Revert "fix: Spawn chat agent in background to avoid blocking event loop"

This reverts commit 8ee02f6013.

apps/server/trpc/routers/chat-session.ts

@@ -8,6 +8,8 @@ import type { ProcedureBuilder } from '../trpc.js';
 import {
   requireAgentManager,
   requireInitiativeRepository,
+  requirePhaseRepository,
+  requirePageRepository,
   requireTaskRepository,
   requireChatSessionRepository,
 } from './_helpers.js';
@@ -81,12 +83,22 @@ export function chatSessionProcedures(publicProcedure: ProcedureBuilder) {
           }
         }
 
-        // Gather data needed for spawn (fast DB reads) before returning
+        // Spawn fresh agent with chat history + context
         const messages = await chatRepo.findMessagesBySessionId(session.id);
         const chatHistory: ChatHistoryEntry[] = messages
           .slice(-MAX_HISTORY_MESSAGES)
           .map(m => ({ role: m.role as 'user' | 'assistant' | 'system', content: m.content }));
 
+        const context = await gatherInitiativeContext(
+          ctx.phaseRepository,
+          ctx.taskRepository,
+          ctx.pageRepository,
+          input.initiativeId,
+        );
+
+        const prompt = buildChatPrompt(input.targetType, input.targetId, chatHistory, input.message);
+
+        // Create a task for the chat agent
         const targetName = input.targetType === 'phase'
           ? (await ctx.phaseRepository?.findById(input.targetId))?.name ?? input.targetId
           : (await ctx.taskRepository?.findById(input.targetId))?.name ?? input.targetId;
@@ -99,21 +111,7 @@ export function chatSessionProcedures(publicProcedure: ProcedureBuilder) {
           status: 'in_progress',
         });
 
-        const prompt = buildChatPrompt(input.targetType, input.targetId, chatHistory, input.message);
-
-        // Spawn agent in background — worktree creation + file I/O is heavy
-        // and blocks the event loop, causing ECONNREFUSED on the SSE connection.
-        // The UI detects the agent via SSE events (agent:spawned) + query invalidation.
-        const sessionId = session.id;
-        void (async () => {
-          try {
-            const context = await gatherInitiativeContext(
-              ctx.phaseRepository,
-              ctx.taskRepository,
-              ctx.pageRepository,
-              input.initiativeId,
-            );
-
+        // Determine target phase/task for input context
         const targetPhase = input.targetType === 'phase'
           ? await ctx.phaseRepository?.findById(input.targetId)
           : undefined;
@@ -137,30 +135,10 @@ export function chatSessionProcedures(publicProcedure: ProcedureBuilder) {
           },
         });
 
-            await chatRepo.updateSession(sessionId, { agentId: agent.id });
+        // Link agent to session
+        await chatRepo.updateSession(session.id, { agentId: agent.id });
 
-            ctx.eventBus.emit({
-              type: 'chat:message_created' as const,
-              timestamp: new Date(),
-              payload: { chatSessionId: sessionId, role: 'system' as const },
-            });
-          } catch (err) {
-            const msg = err instanceof Error ? err.message : String(err);
-            // Store error as system message so the UI can display it
-            await chatRepo.createMessage({
-              chatSessionId: sessionId,
-              role: 'system',
-              content: `Failed to start agent: ${msg}`,
-            });
-            ctx.eventBus.emit({
-              type: 'chat:message_created' as const,
-              timestamp: new Date(),
-              payload: { chatSessionId: sessionId, role: 'system' as const },
-            });
-          }
-        })();
-
-        return { sessionId: session.id, agentId: null, action: 'spawned' as const };
+        return { sessionId: session.id, agentId: agent.id, action: 'spawned' as const };
       }),
 
     getChatSession: publicProcedure