test(FN-4917): complete Step 5 — add session-start recovery interaction coverage

Fusion-Task-Id: FN-4917
Fusion-Task-Lineage: 1422a545-f4b5-4e1f-a347-8be2a4202f45

packages/engine/src/__tests__/reliability-interactions/worktree-incomplete-session-start.test.ts

@@ -0,0 +1,112 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import "../executor-test-helpers.js";
+import { TaskExecutor } from "../../executor.js";
+import { createFnAgent } from "../../pi.js";
+import { createMockStore, resetExecutorMocks } from "../executor-test-helpers.js";
+
+const mockedCreateFnAgent = vi.mocked(createFnAgent);
+
+function makeTask(overrides: Record<string, unknown> = {}) {
+  return {
+    id: "FN-4917-T",
+    title: "Task",
+    description: "Desc",
+    column: "in-progress",
+    dependencies: [],
+    steps: [],
+    currentStep: 0,
+    log: [],
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+    ...overrides,
+  } as any;
+}
+
+describe("reliability interactions: FN-4917 worktree incomplete session-start", () => {
+  beforeEach(() => {
+    resetExecutorMocks();
+  });
+
+  it.each([
+    ["missing", "Refusing to start coding agent in missing worktree: /tmp/wt"],
+    ["incomplete", "Refusing to start coding agent in incomplete worktree: /tmp/wt"],
+    ["unregistered", "Refusing to start coding agent in unregistered git worktree: /tmp/wt"],
+  ])("executor auto-recovers %s session-start failures", async (classification, errorText) => {
+    const store = createMockStore();
+    const events: any[] = [];
+    store.recordRunAuditEvent = vi.fn(async (event: any) => events.push(event));
+
+    let task = makeTask({ worktree: "/tmp/wt", branch: "fusion/fn-4917-t" });
+    store.getTask.mockImplementation(async () => task);
+    store.updateTask.mockImplementation(async (_id: string, updates: any) => {
+      task = { ...task, ...updates };
+      return task;
+    });
+    store.moveTask.mockImplementation(async (_id: string, column: string, _opts?: any) => {
+      task = { ...task, column };
+    });
+
+    mockedCreateFnAgent.mockRejectedValueOnce(new Error(errorText));
+
+    const executor = new TaskExecutor(store, process.cwd());
+    await executor.execute(task);
+
+    expect(task.column).toBe("todo");
+    expect(task.status).not.toBe("failed");
+    expect(task.worktreeSessionRetryCount).toBe(1);
+    expect(task.worktree).toBeNull();
+    expect(task.branch).toBeNull();
+    expect(task.sessionFile).toBeNull();
+    expect(events.map((e) => e.mutationType)).toEqual(expect.arrayContaining([
+      "worktree:incomplete-detected",
+      "worktree:auto-recovered",
+    ]));
+    const sessionStartEvent = events.find((e) => e.mutationType === "worktree:incomplete-detected" && e.metadata?.source === "session-start");
+    expect(sessionStartEvent?.metadata?.classification).toBe(classification);
+    expect(store.logEntry).not.toHaveBeenCalledWith("FN-4917-T", expect.stringMatching(/Refusing to start coding agent/), expect.anything(), expect.anything());
+  });
+
+  it("preserves progress when steps already completed", async () => {
+    const store = createMockStore();
+    let task = makeTask({
+      worktree: "/tmp/wt",
+      branch: "fusion/fn-4917-t",
+      steps: [
+        { id: "1", title: "done", status: "done" },
+        { id: "2", title: "next", status: "pending" },
+      ],
+    });
+    store.recordRunAuditEvent = vi.fn(async () => undefined);
+    store.getTask.mockImplementation(async () => task);
+    store.updateTask.mockImplementation(async (_id: string, updates: any) => {
+      task = { ...task, ...updates };
+      return task;
+    });
+
+    mockedCreateFnAgent.mockRejectedValueOnce(new Error("Refusing to start coding agent in incomplete worktree: /tmp/wt"));
+
+    const executor = new TaskExecutor(store, process.cwd());
+    await executor.execute(task);
+
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4917-T", "todo", { preserveProgress: true });
+  });
+
+  it("does not intercept unrelated session-start failures", async () => {
+    const store = createMockStore();
+    let task = makeTask({ worktree: "/tmp/wt", branch: "fusion/fn-4917-t" });
+    store.recordRunAuditEvent = vi.fn(async () => undefined);
+    store.getTask.mockImplementation(async () => task);
+    store.updateTask.mockImplementation(async (_id: string, updates: any) => {
+      task = { ...task, ...updates };
+      return task;
+    });
+
+    mockedCreateFnAgent.mockRejectedValueOnce(new Error("model API key missing"));
+
+    const executor = new TaskExecutor(store, process.cwd());
+    await executor.execute(task);
+
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4917-T", "in-review");
+    expect(store.recordRunAuditEvent).not.toHaveBeenCalledWith(expect.objectContaining({ mutationType: "worktree:auto-recovered" }));
+  });
+});