{"record":{"id":"2b4e1ec39a5e1675","repo":"firecrawl/open-lovable","slug":"failed-to-read-file-stderr","errorCode":null,"errorMessage":"Failed to read file: ${stderr}","messagePattern":"Failed to read file: (.+?)","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"lib/sandbox/providers/vercel-provider.ts","lineNumber":229,"sourceCode":"      } else {\n        stdout = result.stdout || '';\n      }\n    } catch (e) {\n      stdout = '';\n    }\n    \n    try {\n      if (typeof result.stderr === 'function') {\n        stderr = await result.stderr();\n      } else {\n        stderr = result.stderr || '';\n      }\n    } catch (e) {\n      stderr = '';\n    }\n    \n    if (result.exitCode !== 0) {\n      throw new Error(`Failed to read file: ${stderr}`);\n    }\n    \n    return stdout;\n  }\n\n  async listFiles(directory: string = '/vercel/sandbox'): Promise<string[]> {\n    if (!this.sandbox) {\n      throw new Error('No active sandbox');\n    }\n\n    const result = await this.sandbox.runCommand({\n      cmd: 'sh',\n      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}/||\"`],\n      cwd: '/'\n    });\n    \n    // Handle stdout - it might be a function in Vercel SDK\n    let stdout = '';","sourceCodeStart":211,"sourceCodeEnd":247,"githubUrl":"https://github.com/firecrawl/open-lovable/blob/69bd93bae7a9c97ef989eb70aabe6797fb3dac89/lib/sandbox/providers/vercel-provider.ts#L211-L247","documentation":"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).","triggerScenarios":"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.","commonSituations":"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.","solutions":["Verify the file exists first (listFiles or writeFile tracking) before reading","Use absolute paths under /vercel/sandbox or ensure relative paths resolve from that cwd","Re-run setupViteApp / rewrite the file if it was expected to be scaffolded","Inspect stderr in the message to distinguish missing-file vs permission/parse issues"],"exampleFix":"// before\nconst src = await sandbox.readFile('src/App.tsx');\n// after\nconst files = await sandbox.listFiles();\nif (!files.includes('src/App.tsx')) throw new Error('File not scaffolded yet');\nconst src = await sandbox.readFile('/vercel/sandbox/src/App.tsx');","handlingStrategy":"validation","validationCode":"const files = await sandbox.listFiles();\nif (!files.includes(relPath)) throw new Error(`File ${relPath} does not exist in sandbox`);","typeGuard":"function isReadablePath(p: string): boolean { return typeof p === 'string' && p.length > 0 && !p.includes('\\\\') && !p.includes('..'); }","tryCatchPattern":"try {\n  return await sandbox.readFile(path);\n} catch (e) {\n  if (e.message.startsWith('Failed to read file:')) throw new FileNotFoundError(path, e.message);\n  throw e;\n}","preventionTips":["Check listFiles() output before reading arbitrary paths","Prefer absolute paths under /vercel/sandbox","Only read files the provider previously wrote or scaffolded","Read stderr from the error message to classify the failure"],"tags":["sandbox","filesystem","command-failed"],"backgroundTag":"command-exit-nonzero","analyzedSha":"69bd93bae7a9c97ef989eb70aabe6797fb3dac89","analyzedAt":"2026-08-28T22:20:32.339Z","schemaVersion":2},"datasetVersion":"2026-08-29T02:17:18.158Z"}