mastra-ai/mastra · info · Error

Authentication for MCP server ${serverName} was cancelled.

Error message

Authentication for MCP server ${serverName} was cancelled.

What it means

Plain Error thrown by the throwIfAborted checkpoint inside runAuthorizationFlow. When an OAuth authorization flow is started for a server, an AbortController is stored; if cancelAuth (or disconnect) aborts it, subsequent checkpoints throw this message to unwind the flow instead of leaving it waiting on the callback code.

Source

Thrown at packages/mcp/src/client/configuration.ts:874

  /**
   * OAuth authorization state of a configured server.
   *
   * Returns `undefined` for servers without an authProvider and for servers
   * that have not attempted a connection yet.
   */
  public getServerAuthState(serverName: string): MCPServerAuthState | undefined {
    return this.mcpClientsById.get(serverName)?.authState;
  }

  private async runAuthorizationFlow(serverName: string, options?: { timeoutMs?: number }): Promise<void> {
    // Register the abort controller synchronously, before the first await, so a
    // cancel/disconnect during the setup phase (discovery, registration, port
    // binding) can interrupt the flow rather than letting it park on waitForCode.
    const abortController = new AbortController();
    this.authAbortControllersByServer.set(serverName, abortController);
    const throwIfAborted = () => {
      if (abortController.signal.aborted) {
        throw new Error(`Authentication for MCP server ${serverName} was cancelled.`);
      }
    };

    // Resources acquired during setup that must be released on every exit path.
    // Tracked here so the single outer finally can tear them down even if a
    // fallible setup step (session begin, port binding) throws.
    let provider: MCPOAuthClientProvider | undefined;
    let sessionStarted = false;
    let callbackServer: OAuthCallbackServer | undefined;

    // Installed before the first fallible step so the abort-controller entry,
    // provider session, and callback server never leak on an early throw.
    try {
      const config = this.getServerConfig(serverName);
      const candidateProvider = config.authProvider;
      if (!(candidateProvider instanceof MCPOAuthClientProvider)) {
        throw new Error(
          `Cannot authenticate MCP server ${serverName}: it is not configured with an MCPOAuthClientProvider.`,

View on GitHub (pinned to 75dd419e61)

Solutions

1. Treat this as an expected cancellation: catch it and skip/retry the auth flow rather than treating it as a fault.
2. If unintentional, audit code paths that call cancelAuth/disconnect for the server during setup.
3. Restart the authentication flow (call the authenticate/flow method again) once cancellation is no longer desired.
4. Check for duplicate/overlapping auth flows for the same serverName that may abort each other.

Example fix

// before
await client.authenticateServer('github'); // may throw on cancel
// after
try {
  await client.authenticateServer('github');
} catch (e) {
  if ((e as Error).message.includes('was cancelled')) return; // expected cancel
  throw e;
}

function isAuthCancelled(e: unknown): boolean {
  return e instanceof Error && e.message.includes('was cancelled');
}

try {
  await client.authenticateServer(serverName);
} catch (e) {
  if (isAuthCancelled(e)) return; // user/system cancelled: expected
  throw e;
}

When it happens

Trigger: Calling client.cancelAuthentication(serverName) or disconnecting the server while runAuthorizationFlow is mid-flight (during discovery, registration, port binding, or while waiting for the OAuth callback code).

Common situations: User cancels a browser-based login; application shuts down or times out an auth attempt; a re-authentication request supersedes an in-progress flow for the same server.

Understand the failure class

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

Related errors

• Login cancelled
• Login cancelled
• AbortError
• No OAuth authorization is pending for this server. Call conn
• Cannot authenticate MCP server ${serverName}: it is not conf

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/b4d35c2ac17fa3a2. Report an issue: GitHub.