diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab12a64..eb46bab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- `Worker.run_until()` now records the schedule-to-start histogram for activity tasks, as `run()` already did (#188).
+
 ## [2.15.1] - 2026-11-11
 
 ### Fixed
diff --git a/src/durable_workflow/worker.py b/src/durable_workflow/worker.py
index c744650..1ad5fb5 100644
--- a/src/durable_workflow/worker.py
+++ b/src/durable_workflow/worker.py
@@ -4743,6 +4743,9 @@ async def _retry_run_until_poll_refusal(
         return True
 
     async def _run_until_activity_task(self, task: dict[str, Any]) -> None:
+        # run_until() dispatches activities here instead of through
+        # _dispatch_activity_task, so record the Server-computed age too (#188).
+        self._record_task_schedule_to_start("activity", task)
         task_start = time.perf_counter()
         outcome = "error"
         self._activity_inflight += 1
diff --git a/tests/test_sdk_metrics_contract.py b/tests/test_sdk_metrics_contract.py
index a0065cb..f781460 100644
--- a/tests/test_sdk_metrics_contract.py
+++ b/tests/test_sdk_metrics_contract.py
@@ -228,6 +228,24 @@ async def execute(_: object) -> object:
     assert assert_contract(Recorder(recorder.calls[1:]), duration=19.0) == {"worker_task"}
 
 
+async def test_run_until_activity_records_server_ready_age(monkeypatch: pytest.MonkeyPatch) -> None:
+    # run_until() runs activities through _run_until_activity_task, not
+    # _dispatch_activity_task; both must record schedule-to-start (#188).
+    recorder = Recorder()
+    client = Client("https://runtime.example", metrics=recorder)
+    client._cluster_info = {"worker_protocol": {"server_capabilities": {"claimed_task_ready_age": True}}}
+    worker = Worker(client, task_queue="orders")
+
+    async def execute(_: object) -> object:
+        return "completed"
+
+    monkeypatch.setattr(worker, "_run_activity_task", execute)
+    await worker._run_until_activity_task({"ready_age_ms": 1250})
+    assert recorder.calls[0] == (
+        "record", SCHEDULE_TO_START, 1.25, {"task_kind": "activity", "task_queue": "orders"},
+    )
+
+
 @pytest.mark.parametrize("kind", ["workflow", "activity"])
 @pytest.mark.parametrize("value", [None, True, False, -1, 9007199254740992, 1.0, float("nan"),
                                   float("inf"), "private-value", {"private-key": "private-value"}, []])