diff --git a/src/main/services/team/fileLock.ts b/src/main/services/team/fileLock.ts
index 56a1c7de..46bb3ada 100644
--- a/src/main/services/team/fileLock.ts
+++ b/src/main/services/team/fileLock.ts
@@ -71,8 +71,23 @@ function removeLockPath(lockPath: string): void {
 
 function writeLockFile(lockPath: string): void {
   const fd = fs.openSync(lockPath, 'wx');
-  fs.writeSync(fd, `${process.pid}\n${Date.now()}\n`);
-  fs.closeSync(fd);
+  let closeError: unknown = null;
+  try {
+    fs.writeSync(fd, `${process.pid}\n${Date.now()}\n`);
+  } finally {
+    try {
+      fs.closeSync(fd);
+    } catch (err) {
+      closeError = err;
+    }
+  }
+  if (closeError) {
+    throw closeError;
+  }
+}
+
+function isExistingLockError(code: string | undefined): boolean {
+  return code === 'EEXIST' || code === 'EISDIR';
 }
 
 function tryAcquire(lockPath: string, options: Required<FileLockOptions>): boolean {
@@ -85,19 +100,27 @@ function tryAcquire(lockPath: string, options: Required<FileLockOptions>): boole
   } catch (err) {
     const code = (err as NodeJS.ErrnoException).code;
     if (code === 'ENOENT') {
-      // Lock directory missing — create it lazily and acquire in the same call, so
+      // Lock directory missing - create it lazily and acquire in the same call, so
       // first-acquire latency in a fresh dir is unchanged.
       try {
         fs.mkdirSync(path.dirname(lockPath), { recursive: true });
         writeLockFile(lockPath);
         return true;
-      } catch {
-        // Lost a race (another process created the dir/lock) or still failing —
-        // fall through to a normal retry on the next loop iteration.
-        return false;
+      } catch (retryError) {
+        const retryCode = (retryError as NodeJS.ErrnoException).code;
+        if (retryCode === 'ENOENT') {
+          return false;
+        }
+        if (isExistingLockError(retryCode)) {
+          if (shouldBreakExistingLock(lockPath, options.staleTimeoutMs)) {
+            removeLockPath(lockPath);
+          }
+          return false;
+        }
+        throw retryError;
       }
     }
-    if (code === 'EEXIST' || code === 'EISDIR') {
+    if (isExistingLockError(code)) {
       if (shouldBreakExistingLock(lockPath, options.staleTimeoutMs)) {
         removeLockPath(lockPath);
       }
diff --git a/test/main/services/team/fileLock.test.ts b/test/main/services/team/fileLock.test.ts
index fdb99841..c99825ec 100644
--- a/test/main/services/team/fileLock.test.ts
+++ b/test/main/services/team/fileLock.test.ts
@@ -1,9 +1,10 @@
+import { withFileLock } from '@main/services/team/fileLock';
 import * as fs from 'fs';
 import * as os from 'os';
 import * as path from 'path';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
-import { withFileLock } from '@main/services/team/fileLock';
+const canAssertPosixPermissions = process.platform !== 'win32' && process.getuid?.() !== 0;
 
 describe('withFileLock', () => {
   let tmpDir: string;
@@ -111,4 +112,24 @@ describe('withFileLock', () => {
     expect(result).toBe('created');
     expect(fs.existsSync(`${nested}.lock`)).toBe(false);
   });
+
+  it.skipIf(!canAssertPosixPermissions)(
+    'rethrows fatal errors while creating missing lock directory',
+    async () => {
+      const readonlyDir = path.join(tmpDir, 'readonly');
+      fs.mkdirSync(readonlyDir, 0o555);
+      const nested = path.join(readonlyDir, 'missing', 'test.json');
+
+      try {
+        await expect(
+          withFileLock(nested, async () => 'ok', {
+            acquireTimeoutMs: 25,
+            retryIntervalMs: 1,
+          })
+        ).rejects.toMatchObject({ code: 'EACCES' });
+      } finally {
+        fs.chmodSync(readonlyDir, 0o755);
+      }
+    }
+  );
 });