fix(cron): coerce null runHistory ms fields from jobs.json

Explicit JSON null for runAtMs/durationMs bypassed the missing-key
default and raised TypeError on load. Treat null/blank like missing.

nanobot/cron/types.py

@@ -8,6 +8,13 @@ from typing import Any, Literal
 from nanobot.utils.dict_keys import get_camel_snake
 
 
+def _required_store_int(value: Any, default: int = 0) -> int:
+    """Coerce JSON numerics to int; treat null/blank like a missing key."""
+    if value is None or value == "":
+        return default
+    return int(value)
+
+
 @dataclass
 class CronSchedule:
     """Schedule definition for a cron job."""
@@ -78,9 +85,11 @@ class CronRunRecord:
     @classmethod
     def from_store_dict(cls, data: dict[str, Any]) -> CronRunRecord:
         return cls(
-            run_at_ms=int(get_camel_snake(data, "runAtMs", "run_at_ms", 0)),
+            run_at_ms=_required_store_int(get_camel_snake(data, "runAtMs", "run_at_ms", 0)),
             status=data["status"],
-            duration_ms=int(get_camel_snake(data, "durationMs", "duration_ms", 0)),
+            duration_ms=_required_store_int(
+                get_camel_snake(data, "durationMs", "duration_ms", 0)
+            ),
             error=data.get("error"),
         )
 

tests/cron/test_cron_service.py

@@ -1007,3 +1007,42 @@ async def test_list_jobs_during_on_job_does_not_cause_stale_reload(tmp_path) ->
         next_run = j["state"]["nextRunAtMs"]
         assert next_run is not None
         assert next_run > now_ms, f"Job '{j['name']}' next_run should be in the future"
+
+
+def test_load_jobs_accepts_null_run_history_ms(tmp_path) -> None:
+    store_path = tmp_path / "cron" / "jobs.json"
+    store_path.parent.mkdir(parents=True)
+    store_path.write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "jobs": [
+                    {
+                        "id": "j1",
+                        "name": "t",
+                        "enabled": True,
+                        "schedule": {"kind": "every", "everyMs": 60_000},
+                        "payload": {
+                            "kind": "agent_turn",
+                            "message": "hi",
+                            "sessionKey": "websocket:chat-1",
+                        },
+                        "state": {
+                            "runHistory": [
+                                {"runAtMs": None, "status": "ok", "durationMs": None},
+                            ],
+                        },
+                        "createdAtMs": 0,
+                        "updatedAtMs": 0,
+                    }
+                ],
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    jobs, _version = CronService(store_path)._load_jobs()
+    assert jobs is not None
+    assert jobs[0].state.run_history[0].run_at_ms == 0
+    assert jobs[0].state.run_history[0].duration_ms == 0
+    assert jobs[0].state.run_history[0].status == "ok"