What causes "Failed to write file ${filePath}: ${result.stderr}" in n8n-io/n8n?

Inspect the embedded stderr to identify the shell failure (permissions, disk space, invalid path)

Failed to write file

Error message

Failed to write file ${filePath}: ${result.stderr}

What it means

writeFileViaSandbox ran its base64-encoded write command in the sandbox and the command completed with a non-zero exit or error output; the message includes the command's stderr so the shell-level failure (disk full, permission, path issue) is visible.

Solutions

Inspect the embedded stderr to identify the shell failure (permissions, disk space, invalid path)
Retry after fixing the environment; transient sandbox I/O is already retried by the wrapper

Defensive patterns

Strategy: retry

When it happens

Trigger: Thrown at packages/@n8n/instance-ai/src/workspace/sandbox-fs.ts:153 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/d2420eda04311aac. Report an issue: GitHub.

Appendix: source

Thrown at packages/@n8n/instance-ai/src/workspace/sandbox-fs.ts:153

 * Write a file in the sandbox via shell command.
 * Uses base64 encoding to safely transfer arbitrary content without
 * shell escaping issues (heredocs break on certain characters).
 * Creates parent directories automatically.
 */
export async function writeFileViaSandbox(
	workspace: SandboxCommandTarget,
	filePath: string,
	content: string | Buffer,
	options?: SandboxIoRetryOptions,
): Promise<void> {
	await retryTransientSandboxIo(
		async () => {
			const runWriteCommand = async (command: string) => {
				const result = await runInSandbox(workspace, command, {
					abortSignal: options?.abortSignal,
				});
				if (result.exitCode !== 0) {
					throw new Error(`Failed to write file ${filePath}: ${result.stderr}`);
				}
			};

			// Ensure parent directory exists
			const dir = filePath.substring(0, filePath.lastIndexOf('/'));
			if (dir) {
				await runWriteCommand(`mkdir -p '${escapeSingleQuotes(dir)}'`);
			}

			// Encode content as base64, transfer it in small chunks, then decode in the sandbox.
			// Some providers run commands through spawn(), where a single huge argument can hit E2BIG.
			const b64 =
				typeof content === 'string'
					? Buffer.from(content, 'utf-8').toString('base64')
					: content.toString('base64');
			const tempPath = `${filePath}.base64.tmp-${Date.now()}-${Math.random().toString(36).slice(2)}`;
			const escapedTempPath = escapeSingleQuotes(tempPath);

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