Motivation

• The chat composer was disabled while the model was responding but did not restore focus to the message textarea when it became enabled again, forcing users to click the input before sending follow-ups.
• Improve UX by automatically restoring focus after a disabled->enabled transition and keep disabled-state logic consistent across input and submit controls.

Description

• Added a scoped promptInputContainerRef to the prompt area and attached it to the prompt container element.
• Introduced isInputDisabled and wasInputDisabledRef and a useEffect that detects the disabled->enabled transition and focuses the scoped textarea via querySelector when the composer becomes enabled.
• Replaced scattered disabled checks with isInputDisabled on the PromptInputTextarea and the PromptInputSubmit so the textarea and submit button remain in sync.
• Modified frontend/src/components/chat/chat-session-pane.tsx to implement the changes.

Testing

• Ran pnpm -C frontend exec biome check src/components/chat/chat-session-pane.tsx which initially reported formatting differences and failed.
• Ran pnpm -C frontend exec biome check --write src/components/chat/chat-session-pane.tsx which applied formatter fixes successfully.
• Re-ran pnpm -C frontend exec biome check src/components/chat/chat-session-pane.tsx which completed with no errors.

Codex Task

Summary by cubic

Restores focus to the chat input after the model finishes responding, so users can immediately type follow-ups. Also unifies the composer’s disabled state across the textarea and submit button.

• Bug Fixes
  • Added a scoped promptInputContainerRef and an effect to focus the textarea on a disabled→enabled transition.
  • Introduced isInputDisabled to keep the textarea and submit button in sync.

^{Written for commit c5f8a03. Summary will update on new commits.}