[Bug] CLAUDE_CODE_NO_FLICKER=1 swallows Ctrl+J keybinding for chat:newline in tmux

Ctrl+J bound to chat:newline in keybindings.json stopped working the moment I set CLAUDE_CODE_NO_FLICKER=1. Remove the env var, Ctrl+J works again. Put it back, gone.

The alt-screen renderer is eating the keystroke before the keybinding system gets a chance to see it. Ctrl+J (ASCII 0x0A, line feed) is probably being consumed as a cursor/scroll control in the alternate screen buffer.

Repro

1. Add "CLAUDE_CODE_NO_FLICKER": "1" to settings.json env
2. Bind ctrl+j to chat:newline in keybindings.json:

{
  "bindings": [
    {
      "context": "Chat",
      "bindings": {
        "ctrl+j": "chat:newline"
      }
    }
  ]
}

1. Launch Claude Code inside tmux
2. Press Ctrl+J in the input box. Nothing happens.
3. Remove CLAUDE_CODE_NO_FLICKER, restart. Ctrl+J inserts a newline again.

Environment

• Claude Code 2.1.90
• tmux 3.6a
• Linux 6.17.13-2-pve
• zsh

Note

Shift+Enter also doesn't work in tmux (long-standing tmux limitation with modifier key passthrough), so Ctrl+J is the only reliable newline binding here. This effectively makes NO_FLICKER mode unusable for tmux users who need multi-line input.

Related

• #42501 (same class of bug, Shift+Enter broken in Warp with NO_FLICKER)