feat(HAI-091): add agent log persistence to triage and merger agents

- Add agent log persistence to triage agent with log capture and storage
- Add agent log persistence to merger agent with log capture and storage
- Add unit tests for triage agent log persistence
- Add unit tests for merger agent log persistence

packages/engine/src/merger.test.ts

@@ -45,6 +45,7 @@ function createMockStore(taskOverrides: Partial<Task> = {}, allTasks: Task[] = [
     updateTask: vi.fn().mockResolvedValue(baseTask),
     moveTask: vi.fn().mockResolvedValue(baseTask),
     logEntry: vi.fn().mockResolvedValue(undefined),
+    appendAgentLog: vi.fn().mockResolvedValue(undefined),
     getSettings: vi.fn().mockResolvedValue({ ...DEFAULT_SETTINGS }),
     emit: vi.fn(),
     on: vi.fn(),
@@ -183,3 +184,92 @@ describe("aiMergeTask — conditional worktree cleanup", () => {
     expect(result.merged).toBe(true);
   });
 });
+
+describe("aiMergeTask — agent log persistence", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockedExistsSync.mockReturnValue(true);
+    setupHappyPathExecSync();
+  });
+
+  it("logs text deltas to store.appendAgentLog", async () => {
+    let capturedOnText: ((delta: string) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnText = opts.onText;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            capturedOnText?.("Hello ");
+            capturedOnText?.("merge");
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const worktreePath = "/tmp/root/.worktrees/HAI-050";
+    const store = createMockStore(
+      { id: "HAI-050", worktree: worktreePath },
+      [{ id: "HAI-050", worktree: worktreePath, column: "in-review" } as Task],
+    );
+
+    await aiMergeTask(store, "/tmp/root", "HAI-050");
+
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-050", "Hello merge", "text");
+  });
+
+  it("logs tool invocations to store.appendAgentLog", async () => {
+    let capturedOnToolStart: ((name: string, args: any) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnToolStart = opts.onToolStart;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            capturedOnToolStart?.("Bash", { command: "git status" });
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const worktreePath = "/tmp/root/.worktrees/HAI-050";
+    const store = createMockStore(
+      { id: "HAI-050", worktree: worktreePath },
+      [{ id: "HAI-050", worktree: worktreePath, column: "in-review" } as Task],
+    );
+
+    await aiMergeTask(store, "/tmp/root", "HAI-050");
+
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-050", "Bash", "tool");
+  });
+
+  it("still fires onAgentText callback alongside logging", async () => {
+    const onAgentText = vi.fn();
+    let capturedOnText: ((delta: string) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnText = opts.onText;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            capturedOnText?.("hi");
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const worktreePath = "/tmp/root/.worktrees/HAI-050";
+    const store = createMockStore(
+      { id: "HAI-050", worktree: worktreePath },
+      [{ id: "HAI-050", worktree: worktreePath, column: "in-review" } as Task],
+    );
+
+    await aiMergeTask(store, "/tmp/root", "HAI-050", { onAgentText });
+
+    expect(onAgentText).toHaveBeenCalledWith("hi");
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-050", "hi", "text");
+  });
+});

packages/engine/src/merger.ts

@@ -185,12 +185,49 @@ export async function aiMergeTask(
     `[merger] ${taskId}: ${hasConflicts ? "resolving conflicts + " : ""}writing commit message`,
   );
 
+  // ── Agent log buffering ──────────────────────────────────────────
+  let textBuffer = "";
+  let flushTimer: ReturnType<typeof setTimeout> | null = null;
+  const FLUSH_INTERVAL_MS = 500;
+  const FLUSH_SIZE_BYTES = 1024;
+
+  const flushTextBuffer = async () => {
+    if (textBuffer.length === 0) return;
+    const chunk = textBuffer;
+    textBuffer = "";
+    try {
+      await store.appendAgentLog(taskId, chunk, "text");
+    } catch { /* best-effort persistence */ }
+  };
+
+  const scheduleFlush = () => {
+    if (flushTimer) return;
+    flushTimer = setTimeout(async () => {
+      flushTimer = null;
+      await flushTextBuffer();
+    }, FLUSH_INTERVAL_MS);
+  };
+
   const { session } = await createHaiAgent({
     cwd: rootDir,
     systemPrompt: MERGE_SYSTEM_PROMPT,
     tools: "coding",
-    onText: (delta) => options.onAgentText?.(delta),
-    onToolStart: (name, _args) => options.onAgentTool?.(name),
+    onText: (delta) => {
+      options.onAgentText?.(delta);
+      textBuffer += delta;
+      if (textBuffer.length >= FLUSH_SIZE_BYTES) {
+        if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+        flushTextBuffer();
+      } else {
+        scheduleFlush();
+      }
+    },
+    onToolStart: (name, _args) => {
+      options.onAgentTool?.(name);
+      if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+      flushTextBuffer();
+      store.appendAgentLog(taskId, name, "tool").catch(() => {});
+    },
   });
 
   try {
@@ -221,6 +258,8 @@ export async function aiMergeTask(
     } catch { /* */ }
     throw new Error(`AI merge failed for ${taskId}: ${err.message}`);
   } finally {
+    if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+    await flushTextBuffer();
     session.dispose();
   }
 

packages/engine/src/triage.test.ts

@@ -30,6 +30,7 @@ function createMockStore(tasks: any[] = []) {
     }),
     updateTask: vi.fn().mockResolvedValue({}),
     moveTask: vi.fn().mockResolvedValue({}),
+    appendAgentLog: vi.fn().mockResolvedValue(undefined),
     getSettings: vi.fn().mockResolvedValue({
       maxConcurrent: 2,
       maxWorktrees: 4,
@@ -420,3 +421,113 @@ describe("TriageProcessor deleted task handling", () => {
     expect(mockedCreateHaiAgent).toHaveBeenCalled();
   });
 });
+
+describe("TriageProcessor agent log persistence", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("logs text deltas to store.appendAgentLog", async () => {
+    const store = createMockStore();
+    let capturedOnText: ((delta: string) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnText = opts.onText;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            // Simulate text deltas from the agent
+            capturedOnText?.("Hello ");
+            capturedOnText?.("world");
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const triage = new TriageProcessor(store, "/tmp/test", {});
+    await triage.specifyTask({
+      id: "HAI-001",
+      title: "Test",
+      description: "Test",
+      column: "triage",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    });
+
+    // Text buffer is flushed in finally block
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-001", "Hello world", "text");
+  });
+
+  it("logs tool invocations to store.appendAgentLog", async () => {
+    const store = createMockStore();
+    let capturedOnToolStart: ((name: string, args: any) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnToolStart = opts.onToolStart;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            capturedOnToolStart?.("Read", { path: "foo.ts" });
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const triage = new TriageProcessor(store, "/tmp/test", {});
+    await triage.specifyTask({
+      id: "HAI-001",
+      title: "Test",
+      description: "Test",
+      column: "triage",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    });
+
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-001", "Read", "tool");
+  });
+
+  it("still fires onAgentText callback alongside logging", async () => {
+    const store = createMockStore();
+    const onAgentText = vi.fn();
+    let capturedOnText: ((delta: string) => void) | undefined;
+
+    mockedCreateHaiAgent.mockImplementation(async (opts: any) => {
+      capturedOnText = opts.onText;
+      return {
+        session: {
+          prompt: vi.fn().mockImplementation(async () => {
+            capturedOnText?.("hi");
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const triage = new TriageProcessor(store, "/tmp/test", { onAgentText });
+    await triage.specifyTask({
+      id: "HAI-001",
+      title: "Test",
+      description: "Test",
+      column: "triage",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    });
+
+    expect(onAgentText).toHaveBeenCalledWith("HAI-001", "hi");
+    expect(store.appendAgentLog).toHaveBeenCalledWith("HAI-001", "hi", "text");
+  });
+});

packages/engine/src/triage.ts

@@ -251,14 +251,50 @@ export class TriageProcessor {
       const promptPath = `.hai/tasks/${task.id}/PROMPT.md`;
 
       const agentWork = async () => {
+        // ── Agent log buffering ──────────────────────────────────────────
+        let textBuffer = "";
+        let flushTimer: ReturnType<typeof setTimeout> | null = null;
+        const FLUSH_INTERVAL_MS = 500;
+        const FLUSH_SIZE_BYTES = 1024;
+
+        const flushTextBuffer = async () => {
+          if (textBuffer.length === 0) return;
+          const chunk = textBuffer;
+          textBuffer = "";
+          try {
+            await this.store.appendAgentLog(task.id, chunk, "text");
+          } catch { /* best-effort persistence */ }
+        };
+
+        const scheduleFlush = () => {
+          if (flushTimer) return;
+          flushTimer = setTimeout(async () => {
+            flushTimer = null;
+            await flushTextBuffer();
+          }, FLUSH_INTERVAL_MS);
+        };
+
         const { session } = await createHaiAgent({
           cwd: this.rootDir,
           systemPrompt: TRIAGE_SYSTEM_PROMPT,
           tools: "coding",
           customTools: this.createTriageTools(),
-          onText: (delta) => this.options.onAgentText?.(task.id, delta),
-          onToolStart: (name, _args) =>
-            console.log(`[triage] ${task.id} tool: ${name}`),
+          onText: (delta) => {
+            this.options.onAgentText?.(task.id, delta);
+            textBuffer += delta;
+            if (textBuffer.length >= FLUSH_SIZE_BYTES) {
+              if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+              flushTextBuffer();
+            } else {
+              scheduleFlush();
+            }
+          },
+          onToolStart: (name, _args) => {
+            console.log(`[triage] ${task.id} tool: ${name}`);
+            if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+            flushTextBuffer();
+            this.store.appendAgentLog(task.id, name, "tool").catch(() => {});
+          },
         });
 
         try {
@@ -290,6 +326,8 @@ export class TriageProcessor {
             this.options.onSpecifyComplete?.(task);
           }
         } finally {
+          if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
+          await flushTextBuffer();
           session.dispose();
         }
       };