Description

When using the /auth command in the Ghostty terminal, the CLI prematurely reports "cancelled by user" during the OAuth flow, preventing successful sign-in.

Steps to Reproduce

1. Open Ghostty.
2. Run gemini-cli /auth.
3. Select Option 1 (Login with Google).
4. Consent prompt appears; select "Yes".
5. Browser opens successfully for sign-in.
6. Before/during sign-in completion, the CLI reports "cancelled by user".

Technical Investigation

The issue appears to originate from the cancellationPromise in gemini-cli/packages/core/src/code_assist/oauth2.ts. This promise listens for SIGINT or 0x03 (Ctrl+C) in process.stdin.

In Ghostty, it's possible that:

• A SIGINT is triggered unexpectedly.
• Ghostty sends a sequence that is interpreted as 0x03 in process.stdin.

Relevant code snippet:

    const cancellationPromise = new Promise<never>((_, reject) => {
      sigIntHandler = () =>
        reject(new FatalCancellationError('Authentication cancelled by user.'));
      process.on('SIGINT', sigIntHandler);

      // Note that SIGINT might not get raised on Ctrl+C in raw mode
      // so we also need to look for Ctrl+C directly in stdin.
      stdinHandler = (data: Buffer) => {
        if (data.includes(0x03)) {
          reject(
            new FatalCancellationError('Authentication cancelled by user.'),
          );
        }
      };
      process.stdin.on('data', stdinHandler);
    });