feat(HAI-072): add agent log viewer with persistence, streaming, and UI

- Add agent log persistence layer with JSONL append/read and event emission in core store
- Add server-side SSE log streaming endpoint and REST route for fetching logs
- Create AgentLogViewer component and useAgentLogs hook for real-time log display
- Integrate log viewer into TaskDetailModal
- Fix pre-existing build and test errors

packages/dashboard/src/routes.test.ts

@@ -17,6 +17,7 @@ function createMockStore(overrides: Partial<TaskStore> = {}): TaskStore {
     getSettings: vi.fn().mockResolvedValue({}),
     updateSettings: vi.fn(),
     logEntry: vi.fn().mockResolvedValue(undefined),
+    getAgentLogs: vi.fn().mockResolvedValue([]),
     ...overrides,
   } as unknown as TaskStore;
 }
@@ -340,4 +341,36 @@ describe("Attachment routes", () => {
 
     expect(res.status).toBe(404);
   });
+
+  it("GET /tasks/:id/logs — returns agent logs", async () => {
+    const fakeLogs = [
+      { timestamp: "2026-01-01T00:00:00Z", taskId: "HAI-001", text: "Hello", type: "text" },
+      { timestamp: "2026-01-01T00:00:01Z", taskId: "HAI-001", text: "Read", type: "tool" },
+    ];
+    (store.getAgentLogs as ReturnType<typeof vi.fn>).mockResolvedValue(fakeLogs);
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-001/logs");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual(fakeLogs);
+    expect(store.getAgentLogs).toHaveBeenCalledWith("HAI-001");
+  });
+
+  it("GET /tasks/:id/logs — returns empty array when no logs", async () => {
+    (store.getAgentLogs as ReturnType<typeof vi.fn>).mockResolvedValue([]);
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-001/logs");
+
+    expect(res.status).toBe(200);
+    expect(res.body).toEqual([]);
+  });
+
+  it("GET /tasks/:id/logs — returns 500 on store error", async () => {
+    (store.getAgentLogs as ReturnType<typeof vi.fn>).mockRejectedValue(new Error("disk error"));
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-001/logs");
+
+    expect(res.status).toBe(500);
+    expect(res.body.error).toBe("disk error");
+  });
 });

packages/dashboard/src/routes.ts

@@ -174,6 +174,20 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
+  // Get historical agent logs for a task
+  router.get("/tasks/:id/logs", async (req, res) => {
+    try {
+      const logs = await store.getAgentLogs(req.params.id);
+      res.json(logs);
+    } catch (err: any) {
+      if (err.code === "ENOENT") {
+        res.status(404).json({ error: `Task ${req.params.id} not found` });
+      } else {
+        res.status(500).json({ error: err.message });
+      }
+    }
+  });
+
   // Get single task with prompt content
   router.get("/tasks/:id", async (req, res) => {
     try {

packages/dashboard/src/server.ts

@@ -43,6 +43,35 @@ export function createServer(store: TaskStore, options?: ServerOptions): ReturnT
   // Rate limiting — stricter limit on SSE connections
   app.get("/api/events", rateLimit(RATE_LIMITS.sse), createSSE(store));
 
+  // Per-task SSE endpoint for live agent log streaming
+  app.get("/api/tasks/:id/logs/stream", (req, res) => {
+    const taskId = req.params.id;
+
+    res.setHeader("Content-Type", "text/event-stream");
+    res.setHeader("Cache-Control", "no-cache");
+    res.setHeader("Connection", "keep-alive");
+    res.setHeader("X-Accel-Buffering", "no");
+    res.flushHeaders();
+
+    res.write(": connected\n\n");
+
+    const onAgentLog = (entry: { taskId: string; text: string; type: string; timestamp: string }) => {
+      if (entry.taskId !== taskId) return;
+      res.write(`event: agent:log\ndata: ${JSON.stringify(entry)}\n\n`);
+    };
+
+    store.on("agent:log", onAgentLog);
+
+    const heartbeat = setInterval(() => {
+      res.write(": heartbeat\n\n");
+    }, 30_000);
+
+    req.on("close", () => {
+      clearInterval(heartbeat);
+      store.off("agent:log", onAgentLog);
+    });
+  });
+
   // Rate limiting — mutation endpoints (POST/PUT/PATCH/DELETE)
   app.use("/api", rateLimit(RATE_LIMITS.api));