feat(M5-004,M5-005,M5-006,M5-007): session-conversation binding, session:info broadcast, agent creation from TUI, and session metrics (#321)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/chat/chat.gateway.ts

@@ -119,6 +119,17 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
         // When resuming an existing conversation, load prior messages to inject as context (M1-004)
         const conversationHistory = await this.loadConversationHistory(conversationId, userId);
 
+        // M5-004: Check if there's an existing sessionId bound to this conversation
+        let existingSessionId: string | undefined;
+        if (userId) {
+          existingSessionId = await this.getConversationSessionId(conversationId, userId);
+          if (existingSessionId) {
+            this.logger.log(
+              `Resuming existing sessionId=${existingSessionId} for conversation=${conversationId}`,
+            );
+          }
+        }
+
         // Determine provider/model via routing engine or per-session /model override (M4-012 / M4-007)
         let resolvedProvider = data.provider;
         let resolvedModelId = data.modelId;
@@ -153,7 +164,9 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
           }
         }
 
-        agentSession = await this.agentService.createSession(conversationId, {
+        // M5-004: Use existingSessionId as sessionId when available (session reuse)
+        const sessionIdToCreate = existingSessionId ?? conversationId;
+        agentSession = await this.agentService.createSession(sessionIdToCreate, {
           provider: resolvedProvider,
           modelId: resolvedModelId,
           agentConfigId: data.agentId,
@@ -180,10 +193,15 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     }
 
     // Ensure conversation record exists in the DB before persisting messages
+    // M5-004: Also bind the sessionId to the conversation record
     if (userId) {
       await this.ensureConversation(conversationId, userId);
+      await this.bindSessionToConversation(conversationId, userId, conversationId);
     }
 
+    // M5-007: Count the user message
+    this.agentService.recordMessage(conversationId);
+
     // Persist the user message
     if (userId) {
       try {
@@ -234,6 +252,7 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     this.agentService.addChannel(conversationId, `websocket:${client.id}`);
 
     // Send session info so the client knows the model/provider (M4-008: include routing decision)
+    // Include agentName when a named agent config is active (M5-001)
     {
       const agentSession = this.agentService.getSession(conversationId);
       if (agentSession) {
@@ -244,6 +263,7 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
           modelId: agentSession.modelId,
           thinkingLevel: piSession.thinkingLevel,
           availableThinkingLevels: piSession.getAvailableThinkingLevels(),
+          ...(agentSession.agentName ? { agentName: agentSession.agentName } : {}),
           ...(routingDecisionToStore ? { routingDecision: routingDecisionToStore } : {}),
         });
       }
@@ -301,6 +321,7 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
       modelId: session.modelId,
       thinkingLevel: session.piSession.thinkingLevel,
       availableThinkingLevels: session.piSession.getAvailableThinkingLevels(),
+      ...(session.agentName ? { agentName: session.agentName } : {}),
     });
   }
 
@@ -323,11 +344,23 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
    * Set a per-conversation model override (M4-007).
    * When set, the routing engine is bypassed and the specified model is used.
    * Pass null to clear the override and resume automatic routing.
+   * M5-005: Emits session:info to clients subscribed to this conversation when a model is set.
+   * M5-007: Records a model switch in session metrics.
    */
   setModelOverride(conversationId: string, modelName: string | null): void {
     if (modelName) {
       modelOverrides.set(conversationId, modelName);
       this.logger.log(`Model override set: conversation=${conversationId} model="${modelName}"`);
+
+      // M5-002: Update the live session's modelId so session:info reflects the new model immediately
+      this.agentService.updateSessionModel(conversationId, modelName);
+
+      // M5-005: Broadcast session:info to all clients subscribed to this conversation
+      const agentSession = this.agentService.getSession(conversationId);
+      if (agentSession) {
+        // Find all clients subscribed to this conversation and emit updated session:info
+        this.broadcastSessionInfo(conversationId);
+      }
     } else {
       modelOverrides.delete(conversationId);
       this.logger.log(`Model override cleared: conversation=${conversationId}`);
@@ -341,6 +374,39 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     return modelOverrides.get(conversationId);
   }
 
+  /**
+   * M5-005: Broadcast session:info to all clients currently subscribed to a conversation.
+   * Called on model or agent switch to ensure the TUI TopBar updates immediately.
+   */
+  broadcastSessionInfo(
+    conversationId: string,
+    extra?: { agentName?: string; routingDecision?: RoutingDecisionInfo },
+  ): void {
+    const agentSession = this.agentService.getSession(conversationId);
+    if (!agentSession) return;
+
+    const piSession = agentSession.piSession;
+    const payload = {
+      conversationId,
+      provider: agentSession.provider,
+      modelId: agentSession.modelId,
+      thinkingLevel: piSession.thinkingLevel,
+      availableThinkingLevels: piSession.getAvailableThinkingLevels(),
+      ...(extra?.agentName ? { agentName: extra.agentName } : {}),
+      ...(extra?.routingDecision ? { routingDecision: extra.routingDecision } : {}),
+    };
+
+    // Emit to all clients currently subscribed to this conversation
+    for (const [clientId, session] of this.clientSessions) {
+      if (session.conversationId === conversationId) {
+        const socket = this.server.sockets.sockets.get(clientId);
+        if (socket?.connected) {
+          socket.emit('session:info', payload);
+        }
+      }
+    }
+  }
+
   /**
    * Ensure a conversation record exists in the DB.
    * Creates it if absent — safe to call concurrently since a duplicate insert
@@ -363,6 +429,45 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     }
   }
 
+  /**
+   * M5-004: Bind the agent sessionId to the conversation record in the DB.
+   * Updates the sessionId column so future resumes can reuse the session.
+   */
+  private async bindSessionToConversation(
+    conversationId: string,
+    userId: string,
+    sessionId: string,
+  ): Promise<void> {
+    try {
+      await this.brain.conversations.update(conversationId, userId, { sessionId });
+    } catch (err) {
+      this.logger.error(
+        `Failed to bind sessionId=${sessionId} to conversation=${conversationId}`,
+        err instanceof Error ? err.stack : String(err),
+      );
+    }
+  }
+
+  /**
+   * M5-004: Retrieve the sessionId bound to a conversation, if any.
+   * Returns undefined when the conversation does not exist or has no bound session.
+   */
+  private async getConversationSessionId(
+    conversationId: string,
+    userId: string,
+  ): Promise<string | undefined> {
+    try {
+      const conv = await this.brain.conversations.findById(conversationId, userId);
+      return conv?.sessionId ?? undefined;
+    } catch (err) {
+      this.logger.error(
+        `Failed to get sessionId for conversation=${conversationId}`,
+        err instanceof Error ? err.stack : String(err),
+      );
+      return undefined;
+    }
+  }
+
   /**
    * Load prior conversation messages from DB for context injection on session resume (M1-004).
    * Returns an empty array when no history exists, the conversation is not owned by the user,
@@ -439,6 +544,17 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
           usage: usagePayload,
         });
 
+        // M5-007: Accumulate token usage in session metrics
+        if (stats?.tokens) {
+          this.agentService.recordTokenUsage(conversationId, {
+            input: stats.tokens.input ?? 0,
+            output: stats.tokens.output ?? 0,
+            cacheRead: stats.tokens.cacheRead ?? 0,
+            cacheWrite: stats.tokens.cacheWrite ?? 0,
+            total: stats.tokens.total ?? 0,
+          });
+        }
+
         // Persist the assistant message with metadata
         const cs = this.clientSessions.get(client.id);
         const userId = (client.data.user as { id: string } | undefined)?.id;