Keep a Claude side chat on its parent's request prefix
A Claude side chat now sends the same tools and system prompt as its parent, so it reuses the parent's prompt cache.
A Claude side chat used to cut its tool list to Read, Glob and Grep and put a side-chat note in its system prompt. Both sit before the conversation in Claude’s cached prefix, so a changed prefix risked missing the cache. A side chat now keeps its parent’s tools and system prompt, and the note travels only in the message.
Side chats stay read-only: Claude runs in dontAsk mode with only Read, Glob and Grep allowed, backed by a hook and the permission callback. Every Claude request in a folder now names that folder in its system prompt, including the first one.
Measured against Claude Code 2.1.312, a side chat wrote about 0.5K tokens to the cache instead of 2.3K. Side chats made by an earlier build drop out of the side-chat list. Codex and Pi side chats are unchanged.
Evidence
No screenshot: Backend and protocol change; nothing looks different in the app.