What causes "failed to parse plugin %q (%v) version %q: %v" in hashicorp/nomad?

Make the plugin return a valid semver string in PluginInfoResponse.PluginVersion (e.g. "0.1.0").

failed to parse plugin %q (%v) version %q: %v

Error message

failed to parse plugin %q (%v) version %q: %v

What it means

After PluginInfo() succeeds, fingerprintPlugin() parses i.PluginVersion with hashicorp/go-version's version.NewVersion. This error is returned when the version string reported by the plugin is not a valid semver-compatible version. The plugin is skipped and cannot be registered because its version cannot be compared against constraints.

Source

Thrown at helper/pluginutils/loader/init.go:382

	raw, err := rpcClient.Dispense(base.PluginTypeBase)
	if err != nil {
		return nil, err
	}

	// Cast the plugin to the base type
	bplugin := raw.(base.BasePlugin)

	// Retrieve base plugin information
	i, err := bplugin.PluginInfo()
	if err != nil {
		return nil, fmt.Errorf("failed to get plugin info for plugin %q: %v", info.exePath, err)
	}
	info.baseInfo = i

	// Parse and set the plugin version
	v, err := version.NewVersion(i.PluginVersion)
	if err != nil {
		return nil, fmt.Errorf("failed to parse plugin %q (%v) version %q: %v",
			i.Name, info.exePath, i.PluginVersion, err)
	}
	info.version = v

	// Detect the plugin API version to use
	av, err := l.selectApiVersion(i)
	if err != nil {
		return nil, fmt.Errorf("failed to validate API versions %v for plugin %s (%v): %v", i.PluginApiVersions, i.Name, info.exePath, err)
	}
	if av == "" {
		l.logger.Warn("skipping plugin because supported API versions for plugin and Nomad do not overlap", "plugin", i.Name, "path", info.exePath)
		return nil, nil
	}
	info.apiVersion = av

	// Retrieve the schema
	schema, err := bplugin.ConfigSchema()
	if err != nil {

View on GitHub (pinned to 482b49bf1a)

Solutions

Make the plugin return a valid semver string in PluginInfoResponse.PluginVersion (e.g. "0.1.0").
Remove leading issues: 'v' prefix is allowed, but no extra dots/dashes; validate with a semver checker.
Rebuild and redeploy the plugin with the corrected version string.
If you cannot patch the plugin, remove it from plugin_dir to stop the error.
Confirm with the plugin vendor that the released binary reports a semver PluginVersion.

Example fix

// before
return &base.PluginInfoResponse{..., PluginVersion: "dev"}, nil
// after
return &base.PluginInfoResponse{..., PluginVersion: "0.1.0"}, nil

Defensive patterns

Strategy: validation

Validate before calling

// validate the plugin's reported version is semver before deploying
import "github.com/hashicorp/go-version"
_, err := version.NewVersion(pluginInfo.PluginVersion)
if err != nil {
	log.Fatalf("plugin version %q is not semver: %v", pluginInfo.PluginVersion, err)
}

Try / catch

// Go: detect and isolate the bad plugin
if _, err := loader.Load(); err != nil {
	if strings.Contains(err.Error(), "failed to parse plugin") {
		log.Printf("skipping plugin with invalid version string: %v", err)
	}
}

Prevention

Always set PluginVersion to a valid semver string (e.g. "1.2.0"); never "dev" or empty.
Add a CI check that asserts the plugin's PluginInfoResponse version parses via go-version.
Use a shared version constant in the plugin source to avoid typos.
Pin hashicorp/go-version in the plugin to a version consistent with Nomad's.

When it happens

Trigger: version.NewVersion(i.PluginVersion) fails because the plugin's PluginInfoResponse.PluginVersion is empty, or contains a non-semantic string like "dev", "v1", "1.0.0-beta+" (malformed), or free-form text.

Common situations: Hand-written plugins that set PluginVersion to something like "latest" or leave it empty; plugins using non-semver internal versioning schemes; typos such as "0.1.0.1" (four segments).

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/e1e112f9724604fe. Report an issue: GitHub.