firecrawl/open-lovable · error · Error

Failed to read file: ${stderr}

Error message

Failed to read file: ${stderr}

What it means

readFile() shells out via sandbox.runCommand (typically `cat <path>`) and inspects result.exitCode. If the command exits non-zero, the accumulated stderr is embedded in this Error. It reports a failed read, most commonly a missing file or a path outside the sandbox working directory (/vercel/sandbox).

Source

Thrown at lib/sandbox/providers/vercel-provider.ts:229

      } else {
        stdout = result.stdout || '';
      }
    } catch (e) {
      stdout = '';
    }
    
    try {
      if (typeof result.stderr === 'function') {
        stderr = await result.stderr();
      } else {
        stderr = result.stderr || '';
      }
    } catch (e) {
      stderr = '';
    }
    
    if (result.exitCode !== 0) {
      throw new Error(`Failed to read file: ${stderr}`);
    }
    
    return stdout;
  }

  async listFiles(directory: string = '/vercel/sandbox'): Promise<string[]> {
    if (!this.sandbox) {
      throw new Error('No active sandbox');
    }

    const result = await this.sandbox.runCommand({
      cmd: 'sh',
      args: ['-c', `find ${directory} -type f -not -path "*/node_modules/*" -not -path "*/.git/*" -not -path "*/.next/*" -not -path "*/dist/*" -not -path "*/build/*" | sed "s|^${directory}/||"`],
      cwd: '/'
    });
    
    // Handle stdout - it might be a function in Vercel SDK
    let stdout = '';

View on GitHub (pinned to 69bd93bae7)

Solutions

1. Verify the file exists first (listFiles or writeFile tracking) before reading
2. Use absolute paths under /vercel/sandbox or ensure relative paths resolve from that cwd
3. Re-run setupViteApp / rewrite the file if it was expected to be scaffolded
4. Inspect stderr in the message to distinguish missing-file vs permission/parse issues

Example fix

// before
const src = await sandbox.readFile('src/App.tsx');
// after
const files = await sandbox.listFiles();
if (!files.includes('src/App.tsx')) throw new Error('File not scaffolded yet');
const src = await sandbox.readFile('/vercel/sandbox/src/App.tsx');

const files = await sandbox.listFiles();
if (!files.includes(relPath)) throw new Error(`File ${relPath} does not exist in sandbox`);

function isReadablePath(p: string): boolean { return typeof p === 'string' && p.length > 0 && !p.includes('\\') && !p.includes('..'); }

try {
  return await sandbox.readFile(path);
} catch (e) {
  if (e.message.startsWith('Failed to read file:')) throw new FileNotFoundError(path, e.message);
  throw e;
}

When it happens

Trigger: Reading a path that does not exist in the sandbox, reading a relative path before the project files were written, path containing characters that break the sh command, or the `cat`-equivalent failing for permissions reasons so exitCode !== 0.

Common situations: Dev asks the assistant to read 'src/App.tsx' before setupViteApp scaffolded it; Windows-style backslash paths; reading after a failed file write; directory instead of a file passed to readFile.

Related errors

• Failed to list files
• Unable to read file: ${normalizedPath}
• Failed to write file via shell: ${normalizedPath}
• Failed to write file via command: ${writeResult.stderr}
• Unsupported sandbox type

AI-assisted analysis of firecrawl/open-lovable@69bd93bae7 (2026-08-28). Data as JSON: /api/errors/2b4e1ec39a5e1675. Report an issue: GitHub.