What causes "Failed to get format of " in XTLS/Xray-core?

Failed to get format of

Error message

Failed to get format of

What it means

Error "Failed to get format of " thrown in XTLS/Xray-core.

Source

Thrown at core/config.go:128

	switch v := input.(type) {
	case cmdarg.Arg:
		files := make([]*ConfigSource, len(v))
		hasProtobuf := false
		for i, file := range v {
			var f string

			if formatName == "auto" {
				if file != "stdin:" {
					f = GetFormat(file)
				} else {
					f = "json"
				}
			} else {
				f = formatName
			}

			if f == "" {
				return nil, errors.New("Failed to get format of ", file).AtWarning()
			}

			if f == "protobuf" {
				hasProtobuf = true
			}
			files[i] = &ConfigSource{
				Name:   file,
				Format: f,
			}
		}

		// only one protobuf config file is allowed
		if hasProtobuf {
			if len(v) == 1 {
				return configLoaderByName["protobuf"].Loader(v)
			} else {
				return nil, errors.New("Only one protobuf config file is allowed").AtWarning()
			}

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at core/config.go:128 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/5dff6fdfb104389f. Report an issue: GitHub.