caddyserver/caddy · error

unrecognized config adapter: %s

Error message

unrecognized config adapter: %s

What it means

The adapter name given via --adapter (or inferred) has no registered caddyconfig.Adapter in this binary. Stock Caddy ships the caddyfile adapter; other adapters exist only if compiled in as plugins.

Source

Thrown at cmd/main.go:206

			} else {
				// success reading default Caddyfile
				configFile = "Caddyfile"
				logger.Info("using adjacent Caddyfile")
			}
		}
	}

	if yes, err := isCaddyfile(configFile, adapterName); yes {
		adapterName = "caddyfile"
	} else if err != nil {
		return nil, "", "", err
	}

	// load config adapter
	if adapterName != "" {
		cfgAdapter = caddyconfig.GetAdapter(adapterName)
		if cfgAdapter == nil {
			return nil, "", "", fmt.Errorf("unrecognized config adapter: %s", adapterName)
		}
	}

	// adapt config
	if cfgAdapter != nil {
		adaptedConfig, warnings, err := cfgAdapter.Adapt(config, map[string]any{
			"filename": configFile,
		})
		if err != nil {
			return nil, "", "", fmt.Errorf("adapting config using %s: %v", adapterName, err)
		}
		logger.Info("adapted config to JSON", zap.String("adapter", adapterName))
		for _, warn := range warnings {
			msg := warn.Message
			if warn.Directive != "" {
				msg = fmt.Sprintf("%s: %s", warn.Directive, warn.Message)
			}
			logger.Warn(msg,

View on GitHub (pinned to 50e54ee279)

Solutions

1. Check spelling: the built-in adapter is 'caddyfile'
2. List what your binary supports; if the adapter is a plugin, rebuild with xcaddy including it
3. Confirm which binary runs: which caddy && caddy version

Example fix

# before
caddy adapt --config app.yaml --adapter yaml   # unrecognized config adapter: yaml

# after (build with the plugin, or use the built-in adapter)
xcaddy build --with github.com/caddyserver/format-awslambda  # example plugin flow
caddy adapt --config Caddyfile --adapter caddyfile

// Verify the adapter exists in this binary before using it:
if caddyconfig.GetAdapter(adapterName) == nil { return fmt.Errorf("adapter %q not compiled in; rebuild with xcaddy --with <plugin>", adapterName) }

func hasAdapter(name string) bool { return caddyconfig.GetAdapter(name) != nil }

When it happens

Trigger: Running 'caddy adapt --config x.yaml --adapter yaml' on a build without the yaml adapter plugin; misspelling 'caddyfile'; using an adapter plugin that was not compiled into the custom build actually being invoked.

Common situations: Custom xcaddy builds missing a plugin; docs referencing an adapter the installed binary lacks; PATH picking up a different caddy binary than the one built with the plugin.

Related errors

• unrecognized shell: %s
• cannot adapt config without config file (use --config)
• adapting config using %s: %v
• module %s is not a precompressor; is %T
• command short string is required

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/6682a0ea5fa7eb14. Report an issue: GitHub.