fix(HAI-018): complete Step 1 — fix server-side error handling in GET /tasks/:id

- Route now returns 404 only for ENOENT, 500 for transient errors
- store.getTask() retries once after 50ms on non-ENOENT failures
- Added route tests for success, 404, and 500 cases
- Updated vitest config to include src/**/*.test.* files

packages/core/src/store.ts

@@ -118,10 +118,29 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     return task;
   }
 
+  /**
+   * Read a task's JSON and prompt content.
+   *
+   * Retries once after a short delay on non-ENOENT errors to handle
+   * transient read failures caused by concurrent `writeFile` calls
+   * (e.g. partial JSON from a non-atomic write during executor updates).
+   */
   async getTask(id: string): Promise<TaskDetail> {
     const dir = this.taskDir(id);
-    const data = await readFile(join(dir, "task.json"), "utf-8");
-    const task = JSON.parse(data) as Task;
+    const taskPath = join(dir, "task.json");
+
+    let task: Task;
+    try {
+      const data = await readFile(taskPath, "utf-8");
+      task = JSON.parse(data) as Task;
+    } catch (err: any) {
+      // If the file doesn't exist, propagate immediately (true 404)
+      if (err.code === "ENOENT") throw err;
+      // Transient error (e.g. partial read / JSON parse failure) — retry once
+      await new Promise((r) => setTimeout(r, 50));
+      const data = await readFile(taskPath, "utf-8");
+      task = JSON.parse(data) as Task;
+    }
 
     let prompt = "";
     const promptPath = join(dir, "PROMPT.md");

packages/dashboard/src/routes.test.ts

@@ -0,0 +1,101 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import express from "express";
+import http from "node:http";
+import { createApiRoutes } from "./routes.js";
+import type { TaskStore } from "@hai/core";
+import type { TaskDetail } from "@hai/core";
+
+function createMockStore(overrides: Partial<TaskStore> = {}): TaskStore {
+  return {
+    getTask: vi.fn(),
+    listTasks: vi.fn().mockResolvedValue([]),
+    createTask: vi.fn(),
+    moveTask: vi.fn(),
+    updateTask: vi.fn(),
+    deleteTask: vi.fn(),
+    mergeTask: vi.fn(),
+    getSettings: vi.fn().mockResolvedValue({}),
+    updateSettings: vi.fn(),
+    ...overrides,
+  } as unknown as TaskStore;
+}
+
+const FAKE_TASK_DETAIL: TaskDetail = {
+  id: "HAI-001",
+  description: "Test task",
+  column: "in-progress",
+  dependencies: [],
+  steps: [],
+  currentStep: 0,
+  log: [],
+  createdAt: "2026-01-01T00:00:00.000Z",
+  updatedAt: "2026-01-01T00:00:00.000Z",
+  prompt: "# HAI-001\n\nTest task",
+};
+
+/** Helper: send GET and return { status, body } */
+async function GET(app: express.Express, path: string): Promise<{ status: number; body: any }> {
+  return new Promise((resolve, reject) => {
+    const server = app.listen(0, () => {
+      const addr = server.address() as { port: number };
+      http.get(`http://127.0.0.1:${addr.port}${path}`, (res) => {
+        let data = "";
+        res.on("data", (chunk) => (data += chunk));
+        res.on("end", () => {
+          server.close();
+          try {
+            resolve({ status: res.statusCode!, body: JSON.parse(data) });
+          } catch {
+            resolve({ status: res.statusCode!, body: data });
+          }
+        });
+      }).on("error", (err) => { server.close(); reject(err); });
+    });
+  });
+}
+
+describe("GET /tasks/:id", () => {
+  let store: TaskStore;
+
+  beforeEach(() => {
+    store = createMockStore();
+  });
+
+  function buildApp() {
+    const app = express();
+    app.use(express.json());
+    app.use("/api", createApiRoutes(store));
+    return app;
+  }
+
+  it("returns task detail on success", async () => {
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(FAKE_TASK_DETAIL);
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-001");
+
+    expect(res.status).toBe(200);
+    expect(res.body.id).toBe("HAI-001");
+    expect(res.body.prompt).toBe("# HAI-001\n\nTest task");
+  });
+
+  it("returns 404 when task genuinely does not exist (ENOENT)", async () => {
+    const err: NodeJS.ErrnoException = new Error("ENOENT: no such file or directory");
+    err.code = "ENOENT";
+    (store.getTask as ReturnType<typeof vi.fn>).mockRejectedValue(err);
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-999");
+
+    expect(res.status).toBe(404);
+    expect(res.body.error).toContain("not found");
+  });
+
+  it("returns 500 on transient/unexpected errors (non-ENOENT)", async () => {
+    const err = new Error("Unexpected end of JSON input");
+    (store.getTask as ReturnType<typeof vi.fn>).mockRejectedValue(err);
+
+    const res = await GET(buildApp(), "/api/tasks/HAI-001");
+
+    expect(res.status).toBe(500);
+    expect(res.body.error).toContain("Unexpected end of JSON input");
+  });
+});

packages/dashboard/src/routes.ts

@@ -107,7 +107,14 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
       const task = await store.getTask(req.params.id);
       res.json(task);
     } catch (err: any) {
-      res.status(404).json({ error: `Task ${req.params.id} not found` });
+      // ENOENT means the task directory/file genuinely doesn't exist → 404.
+      // Any other error (e.g. JSON parse failure from a concurrent partial write,
+      // or a transient FS error) should surface as 500 so clients can retry.
+      if (err.code === "ENOENT") {
+        res.status(404).json({ error: `Task ${req.params.id} not found` });
+      } else {
+        res.status(500).json({ error: err.message || "Internal server error" });
+      }
     }
   });
 

packages/dashboard/vitest.config.ts

@@ -11,6 +11,6 @@ export default defineConfig({
   },
   test: {
     environment: "jsdom",
-    include: ["app/**/*.test.{ts,tsx}"],
+    include: ["app/**/*.test.{ts,tsx}", "src/**/*.test.{ts,tsx}"],
   },
 });

pnpm-lock.yaml

@@ -115,7 +115,7 @@ importers:
         version: 5.9.3
       vitest:
         specifier: ^4.1.1
-        version: 4.1.1(@types/node@25.5.0)(vite@6.4.1(@types/node@25.5.0)(tsx@4.21.0)(yaml@2.8.3))
+        version: 4.1.1(@types/node@25.5.0)(jsdom@29.0.1)(vite@6.4.1(@types/node@25.5.0)(tsx@4.21.0)(yaml@2.8.3))
 
 packages: