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/commands/command-executor.service.ts

@@ -1,6 +1,7 @@
 import { forwardRef, Inject, Injectable, Logger, Optional } from '@nestjs/common';
 import type { QueueHandle } from '@mosaic/queue';
 import type { SlashCommandPayload, SlashCommandResultPayload } from '@mosaic/types';
+import type { Brain } from '@mosaic/brain';
 import { AgentService } from '../agent/agent.service.js';
 import { ChatGateway } from '../chat/chat.gateway.js';
 import { SessionGCService } from '../gc/session-gc.service.js';
@@ -8,6 +9,7 @@ import { SystemOverrideService } from '../preferences/system-override.service.js
 import { ReloadService } from '../reload/reload.service.js';
 import { COMMANDS_REDIS } from './commands.tokens.js';
 import { CommandRegistryService } from './command-registry.service.js';
+import { BRAIN } from '../brain/brain.tokens.js';
 
 @Injectable()
 export class CommandExecutorService {
@@ -19,6 +21,7 @@ export class CommandExecutorService {
     @Inject(SystemOverrideService) private readonly systemOverride: SystemOverrideService,
     @Inject(SessionGCService) private readonly sessionGC: SessionGCService,
     @Inject(COMMANDS_REDIS) private readonly redis: QueueHandle['redis'],
+    @Inject(BRAIN) private readonly brain: Brain,
     @Optional()
     @Inject(forwardRef(() => ReloadService))
     private readonly reloadService: ReloadService | null,
@@ -87,7 +90,7 @@ export class CommandExecutorService {
           };
         }
         case 'agent':
-          return await this.handleAgent(args ?? null, conversationId);
+          return await this.handleAgent(args ?? null, conversationId, userId);
         case 'provider':
           return await this.handleProvider(args ?? null, userId, conversationId);
         case 'mission':
@@ -239,12 +242,14 @@ export class CommandExecutorService {
   private async handleAgent(
     args: string | null,
     conversationId: string,
+    userId: string,
   ): Promise<SlashCommandResultPayload> {
     if (!args) {
       return {
         command: 'agent',
         success: true,
-        message: 'Usage: /agent <agent-id> to switch, or /agent list to see available agents.',
+        message:
+          'Usage: /agent <agent-id> | /agent list | /agent new <name> to create a new agent.',
         conversationId,
       };
     }
@@ -258,13 +263,101 @@ export class CommandExecutorService {
       };
     }
 
-    // Switch agent — stub for now (full implementation in P8-015)
-    return {
-      command: 'agent',
-      success: true,
-      message: `Agent switch to "${args}" requested. Restart conversation to apply.`,
-      conversationId,
-    };
+    // M5-006: /agent new <name> — create a new agent config via brain.agents.create()
+    if (args.startsWith('new')) {
+      const namePart = args.slice(3).trim();
+      if (!namePart) {
+        return {
+          command: 'agent',
+          success: false,
+          message: 'Usage: /agent new <name> — provide a name for the new agent.',
+          conversationId,
+        };
+      }
+
+      try {
+        const defaultProvider = process.env['DEFAULT_PROVIDER'] ?? 'anthropic';
+        const defaultModel = process.env['DEFAULT_MODEL'] ?? 'claude-sonnet-4-5-20251001';
+
+        const newAgent = await this.brain.agents.create({
+          name: namePart,
+          provider: defaultProvider,
+          model: defaultModel,
+          status: 'idle',
+          ownerId: userId,
+          isSystem: false,
+        });
+
+        this.logger.log(`Created new agent "${newAgent.name}" (${newAgent.id}) for user ${userId}`);
+
+        return {
+          command: 'agent',
+          success: true,
+          message: `Agent "${newAgent.name}" created with ID: ${newAgent.id}. Configure it via the web dashboard.`,
+          conversationId,
+          data: { agentId: newAgent.id, agentName: newAgent.name },
+        };
+      } catch (err) {
+        this.logger.error(`Failed to create agent: ${err}`);
+        return {
+          command: 'agent',
+          success: false,
+          message: `Failed to create agent: ${String(err)}`,
+          conversationId,
+        };
+      }
+    }
+
+    // M5-003: Look up agent by name (or ID) and apply to session mid-conversation
+    const agentName = args.trim();
+    try {
+      // Try lookup by name first; fall back to ID-based lookup
+      let agentConfig = await this.brain.agents.findByName(agentName);
+      if (!agentConfig) {
+        // Try by ID (UUID-style input)
+        agentConfig = await this.brain.agents.findById(agentName);
+      }
+
+      if (!agentConfig) {
+        return {
+          command: 'agent',
+          success: false,
+          message: `Agent "${agentName}" not found. Use /agent list to see available agents.`,
+          conversationId,
+        };
+      }
+
+      // Apply the agent config to the live session and emit session:info (M5-003)
+      this.agentService.applyAgentConfig(
+        conversationId,
+        agentConfig.id,
+        agentConfig.name,
+        agentConfig.model ?? undefined,
+      );
+
+      // Broadcast updated session:info so TUI TopBar reflects new agent/model
+      this.chatGateway?.broadcastSessionInfo(conversationId, { agentName: agentConfig.name });
+
+      this.logger.log(
+        `Agent switched to "${agentConfig.name}" (${agentConfig.id}) for conversation ${conversationId} (M5-003)`,
+      );
+
+      return {
+        command: 'agent',
+        success: true,
+        message: `Switched to agent "${agentConfig.name}". System prompt and tools applied. Model: ${agentConfig.model ?? 'default'}.`,
+        conversationId,
+        data: { agentId: agentConfig.id, agentName: agentConfig.name, model: agentConfig.model },
+      };
+    } catch (err) {
+      this.logger.error(`Failed to switch agent "${agentName}": ${err}`);
+      return {
+        command: 'agent',
+        success: false,
+        message: `Failed to switch agent: ${String(err)}`,
+        conversationId,
+      };
+    }
   }
 
   private async handleProvider(