diff --git a/tests/test_issue50_dispatch_herdr.py b/tests/test_issue50_dispatch_herdr.py
index 1e55d87..cf36bee 100644
--- a/tests/test_issue50_dispatch_herdr.py
+++ b/tests/test_issue50_dispatch_herdr.py
@@ -522,30 +522,44 @@ def _onboarding(box: Box, ack: int) -> str:
     return a
 
 
+def _restamp(box: Box, jid: str, created_at: str) -> None:
+    """Give a record the test owns another created_at, atomically: a wrapper
+    scanning the registry must never find the file half-written (an unreadable
+    record is skipped, which would let it through)."""
+    rec = box.record(jid)
+    rec["created_at"] = created_at
+    tmp = box.jobs / f"{jid}.json.tmp"
+    tmp.write_text(json.dumps(rec))
+    os.replace(tmp, box.jobs / f"{jid}.json")
+
+
 def test_c10_a_pending_onboarding_within_its_ack_budget_blocks_the_session_past_the_signal_window(box):
     # review 5a09a13f F-A: the onboarding and the first job are registered in
     # the same second (create registers, then injects; the job's wrapper
     # registers a moment later), where the FIFO's (created_at, job_id) once
-    # let a lower id pass the injected onboarding; the second job comes a
-    # different second
-    while time.time() % 1 > 0.05:
-        time.sleep(0.005)
-    t0 = time.time()
+    # let a lower id pass the injected onboarding. The tie is made, not timed
+    # (reviews 98b31bb2 / 352066ec / 244b8072 F-B): once the first job's record
+    # exists, A takes its created_at - A has no signal and no admission, and the
+    # pane already holds its prompt, so nothing else depends on the stamp. The
+    # second job comes a different second.
     a = box.register(ack_timeout_sec=180)
     known = box.job_ids()
+    created = 0
     for label in ("before", "after"):
         if label == "after":
-            time.sleep(max(0.0, t0 + 31.5 - time.time()))       # A is now older than the signal window
+            time.sleep(max(0.0, created + 31.5 - time.time()))  # A is now older than the signal window
         proc = box.submit(prompt="work " + label, MAM_DISPATCH_WAIT_S="3")
         if label == "before":
             prompt = box.herdr("agent", "prompt", SESSION, "Onboarding " + a)
             assert prompt.returncode == 0, prompt.stdout + prompt.stderr
         b = box.wait_new_job(known)
         known.add(b)
-        print(label, "created", a, box.record(a)["created_at"], b, box.record(b)["created_at"],
-              "registered at +%.2fs" % (time.time() - t0))
         if label == "before":
-            assert box.record(b)["created_at"] == box.record(a)["created_at"], "the same-second tie this exercises"
+            _restamp(box, a, box.record(b)["created_at"])
+            created = calendar.timegm(time.strptime(box.record(a)["created_at"], "%Y-%m-%dT%H:%M:%SZ"))
+        print(label, "created", a, box.record(a)["created_at"], b, box.record(b)["created_at"],
+              "at +%.2fs" % (time.time() - created))
+        assert (box.record(b)["created_at"] > box.record(a)["created_at"]) == (label == "after"), label
         rc, out, err = box.finish(proc)
         assert rc == 5, (label, out + err)
         rec = box.record(b)
@@ -553,7 +567,6 @@ def test_c10_a_pending_onboarding_within_its_ack_budget_blocks_the_session_past_
         assert a in err and "still has open jobs in the registry" in err and "stale open job" not in err, (label, err)
         assert b not in box.pane_text(), label
         assert box.record(a)["status"] == "pending" and "dispatch_wait_at" not in box.record(a), label
-    created = calendar.timegm(time.strptime(box.record(a)["created_at"], "%Y-%m-%dT%H:%M:%SZ"))
     assert 31 <= time.time() - created < 180, "the second answer came past the window, within the budget"