failed to authenticate websocket connection

Error message

failed to authenticate websocket connection

What it means

Returned by processWSConn when the very first websocket ReadMessage fails, meaning the client never delivered the initial authentication line — typically a network drop, an immediate disconnect, or a non-websocket client hitting the endpoint. The underlying read error is wrapped for context.

Source

Thrown at server/handlers.go:93

		err = server.processWSConn(ctx, conn)

		switch err {
		case ctx.Err():
			closeReason = "cancelation"
		case webtty.ErrSlaveClosed:
			closeReason = server.factory.Name()
		case webtty.ErrMasterClosed:
			closeReason = "client"
		default:
			closeReason = fmt.Sprintf("an error: %s", err)
		}
	}
}

func (server *Server) processWSConn(ctx context.Context, conn *websocket.Conn) error {
	typ, initLine, err := conn.ReadMessage()
	if err != nil {
		return errors.Wrapf(err, "failed to authenticate websocket connection")
	}
	if typ != websocket.TextMessage {
		return errors.New("failed to authenticate websocket connection: invalid message type")
	}

	var init InitMessage
	err = json.Unmarshal(initLine, &init)
	if err != nil {
		return errors.Wrapf(err, "failed to authenticate websocket connection")
	}
	if init.AuthToken != server.options.Credential {
		return errors.New("failed to authenticate websocket connection")
	}

	queryPath := "?"
	if server.options.PermitArguments && init.Arguments != "" {
		queryPath = init.Arguments
	}

View on GitHub (pinned to a080c85cbc)

Solutions

Verify the client is a real websocket peer speaking the correct subprotocol/URL before the handshake
Check for intermediaries (proxies, load balancers) that truncate or buffer the first frame
Inspect the wrapped error (close frame, timeout, EOF) to distinguish client abort from transport failure

Defensive patterns

Strategy: try-catch

When it happens

Trigger: Thrown at server/handlers.go:93 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

Authentication and authorization failures — expired tokens, bad credentials, and missing scopes.

AI-assisted analysis of yudai/gotty@a080c85cbc (2026-09-02). Data as JSON: /api/errors/79780ea23b92c64b. Report an issue: GitHub.