diff --git a/hermes_cli/web_server_idle_exit.py b/hermes_cli/web_server_idle_exit.py
index 0e2711575e..567ce96951 100644
--- a/hermes_cli/web_server_idle_exit.py
+++ b/hermes_cli/web_server_idle_exit.py
@@ -137,7 +137,8 @@ def busy_ledger() -> Optional[str]:
 
 
 def turn_in_flight() -> Optional[bool]:
-    """True/False from :func:`busy_ledger`; None when it cannot be read."""
+    """Bool view of :func:`busy_ledger`, kept so ``should_exit_idle`` / the idle watchdog and injected
+    test probes keep their ``Optional[bool]`` contract; None when the ledgers cannot be read."""
     ledger = busy_ledger()
     return None if ledger is None else bool(ledger)
 
diff --git a/hermes_cli/web_server_idle_proof.py b/hermes_cli/web_server_idle_proof.py
index a109c01996..66c915b5e4 100644
--- a/hermes_cli/web_server_idle_proof.py
+++ b/hermes_cli/web_server_idle_proof.py
@@ -36,7 +36,7 @@ def pending_human_input() -> Optional[int]:
         return None
 
 
-def idle_proof(turn_probe: Callable[[], Optional[bool | str]] = busy_ledger,
+def idle_proof(turn_probe: Callable[[], bool | str | None] = busy_ledger,
                input_probe: Callable[[], Optional[int]] = pending_human_input) -> dict:
     """``{"idle": True | False | None, "reason": str | None}`` plus ``"detail"`` naming the busy ledger.