Constant TOOL_CHUNK_PERSIST 

const TOOL_CHUNK_PERSIST: usize = 1024;

How many tool_chunk events the broker keeps per block:<id> scope. Sized for npm-install class output (~1000 lines is typical; 1024 covers all but heavy CI builds). Each event is ~200–500 bytes, so the steady-state ceiling is ~512 KB per actively-streaming block.