Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
System PromptArea: what it touches
Internal ChangesKind: in v2.1.275,
Internal ChangesSection of the release
What
When Claude Code builds the system prompt used for analyzing context usage, a custom system prompt string is now passed through a new splitSystemPromptAtBoundary() helper instead of being included as one single block.
Why
Splitting the prompt at a boundary allows it to be broken into multiple segments for prompt caching (where Anthropic's API can reuse unchanged parts of a prompt across requests instead of reprocessing them), which can make repeated requests with a custom system prompt more efficient.
