GPT 5.4 model support — Added OpenAI's latest GPT 5.4 model as the new default for Codex runtime, replacing GPT-5.3 Codex
Copy button in text selection popover — Select any text in chat to quickly copy it with a new Copy icon button
Improvements & Fixes
Instant new chat creation — Creating a new sub-chat is now instant (optimistic UI update) instead of waiting for DB insert, with full rollback on failure
Double-click guard on new chat — Prevents duplicate sub-chats from rapid Cmd+T or double-clicking the new chat button
Race condition safety net — If a message is sent before the sub-chat row is persisted, the backend now auto-creates it instead of silently failing
Nested session error fix — Fixed "Claude Code cannot be launched inside another session" error when running the dev build from a Claude Code terminal
Changelog URL fix — Updated changelog links to point to the correct URL