change IME composing handling order to support implicitly confirming IME

[sters]

Problem

When using IME with Japanese in the terminal panel, implicitly confirming IME does not work properly.

Environment

• MacOS 26.2
• Wave Terminal 0.13.1 (202512170503)
• Google Japanese IME 2.32.5990

Step to reproduce

1. Input てすと
2. Input Tab (or Space)
3. IME changes the status to confirming (showing some candidates) and the text changes to テスト
4. Input next chars like あ
5. IME closes candidates for てすと
   • Expected: Confirm テスト and continue with next chars composition
   • Actual: テスト is lost, only next chars composition continues

Cause

I added some logs and check the behavior, the event triggering order seems complicated.

• When explicitly confirming IME (Input Enter)
  • compositionend -> handleTermData
• When implicitly confirming IME (Input Tab + Input next char)
  • compositionend -> compositionstart -> handleTermData

DEMO

Current	This PR	Reference (Chrome's textarea)
current.mp4	updated.mp4	reference.mp4

Note

I'm not familiar with other CJK languages and IME itself. There may be patterns I'm unaware of.

[CLAassistant]

All committers have signed the CLA.

[coderabbitai]

Walkthrough

The change reworks IME input handling in TermWrap.handleTermData by replacing an early composition block with a time-windowed deduplication mechanism. A 50-millisecond dedup window now permits the first data after composition ends, even if a new composition has started, while blocking duplicate inputs from the same window (such as from Capslock or input method switches). An additional guard was added to explicitly prevent intermediate composition updates from being transmitted to the terminal handler.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: reworking IME handling to support implicit IME confirmation when composition order changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The pull request description clearly explains the IME composition handling problem with Japanese input, including reproduction steps, root cause analysis, and the PR's solution.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

frontend/app/view/term/termwrap.ts (1)

625-652: IME dedup logic works for desktop but lacks mobile/iOS fallback for Hangul composition events.

The 50ms dedup window is appropriate for desktop CJK IMEs (Pinyin, Japanese), though timing varies across implementations. However, a critical gap exists: iOS and other mobile platforms do not emit composition events for Hangul/Korean input—instead, input arrives via beforeinput events. The current implementation will silently fail to handle Korean input on iOS.

To address this:

1. Add beforeinput fallback handling for platforms where composition events don't fire. Detect IME input via inputType values (e.g., "insertCompositionText") and use that as a fallback to capture Korean input on mobile.

2. Extract IMEDedupWindowMs as a class-level constant for visibility and future configurability.

3. Test across platforms and IME implementations: Pinyin, Japanese (Mozc/Anthy), Hangul on desktop (Chrome, Firefox, Safari) and mobile (iOS Safari, Android Chrome).

📜 Review details

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 31a8714 and 0a9036e.

📒 Files selected for processing (1)

• frontend/app/view/term/termwrap.ts

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: merge-gatekeeper

🔇 Additional comments (1)

frontend/app/view/term/termwrap.ts (1)

654-661: LGTM - Guard placement is correct.

Placing this guard after the dedup check ensures that:

1. Confirmed text from a recent compositionend is allowed through (even if a new composition has started)
2. Intermediate composition updates during active composition are blocked

The logic flow is sound.