Cursor jumps while typing when Codex is idle, but not while Codex is working

Is this a reproducible bug?

• I confirm this is a reproducible bug, not a feature request, idea, question, contribution proposal, or direction check.
• I reproduced this bug on the version and environment reported below using the exact steps provided.

Current behavior

This is very closely related to #3050, which I reported (and got resolved) earlier.

The issue occurs when Codex is idle. When Codex is actively working, I do not see any cursor jumps.

While Codex is idle and I type in the composer, the terminal cursor briefly leaves the actual input caret and appears elsewhere in the Codex UI before returning.

However, with Astra enabled whimsy=true, the problem becomes significantly more noticeable. Since the Astra input area contains moving animations, the cursor appears to briefly jump to different positions rather than repeatedly jumping to the same fixed location.

I have attached three screen recordings: Astra (whimsy=true), Codex idle: cursor jumping occurs and is more noticeable because the apparent cursor position changes.

https://github.com/user-attachments/assets/65eef87a-53c8-44be-8087-60324aad03d8

Astra (whimsy=true), Codex working: cursor in correct place.

https://github.com/user-attachments/assets/7c7e8ad5-bff4-4f55-94ce-8a465375e27c

5.6-Sol (whimsy=false), Codex idle: cursor jumping occurs and but to one and the same place.

https://github.com/user-attachments/assets/26871e65-21bc-4f23-84be-fc62208da521

The last recording suggests that Astra itself is not causing the issue, since the Astra animation is still running while Codex is working and the cursor remains stable.

Expected behavior

The terminal cursor should remain at the actual input caret while typing, regardless of the Astra animation state or whether Codex is idle.

Reproduction

Start Herdr. Run Codex CLI in a pane. Enable Astra / whimsy=true. Wait until Codex is idle. Type continuously in the Codex composer. Observe the cursor briefly jumping away from the input caret into different parts of the animated area. Start a Codex task so Codex is actively working. Continue typing while it is working. The cursor now remains stable.

Impact

The issue is distracting while typing and makes the input feel unstable, since the cursor briefly appears to jump away from the actual caret.

With Astra enabled, it is more noticeable than the behavior in #3050 because the cursor can appear in different parts of the animated input area rather than briefly jumping to one fixed location.

Environment

• Herdr version: v0.9.0-preview.2026-09-16-2c29fb29e302
• Update channel: Preview
• Operating system: Windows 11
• Terminal: Windows Terminal
• Shell, if relevant: PowerShell
• Relevant config, if any: Default
• Codex CLI version: 0.154.0
• Codex UI: Astra / whimsy=true