The sync resolvers (`confirm_clear`, `rank_open_tasks`, and the brainstorm chain) run on a worker thread via `anyio.to_thread.run_sync`, where they iterate the module-global `tasks_by_id` while the event-loop thread stays free to mutate it (`add_task_record` inserts, `clear_done` pops) — a mutation landing mid-iteration raises `RuntimeError("dictionary changed size during iteration")` and fails the whole `tools/call`. Snapshot with `list(tasks_by_id.values())` before iterating, or declare the re

log_info holds warnings.catch_warnings() across the awaited ctx.log(...) call; catch_warnings() saves/restores the process-global warnings.filters and is not task-safe, so two overlapping tool calls (easy over streamable HTTP, where every mutating tool logs) can interleave enter/exit non-LIFO and permanently leak the ignore filter into the global filter list. Since this is a reference example that teaches patterns, install the filter once at module import — warnings.filterwarnings("ignore", cate