diff --git a/pyproject.toml b/pyproject.toml
index 3d5981f..9fb2b31 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "durable-workflow"
-version = "2.3.0"
+version = "2.3.1"
 description = "Python client and worker SDK for Durable Workflow Cloud and self-hosted Server"
 readme = "README.md"
 requires-python = ">=3.10"
@@ -71,9 +71,9 @@ durable-workflow-replay-conformance = "durable_workflow.replay_conformance:main"
 durable-workflow-workflow-updates-conformance = "durable_workflow.workflow_updates_conformance:main"
 
 [tool.durable-workflow]
-product-train = "2.3.0"
-registry-version = "2.3.0"
-supported-server-versions = "2.4.2"
+product-train = "2.3.1"
+registry-version = "2.3.1"
+supported-server-versions = "2.4.8"
 worker-protocol-version = "1.19"
 control-plane-version = "2"
 durable-selection = true
diff --git a/src/durable_workflow/retry_policy.py b/src/durable_workflow/retry_policy.py
index de12b3f..9322c19 100644
--- a/src/durable_workflow/retry_policy.py
+++ b/src/durable_workflow/retry_policy.py
@@ -68,25 +68,26 @@ def _storage_refusal(exc: Exception) -> tuple[ServerError, str | None] | None:
 def _backend_unavailable_refusal(exc: Exception) -> tuple[bool, int | None]:
     if not isinstance(exc, httpx.HTTPStatusError) or exc.response.status_code != 503:
         return False, None
-    try:
-        body = exc.response.json()
-    except ValueError:
-        return False, None
-    if not isinstance(body, dict) or body.get("reason") != "backend_unavailable":
-        return False, None
     request = exc.request
     if request.method != "POST" or "X-Durable-Workflow-Protocol-Version" not in request.headers:
-        return True, None
+        return False, None
     operations = {
         "/api/worker/workflow-tasks/poll": "poll_workflow_task",
         "/api/worker/activity-tasks/poll": "poll_activity_task",
         "/api/worker/query-tasks/poll": "poll_query_task",
+        "/api/worker/update-validation-tasks/poll": "poll_update_validation_task",
         "/api/worker/register": "register_worker",
         "/api/worker/heartbeat": "heartbeat_worker",
     }
     operation = next((name for path, name in operations.items() if request.url.path.endswith(path)), None)
     if operation is None:
-        return True, None
+        return False, None
+    try:
+        body = exc.response.json()
+    except ValueError:
+        return False, None
+    if not isinstance(body, dict) or body.get("reason") != "backend_unavailable":
+        return False, None
     try:
         submitted = json.loads(request.content)
     except ValueError:
diff --git a/tests/test_release_metadata.py b/tests/test_release_metadata.py
index a6c826c..846722b 100644
--- a/tests/test_release_metadata.py
+++ b/tests/test_release_metadata.py
@@ -44,7 +44,7 @@ def test_worker_release_identity_matches_supported_server_and_protocol() -> None
     assert check_release_metadata.VERSION_PATTERN.fullmatch(project["version"]) is not None
     assert release["product-train"] == project["version"]
     assert release["registry-version"] == project["version"].replace("-rc.", "rc")
-    assert release["supported-server-versions"] == "2.4.2"
+    assert check_release_metadata.VERSION_PATTERN.fullmatch(release["supported-server-versions"]) is not None
     assert release["worker-protocol-version"] == PROTOCOL_VERSION == "1.19"
     assert release["durable-selection"] is True
     assert release["durable-selection-minimum-worker-protocol-version"] == "1.19"
diff --git a/tests/test_storage_admission.py b/tests/test_storage_admission.py
index c861cad..fb4e8bb 100644
--- a/tests/test_storage_admission.py
+++ b/tests/test_storage_admission.py
@@ -249,6 +249,20 @@ def handler(request: httpx.Request) -> httpx.Response:
     assert calls == 2
 
 
+async def test_control_backend_error_keeps_finite_transport_retries(retry_sleeps: list[float]) -> None:
+    calls = 0
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        nonlocal calls
+        calls += 1
+        return httpx.Response(503, json={"reason": "backend_unavailable", "retryable": True})
+
+    async with client_for(handler) as client:
+        with worker_scope(), pytest.raises(ServerError):
+            await client._request("POST", "/workflows", json={})
+    assert calls == 2
+
+
 async def test_shutdown_interrupts_backend_outage_without_new_poll(monkeypatch: pytest.MonkeyPatch) -> None:
     calls = 0
     stopped = False