadata.operation, "missing");
+    assert_eq!(metadata.interface, request.interface);
+}
+
+#[test]
+fn observation_scope_validation_uses_each_nodes_path_and_structural_duplicates() {
+    let request = ObserveRequest {
+        path: "/a".into(),
+        depth: 1,
+    };
+    let valid = json!({
+        "object": {"name": "a", "interfaces": [{"scope": "/", "name": "x"}, {"scope": "/a", "name": "x"}]},
+        "children": [{"object": {"name": "b", "interfaces": [{"scope": "/a/b", "name": "x"}]}}]
+    });
+    assert!(
+        decode_observe_response(&request, &response(StatusCode::OK, valid.clone()), limits())
+            .is_ok()
+    );
+    for scope in ["/ab", "/elsewhere", "/a/b/c"] {
+        let mut bad = valid.clone();
+        bad["children"][0]["object"]["interfaces"][0]["scope"] = json!(scope);
+        invalid_success(decode_observe_response(
+            &request,
+            &response(StatusCode::OK, bad),
+            limits(),
+        ));
+    }
+    let mut duplicate = valid;
+    duplicate["object"]["interfaces"] =
+        json!([{"scope": "/a", "name": "x"}, {"name": "x", "scope": "/a"}]);
+    invalid_success(decode_observe_response(
+        &request,
+        &response(StatusCode::OK, duplicate),
+        limits(),
+    ));
+    let root_request = ObserveRequest {
+        path: "/".into(),
+        depth: 0,
+    };
+    for (scope, valid) in [("/", true), ("/a", false)] {
+        let result = decode_observe_response(
+            &root_request,
+            &response(
+                StatusCode::OK,
+                json!({"object": {"name": "", "interfaces": [{"scope": scope, "name": "x"}]}}),
+            ),
+            limits(),
+        );
+        if valid {
+            assert!(result.is_ok());
+        } else {
+            invalid_success(result);
+        }
+    }
+}
+
+#[test]
+fn scope_ref_omission_and_opaque_strings_round_trip_in_both_positions() {
+    for scope_ref in [
+        None,
+        Some(String::new()),
+        Some("opaque::# 世界 ! not base64 /+=".into()),
+        Some("\"\\\n\u{0}".into()),
+    ] {
+        let request = FetchInterfaceRequest {
+            interface: reference("/", "x"),
+        };
+        let expected = FetchInterfaceResponse {
+            interface: request.interface.clone(),
+            scope_ref: scope_ref.clone(),
+            descriptor: descriptor(),
+            validator: None,
+        };
+        let encoded = encode_fetch_interface_response(&request, &expected, limits()).unwrap();
+        let body: Json = serde_json::from_slice(encoded.body()).unwrap();
+        assert_eq!(
+            body.get("scope_ref"),
+            scope_ref
+                .as_ref()
+                .map(|value| Json::String(value.clone()))
+                .as_ref()
+        );
+        assert!(body.get("validator").is_none());
+        assert_eq!(
+            decode_fetch_interface_response(&request, &encoded, limits()).unwrap(),
+            DecodedResponse::Success(expected)
+        );
+        let call = call(request.interface, scope_ref);
+        let encoded =
+            encode_call_operation_request(&endpoint(), &call, &descriptor(), limits()).unwrap();
+        let body: Json = serde_json::from_slice(encoded.body()).unwrap();
+        assert_eq!(
+            body["interface"].get("scope_ref"),
+            call.interface
+                .scope_ref
+                .as_ref()
+                .map(|value| Json::String(value.clone()))
+                .as_ref()
+        );
+        assert_eq!(
+            decode_call_operation_metadata(encoded.body(), limits())
+                .unwrap()
+                .interface,
+            call.interface
+        );
+        assert_eq!(
+            decode_call_operation_request(encoded.body(), &descriptor(), limits()).unwrap(),
+            call
+        );
+    }
+}
+
+#[test]
+fn scope_ref_null_and_every_nonstring_type_are_rejected_before_descriptor_resolution() {
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "x"),
+    };
+    for bad in [Json::Null, json!(true), json!(0), json!([]), json!({})] {
+        let mut fetch = fetch_json(json!({"scope": "/", "name": "x"}));
+        fetch["scope_ref"] = bad.clone();
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &response(StatusCode::OK, fetch.clone()),
+            limits(),
+        ));
+        // Unknown format does not mask malformed common response fields.
+        fetch["descriptor"] = json!({"format": "future-format", "future": true});
+        invalid_success(decode_fetch_interface_response(
+            &request,
+            &response(StatusCode::OK, fetch),
+            limits(),
+        ));
+        let mut call = call_json(json!({"scope": "/", "name": "x"}));
+        call["interface"]["scope_ref"] = bad.clone();
+        let body = serde_json::to_vec(&call).unwrap();
+        let error = decode_call_operation_metadata(&body, limits()).unwrap_err();
+        if bad.is_null() {
+            assert!(matches!(error, CodecError::NullOptionalField { .. }));
+        } else {
+            assert!(matches!(error, CodecError::InvalidField { .. }));
+        }
+        assert!(decode_call_operation_request(&body, &descriptor(), limits()).is_err());
+    }
+}
+
+#[test]
+fn scope_ref_is_only_allowed_on_fetch_responses_and_call_interface_targets() {
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "x"),
+    };
+    let reference = json!({"scope": "/", "name": "x"});
+    let fetch_request = json!({"interface": reference, "scope_ref": "identity"});
+    assert!(
+        decode_fetch_interface_request(&serde_json::to_vec(&fetch_request).unwrap(), limits())
+            .is_err()
+    );
+
+    let mut call = call_json(reference.clone());
+    call["scope_ref"] = json!("identity");
+    assert!(decode_call_operation_metadata(&serde_json::to_vec(&call).unwrap(), limits()).is_err());
+    let mut call = call_json(reference);
+    call["target"]["scope_ref"] = json!("identity");
+    assert!(decode_call_operation_metadata(&serde_json::to_vec(&call).unwrap(), limits()).is_err());
+
+    let duplicate = br#"{"interface":{"scope":"/","name":"x"},"scope_ref":"identity","scope_ref":"identity","descriptor":{"format":"wip-interface/1","types":[],"operations":[]}}"#;
+    invalid_success(decode_fetch_interface_response(
+        &request,
+        &raw_response(StatusCode::OK, duplicate),
+        limits(),
+    ));
+    let duplicate = br#"{"target":{"path":"/"},"interface":{"reference":{"scope":"/","name":"x"},"scope_ref":"identity","scope_ref":"identity"},"operation":"run#::\u64cd\u4f5c","arguments":{}}"#;
+    assert!(matches!(
+        decode_call_operation_metadata(duplicate, limits()).unwrap_err(),
+        CodecError::InvalidJson(_)
+    ));
+    assert!(matches!(
+        decode_call_operation_request(duplicate, &descriptor(), limits()).unwrap_err(),
+        CodecError::InvalidJson(_)
+    ));
+}
+
+#[test]
+fn metadata_correspondence_includes_reference_and_scope_ref_but_not_wire_order() {
+    let request = call(reference("/", "x"), Some("identity".into()));
+    let encoded =
+        encode_call_operation_request(&endpoint(), &request, &descriptor(), limits()).unwrap();
+    let metadata = decode_call_operation_metadata(encoded.body(), limits()).unwrap();
+    for (field, changed) in [
+        ("scope_ref", json!("other")),
+        ("reference", json!({"scope": "/", "name": "other"})),
+    ] {
+        let mut body: Json = serde_json::from_slice(encoded.body()).unwrap();
+        body["interface"][field] = changed;
+        assert!(
+            matches!(metadata.decode_request(&serde_json::to_vec(&body).unwrap(), &descriptor(), limits()).unwrap_err(), CodecError::InvalidField { field, .. } if field == "request")
+        );
+    }
+    let mut body: Json = serde_json::from_slice(encoded.body()).unwrap();
+    body["interface"]
+        .as_object_mut()
+        .unwrap()
+        .remove("scope_ref");
+    assert!(
+        metadata
+            .decode_request(&serde_json::to_vec(&body).unwrap(), &descriptor(), limits())
+            .is_err()
+    );
+}
+
+#[test]
+fn fetch_classification_preserves_transport_status_and_error_envelope_semantics() {
+    let request = FetchInterfaceRequest {
+        interface: reference("/", "x"),
+    };
+    let valid = fetch_json(json!({"scope": "/", "name": "x"}));
+    for (status, kind) in [
+        (
+            StatusCode::CREATED,
+            InvalidResponseKind::NonCanonicalSuccessStatus,
+        ),
+        (
+            StatusCode::BAD_GATEWAY,
+            InvalidResponseKind::SuccessBodyOnErrorStatus,
+        ),
+    ] {
+        assert!(
+            matches!(decode_fetch_interface_response(&request, &response(status, valid.clone()), limits()).unwrap_err(), ClientResponseError::InvalidResponse { kind: actual, .. } if actual == kind)
+        );
+    }
+    for status in [
+        StatusCode::UNAUTHORIZED,
+        StatusCode::FORBIDDEN,
+        StatusCode::BAD_GATEWAY,
+    ] {
+        let malformed = response(status, fetch_json(json!("legacy")));
+        assert!(
+            matches!(decode_fetch_interface_response(&request, &malformed, limits()).unwrap_err(), ClientResponseError::TransportBinding(failure) if failure.status == status)
+        );
+    }
+    let error = ProtocolError {
+        code: ProtocolErrorCode::InterfaceNotFound,
+        message: "unpublished".into(),
+    };
+    let mut encoded =
+        encode_protocol_error_response(ProtocolInteraction::FetchInterface, &error, limits())
+            .unwrap();
+    assert_eq!(
+        decode_fetch_interface_response(&request, &encoded, limits()).unwrap(),
+        DecodedResponse::ProtocolFailure {
+            error: error.clone(),
+            status_mismatch: None
+        }
+    );
+    *encoded.status_mut() = StatusCode::BAD_GATEWAY;
+    assert!(
+        matches!(decode_fetch_interface_response(&request, &encoded, limits()).unwrap(), DecodedResponse::ProtocolFailure { error: actual, status_mismatch: Some(_) } if actual == error)
+    );
+    *encoded.status_mut() = StatusCode::OK;
+    assert!(matches!(
+        decode_fetch_interface_response(&request, &encoded, limits()).unwrap_err(),
+        ClientResponseError::InvalidResponse {
+            kind: InvalidResponseKind::ErrorEnvelopeOnSuccessStatus,
+            ..
+        }
+    ));
+    let disallowed = response(
+        StatusCode::CONFLICT,
+        json!({"error": {"code": "interface_mismatch", "message": "wrong interaction"}}),
+    );
+    assert!(matches!(
+        decode_fetch_interface_response(&request, &disallowed, limits()).unwrap_err(),
+        ClientResponseError::InvalidResponse {
+            kind: InvalidResponseKind::DisallowedProtocolCode,
+            ..
+        }
+    ));
+    let mut coded = response(StatusCode::OK, valid);
+    coded
+        .headers_mut()
+        .insert("content-encoding", "gzip".parse().unwrap());
+    assert!(
+        matches!(decode_fetch_interface_response(&request, &coded, limits()).unwrap_err(), ClientResponseError::TransportBinding(failure) if failure.kind == TransportFailureKind::UnsupportedContentCoding)
+    );
+}
+
+#[test]
+fn call_interface_mismatch_envelope_remains_protocol_failure_with_structured_metadata() {
+    let request = call(reference("/unrelated", "x"), Some("stale identity".into()));
+    let error = ProtocolError {
+        code: ProtocolErrorCode::InterfaceMismatch,
+        message: "interface precondition".into(),
+    };
+    let encoded =
+        encode_protocol_error_response(ProtocolInteraction::CallOperation, &error, limits())
+            .unwrap();
+    assert_eq!(
+        decode_call_operation_response(&request, &descriptor(), &encoded, limits()).unwrap(),
+        DecodedResponse::ProtocolFailure {
+            error,
+            status_mismatch: None
+        }
+    );
+}

crates/wip-protocol/README.md

@@ -9,6 +9,15 @@ This crate defines the canonical Object and Interface Descriptor models, the thr
 wip-protocol = "0.1.0"
 ```
 
+Interface identity is an exact `InterfaceReference { scope, name }` pair.
+`scope` is a canonical absolute Worldspace path and `name` is nonempty Unicode.
+Use `validate()` for shape, `validate_for_path()` for ancestor-or-self placement,
+and Object/interaction validation at response boundaries. Fetching needs no
+target Object path. Fetch responses and interface call targets carry optional
+opaque string `scope_ref` metadata, not a third identity field. Descriptors do
+not embed identity. See the repository's [migration guide](../../MIGRATION.md)
+for the breaking Rust and HTTP wire changes and deferred consumer semantics.
+
 See the [API documentation](https://docs.rs/wip-protocol) for the complete model and validation rules.
 
 Licensed under either of Apache-2.0 or MIT at your option.

crates/wip-protocol/src/error.rs

@@ -143,8 +143,17 @@ pub enum ValidationErrorKind {
     },
     /// An object's ordered interface set contains a duplicate.
     DuplicateInterface {
-        /// Duplicate opaque interface reference.
-        reference: String,
+        /// Duplicate structured interface reference.
+        reference: crate::InterfaceReference,
+    },
+    /// The local interface name is empty.
+    EmptyInterfaceName,
+    /// A valid scope is not an ancestor-or-self of the target path.
+    InterfaceScopeMismatch {
+        /// Selected scope path.
+        scope: String,
+        /// Target Object path.
+        path: String,
     },
     /// A string is not a canonical absolute Worldspace path.
     InvalidPath {
@@ -175,10 +184,10 @@ pub enum ValidationErrorKind {
     },
     /// A response refers to a different interface than its request.
     InterfaceResponseMismatch {
-        /// Requested opaque reference.
-        expected: String,
-        /// Returned opaque reference.
-        actual: String,
+        /// Requested structured reference (boxed to keep validation errors small).
+        expected: Box<crate::InterfaceReference>,
+        /// Returned structured reference (boxed to keep validation errors small).
+        actual: Box<crate::InterfaceReference>,
     },
 }
 
@@ -226,7 +235,7 @@ impl Error for ValidationError {}
 pub enum ProtocolInteraction {
     /// Observe one object and its indexable descendants to a requested depth.
     Observe,
-    /// Fetch one interface descriptor by its opaque reference.
+    /// Fetch one interface descriptor by its structured reference.
     FetchInterface,
     /// Invoke one operation on a path-targeted object.
     CallOperation,

crates/wip-protocol/src/lib.rs

@@ -31,7 +31,7 @@
 //! guarantee; Clients must not automatically retry it.
 //!
 //! Paths, object refs, interface refs, and validators remain separate concepts.
-//! They are represented by ordinary protocol strings/bytes in the corresponding
+//! Interface refs use [`InterfaceReference`]; other metadata use strings/bytes in their
 //! fields. In particular, object refs are optional, operation targeting uses a
 //! path, and this crate defines no interaction that fetches an object by ref.
 //!
@@ -52,9 +52,10 @@ pub use error::{
 };
 pub use model::{
     CallOperationRequest, CallOperationResponse, Documentation, EnumCase, FetchInterfaceRequest,
-    FetchInterfaceResponse, FieldDeclaration, InterfaceDescriptor, InterfaceTarget, Object,
-    ObjectObservation, ObserveRequest, ObserveResponse, OperationDeclaration, ParameterDeclaration,
-    ProtocolResult, ReturnDeclaration, Target, TypeDeclaration, TypeExpr, UnionCase, Value,
+    FetchInterfaceResponse, FieldDeclaration, InterfaceDescriptor, InterfaceReference,
+    InterfaceTarget, Object, ObjectObservation, ObserveRequest, ObserveResponse,
+    OperationDeclaration, ParameterDeclaration, ProtocolResult, ReturnDeclaration, Target,
+    TypeDeclaration, TypeExpr, UnionCase, Value,
 };
 
 /// Validates a canonical absolute Worldspace path.

crates/wip-protocol/src/model.rs

@@ -11,9 +11,49 @@ pub struct Documentation {
     pub details: Option<String>,
 }
 
+/// An interface identified by an exact `(scope, name)` pair in one Worldspace.
+///
+/// Neither field is normalized, case-folded, URL-decoded, or split on display
+/// delimiters. Descriptor identity is external to the descriptor itself.
+///
+/// ```
+/// use wip_protocol::{FetchInterfaceRequest, InterfaceReference};
+/// let reference = InterfaceReference {
+///     scope: "/世::界/#".into(),
+///     name: "read::書く#λ".into(),
+/// };
+/// reference.validate_for_path("/世::界/#/item")?;
+/// // Fetching is independent of an Object target path.
+/// FetchInterfaceRequest { interface: reference }.validate()?;
+/// # Ok::<(), wip_protocol::ValidationError>(())
+/// ```
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct InterfaceReference {
+    /// Canonical absolute Worldspace path of the interface's scope Object.
+    pub scope: String,
+    /// Nonempty Unicode local name, with no delimiter restrictions.
+    pub name: String,
+}
+
+impl InterfaceReference {
+    /// Validates reference shape without requiring a target Object path.
+    pub fn validate(&self) -> Result<(), ValidationError> {
+        crate::validation::validate_interface_reference(self)
+    }
+
+    /// Validates shape and that scope is an ancestor-or-self of `path`.
+    ///
+    /// This is independent of indexability. A Host maps a valid reference's
+    /// scope mismatch to `InterfaceMismatch` at the interface-selection stage,
+    /// not to the earlier shape-validation `InvalidRequest` stage.
+    pub fn validate_for_path(&self, path: &str) -> Result<(), ValidationError> {
+        crate::validation::validate_interface_scope(self, path)
+    }
+}
+
 /// The protocol projection currently published at one Worldspace path.
 ///
-/// `name` is a path segment, `interfaces` is an ordered set of opaque interface
+/// `name` is a path segment, `interfaces` is an ordered set of structured interface
 /// references, `r#ref` is optional object identity, and `validator` is an
 /// independent optional observation precondition. In particular, neither the
 /// path nor `r#ref` is a mandatory object identifier.
@@ -23,8 +63,8 @@ pub struct Object {
     pub name: String,
     /// Short public description of the object.
     pub description: Option<String>,
-    /// Opaque interface references in host publication order.
-    pub interfaces: Vec<String>,
+    /// Structured interface references in host publication order.
+    pub interfaces: Vec<InterfaceReference>,
     /// Optional opaque identity within one client-facing Worldspace.
     pub r#ref: Option<String>,
     /// Optional opaque validator for the object's observed state.
@@ -239,18 +279,20 @@ pub struct ObjectObservation {
 /// Successful `observe` response.
 pub type ObserveResponse = ObjectObservation;
 
-/// Request for the current descriptor of one opaque interface reference.
+/// Request for the current descriptor of one structured interface reference.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FetchInterfaceRequest {
-    /// Opaque interface reference obtained from an object.
-    pub interface: String,
+    /// Structured interface reference obtained from an object.
+    pub interface: InterfaceReference,
 }
 
 /// Successful `fetch_interface` response.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FetchInterfaceResponse {
-    /// Opaque interface reference corresponding to the request.
-    pub interface: String,
+    /// Structured interface reference corresponding to the request.
+    pub interface: InterfaceReference,
+    /// Optional opaque ref of the scope Object, not part of interface identity.
+    pub scope_ref: Option<String>,
     /// Current validated descriptor.
     pub descriptor: InterfaceDescriptor,
     /// Optional opaque validator for this descriptor observation.
@@ -269,8 +311,10 @@ pub struct Target {
 /// Interface portion of an operation target.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InterfaceTarget {
-    /// Opaque interface reference selected from the object's interface set.
-    pub reference: String,
+    /// Structured reference selected from the object's interface set.
+    pub reference: InterfaceReference,
+    /// Optional scope Object ref copied from the same interface observation.
+    pub scope_ref: Option<String>,
     /// Optional validator copied from the interface observation.
     pub validator: Option<Vec<u8>>,
 }
@@ -369,6 +413,13 @@ impl ObserveRequest {
     }
 }
 
+impl FetchInterfaceRequest {
+    /// Validates reference shape; fetching an interface needs no target path.
+    pub fn validate(&self) -> Result<(), ValidationError> {
+        self.interface.validate()
+    }
+}
+
 impl FetchInterfaceResponse {
     /// Validates request correspondence and descriptor semantics.
     ///
@@ -382,7 +433,16 @@ impl FetchInterfaceResponse {
 }
 
 impl CallOperationRequest {
-    /// Validates this call against the descriptor selected by `interface`.
+    /// Validates descriptor-independent request shape only.
+    ///
+    /// Scope compatibility is deliberately deferred to interface selection so
+    /// that `NotFound` precedes `InterfaceMismatch` at the Host boundary.
+    pub fn validate(&self) -> Result<(), ValidationError> {
+        crate::validation::validate_call_shape(self)
+    }
+
+    /// Validates this call's shape and descriptor-bound operation/arguments.
+    /// Scope compatibility and membership require Host publication context.
     pub fn validate_with(&self, descriptor: &InterfaceDescriptor) -> Result<(), ValidationError> {
         descriptor.validate_call(self)
     }

crates/wip-protocol/src/validation.rs

@@ -2,17 +2,22 @@ use std::collections::{BTreeMap, HashMap, HashSet};
 
 use crate::{
     CallOperationRequest, FetchInterfaceRequest, FetchInterfaceResponse, InterfaceDescriptor,
-    MAX_SAFE_INTEGER, MIN_SAFE_INTEGER, NameNamespace, Object, ObjectObservation, ObserveRequest,
-    PathSegment, TypeDeclaration, TypeExpr, UNION_CASE_FIELD, UNION_VALUE_FIELD, ValidationError,
-    ValidationErrorKind, Value, ValueKind,
+    InterfaceReference, MAX_SAFE_INTEGER, MIN_SAFE_INTEGER, NameNamespace, Object,
+    ObjectObservation, ObserveRequest, PathSegment, TypeDeclaration, TypeExpr, UNION_CASE_FIELD,
+    UNION_VALUE_FIELD, ValidationError, ValidationErrorKind, Value, ValueKind,
 };
 
 pub(crate) fn validate_object(object: &Object) -> Result<(), ValidationError> {
     validate_object_name(&object.name, true)?;
 
     let mut seen = HashSet::new();
-    for interface in &object.interfaces {
-        if !seen.insert(interface.as_str()) {
+    for (index, interface) in object.interfaces.iter().enumerate() {
+        interface.validate().map_err(|error| {
+            error
+                .prepend(PathSegment::Index(index))
+                .prepend(PathSegment::Field("interfaces".into()))
+        })?;
+        if !seen.insert(interface) {
             return Err(
                 ValidationError::new(ValidationErrorKind::DuplicateInterface {
                     reference: interface.clone(),
@@ -51,6 +56,14 @@ pub(crate) fn validate_object_at_path(object: &Object, path: &str) -> Result<(),
             .next()
             .expect("non-root path has a segment")
     };
+    for (index, interface) in object.interfaces.iter().enumerate() {
+        interface.validate_for_path(path).map_err(|error| {
+            error
+                .prepend(PathSegment::Index(index))
+                .prepend(PathSegment::Field("interfaces".into()))
+                .prepend(PathSegment::Object(path.to_owned()))
+        })?;
+    }
     if object.name == expected {
         Ok(())
     } else {
@@ -106,6 +119,54 @@ pub(crate) fn validate_path(path: &str) -> Result<(), ValidationError> {
     }
 }
 
+pub(crate) fn validate_interface_reference(
+    reference: &InterfaceReference,
+) -> Result<(), ValidationError> {
+    validate_path(&reference.scope)
+        .map_err(|error| error.prepend(PathSegment::Field("scope".into())))?;
+    if reference.name.is_empty() {
+        return Err(
+            ValidationError::new(ValidationErrorKind::EmptyInterfaceName)
+                .prepend(PathSegment::Field("name".into())),
+        );
+    }
+    Ok(())
+}
+
+pub(crate) fn validate_interface_scope(
+    reference: &InterfaceReference,
+    path: &str,
+) -> Result<(), ValidationError> {
+    reference.validate()?;
+    validate_path(path)?;
+    let scope = reference.scope.as_str();
+    if scope == "/"
+        || path == scope
+        || path
+            .strip_prefix(scope)
+            .is_some_and(|rest| rest.starts_with('/'))
+    {
+        Ok(())
+    } else {
+        Err(ValidationError::new(
+            ValidationErrorKind::InterfaceScopeMismatch {
+                scope: reference.scope.clone(),
+                path: path.to_owned(),
+            },
+        ))
+    }
+}
+
+pub(crate) fn validate_call_shape(request: &CallOperationRequest) -> Result<(), ValidationError> {
+    validate_path(&request.target.path)
+        .map_err(|error| error.prepend(PathSegment::Field("target".into())))?;
+    request.interface.reference.validate().map_err(|error| {
+        error
+            .prepend(PathSegment::Field("reference".into()))
+            .prepend(PathSegment::Field("interface".into()))
+    })
+}
+
 pub(crate) fn validate_descriptor(descriptor: &InterfaceDescriptor) -> Result<(), ValidationError> {
     let declarations = declaration_map(descriptor)?;
 
@@ -582,8 +643,7 @@ pub(crate) fn validate_call(
     descriptor: &InterfaceDescriptor,
     request: &CallOperationRequest,
 ) -> Result<(), ValidationError> {
-    validate_path(&request.target.path)
-        .map_err(|error| error.prepend(PathSegment::Field("target".into())))?;
+    request.validate()?;
     validate_arguments(descriptor, &request.operation, &request.arguments)
 }
 
@@ -660,11 +720,13 @@ pub(crate) fn validate_fetch_interface_response(
     response: &FetchInterfaceResponse,
     request: &FetchInterfaceRequest,
 ) -> Result<(), ValidationError> {
+    request.validate()?;
+    response.interface.validate()?;
     if response.interface != request.interface {
         return Err(
             ValidationError::new(ValidationErrorKind::InterfaceResponseMismatch {
-                expected: request.interface.clone(),
-                actual: response.interface.clone(),
+                expected: Box::new(request.interface.clone()),
+                actual: Box::new(response.interface.clone()),
             })
             .prepend(PathSegment::Field("interface".into())),
         );

crates/wip-protocol/tests/interface_references.rs

@@ -0,0 +1,219 @@
+use std::collections::BTreeMap;
+use wip_protocol::{
+    CallOperationRequest, FetchInterfaceRequest, FetchInterfaceResponse, InterfaceDescriptor,
+    InterfaceReference, InterfaceTarget, Object, ObjectObservation, ObserveRequest,
+    OperationDeclaration, ReturnDeclaration, Target, TypeExpr, ValidationErrorKind,
+};
+
+fn reference(scope: &str, name: &str) -> InterfaceReference {
+    InterfaceReference {
+        scope: scope.into(),
+        name: name.into(),
+    }
+}
+
+fn object(path: &str, interfaces: Vec<InterfaceReference>) -> Object {
+    Object {
+        name: path.rsplit('/').next().unwrap().into(),
+        description: None,
+        interfaces,
+        r#ref: None,
+        validator: None,
+    }
+}
+
+fn descriptor() -> InterfaceDescriptor {
+    InterfaceDescriptor {
+        format: wip_protocol::INTERFACE_FORMAT_V1.into(),
+        documentation: None,
+        types: vec![],
+        operations: vec![OperationDeclaration {
+            name: "run".into(),
+            documentation: None,
+            parameters: vec![],
+            returns: ReturnDeclaration {
+                documentation: None,
+                r#type: TypeExpr::Unit,
+            },
+        }],
+    }
+}
+
+#[test]
+fn scope_is_segment_based_ancestor_or_self_not_indexability() {
+    for (scope, path) in [
+        ("/", "/"),
+        ("/", "/a/b"),
+        ("/a", "/a"),
+        ("/a", "/a/b"),
+        ("/a/b", "/a/b/c"),
+    ] {
+        reference(scope, "read").validate_for_path(path).unwrap();
+        object(path, vec![reference(scope, "read")])
+            .validate_at_path(path)
+            .unwrap();
+    }
+    for (scope, path) in [
+        ("/a", "/ab"),
+        ("/a", "/ab/c"),
+        ("/a/b", "/a/c"),
+        ("/a/b", "/a"),
+        ("/a", "/"),
+    ] {
+        assert!(matches!(
+            reference(scope, "read")
+                .validate_for_path(path)
+                .unwrap_err()
+                .kind,
+            ValidationErrorKind::InterfaceScopeMismatch { .. }
+        ));
+        // Without the placement context, the Object/reference shape is valid.
+        let object = object(path, vec![reference(scope, "read")]);
+        object.validate().unwrap();
+        assert!(matches!(
+            object.validate_at_path(path).unwrap_err().kind,
+            ValidationErrorKind::InterfaceScopeMismatch { .. }
+        ));
+    }
+}
+
+#[test]
+fn shape_validation_does_not_normalize_or_parse_fields() {
+    for scope in ["", "relative", "//a", "/a/", "/a//b", "/a/./b", "/a/../b"] {
+        let reference = reference(scope, "read");
+        assert!(matches!(
+            reference.validate().unwrap_err().kind,
+            ValidationErrorKind::InvalidPath { .. }
+        ));
+        assert!(
+            FetchInterfaceRequest {
+                interface: reference.clone()
+            }
+            .validate()
+            .is_err()
+        );
+        assert!(object("/a", vec![reference]).validate().is_err());
+    }
+    assert_eq!(
+        reference("/", "").validate().unwrap_err().kind,
+        ValidationErrorKind::EmptyInterfaceName
+    );
+    for name in [".", "..", "a/b", "::", "#", "読み::書き#λ", "e\u{301}"] {
+        let reference = reference("/世::界/#/%2F", name);
+        reference.validate().unwrap();
+        assert_eq!(reference.name, name);
+        assert_eq!(reference.scope, "/世::界/#/%2F");
+    }
+    assert_ne!(reference("/", "é"), reference("/", "e\u{301}"));
+    assert_ne!(reference("/A", "read"), reference("/a", "read"));
+    assert_ne!(reference("/%61", "read"), reference("/a", "read"));
+}
+
+#[test]
+fn duplicate_membership_and_correlation_use_complete_pair() {
+    let root = reference("/", "read");
+    let scoped = reference("/a", "read");
+    let mut object = object("/a", vec![root.clone(), scoped.clone()]);
+    object.validate_at_path("/a").unwrap();
+    assert!(object.interfaces.contains(&scoped));
+    assert!(!object.interfaces.contains(&reference("/b", "read")));
+    object.interfaces.push(root.clone());
+    assert_eq!(
+        object.validate().unwrap_err().kind,
+        ValidationErrorKind::DuplicateInterface {
+            reference: root.clone()
+        }
+    );
+    let request = FetchInterfaceRequest { interface: root };
+    let mut response = FetchInterfaceResponse {
+        interface: scoped,
+        scope_ref: None,
+        descriptor: descriptor(),
+        validator: None,
+    };
+    assert!(matches!(
+        response.validate_for(&request).unwrap_err().kind,
+        ValidationErrorKind::InterfaceResponseMismatch { .. }
+    ));
+    response.interface = request.interface.clone();
+    for scope_ref in [None, Some(String::new()), Some("opaque::世界#/%".into())] {
+        response.scope_ref = scope_ref;
+        response.validate_for(&request).unwrap();
+    }
+    response.interface.name.clear();
+    assert_eq!(
+        response.validate_for(&request).unwrap_err().kind,
+        ValidationErrorKind::EmptyInterfaceName
+    );
+}
+
+#[test]
+fn observe_checks_scope_at_every_node_including_depth_boundary() {
+    let request = ObserveRequest {
+        path: "/a".into(),
+        depth: 1,
+    };
+    let mut response = ObjectObservation {
+        object: object("/a", vec![reference("/a", "read")]),
+        children: Some(vec![ObjectObservation {
+            object: object("/a/b", vec![reference("/a/b", "read")]),
+            children: None,
+        }]),
+    };
+    request.validate_response(&response).unwrap();
+    response.children.as_mut().unwrap()[0].object.interfaces[0].scope = "/a/c".into();
+    assert!(matches!(
+        request.validate_response(&response).unwrap_err().kind,
+        ValidationErrorKind::InterfaceScopeMismatch { .. }
+    ));
+}
+
+#[test]
+fn fetch_needs_no_target_path_and_call_separates_shape_from_scope_selection() {
+    let reference = reference("/some/unrelated/scope", "read");
+    let fetch = FetchInterfaceRequest {
+        interface: reference.clone(),
+    };
+    fetch.validate().unwrap();
+    FetchInterfaceResponse {
+        interface: reference.clone(),
+        scope_ref: None,
+        descriptor: descriptor(),
+        validator: None,
+    }
+    .validate_for(&fetch)
+    .unwrap();
+    let mut call = CallOperationRequest {
+        target: Target {
+            path: "/a".into(),
+            validator: None,
+        },
+        interface: InterfaceTarget {
+            reference,
+            scope_ref: Some("opaque".into()),
+            validator: None,
+        },
+        operation: "run".into(),
+        arguments: BTreeMap::new(),
+    };
+    call.validate().unwrap();
+    call.validate_with(&descriptor()).unwrap();
+    // This stage is Host InterfaceMismatch, after NotFound, not shape InvalidRequest.
+    assert!(matches!(
+        call.interface
+            .reference
+            .validate_for_path(&call.target.path)
+            .unwrap_err()
+            .kind,
+        ValidationErrorKind::InterfaceScopeMismatch { .. }
+    ));
+    call.interface.reference.name.clear();
+    assert_eq!(
+        call.validate().unwrap_err().kind,
+        ValidationErrorKind::EmptyInterfaceName
+    );
+    assert_eq!(
+        call.validate_with(&descriptor()).unwrap_err().kind,
+        ValidationErrorKind::EmptyInterfaceName
+    );
+}

crates/wip-protocol/tests/validation.rs

@@ -3,12 +3,19 @@ use std::collections::BTreeMap;
 use wip_protocol::{
     CallOperationRequest, CallOperationResponse, EnumCase, FetchInterfaceRequest,
     FetchInterfaceResponse, FieldDeclaration, INTERFACE_FORMAT_V1, InterfaceDescriptor,
-    InterfaceTarget, MAX_SAFE_INTEGER, NameNamespace, Object, ObjectObservation, ObserveRequest,
-    OperationDeclaration, ParameterDeclaration, PathSegment, ProtocolError, ProtocolErrorCode,
-    ProtocolInteraction, ProtocolResult, ReturnDeclaration, Target, TypeDeclaration, TypeExpr,
-    UnionCase, ValidationErrorKind, Value, ValueKind,
+    InterfaceReference, InterfaceTarget, MAX_SAFE_INTEGER, NameNamespace, Object,
+    ObjectObservation, ObserveRequest, OperationDeclaration, ParameterDeclaration, PathSegment,
+    ProtocolError, ProtocolErrorCode, ProtocolInteraction, ProtocolResult, ReturnDeclaration,
+    Target, TypeDeclaration, TypeExpr, UnionCase, ValidationErrorKind, Value, ValueKind,
 };
 
+fn reference(scope: &str, name: &str) -> InterfaceReference {
+    InterfaceReference {
+        scope: scope.into(),
+        name: name.into(),
+    }
+}
+
 fn record(entries: impl IntoIterator<Item = (&'static str, Value)>) -> Value {
     Value::Record(
         entries
@@ -135,7 +142,7 @@ fn object(name: &str) -> Object {
     Object {
         name: name.into(),
         description: Some(format!("Object {name}")),
-        interfaces: vec!["catalog-v1".into(), "search-v2".into()],
+        interfaces: vec![reference("/", "catalog-v1"), reference("/", "search-v2")],
         r#ref: Some("opaque-object-ref".into()),
         validator: Some(vec![1, 2, 3]),
     }
@@ -146,16 +153,19 @@ fn object_fields_have_canonical_identity_and_ordered_set_semantics() {
     let object = object("article");
     object.validate().unwrap();
     object.validate_at_path("/articles/article").unwrap();
-    assert_eq!(object.interfaces, ["catalog-v1", "search-v2"]);
+    assert_eq!(
+        object.interfaces,
+        [reference("/", "catalog-v1"), reference("/", "search-v2")]
+    );
 
     let duplicate = Object {
-        interfaces: vec!["catalog-v1".into(), "catalog-v1".into()],
+        interfaces: vec![reference("/", "catalog-v1"), reference("/", "catalog-v1")],
         ..object.clone()
     };
     assert_eq!(
         duplicate.validate().unwrap_err().kind,
         ValidationErrorKind::DuplicateInterface {
-            reference: "catalog-v1".into()
+            reference: reference("/", "catalog-v1")
         }
     );
 
@@ -574,7 +584,8 @@ fn calls_validate_canonical_paths_named_arguments_and_unit_results() {
             validator: Some(vec![1]),
         },
         interface: InterfaceTarget {
-            reference: "catalog-v1".into(),
+            scope_ref: None,
+            reference: reference("/", "catalog-v1"),
             validator: Some(vec![2]),
         },
         operation: "publish".into(),
@@ -659,17 +670,18 @@ fn observe_and_fetch_interface_dtos_validate_request_response_correspondence() {
     }
 
     let request = FetchInterfaceRequest {
-        interface: "catalog-v1".into(),
+        interface: reference("/", "catalog-v1"),
     };
     let response = FetchInterfaceResponse {
-        interface: "catalog-v1".into(),
+        scope_ref: None,
+        interface: reference("/", "catalog-v1"),
         descriptor: descriptor(),
         validator: Some(vec![9]),
     };
     response.validate_for(&request).unwrap();
     assert!(matches!(
         FetchInterfaceResponse {
-            interface: "other".into(),
+            interface: reference("/", "other"),
             ..response
         }
         .validate_for(&request)
@@ -847,7 +859,7 @@ fn invalid_success_payloads_remain_client_local_validation_failures() {
     ));
 
     let interface_request = FetchInterfaceRequest {
-        interface: "catalog-v1".into(),
+        interface: reference("/", "catalog-v1"),
     };
     let mut invalid_descriptor = descriptor();
     invalid_descriptor
@@ -856,6 +868,7 @@ fn invalid_success_payloads_remain_client_local_validation_failures() {
     assert!(matches!(
         FetchInterfaceResponse {
             interface: interface_request.interface.clone(),
+            scope_ref: None,
             descriptor: invalid_descriptor,
             validator: None,
         }

crates/wip-public-api-example/src/lib.rs

@@ -16,7 +16,7 @@
 //!
 //! The canonical API targets operations by `target.path` rather than a mandatory
 //! object identifier. Object `ref` and object/interface validators are separate,
-//! optional observation fields. Interface references are opaque values observed
+//! optional observation fields. Interface references are structured scope/name values observed
 //! separately from descriptors, and descriptors contain neither a Rust trait
 //! name nor an opaque-reference `name` field. Application records, enums,
 //! unions, entry paths, and JSON all encode through the schema-neutral [`Value`]
@@ -46,7 +46,7 @@ use wip_host::{
 };
 use wip_interface as wip;
 use wip_interface::WipType;
-use wip_protocol::{ProtocolError, ProtocolErrorCode, Value};
+use wip_protocol::{InterfaceReference, ProtocolError, ProtocolErrorCode, Value};
 
 const OBJECT_PATH: &str = "/article-service";
 const OBJECT_VALIDATOR: &[u8] = b"object-v1";
@@ -134,12 +134,12 @@ pub struct DemoReport {
     pub object_reference: Option<String>,
     /// Optional object-state validator.
     pub object_validator: Option<Vec<u8>>,
-    /// Opaque interface references published by the object, in exposure order.
-    pub published_interfaces: Vec<String>,
-    /// Opaque reference assigned to the catalog descriptor.
-    pub catalog_interface_reference: String,
-    /// Opaque reference assigned to the audit descriptor.
-    pub audit_interface_reference: String,
+    /// Structured interface references published by the object, in exposure order.
+    pub published_interfaces: Vec<InterfaceReference>,
+    /// Root-scoped reference assigned to the catalog descriptor.
+    pub catalog_interface_reference: InterfaceReference,
+    /// Root-scoped reference assigned to the audit descriptor.
+    pub audit_interface_reference: InterfaceReference,
     /// Descriptor format observed separately for the catalog reference.
     pub catalog_descriptor_format: String,
     /// Descriptor format observed separately for the audit reference.
@@ -296,7 +296,8 @@ pub fn run() -> Result<DemoReport, Box<dyn Error>> {
                 validator: Some(b"stale-object".to_vec()),
             },
             interface: InterfaceTarget {
-                reference: diagnostics.reference().as_str().to_owned(),
+                scope_ref: None,
+                reference: diagnostics.reference().protocol_reference(),
                 validator: Some(b"stale-interface".to_vec()),
             },
             operation: "missing".into(),
@@ -319,7 +320,10 @@ pub fn run() -> Result<DemoReport, Box<dyn Error>> {
         .code;
 
     let interface_not_found = registry
-        .fetch_interface("missing-interface")
+        .fetch_interface(&InterfaceReference {
+            scope: "/".into(),
+            name: "missing-interface".into(),
+        })
         .expect_err("unknown interface references must not resolve")
         .code;
 
@@ -330,7 +334,8 @@ pub fn run() -> Result<DemoReport, Box<dyn Error>> {
                 validator: Some(b"stale-object".to_vec()),
             },
             interface: InterfaceTarget {
-                reference: diagnostics.reference().as_str().to_owned(),
+                scope_ref: None,
+                reference: diagnostics.reference().protocol_reference(),
                 validator: Some(b"stale-interface".to_vec()),
             },
             operation: "missing".into(),
@@ -345,8 +350,8 @@ pub fn run() -> Result<DemoReport, Box<dyn Error>> {
         object_reference: object.r#ref,
         object_validator: object.validator,
         published_interfaces: object.interfaces,
-        catalog_interface_reference: catalog.reference().as_str().to_owned(),
-        audit_interface_reference: audit.reference().as_str().to_owned(),
+        catalog_interface_reference: catalog.reference().protocol_reference(),
+        audit_interface_reference: audit.reference().protocol_reference(),
         catalog_descriptor_format: catalog_response.descriptor.format,
         audit_descriptor_format: audit_response.descriptor.format,
         published,
@@ -412,7 +417,8 @@ fn request(
             validator: Some(OBJECT_VALIDATOR.to_vec()),
         },
         interface: InterfaceTarget {
-            reference: interface.as_str().to_owned(),
+            scope_ref: None,
+            reference: interface.protocol_reference(),
             validator: interface_validator.map(<[u8]>::to_vec),
         },
         operation: operation.into(),

crates/wip-public-api-example/tests/end_to_end.rs

@@ -97,7 +97,7 @@ fn object_fields_keep_path_context_and_optional_ref_separate() {
     let object = Object {
         name: "article".into(),
         description: None,
-        interfaces: vec!["catalog-ref".into(), "audit-ref".into()],
+        interfaces: vec![root_reference("catalog-ref"), root_reference("audit-ref")],
         r#ref: None,
         validator: None,
     };
@@ -105,7 +105,10 @@ fn object_fields_keep_path_context_and_optional_ref_separate() {
     object.validate_at_path("/library/article").unwrap();
     assert_eq!(object.name, "article");
     assert_eq!(object.r#ref, None);
-    assert_eq!(object.interfaces, ["catalog-ref", "audit-ref"]);
+    assert_eq!(
+        object.interfaces,
+        [root_reference("catalog-ref"), root_reference("audit-ref")]
+    );
 }
 
 #[test]
@@ -244,3 +247,10 @@ fn assert_schema_neutral(value: &Value) {
         }
     }
 }
+
+fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+    wip_protocol::InterfaceReference {
+        scope: "/".into(),
+        name: name.into(),
+    }
+}

crates/wip-tui/README.md

@@ -96,8 +96,10 @@ a second explicit Enter (or `e`) to execute once. There is no operation auto-ret
   interfaces, and freshness. Validators, credentials, Host internals, and backend
   paths are deliberately hidden. If current metadata disappears, old text is not
   presented as current.
-- **Interfaces / Operations** identifies every operation by `(interface reference,
-  operation name)`. Descriptor lookahead follows fresh visible Objects, shares the
+- **Interfaces / Operations** identifies every operation by `(interface scope,
+  interface name, operation name)` and explicitly displays `scope=…` and `name=…`.
+  Structured references remain intact in selection, acquisition, and call state;
+  display labels are never parsed back into references. Descriptor lookahead follows fresh visible Objects, shares the
   client's in-flight/cache bounds, and never retries retained failures implicitly.
   The pane shows descriptor documentation, ordered parameters, required/optional
   status, and result types.

crates/wip-tui/src/app.rs

@@ -3,7 +3,7 @@
 use std::collections::{BTreeMap, BTreeSet};
 
 use wip_client::{InterfaceObservation, ObjectObservation, ObservationState, TreeObservation};
-use wip_protocol::{InterfaceDescriptor, Object, Value};
+use wip_protocol::{InterfaceDescriptor, InterfaceReference, Object, Value};
 
 use crate::editor::ArgumentEditor;
 
@@ -139,8 +139,8 @@ impl EntryView {
 /// Cached interface descriptor state used by presentation.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct InterfaceView {
-    /// Opaque interface reference.
-    pub reference: String,
+    /// Structured interface reference.
+    pub reference: InterfaceReference,
     /// Descriptor when accepted by the client runtime.
     pub descriptor: Option<InterfaceDescriptor>,
     /// Descriptor observation state.
@@ -187,13 +187,13 @@ pub enum InFlightKind {
     /// Tree expansion or refresh.
     Tree(String),
     /// Descriptor fetch.
-    Interface(String),
+    Interface(InterfaceReference),
     /// Explicit operation call.
     Operation {
         /// Target path.
         path: String,
         /// Interface reference.
-        interface: String,
+        interface: InterfaceReference,
         /// Operation name.
         operation: String,
         /// Whether the transport dispatch boundary was crossed.
@@ -241,13 +241,13 @@ pub enum Action {
         path: String,
     },
     /// Retrieve one interface descriptor.
-    FetchInterface(String),
+    FetchInterface(InterfaceReference),
     /// Execute only after explicit confirmation.
     Execute {
         /// Entry target.
         path: String,
         /// Interface reference.
-        interface: String,
+        interface: InterfaceReference,
         /// Operation name.
         operation: String,
         /// Descriptor-validated arguments.
@@ -276,8 +276,8 @@ pub struct App {
     pub selected_path: String,
     /// Focused pane.
     pub focus: Focus,
-    /// Interface descriptor views by opaque reference.
-    pub interfaces: BTreeMap<String, InterfaceView>,
+    /// Interface descriptor views by structured reference.
+    pub interfaces: BTreeMap<InterfaceReference, InterfaceView>,
     /// Selected row in the flattened interface/operation view.
     pub operation_cursor: usize,
     /// Selected recent-history row.
@@ -615,7 +615,7 @@ impl App {
     /// Returns interface references advertised by fresh visible Objects in display
     /// and per-Object declaration order, with duplicates removed.
     #[must_use]
-    pub fn visible_interface_references(&self) -> Vec<String> {
+    pub fn visible_interface_references(&self) -> Vec<InterfaceReference> {
         let mut references = Vec::new();
         let mut seen = BTreeSet::new();
         for path in self.visible_paths() {
@@ -716,7 +716,7 @@ impl App {
             .or_insert_with(|| EntryView::placeholder(path))
     }
 
-    fn ensure_interface(&mut self, reference: &str) -> &mut InterfaceView {
+    fn ensure_interface(&mut self, reference: &InterfaceReference) -> &mut InterfaceView {
         if !self.interfaces.contains_key(reference)
             && self.interfaces.len() >= MAX_PRESENTATION_INTERFACES
         {
@@ -757,7 +757,7 @@ impl App {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct OperationRow {
     /// Interface reference, which participates in operation identity.
-    pub interface: String,
+    pub interface: InterfaceReference,
     /// Operation name, or `None` for the interface heading.
     pub operation: Option<String>,
 }
@@ -773,6 +773,12 @@ pub fn parent_path(path: &str) -> String {
 
 #[cfg(test)]
 mod tests {
+    fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+        wip_protocol::InterfaceReference {
+            scope: "/".into(),
+            name: name.into(),
+        }
+    }
     use super::*;
     use wip_protocol::{INTERFACE_FORMAT_V1, OperationDeclaration, ReturnDeclaration, TypeExpr};
 
@@ -780,7 +786,10 @@ mod tests {
         Object {
             name: name.into(),
             description: Some(format!("{name} description")),
-            interfaces: interfaces.iter().map(|value| (*value).into()).collect(),
+            interfaces: interfaces
+                .iter()
+                .map(|value| root_reference(value))
+                .collect(),
             r#ref: None,
             validator: None,
         }
@@ -846,7 +855,51 @@ mod tests {
 
         assert_eq!(
             app.visible_interface_references(),
-            ["root", "shared", "child"]
+            [
+                root_reference("root"),
+                root_reference("shared"),
+                root_reference("child")
+            ]
+        );
+    }
+
+    #[test]
+    fn presentation_retains_equal_names_in_distinct_scopes() {
+        let mut app = App::new("https://example.test/wip");
+        let root = root_reference("shared#::操作");
+        let local = InterfaceReference {
+            scope: "/a".into(),
+            name: root.name.clone(),
+        };
+        let mut value = object("a", &[]);
+        value.interfaces = vec![root.clone(), local.clone()];
+        app.navigate_entry("/a");
+        app.apply_object(ObjectObservation {
+            path: "/a".into(),
+            object: Some(value),
+            validator: None,
+            state: ObservationState::Fresh,
+        });
+        for reference in [&root, &local] {
+            app.apply_interface(InterfaceObservation {
+                reference: reference.clone(),
+                descriptor: None,
+                validator: None,
+                scope_ref: None,
+                state: ObservationState::Fresh,
+            });
+        }
+        assert_eq!(app.interfaces.len(), 2);
+        assert_eq!(
+            app.visible_interface_references(),
+            vec![root.clone(), local.clone()]
+        );
+        assert_eq!(
+            app.operation_rows()
+                .iter()
+                .map(|row| row.interface.clone())
+                .collect::<Vec<_>>(),
+            vec![root, local]
         );
     }
 
@@ -874,7 +927,8 @@ mod tests {
             }],
         };
         app.apply_interface(InterfaceObservation {
-            reference: "iface".into(),
+            scope_ref: None,
+            reference: root_reference("iface"),
             descriptor: Some(descriptor),
             validator: None,
             state: ObservationState::Fresh,
@@ -903,7 +957,8 @@ mod tests {
 
         for index in 0..(MAX_PRESENTATION_INTERFACES + 50) {
             app.apply_interface(InterfaceObservation {
-                reference: format!("interface-{index}"),
+                scope_ref: None,
+                reference: root_reference(&format!("interface-{index}")),
                 descriptor: None,
                 validator: None,
                 state: ObservationState::Fresh,

crates/wip-tui/src/editor.rs

@@ -4,7 +4,9 @@ use std::collections::BTreeMap;
 
 use base64::Engine as _;
 use base64::engine::general_purpose::STANDARD;
-use wip_protocol::{InterfaceDescriptor, OperationDeclaration, TypeExpr, Value};
+use wip_protocol::{
+    InterfaceDescriptor, InterfaceReference, OperationDeclaration, TypeExpr, Value,
+};
 
 const MAX_FIELD_INPUT_BYTES: usize = 256 * 1024;
 
@@ -30,8 +32,8 @@ pub struct InvalidArguments;
 /// Pure, terminal-independent editor built from an operation descriptor.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ArgumentEditor {
-    /// Opaque interface reference selected for the call.
-    pub interface: String,
+    /// Structured interface reference selected for the call.
+    pub interface: InterfaceReference,
     /// Selected operation declaration.
     pub operation: OperationDeclaration,
     /// Complete descriptor used to resolve named types.
@@ -46,7 +48,7 @@ impl ArgumentEditor {
     /// Builds an editor whose fields preserve descriptor order.
     #[must_use]
     pub fn new(
-        interface: impl Into<String>,
+        interface: InterfaceReference,
         descriptor: InterfaceDescriptor,
         operation: OperationDeclaration,
     ) -> Self {
@@ -66,7 +68,7 @@ impl ArgumentEditor {
             })
             .collect();
         Self {
-            interface: interface.into(),
+            interface,
             operation,
             descriptor,
             fields,
@@ -466,6 +468,12 @@ fn json_to_untyped(json: &serde_json::Value, field: &str) -> Result<Value, Strin
 
 #[cfg(test)]
 mod tests {
+    fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+        wip_protocol::InterfaceReference {
+            scope: "/".into(),
+            name: name.into(),
+        }
+    }
     use super::*;
     use wip_protocol::{
         EnumCase, FieldDeclaration, INTERFACE_FORMAT_V1, ParameterDeclaration, ReturnDeclaration,
@@ -560,7 +568,7 @@ mod tests {
             }],
         );
         let operation = descriptor.operations[0].clone();
-        let mut editor = ArgumentEditor::new("test", descriptor, operation);
+        let mut editor = ArgumentEditor::new(root_reference("test"), descriptor, operation);
         let inputs = [
             "null",
             "true",
@@ -595,7 +603,7 @@ mod tests {
             vec![],
         );
         let operation = descriptor.operations[0].clone();
-        let mut editor = ArgumentEditor::new("test", descriptor, operation);
+        let mut editor = ArgumentEditor::new(root_reference("test"), descriptor, operation);
         editor.fields[1].input = "not-a-bool".into();
         assert_eq!(editor.validate(), Err(InvalidArguments));
         assert!(

crates/wip-tui/src/render.rs

@@ -11,6 +11,14 @@ use crate::editor::type_name;
 
 const MAX_RENDER_TEXT: usize = 512;
 
+fn interface_label(reference: &wip_protocol::InterfaceReference) -> String {
+    format!(
+        "scope={}, name={}",
+        sanitize(&reference.scope),
+        sanitize(&reference.name)
+    )
+}
+
 /// Draws the complete application without mutating it.
 pub fn draw(frame: &mut Frame<'_>, app: &App) {
     let area = frame.area();
@@ -162,7 +170,7 @@ fn render_selected(frame: &mut Frame<'_>, area: Rect, app: &App) {
                         object
                             .interfaces
                             .iter()
-                            .map(|value| sanitize(value))
+                            .map(interface_label)
                             .collect::<Vec<_>>()
                             .join(", ")
                     }
@@ -224,7 +232,7 @@ fn operation_line(app: &App, row: &OperationRow) -> (Line<'static>, Style) {
                 .find(|operation| operation.name == *name)
         });
         let signature = declaration.map_or_else(
-            || format!("  ({}, {})", row.interface, name),
+            || format!("  ({}, {})", interface_label(&row.interface), name),
             |operation| {
                 let parameters = operation
                     .parameters
@@ -246,7 +254,7 @@ fn operation_line(app: &App, row: &OperationRow) -> (Line<'static>, Style) {
                     .unwrap_or_default();
                 format!(
                     "  ({}, {}) ({parameters}) -> {}{}",
-                    row.interface,
+                    interface_label(&row.interface),
                     name,
                     type_name(&operation.returns.r#type),
                     documentation
@@ -266,7 +274,7 @@ fn operation_line(app: &App, row: &OperationRow) -> (Line<'static>, Style) {
         (
             Line::from(format!(
                 "Interface {} [{}]{}",
-                sanitize(&row.interface),
+                interface_label(&row.interface),
                 state,
                 documentation
             )),
@@ -355,7 +363,7 @@ fn render_modal(frame: &mut Frame<'_>, app: &App) {
             let mut lines = vec![Line::from(format!(
                 "Target: {}  Operation: ({}, {})",
                 sanitize(&app.selected_path),
-                sanitize(&editor.interface),
+                interface_label(&editor.interface),
                 sanitize(&editor.operation.name)
             ))];
             if editor.fields.is_empty() {
@@ -405,7 +413,7 @@ fn render_modal(frame: &mut Frame<'_>, app: &App) {
                         .add_modifier(Modifier::BOLD),
                 ),
                 Line::from(format!("Entry: {}", sanitize(&app.selected_path))),
-                Line::from(format!("Interface: {}", sanitize(&editor.interface))),
+                Line::from(format!("Interface: {}", interface_label(&editor.interface))),
                 Line::from(format!("Operation: {}", sanitize(&editor.operation.name))),
                 Line::from("Input values:"),
             ];
@@ -579,6 +587,12 @@ fn bounded_value_at(value: &wip_protocol::Value, depth: usize) -> String {
 
 #[cfg(test)]
 mod tests {
+    fn root_reference(name: &str) -> wip_protocol::InterfaceReference {
+        wip_protocol::InterfaceReference {
+            scope: "/".into(),
+            name: name.into(),
+        }
+    }
     use ratatui::Terminal;
     use ratatui::backend::TestBackend;
 
@@ -664,7 +678,7 @@ mod tests {
             object: Some(Object {
                 name: String::new(),
                 description: Some("public root description".into()),
-                interfaces: vec!["demo-interface".into()],
+                interfaces: vec![root_reference("demo-interface")],
                 r#ref: None,
                 validator: Some(b"must-not-render".to_vec()),
             }),
@@ -691,7 +705,8 @@ mod tests {
             }],
         };
         app.apply_interface(InterfaceObservation {
-            reference: "demo-interface".into(),
+            scope_ref: None,
+            reference: root_reference("demo-interface"),
             descriptor: Some(descriptor.clone()),
             validator: Some(b"must-not-render".to_vec()),
             state: ObservationState::Fresh,
@@ -711,7 +726,7 @@ mod tests {
         }
         let snapshot = rendered(&app, 140, 40);
         assert!(snapshot.contains("public root description"));
-        assert!(snapshot.contains("(demo-interface, run)"));
+        assert!(snapshot.contains("(scope=/, name=demo-interface, run)"));
         assert!(snapshot.contains("SUCCESS"));
         assert!(snapshot.contains("PROTOCOL ERROR"));
         assert!(snapshot.contains("TRANSPORT FAILURE"));
@@ -719,7 +734,7 @@ mod tests {
         assert!(!snapshot.contains("must-not-render"));
 
         let mut editor = ArgumentEditor::new(
-            "demo-interface",
+            root_reference("demo-interface"),
             descriptor.clone(),
             descriptor.operations[0].clone(),
         );
@@ -774,7 +789,7 @@ mod tests {
             object: Some(Object {
                 name: String::new(),
                 description: None,
-                interfaces: vec!["many".into()],
+                interfaces: vec![root_reference("many")],
                 r#ref: None,
                 validator: None,
             }),
@@ -793,7 +808,8 @@ mod tests {
             })
             .collect::<Vec<_>>();
         app.apply_interface(InterfaceObservation {
-            reference: "many".into(),
+            scope_ref: None,
+            reference: root_reference("many"),
             descriptor: Some(InterfaceDescriptor {
                 format: INTERFACE_FORMAT_V1.into(),
                 documentation: None,
@@ -806,7 +822,7 @@ mod tests {
         app.focus = Focus::Operations;
         app.operation_cursor = app.operation_rows().len() - 1;
         let snapshot = rendered(&app, 100, 30);
-        assert!(snapshot.contains("(many, operation-19)"));
+        assert!(snapshot.contains("(scope=/, name=many, operation-19)"));
 
         for index in 0..20 {
             app.push_history(HistoryItem {
@@ -828,6 +844,19 @@ mod tests {
         assert!(snapshot.contains("too small"));
     }
 
+    #[test]
+    fn interface_labels_show_scope_and_name_without_parsing() {
+        let reference = wip_protocol::InterfaceReference {
+            scope: "/nested".into(),
+            name: "#::操作".into(),
+        };
+        assert_eq!(interface_label(&reference), "scope=/nested, name=#::操作");
+        assert_ne!(
+            interface_label(&reference),
+            interface_label(&root_reference(&reference.name))
+        );
+    }
+
     #[test]
     fn control_characters_and_large_bytes_are_bounded() {
         assert_eq!(sanitize("safe\u{1b}[31m"), "safe�[31m");

crates/wip-tui/src/runtime.rs

@@ -303,7 +303,10 @@ impl<T: Transport> Runtime<T> {
                 Err(error) => self.local_error("subtree refresh", error),
             },
             Action::FetchInterface(reference) => {
-                match self.client.prepare_interface(&self.session, &reference) {
+                match self
+                    .client
+                    .prepare_interface(&self.session, reference.clone())
+                {
                     Ok(request) => {
                         self.dispatch(request, InFlightKind::Interface(reference), false)
                     }
@@ -367,7 +370,10 @@ impl<T: Transport> Runtime<T> {
             }
         }
         for reference in references {
-            match self.client.ensure_interface(&self.session, &reference) {
+            match self
+                .client
+                .ensure_interface(&self.session, reference.clone())
+            {
                 Ok(Some(request)) => {
                     self.dispatch(request, InFlightKind::Interface(reference), false);
                 }
@@ -599,8 +605,9 @@ impl<T: Transport> Runtime<T> {
 
     fn push_call_history(&mut self, record: &wip_client::CallRecord) {
         let key = format!(
-            "({}, {}) on {}",
-            record.context.interface().reference,
+            "(scope={}, name={}, {}) on {}",
+            sanitize(&record.context.interface().reference.scope),
+            sanitize(&record.context.interface().reference.name),
             record.context.operation().name,
             record.context.object().path
         );
@@ -683,7 +690,11 @@ impl<T: Transport> Runtime<T> {
         let title = match kind {
             Some(InFlightKind::Object(path)) => format!("observe {path}"),
             Some(InFlightKind::Tree(path)) => format!("tree {path}"),
-            Some(InFlightKind::Interface(reference)) => format!("interface {reference}"),
+            Some(InFlightKind::Interface(reference)) => format!(
+                "interface scope={}, name={}",
+                sanitize(&reference.scope),
+                sanitize(&reference.name)
+            ),
             Some(InFlightKind::Operation { operation, .. }) => operation.clone(),
             None => "request".into(),
         };