fix(runner): narrow optional completion state for consumer mypy

scripts/runner_lib/core.py

@@ -1039,7 +1039,7 @@ def _completion_was_unproductive(prior: dict[str, Any] | None) -> bool:
     pre-#3433 behavior (treat the completion as terminal) rather than silently loosening the
     debounce for every caller that has not been taught to report it.
     """
-    return bool(prior) and prior.get("productive") is False
+    return prior is not None and prior.get("productive") is False
 
 
 def _unproductive_completion_count(prior: dict[str, Any] | None) -> int:

tests/scripts/test_runner_lib.py

@@ -971,6 +971,24 @@ def fail_check_call(
     assert Path(clone_env["GIT_ASKPASS"]).exists() is False
 
 
+@pytest.mark.parametrize(
+    ("prior", "expected"),
+    [
+        (None, False),
+        ({}, False),
+        ({"productive": None}, False),
+        ({"productive": True}, False),
+        ({"productive": False}, True),
+        ({"productive": 0}, False),
+        ({"productive": "false"}, False),
+    ],
+)
+def test_completion_productivity_requires_explicit_false(
+    prior: dict[str, Any] | None, expected: bool
+) -> None:
+    assert runner_core._completion_was_unproductive(prior) is expected
+
+
 def _unproductive_result() -> RunnerResult:
     """A run that exits 0 having done nothing — the shape the codex sandbox failure takes."""
     return RunnerResult(