fix(design): daemon log stream handles open errors instead of crashing the daemon; shutdown test awaits the stubbed exit

design/src/daemon.ts

@@ -93,7 +93,11 @@ function openDaemonLog(): fs.WriteStream | null {
   try {
     const p = resolveDaemonLogPath();
     fs.mkdirSync(path.dirname(p), { recursive: true });
-    return fs.createWriteStream(p, { flags: "a" });
+    const stream = fs.createWriteStream(p, { flags: "a" });
+    stream.on("error", () => {
+      if (daemonLog === stream) daemonLog = null;
+    });
+    return stream;
   } catch {
     return null;
   }
@@ -574,7 +578,10 @@ export const __testInternals__ = {
   fetchHandler,
   idleCheckTick,
   markMeaningfulActivity,
+  daemonLog: () => daemonLog,
   resetForTest: (): void => {
+    daemonLog?.end();
+    daemonLog = undefined;
     boards.clear();
     boardMutex.clear();
     lastMeaningfulActivity = Date.now();

design/test/daemon.test.ts

@@ -16,7 +16,7 @@ const { markMeaningfulActivity } = __testInternals__;
 import { makeBoardHtml, makeTmpDir, req, resetDaemon } from "./daemon-tests-fixtures";
 import { usePrivateStateRoot } from "../../test/helpers/private-state-root";
 
-usePrivateStateRoot();
+const stateRoot = usePrivateStateRoot();
 
 let tmpDir: string;
 
@@ -368,19 +368,25 @@ describe("daemon /shutdown", () => {
     // arms setTimeout(process.exit, 50). bun test runs ALL files in one
     // process, so letting that exit fire would kill the whole suite ~100ms
     // later (exit 0, no summary — see test/no-suicide-exit.test.ts). Stub
-    // process.exit, wait past both timers so they fire harmlessly while
-    // stubbed, then restore. (resetForTest does NOT defuse the timers: the
-    // exit callback is unconditional.)
+    // process.exit and restore it only after the exit callback has reached
+    // the stub; a fixed sleep lets a late timer reach the real exit under
+    // load. (resetForTest does NOT defuse the timers: the exit callback is
+    // unconditional.)
     const origExit = process.exit;
-    (process as any).exit = (() => undefined) as any;
+    let exitCode: number | undefined;
+    const exited = new Promise<void>((resolve) => {
+      (process as any).exit = ((code?: number) => {
+        exitCode = code;
+        resolve();
+      }) as any;
+    });
     try {
       const r = await fetchHandler(req("POST", "/shutdown"));
       expect(r.status).toBe(200);
       const body = (await r.json()) as any;
       expect(body.shuttingDown).toBe(true);
-      // Let both 50ms timers (gracefulShutdown, then its process.exit) fire
-      // against the stub before restoring the real process.exit.
-      await new Promise((resolve) => setTimeout(resolve, 200));
+      await exited;
+      expect(exitCode).toBe(0);
     } finally {
       (process as any).exit = origExit;
     }
@@ -533,6 +539,30 @@ describe("daemon malformed body handling", () => {
   });
 });
 
+// ─── Daemon log ──────────────────────────────────────────────────
+
+describe("daemon log", () => {
+  test("an unopenable log disables file logging instead of raising an uncaught error", async () => {
+    // A directory where the log file belongs makes the asynchronous open fail
+    // with EISDIR, the same path as a state root removed before the open lands.
+    fs.mkdirSync(path.join(stateRoot.dir, "design-daemon.log"));
+    await publishTestBoard();
+    const log = __testInternals__.daemonLog();
+    expect(log).toBeTruthy();
+    while (__testInternals__.daemonLog() === log) await new Promise((r) => setTimeout(r, 1));
+    expect(log!.destroyed).toBe(true);
+    expect(__testInternals__.daemonLog()).toBeNull();
+
+    const dirB = makeTmpDir("log-b");
+    try {
+      await publishTestBoard({ dir: dirB });
+      expect(__testInternals__.boards.size).toBe(2);
+    } finally {
+      try { fs.rmSync(dirB, { recursive: true, force: true }); } catch {}
+    }
+  });
+});
+
 // ─── Unknown routes ──────────────────────────────────────────────
 
 describe("daemon unknown routes", () => {