gildas-lormeau/SingleFile · error · Error

error.message + " (MCP)"

Error message

error.message + " (MCP)"

What it means

saveWithMCP wraps any error from the MCP client upload (new MCP(serverUrl, authToken).upload(...)) and rethrows with an " (MCP)" suffix plus the original error as cause. The suffix identifies the MCP server destination as the failure point.

Source

Thrown at src/core/bg/downloads.js:521

			const client = new WebDAV(url, username, password);
			business.setCancelCallback(taskId, () => client.abort());
			return await client.upload(filename, content, { filenameConflictAction, prompt });
		}
	} catch (error) {
		throw new Error(error.message + " (WebDAV)", { cause: error });
	}
}

async function saveWithMCP(taskId, filename, content, serverUrl, authToken, { filenameConflictAction, prompt }) {
	try {
		const taskInfo = business.getTaskInfo(taskId);
		if (!taskInfo || !taskInfo.cancelled) {
			const client = new MCP(serverUrl, authToken);
			business.setCancelCallback(taskId, () => client.abort());
			return await client.upload(filename, content, { filenameConflictAction, prompt });
		}
	} catch (error) {
		throw new Error(error.message + " (MCP)", { cause: error });
	}
}

async function saveToGDrive(taskId, filename, blob, authOptions, uploadOptions) {
	try {
		await getAuthInfo(authOptions);
		const taskInfo = business.getTaskInfo(taskId);
		if (!taskInfo || !taskInfo.cancelled) {
			return await gDrive.upload(filename, blob, uploadOptions, callback => business.setCancelCallback(taskId, callback));
		}
	}
	catch (error) {
		if (error.message == "invalid_token") {
			let authInfo;
			try {
				authInfo = await gDrive.refreshAuthToken();
			} catch (error) {
				if (error.message == "unknown_token") {

View on GitHub (pinned to 517fb7c5cf)

Solutions

  1. Inspect error.cause and verify serverUrl points at a running MCP server
  2. Regenerate/refresh the authToken and retry
  3. Test the server endpoint with curl to see the raw status code
  4. Check proxy/timeout settings if uploads of large pages fail midway

Example fix

// before
new MCP('http://localhost:9999', staleToken);
// after
new MCP('http://localhost:3000', await getFreshMcpToken());
Defensive patterns

Strategy: try-catch

Validate before calling

try {
  const res = await fetch(serverUrl, { method: 'HEAD' });
  if (!res.ok) throw new Error('MCP server not reachable: ' + res.status);
} catch (e) { throw new Error('MCP server unreachable before save: ' + e.message); }

Type guard

function hasMCPConfig(o) {
  try { return !!new URL(o.serverUrl) && typeof o.authToken === 'string' && o.authToken.length > 0; }
  catch { return false; }
}

Try / catch

try {
  await saveWithMCP(taskId, filename, content, mcpOpts);
} catch (error) {
  if (error.message.endsWith('(MCP)')) {
    await refreshToken();
    // optionally retry once
  } else { throw error; }
}

Prevention

When it happens

Trigger: Any rejection inside MCP.upload(filename, content, {filenameConflictAction, prompt}) from downloadContent/downloadCompressedContent: server unreachable, invalid/missing auth token, server error response, or abort.

Common situations: MCP server URL mistyped or server down; auth token expired or rotated; server rejecting the upload endpoint/CORS; reverse proxy returning 502/504 during large uploads.

Related errors

AI-assisted analysis of gildas-lormeau/SingleFile@517fb7c5cf (2026-09-01). Data as JSON: /api/errors/ba632024659325c7. Report an issue: GitHub.