Under the hood
/context now checks fullscreen state directly instead of via a heuristic.
The /context command now decides whether to collapse detail sections by checking i.presentation === "fullscreen" directly, replacing the prior xt() heuristic function.
Names in the bundle/context
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Added since
A small documentation edit on whats-new-fable-5-1 touched a line naming /context after this was published.
To keep thinking valid across a long session, treat the conversation as append-only. Add instructions with a [mid-conversation system message](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) ([turn-s…models/fable-5-1/whats-new-fable-5-1 see the edit
Confirmed since
Anthropic's documentation has since written up /context, on How Claude Code uses prompt caching.
[Compaction](/docs/en/context-window#what-survives-compaction) replaces your message history with a summary. By design, this invalidates the conversation layer, since the next request has a new, shorter history that doesn't share a prefix …prompt-caching see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up /context, on How Claude Code uses prompt caching.