What causes "Failed to write lock file: ${message}" in withastro/astro?

Ensure the project root (and `.astro/`) is writable by the current user.

withastro/astro · error · Error

Failed to write lock file: ${message}

Error message

Failed to write lock file: ${message}

What it means

`writeLockFile` serializes the dev/build lock file to `<root>/.astro/`; if directory creation or `writeFileSync` fails (permissions, disk full, read-only FS, path issues), the error is caught and re-thrown as a plain `Error` prefixed 'Failed to write lock file:'. This wraps low-level FS errors with actionable context.

Source

Thrown at packages/astro/src/core/dev/lockfile.ts:122

	} catch {
		return null;
	}
}

/**
 * Write the lock file to disk.
 */
export function writeLockFile(root: URL, data: LockFileData, command: ServerCommand = 'dev'): void {
	const lockFileURL = getLockFileURL(root, command);
	const dirPath = fileURLToPath(new URL('.astro/', root));
	try {
		if (!existsSync(dirPath)) {
			mkdirSync(dirPath, { recursive: true });
		}
		writeFileSync(lockFileURL, serializeLockFile(data), 'utf-8');
	} catch (err) {
		const message = err instanceof Error ? err.message : String(err);
		throw new Error(`Failed to write lock file: ${message}`);
	}
}

/**
 * Remove the lock file from disk. No-op if it doesn't exist.
 */
export function removeLockFile(root: URL, command: ServerCommand = 'dev'): void {
	const lockFileURL = getLockFileURL(root, command);
	try {
		unlinkSync(lockFileURL);
	} catch (err: any) {
		// ENOENT means the file doesn't exist, which is fine.
		// Any other error (permissions, etc.) should be surfaced.
		if (err?.code !== 'ENOENT') {
			throw err;
		}
	}
}

View on GitHub (pinned to d081033d5f)

Solutions

Ensure the project root (and `.astro/`) is writable by the current user.
Free disk space if ENOSPC; on Windows, close processes locking the file.
In CI/Docker, mount or create a writable `.astro/` directory.
Run `astro sync` once in a build step that has write access, then copy artifacts.

Defensive patterns

Strategy: try-catch

Validate before calling

const fs = require('fs'); const dir = path.join(root, '.astro'); try { fs.accessSync(dir, fs.constants.W_OK); } catch { /* ensure writable or create */ }

Type guard

function isDirWritable(p) { try { fs.accessSync(p, fs.constants.W_OK); return true; } catch { return false; } }

Try / catch

try { writeLockFile(root, data); } catch (e) { if (/Failed to write lock file/.test(e.message)) { /* handle FS/permission issue */ } else throw e; }

Prevention

Ensure the project root is writable in CI/Docker.
Pre-warm .astro/ via `astro sync` in a writable build step.
Avoid read-only source mounts for dev/build environments.

When it happens

Trigger: Running `astro dev`/`astro build` in a directory where `.astro/` cannot be created or written: read-only filesystem, insufficient permissions, EBUSY on Windows, ENOSPC, or a path collision. The `catch` at `lockfile.ts:122` wraps any thrown error.

Common situations: CI with a read-only source mount; Docker `COPY` without writable layer; a previous crash leaving a locked file on Windows; disk-full environments; running from a tarball extraction that dropped write bits.

Related errors

AI-assisted analysis of withastro/astro@d081033d5f (2026-08-12). Data as JSON: /api/errors/fe9c62d6ae6eb15e. Report an issue: GitHub.