fix: wire generated_by_model into observation write path

The generated_by_model column was added to the observations table in the
Phase 0 governance schema migration but never wired into the INSERT
statements. All 3,878+ observations in production have this field NULL.

This fix threads the model ID from each agent (SDKAgent, GeminiAgent,
OpenRouterAgent) through processAgentResponse() into storeObservation(),
storeObservations(), and storeObservationsAndMarkComplete().

Unblocks Thompson Sampling RFC (#1571) which needs {obs_type}:{model}
as the bandit arm key.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/sqlite/SessionStore.ts

@@ -1517,7 +1517,8 @@ export class SessionStore {
     },
     promptNumber?: number,
     discoveryTokens: number = 0,
-    overrideTimestampEpoch?: number
+    overrideTimestampEpoch?: number,
+    generatedByModel?: string
   ): { id: number; createdAtEpoch: number } {
     // Use override timestamp if provided (for processing backlog messages with original timestamps)
     const timestampEpoch = overrideTimestampEpoch ?? Date.now();
@@ -1533,8 +1534,9 @@ export class SessionStore {
     const stmt = this.db.prepare(`
       INSERT INTO observations
       (memory_session_id, project, type, title, subtitle, facts, narrative, concepts,
-       files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch)
+       files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch,
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+       generated_by_model)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
     `);
 
     const result = stmt.run(
@@ -1552,7 +1554,8 @@ export class SessionStore {
       discoveryTokens,
       contentHash,
       timestampIso,
-      timestampEpoch
+      timestampEpoch,
+      generatedByModel || null
     );
 
     return {
@@ -1651,7 +1654,8 @@ export class SessionStore {
     } | null,
     promptNumber?: number,
     discoveryTokens: number = 0,
-    overrideTimestampEpoch?: number
+    overrideTimestampEpoch?: number,
+    generatedByModel?: string
   ): { observationIds: number[]; summaryId: number | null; createdAtEpoch: number } {
     // Use override timestamp if provided
     const timestampEpoch = overrideTimestampEpoch ?? Date.now();
@@ -1665,8 +1669,9 @@ export class SessionStore {
       const obsStmt = this.db.prepare(`
         INSERT INTO observations
         (memory_session_id, project, type, title, subtitle, facts, narrative, concepts,
-         files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch)
+         files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch,
-        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+         generated_by_model)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
       `);
 
       for (const observation of observations) {
@@ -1693,7 +1698,8 @@ export class SessionStore {
           discoveryTokens,
           contentHash,
           timestampIso,
-          timestampEpoch
+          timestampEpoch,
+          generatedByModel || null
         );
         observationIds.push(Number(result.lastInsertRowid));
       }
@@ -1780,7 +1786,8 @@ export class SessionStore {
     _pendingStore: PendingMessageStore,
     promptNumber?: number,
     discoveryTokens: number = 0,
-    overrideTimestampEpoch?: number
+    overrideTimestampEpoch?: number,
+    generatedByModel?: string
   ): { observationIds: number[]; summaryId?: number; createdAtEpoch: number } {
     // Use override timestamp if provided
     const timestampEpoch = overrideTimestampEpoch ?? Date.now();
@@ -1794,8 +1801,9 @@ export class SessionStore {
       const obsStmt = this.db.prepare(`
         INSERT INTO observations
         (memory_session_id, project, type, title, subtitle, facts, narrative, concepts,
-         files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch)
+         files_read, files_modified, prompt_number, discovery_tokens, content_hash, created_at, created_at_epoch,
-        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+         generated_by_model)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
       `);
 
       for (const observation of observations) {
@@ -1822,7 +1830,8 @@ export class SessionStore {
           discoveryTokens,
           contentHash,
           timestampIso,
-          timestampEpoch
+          timestampEpoch,
+          generatedByModel || null
         );
         observationIds.push(Number(result.lastInsertRowid));
       }

src/services/worker/GeminiAgent.ts

@@ -175,7 +175,9 @@ export class GeminiAgent {
           worker,
           tokensUsed,
           null,
-          'Gemini'
+          'Gemini',
+          undefined,
+          model
         );
       } else {
         logger.error('SDK', 'Empty Gemini init response - session may lack context', {
@@ -248,7 +250,8 @@ export class GeminiAgent {
               tokensUsed,
               originalTimestamp,
               'Gemini',
-              lastCwd
+              lastCwd,
+              model
             );
           } else {
             logger.warn('SDK', 'Empty Gemini observation response, skipping processing to preserve message', {
@@ -298,7 +301,8 @@ export class GeminiAgent {
               tokensUsed,
               originalTimestamp,
               'Gemini',
-              lastCwd
+              lastCwd,
+              model
             );
           } else {
             logger.warn('SDK', 'Empty Gemini summary response, skipping processing to preserve message', {

src/services/worker/OpenRouterAgent.ts

@@ -131,7 +131,8 @@ export class OpenRouterAgent {
           tokensUsed,
           null,
           'OpenRouter',
-          undefined  // No lastCwd yet - before message processing
+          undefined,  // No lastCwd yet - before message processing
+          model
         );
       } else {
         logger.error('SDK', 'Empty OpenRouter init response - session may lack context', {
@@ -202,7 +203,8 @@ export class OpenRouterAgent {
             tokensUsed,
             originalTimestamp,
             'OpenRouter',
-            lastCwd
+            lastCwd,
+            model
           );
 
         } else if (message.type === 'summarize') {
@@ -244,7 +246,8 @@ export class OpenRouterAgent {
             tokensUsed,
             originalTimestamp,
             'OpenRouter',
-            lastCwd
+            lastCwd,
+            model
           );
         }
       }

src/services/worker/SDKAgent.ts

@@ -270,7 +270,8 @@ export class SDKAgent {
             discoveryTokens,
             originalTimestamp,
             'SDK',
-            cwdTracker.lastCwd
+            cwdTracker.lastCwd,
+            modelId
           );
         }
 

src/services/worker/agents/ResponseProcessor.ts

@@ -54,7 +54,8 @@ export async function processAgentResponse(
   discoveryTokens: number,
   originalTimestamp: number | null,
   agentName: string,
-  projectRoot?: string
+  projectRoot?: string,
+  modelId?: string
 ): Promise<void> {
   // Track generator activity for stale detection (Issue #1099)
   session.lastGeneratorActivity = Date.now();
@@ -102,7 +103,8 @@ export async function processAgentResponse(
     summaryForStore,
     session.lastPromptNumber,
     discoveryTokens,
-    originalTimestamp ?? undefined
+    originalTimestamp ?? undefined,
+    modelId
   );
 
   // Log storage result with IDs for end-to-end traceability