feat: integrate persistent Subject behavior context

crates/server-api/src/lib.rs

@@ -237,6 +237,7 @@ impl_openapi_schema!(
     MemoryConsolidateStagingRequest,
     MemoryConsolidationResponse,
     SubjektivSubjectCreateRequest,
+    SubjektivSubjectBehaviorUpdateRequest,
     SubjektivSubjectListQuery,
     SubjektivSubjectListResponse,
     SubjektivSubjectResponse,
@@ -1163,6 +1164,20 @@ pub trait ServerApi {
         #[path] workspace_id: String,
         #[path] subject_id: String,
     ) -> Result<SubjektivSubjectResponse, RepositoryApiError>;
+    #[patch(
+        "/api/w/{workspace_id}/subjektiv/subjects/{subject_id}/behavior",
+        status = 200,
+        error_status = 400,
+        additional_error_statuses = [401, 403, 404, 409, 500],
+        bearer_auth = true,
+        browser_auth = true,
+    )]
+    async fn subjektiv_subject_behavior_update(
+        &self,
+        #[path] workspace_id: String,
+        #[path] subject_id: String,
+        #[body] request: SubjektivSubjectBehaviorUpdateRequest,
+    ) -> Result<SubjektivSubjectResponse, RepositoryApiError>;
     #[get(
         "/api/w/{workspace_id}/subjektiv/subjects/{subject_id}/surface",
         status = 200,
@@ -4579,9 +4594,20 @@ pub enum SubjektivSubjectState {
 #[serde(deny_unknown_fields)]
 pub struct SubjektivSubjectCreateRequest {
     pub role: String,
+    #[serde(default)]
+    pub behavior_md: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct SubjektivSubjectBehaviorUpdateRequest {
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub expected_behavior_revision: u64,
+    pub behavior_md: String,
 }
 
 pub const SUBJEKTIV_BROWSER_MAX_LIST_LIMIT: usize = 100;
+pub const SUBJEKTIV_MAX_BEHAVIOR_BYTES: usize = 16 * 1024;
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
 #[serde(deny_unknown_fields)]
@@ -4609,6 +4635,9 @@ pub struct SubjektivSubjectListResponse {
 pub struct SubjektivSubjectResponse {
     pub id: String,
     pub role: String,
+    pub behavior_md: String,
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub behavior_revision: u64,
     pub state: SubjektivSubjectState,
     #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
     pub store_revision: u64,
@@ -5442,10 +5471,22 @@ pub struct SubjektivSurfaceFailureResponse {
     pub status: String,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct SubjektivResidentContextOutput {
+    /// Exact user-managed document. Empty means explicitly unset.
+    pub behavior_md: String,
+    #[schemars(range(min = 0, max = 9_007_199_254_740_991_u64))]
+    pub behavior_revision: u64,
+    /// Independently-fresh generated Memory projection.
+    pub memory_surface: memory::backend::MemoryResidentSummaryOutput,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, JsonSchema)]
 #[serde(tag = "operation", content = "input", rename_all = "snake_case")]
 pub enum SubjektivMemoryBackendOperation {
     ResidentSummary(memory::backend::MemoryResidentSummaryOperation),
+    ResidentContext(memory::backend::MemoryResidentSummaryOperation),
     Query(SubjektivMemoryQueryRequest),
     Read(SubjektivMemoryReadRequest),
     ListRevisions(SubjektivMemoryListRevisionsRequest),
@@ -5618,6 +5659,7 @@ pub struct SubjektivMemoryStageExplicitResponse {
 #[serde(tag = "result", content = "data", rename_all = "snake_case")]
 pub enum SubjektivMemoryBackendResponse {
     ResidentSummary(memory::backend::MemoryResidentSummaryOutput),
+    ResidentContext(SubjektivResidentContextOutput),
     Query(SubjektivMemoryQueryResponse),
     Read(SubjektivMemoryReadResponse),
     ListRevisions(SubjektivMemoryListRevisionsResponse),
@@ -9861,9 +9903,11 @@ pub fn memory_api_typescript() -> String {
     // `ts-rs` solely for this read-only projection.
     let subjektiv_browser_declarations = r#"export type SubjektivSubjectState = "active" | "retired";
 
-export type SubjektivSubjectCreateRequest = { role: string, };
+export type SubjektivSubjectCreateRequest = { role: string, behavior_md?: string, };
 
-export type SubjektivSubjectResponse = { id: string, role: string, state: SubjektivSubjectState, store_revision: number, created_at: string, updated_at: string, current_worker?: | import("./worker-launch-api").WorkerLaunchWorkerSummary | null, };
+export type SubjektivSubjectBehaviorUpdateRequest = { expected_behavior_revision: number, behavior_md: string, };
+
+export type SubjektivSubjectResponse = { id: string, role: string, behavior_md: string, behavior_revision: number, state: SubjektivSubjectState, store_revision: number, created_at: string, updated_at: string, current_worker?: | import("./worker-launch-api").WorkerLaunchWorkerSummary | null, };
 
 export type SubjektivSubjectListResponse = { limit: number, items: Array<SubjektivSubjectResponse>, next_cursor?: string | null, has_more: boolean, };
 
@@ -9896,8 +9940,11 @@ export type SubjektivMemoryListRevisionsResponse = { memory_id: string, current_
     let limits = format!(
         "export const MEMORY_API_LIMITS = {{\n  maxResponseBytes: {MEMORY_API_MAX_RESPONSE_BYTES},\n  maxDocumentBytes: {MEMORY_API_MAX_DOCUMENT_BYTES},\n  maxCollectionItems: {MEMORY_API_MAX_COLLECTION_ITEMS},\n  maxStringBytes: {MEMORY_API_MAX_STRING_BYTES},\n  maxIdentifierBytes: {MEMORY_API_MAX_IDENTIFIER_BYTES},\n}} as const;"
     );
+    let subjektiv_limits = format!(
+        "export const SUBJEKTIV_API_LIMITS = {{\n  maxBehaviorBytes: {SUBJEKTIV_MAX_BEHAVIOR_BYTES},\n}} as const;"
+    );
     format!(
-        "// Generated from server-api. Do not edit by hand.\n// Regenerate: cargo run -q -p server-api --features typescript --example generate_memory_api_types > web/workspace/src/lib/generated/memory-api.ts\n\n{limits}\n\n{}\n\n{subjektiv_browser_declarations}\n",
+        "// Generated from server-api. Do not edit by hand.\n// Regenerate: cargo run -q -p server-api --features typescript --example generate_memory_api_types > web/workspace/src/lib/generated/memory-api.ts\n\n{limits}\n\n{subjektiv_limits}\n\n{}\n\n{subjektiv_browser_declarations}\n",
         declarations
             .into_iter()
             .map(|declaration| format!("export {declaration}"))

crates/session-store/src/system_item.rs

@@ -167,6 +167,15 @@ pub enum SystemItem {
         prompt_provenance: Option<PromptRenderProvenance>,
     },
 
+    /// A Host-fetched change to user-managed Subject behavior. Each changed
+    /// revision is appended rather than rewriting prior prompt/session content.
+    SubjectBehaviorRefresh {
+        body: String,
+        behavior_revision: u64,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        prompt_provenance: Option<PromptRenderProvenance>,
+    },
+
     /// Synthetic note inserted after an interrupted turn before the next
     /// user input. `body` is the exact LLM-context text explaining that the
     /// previous turn was cut short.
@@ -192,6 +201,7 @@ impl SystemItem {
             }
             SystemItem::TaskReminder { body, .. } => body.clone(),
             SystemItem::ResidentSummaryRefresh { body, .. } => body.clone(),
+            SystemItem::SubjectBehaviorRefresh { body, .. } => body.clone(),
             SystemItem::Interrupt { body, .. } => body.clone(),
         }
     }
@@ -214,6 +224,7 @@ impl SystemItem {
             SystemItem::LegacyIgnored { .. } => "legacy_ignored",
             SystemItem::TaskReminder { .. } => "task_reminder",
             SystemItem::ResidentSummaryRefresh { .. } => "resident_summary_refresh",
+            SystemItem::SubjectBehaviorRefresh { .. } => "subject_behavior_refresh",
             SystemItem::Interrupt { .. } => "interrupt",
         }
     }
@@ -270,6 +281,25 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn subject_behavior_refresh_round_trips_with_revision_and_exact_body() {
+        let item = SystemItem::SubjectBehaviorRefresh {
+            body: "current Subject context".to_string(),
+            behavior_revision: 7,
+            prompt_provenance: None,
+        };
+        let raw = serde_json::to_string(&item).unwrap();
+        let parsed: SystemItem = serde_json::from_str(&raw).unwrap();
+        assert_eq!(parsed.history_text(), "current Subject context");
+        assert!(matches!(
+            parsed,
+            SystemItem::SubjectBehaviorRefresh {
+                behavior_revision: 7,
+                ..
+            }
+        ));
+    }
+
     #[test]
     fn notification_history_text_returns_stored_body() {
         let item = SystemItem::Notification {

crates/tui/src/app.rs

@@ -2618,6 +2618,7 @@ impl App {
             session_store::SystemItem::FileAttachment { body, .. }
             | session_store::SystemItem::SkillActivation { body, .. }
             | session_store::SystemItem::ResidentSummaryRefresh { body, .. }
+            | session_store::SystemItem::SubjectBehaviorRefresh { body, .. }
             | session_store::SystemItem::Interrupt { body, .. } => {
                 self.task_store.apply_system_message_text(&body);
                 self.blocks.push(Block::SystemMessage { text: body });

crates/worker/src/controller.rs

@@ -1375,6 +1375,7 @@ where
         crate::feature::builtin::memory::ordinary_subjektiv_resident_summary_source(
             worker.manifest(),
             worker.workspace_client_handle(),
+            worker.prompts(),
         )?
     {
         let workspace_id = worker

crates/worker/src/feature/builtin/memory.rs

@@ -4,7 +4,8 @@
 //! authority. In that case model-visible Memory tools must go through the
 //! workspace backend instead of resolving `.yoi/memory` from a Worker workdir.
 
-use std::sync::Arc;
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
 use agen::tool::{Tool, ToolDefinition, ToolError, ToolExecutionContext, ToolMeta, ToolOutput};
@@ -24,11 +25,15 @@ use crate::feature::{
     FeatureDescriptor, FeatureHookPoint, FeatureInstallContext, FeatureInstallError, FeatureModule,
     HookDeclaration, ToolContribution, ToolDeclaration,
 };
-use crate::hook::{Hook, HookError, HookErrorCategory, HookExecutionPolicy, WorkerRestored};
+use crate::hook::{
+    BeforeSessionRewrite, BeforeSessionRewriteAction, BeforeSessionRewriteContext, Hook, HookError,
+    HookErrorCategory, HookExecutionPolicy, HookPreRequestAction, PreLlmRequest, PreRequestContext,
+    WorkerRestored,
+};
 use crate::prompt::catalog::{PromptCatalog, WorkerPrompt};
 use crate::worker::{
-    SystemPromptContribution, SystemPromptContributionSource, WorkspaceClient,
+    ResidentContextRefresh, SystemPromptContribution, SystemPromptContributionSource,
-    WorkspaceClientError, WorkspaceRequest, WorkspaceRequestMethod,
+    WorkspaceClient, WorkspaceClientError, WorkspaceRequest, WorkspaceRequestMethod,
 };
 
 #[derive(Clone, Debug)]
@@ -74,6 +79,8 @@ pub enum WorkspaceMemoryBackendError {
     Decode(#[from] serde_json::Error),
     #[error("workspace memory backend rejected operation: {0}")]
     Backend(String),
+    #[error("workspace memory backend returned an invalid response: {0}")]
+    InvalidResponse(String),
 }
 
 impl dyn WorkspaceClient + '_ {
@@ -672,12 +679,17 @@ struct WorkspaceResidentSummarySource {
     client: Arc<dyn WorkspaceClient>,
 }
 
-struct WorkspaceSubjektivResidentSummarySource {
+#[derive(Default)]
-    client: Arc<dyn WorkspaceClient>,
+struct SubjectBehaviorRefreshState {
+    applied: Option<(u64, String)>,
+    pending: HashMap<u64, String>,
 }
 
-const READY_EMPTY_RESIDENT_SURFACE: &str =
+struct WorkspaceSubjektivResidentSummarySource {
-    "The current ready resident memory surface is intentionally empty.";
+    client: Arc<dyn WorkspaceClient>,
+    prompts: Arc<ArcSwap<PromptCatalog>>,
+    behavior_state: Mutex<SubjectBehaviorRefreshState>,
+}
 
 fn resident_summary_contribution(
     output: memory::backend::MemoryResidentSummaryOutput,
@@ -715,37 +727,133 @@ impl SystemPromptContributionSource for WorkspaceResidentSummarySource {
     }
 }
 
-#[async_trait]
+impl WorkspaceSubjektivResidentSummarySource {
-impl SystemPromptContributionSource for WorkspaceSubjektivResidentSummarySource {
+    async fn fetch(
-    async fn load(&self) -> SystemPromptContribution {
+        &self,
+    ) -> Result<server_api::SubjektivResidentContextOutput, WorkspaceMemoryBackendError> {
         match execute_subjektiv_memory_operation_with(
             self.client.as_ref(),
-            server_api::SubjektivMemoryBackendOperation::ResidentSummary(Default::default()),
+            server_api::SubjektivMemoryBackendOperation::ResidentContext(Default::default()),
             |client, request| {
                 client.execute_with_timeout(request, RESIDENT_SUMMARY_REQUEST_TIMEOUT)
             },
-        ) {
+        )? {
-            Ok(server_api::SubjektivMemoryBackendResponse::ResidentSummary(output)) => {
+            server_api::SubjektivMemoryBackendResponse::ResidentContext(output) => Ok(output),
-                match resident_summary_contribution(output) {
+            other => Err(WorkspaceMemoryBackendError::InvalidResponse(format!(
-                    SystemPromptContribution::Ready(content) if content.trim().is_empty() => {
+                "unexpected subject resident context response: {other:?}"
-                        SystemPromptContribution::Ready(READY_EMPTY_RESIDENT_SURFACE.to_string())
+            ))),
-                    }
+        }
-                    contribution => contribution,
+    }
+
+    fn render(
+        &self,
+        output: &server_api::SubjektivResidentContextOutput,
+    ) -> Result<String, String> {
+        use memory::backend::MemoryResidentSummaryAvailability as Availability;
+        let availability = match output.memory_surface.availability {
+            Availability::Ready => "ready",
+            Availability::Ungenerated => "ungenerated",
+            Availability::Stale => "stale",
+            Availability::Failed => "failed",
+            Availability::Unavailable => "unavailable",
+        };
+        self.prompts
+            .load()
+            .subjektiv_resident_context(
+                &output.behavior_md,
+                availability,
+                output.memory_surface.content.as_deref(),
+            )
+            .map_err(|error| error.to_string())
+    }
+
+    fn remember_behavior(&self, output: &server_api::SubjektivResidentContextOutput) {
+        let mut state = self
+            .behavior_state
+            .lock()
+            .expect("subject behavior state poisoned");
+        state.applied = Some((output.behavior_revision, output.behavior_md.clone()));
+        state.pending.remove(&output.behavior_revision);
+    }
+}
+
+#[async_trait]
+impl SystemPromptContributionSource for WorkspaceSubjektivResidentSummarySource {
+    async fn load(&self) -> SystemPromptContribution {
+        match self.fetch().await {
+            Ok(output) => match self.render(&output) {
+                Ok(rendered) => {
+                    self.remember_behavior(&output);
+                    SystemPromptContribution::Ready(rendered)
                 }
-            }
+                Err(error) => {
-            Ok(other) => {
+                    tracing::error!(%error, "subject resident context render failed");
-                tracing::debug!(?other, "unexpected subject resident Memory response");
+                    SystemPromptContribution::Ready(
-                SystemPromptContribution::Unavailable
+                        "The Host could not render the Subject resident context. Do not treat this as unset behavior or infer replacement behavior from Memory."
-            }
+                            .to_string(),
+                    )
+                }
+            },
             Err(error) => {
-                tracing::debug!(%error, "subject resident Memory unavailable");
+                tracing::error!(%error, "subject resident context fetch failed");
-                SystemPromptContribution::Unavailable
+                SystemPromptContribution::Ready(
+                    "The Host could not fetch the Subject resident context. Do not treat this as unset behavior or infer replacement behavior from Memory."
+                        .to_string(),
+                )
             }
         }
     }
+
+    async fn load_changed_resident_context(
+        &self,
+    ) -> Result<Option<ResidentContextRefresh>, String> {
+        let output = self.fetch().await.map_err(|error| error.to_string())?;
+        let changed = self
+            .behavior_state
+            .lock()
+            .expect("subject behavior state poisoned")
+            .applied
+            .as_ref()
+            .is_none_or(|(revision, body)| {
+                *revision != output.behavior_revision || body != &output.behavior_md
+            });
+        if !changed {
+            return Ok(None);
+        }
+        let rendered = self.render(&output)?;
+        let revision = output.behavior_revision;
+        self.behavior_state
+            .lock()
+            .expect("subject behavior state poisoned")
+            .pending
+            .insert(revision, output.behavior_md);
+        Ok(Some(ResidentContextRefresh {
+            body: rendered,
+            revision,
+        }))
+    }
+
+    fn confirm_resident_context_revision(&self, revision: u64) {
+        let mut state = self
+            .behavior_state
+            .lock()
+            .expect("subject behavior state poisoned");
+        if let Some(body) = state.pending.remove(&revision) {
+            state.applied = Some((revision, body));
+        }
+    }
+
+    fn invalidate_resident_context_representation(&self) {
+        self.behavior_state
+            .lock()
+            .expect("subject behavior state poisoned")
+            .applied = None;
+    }
 }
 
 const SUBJEKTIV_RESTORE_REFRESH_HOOK: &str = "refresh-resident-surface-after-restore";
+const SUBJEKTIV_BEHAVIOR_REFRESH_HOOK: &str = "refresh-subject-behavior-before-request";
+const SUBJEKTIV_BEHAVIOR_REWRITE_HOOK: &str = "invalidate-subject-behavior-before-rewrite";
 
 /// subjektiv-owned restore behavior. Initial prompt contribution remains a
 /// shared host facility, while loading and rendering a post-restore refresh is
@@ -793,6 +901,14 @@ impl FeatureModule for SubjektivResidentRestoreRefreshFeature {
             SUBJEKTIV_RESTORE_REFRESH_HOOK,
             FeatureHookPoint::WorkerRestored,
         ))
+        .with_hook(HookDeclaration::new(
+            SUBJEKTIV_BEHAVIOR_REFRESH_HOOK,
+            FeatureHookPoint::PreLlmRequest,
+        ))
+        .with_hook(HookDeclaration::new(
+            SUBJEKTIV_BEHAVIOR_REWRITE_HOOK,
+            FeatureHookPoint::BeforeSessionRewrite,
+        ))
     }
 
     fn install(&self, context: &mut FeatureInstallContext<'_>) -> Result<(), FeatureInstallError> {
@@ -804,10 +920,64 @@ impl FeatureModule for SubjektivResidentRestoreRefreshFeature {
                 prompts: Arc::clone(&self.prompts),
                 workspace_id: self.workspace_id.clone(),
             },
+        )?;
+        context.hooks().add_pre_llm_request(
+            SUBJEKTIV_BEHAVIOR_REFRESH_HOOK,
+            HookExecutionPolicy::fail_closed(),
+            SubjektivBehaviorRefreshHook {
+                source: Arc::clone(&self.source),
+            },
+        )?;
+        context.hooks().add_before_session_rewrite(
+            SUBJEKTIV_BEHAVIOR_REWRITE_HOOK,
+            HookExecutionPolicy::fail_closed(),
+            SubjektivBehaviorRewriteHook {
+                source: Arc::clone(&self.source),
+            },
         )
     }
 }
 
+struct SubjektivBehaviorRewriteHook {
+    source: Arc<dyn SystemPromptContributionSource>,
+}
+
+#[async_trait]
+impl Hook<BeforeSessionRewrite> for SubjektivBehaviorRewriteHook {
+    async fn call(
+        &self,
+        _context: &BeforeSessionRewriteContext,
+    ) -> Result<BeforeSessionRewriteAction, HookError> {
+        self.source.invalidate_resident_context_representation();
+        Ok(BeforeSessionRewriteAction::Continue)
+    }
+}
+
+struct SubjektivBehaviorRefreshHook {
+    source: Arc<dyn SystemPromptContributionSource>,
+}
+
+#[async_trait]
+impl Hook<PreLlmRequest> for SubjektivBehaviorRefreshHook {
+    async fn call(&self, context: &PreRequestContext) -> Result<HookPreRequestAction, HookError> {
+        let refresh = self
+            .source
+            .load_changed_resident_context()
+            .await
+            .map_err(|error| HookError::new(HookErrorCategory::Dependency, error))?;
+        if let Some(refresh) = refresh {
+            let system_items = context.system_items().ok_or_else(|| {
+                HookError::new(
+                    HookErrorCategory::Dependency,
+                    "Subject behavior refresh requires durable session append authority",
+                )
+            })?;
+            system_items.append_subject_behavior_refresh(refresh.body, refresh.revision);
+        }
+        Ok(HookPreRequestAction::Continue)
+    }
+}
+
 struct SubjektivResidentRestoreRefreshHook {
     source: Arc<dyn SystemPromptContributionSource>,
     prompts: Arc<ArcSwap<PromptCatalog>>,
@@ -951,6 +1121,7 @@ pub(crate) fn ordinary_subjektiv_features_enabled(manifest: &manifest::WorkerMan
 pub(crate) fn ordinary_subjektiv_resident_summary_source(
     manifest: &manifest::WorkerManifest,
     client: Arc<dyn WorkspaceClient>,
+    prompts: Arc<ArcSwap<PromptCatalog>>,
 ) -> std::io::Result<Option<Arc<dyn SystemPromptContributionSource>>> {
     if !ordinary_subjektiv_features_enabled(manifest) {
         return Ok(None);
@@ -988,6 +1159,8 @@ pub(crate) fn ordinary_subjektiv_resident_summary_source(
     }
     Ok(Some(Arc::new(WorkspaceSubjektivResidentSummarySource {
         client,
+        prompts,
+        behavior_state: Mutex::new(SubjectBehaviorRefreshState::default()),
     })))
 }
 
@@ -1120,6 +1293,10 @@ mod tests {
     use agen::tool::ToolDefinition;
     use std::sync::Mutex;
 
+    fn test_prompts() -> Arc<ArcSwap<PromptCatalog>> {
+        Arc::new(ArcSwap::from(PromptCatalog::builtins_only().unwrap()))
+    }
+
     fn test_client() -> Arc<dyn WorkspaceClient> {
         Arc::new(crate::worker::TestWorkspaceHttpClient::new(
             "workspace",
@@ -1132,6 +1309,7 @@ mod tests {
         availability: memory::backend::MemoryResidentSummaryAvailability,
         content: Option<String>,
         scope_allowed: bool,
+        behavior: Mutex<(u64, String)>,
         paths: Mutex<Vec<String>>,
         timeouts: Mutex<Vec<Duration>>,
     }
@@ -1145,6 +1323,7 @@ mod tests {
                 availability,
                 content: content.map(str::to_string),
                 scope_allowed: true,
+                behavior: Mutex::new((3, "Be deliberate.".to_string())),
                 paths: Mutex::new(Vec::new()),
                 timeouts: Mutex::new(Vec::new()),
             }
@@ -1155,6 +1334,7 @@ mod tests {
                 availability: memory::backend::MemoryResidentSummaryAvailability::Ready,
                 content: Some("must not be injected".into()),
                 scope_allowed: false,
+                behavior: Mutex::new((3, "must not be injected".to_string())),
                 paths: Mutex::new(Vec::new()),
                 timeouts: Mutex::new(Vec::new()),
             }
@@ -1184,7 +1364,7 @@ mod tests {
                 serde_json::from_str(request.body.as_deref().unwrap_or_default()).unwrap();
             assert!(matches!(
                 request.operation,
-                server_api::SubjektivMemoryBackendOperation::ResidentSummary(_)
+                server_api::SubjektivMemoryBackendOperation::ResidentContext(_)
             ));
             if !self.scope_allowed {
                 return Ok(WorkspaceResponse {
@@ -1192,13 +1372,18 @@ mod tests {
                     body: "subject scope unavailable".into(),
                 });
             }
+            let (behavior_revision, behavior_md) = self.behavior.lock().unwrap().clone();
             Ok(WorkspaceResponse {
                 status: 200,
                 body: serde_json::to_string(
-                    &server_api::SubjektivMemoryBackendResponse::ResidentSummary(
+                    &server_api::SubjektivMemoryBackendResponse::ResidentContext(
-                        memory::backend::MemoryResidentSummaryOutput {
+                        server_api::SubjektivResidentContextOutput {
-                            availability: self.availability,
+                            behavior_md,
-                            content: self.content.clone(),
+                            behavior_revision,
+                            memory_surface: memory::backend::MemoryResidentSummaryOutput {
+                                availability: self.availability,
+                                content: self.content.clone(),
+                            },
                         },
                     ),
                 )
@@ -1511,13 +1696,19 @@ permission = "write"
             memory::backend::MemoryResidentSummaryAvailability::Ready,
             Some("current subject surface"),
         ));
-        let ready = ordinary_subjektiv_resident_summary_source(&manifest, ready_client.clone())
+        let ready = ordinary_subjektiv_resident_summary_source(
-            .unwrap()
+            &manifest,
-            .unwrap();
+            ready_client.clone(),
-        assert_eq!(
+            test_prompts(),
-            ready.load().await,
+        )
-            SystemPromptContribution::Ready("current subject surface".into())
+        .unwrap()
-        );
+        .unwrap();
+        let loaded = ready.load().await;
+        let SystemPromptContribution::Ready(loaded) = loaded else {
+            panic!("subject resident context must be present");
+        };
+        assert!(loaded.contains("Be deliberate."));
+        assert!(loaded.contains("current subject surface"));
         assert_eq!(
             ready_client.paths.lock().unwrap().clone(),
             vec!["/api/w/workspace/subjektiv/memory".to_string()]
@@ -1531,13 +1722,18 @@ permission = "write"
             memory::backend::MemoryResidentSummaryAvailability::Ready,
             None,
         ));
-        let ready_empty = ordinary_subjektiv_resident_summary_source(&manifest, ready_empty_client)
+        let ready_empty = ordinary_subjektiv_resident_summary_source(
-            .unwrap()
+            &manifest,
-            .unwrap();
+            ready_empty_client,
-        assert_eq!(
+            test_prompts(),
-            ready_empty.load().await,
+        )
-            SystemPromptContribution::Ready(READY_EMPTY_RESIDENT_SURFACE.into())
+        .unwrap()
-        );
+        .unwrap();
+        let SystemPromptContribution::Ready(ready_empty) = ready_empty.load().await else {
+            panic!("empty surface must retain Subject behavior");
+        };
+        assert!(ready_empty.contains("Be deliberate."));
+        assert!(ready_empty.contains("intentionally empty"));
 
         for availability in [
             memory::backend::MemoryResidentSummaryAvailability::Ungenerated,
@@ -1550,22 +1746,107 @@ permission = "write"
                     availability,
                     Some("must not be injected"),
                 )),
+                test_prompts(),
             )
             .unwrap()
             .unwrap();
-            assert_eq!(source.load().await, SystemPromptContribution::Unavailable);
+            let SystemPromptContribution::Ready(loaded) = source.load().await else {
+                panic!("Subject behavior must survive unavailable surfaces");
+            };
+            assert!(loaded.contains("Be deliberate."));
+            assert!(!loaded.contains("must not be injected"));
         }
     }
 
+    #[tokio::test]
+    async fn subject_resident_source_emits_only_changed_behavior_revisions() {
+        let manifest = subject_manifest("workspace");
+        let client = Arc::new(SubjectResidentClient::new(
+            memory::backend::MemoryResidentSummaryAvailability::Ungenerated,
+            None,
+        ));
+        let source =
+            ordinary_subjektiv_resident_summary_source(&manifest, client.clone(), test_prompts())
+                .unwrap()
+                .unwrap();
+
+        let initial = source.load().await;
+        assert!(matches!(initial, SystemPromptContribution::Ready(_)));
+        assert!(
+            source
+                .load_changed_resident_context()
+                .await
+                .unwrap()
+                .is_none()
+        );
+
+        *client.behavior.lock().unwrap() = (4, "Ask when uncertain.".to_string());
+        let refresh = source
+            .load_changed_resident_context()
+            .await
+            .unwrap()
+            .expect("changed behavior must produce one refresh");
+        assert_eq!(refresh.revision, 4);
+        assert!(refresh.body.contains("Ask when uncertain."));
+        source.confirm_resident_context_revision(refresh.revision);
+        assert!(
+            source
+                .load_changed_resident_context()
+                .await
+                .unwrap()
+                .is_none()
+        );
+
+        *client.behavior.lock().unwrap() = (5, String::new());
+        let cleared = source
+            .load_changed_resident_context()
+            .await
+            .unwrap()
+            .expect("cleared behavior must produce one refresh");
+        assert_eq!(cleared.revision, 5);
+        assert!(cleared.body.contains("No user-managed behavior is set"));
+        source.confirm_resident_context_revision(cleared.revision);
+        assert!(
+            source
+                .load_changed_resident_context()
+                .await
+                .unwrap()
+                .is_none()
+        );
+
+        source.invalidate_resident_context_representation();
+        let replay_after_rewrite = source
+            .load_changed_resident_context()
+            .await
+            .unwrap()
+            .expect("history rewrite must require a durable current representation");
+        assert_eq!(replay_after_rewrite.revision, 5);
+        assert!(
+            replay_after_rewrite
+                .body
+                .contains("No user-managed behavior is set")
+        );
+        // Initial load and every live update/clear/replay probe retain the
+        // target-side bounded resident request contract.
+        assert_eq!(
+            client.timeouts.lock().unwrap().as_slice(),
+            &[RESIDENT_SUMMARY_REQUEST_TIMEOUT; 7]
+        );
+    }
+
     #[tokio::test]
     async fn subject_resident_source_fails_closed_without_trusted_subject_scope() {
         let manifest = subject_manifest("workspace");
         let client = Arc::new(SubjectResidentClient::denied());
-        let source = ordinary_subjektiv_resident_summary_source(&manifest, client.clone())
+        let source =
-            .unwrap()
+            ordinary_subjektiv_resident_summary_source(&manifest, client.clone(), test_prompts())
-            .unwrap();
+                .unwrap()
+                .unwrap();
 
-        assert_eq!(source.load().await, SystemPromptContribution::Unavailable);
+        let SystemPromptContribution::Ready(failure) = source.load().await else {
+            panic!("fetch failure must be explicit in resident context");
+        };
+        assert!(failure.contains("could not fetch"));
         assert_eq!(
             client.paths.lock().unwrap().clone(),
             vec!["/api/w/workspace/subjektiv/memory".to_string()]
@@ -1593,7 +1874,7 @@ permission = "write"
         )
         .unwrap();
         assert!(
-            ordinary_subjektiv_resident_summary_source(&disabled, test_client())
+            ordinary_subjektiv_resident_summary_source(&disabled, test_client(), test_prompts())
                 .unwrap()
                 .is_none()
         );
@@ -1605,22 +1886,30 @@ permission = "write"
             Some("policy-only surface must not load"),
         ));
         assert!(
-            ordinary_subjektiv_resident_summary_source(&policy_only, unattached_client.clone())
+            ordinary_subjektiv_resident_summary_source(
-                .unwrap()
+                &policy_only,
-                .is_none()
+                unattached_client.clone(),
+                test_prompts()
+            )
+            .unwrap()
+            .is_none()
         );
         assert!(unattached_client.paths.lock().unwrap().is_empty());
 
         let foreign = subject_manifest("other-workspace");
-        assert!(ordinary_subjektiv_resident_summary_source(&foreign, test_client()).is_err());
+        assert!(
+            ordinary_subjektiv_resident_summary_source(&foreign, test_client(), test_prompts())
+                .is_err()
+        );
     }
 
     #[test]
     fn subject_restore_refresh_is_suppressed_for_internal_hosts() {
         let manifest = subject_manifest("workspace");
-        let source = ordinary_subjektiv_resident_summary_source(&manifest, test_client())
+        let source =
-            .unwrap()
+            ordinary_subjektiv_resident_summary_source(&manifest, test_client(), test_prompts())
-            .unwrap();
+                .unwrap()
+                .unwrap();
         let prompts = Arc::new(ArcSwap::from(
             crate::prompt::catalog::PromptCatalog::builtins_only().unwrap(),
         ));
@@ -1634,9 +1923,10 @@ permission = "write"
     #[test]
     fn subject_restore_refresh_feature_declares_only_restore_lifecycle() {
         let manifest = subject_manifest("workspace");
-        let source = ordinary_subjektiv_resident_summary_source(&manifest, test_client())
+        let source =
-            .unwrap()
+            ordinary_subjektiv_resident_summary_source(&manifest, test_client(), test_prompts())
-            .unwrap();
+                .unwrap()
+                .unwrap();
         let feature = SubjektivResidentRestoreRefreshFeature::new(
             source,
             Arc::new(ArcSwap::from(
@@ -1647,8 +1937,13 @@ permission = "write"
         let descriptor = feature.descriptor();
 
         assert!(descriptor.tools.is_empty());
-        assert_eq!(descriptor.hooks.len(), 1);
+        assert_eq!(descriptor.hooks.len(), 3);
         assert_eq!(descriptor.hooks[0].point, FeatureHookPoint::WorkerRestored);
+        assert_eq!(descriptor.hooks[1].point, FeatureHookPoint::PreLlmRequest);
+        assert_eq!(
+            descriptor.hooks[2].point,
+            FeatureHookPoint::BeforeSessionRewrite
+        );
     }
 
     #[test]

crates/worker/src/hook.rs

@@ -281,6 +281,20 @@ impl SystemItemAppendHandle {
             .expect("system-item append queue poisoned")
             .push(item);
     }
+
+    /// Queue a revisioned Subject behavior refresh. The caller receives this
+    /// narrow operation only at a pre-request boundary, and the host commits it
+    /// before exposing it to the model.
+    pub fn append_subject_behavior_refresh(&self, body: impl Into<String>, behavior_revision: u64) {
+        self.pending
+            .lock()
+            .expect("system-item append queue poisoned")
+            .push(SystemItem::SubjectBehaviorRefresh {
+                body: body.into(),
+                behavior_revision,
+                prompt_provenance: None,
+            });
+    }
 }
 
 /// Host-created narrow append authority exposed only at a restore lifecycle

crates/worker/src/ipc/interceptor.rs

@@ -38,7 +38,7 @@ use crate::hook::{
 use crate::ipc::notify_buffer::{NotifyBuffer, build_system_item_with_provenance};
 use crate::prompt::catalog::PromptCatalog;
 use crate::session_history::SessionHistoryMetadata;
-use crate::worker::SystemItemCommitter;
+use crate::worker::{SystemItemCommitter, SystemPromptContributionSource};
 use agen::HistoryEntry;
 use agen::token_counter::total_tokens;
 
@@ -109,6 +109,7 @@ pub(crate) struct WorkerInterceptor {
     /// worker. `None` in tests / `Worker::new` paths where no writer is
     /// attached.
     log_writer: Option<Arc<dyn SystemItemCommitter>>,
+    resident_context_source: Option<Arc<dyn SystemPromptContributionSource>>,
     pending_committed_history: Arc<Mutex<VecDeque<HistoryEntry<SessionHistoryMetadata>>>>,
     /// Next turn index assigned by `on_prompt_submit`.
     next_turn_index: AtomicUsize,
@@ -163,6 +164,7 @@ impl WorkerInterceptor {
             prompts,
             prompt_workspace_id: None,
             log_writer,
+            resident_context_source: None,
             pending_committed_history,
             next_turn_index: AtomicUsize::new(0),
             tool_calls_this_turn: AtomicUsize::new(0),
@@ -179,11 +181,31 @@ impl WorkerInterceptor {
         self
     }
 
+    pub(crate) fn with_resident_context_source(
+        mut self,
+        source: Option<Arc<dyn SystemPromptContributionSource>>,
+    ) -> Self {
+        self.resident_context_source = source;
+        self
+    }
+
     pub(crate) fn with_prompt_workspace_id(mut self, workspace_id: Option<String>) -> Self {
         self.prompt_workspace_id = workspace_id;
         self
     }
 
+    fn confirm_resident_context_item(&self, item: &SystemItem) {
+        let Some(source) = self.resident_context_source.as_ref() else {
+            return;
+        };
+        if let SystemItem::SubjectBehaviorRefresh {
+            behavior_revision, ..
+        } = item
+        {
+            source.confirm_resident_context_revision(*behavior_revision);
+        }
+    }
+
     /// Commit each `SystemItem` as its own `LogEntry::AnnotatedSystemItem`
     /// entry through the attached writer (no-op when no writer is
     /// wired). Sync — writes complete before the matching
@@ -211,6 +233,7 @@ impl WorkerInterceptor {
                 .lock()
                 .expect("pending committed history poisoned")
                 .push_back(entry);
+            self.confirm_resident_context_item(item);
         }
         Ok(())
     }
@@ -350,6 +373,11 @@ impl WorkerInterceptor {
                 } if prompt_provenance.is_none() => {
                     *prompt_provenance = Some(provenance("internal.task_reminder"));
                 }
+                SystemItem::SubjectBehaviorRefresh {
+                    prompt_provenance, ..
+                } if prompt_provenance.is_none() => {
+                    *prompt_provenance = Some(provenance("internal.subjektiv_resident_context"));
+                }
                 SystemItem::Interrupt {
                     prompt_provenance, ..
                 } if prompt_provenance.is_none() => {
@@ -763,6 +791,7 @@ mod tests {
         HookTurnEndAction, OnTurnEnd, PostToolCall, PreLlmRequest, PreToolCall,
     };
     use crate::session_history::{WorkerHistoryProvenance, history_entry};
+    use crate::worker::SystemPromptContribution;
 
     fn test_prompts() -> Arc<ArcSwap<PromptCatalog>> {
         Arc::new(ArcSwap::from(PromptCatalog::builtins_only().unwrap()))
@@ -859,6 +888,53 @@ mod tests {
         }
     }
 
+    struct AppendingSubjectBehaviorHook;
+
+    #[async_trait]
+    impl Hook<PreLlmRequest> for AppendingSubjectBehaviorHook {
+        async fn call(
+            &self,
+            input: &PreRequestContext,
+        ) -> Result<HookPreRequestAction, crate::hook::HookError> {
+            input
+                .system_items()
+                .expect("test interceptor has durable append authority")
+                .append_subject_behavior_refresh("current Subject context", 7);
+            Ok(HookPreRequestAction::Continue)
+        }
+    }
+
+    struct ConfirmRecordingResidentSource {
+        confirmed: Arc<Mutex<Vec<u64>>>,
+    }
+
+    #[async_trait]
+    impl SystemPromptContributionSource for ConfirmRecordingResidentSource {
+        async fn load(&self) -> SystemPromptContribution {
+            SystemPromptContribution::Unavailable
+        }
+
+        fn confirm_resident_context_revision(&self, revision: u64) {
+            self.confirmed.lock().unwrap().push(revision);
+        }
+    }
+
+    struct FailingSystemItemCommitter;
+
+    impl SystemItemCommitter for FailingSystemItemCommitter {
+        fn commit_log_entry(
+            &self,
+            entry: session_store::LogEntry,
+        ) -> Result<(), session_store::StoreError> {
+            if matches!(entry, session_store::LogEntry::AnnotatedSystemItem { .. }) {
+                return Err(session_store::StoreError::Io(std::io::Error::other(
+                    "synthetic system-item failure",
+                )));
+            }
+            Ok(())
+        }
+    }
+
     fn task_tool_call_info(
         name: &str,
         input: serde_json::Value,
@@ -1346,6 +1422,88 @@ mod tests {
         }
     }
 
+    #[tokio::test]
+    async fn subject_behavior_revision_is_confirmed_only_after_durable_commit() {
+        let mut builder = HookRegistryBuilder::new();
+        builder.add_pre_llm_request(AppendingSubjectBehaviorHook);
+        let committed = Arc::new(Mutex::new(Vec::new()));
+        let confirmed = Arc::new(Mutex::new(Vec::new()));
+        let source: Arc<dyn SystemPromptContributionSource> =
+            Arc::new(ConfirmRecordingResidentSource {
+                confirmed: Arc::clone(&confirmed),
+            });
+        let interceptor = WorkerInterceptor::new(
+            Arc::new(builder.build()),
+            None,
+            None,
+            NotifyBuffer::new(),
+            Arc::new(Mutex::new(Vec::new())),
+            test_prompts(),
+            Some(Arc::new(RecordingSystemItemCommitter {
+                committed: Arc::clone(&committed),
+            })),
+        )
+        .with_resident_context_source(Some(source));
+
+        let mut ctx = Vec::new();
+        let action = interceptor
+            .pre_llm_request(PreLlmRequestContext {
+                invocation: Default::default(),
+                items: &mut ctx,
+                history: &[],
+            })
+            .await
+            .unwrap();
+
+        assert!(matches!(action, PreRequestAction::ContinueWith(_)));
+        assert_eq!(*confirmed.lock().unwrap(), [7]);
+        assert!(matches!(
+            committed.lock().unwrap().as_slice(),
+            [SystemItem::SubjectBehaviorRefresh {
+                behavior_revision: 7,
+                prompt_provenance: Some(_),
+                ..
+            }]
+        ));
+    }
+
+    #[tokio::test]
+    async fn failed_subject_behavior_persistence_does_not_confirm_revision() {
+        let mut builder = HookRegistryBuilder::new();
+        builder.add_pre_llm_request(AppendingSubjectBehaviorHook);
+        let confirmed = Arc::new(Mutex::new(Vec::new()));
+        let source: Arc<dyn SystemPromptContributionSource> =
+            Arc::new(ConfirmRecordingResidentSource {
+                confirmed: Arc::clone(&confirmed),
+            });
+        let interceptor = WorkerInterceptor::new(
+            Arc::new(builder.build()),
+            None,
+            None,
+            NotifyBuffer::new(),
+            Arc::new(Mutex::new(Vec::new())),
+            test_prompts(),
+            Some(Arc::new(FailingSystemItemCommitter)),
+        )
+        .with_resident_context_source(Some(source));
+
+        let mut ctx = Vec::new();
+        let action = interceptor
+            .pre_llm_request(PreLlmRequestContext {
+                invocation: Default::default(),
+                items: &mut ctx,
+                history: &[],
+            })
+            .await
+            .unwrap();
+
+        assert!(matches!(
+            action,
+            PreRequestAction::Cancel(reason) if reason.contains("session persistence failed")
+        ));
+        assert!(confirmed.lock().unwrap().is_empty());
+    }
+
     #[tokio::test]
     async fn pre_llm_request_without_log_writer_does_not_expose_system_item_handle() {
         let saw_handle = Arc::new(AtomicBool::new(false));

crates/worker/src/prompt/catalog.rs

@@ -105,6 +105,7 @@ pub enum WorkerPrompt {
     AgentsMdSection,
     ResidentMemorySummarySection,
     ResidentMemoryRestoreSection,
+    SubjektivResidentContext,
     WorkerOrchestrationGuidanceSection,
     SubWorkerSpawnToolDescription,
 }
@@ -128,6 +129,7 @@ impl WorkerPrompt {
             Self::AgentsMdSection => "internal.agents_md_section",
             Self::ResidentMemorySummarySection => "internal.resident_memory_summary_section",
             Self::ResidentMemoryRestoreSection => "internal.resident_memory_restore_section",
+            Self::SubjektivResidentContext => "internal.subjektiv_resident_context",
             Self::WorkerOrchestrationGuidanceSection => {
                 "internal.worker_orchestration_guidance_section"
             }
@@ -150,6 +152,7 @@ impl WorkerPrompt {
         WorkerPrompt::AgentsMdSection,
         WorkerPrompt::ResidentMemorySummarySection,
         WorkerPrompt::ResidentMemoryRestoreSection,
+        WorkerPrompt::SubjektivResidentContext,
         WorkerPrompt::WorkerOrchestrationGuidanceSection,
         WorkerPrompt::SubWorkerSpawnToolDescription,
     ];
@@ -518,6 +521,21 @@ impl PromptCatalog {
             },
         )
     }
+    pub fn subjektiv_resident_context(
+        &self,
+        behavior_md: &str,
+        surface_availability: &str,
+        surface_body: Option<&str>,
+    ) -> Result<String, CatalogError> {
+        self.render(
+            WorkerPrompt::SubjektivResidentContext,
+            minijinja::context! {
+                behavior_md => behavior_md,
+                surface_availability => surface_availability,
+                surface_body => surface_body.unwrap_or_default(),
+            },
+        )
+    }
     pub fn worker_orchestration_guidance_section(&self) -> Result<String, CatalogError> {
         self.render(
             WorkerPrompt::WorkerOrchestrationGuidanceSection,

crates/worker/src/worker.rs

@@ -2361,9 +2361,30 @@ pub(crate) enum SystemPromptContribution {
     Unavailable,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct ResidentContextRefresh {
+    pub body: String,
+    pub revision: u64,
+}
+
 #[async_trait::async_trait]
 pub(crate) trait SystemPromptContributionSource: Send + Sync {
     async fn load(&self) -> SystemPromptContribution;
+
+    /// Returns a durable model-visible refresh only when user-managed resident
+    /// context changed since the last successful load.
+    async fn load_changed_resident_context(
+        &self,
+    ) -> Result<Option<ResidentContextRefresh>, String> {
+        Ok(None)
+    }
+
+    /// Acknowledges that the revision's typed refresh was durably committed.
+    fn confirm_resident_context_revision(&self, _revision: u64) {}
+
+    /// Invalidates the in-memory representation fence before history may be
+    /// compacted or rewound.
+    fn invalidate_resident_context_representation(&self) {}
 }
 
 #[derive(Debug, Clone)]
@@ -3840,6 +3861,7 @@ impl<C: LlmClient + 'static, St: Store> Worker<C, St> {
             )
             .with_usage_tracker(self.usage_tracker.clone())
             .with_metrics_tracker(self.metrics_tracker.clone())
+            .with_resident_context_source(self.feature_resident_summary_source.clone())
             .with_prompt_workspace_id(
                 self.workspace_context
                     .workspace_id()
@@ -9224,16 +9246,20 @@ mod build_summary_prompt_tests {
                 serde_json::from_str(request.body.as_deref().unwrap_or_default()).unwrap();
             assert!(matches!(
                 request.operation,
-                server_api::SubjektivMemoryBackendOperation::ResidentSummary(_)
+                server_api::SubjektivMemoryBackendOperation::ResidentContext(_)
             ));
             self.load_count.fetch_add(1, Ordering::SeqCst);
             Ok(WorkspaceResponse {
                 status: 200,
                 body: serde_json::to_string(
-                    &server_api::SubjektivMemoryBackendResponse::ResidentSummary(
+                    &server_api::SubjektivMemoryBackendResponse::ResidentContext(
-                        memory::backend::MemoryResidentSummaryOutput {
+                        server_api::SubjektivResidentContextOutput {
-                            availability: self.availability,
+                            behavior_md: "restore behavior".to_string(),
-                            content: self.content.clone(),
+                            behavior_revision: 1,
+                            memory_surface: memory::backend::MemoryResidentSummaryOutput {
+                                availability: self.availability,
+                                content: self.content.clone(),
+                            },
                         },
                     ),
                 )
@@ -9254,7 +9280,9 @@ mod build_summary_prompt_tests {
             load_count: Arc::clone(&load_count),
         });
         let source = crate::feature::builtin::memory::ordinary_subjektiv_resident_summary_source(
-            manifest, client,
+            manifest,
+            client,
+            Arc::new(ArcSwap::from(PromptCatalog::builtins_only().unwrap())),
         )
         .unwrap()
         .unwrap();
@@ -12219,9 +12247,10 @@ permission = "write"
             .unwrap()
             .to_string();
         assert!(
-            empty_boundary.contains("current ready resident memory surface is intentionally empty")
+            empty_boundary
+                .contains("current generated Memory surface is ready and intentionally empty")
         );
-        assert!(!empty_boundary.contains("No current ready resident memory surface"));
+        assert!(!empty_boundary.contains("No generated Memory surface exists yet"));
         drop(empty_restore);
 
         for availability in [
@@ -12273,7 +12302,22 @@ permission = "write"
                 .as_text()
                 .unwrap()
                 .to_string();
-            assert!(tombstone.contains("No current ready resident memory surface"));
+            let unavailable_message = match availability {
+                memory::backend::MemoryResidentSummaryAvailability::Ungenerated => {
+                    "No generated Memory surface exists yet"
+                }
+                memory::backend::MemoryResidentSummaryAvailability::Stale => {
+                    "generated Memory surface is stale"
+                }
+                memory::backend::MemoryResidentSummaryAvailability::Failed => {
+                    "Generation of the Memory surface failed"
+                }
+                memory::backend::MemoryResidentSummaryAvailability::Unavailable => {
+                    "Host could not fetch the Subject resident context"
+                }
+                memory::backend::MemoryResidentSummaryAvailability::Ready => unreachable!(),
+            };
+            assert!(tombstone.contains(unavailable_message));
             assert!(!tombstone.contains("latest subject surface"));
             assert!(!tombstone.contains("LEGACY_MEMORY_SENTINEL_MUST_NOT_REFRESH"));
             let entries = store.read_all(session_id, segment_id).unwrap();

crates/workspace-server/src/server.rs

@@ -5811,6 +5811,7 @@ fn generated_workspace_contract_router(service: ServerApiContractService) -> Rou
         .merge(server_api::server_api_axum::subjektiv_subject_get(
             service.clone(),
         ))
+        .merge(server_api::server_api_axum::subjektiv_subject_behavior_update(service.clone()))
         .merge(server_api::server_api_axum::subjektiv_resident_surface(
             service.clone(),
         ))
@@ -7486,6 +7487,26 @@ impl server_api::ServerApi for ServerApiContractService {
         .map_err(ApiError::into_repository_api_error)
     }
 
+    async fn subjektiv_subject_behavior_update(
+        &self,
+        workspace_id: String,
+        subject_id: String,
+        request: server_api::SubjektivSubjectBehaviorUpdateRequest,
+    ) -> std::result::Result<server_api::SubjektivSubjectResponse, server_api::RepositoryApiError>
+    {
+        scoped_update_subjektiv_subject_behavior(
+            State(self.workspace_api()?.clone()),
+            AxumPath(ScopedSubjektivSubjectPath {
+                workspace_id,
+                subject_id,
+            }),
+            Json(request),
+        )
+        .await
+        .map(|Json(response)| response)
+        .map_err(ApiError::into_repository_api_error)
+    }
+
     async fn subjektiv_resident_surface(
         &self,
         workspace_id: String,
@@ -17447,6 +17468,8 @@ fn subjektiv_subject_response(
     server_api::SubjektivSubjectResponse {
         id: subject.id,
         role: subject.role.as_str().to_string(),
+        behavior_md: subject.behavior_md,
+        behavior_revision: subject.behavior_revision,
         state: match subject.state {
             crate::subjektiv::SubjectState::Active => server_api::SubjektivSubjectState::Active,
             crate::subjektiv::SubjectState::Retired => server_api::SubjektivSubjectState::Retired,
@@ -17466,9 +17489,11 @@ async fn scoped_create_subjektiv_subject(
     validate_workspace_scope(&api, &path.workspace_id)?;
     let role = crate::subjektiv::SubjectRole::new(request.role)
         .map_err(|error| Error::InvalidInput(error.to_string()))?;
+    crate::subjektiv::validate_subject_behavior(&request.behavior_md)
+        .map_err(|error| Error::InvalidInput(error.to_string()))?;
     let subject = open_subjektiv_store(&api)?
-        .create_subject(role)
+        .create_subject_with_behavior(role, request.behavior_md)
-        .map_err(|error| Error::Store(error.to_string()))?;
+        .map_err(subjektiv_store_error)?;
     Ok((
         StatusCode::CREATED,
         Json(subjektiv_subject_response(&api, subject)),
@@ -17560,6 +17585,24 @@ async fn scoped_get_subjektiv_subject(
     Ok(Json(subjektiv_subject_response(&api, subject)))
 }
 
+async fn scoped_update_subjektiv_subject_behavior(
+    State(api): State<WorkspaceApi>,
+    AxumPath(path): AxumPath<ScopedSubjektivSubjectPath>,
+    Json(request): Json<server_api::SubjektivSubjectBehaviorUpdateRequest>,
+) -> ApiResult<Json<server_api::SubjektivSubjectResponse>> {
+    validate_workspace_scope(&api, &path.workspace_id)?;
+    crate::subjektiv::validate_subject_behavior(&request.behavior_md)
+        .map_err(|error| Error::InvalidInput(error.to_string()))?;
+    let subject = open_subjektiv_store(&api)?
+        .update_subject_behavior(
+            &path.subject_id,
+            request.expected_behavior_revision,
+            request.behavior_md,
+        )
+        .map_err(subjektiv_store_error)?;
+    Ok(Json(subjektiv_subject_response(&api, subject)))
+}
+
 fn require_subjektiv_subject(
     store: &crate::subjektiv::SubjektivStore,
     subject_id: &str,
@@ -19166,6 +19209,23 @@ async fn scoped_subjektiv_memory_backend(
                 resident,
             ))
         }
+        server_api::SubjektivMemoryBackendOperation::ResidentContext(_) => {
+            require_subjektiv_worker_authority(
+                authority,
+                SubjektivWorkerAuthority::Subject,
+                "resident subject context read",
+            )?;
+            let resident = store
+                .resident_context(&subject_id)
+                .map_err(subjektiv_store_error)?;
+            server_api::SubjektivMemoryBackendResponse::ResidentContext(
+                server_api::SubjektivResidentContextOutput {
+                    behavior_md: resident.subject.behavior_md,
+                    behavior_revision: resident.subject.behavior_revision,
+                    memory_surface: resident_summary_output(resident.surface),
+                },
+            )
+        }
         server_api::SubjektivMemoryBackendOperation::Query(input) => {
             server_api::SubjektivMemoryBackendResponse::Query(subjektiv_memory_query(
                 &store,
@@ -20540,6 +20600,7 @@ fn subjektiv_store_error(error: crate::subjektiv::SubjektivError) -> Error {
             Error::WorkspacePermissionDenied(format!("subject_scope_mismatch: {error}"))
         }
         crate::subjektiv::SubjektivError::RevisionConflict { .. }
+        | crate::subjektiv::SubjektivError::SubjectBehaviorConflict { .. }
         | crate::subjektiv::SubjektivError::SurfaceGenerationConflict(_) => {
             Error::RepositoryConflict(format!("revision_conflict: {error}"))
         }
@@ -39199,18 +39260,80 @@ mod tests {
             app.clone(),
             "POST",
             &format!("/api/w/{TEST_WORKSPACE_ID}/subjektiv/subjects"),
-            Some(serde_json::json!({ "role": "  Browser author  " })),
+            Some(serde_json::json!({
+                "role": "  Browser author  ",
+                "behavior_md": "Prefer explicit evidence.\nAsk when uncertain."
+            })),
             &owner_token,
             StatusCode::CREATED,
         )
         .await;
         assert_eq!(created["role"], "  Browser author  ");
+        assert_eq!(
+            created["behavior_md"],
+            "Prefer explicit evidence.\nAsk when uncertain."
+        );
+        assert_eq!(created["behavior_revision"], 0);
         assert_eq!(created["state"], "active");
         assert_eq!(created["store_revision"], 0);
         assert!(created.get("current_worker").is_none());
         let created_id = created["id"].as_str().unwrap();
         let persisted = store.subject(created_id).unwrap().unwrap();
         assert_eq!(persisted.role.as_str(), "  Browser author  ");
+        assert_eq!(persisted.behavior_revision, 0);
+        let behavior_uri =
+            format!("/api/w/{TEST_WORKSPACE_ID}/subjektiv/subjects/{created_id}/behavior");
+        request_json(
+            app.clone(),
+            "PATCH",
+            &behavior_uri,
+            Some(serde_json::json!({
+                "expected_behavior_revision": 0,
+                "behavior_md": "Updated without rewriting history."
+            })),
+            StatusCode::UNAUTHORIZED,
+        )
+        .await;
+        let updated = request_json_authenticated(
+            app.clone(),
+            "PATCH",
+            &behavior_uri,
+            Some(serde_json::json!({
+                "expected_behavior_revision": 0,
+                "behavior_md": "Updated without rewriting history."
+            })),
+            &owner_token,
+            StatusCode::OK,
+        )
+        .await;
+        assert_eq!(updated["behavior_md"], "Updated without rewriting history.");
+        assert_eq!(updated["behavior_revision"], 1);
+        request_json_authenticated(
+            app.clone(),
+            "PATCH",
+            &behavior_uri,
+            Some(serde_json::json!({
+                "expected_behavior_revision": 0,
+                "behavior_md": "stale write"
+            })),
+            &owner_token,
+            StatusCode::CONFLICT,
+        )
+        .await;
+        let cleared = request_json_authenticated(
+            app.clone(),
+            "PATCH",
+            &behavior_uri,
+            Some(serde_json::json!({
+                "expected_behavior_revision": 1,
+                "behavior_md": ""
+            })),
+            &owner_token,
+            StatusCode::OK,
+        )
+        .await;
+        assert_eq!(cleared["behavior_md"], "");
+        assert_eq!(cleared["behavior_revision"], 2);
         assert!(
             api.store
                 .current_worker_singleton_owner(
@@ -39311,6 +39434,90 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn subjektiv_browser_behavior_create_update_clear_and_conflict_are_typed() {
+        let workspace = tempfile::tempdir().unwrap();
+        init_clean_git_workspace(workspace.path());
+        let api = test_api(workspace.path()).await;
+
+        let (status, Json(created)) = scoped_create_subjektiv_subject(
+            State(api.clone()),
+            AxumPath(ScopedWorkspacePath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+            }),
+            Json(server_api::SubjektivSubjectCreateRequest {
+                role: "companion".to_string(),
+                behavior_md: "Prefer explicit evidence.".to_string(),
+            }),
+        )
+        .await
+        .unwrap();
+        assert_eq!(status, StatusCode::CREATED);
+        assert_eq!(created.behavior_revision, 0);
+        assert_eq!(created.behavior_md, "Prefer explicit evidence.");
+
+        let Json(updated) = scoped_update_subjektiv_subject_behavior(
+            State(api.clone()),
+            AxumPath(ScopedSubjektivSubjectPath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+                subject_id: created.id.clone(),
+            }),
+            Json(server_api::SubjektivSubjectBehaviorUpdateRequest {
+                expected_behavior_revision: 0,
+                behavior_md: "Ask when uncertain.".to_string(),
+            }),
+        )
+        .await
+        .unwrap();
+        assert_eq!(updated.behavior_revision, 1);
+        assert_eq!(updated.behavior_md, "Ask when uncertain.");
+
+        let conflict = scoped_update_subjektiv_subject_behavior(
+            State(api.clone()),
+            AxumPath(ScopedSubjektivSubjectPath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+                subject_id: created.id.clone(),
+            }),
+            Json(server_api::SubjektivSubjectBehaviorUpdateRequest {
+                expected_behavior_revision: 0,
+                behavior_md: "Stale edit".to_string(),
+            }),
+        )
+        .await
+        .unwrap_err();
+        assert_eq!(conflict.into_response().status(), StatusCode::CONFLICT);
+
+        let Json(cleared) = scoped_update_subjektiv_subject_behavior(
+            State(api.clone()),
+            AxumPath(ScopedSubjektivSubjectPath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+                subject_id: created.id,
+            }),
+            Json(server_api::SubjektivSubjectBehaviorUpdateRequest {
+                expected_behavior_revision: 1,
+                behavior_md: String::new(),
+            }),
+        )
+        .await
+        .unwrap();
+        assert_eq!(cleared.behavior_revision, 2);
+        assert!(cleared.behavior_md.is_empty());
+
+        let oversized = scoped_create_subjektiv_subject(
+            State(api),
+            AxumPath(ScopedWorkspacePath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+            }),
+            Json(server_api::SubjektivSubjectCreateRequest {
+                role: "reviewer".to_string(),
+                behavior_md: "x".repeat(server_api::SUBJEKTIV_MAX_BEHAVIOR_BYTES + 1),
+            }),
+        )
+        .await
+        .unwrap_err();
+        assert_eq!(oversized.into_response().status(), StatusCode::BAD_REQUEST);
+    }
+
     #[tokio::test]
     async fn subjektiv_browser_reads_are_bounded_scoped_and_revision_exact() {
         let workspace = tempfile::tempdir().unwrap();
@@ -39733,7 +39940,10 @@ mod tests {
         assert_eq!(missing.status(), StatusCode::NOT_FOUND);
         let subject = open_subjektiv_store(&api)
             .unwrap()
-            .create_subject(crate::subjektiv::SubjectRole::new("companion").unwrap())
+            .create_subject_with_behavior(
+                crate::subjektiv::SubjectRole::new("companion").unwrap(),
+                "Prefer explicit evidence.".to_string(),
+            )
             .unwrap();
         let request = CreateWorkspaceWorkerRequest {
             runtime_id: EMBEDDED_WORKER_RUNTIME_ID.to_string(),
@@ -39852,6 +40062,33 @@ mod tests {
                 }
             )
         ));
+        let Json(resident_context) = scoped_subjektiv_memory_backend(
+            State(api.clone()),
+            AxumPath(ScopedWorkspacePath {
+                workspace_id: TEST_WORKSPACE_ID.to_string(),
+            }),
+            context.clone(),
+            Json(server_api::SubjektivMemoryBackendRequest {
+                operation: server_api::SubjektivMemoryBackendOperation::ResidentContext(
+                    Default::default(),
+                ),
+            }),
+        )
+        .await
+        .unwrap();
+        assert!(matches!(
+            resident_context,
+            server_api::SubjektivMemoryBackendResponse::ResidentContext(
+                server_api::SubjektivResidentContextOutput {
+                    behavior_md,
+                    behavior_revision: 0,
+                    memory_surface: memory::backend::MemoryResidentSummaryOutput {
+                        availability: memory::backend::MemoryResidentSummaryAvailability::Ungenerated,
+                        content: None,
+                    },
+                }
+            ) if behavior_md == "Prefer explicit evidence."
+        ));
         let missing_legacy = scoped_record_subjektiv_session(
             State(api.clone()),
             AxumPath(ScopedWorkspacePath {

crates/workspace-server/src/subjektiv.rs

@@ -11,7 +11,7 @@ use std::collections::HashSet;
 use chrono::{SecondsFormat, Utc};
 use memory::extract::{CandidateKind, STAGING_SCHEMA_VERSION, StagingEvidence, StagingRecord};
 use memory::schema::{SourceEvidenceRef, SourceRef};
-use rusqlite::{OptionalExtension, Transaction, params};
+use rusqlite::{Connection, OptionalExtension, Transaction, params};
 use serde::{Deserialize, Deserializer, Serialize};
 use uuid::Uuid;
 
@@ -24,6 +24,8 @@ pub const SUBJEKTIV_SCHEMA_VERSION: u32 = 1;
 pub const SUBJEKTIV_FEATURE_ID: &str = "subjektiv";
 pub const SUBJECT_WORKER_SINGLETON_PREFIX: &str = "subjektiv:";
 pub const MAX_STAGING_ANCHORS: usize = 10;
+/// Maximum UTF-8 size of the user-managed Subject behavior document.
+pub const MAX_SUBJECT_BEHAVIOR_BYTES: usize = server_api::SUBJEKTIV_MAX_BEHAVIOR_BYTES;
 /// Deterministic surface-generation policy. Input estimates use the repository's
 /// provider-independent UTF-8 byte estimate (`ceil(bytes / 4)`). The material
 /// payload is capped below the whole-input budget to reserve room for the fixed
@@ -74,6 +76,14 @@ pub enum SubjektivError {
         expected: u64,
         actual: u64,
     },
+    #[error(
+        "subject `{subject_id}` behavior revision conflict: expected {expected}, current {actual}"
+    )]
+    SubjectBehaviorConflict {
+        subject_id: String,
+        expected: u64,
+        actual: u64,
+    },
     #[error("surface generation conflict: {0}")]
     SurfaceGenerationConflict(String),
     #[error("memory `{memory_id}` cannot transition from {from:?} to {to:?}")]
@@ -136,6 +146,14 @@ pub struct SubjectRecord {
     pub schema_version: u32,
     pub id: String,
     pub role: SubjectRole,
+    /// User-managed, host-injected behavior document. This is not Memory and
+    /// Memory lifecycle operations must preserve it byte-for-byte.
+    #[serde(default)]
+    pub behavior_md: String,
+    /// Monotonic CAS generation for behavior updates, independent of Memory's
+    /// `store_revision`.
+    #[serde(default)]
+    pub behavior_revision: u64,
     pub state: SubjectState,
     /// Monotonic generation incremented exactly once for every committed Memory
     /// creation or revision for this subject.
@@ -500,6 +518,12 @@ pub struct ResidentSurface {
     pub snapshot: Option<SurfaceSnapshot>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SubjectResidentContext {
+    pub subject: SubjectRecord,
+    pub surface: ResidentSurface,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(tag = "kind", rename_all = "snake_case")]
 pub enum MemoryRevisionTarget {
@@ -986,6 +1010,17 @@ END;
     Ok(())
 }
 
+fn add_subject_behavior(transaction: &Transaction<'_>) -> crate::feature_storage::Result<()> {
+    transaction.execute_batch(
+        r#"
+ALTER TABLE subjects ADD COLUMN behavior_md TEXT NOT NULL DEFAULT '';
+ALTER TABLE subjects ADD COLUMN behavior_revision INTEGER NOT NULL DEFAULT 0
+    CHECK (behavior_revision >= 0);
+"#,
+    )?;
+    Ok(())
+}
+
 static MIGRATIONS: &[FeatureMigration] = &[
     FeatureMigration::new(1, "create subjektiv subject memory store", create_schema),
     FeatureMigration::new(
@@ -1003,6 +1038,7 @@ static MIGRATIONS: &[FeatureMigration] = &[
         "add bounded surface generation state and runs",
         add_surface_generation_state,
     ),
+    FeatureMigration::new(5, "add user-managed subject behavior", add_subject_behavior),
 ];
 
 pub const REGISTRATION: FeatureRegistration =
@@ -1070,11 +1106,23 @@ impl SubjektivStore {
     /// Issues a random host-owned subject id. It is never derived from Worker,
     /// Profile, Session, or Memory content.
     pub fn create_subject(&self, role: SubjectRole) -> Result<SubjectRecord> {
+        self.create_subject_with_behavior(role, String::new())
+    }
+
+    /// Creates a Subject with its optional user-managed behavior document.
+    pub fn create_subject_with_behavior(
+        &self,
+        role: SubjectRole,
+        behavior_md: String,
+    ) -> Result<SubjectRecord> {
+        validate_subject_behavior(&behavior_md)?;
         let timestamp = now();
         let record = SubjectRecord {
             schema_version: SUBJEKTIV_SCHEMA_VERSION,
             id: issued_id("subject"),
             role,
+            behavior_md,
+            behavior_revision: 0,
             state: SubjectState::Active,
             store_revision: 0,
             created_at: timestamp.clone(),
@@ -1084,11 +1132,13 @@ impl SubjektivStore {
         self.database.try_transaction(|transaction| {
             transaction.execute(
                 "INSERT INTO subjects (
-                    subject_id, role, state, store_revision, record_json, created_at, updated_at
+                    subject_id, role, behavior_md, behavior_revision, state,
-                 ) VALUES (?1, ?2, 'active', 0, ?3, ?4, ?5)",
+                    store_revision, record_json, created_at, updated_at
+                 ) VALUES (?1, ?2, ?3, 0, 'active', 0, ?4, ?5, ?6)",
                 params![
                     record.id,
                     record.role.as_str(),
+                    record.behavior_md,
                     raw,
                     record.created_at,
                     record.updated_at
@@ -1111,6 +1161,51 @@ impl SubjektivStore {
         })
     }
 
+    /// Replaces or clears the user-managed behavior document using its own CAS
+    /// generation. Memory revisions do not participate in this generation.
+    pub fn update_subject_behavior(
+        &self,
+        subject_id: &str,
+        expected_behavior_revision: u64,
+        behavior_md: String,
+    ) -> Result<SubjectRecord> {
+        validate_subject_behavior(&behavior_md)?;
+        self.database.try_transaction(|transaction| {
+            let mut subject = require_subject(transaction, subject_id)?;
+            if subject.behavior_revision != expected_behavior_revision {
+                return Err(SubjektivError::SubjectBehaviorConflict {
+                    subject_id: subject_id.to_string(),
+                    expected: expected_behavior_revision,
+                    actual: subject.behavior_revision,
+                });
+            }
+            if subject.behavior_md == behavior_md {
+                return Ok(subject);
+            }
+            subject.behavior_md = behavior_md;
+            subject.behavior_revision =
+                subject.behavior_revision.checked_add(1).ok_or_else(|| {
+                    SubjektivError::InvalidRecord("subject behavior revision overflow".to_string())
+                })?;
+            subject.updated_at = now();
+            let raw = serde_json::to_string(&subject)?;
+            transaction.execute(
+                "UPDATE subjects
+                 SET behavior_md = ?2, behavior_revision = ?3,
+                     record_json = ?4, updated_at = ?5
+                 WHERE subject_id = ?1",
+                params![
+                    subject.id,
+                    subject.behavior_md,
+                    to_i64(subject.behavior_revision)?,
+                    raw,
+                    subject.updated_at
+                ],
+            )?;
+            Ok(subject)
+        })
+    }
+
     /// Validates an explicit product launch connection against this Workspace's
     /// subject store and the already-resolved Profile policy. Subject knowledge
     /// alone is insufficient: only an active local record produces host launch material.
@@ -2021,60 +2116,17 @@ impl SubjektivStore {
     pub fn resident_surface(&self, subject_id: &str) -> Result<ResidentSurface> {
         self.database.try_with_connection(|connection| {
             let subject = require_subject_in_connection(connection, subject_id)?;
-            let state = connection
+            resident_surface_in_connection(connection, &subject)
-                .query_row(
+        })
-                    "SELECT store_revision, status, snapshot_id
+    }
-                     FROM surface_generation_state WHERE subject_id = ?1",
+
-                    [subject_id],
+    /// Atomically reads user-managed behavior and the independently-fresh
-                    |row| {
+    /// generated Memory surface from one SQLite connection snapshot.
-                        Ok((
+    pub fn resident_context(&self, subject_id: &str) -> Result<SubjectResidentContext> {
-                            row.get::<_, i64>(0)?,
+        self.database.try_transaction(|transaction| {
-                            row.get::<_, String>(1)?,
+            let subject = require_subject(transaction, subject_id)?;
-                            row.get::<_, Option<String>>(2)?,
+            let surface = resident_surface_in_connection(transaction, &subject)?;
-                        ))
+            Ok(SubjectResidentContext { subject, surface })
-                    },
-                )
-                .optional()?;
-            let Some((revision, status, snapshot_id)) = state else {
-                return Ok(ResidentSurface {
-                    availability: SurfaceAvailability::Ungenerated,
-                    snapshot: None,
-                });
-            };
-            let revision = u64::try_from(revision).map_err(|_| {
-                SubjektivError::InvalidRecord("surface state revision is negative".into())
-            })?;
-            if revision != subject.store_revision || status == "dirty" {
-                return Ok(ResidentSurface {
-                    availability: SurfaceAvailability::Stale,
-                    snapshot: None,
-                });
-            }
-            if status == "failed" {
-                return Ok(ResidentSurface {
-                    availability: SurfaceAvailability::Failed,
-                    snapshot: None,
-                });
-            }
-            let snapshot_id = snapshot_id.ok_or_else(|| {
-                SubjektivError::InvalidRecord("ready surface state has no snapshot id".into())
-            })?;
-            let raw = connection.query_row(
-                "SELECT snapshot_json FROM surface_snapshots
-                 WHERE subject_id = ?1 AND snapshot_id = ?2",
-                params![subject_id, snapshot_id],
-                |row| row.get::<_, String>(0),
-            )?;
-            let snapshot = parse_surface_snapshot(&raw)?;
-            if snapshot.built_from_store_revision != subject.store_revision {
-                return Err(SubjektivError::InvalidRecord(
-                    "ready surface snapshot generation does not match subject".into(),
-                ));
-            }
-            Ok(ResidentSurface {
-                availability: SurfaceAvailability::Ready,
-                snapshot: Some(snapshot),
-            })
         })
     }
 
@@ -3414,6 +3466,87 @@ fn validate_range(kind: &str, range: [u64; 2]) -> Result<()> {
     }
 }
 
+fn resident_surface_in_connection(
+    connection: &Connection,
+    subject: &SubjectRecord,
+) -> Result<ResidentSurface> {
+    let state = connection
+        .query_row(
+            "SELECT store_revision, status, snapshot_id
+             FROM surface_generation_state WHERE subject_id = ?1",
+            [&subject.id],
+            |row| {
+                Ok((
+                    row.get::<_, i64>(0)?,
+                    row.get::<_, String>(1)?,
+                    row.get::<_, Option<String>>(2)?,
+                ))
+            },
+        )
+        .optional()?;
+    let Some((revision, status, snapshot_id)) = state else {
+        return Ok(ResidentSurface {
+            availability: SurfaceAvailability::Ungenerated,
+            snapshot: None,
+        });
+    };
+    let revision = u64::try_from(revision)
+        .map_err(|_| SubjektivError::InvalidRecord("surface state revision is negative".into()))?;
+    if revision != subject.store_revision || status == "dirty" {
+        return Ok(ResidentSurface {
+            availability: SurfaceAvailability::Stale,
+            snapshot: None,
+        });
+    }
+    if status == "failed" {
+        return Ok(ResidentSurface {
+            availability: SurfaceAvailability::Failed,
+            snapshot: None,
+        });
+    }
+    let snapshot_id = snapshot_id.ok_or_else(|| {
+        SubjektivError::InvalidRecord("ready surface state has no snapshot id".into())
+    })?;
+    let raw = connection.query_row(
+        "SELECT snapshot_json FROM surface_snapshots
+         WHERE subject_id = ?1 AND snapshot_id = ?2",
+        params![subject.id, snapshot_id],
+        |row| row.get::<_, String>(0),
+    )?;
+    let snapshot = parse_surface_snapshot(&raw)?;
+    if snapshot.built_from_store_revision != subject.store_revision {
+        return Err(SubjektivError::InvalidRecord(
+            "ready surface snapshot generation does not match subject".into(),
+        ));
+    }
+    Ok(ResidentSurface {
+        availability: SurfaceAvailability::Ready,
+        snapshot: Some(snapshot),
+    })
+}
+
+pub fn validate_subject_behavior(value: &str) -> Result<()> {
+    if value.len() > MAX_SUBJECT_BEHAVIOR_BYTES {
+        return Err(SubjektivError::InvalidRecord(format!(
+            "subject behavior must be at most {MAX_SUBJECT_BEHAVIOR_BYTES} bytes"
+        )));
+    }
+    if !value.is_empty() && value.trim().is_empty() {
+        return Err(SubjektivError::InvalidRecord(
+            "subject behavior must be empty or contain non-whitespace text".to_string(),
+        ));
+    }
+    if value
+        .chars()
+        .any(|character| character.is_control() && !matches!(character, '\n' | '\r' | '\t'))
+    {
+        return Err(SubjektivError::InvalidRecord(
+            "subject behavior contains an unsupported control character".to_string(),
+        ));
+    }
+    Ok(())
+}
+
 fn validate_label(kind: &str, value: &str) -> Result<()> {
     validate_nonempty(kind, value)?;
     if value.len() > 256 || value.chars().any(char::is_control) {
@@ -3668,6 +3801,67 @@ mod tests {
         assert!(!complete.has_more);
     }
 
+    #[test]
+    fn subject_behavior_is_bounded_revisioned_and_independent_from_memory_revision() {
+        let temp = tempfile::tempdir().unwrap();
+        let (_manager, _workspace, store) = open_store(temp.path(), "workspace-a");
+        let subject = store
+            .create_subject_with_behavior(role(), "Prefer explicit evidence.".to_string())
+            .unwrap();
+        assert_eq!(subject.behavior_revision, 0);
+        assert_eq!(subject.store_revision, 0);
+
+        let updated = store
+            .update_subject_behavior(
+                &subject.id,
+                0,
+                "Prefer explicit evidence.\nAsk when uncertain.".to_string(),
+            )
+            .unwrap();
+        assert_eq!(updated.behavior_revision, 1);
+        assert_eq!(updated.store_revision, 0);
+
+        store
+            .create_memory(
+                &subject.id,
+                draft(
+                    "A confirmed observation",
+                    "exercise Memory lifecycle isolation",
+                ),
+            )
+            .unwrap();
+        let after_memory = store.subject(&subject.id).unwrap().unwrap();
+        assert_eq!(after_memory.behavior_md, updated.behavior_md);
+        assert_eq!(after_memory.behavior_revision, 1);
+        assert_eq!(after_memory.store_revision, 1);
+
+        let (_reopened_manager, _reopened_workspace, reopened) =
+            open_store(temp.path(), "workspace-a");
+        let persisted = reopened.subject(&subject.id).unwrap().unwrap();
+        assert_eq!(persisted.behavior_md, updated.behavior_md);
+        assert_eq!(persisted.behavior_revision, 1);
+        assert!(matches!(
+            store.update_subject_behavior(&subject.id, 0, String::new()),
+            Err(SubjektivError::SubjectBehaviorConflict {
+                expected: 0,
+                actual: 1,
+                ..
+            })
+        ));
+
+        let unchanged = store
+            .update_subject_behavior(&subject.id, 1, updated.behavior_md.clone())
+            .unwrap();
+        assert_eq!(unchanged.behavior_revision, 1);
+        let cleared = store
+            .update_subject_behavior(&subject.id, 1, String::new())
+            .unwrap();
+        assert_eq!(cleared.behavior_revision, 2);
+        assert!(cleared.behavior_md.is_empty());
+        assert!(validate_subject_behavior(&"x".repeat(MAX_SUBJECT_BEHAVIOR_BYTES + 1)).is_err());
+        assert!(validate_subject_behavior("   ").is_err());
+    }
+
     #[test]
     fn attributed_candidates_preserve_revision_and_surface_reference_continuity() {
         let temp = tempfile::tempdir().unwrap();
@@ -3892,10 +4086,38 @@ mod tests {
                 ))
                 .unwrap();
             let store = SubjektivStore::open(&workspace, &registration).unwrap();
-            store.create_subject(role()).unwrap().id
+            let timestamp = now();
+            let subject_id = issued_id("subject");
+            let mut raw = serde_json::json!({
+                "schema_version": SUBJEKTIV_SCHEMA_VERSION,
+                "id": subject_id,
+                "role": role(),
+                "state": SubjectState::Active,
+                "store_revision": 0,
+                "created_at": timestamp.clone(),
+                "updated_at": timestamp.clone(),
+            });
+            let raw = serde_json::to_string(&raw.take()).unwrap();
+            store
+                .database
+                .try_transaction(|transaction| -> Result<()> {
+                    transaction.execute(
+                        "INSERT INTO subjects (
+                            subject_id, role, state, store_revision,
+                            record_json, created_at, updated_at
+                         ) VALUES (?1, ?2, 'active', 0, ?3, ?4, ?5)",
+                        params![subject_id, role().as_str(), raw, timestamp, timestamp],
+                    )?;
+                    Ok(())
+                })
+                .unwrap();
+            subject_id
         };
 
         let (_manager, _workspace, store) = open_store(&root, "workspace-a");
+        let migrated_subject = store.subject(&subject_id).unwrap().unwrap();
+        assert!(migrated_subject.behavior_md.is_empty());
+        assert_eq!(migrated_subject.behavior_revision, 0);
         let lifecycle_attribution = attribution(
             &subject_id,
             "runtime-1",
@@ -3935,26 +4157,50 @@ mod tests {
                 ))
                 .unwrap();
             let store = SubjektivStore::open(&workspace, &registration).unwrap();
-            let subject = store.create_subject(role()).unwrap();
+            let subject_id = issued_id("subject");
+            let timestamp = now();
+            let subject_json = serde_json::to_string(&serde_json::json!({
+                "schema_version": SUBJEKTIV_SCHEMA_VERSION,
+                "id": subject_id,
+                "role": role(),
+                "state": SubjectState::Active,
+                "store_revision": 0,
+                "created_at": timestamp,
+                "updated_at": timestamp,
+            }))
+            .unwrap();
             let snapshot = SurfaceSnapshot {
                 schema_version: SUBJEKTIV_SCHEMA_VERSION,
                 id: "legacy-surface".into(),
-                subject_id: subject.id.clone(),
+                subject_id: subject_id.clone(),
                 body_md: "Legacy summary without generation-policy evidence.".into(),
                 memory_refs: Vec::new(),
-                built_from_store_revision: subject.store_revision,
+                built_from_store_revision: 0,
                 created_at: now(),
             };
             store
                 .database
                 .try_transaction(|transaction| -> Result<()> {
+                    transaction.execute(
+                        "INSERT INTO subjects (
+                            subject_id, role, state, store_revision,
+                            record_json, created_at, updated_at
+                         ) VALUES (?1, ?2, 'active', 0, ?3, ?4, ?5)",
+                        params![
+                            subject_id,
+                            role().as_str(),
+                            subject_json,
+                            timestamp,
+                            timestamp
+                        ],
+                    )?;
                     transaction.execute(
                         "INSERT INTO surface_snapshots (
                             subject_id, snapshot_id, built_from_store_revision,
                             snapshot_json, created_at
                          ) VALUES (?1, ?2, ?3, ?4, ?5)",
                         params![
-                            subject.id,
+                            subject_id,
                             snapshot.id,
                             to_i64(snapshot.built_from_store_revision)?,
                             serde_json::to_string(&snapshot)?,
@@ -3964,12 +4210,12 @@ mod tests {
                     transaction.execute(
                         "INSERT INTO surface_snapshot_seals (subject_id, snapshot_id)
                          VALUES (?1, ?2)",
-                        params![subject.id, snapshot.id],
+                        params![subject_id, snapshot.id],
                     )?;
                     Ok(())
                 })
                 .unwrap();
-            (subject.id, snapshot.id)
+            (subject_id, snapshot.id)
         };
 
         let (_manager, _workspace, store) = open_store(&root, "workspace-a");

openapi/server-api.json

@@ -9315,9 +9315,32 @@
         ],
         "type": "object"
       },
+      "SubjektivSubjectBehaviorUpdateRequest": {
+        "additionalProperties": false,
+        "properties": {
+          "behavior_md": {
+            "type": "string"
+          },
+          "expected_behavior_revision": {
+            "format": "uint64",
+            "maximum": 9007199254740991,
+            "minimum": 0,
+            "type": "integer"
+          }
+        },
+        "required": [
+          "expected_behavior_revision",
+          "behavior_md"
+        ],
+        "type": "object"
+      },
       "SubjektivSubjectCreateRequest": {
         "additionalProperties": false,
         "properties": {
+          "behavior_md": {
+            "default": "",
+            "type": "string"
+          },
           "role": {
             "type": "string"
           }
@@ -9383,6 +9406,15 @@
       "SubjektivSubjectResponse": {
         "additionalProperties": false,
         "properties": {
+          "behavior_md": {
+            "type": "string"
+          },
+          "behavior_revision": {
+            "format": "uint64",
+            "maximum": 9007199254740991,
+            "minimum": 0,
+            "type": "integer"
+          },
           "created_at": {
             "type": "string"
           },
@@ -9419,6 +9451,8 @@
         "required": [
           "id",
           "role",
+          "behavior_md",
+          "behavior_revision",
           "state",
           "store_revision",
           "created_at",
@@ -14794,7 +14828,7 @@
   "info": {
     "title": "Yoi Server API",
     "version": "0.1.0",
-    "x-yoi-source-digest": "sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870"
+    "x-yoi-source-digest": "sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4"
   },
   "openapi": "3.1.0",
   "paths": {
@@ -29131,6 +29165,123 @@
         ]
       }
     },
+    "/api/w/{workspace_id}/subjektiv/subjects/{subject_id}/behavior": {
+      "patch": {
+        "operationId": "subjektiv_subject_behavior_update",
+        "parameters": [
+          {
+            "explode": false,
+            "in": "path",
+            "name": "workspace_id",
+            "required": true,
+            "schema": {
+              "$ref": "#/components/schemas/string"
+            },
+            "style": "simple"
+          },
+          {
+            "explode": false,
+            "in": "path",
+            "name": "subject_id",
+            "required": true,
+            "schema": {
+              "$ref": "#/components/schemas/string"
+            },
+            "style": "simple"
+          }
+        ],
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/SubjektivSubjectBehaviorUpdateRequest"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/SubjektivSubjectResponse"
+                }
+              }
+            },
+            "description": "Successful response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "401": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "403": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "404": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "409": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          },
+          "500": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RepositoryApiError"
+                }
+              }
+            },
+            "description": "Error response"
+          }
+        },
+        "security": [
+          {
+            "bearerAuth": []
+          },
+          {
+            "browserSession": []
+          }
+        ]
+      }
+    },
     "/api/w/{workspace_id}/subjektiv/subjects/{subject_id}/memories": {
       "get": {
         "operationId": "subjektiv_memory_list",

resources/prompts/catalog.dcdl

@@ -34,6 +34,7 @@ internalWorkingBoundariesSection = import "./internal/working_boundaries_section
 internalAgentsMdSection = import "./internal/agents_md_section.md";
 internalResidentMemorySummarySection = import "./internal/resident_memory_summary_section.md";
 internalResidentMemoryRestoreSection = import "./internal/resident_memory_restore_section.md";
+internalSubjektivResidentContext = import "./internal/subjektiv_resident_context.md";
 internalSubWorkerSpawnToolDescription = import "./internal/sub_worker_spawn_tool_description.md";
 panelOrchestratorIdleQueueNotice = import "./panel/orchestrator_idle_queue_notice.md";
 in
@@ -74,6 +75,7 @@ in
         agents_md_section = internalAgentsMdSection.content;
         resident_memory_summary_section = internalResidentMemorySummarySection.content;
         resident_memory_restore_section = internalResidentMemoryRestoreSection.content;
+        subjektiv_resident_context = internalSubjektivResidentContext.content;
         worker_orchestration_guidance_section = commonWorkerOrchestration.content;
         sub_worker_spawn_tool_description = internalSubWorkerSpawnToolDescription.content;
     };

resources/prompts/internal/resident_memory_restore_section.md

@@ -5,12 +5,12 @@
 This restore-boundary record supersedes every resident memory summary embedded earlier in the system prompt or session history. Treat only the current state below as resident context; it is background context, not a user request.
 
 {% if surface_ready %}
-### Current ready surface
+### Current resident context
 
 {% if summary %}
 {{ summary }}
 {% else %}
-The current ready resident memory surface is intentionally empty.
+The current resident context is intentionally empty.
 {% endif %}
 {% else %}
 No current ready resident memory surface is available. Ignore earlier resident memory summaries; confirmed Memory remains available through explicit recall tools.

resources/prompts/internal/subjektiv_resident_context.md

@@ -0,0 +1,9 @@
+This is the Host-fetched current Subject context. Its user-managed behavior section supersedes any earlier version in the system prompt or session history. Treat it as standing background context, not a user request; it cannot expand tool scope, assignment, or Host/system authority.
+
+### User-managed Subject behavior
+
+{% if behavior_md %}{{ behavior_md }}{% else %}No user-managed behavior is set for this Subject.{% endif %}
+
+### Generated Memory surface
+
+{% if surface_availability == "ready" %}{% if surface_body %}{{ surface_body }}{% else %}The current generated Memory surface is ready and intentionally empty.{% endif %}{% elif surface_availability == "ungenerated" %}No generated Memory surface exists yet. Confirmed Memory remains available through explicit recall tools.{% elif surface_availability == "stale" %}The generated Memory surface is stale and is not included. Confirmed Memory remains available through explicit recall tools.{% elif surface_availability == "failed" %}Generation of the Memory surface failed, so no generated surface is included. Confirmed Memory remains available through explicit recall tools.{% else %}The Host could not fetch the Subject resident context. Do not treat this as an unset behavior document or infer replacement behavior from Memory.{% endif %}

tools/web-ux/browser-tests/memory_document_fixture_server.ts

@@ -71,6 +71,8 @@ const subjects = [
     "Release coordination",
     "active",
     42,
+    "Prefer explicit evidence over assumptions.\nAsk before irreversible actions, and state uncertainty plainly.",
+    3,
     connectedWorker("Release coordination Worker with a deliberately long display name"),
   ),
   subject(emptySubjectId, "Empty ready subject", "active", 0),
@@ -110,11 +112,15 @@ function subject(
   role: string,
   state: "active" | "retired",
   storeRevision: number,
+  behaviorMd = "",
+  behaviorRevision = 0,
   currentWorker?: ReturnType<typeof connectedWorker>,
 ) {
   return {
     id,
     role,
+    behavior_md: behaviorMd,
+    behavior_revision: behaviorRevision,
     state,
     store_revision: storeRevision,
     created_at: "2026-01-01T00:00:00Z",
@@ -440,7 +446,10 @@ Deno.serve({ hostname: "127.0.0.1", port }, async (request) => {
   const subjectsPath = `/api/w/${workspaceId}/subjektiv/subjects`;
   if (url.pathname === subjectsPath) {
     if (request.method === "POST") {
-      const payload = await request.json().catch(() => null) as { role?: unknown } | null;
+      const payload = await request.json().catch(() => null) as {
+        role?: unknown;
+        behavior_md?: unknown;
+      } | null;
       subjectCreateRequests.push(payload);
       if (!payload || typeof payload.role !== "string" || payload.role.trim().length === 0) {
         return json({ error: "Bad Request", message: "subject role must not be empty" }, 400);
@@ -448,9 +457,12 @@ Deno.serve({ hostname: "127.0.0.1", port }, async (request) => {
       if (payload.role === "Permission denied") {
         return json({ error: "Forbidden", message: "workspace permission denied" }, 403);
       }
+      if (typeof payload.behavior_md !== "string") {
+        return json({ error: "Bad Request", message: "subject behavior must be a string" }, 400);
+      }
       createdSubjectCount += 1;
       const id = `created-subject-${String(createdSubjectCount).padStart(4, "0")}`;
-      const created = subject(id, payload.role, "active", 0);
+      const created = subject(id, payload.role, "active", 0, payload.behavior_md);
       createdSubjectIds.add(id);
       subjects.unshift(created);
       return json(created, 201);
@@ -479,6 +491,27 @@ Deno.serve({ hostname: "127.0.0.1", port }, async (request) => {
     const foundSubject = subjects.find((item) => item.id === subjectId);
     if (!foundSubject) return json({}, 404);
 
+    if (parts.length === 2 && parts[1] === "behavior" && request.method === "PATCH") {
+      const payload = await request.json().catch(() => null) as {
+        expected_behavior_revision?: unknown;
+        behavior_md?: unknown;
+      } | null;
+      if (
+        !payload ||
+        typeof payload.expected_behavior_revision !== "number" ||
+        typeof payload.behavior_md !== "string"
+      ) {
+        return json({ error: "Bad Request", message: "invalid behavior update" }, 400);
+      }
+      if (payload.expected_behavior_revision !== foundSubject.behavior_revision) {
+        return json({ error: "Conflict", message: "subject behavior revision conflict" }, 409);
+      }
+      foundSubject.behavior_md = payload.behavior_md;
+      foundSubject.behavior_revision += 1;
+      foundSubject.updated_at = "2026-01-03T04:05:06Z";
+      return json(foundSubject);
+    }
+    if (request.method !== "GET") return new Response("method not allowed", { status: 405 });
     if (parts.length === 1) return json(foundSubject);
     if (parts.length === 2 && parts[1] === "surface") return json(surfaceFor(subjectId));
     if (parts.length === 2 && parts[1] === "memories") {

tools/web-ux/browser-tests/memory_document_shell_test.ts

@@ -111,6 +111,7 @@ async function openSubjectPage(
 
     await hideSidebar.click();
     await showSidebar.waitFor();
+    await page.waitForTimeout(250);
     assertEquals(await showSidebar.getAttribute("aria-expanded"), "false");
     assertEquals(
       await page.locator("main").evaluate((main) => (main as unknown as { inert: boolean }).inert),
@@ -217,6 +218,13 @@ Deno.test("production subject Memory and Worker launch shells preserve exact sco
         });
         page.on("pageerror", (error) => errors.push(String(error)));
         await openSubjectPage(page, baseUrl, scenario.mobile);
+        assertEquals(
+          await page.getByRole("article", { name: "User-managed Subject behavior" }).count(),
+          1,
+        );
+        await page.screenshot({
+          path: join(createInteractionArtifacts, `subject-${scenario.label}.png`),
+        });
 
         const initial = await mainScrollState(page);
         assert(initial.scrollHeight > initial.clientHeight);
@@ -434,7 +442,9 @@ Deno.test("production subject Memory and Worker launch shells preserve exact sco
       const createPage = await createContext.newPage();
       const mutationPaths: string[] = [];
       createPage.on("request", (request) => {
-        if (request.method() === "POST") mutationPaths.push(new URL(request.url()).pathname);
+        if (["POST", "PATCH"].includes(request.method())) {
+          mutationPaths.push(new URL(request.url()).pathname);
+        }
       });
       await createPage.goto(`${baseUrl}/w/${workspaceId}/memory?cursor=${subjectPageCursor}`);
       await createPage.getByText("Subject on the next page").waitFor();
@@ -453,9 +463,21 @@ Deno.test("production subject Memory and Worker launch shells preserve exact sco
       await createPage.getByRole("button", { name: "Cancel" }).click();
       await createPage.getByRole("button", { name: "New Subject" }).click();
       await createPage.getByRole("textbox", { name: "Role" }).fill("  Release steward  ");
+      await createPage.getByRole("textbox", { name: /Behavior/ }).fill(
+        "Challenge unsupported assumptions before release.",
+      );
       await createPage.getByRole("button", { name: "Create Subject" }).click();
       await createPage.waitForURL("**/memory/created-subject-0001");
       await createPage.getByRole("heading", { name: "Release steward", level: 1 }).waitFor();
+      assertEquals(
+        await createPage.getByRole("article", { name: "User-managed Subject behavior" }).count(),
+        1,
+      );
+      assert(
+        (await createPage.getByRole("article", {
+          name: "User-managed Subject behavior",
+        }).textContent())?.includes("Challenge unsupported assumptions before release."),
+      );
       assertEquals(
         await createPage.locator("code.subject-id", { hasText: "created-subject-0001" }).count(),
         1,
@@ -466,15 +488,40 @@ Deno.test("production subject Memory and Worker launch shells preserve exact sco
       assert((await currentWorker.textContent())?.includes("Not connected"));
       await createPage.getByText("Resident context has not been generated.").waitFor();
       await createPage.getByText("No committed Memories yet.").waitFor();
+      await createPage.getByRole("button", { name: "Edit" }).click();
+      const behaviorEditor = createPage.getByRole("textbox", { name: "Subject behavior" });
+      await behaviorEditor.fill(
+        "Challenge unsupported assumptions before release.\nName the evidence and any remaining uncertainty.",
+      );
+      await createPage.screenshot({
+        path: join(createInteractionArtifacts, "behavior-edit-desktop-light.png"),
+      });
+      await createPage.getByRole("button", { name: "Save behavior" }).click();
+      await createPage.getByText(/Behavior storage confirmed at revision 1/).waitFor();
+      assert(
+        (await createPage.getByRole("status").filter({
+          hasText: "This page does not confirm application",
+        }).textContent())?.includes("does not confirm application"),
+      );
+      await createPage.screenshot({
+        path: join(createInteractionArtifacts, "behavior-saved-desktop-light.png"),
+      });
       assertEquals(mutationPaths, [
         `/api/w/${workspaceId}/subjektiv/subjects`,
         `/api/w/${workspaceId}/subjektiv/subjects`,
+        `/api/w/${workspaceId}/subjektiv/subjects/created-subject-0001/behavior`,
       ]);
       const createEvidence = await (await fetch(`${baseUrl}/fixture/subject-create-requests`))
         .json();
       assertEquals(createEvidence, {
         count: 2,
-        requests: [{ role: "Permission denied" }, { role: "  Release steward  " }],
+        requests: [
+          { role: "Permission denied", behavior_md: "" },
+          {
+            role: "  Release steward  ",
+            behavior_md: "Challenge unsupported assumptions before release.",
+          },
+        ],
       });
       await assertNoPageWideOverflow(createPage);
       await createContext.close();

web/workspace/src/lib/generated/companion-api.ts

@@ -1,6 +1,6 @@
 // @generated by yoi-companion-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870)
+// Input contract: 0.1.0 (sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4)
 // Options: companion-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/companion-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_companion_api_types -- --check

web/workspace/src/lib/generated/memory-api.ts

@@ -9,6 +9,10 @@ export const MEMORY_API_LIMITS = {
   maxIdentifierBytes: 512,
 } as const;
 
+export const SUBJEKTIV_API_LIMITS = {
+  maxBehaviorBytes: 16384,
+} as const;
+
 export type DiagnosticSeverity = "info" | "warning" | "error";
 
 export type Diagnostic = { code: string, severity: DiagnosticSeverity, message: string, };
@@ -35,9 +39,11 @@ export type MemoryStagingListResponse = { limit: number, returned_count: number,
 
 export type SubjektivSubjectState = "active" | "retired";
 
-export type SubjektivSubjectCreateRequest = { role: string, };
+export type SubjektivSubjectCreateRequest = { role: string, behavior_md?: string, };
 
-export type SubjektivSubjectResponse = { id: string, role: string, state: SubjektivSubjectState, store_revision: number, created_at: string, updated_at: string, current_worker?: | import("./worker-launch-api").WorkerLaunchWorkerSummary | null, };
+export type SubjektivSubjectBehaviorUpdateRequest = { expected_behavior_revision: number, behavior_md: string, };
+
+export type SubjektivSubjectResponse = { id: string, role: string, behavior_md: string, behavior_revision: number, state: SubjektivSubjectState, store_revision: number, created_at: string, updated_at: string, current_worker?: | import("./worker-launch-api").WorkerLaunchWorkerSummary | null, };
 
 export type SubjektivSubjectListResponse = { limit: number, items: Array<SubjektivSubjectResponse>, next_cursor?: string | null, has_more: boolean, };
 

web/workspace/src/lib/generated/repository-api.ts

@@ -1,6 +1,6 @@
 // @generated by yoi-repository-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870)
+// Input contract: 0.1.0 (sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4)
 // Options: repository-operation-schema-closure,openapi-3.1,format:uint64=safe-number,strict-safe-integers,sorted-output
 // Output: web/workspace/src/lib/generated/repository-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_repository_openapi_types -- --check

web/workspace/src/lib/generated/runtime-api.ts

@@ -1,6 +1,6 @@
 // @generated by yoi-runtime-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870)
+// Input contract: 0.1.0 (sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4)
 // Options: runtime-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/runtime-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_runtime_api_types -- --check

web/workspace/src/lib/generated/ticket-api.ts

@@ -1,6 +1,6 @@
 // @generated by yoi-ticket-browser-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870)
+// Input contract: 0.1.0 (sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4)
 // Options: ticket-objective-merge-request-browser-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/ticket-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_ticket_api_types -- --check

web/workspace/src/lib/generated/worker-launch-api.ts

@@ -1,6 +1,6 @@
 // @generated by yoi-worker-openapi-typescript@1. Do not edit.
 // Input: openapi/server-api.json
-// Input contract: 0.1.0 (sha256:f9f0f8918dbcce386e94d5368fa938f02565ca98f9f67f07537bd88ed8c49870)
+// Input contract: 0.1.0 (sha256:025ccf848b72bbadd2144980dbcd5f94f9d0d06e25de34fa2b643de042d4dcb4)
 // Options: worker-operation-schema-closure,openapi-3.1,strict-integer-ranges,sorted-output
 // Output: web/workspace/src/lib/generated/worker-launch-api.ts
 // Regenerate/check: cargo run -q -p server-api --example generate_worker_launch_api_types -- --check

web/workspace/src/lib/workspace/memory/api.ts

@@ -1,4 +1,7 @@
-import { MEMORY_API_LIMITS } from "#lib/generated/memory-api.ts";
+import {
+  MEMORY_API_LIMITS,
+  SUBJEKTIV_API_LIMITS,
+} from "#lib/generated/memory-api.ts";
 import { readBoundedJson, workspaceApiPath } from "#lib/workspace/api/http.ts";
 import type {
   Diagnostic,
@@ -26,6 +29,7 @@ import type {
   SubjektivResidentSurfaceAvailability,
   SubjektivResidentSurfaceResponse,
   SubjektivResidentSurfaceSnapshot,
+  SubjektivSubjectBehaviorUpdateRequest,
   SubjektivSubjectCreateRequest,
   SubjektivSubjectListResponse,
   SubjektivSubjectResponse,
@@ -84,6 +88,7 @@ export const MEMORY_API_LOAD_POLICY = {
 } as const;
 
 const MAX_SUBJECT_ROLE_BYTES = 256;
+export const MAX_SUBJECT_BEHAVIOR_BYTES = SUBJEKTIV_API_LIMITS.maxBehaviorBytes;
 const MAX_SUBJECT_CREATE_ERROR_BYTES = 1024 * 1024;
 
 export type SubjektivSubjectCreateErrorKind =
@@ -126,7 +131,31 @@ export function validateSubjektivSubjectCreateRequest(
       "Subject role must be at most 256 bytes and contain no control characters.",
     );
   }
-  return { role: request.role };
+  const behaviorMd = request.behavior_md ?? "";
+  validateSubjectBehavior(behaviorMd);
+  return { role: request.role, behavior_md: behaviorMd };
+}
+
+function validateSubjectBehavior(behaviorMd: string): void {
+  const bytes = new TextEncoder().encode(behaviorMd).byteLength;
+  if (bytes > MAX_SUBJECT_BEHAVIOR_BYTES) {
+    throw new SubjektivSubjectCreateError(
+      "validation",
+      `Subject behavior must be at most ${MAX_SUBJECT_BEHAVIOR_BYTES} bytes.`,
+    );
+  }
+  if (behaviorMd.length > 0 && behaviorMd.trim().length === 0) {
+    throw new SubjektivSubjectCreateError(
+      "validation",
+      "Subject behavior must be empty or contain non-whitespace text.",
+    );
+  }
+  if (/[\u0000-\u0008\u000B\u000C\u000E-\u001F\u007F]/u.test(behaviorMd)) {
+    throw new SubjektivSubjectCreateError(
+      "validation",
+      "Subject behavior contains an unsupported control character.",
+    );
+  }
 }
 
 export async function createSubjektivSubject(
@@ -170,8 +199,11 @@ export async function createSubjektivSubject(
     const subject = parseSubjektivSubjectResponse(
       await readBoundedJson(response, MEMORY_API_LIMITS.maxResponseBytes),
     );
-    if (subject.role !== validated.role) {
+    if (
-      throw new Error("created Subject role does not match the request");
+      subject.role !== validated.role ||
+      subject.behavior_md !== validated.behavior_md
+    ) {
+      throw new Error("created Subject does not match the request");
     }
     return subject;
   } catch {
@@ -182,6 +214,68 @@ export async function createSubjektivSubject(
   }
 }
 
+export async function updateSubjektivSubjectBehavior(
+  fetchFn: typeof fetch,
+  workspaceId: string,
+  subjectId: string,
+  request: SubjektivSubjectBehaviorUpdateRequest,
+): Promise<SubjektivSubjectResponse> {
+  validateSubjectBehavior(request.behavior_md);
+  if (
+    !Number.isSafeInteger(request.expected_behavior_revision) ||
+    request.expected_behavior_revision < 0
+  ) {
+    throw new SubjektivSubjectCreateError(
+      "validation",
+      "Subject behavior revision is invalid.",
+    );
+  }
+  let response: Response;
+  try {
+    response = await fetchFn(
+      workspaceApiPath(
+        workspaceId,
+        `/subjektiv/subjects/${encodeURIComponent(subjectId)}/behavior`,
+      ),
+      {
+        method: "PATCH",
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify(request),
+      },
+    );
+  } catch {
+    throw new SubjektivSubjectCreateError(
+      "unknown_outcome",
+      "The save outcome is unknown. Reload the Subject before retrying.",
+    );
+  }
+  if (!response.ok) {
+    const message = await subjektivSubjectCreateErrorMessage(response);
+    throw new SubjektivSubjectCreateError(
+      response.status >= 500 ? "unknown_outcome" : "rejected",
+      response.status === 409
+        ? "The behavior changed elsewhere. Reload the Subject and review the latest text."
+        : message,
+      response.status,
+    );
+  }
+  try {
+    const subject = parseSubjektivSubjectResponse(
+      await readBoundedJson(response, MEMORY_API_LIMITS.maxResponseBytes),
+      subjectId,
+    );
+    if (subject.behavior_md !== request.behavior_md) {
+      throw new Error("saved Subject behavior does not match the request");
+    }
+    return subject;
+  } catch {
+    throw new SubjektivSubjectCreateError(
+      "unknown_outcome",
+      "The behavior may have been saved, but the response could not be confirmed. Reload the Subject.",
+    );
+  }
+}
+
 async function subjektivSubjectCreateErrorMessage(
   response: Response,
 ): Promise<string> {
@@ -202,7 +296,7 @@ async function subjektivSubjectCreateErrorMessage(
   } catch {
     // A rejected request still has a known outcome even when its body is invalid.
   }
-  return `Subject creation failed with HTTP ${response.status}.`;
+  return `Subject request failed with HTTP ${response.status}.`;
 }
 
 export function parseMemoryDocumentResponse(
@@ -454,6 +548,8 @@ export function parseSubjektivSubjectResponse(
     [
       "id",
       "role",
+      "behavior_md",
+      "behavior_revision",
       "state",
       "store_revision",
       "created_at",
@@ -472,6 +568,12 @@ export function parseSubjektivSubjectResponse(
   const result: SubjektivSubjectResponse = {
     id,
     role: requiredString(record, "role"),
+    behavior_md: requiredString(
+      record,
+      "behavior_md",
+      MAX_SUBJECT_BEHAVIOR_BYTES,
+    ),
+    behavior_revision: requiredNonNegativeInteger(record, "behavior_revision"),
     state,
     store_revision: requiredNonNegativeInteger(record, "store_revision"),
     created_at: requiredString(record, "created_at"),

web/workspace/src/routes/w/[workspaceId]/memory/+page.svelte

@@ -14,13 +14,16 @@
   const subjects = $derived(data.subjects.data?.items ?? []);
   let createExpanded = $state(false);
   let role = $state('');
+  let behaviorMd = $state('');
   let submitting = $state(false);
   let createError = $state<string | null>(null);
   let roleInvalid = $state(false);
+  let behaviorInvalid = $state(false);
   let createOutcomeUnknown = $state(false);
   let createdSubject = $state<SubjektivSubjectResponse | null>(null);
   let createButton = $state<HTMLButtonElement>();
   let roleInput = $state<HTMLInputElement>();
+  let behaviorInput = $state<HTMLTextAreaElement>();
 
   function subjectHref(subjectId: string): string {
     return workspaceRoute(data.workspaceId, `/memory/${encodeURIComponent(subjectId)}`);
@@ -39,6 +42,7 @@
     createExpanded = true;
     createError = null;
     roleInvalid = false;
+    behaviorInvalid = false;
     createOutcomeUnknown = false;
     createdSubject = null;
     await tick();
@@ -49,8 +53,10 @@
     if (submitting) return;
     createExpanded = false;
     role = '';
+    behaviorMd = '';
     createError = null;
     roleInvalid = false;
+    behaviorInvalid = false;
     createOutcomeUnknown = false;
     createdSubject = null;
     await tick();
@@ -62,9 +68,13 @@
     submitting = true;
     createError = null;
     roleInvalid = false;
+    behaviorInvalid = false;
     createOutcomeUnknown = false;
     try {
-      const subject = await createSubjektivSubject(fetch, data.workspaceId, { role });
+      const subject = await createSubjektivSubject(fetch, data.workspaceId, {
+        role,
+        behavior_md: behaviorMd,
+      });
       createdSubject = subject;
       try {
         await goto(subjectHref(subject.id));
@@ -73,14 +83,16 @@
       }
     } catch (error) {
       if (error instanceof SubjektivSubjectCreateError) {
-        roleInvalid = error.kind === 'validation';
+        roleInvalid = error.kind === 'validation' && error.message.startsWith('Subject role');
+        behaviorInvalid = error.kind === 'validation' && error.message.startsWith('Subject behavior');
         createOutcomeUnknown = error.kind === 'unknown_outcome';
         createError = error.status === 401 || error.status === 403
           ? 'You do not have permission to create Subjects in this Workspace.'
           : error.message;
-        if (roleInvalid) {
+        if (roleInvalid || behaviorInvalid) {
           await tick();
-          roleInput?.focus();
+          if (behaviorInvalid) behaviorInput?.focus();
+          else roleInput?.focus();
         }
       } else {
         createOutcomeUnknown = true;
@@ -149,9 +161,22 @@
           disabled={submitting || createdSubject !== null}
           onkeydown={createFormKeydown}
           aria-invalid={roleInvalid ? 'true' : undefined}
-          aria-describedby={createError ? 'subject-role-help subject-create-error' : 'subject-role-help'}
+          aria-describedby={createError && roleInvalid ? 'subject-role-help subject-create-error' : 'subject-role-help'}
         />
       </label>
+      <label class="subject-role-field">
+        <span>Behavior <small>Optional, user-managed</small></span>
+        <textarea
+          bind:this={behaviorInput}
+          bind:value={behaviorMd}
+          rows="7"
+          disabled={submitting || createdSubject !== null}
+          onkeydown={createFormKeydown}
+          aria-invalid={behaviorInvalid ? 'true' : undefined}
+          aria-describedby={createError && behaviorInvalid ? 'subject-behavior-help subject-create-error' : 'subject-behavior-help'}
+        ></textarea>
+        <small id="subject-behavior-help">Persistent guidance injected verbatim for this Subject. It remains separate from generated Memory and can be edited later.</small>
+      </label>
       {#if createError}
         <div
           id="subject-create-error"
@@ -318,20 +343,25 @@
   }
 
   .subject-create-actions {
-    grid-column: 3;
+    grid-column: 2;
-    grid-row: 1;
   }
 
   .subject-create-panel {
     display: grid;
-    grid-template-columns: minmax(14rem, 0.8fr) minmax(18rem, 1fr) auto;
+    grid-template-columns: minmax(14rem, 0.7fr) minmax(18rem, 1.3fr);
-    align-items: end;
+    align-items: start;
     gap: var(--space-4);
     padding: var(--space-4);
     background: var(--bg-raised);
     border-radius: var(--radius-soft);
   }
 
+  .subject-create-copy {
+    grid-column: 1;
+    grid-row: 1 / span 4;
+    align-self: start;
+  }
+
   .subject-create-copy h2,
   .subject-create-copy p,
   .subject-create-error p {
@@ -353,7 +383,8 @@
     font-weight: 700;
   }
 
-  .subject-role-field input {
+  .subject-role-field input,
+  .subject-role-field textarea {
     width: 100%;
     min-width: 0;
     border: 1px solid var(--line);
@@ -363,7 +394,15 @@
     color: var(--text-strong);
   }
 
-  .subject-role-field input[aria-invalid='true'] {
+  .subject-role-field textarea {
+    min-height: 8rem;
+    resize: vertical;
+    font: inherit;
+    line-height: 1.5;
+  }
+
+  .subject-role-field input[aria-invalid='true'],
+  .subject-role-field textarea[aria-invalid='true'] {
     border-color: var(--danger);
   }
 
@@ -496,6 +535,7 @@
       align-items: stretch;
     }
 
+    .subject-create-copy,
     .subject-create-error,
     .subject-create-actions {
       grid-column: 1;

web/workspace/src/routes/w/[workspaceId]/memory/[subjectId]/+page.svelte

@@ -1,14 +1,91 @@
 <script lang="ts">
+  import { untrack } from 'svelte';
   import DocumentMarkdown from '#lib/workspace/markdown/DocumentMarkdown.svelte';
   import { formatDate, workspaceRoute } from '#lib/workspace/api/http.ts';
-  import type {
+  import {
-    SubjektivMemoryState,
+    SubjektivSubjectCreateError,
-    SubjektivResidentSurfaceAvailability,
+    updateSubjektivSubjectBehavior,
-  } from '#lib/generated/memory-api.ts';
+  } from '#lib/workspace/memory/api.ts';
+  import type { SubjektivMemoryState, SubjektivResidentSurfaceAvailability } from '#lib/generated/memory-api.ts';
   import type { PageProps } from './$types';
 
   let { data }: PageProps = $props();
 
+  let subject = $state(untrack(() => data.subject.data));
+  let editingBehavior = $state(false);
+  let behaviorDraft = $state(untrack(() => subject?.behavior_md ?? ''));
+  let behaviorSaving = $state(false);
+  let behaviorError = $state<string | null>(null);
+  let behaviorSaveConfirmed = $state(false);
+
+  let routeGeneration = 0;
+  let subjectWorkspaceId = untrack(() => data.workspaceId);
+
+  // SvelteKit reuses this page across Subject and Workspace routes. A new
+  // loader snapshot owns a new editor and fences all previous mutations.
+  $effect(() => {
+    const workspaceId = data.workspaceId;
+    const subjectId = data.subjectId;
+    const loadedSubject = data.subject.data;
+    untrack(() => {
+      routeGeneration += 1;
+      subjectWorkspaceId = workspaceId;
+      subject = loadedSubject?.id === subjectId ? loadedSubject : null;
+      behaviorDraft = subject?.behavior_md ?? '';
+      editingBehavior = false;
+      behaviorSaving = false;
+      behaviorError = null;
+      behaviorSaveConfirmed = false;
+    });
+  });
+
+  async function saveBehavior(): Promise<void> {
+    if (!subject || behaviorSaving || subject.id !== data.subjectId || subjectWorkspaceId !== data.workspaceId) return;
+    const generation = routeGeneration;
+    const workspaceId = subjectWorkspaceId;
+    const subjectId = subject.id;
+    const request = {
+      expected_behavior_revision: subject.behavior_revision,
+      behavior_md: behaviorDraft,
+    };
+    const isCurrent = () => generation === routeGeneration &&
+      data.workspaceId === workspaceId && data.subjectId === subjectId;
+    behaviorSaving = true;
+    behaviorError = null;
+    behaviorSaveConfirmed = false;
+    try {
+      const updated = await updateSubjektivSubjectBehavior(fetch, workspaceId, subjectId, request);
+      if (!isCurrent()) return;
+      subject = updated;
+      behaviorDraft = updated.behavior_md;
+      editingBehavior = false;
+      behaviorSaveConfirmed = true;
+    } catch (error) {
+      if (!isCurrent()) return;
+      behaviorError = error instanceof SubjektivSubjectCreateError
+        ? (error.status === 401 || error.status === 403
+          ? 'You do not have permission to edit this Subject.'
+          : error.message)
+        : 'The save outcome is unknown. Reload the Subject before retrying.';
+    } finally {
+      if (isCurrent()) behaviorSaving = false;
+    }
+  }
+
+  function beginBehaviorEdit(): void {
+    if (!subject) return;
+    behaviorDraft = subject.behavior_md;
+    behaviorError = null;
+    behaviorSaveConfirmed = false;
+    editingBehavior = true;
+  }
+
+  function cancelBehaviorEdit(): void {
+    behaviorDraft = subject?.behavior_md ?? '';
+    behaviorError = null;
+    editingBehavior = false;
+  }
+
   const surface = $derived(data.surface.data);
   const snapshot = $derived(surface?.snapshot ?? null);
   const memories = $derived(data.memories.data?.items ?? []);
@@ -51,7 +128,7 @@
     if (availability !== 'ready') return 'No current generated context is available to use.';
     return snapshot?.body_md.trim()
       ? 'Current generated context is available.'
-      : 'A current empty surface exists; there is no resident context to show.';
+      : 'A current empty surface exists; there is no generated Memory context to show.';
   }
 
   function subjectStateLabel(state: 'active' | 'retired'): string {
@@ -60,7 +137,7 @@
 </script>
 
 <svelte:head>
-  <title>{data.subject.data?.role ?? data.subjectId} · Memory · Yoi Workspace</title>
+  <title>{subject?.role ?? data.subjectId} · Memory · Yoi Workspace</title>
   <meta name="description" content="Subject resident surface and current committed Memories" />
 </svelte:head>
 
@@ -70,23 +147,23 @@
   <header class="memory-page-header">
     <div>
       <p class="memory-eyebrow">Memory subject</p>
-      <h1 id="subject-heading">{data.subject.data?.role ?? data.subjectId}</h1>
+      <h1 id="subject-heading">{subject?.role ?? data.subjectId}</h1>
       <code class="subject-id" title={data.subjectId}>{data.subjectId}</code>
     </div>
-    <span class="read-only-label">Read-only</span>
+    <span class="read-only-label">Behavior editable</span>
   </header>
 
-  {#if data.subject.data}
+  {#if subject}
     <section class="subject-overview" aria-label="Subject status">
       <div>
         <span>Subject status</span>
-        <strong class="subject-state is-{data.subject.data.state}">{subjectStateLabel(data.subject.data.state)}</strong>
+        <strong class="subject-state is-{subject.state}">{subjectStateLabel(subject.state)}</strong>
-        <p>{data.subject.data.state === 'active' ? 'Available for new Worker connections.' : 'No longer available for new Worker connections.'}</p>
+        <p>{subject.state === 'active' ? 'Available for new Worker connections.' : 'No longer available for new Worker connections.'}</p>
       </div>
       <div>
         <span>Worker connection</span>
-        <strong>{data.subject.data.current_worker ? 'Connected' : 'Not connected'}</strong>
+        <strong>{subject.current_worker ? 'Connected' : 'Not connected'}</strong>
-        <p>{data.subject.data.current_worker?.display_name ?? 'No Worker currently owns this Subject connection.'}</p>
+        <p>{subject.current_worker?.display_name ?? 'No Worker currently owns this Subject connection.'}</p>
       </div>
       <div>
         <span>Committed Memories</span>
@@ -99,7 +176,7 @@
         {/if}
       </div>
       <div>
-        <span>Resident context</span>
+        <span>Generated Memory context</span>
         {#if surface}
           <strong class="availability is-{surface.availability}">{surfaceLabel(surface.availability)}</strong>
           <p>{surfaceSummary(surface.availability)}</p>
@@ -113,12 +190,12 @@
     <details class="subject-technical-details">
       <summary>Technical details</summary>
       <dl>
-        <div><dt>Subject ID</dt><dd><code>{data.subject.data.id}</code></dd></div>
+        <div><dt>Subject ID</dt><dd><code>{subject.id}</code></dd></div>
         <div>
           <dt>Subject store revision</dt>
-          <dd>{data.subject.data.store_revision}<small>Internal change number for committed Memories; not a Memory count or content-quality score.</small></dd>
+          <dd>{subject.store_revision}<small>Internal change number for committed Memories; not a Memory count or content-quality score.</small></dd>
         </div>
-        <div><dt>Last changed</dt><dd><time datetime={data.subject.data.updated_at}>{formatDate(data.subject.data.updated_at)}</time></dd></div>
+        <div><dt>Last changed</dt><dd><time datetime={subject.updated_at}>{formatDate(subject.updated_at)}</time></dd></div>
       </dl>
     </details>
   {:else if data.subject.error}
@@ -130,6 +207,40 @@
     <div class="memory-state" role="status"><p>Subject details are unavailable.</p></div>
   {/if}
 
+  {#if subject}
+    <section class="behavior-section" aria-labelledby="subject-behavior-heading">
+      <header class="section-heading">
+        <div>
+          <p class="memory-eyebrow">User-managed context</p>
+          <h2 id="subject-behavior-heading">Behavior</h2>
+        </div>
+        {#if !editingBehavior}
+          <button type="button" class="behavior-edit" onclick={beginBehaviorEdit}>Edit</button>
+        {/if}
+      </header>
+      <p class="behavior-help">The Host injects this text verbatim for connected Workers, separately from generated Memory. Saving confirms storage only. Connected Workers check for the latest revision before later model requests; this page does not report that application.</p>
+      {#if editingBehavior}
+        <form class="behavior-form" aria-busy={behaviorSaving} onsubmit={(event) => { event.preventDefault(); void saveBehavior(); }}>
+          <label>
+            <span class="sr-only">Subject behavior</span>
+            <textarea bind:value={behaviorDraft} rows="9" disabled={behaviorSaving} aria-invalid={behaviorError ? 'true' : undefined} aria-describedby={behaviorError ? 'subject-behavior-edit-error' : undefined}></textarea>
+          </label>
+          {#if behaviorError}<p id="subject-behavior-edit-error" class="behavior-error" role="alert">{behaviorError}</p>{/if}
+          <div class="behavior-actions">
+            <button type="submit" disabled={behaviorSaving}>{behaviorSaving ? 'Saving…' : 'Save behavior'}</button>
+            <button type="button" disabled={behaviorSaving} onclick={cancelBehaviorEdit}>Cancel</button>
+            <button type="button" disabled={behaviorSaving || behaviorDraft.length === 0} onclick={() => { behaviorDraft = ''; }}>Clear</button>
+          </div>
+        </form>
+      {:else if subject.behavior_md.length > 0}
+        <article class="behavior-document" aria-label="User-managed Subject behavior"><pre>{subject.behavior_md}</pre></article>
+      {:else}
+        <div class="memory-state" role="status"><strong>No behavior is set.</strong><p>Connected Workers receive an explicit empty behavior document.</p></div>
+      {/if}
+      {#if behaviorSaveConfirmed}<p class="behavior-saved" role="status">Behavior storage confirmed at revision {subject.behavior_revision}. This page does not confirm application by a connected Worker.</p>{/if}
+    </section>
+  {/if}
+
   <section class="surface-section" aria-labelledby="resident-surface-heading">
     <header class="section-heading">
       <div>
@@ -434,6 +545,7 @@
     color: var(--danger);
   }
 
+  .behavior-section,
   .surface-section,
   .memories-section {
     display: grid;
@@ -442,6 +554,78 @@
     padding-top: var(--space-3);
   }
 
+  .behavior-help,
+  .behavior-saved,
+  .behavior-error {
+    margin: 0;
+    color: var(--text-muted);
+    font-size: var(--font-size-compact);
+  }
+
+  .behavior-error { color: var(--danger); }
+  .behavior-saved { color: var(--success); }
+
+  .behavior-form,
+  .behavior-form label {
+    display: grid;
+    gap: var(--space-3);
+  }
+
+  .behavior-form textarea {
+    width: 100%;
+    min-height: 10rem;
+    padding: var(--space-3);
+    color: var(--text);
+    background: var(--surface-raised);
+    border: 1px solid var(--line-strong);
+    border-radius: var(--radius-sm);
+    font: inherit;
+    line-height: 1.5;
+    resize: vertical;
+  }
+
+  .behavior-actions {
+    display: flex;
+    flex-wrap: wrap;
+    gap: var(--space-2);
+  }
+
+  .behavior-edit,
+  .behavior-actions button {
+    padding: var(--space-2) var(--space-3);
+    color: var(--text);
+    background: var(--surface-raised);
+    border: 1px solid var(--line-strong);
+    border-radius: var(--radius-sm);
+    cursor: pointer;
+  }
+
+  .behavior-actions button:disabled { cursor: not-allowed; opacity: 0.55; }
+
+  .behavior-document pre {
+    margin: 0;
+    padding: var(--space-4);
+    overflow-wrap: anywhere;
+    white-space: pre-wrap;
+    background: var(--surface-raised);
+    border: 1px solid var(--line);
+    border-radius: var(--radius-sm);
+    font: inherit;
+    line-height: 1.6;
+  }
+
+  .sr-only {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    padding: 0;
+    margin: -1px;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+  }
+
   .surface-meta,
   .pill-row {
     display: flex;

web/workspace/src/routes/w/[workspaceId]/memory/memory-page.browser.spec.ts

@@ -34,6 +34,8 @@ function subject() {
   return {
     id: "subject-1",
     role: "Release coordinator",
+    behavior_md: "Prefer explicit evidence.",
+    behavior_revision: 2,
     state: "active" as const,
     store_revision: 9,
     created_at: "2026-01-01T00:00:00Z",
@@ -99,6 +101,12 @@ test("creates one Subject with the exact role and navigates to its generated det
   }) as HTMLInputElement;
   await waitFor(() => expect(document.activeElement).toBe(roleInput));
   await fireEvent.input(roleInput, { target: { value: "  Review lead  " } });
+  const behaviorInput = screen.getByRole("textbox", {
+    name: /Behavior/,
+  }) as HTMLTextAreaElement;
+  await fireEvent.input(behaviorInput, {
+    target: { value: "Challenge unsupported assumptions." },
+  });
 
   const submit = screen.getByRole("button", { name: "Create Subject" });
   await fireEvent.click(submit);
@@ -113,6 +121,8 @@ test("creates one Subject with the exact role and navigates to its generated det
   resolveRequest(Response.json({
     id: "generated-subject-1",
     role: "  Review lead  ",
+    behavior_md: "Challenge unsupported assumptions.",
+    behavior_revision: 0,
     state: "active",
     store_revision: 0,
     created_at: "2026-01-03T00:00:00Z",
@@ -130,7 +140,9 @@ test("creates one Subject with the exact role and navigates to its generated det
   ];
   expect(path).toBe("/api/w/workspace-1/subjektiv/subjects");
   expect(init.method).toBe("POST");
-  expect(init.body).toBe('{"role":"  Review lead  "}');
+  expect(init.body).toBe(
+    '{"role":"  Review lead  ","behavior_md":"Challenge unsupported assumptions."}',
+  );
 });
 
 test("keeps creation available for an empty list and restores focus on cancel", async () => {
@@ -149,7 +161,7 @@ test("keeps creation available for an empty list and restores focus on cancel",
   expect(screen.queryByRole("textbox", { name: "Role" })).toBeNull();
 });
 
-test("preserves invalid and rejected role drafts with accessible errors", async () => {
+test("preserves invalid and rejected Subject drafts with accessible field errors", async () => {
   const fetchMock = vi.fn(() =>
     Promise.resolve(Response.json(
       {
@@ -175,6 +187,20 @@ test("preserves invalid and rejected role drafts with accessible errors", async
   expect(fetchMock).not.toHaveBeenCalled();
 
   await fireEvent.input(input, { target: { value: "Release reviewer" } });
+  const behaviorInput = screen.getByRole("textbox", {
+    name: /Behavior/,
+  }) as HTMLTextAreaElement;
+  await fireEvent.input(behaviorInput, { target: { value: "   " } });
+  await fireEvent.click(screen.getByRole("button", { name: "Create Subject" }));
+  expect(screen.getByRole("alert").textContent).toContain(
+    "empty or contain non-whitespace",
+  );
+  expect(behaviorInput.getAttribute("aria-invalid")).toBe("true");
+  expect(fetchMock).not.toHaveBeenCalled();
+
+  await fireEvent.input(behaviorInput, {
+    target: { value: "Challenge unsupported assumptions." },
+  });
   await fireEvent.click(screen.getByRole("button", { name: "Create Subject" }));
   await waitFor(() => {
     expect(screen.getByRole("alert").textContent).toContain(
@@ -273,6 +299,11 @@ test("renders a ready resident surface and committed Memory lifecycle states", a
     expect(screen.getByRole("heading", { name: "Resident context", level: 1 }))
       .not.toBeNull();
   });
+  expect(
+    screen.getByRole("article", { name: "User-managed Subject behavior" })
+      .textContent,
+  )
+    .toContain("Prefer explicit evidence.");
   expect(screen.getByRole("article", { name: "Resident context" })).not
     .toBeNull();
   expect(screen.getByText("Connected", { exact: true })).not.toBeNull();
@@ -292,6 +323,272 @@ test("renders a ready resident surface and committed Memory lifecycle states", a
     .toContain("cursor=memory-next");
 });
 
+test("edits and clears user-managed behavior with CAS while distinguishing save from Worker application", async () => {
+  const fetchMock = vi.fn(async (_path: string, init?: RequestInit) => {
+    const request = JSON.parse(String(init?.body));
+    return Response.json({
+      ...subject(),
+      behavior_md: request.behavior_md,
+      behavior_revision: request.expected_behavior_revision + 1,
+    });
+  });
+  vi.stubGlobal("fetch", fetchMock);
+  render(SubjectPage, {
+    data: {
+      workspaceId: "workspace-1",
+      subjectId: "subject-1",
+      subject: result(subject()),
+      surface: result({
+        subject_id: "subject-1",
+        availability: "ungenerated" as const,
+      }),
+      memories: result({ items: [], has_more: false }),
+    },
+  } as never);
+
+  await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+  const textarea = screen.getByRole("textbox", { name: "Subject behavior" });
+  await fireEvent.input(textarea, {
+    target: { value: "Ask before irreversible actions." },
+  });
+  await fireEvent.click(screen.getByRole("button", { name: "Save behavior" }));
+  await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+  const [path, init] = fetchMock.mock.calls[0] as unknown as [
+    string,
+    RequestInit,
+  ];
+  expect(path).toBe("/api/w/workspace-1/subjektiv/subjects/subject-1/behavior");
+  expect(init.method).toBe("PATCH");
+  expect(init.body).toBe(
+    '{"expected_behavior_revision":2,"behavior_md":"Ask before irreversible actions."}',
+  );
+  await waitFor(() => {
+    expect(
+      screen.getByText(/Behavior storage confirmed at revision 3/).textContent,
+    )
+      .toContain("does not confirm application");
+  });
+  expect(
+    screen.getByRole("article", { name: "User-managed Subject behavior" })
+      .textContent,
+  )
+    .toContain("Ask before irreversible actions.");
+
+  await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+  await fireEvent.click(screen.getByRole("button", { name: "Clear" }));
+  await fireEvent.click(screen.getByRole("button", { name: "Save behavior" }));
+  await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
+  const secondBody =
+    (fetchMock.mock.calls[1] as unknown as [string, RequestInit])[1].body;
+  expect(secondBody).toBe('{"expected_behavior_revision":3,"behavior_md":""}');
+  await waitFor(() =>
+    expect(screen.getByText("No behavior is set.")).not.toBeNull()
+  );
+});
+
+function subjectPageData(record = subject(), workspaceId = "workspace-1") {
+  return {
+    workspaceId,
+    subjectId: record.id,
+    subject: result(record),
+    surface: result({
+      subject_id: record.id,
+      availability: "ungenerated" as const,
+    }),
+    memories: result({ items: [], has_more: false }),
+  };
+}
+
+test.each([
+  ["subject-2", "workspace-1"],
+  ["subject-1", "workspace-2"],
+])(
+  "resets reused Subject editor for %s in %s and saves only its own behavior",
+  async (id, workspaceId) => {
+    const nextSubject = { ...subject(), id, behavior_md: "Only B behavior." };
+    const fetchMock = vi.fn(async (_path: string, init?: RequestInit) => {
+      const request = JSON.parse(String(init?.body));
+      return Response.json({
+        ...nextSubject,
+        behavior_md: request.behavior_md,
+        behavior_revision: request.expected_behavior_revision + 1,
+      });
+    });
+    vi.stubGlobal("fetch", fetchMock);
+    const view = render(SubjectPage, { data: subjectPageData() } as never);
+    await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+    await fireEvent.input(
+      screen.getByRole("textbox", { name: "Subject behavior" }),
+      {
+        target: { value: "Unsaved A draft" },
+      },
+    );
+
+    await view.rerender(
+      { data: subjectPageData(nextSubject, workspaceId) } as never,
+    );
+    expect(screen.queryByRole("textbox", { name: "Subject behavior" }))
+      .toBeNull();
+    expect(
+      screen.getByRole("article", { name: "User-managed Subject behavior" })
+        .textContent,
+    )
+      .toContain("Only B behavior.");
+    await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+    expect(
+      (screen.getByRole("textbox", {
+        name: "Subject behavior",
+      }) as HTMLTextAreaElement).value,
+    )
+      .toBe("Only B behavior.");
+    await fireEvent.click(
+      screen.getByRole("button", { name: "Save behavior" }),
+    );
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+    const [path, init] = fetchMock.mock.calls[0] as unknown as [
+      string,
+      RequestInit,
+    ];
+    expect(path).toBe(
+      `/api/w/${workspaceId}/subjektiv/subjects/${id}/behavior`,
+    );
+    expect(JSON.parse(String(init.body))).toEqual({
+      expected_behavior_revision: 2,
+      behavior_md: "Only B behavior.",
+    });
+    await waitFor(() =>
+      expect(screen.getByText(/storage confirmed at revision 3/)).not.toBeNull()
+    );
+  },
+);
+
+test.each(["success", "failure"])(
+  "fences late %s from a previous Subject without clearing the new save state",
+  async (outcome) => {
+    const pending: Array<(response: Response) => void> = [];
+    const fetchMock = vi.fn(() =>
+      new Promise<Response>((resolve) => pending.push(resolve))
+    );
+    vi.stubGlobal("fetch", fetchMock);
+    const view = render(SubjectPage, { data: subjectPageData() } as never);
+    await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+    await fireEvent.click(
+      screen.getByRole("button", { name: "Save behavior" }),
+    );
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(1));
+
+    const nextSubject = {
+      ...subject(),
+      id: "subject-2",
+      behavior_md: "Only B behavior.",
+    };
+    await view.rerender({ data: subjectPageData(nextSubject) } as never);
+    await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+    await fireEvent.input(
+      screen.getByRole("textbox", { name: "Subject behavior" }),
+      {
+        target: { value: "Updated B behavior." },
+      },
+    );
+    await fireEvent.click(
+      screen.getByRole("button", { name: "Save behavior" }),
+    );
+    await waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
+    pending[0](
+      outcome === "success"
+        ? Response.json({
+          ...subject(),
+          behavior_md: "Late A response",
+          behavior_revision: 3,
+        })
+        : Response.json({
+          error: "Forbidden",
+          message: "A denied",
+          diagnostics: [],
+        }, { status: 403 }),
+    );
+    // Drain the previous response through its success/catch/finally branches.
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    expect(
+      screen.getByRole("button", { name: "Saving…" }).hasAttribute("disabled"),
+    ).toBe(true);
+    expect(
+      (screen.getByRole("textbox", {
+        name: "Subject behavior",
+      }) as HTMLTextAreaElement).value,
+    )
+      .toBe("Updated B behavior.");
+    expect(screen.queryByRole("alert")).toBeNull();
+    expect(screen.queryByText(/storage confirmed/)).toBeNull();
+    pending[1](
+      Response.json({
+        ...nextSubject,
+        behavior_md: "Updated B behavior.",
+        behavior_revision: 3,
+      }),
+    );
+    await waitFor(() =>
+      expect(screen.getByText(/storage confirmed at revision 3/)).not.toBeNull()
+    );
+    expect(
+      screen.getByRole("article", { name: "User-managed Subject behavior" })
+        .textContent,
+    )
+      .toContain("Updated B behavior.");
+  },
+);
+
+test("a refreshed loader snapshot fences old saves even after returning to the same Subject", async () => {
+  let resolveRequest!: (response: Response) => void;
+  vi.stubGlobal(
+    "fetch",
+    vi.fn(() =>
+      new Promise<Response>((resolve) => {
+        resolveRequest = resolve;
+      })
+    ),
+  );
+  const view = render(SubjectPage, { data: subjectPageData() } as never);
+  await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+  await fireEvent.click(screen.getByRole("button", { name: "Save behavior" }));
+  await view.rerender(
+    { data: subjectPageData({ ...subject(), id: "subject-2" }) } as never,
+  );
+  const fresh = {
+    ...subject(),
+    behavior_md: "Fresh A loader",
+    behavior_revision: 4,
+  };
+  await view.rerender({ data: subjectPageData(fresh) } as never);
+  resolveRequest(
+    Response.json({
+      ...subject(),
+      behavior_md: "Stale A response",
+      behavior_revision: 3,
+    }),
+  );
+  await new Promise((resolve) => setTimeout(resolve, 0));
+  expect(
+    screen.getByRole("article", { name: "User-managed Subject behavior" })
+      .textContent,
+  )
+    .toContain("Fresh A loader");
+  expect(screen.queryByText(/storage confirmed/)).toBeNull();
+
+  await view.rerender(
+    {
+      data: {
+        ...subjectPageData(),
+        subject: result(null, "Subject unavailable"),
+      },
+    } as never,
+  );
+  expect(screen.queryByRole("button", { name: "Edit" })).toBeNull();
+  expect(
+    screen.queryByRole("article", { name: "User-managed Subject behavior" }),
+  ).toBeNull();
+});
+
 test("candidate-only Subjects show no committed Memories, not an inferred candidate count", () => {
   // The store regression candidate_decisions_reject_conflicts_and_roll_back_partial_writes
   // stages a candidate without committing a Memory. Its public read projection is
@@ -320,6 +617,65 @@ test("candidate-only Subjects show no committed Memories, not an inferred candid
   ).toBeNull();
 });
 
+test.each(["ready", "ungenerated", "stale", "failed"] as const)(
+  "user behavior and diagnostic disclosures stay independent of %s generated Memory",
+  async (availability) => {
+    const record = { ...subject(), store_revision: 0 };
+    const view = render(SubjectPage, {
+      data: {
+        ...subjectPageData(record),
+        surface: result({
+          subject_id: record.id,
+          availability,
+          ...(availability === "ready"
+            ? {
+              snapshot: {
+                snapshot_id: "empty-snapshot",
+                body_md: "",
+                memory_refs: [],
+                built_from_store_revision: 0,
+                created_at: "2026-01-02T03:04:05Z",
+              },
+            }
+            : {}),
+        }),
+      },
+    } as never);
+    expect(
+      screen.getByRole("article", { name: "User-managed Subject behavior" })
+        .textContent,
+    )
+      .toContain(record.behavior_md);
+    expect(screen.getByText("Generated Memory context", { exact: true })).not
+      .toBeNull();
+    expect(screen.getByText("No committed Memories yet.")).not.toBeNull();
+    expect(screen.getByText("Not connected", { exact: true })).not.toBeNull();
+    const technical = view.container.querySelector(
+      "details.subject-technical-details",
+    ) as HTMLDetailsElement;
+    expect(technical.open).toBe(false);
+    expect(technical.textContent).toContain("Subject store revision");
+    if (availability === "ready") {
+      expect(screen.getByText("Resident context is current but empty.")).not
+        .toBeNull();
+      expect(screen.getByText(/no generated Memory context to show/)).not
+        .toBeNull();
+      expect(
+        view.container.querySelector("details.surface-details")?.textContent,
+      )
+        .toContain("Generated from Subject revision");
+    }
+    await fireEvent.click(screen.getByRole("button", { name: "Edit" }));
+    await fireEvent.click(screen.getByRole("button", { name: "Cancel" }));
+    expect(
+      screen.getByRole("article", { name: "User-managed Subject behavior" })
+        .textContent,
+    )
+      .toContain(record.behavior_md);
+    expect(technical.open).toBe(false);
+  },
+);
+
 test("distinguishes ready-empty, stale, failed, unavailable, and request error surfaces", async () => {
   const base = {
     workspaceId: "workspace-1",

web/workspace/tests/memory-api.test.ts

@@ -12,6 +12,7 @@ import {
   parseSubjektivSubjectListResponse,
   parseSubjektivSubjectResponse,
   SubjektivSubjectCreateError,
+  updateSubjektivSubjectBehavior,
   validateSubjektivSubjectCreateRequest,
 } from "../src/lib/workspace/memory/api.ts";
 
@@ -73,6 +74,8 @@ function subject(id = "subject-1") {
   return {
     id,
     role: "Release coordinator",
+    behavior_md: "Prefer explicit evidence.",
+    behavior_revision: 2,
     state: "active",
     store_revision: 12,
     created_at: "2026-09-01T00:00:00Z",
@@ -271,7 +274,7 @@ Deno.test("Subject list parser preserves the exact bounded response", () => {
 Deno.test("Subject create request mirrors Backend role validation without rewriting input", () => {
   assertEquals(
     validateSubjektivSubjectCreateRequest({ role: "  Release coordinator  " }),
-    { role: "  Release coordinator  " },
+    { role: "  Release coordinator  ", behavior_md: "" },
   );
   assertThrows(
     () => validateSubjektivSubjectCreateRequest({ role: "   " }),
@@ -285,6 +288,70 @@ Deno.test("Subject create request mirrors Backend role validation without rewrit
     () => validateSubjektivSubjectCreateRequest({ role: "界".repeat(86) }),
     "at most 256 bytes",
   );
+  assertThrows(
+    () =>
+      validateSubjektivSubjectCreateRequest({
+        role: "Reviewer",
+        behavior_md: " ".repeat(3),
+      }),
+    "empty or contain non-whitespace",
+  );
+  assertThrows(
+    () =>
+      validateSubjektivSubjectCreateRequest({
+        role: "Reviewer",
+        behavior_md: "x".repeat(16 * 1024 + 1),
+      }),
+    "at most 16384 bytes",
+  );
+});
+
+Deno.test("Subject behavior update uses CAS and preserves exact text", async () => {
+  const requests: Array<{ path: string; init?: RequestInit }> = [];
+  const fetchFn = (async (path: string | URL | Request, init?: RequestInit) => {
+    requests.push({ path: String(path), init });
+    return Response.json({
+      ...subject("subject/one"),
+      behavior_md: "Line one.\nLine two.",
+      behavior_revision: 3,
+    });
+  }) as typeof fetch;
+
+  const updated = await updateSubjektivSubjectBehavior(
+    fetchFn,
+    "workspace one",
+    "subject/one",
+    { expected_behavior_revision: 2, behavior_md: "Line one.\nLine two." },
+  );
+  assertEquals(updated.behavior_revision, 3);
+  assertEquals(updated.behavior_md, "Line one.\nLine two.");
+  assertEquals(
+    requests[0].path,
+    "/api/w/workspace%20one/subjektiv/subjects/subject%2Fone/behavior",
+  );
+  assertEquals(requests[0].init?.method, "PATCH");
+  assertEquals(
+    requests[0].init?.body,
+    '{"expected_behavior_revision":2,"behavior_md":"Line one.\\nLine two."}',
+  );
+});
+
+Deno.test("Subject behavior update reports conflicts without claiming Worker application", async () => {
+  const conflictFetch =
+    (async () =>
+      Response.json({ message: "revision conflict" }, {
+        status: 409,
+      })) as typeof fetch;
+  await assertSubjectCreateRejects(
+    () =>
+      updateSubjektivSubjectBehavior(conflictFetch, "workspace", "subject", {
+        expected_behavior_revision: 1,
+        behavior_md: "new",
+      }),
+    "rejected",
+    "changed elsewhere",
+    409,
+  );
 });
 
 Deno.test("Subject create client sends the exact typed body once and parses the created Subject", async () => {
@@ -294,20 +361,26 @@ Deno.test("Subject create client sends the exact typed body once and parses the
     return Response.json({
       ...subject("subject-created"),
       role: "  Release coordinator  ",
+      behavior_md: "Stay concise.",
     }, { status: 201 });
   }) as typeof fetch;
 
   const created = await createSubjektivSubject(fetchFn, "workspace one", {
     role: "  Release coordinator  ",
+    behavior_md: "Stay concise.",
   });
   assertEquals(created, {
     ...subject("subject-created"),
     role: "  Release coordinator  ",
+    behavior_md: "Stay concise.",
   });
   assertEquals(requests.length, 1);
   assertEquals(requests[0].path, "/api/w/workspace%20one/subjektiv/subjects");
   assertEquals(requests[0].init?.method, "POST");
-  assertEquals(requests[0].init?.body, '{"role":"  Release coordinator  "}');
+  assertEquals(
+    requests[0].init?.body,
+    '{"role":"  Release coordinator  ","behavior_md":"Stay concise."}',
+  );
 });
 
 Deno.test("Subject create client distinguishes rejected and unknown outcomes without retrying", async () => {