failed to get version details with extensions: %w

Error message

failed to get version details with extensions: %w

What it means

'k6 version --json' collects version details including all registered extensions via versionDetailsWithExtensions; if that collection fails (today, the 'unhandled extension type' guard), the error is wrapped as "failed to get version details with extensions" and no JSON is produced.

Source

Thrown at internal/cmd/version.go:229

	return details, nil
}

type versionCmd struct {
	gs     *state.GlobalState
	isJSON bool
}

func (c *versionCmd) run(cmd *cobra.Command, _ []string) error {
	if !c.isJSON {
		root := cmd.Root()
		root.SetArgs([]string{"--version"})
		_ = root.Execute()
		return nil
	}

	details, err := versionDetailsWithExtensions(ext.GetAll())
	if err != nil {
		return fmt.Errorf("failed to get version details with extensions: %w", err)
	}

	if err := json.NewEncoder(c.gs.Stdout).Encode(details); err != nil {
		return fmt.Errorf("failed to encode/output version details: %w", err)
	}

	return nil
}

func getCmdVersion(gs *state.GlobalState) *cobra.Command {
	versionCmd := &versionCmd{gs: gs}

	cmd := &cobra.Command{
		Use:    "version",
		Short:  "Show application version",
		Long:   `Show the application version and exit.`,
		Hidden: true,
		RunE:   versionCmd.run,

View on GitHub (pinned to 93accf6570)

Solutions

Run plain 'k6 version' — the non-JSON path prints the banner without iterating extension types
Rebuild k6 so the version command handles the new extension type, or drop the problematic extension from the build
Report upstream with the plain 'k6 version' output and the extension list

Example fix

# before
k6 version --json   # fails on unknown extension type
# after
k6 version           # plain output still works

Defensive patterns

Strategy: fallback

Try / catch

# Fall back to the plain banner when JSON collection fails
k6 version --json || { echo 'JSON version details failed, using plain output' >&2; k6 version; }

Prevention

Use plain 'k6 version' for quick checks
Keep the extension set consistent with the k6 core version
Report unknown-type errors upstream with the full plain version output

When it happens

Trigger: Running 'k6 version --json' on a binary whose registered extensions include a type unknown to the version command; the wrapping happens at the call site in versionCmd.run.

Common situations: Custom xk6 builds after adding a new extension kind; using --json to debug extension loading and hitting the classification failure.

Related errors

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/8f25788ea92c4bf6. Report an issue: GitHub.