github/github-mcp-server · error

failed to parse API host: %w

Error message

failed to parse API host: %w

What it means

utils.NewAPIHost rejected cfg.Host: the string could not be parsed and normalized into the REST/GraphQL/upload/raw endpoint set. Hosts must be parseable URLs with a scheme - the dotcom constant or a GHES base URL.

Source

Thrown at pkg/http/server.go:130

	var slogHandler slog.Handler
	var logOutput io.Writer
	if cfg.LogFilePath != "" {
		file, err := os.OpenFile(cfg.LogFilePath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
		if err != nil {
			return fmt.Errorf("failed to open log file: %w", err)
		}
		logOutput = file
		slogHandler = slog.NewTextHandler(logOutput, &slog.HandlerOptions{Level: slog.LevelDebug})
	} else {
		logOutput = os.Stderr
		slogHandler = slog.NewTextHandler(logOutput, &slog.HandlerOptions{Level: slog.LevelInfo})
	}
	logger := slog.New(slogHandler)
	logger.Info("starting server", "version", cfg.Version, "host", cfg.Host, "lockdownEnabled", cfg.LockdownMode, "readOnly", cfg.ReadOnly, "insidersMode", cfg.InsidersMode)

	apiHost, err := utils.NewAPIHost(cfg.Host)
	if err != nil {
		return fmt.Errorf("failed to parse API host: %w", err)
	}
	hostType, err := utils.ParseHostType(cfg.Host)
	if err != nil {
		return fmt.Errorf("failed to classify API host: %w", err)
	}

	repoAccessOpts := []lockdown.RepoAccessOption{
		lockdown.WithLogger(logger.With("component", "lockdown")),
	}
	if cfg.RepoAccessCacheTTL != nil {
		repoAccessOpts = append(repoAccessOpts, lockdown.WithTTL(*cfg.RepoAccessCacheTTL))
	}

	featureChecker := createHTTPFeatureChecker(cfg.EnabledFeatures, cfg.InsidersMode)

	obs, err := observability.NewExporters(logger, metrics.NewNoopMetrics())
	if err != nil {
		return fmt.Errorf("failed to create observability exporters: %w", err)

View on GitHub (pinned to 0ea1f775a7)

Solutions

1. Use https://api.github.com for dotcom, or the full https base URL of the GHES instance
2. Ensure the scheme is present and there is no stray path, query, or whitespace
3. Validate candidate host strings with utils.NewAPIHost in a smoke test before deploying

Example fix

// before
cfg.Host = "github.example.com"

// after
cfg.Host = "https://github.example.com"

u, err := url.Parse(cfg.Host)
if err != nil || u.Scheme == "" || u.Host == "" {
	return fmt.Errorf("host must be an absolute URL like https://api.github.com, got %q", cfg.Host)
}

When it happens

Trigger: Passing a bare hostname without a scheme (github.example.com), a URL with unexpected path/query components, control characters, or otherwise malformed URL syntax.

Common situations: Misconfigured GITHUB_API_URL or host flag values; copy-paste with trailing punctuation or whitespace; switching from hostname-style config to URL-style config.

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

• failed to get base REST URL: %w
• failed to create default API host: %w
• failed to classify API host: %w
• authentication required: set GITHUB_PERSONAL_ACCESS_TOKEN, c
• GitHub App authentication and OAuth login (--oauth-client-id

AI-assisted analysis of github/github-mcp-server@0ea1f775a7 (2026-08-15). Data as JSON: /api/errors/f66234968dd94338. Report an issue: GitHub.