Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.252,
Internal ChangesSection of the release
The token-counting helpers for MCP tools, built-in tools, skills, and slash commands (dA, formerly TA) now accept a recordedDescription map sourced from the last prompt snapshot, so re-analysis of context usage (e.g. /context) reuses the exact tool description text actually sent to the model instead of recomputing it.
The flag server returned off for the account this site reads and for the anonymous baseline. A reading of off cannot rule out a rollout these two readings sit outside of.
This account: off · anonymous baseline: off · compiled default in v2.1.252: not a boolean we can read
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 sinceA 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-5-1see the edit
Confirmed sinceAnthropic'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-cachingsee the edit
What has happened since
Flag reading movedThe flag server now returns on for tengu_carved_slate, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading movedThe flag server now returns nothing at all, having stopped carrying it for tengu_carved_slate, read as this account.A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
