Shift+Enter no longer inserts newline — submits instead (regression ~June 30)

Bug Report

Description

Shift+Enter stopped inserting a newline in the chat input and now submits the message instead. This is a regression — it was working prior to approximately June 30, 2026.

Environment

• Claude Code version: 2.1.193, 2.1.200 (both affected)
• OS: macOS Tahoe 26.5.1
• Terminal (broken): Apple Terminal.app 470.2
• Terminal (working): iTerm2 3.6.11

Configuration

~/.claude/keybindings.json:

{
  "$schema": "https://www.schemastore.org/claude-code-keybindings.json",
  "$docs": "https://code.claude.com/docs/en/keybindings",
  "bindings": [
    {
      "context": "Chat",
      "bindings": {
        "shift+enter": "chat:newline"
      }
    }
  ]
}

Steps to Reproduce

1. Open Apple Terminal.app
2. Run claude
3. Focus the chat input
4. Press Shift+Enter

Expected Behavior

A newline is inserted in the chat input.

Actual Behavior

The message is submitted (same behavior as Enter).

Additional Context

• Works correctly in iTerm2 — Terminal.app-specific regression
• No macOS system updates occurred around the time of the regression
• Shell config (.zshrc) is minimal and unrelated
• ctrl+j (chat:newline default) still works correctly as a workaround in both terminals
• Broke around June 30–July 1, 2026
• Previously worked in Terminal.app before that date