diff --git a/cron/scheduler.py b/cron/scheduler.py
index fafcbfab95..2cb1547ad3 100644
--- a/cron/scheduler.py
+++ b/cron/scheduler.py
@@ -123,9 +123,19 @@ _LOCK_FILE = _LOCK_DIR / ".tick.lock"
 
 
 def _resolve_origin(job: dict) -> Optional[dict]:
-    """Extract origin info from a job, preserving any extra routing metadata."""
+    """Extract origin info from a job, preserving any extra routing metadata.
+
+    Treats non-dict origins (free-form provenance strings, ints, lists from
+    migration scripts or hand-edited jobs.json) as missing instead of
+    crashing with ``AttributeError`` on ``origin.get(...)``. Without this
+    guard, a job tagged with e.g. ``"combined-digest-replaces-x-and-y"``
+    crashed every fire attempt with
+    ``'str' object has no attribute 'get'`` — ``mark_job_run`` recorded the
+    failure, but the next tick re-loaded the same poisoned origin and
+    crashed identically until the field was patched manually (#18722).
+    """
     origin = job.get("origin")
-    if not origin:
+    if not isinstance(origin, dict):
         return None
     platform = origin.get("platform")
     chat_id = origin.get("chat_id")
diff --git a/tests/cron/test_scheduler.py b/tests/cron/test_scheduler.py
index 8c204d9a51..b12bb578a3 100644
--- a/tests/cron/test_scheduler.py
+++ b/tests/cron/test_scheduler.py
@@ -46,6 +46,29 @@ class TestResolveOrigin:
         job = {"origin": {}}
         assert _resolve_origin(job) is None
 
+    @pytest.mark.parametrize(
+        "non_dict_origin",
+        [
+            "combined-digest-replaces-x-and-y-20260503",
+            123,
+            ["telegram", "12345"],
+            ("platform", "chat_id"),
+            42.0,
+        ],
+    )
+    def test_non_dict_origin_returns_none_instead_of_crashing(self, non_dict_origin):
+        """Non-dict origins (provenance strings from hand-edited or migrated
+        jobs.json) must be treated as missing instead of crashing the
+        scheduler tick on ``origin.get('platform')`` with
+        ``'str' object has no attribute 'get'`` (#18722).
+
+        Before this guard a job in this state crashed every fire attempt
+        forever; ``mark_job_run`` recorded the error but the next tick
+        re-loaded the poisoned origin and crashed identically.
+        """
+        job = {"origin": non_dict_origin}
+        assert _resolve_origin(job) is None
+
 
 class TestResolveDeliveryTarget:
     def test_origin_delivery_preserves_thread_id(self):