Plan mode

We've also added GPT-5-Codex Mini, and brought back Opus 4.1.

Improvements

• Add animation for chat titles
• Add archive on merge setting
• Add a copy path button and ⌘⇧C shortcut

Fixes

• Fix Linear attachments being sent to the wrong chat
• Fix file paths with slugs not rendering properly
• Recent files in the file picker are now scoped to the repository