github/copilot-sdk · error

failed to write runtime.node

Error message

failed to write runtime.node: %w

What it means

buildBundle compresses the extracted runtime.node with Zstandard into its bundle artifact via compressZstdFile. A failure reading the source addon or creating/writing the .zst artifact is wrapped with this message and aborts the bundle.

Solutions

1. Free space on the output volume or choose an --output location with sufficient capacity.
2. Confirm the output directory and artifact path are writable by the build user.
3. Check for volume quotas or small tmpfs mounts and move the output to persistent storage.
4. Re-run the build to clear transient I/O failures.

Example fix

// before
# CI artifact dir quota 1GB, runtime.node.zst ~1.2GB

// after
# raise quota or write to workspace volume
bundler --output $GITHUB_WORKSPACE/dist

if err := os.MkdirAll(filepath.Dir(runtimeArtifactPath), 0o755); err != nil {
	return fmt.Errorf("artifact dir not creatable: %w", err)
}
probe := runtimeArtifactPath + ".probe"
if err := os.WriteFile(probe, []byte("x"), 0o644); err != nil {
	return fmt.Errorf("artifact path not writable: %w", err)
}
os.Remove(probe)

func canWriteTo(dir string) bool {
	f, err := os.CreateTemp(dir, ".probe*")
	if err != nil {
		return false
	}
	f.Close()
	os.Remove(f.Name())
	return true
}

if err := buildBundle(...); err != nil {
	if strings.Contains(err.Error(), "failed to write runtime.node") {
		var pe *fs.PathError
		if errors.As(err, &pe) && errors.Is(err, syscall.ENOSPC) {
			log.Error("output volume full while writing runtime.node artifact")
		}
		return err
	}
	return err
}

When it happens

Trigger: compressZstdFile(rawLibPath, runtimeArtifactPath) errors: destination artifact path not writable, disk full, or source runtime.node unreadable.

Common situations: Output volume running out of space (runtime.node addons are large), read-only container output mounts, or quota limits on the output directory.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• failed to write output binary
• failed to write runtime wrapper
• failed to extract binary
• failed to extract binary
• failed to extract license: copy error

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/cb889f40b5674445. Report an issue: GitHub.

Appendix: source

Thrown at go/cmd/bundler/main.go:478

	if err := compressZstdFile(binaryPath, outputPath); err != nil {
		return bundleArtifacts{}, fmt.Errorf("failed to write output binary: %w", err)
	}

	rawLibPath := filepath.Join(tempDir, "runtime.node")
	if err := extractFileFromTarball(
		tarballPath,
		tempDir,
		"package/prebuilds/"+info.runtimePlatform+"/runtime.node",
		"runtime.node",
	); err != nil {
		return bundleArtifacts{}, fmt.Errorf("runtime package is missing prebuilds/%s/runtime.node: %w", info.runtimePlatform, err)
	}
	runtimeHash, err := sha256File(rawLibPath)
	if err != nil {
		return bundleArtifacts{}, fmt.Errorf("failed to hash runtime.node: %w", err)
	}
	if err := compressZstdFile(rawLibPath, runtimeArtifactPath); err != nil {
		return bundleArtifacts{}, fmt.Errorf("failed to write runtime.node: %w", err)
	}

	wrapperName := runtimeWrapperName(info.binaryName)
	rawWrapperPath := filepath.Join(tempDir, wrapperName)
	if err := extractFileFromTarball(
		tarballPath,
		tempDir,
		"package/prebuilds/"+info.runtimePlatform+"/"+wrapperName,
		wrapperName,
	); err != nil {
		return bundleArtifacts{}, fmt.Errorf("runtime package is missing prebuilds/%s/%s: %w", info.runtimePlatform, wrapperName, err)
	}
	wrapperHash, err := sha256File(rawWrapperPath)
	if err != nil {
		return bundleArtifacts{}, fmt.Errorf("failed to hash runtime wrapper: %w", err)
	}
	if err := compressZstdFile(rawWrapperPath, wrapperArtifactPath); err != nil {
		return bundleArtifacts{}, fmt.Errorf("failed to write runtime wrapper: %w", err)

View on GitHub (pinned to cd8cf15dc3)