- /changes diffs the last turn's file snapshot (added/modified/deleted), reusing undo infra via SnapshotStack.peek() - system prompt memoized behind version counters (notebook/memory/skills/plugins/tools/workspace); hit-rate in /cost, foundation for provider caching - web_search: DuckDuckGo Lite, keyless, 5 results, SSRF-filtered, in the net set with ask permission - /search <query>: full-text grep over saved sessions incl. tool-input JSON - workspace file list re-walks at a turn boundary after writes - maxSpendPerTurn: per-turn cap stops a runaway step with a notice - /fork: branch the session at the last turn boundary, original untouched 821 tests pass, typecheck clean, build green