fix(desktop): prevent browser default behavior for terminal shortcuts

[onevcat]

Summary

Fix IME (Input Method Editor) input corruption after using Cmd+Left, Cmd+Right, Cmd+Backspace, or Shift+Enter shortcuts in the terminal.

Problem

When using IME to input CJK characters (Chinese, Japanese, Korean) in the terminal:

1. Type some characters, e.g., "一二三四五" (Chinese for 1-2-3-4-5)
2. Press Cmd+Left to move cursor to the beginning of the line
3. Try to type any new character
4. Bug: The input becomes corrupted - in this case, any input would result in just "五" (the last character)

As is

2026-01-27.12.43.52.mov

To be

2026-01-27.12.44.45.mov

More detail

This issue does not occur when:

• Using Ctrl+A directly (instead of Cmd+Left)
• Typing non-IME characters (English, numbers)
• Using arrow keys to move cursor character by character

Root Cause

This bug was introduced in #926 (feat(terminal): add Cmd+Arrow for cursor line navigation), which remapped shortcuts to match macOS conventions:

Shortcut	Before #926	After #926
Terminal switching	Cmd+Left/Right	Cmd+Option+Left/Right
Pane switching	Cmd+Option+Left/Right	Cmd+Shift+Left/Right
Cursor line navigation	(none)	Cmd+Left/Right

xterm.js uses a hidden <textarea> element to capture keyboard input and IME composition. When handling custom shortcuts via attachCustomKeyEventHandler:

• Returning false tells xterm to skip its default key handling
• However, it does not call event.preventDefault(), so browser default behavior still occurs
• Cmd+Left in browsers moves the textarea cursor to the beginning of the text
• This cursor movement in the hidden textarea interferes with IME's internal composition state

Solution

Add event.preventDefault() before handling the following shortcuts:

• Cmd+Left (move to line beginning)
• Cmd+Right (move to line end)
• Cmd+Backspace (delete to line beginning)
• Shift+Enter (line continuation)

This prevents the browser from manipulating the hidden textarea's cursor position while we send the appropriate control sequences to the PTY.

Testing

1. Open terminal in Superset desktop app
2. Switch to an IME (e.g., Chinese Pinyin, Japanese)
3. Type some CJK characters
4. Press Cmd+Left to jump to line beginning
5. Type more characters
6. Expected: New characters appear at cursor position normally
7. Before fix: Input is corrupted

Additional Notes

A video demonstration can be provided if needed to illustrate the bug and the fix.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds event.preventDefault() calls to four keyboard event handlers in the Terminal component (Shift+Enter, Cmd+Backspace, Cmd+Left, Cmd+Right), preventing browser default behavior when these keys are pressed while the terminal handles them.

Changes

Cohort / File(s)	Summary
Terminal keyboard event prevention apps/desktop/src/renderer/screens/main/components/WorkspaceView/ContentView/TabsContent/Terminal/helpers.ts	Added event.preventDefault() calls in four keyboard-handling branches within setupKeyboardHandler to block browser defaults for Shift+Enter, Cmd+Backspace, Cmd+Left, and Cmd+Right key combinations

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• fix(desktop): shift+enter adding stray \ characters in Claude Code #536 — Modifies Shift+Enter data handling in the terminal; this PR ensures the browser doesn't interfere with that handler.
• feat(terminal): add Cmd+Arrow for cursor line navigation #926 — Introduces Cmd+Left and Cmd+Right handlers in the same Terminal helpers file; this PR prevents default behavior for those keys.
• feat(desktop): add click-to-move cursor and selection delete for terminal #357 — Adds keyboard event handlers (onWrite, selection-delete) in the same Terminal keyboard flow that this PR protects.

Suggested reviewers

• Kitenite

Poem

🐰 Four keys pressed, defaults gone to sleep,
Cmd and Shift now secrets we shall keep,
No browser interference, just our way,
The terminal hops free, hip-hip-hooray! 🌿

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title accurately reflects the main change: adding event.preventDefault() calls to prevent browser default behavior for terminal shortcuts.
Description check	✅ Passed	The pull request description is comprehensive and well-structured, covering the problem, root cause, solution, testing steps, and additional context, exceeding template requirements.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[Kitenite]

Thanks for creating the PR, sorry I must've missed this entirely