diff --git a/src/io_pool.py b/src/io_pool.py
index ac46afa8..2d794498 100644
--- a/src/io_pool.py
+++ b/src/io_pool.py
@@ -24,9 +24,11 @@ IO_POOL_THREAD_NAME_PREFIX: str = "controller-io"
 def make_io_pool(max_workers: int = IO_POOL_MAX_WORKERS) -> ThreadPoolExecutor:
  """Create the shared AppController I/O pool.
 
- 4 worker threads, named "controller-io-N". Used for warmup, log pruning,
- disk-bound subsystem init, and any other background work that should
- not spin up its own thread.
+ 8 worker threads (per `IO_POOL_MAX_WORKERS = 8` above; bumped from 4
+ in commit 4a338486 on 2026-06-06 to relieve contention during batched
+ sims), named "controller-io-N". Used for warmup, log pruning, disk-
+ bound subsystem init, and any other background work that should not
+ spin up its own thread.
 
  Caller is responsible for shutdown (e.g. controller.shutdown()).
  """