Memory-queue ids carry a per-instance boot token, so a restart without Redis no longer overwrites earlier run rows

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

backend/tests/flow/test_queue.py

@@ -25,6 +25,18 @@ def test_items_come_back_in_the_order_they_went_in():
     assert all(item.entry_id for item in claimed)
 
 
+def test_two_queues_never_hand_out_the_same_id():
+    """A restart without Redis must not reuse the last boot's run ids."""
+    first, second = MemoryWorkQueue(), MemoryWorkQueue()
+    for queue in (first, second):
+        queue.add(WorkItem(kind="cascade", node="f.n", flow="f"))
+
+    ids = [queue.claim(1, 10)[0].entry_id for queue in (first, second)]
+
+    assert ids[0] != ids[1]
+    assert all(len(entry_id) <= 64 for entry_id in ids)
+
+
 def test_claiming_an_empty_queue_waits_and_gives_up():
     queue = MemoryWorkQueue()
     started = time.monotonic()