grafana/k6 · critical

expected bundle type 'js', got '%s'

Error message

expected bundle type 'js', got '%s'

What it means

NewBundleFromArchive loads a tar produced by `k6 archive`; the archive's metadata.json carries a `type` field that must be 'js' (core k6 only ever writes that value). This guard in internal/js/bundle.go:146 rejects anything else before attempting to parse the script - foreign tars, corrupted metadata, or archives stamped with a different type by external tooling/xk6 extensions.

Source

Thrown at internal/js/bundle.go:146

	if err != nil {
		return nil, err
	}
	bundle.ModuleResolver.Lock()

	err = bundle.populateExports(updateOptions, bi)
	if err != nil {
		return nil, err
	}

	return bundle, nil
}

// NewBundleFromArchive creates a new bundle from an lib.Archive.
func NewBundleFromArchive(
	piState *lib.TestPreInitState, arc *lib.Archive, mr *modules.ModuleResolver,
) (*Bundle, error) {
	if arc.Type != "js" {
		return nil, fmt.Errorf("expected bundle type 'js', got '%s'", arc.Type)
	}

	env := arc.Env
	if env == nil {
		// Older archives (<=0.20.0) don't have an "env" property
		env = make(map[string]string)
	}
	maps.Copy(env, piState.RuntimeOptions.Env)
	piState.RuntimeOptions.Env = env

	return newBundle(piState, &loader.SourceData{
		Data: arc.Data,
		URL:  arc.FilenameURL,
	}, arc.Filesystems, arc.Options, false, mr)
}

func (b *Bundle) makeArchive() *lib.Archive {
	clonedSourceDataURL, _ := url.Parse(b.sourceData.URL.String())

View on GitHub (pinned to 93accf6570)

Solutions

1. Regenerate the archive from source: `k6 archive script.js` then `k6 run archive.tar`
2. Inspect the tar metadata: `tar -xOf archive.tar metadata.json` and confirm it contains "type": "js"
3. If archiving is not needed, run the .js script directly

Example fix

# before: re-packed/hand-edited archive
k6 run repacked.tar  # ERRO ... expected bundle type 'js', got ''

# after: build a clean archive from the source script
k6 archive script.js && k6 run archive.tar

# verify archive metadata before running
if ! tar -xOf archive.tar metadata.json 2>/dev/null | grep -q '"type": *"js"'; then
  echo 'archive is not a k6 JavaScript archive - regenerate with: k6 archive script.js' >&2
  exit 1
fi
k6 run archive.tar

When it happens

Trigger: `k6 run some.tar` where metadata.json is missing, corrupt, or has type != "js"; Go code calling js.NewBundleFromArchive with an lib.Archive built by another tool; a tar that was unpacked, edited, and re-packed without a valid metadata.json.

Common situations: Pipelines that transform or re-package archives (adding files, renaming) and drop or mangle metadata.json; passing an unrelated .tar to k6 run; archives produced by third-party tooling that emits its own type field.

Related errors

• Unexpected end of selector while parsing selector `${selecto
• missing required url
• browser process ended unexpectedly
• must be an object with key-value pairs
• urlTemplate must contain {key} placeholder

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/3ed34324f68f338e. Report an issue: GitHub.