Under the hood
System prompt can now list tools that were removed, not just added
What
The internal function that builds the system prompt's tool-context section can now describe tool removals as well as additions. It emits tool_removal entries (referencing the tool by name) ahead of any tool_addition entries, and callers now pass a list of removed tools alongside the list of added ones.
Why
This lets Claude's system prompt explicitly note when a tool has been taken away during a session, not just when one is added, which should help Claude stay accurate about which tools are currently available.