Function processLambdaOutput

packages/cli/src/util/dev/builder-worker.cjs:65–86

(output)

  // Helper to handle zipBuffer - writes to temp file if too large for IPC
  async function processLambdaOutput(output) {
    const zipBuffer = await output.createZip();
    // Delete files after creating zip to avoid OOM when serializing via IPC.
    // The zipBuffer contains all file data, so files is no longer needed.
    delete output.files;

    // For large zip buffers, write to a temp file instead of sending via IPC.
    // JSON serialization of large Buffers causes OOM because each byte becomes
    // a separate array element (e.g., {"type":"Buffer","data":[1,2,3,...]}).
    if (zipBuffer.length > ZIP_BUFFER_FILE_THRESHOLD) {
      const tempDir = os.tmpdir();
      const randomId = crypto.randomBytes(8).toString('hex');
      const zipFilePath = path.join(
        tempDir,
        `vercel-dev-lambda-${randomId}.zip`
      );
      fs.writeFileSync(zipFilePath, zipBuffer);
      output.zipBufferPath = zipFilePath;
    } else {
      output.zipBuffer = zipBuffer;
    }
  }

  // Container Lambdas carry an OCI image reference in `handler`, not a code
  // bundle, so there is nothing to zip. They are built and run locally by the