Left Shift key does not trigger input mode switch

[rayzhangxql-design]

Pre-submit Checks

• I have searched Warp bugs and there are no duplicates
• I have searched Warp known issues page and my issue is not there
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Describe the bug

Bug Report

Environment

• OS: Ubuntu 26.04 LTS (Resolute Raccoon)
• Warp Version: [请填写你的版本]
• Desktop Environment: [请填写, e.g. GNOME 47 / KDE Plasma]
• Input Method: [请填写, e.g. IBus / Fcitx5]

Problem 1: Left Shift key does not trigger input mode switch

Description:
On Ubuntu, pressing Left Shift to switch input mode (e.g., Chinese ↔ English) does not work in Warp. The same keyboard shortcut works correctly in the system default terminal (GNOME Terminal / Bash).

Steps to Reproduce:

1. Install an input method framework on Ubuntu (IBus or Fcitx5) with Chinese input configured
2. Set Left Shift as the input mode switch shortcut (this is the default in many Ubuntu Chinese input setups)
3. Open Warp terminal
4. Press Left Shift to switch between input modes
5. Nothing happens — the input mode does not switch

Expected Behavior:
Left Shift should toggle between input modes, just like it does in other terminals (GNOME Terminal, Alacritty, Kitty, etc.).

Actual Behavior:
Warp does not respond to the Left Shift key for input mode switching.

---

Problem 2: Chinese characters rendered incorrectly (garbled/bloated)

Description:
Chinese characters are not displayed with the correct font in Warp. They appear distorted or "bloated" (加花), not rendering properly.

Steps to Reproduce:

1. Open Warp terminal on Ubuntu
2. Type or paste Chinese characters (e.g., 你好世界)
3. Observe the rendering

Expected Behavior:
Chinese characters should render clearly with the configured font (e.g., Noto Sans CJK, WenQuanYi Micro Hei, or any system CJK font).

Actual Behavior:
Chinese characters appear garbled/distorted, not matching the expected font rendering.

Additional Notes

• Both issues are specific to Warp. Other terminal emulators (GNOME Terminal, Alacritty, Kitty, Ghostty) work correctly on the same system.
• This affects daily workflow for Chinese users on Ubuntu.

To reproduce

Steps to Reproduce:

1. Install an input method framework on Ubuntu (IBus or Fcitx5) with Chinese input configured
2. Set Left Shift as the input mode switch shortcut (this is the default in many Ubuntu Chinese input setups)
3. Open Warp terminal
4. Press Left Shift to switch between input modes
5. Nothing happens — the input mode does not switch

Expected behavior

No response

Screenshots, videos, and logs

No response

Operating system (OS)

Linux

Operating system and version

Ubuntu 26.04 LTS

Shell Version

No response

Current Warp version

No response

Regression

Yes, this bug started recently or with an X Warp version

Recent working Warp date

No response

Additional context

No response

Does this block you from using Warp daily?

Yes, this issue prevents me from using Warp daily.

Is this an issue only in Warp?

Yes, I confirmed that this only happens in Warp, not other terminals.

Warp Internal (ignore): linear-label:b9d78064-c89e-4973-b153-5178a31ee54e

None

[oz-for-oss]

@rayzhangxql-design

Here's what I found while triaging this issue:

This looks related to Linux IME/input handling and CJK fallback/font rendering rather than a shell-specific issue. I found related reports (#7971, #5279, #3505), but not enough clear duplicate matches to mark this issue as a duplicate yet.

I have a few follow-up questions before I can narrow this down:

1. Can you attach a short screen recording showing Left Shift failing to switch input mode in Warp and working in another terminal on the same machine?
2. Which input method framework is configured for the Left Shift shortcut: IBus, Fcitx5, or something else?

Reply in-thread with those details and the triage workflow will automatically re-evaluate the issue and update the diagnosis, labels, and next steps.

Maintainer details

I concluded that linux IME/input handling bug report where Left Shift does not switch Chinese input mode in Warp and CJK terminal text renders incorrectly; reproduction is plausible but key environment details are missing..

Triage summary

This appears to be a Linux-specific input/rendering bug affecting Chinese IME workflows in Warp. The report contains two symptoms that may have separate underlying fixes: Left Shift does not switch the configured input mode, and Chinese characters render with an incorrect or distorted fallback font.

Reproducibility

Reproducibility is medium. The report includes a concrete IME shortcut setup and says the behavior is Warp-specific compared with GNOME Terminal, Alacritty, Kitty, and Ghostty, but the exact Warp version, input method framework, desktop environment/display server, and screenshots or recording are missing.

Likely area

The input-mode failure likely belongs in Warp's Linux/winit input path rather than shell integration. Relevant code paths include modifier-only keyboard event conversion and IME event dispatch in crates/warpui/src/windowing/winit/event_loop/mod.rs and crates/warpui/src/windowing/winit/event_loop/key_events.rs, then terminal/editor event handling in app/src/terminal/block_list_element.rs and app/src/terminal/view.rs.

The CJK rendering symptom likely belongs to terminal rendering/font fallback: app/src/terminal/grid_renderer.rs, app/src/terminal/grid_renderer/cell_glyph_cache.rs, crates/warpui_core/src/fonts.rs, crates/warpui/src/windowing/winit/fonts.rs, and crates/warpui/src/windowing/winit/fonts/linux.rs. The code currently relies on fontconfig/cosmic-text fallback for Linux glyph selection; a mismatch between the configured terminal font and the chosen fallback CJK font could explain distorted or unexpected glyph shapes, but this needs visual confirmation.

Related existing issues

I found related open reports, but fewer than two clear duplicates of this exact Left Shift + Ubuntu IME-switch symptom, so I am not marking this as a duplicate. Related issues include #7971 for Fcitx5 input switching via Ctrl+Space, #5279 for Fcitx5/Rime Chinese input not committing into Warp, and #3505 for Chinese character rendering problems.

Missing details

The two highest-value missing details are the exact input method framework used for the Left Shift shortcut and visual evidence of the rendering/input behavior. The exact Warp version is also missing and would help confirm whether this is tied to a recent regression, but I am keeping the public follow-up questions limited to the two most actionable items.

Question reasoning

1. Can you attach a short screen recording showing Left Shift failing to switch input mode in Warp and working in another terminal on the same machine? — The report includes both an input behavior issue and a visual CJK rendering issue; a recording would confirm the exact UI/input symptom and whether both problems occur in the same focused surface.
2. Which input method framework is configured for the Left Shift shortcut: IBus, Fcitx5, or something else? — Warp's Linux IME behavior can differ by framework/backend, and the issue body left this field as a placeholder.

This is my automated analysis and may be incorrect. A maintainer will verify the details.

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[linwanlong]

After the version update, I encountered this same annoying problem again.

Video:

2026-05-22.15-48-51.webm

[rayzhangxql-design]

@oz-for-oss[bot]

补充信息如下：

Environment

• OS: Ubuntu 26.04 LTS (Resolute Raccoon)
• Desktop Environment: GNOME
• Input Method Framework: Fcitx5
• Warp Version: [待确认]

Screen Recording

Attached screen recording showing:

1. Left Shift failing to switch input mode in Warp
2. Left Shift working correctly in GNOME Terminal on the same machine

[录屏文件已上传]

Please re-evaluate the issue with this additional information.

[rayzhangxql-design]

Screen recording attached below.

[oz-for-oss]

@rayzhangxql-design

Here's what I found while triaging this issue:

The added GNOME/Fcitx5 recording narrows this to Warp’s Linux input-method/key handling path; the Chinese rendering symptom should stay routed with terminal rendering/font fallback as a related secondary symptom.

I have a few follow-up questions before I can narrow this down:

1. Which exact Warp version/channel are you using when Left Shift fails?
2. Is the GNOME session running under Wayland or X11 when this reproduces?

Reply in-thread with those details and the triage workflow will automatically re-evaluate the issue and update the diagnosis, labels, and next steps.

Maintainer details

I concluded that linux GNOME/Fcitx5 regression where Left Shift no longer toggles the input method in Warp, with a secondary CJK rendering/font fallback symptom..

Triage summary

The added GNOME/Fcitx5 recording makes the Left Shift input-mode switch failure plausible and Warp-specific on Linux. The CJK rendering report appears related but likely belongs to the terminal rendering/font fallback path rather than the same key-event failure, so both terminal input and UI/rendering routing are appropriate.

Likely area

• Linux window/input event handling for IME modifier events.
• Terminal marked-text and typed-character handling for IME commits.
• Linux font fallback and glyph rendering for CJK display.

Evidence

• Reporter states Left Shift toggles Fcitx5 in GNOME Terminal but not Warp on the same machine.
• Follow-up provides GNOME + Fcitx5 context and screen-recording evidence.
• crates/warpui/src/windowing/winit/event_loop/mod.rs handles standalone modifier KeyboardInput events as ModifierKeyChanged before normal keydown conversion, while handle_ime_event separately forwards IME commit/preedit events.
• app/src/terminal/view.rs updates marked text only when FeatureFlag::ImeMarkedText is enabled and writes committed typed characters through the terminal/input path.
• crates/warpui/src/windowing/winit/fonts.rs and crates/warpui/src/windowing/winit/fonts/linux.rs use fontconfig-backed fallback loading for non-Windows glyphs, which is the likely area for the garbled/bloated Chinese rendering symptom.

Duplicate check

#11526 is an exact copy, but it was closed as a duplicate of this issue, so #11524 should remain the canonical thread. Open issues #5279, #7971, #5606/#6877, and #320 are related Linux/IME reports but differ in shortcut, platform/session assumptions, or specific symptom, so this issue is not being marked as a duplicate.

Remaining ambiguity

Warp version/channel and GNOME session type are still missing. Those details matter because the report is framed as a recent regression and Linux IME behavior can differ between Wayland and X11.

Question reasoning

1. Which exact Warp version/channel are you using when Left Shift fails? — The report says this started after a recent update, so the exact build is needed to identify the regression window and decide whether the current stable build is still affected.
2. Is the GNOME session running under Wayland or X11 when this reproduces? — Warp's Linux IME/input behavior can differ between Wayland and X11, and that distinction materially affects the likely owner and repro setup.

This is my automated analysis and may be incorrect. A maintainer will verify the details.

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[oz-for-oss]

@rayzhangxql-design

Here's what I found while triaging this issue:

The added GNOME/Fcitx5 recording makes this look like a Warp-specific Linux IME integration bug rather than expected shortcut behavior. Related IME/CJK reports exist (#7971, #5279, #9012), but #11526 was closed as a duplicate of this issue, so I am not marking this thread as a duplicate.

I have a few follow-up questions before I can narrow this down:

1. What exact Warp version/channel/build are you using when Left Shift fails?
2. Is the GNOME session running on Wayland or X11 when you reproduce this?

Reply in-thread with those details and the triage workflow will automatically re-evaluate the issue and update the diagnosis, labels, and next steps.

Maintainer details

I concluded that linux GNOME/Fcitx5 reports and the attached recording point to a Warp-specific IME/input integration bug where Left Shift does not trigger input-mode switching, with a related CJK font/rendering symptom that still needs exact build and display-session details..

Triage summary

The added GNOME/Fcitx5 context and screen-recording reference make this look like a Warp-specific Linux IME/input bug rather than expected shortcut behavior. The primary symptom is that a modifier-only IME shortcut (Left Shift) does not switch Chinese/English input mode in Warp while it works in GNOME Terminal on the same machine; the secondary symptom is incorrect CJK glyph rendering.

Current assessment

• Reproducibility: medium. The issue has clear steps, a specific Linux desktop/input-method stack, confirmation against another terminal, a second affected user, and a recording reference. The exact Warp build/channel and Linux display protocol are still missing.
• Likely owner areas: terminal input and the UI framework/windowing layer, with shell-terminal involvement for CJK output rendering.
• Likely code path: the winit event loop converts keyboard, modifier, and IME events, dispatches Ime::Preedit/Ime::Commit, and updates the active IME cursor position. Modifier-only keys such as Shift are handled separately from normal text-producing keydown events, which is relevant for Fcitx5 shortcuts that use Shift as an input-mode toggle.
• Rendering angle: Linux font loading/fallback uses fontconfig and terminal glyph rendering, so the CJK garbling/bloating may be related but needs separate visual/font details before assigning a narrower root cause.

Duplicate check

I checked the open issue set and recent closed issues. Related IME/CJK reports include #7971, #5279, and #9012, but they do not provide two matching canonical duplicates for the exact Left Shift + Linux/Fcitx5 behavior. #11526 is an exact recent match, but it was closed by the reporter as a duplicate of this issue, so this issue should remain the active thread rather than being marked duplicate.

Question reasoning

1. What exact Warp version/channel/build are you using when Left Shift fails? — The report says this is a regression after an update, but the current Warp build is still pending; the exact build materially affects bisecting and whether this is already fixed in a newer release.
2. Is the GNOME session running on Wayland or X11 when you reproduce this? — Warp's Linux keyboard and IME behavior depends on the winit/windowing backend, and the report does not specify the display protocol.

This is my automated analysis and may be incorrect. A maintainer will verify the details.

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