XTLS/Xray-core · error

failed to write response header

Error message

failed to write response header

What it means

Error "failed to write response header" thrown in XTLS/Xray-core.

Source

Thrown at proxy/vless/encoding/encoding.go:148

		return nil, nil, nil, isfb, errors.New("invalid request version")
	}
}

// EncodeResponseHeader writes encoded response header into the given writer.
func EncodeResponseHeader(writer io.Writer, request *protocol.RequestHeader, responseAddons *Addons) error {
	buffer := buf.StackNew()
	defer buffer.Release()

	if err := buffer.WriteByte(request.Version); err != nil {
		return errors.New("failed to write response version").Base(err)
	}

	if err := EncodeHeaderAddons(&buffer, responseAddons); err != nil {
		return errors.New("failed to encode response header addons").Base(err)
	}

	if _, err := writer.Write(buffer.Bytes()); err != nil {
		return errors.New("failed to write response header").Base(err)
	}

	return nil
}

// DecodeResponseHeader decodes and returns (if successful) a ResponseHeader from an input stream.
func DecodeResponseHeader(reader io.Reader, request *protocol.RequestHeader) (*Addons, error) {
	buffer := buf.StackNew()
	defer buffer.Release()

	if _, err := buffer.ReadFullFrom(reader, 1); err != nil {
		return nil, errors.New("failed to read response version").Base(err)
	}

	if buffer.Byte(0) != request.Version {
		return nil, errors.New("unexpected response version. Expecting ", int(request.Version), " but actually ", int(buffer.Byte(0)))
	}

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at proxy/vless/encoding/encoding.go:148 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/ea1196055f5a67b0. Report an issue: GitHub.