Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.110.0-insider (0366405)
• OS Version: macOS 26.1 (Build 25B78)

Steps to Reproduce:

1. Open the integrated terminal in VS Code Insiders.
2. Use fish as the integrated terminal shell (fish at /opt/homebrew/bin/fish).
3. Run sleep 100 (also seen with top).
4. Press Ctrl+C.

Expected:

sleep is interrupted (SIGINT) and the shell prompt returns.

Actual:

The process keeps running, and the terminal prints something like [99;5u (sometimes repeated).

Additional Information:

• Only reproduces with fish (fish 4.4.0). If I switch the integrated terminal profile to zsh, Ctrl+C works normally.
• Outside VS Code, Ctrl+C interrupts as expected in fish (Ghostty and macOS Terminal).
• $TERM:
  • VS Code: xterm-256color
  • Ghostty: xterm-ghostty
  • macOS Terminal: xterm-256color (Ctrl+C works)
• Ctrl+C also does nothing at the fish prompt (no running command).
• Disabling shell integration (terminal.integrated.shellIntegration.enabled: false) does not change the behavior.
• Reproducible with fish --no-config.
• fish_key_reader prints bind ctrl-c 'do something' in both VS Code and Ghostty.
• [99;5u looks like a kitty keyboard protocol "CSI u" sequence for Ctrl+C.

Repro videos: