grafana/k6 · error

loading feature definitions: %w

Error message

loading feature definitions: %w

What it means

Returned by the `k6 features` command's run() when features.All() fails. All() reflects over the internal Flags struct and parses the `lifecycle`/`help` struct tags of every feature-flag field; the call fails only when those compile-time tags are malformed (non-kebab name, unknown lifecycle token). This is an invariant of k6's own code, not user input.

Source

Thrown at internal/cmd/features.go:44

	c := &featuresCmd{gs: gs}

	cmd := &cobra.Command{
		Use:   "features",
		Short: "List available feature flags",
		Long:  `List all available feature flags with their lifecycle status and description.`,
		Args:  cobra.NoArgs,
		RunE:  c.run,
	}

	cmd.Flags().BoolVar(&c.isJSON, "json", false, "output in JSON format")

	return cmd
}

func (c *featuresCmd) run(_ *cobra.Command, _ []string) error {
	all, err := features.All()
	if err != nil {
		return fmt.Errorf("loading feature definitions: %w", err)
	}

	if c.isJSON {
		return c.printJSON(all)
	}
	return c.printTable(all)
}

func (c *featuresCmd) printTable(flags []features.Flag) error {
	if len(flags) == 0 {
		return nil
	}

	w := tabwriter.NewWriter(c.gs.Stdout, 0, 0, 3, ' ', 0)
	if _, err := fmt.Fprintln(w, "FEATURE\tLIFECYCLE\tDESCRIPTION"); err != nil {
		return err
	}
	for _, f := range flags {

View on GitHub (pinned to 93accf6570)

Solutions

1. Reproduce: `k6 features` — if it fails on a stock binary, the binary is corrupted; re-download the official build
2. If this is your own xk6/extension build, check the Flags struct tags in internal/features/features.go (lifecycle must be experimental|deprecated|ga, names must match the kebab-case regex)
3. Rebuild from a clean checkout of a released tag and verify `k6 version` matches expectations

# Sanity-check the binary before relying on it
k6 version >/dev/null && k6 features >/dev/null || { echo 'k6 binary appears broken'; exit 1; }

When it happens

Trigger: Running `k6 features` (optionally --json) on a k6 build whose internal feature-flag struct tags are invalid — essentially only a faulty custom xk6 build or a corrupted binary; no flag value, script, or environment setting influences this path.

Common situations: Custom k6 forks/xk6 builds where a developer added a feature flag with a bad tag (e.g. lifecycle:"beta" or a field name producing a non-kebab string) and shipped it; virtually never seen in official releases.

Related errors

• reading --features flag: %w
• error initializing template manager: %w
• Run `k6 cloud login` to authenticate, or check the docs for
• access token not configured
• no project specified. Use --project-id, set K6_CLOUD_PROJECT

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/c5043d6f229cb13a. Report an issue: GitHub.