AFS sole-account fallback when runtime selector is not a broker id

main.py

@@ -928,9 +928,36 @@ def account_facts_sync():
     client = None
     try:
         client = READ_ONLY_ACCOUNT_FACTS_CLIENT_BUILDER()
+        expected_account = config.account_id
+        try:
+            broker_accounts = client.account_numbers()
+        except Exception:
+            broker_accounts = None
+        if (
+            isinstance(expected_account, str)
+            and isinstance(broker_accounts, list)
+            and expected_account not in broker_accounts
+            and len(broker_accounts) == 1
+            and isinstance(broker_accounts[0], str)
+            and broker_accounts[0]
+        ):
+            # RUNTIME_TARGET account_selector may be a deployment label (e.g. platform id)
+            # rather than the Firstrade broker account number. For single-account brokers,
+            # bind the sole returned account for read-only facts publish only.
+            sole = broker_accounts[0]
+            app.logger.warning(
+                "account_facts_sync sole_account_fallback selector=%s sole=%s",
+                mask_account_id(expected_account),
+                mask_account_id(sole),
+            )
+            config = bind_account_facts_runtime_selector(
+                replace(config, account_id=None),
+                sole,
+            )
+            expected_account = config.account_id
         observation = collect_firstrade_account_facts(
             client,
-            expected_account=config.account_id,
+            expected_account=expected_account,
             include_positions=False,
         )
         payload = build_firstrade_account_snapshot(
@@ -939,10 +966,17 @@ def account_facts_sync():
             account_scope=str(runtime_target.account_scope),
         )
     except AccountFactsUnavailable as exc:
+        accounts_len = -1
+        try:
+            if client is not None:
+                accounts_len = len(client.account_numbers())
+        except Exception:
+            accounts_len = -1
         app.logger.warning(
-            "account_facts_sync collect failed reason=%s expected=%s",
+            "account_facts_sync collect failed reason=%s expected=%s accounts_len=%s",
             exc.reason_code,
             mask_account_id(config.account_id or ""),
+            accounts_len,
         )
         return jsonify({"ok": False, "error": exc.reason_code}), 503
     except AccountFactsPublishError as exc:

tests/test_account_facts_endpoint.py

@@ -257,3 +257,46 @@ def test_collection_failure_is_safe_and_client_still_closes(monkeypatch):
     assert response.get_json() == {"ok": False, "error": "balances_unavailable"}
     assert client.closed is True
     assert published == []
+
+
+def test_sync_endpoint_falls_back_to_sole_broker_account_when_selector_unmatched(monkeypatch):
+    _configure(monkeypatch, FIRSTRADE_ACCOUNT="firstrade")
+    monkeypatch.setattr(main, "_runtime_settings", lambda: SimpleNamespace(runtime_target=SimpleNamespace(
+        platform_id="firstrade",
+        account_selector=("firstrade",),
+        account_scope="us",
+    )))
+
+    class SoleAccountClient(FakeClient):
+        def account_numbers(self):
+            return ["synthetic-native-id"]
+
+    client = SoleAccountClient()
+    monkeypatch.setattr(main, "READ_ONLY_ACCOUNT_FACTS_CLIENT_BUILDER", lambda: client)
+    collector_calls = []
+
+    def collect(_client, *, expected_account, include_positions):
+        collector_calls.append({"expected_account": expected_account, "include_positions": include_positions})
+        return {
+            "status": "available",
+            "platform": "firstrade",
+            "account_selector_status": "matched",
+            "broker_account_id": expected_account,
+            "observed_started_at": "2026-10-08T08:00:00+00:00",
+            "observed_finished_at": "2026-10-08T08:00:03+00:00",
+            "balances": {"currency": "USD", "provider_equity": "100.00", "cash_balance": "50.00"},
+        }
+
+    monkeypatch.setattr(main, "collect_firstrade_account_facts", collect)
+    published = []
+    monkeypatch.setattr(main, "publish_firstrade_account_snapshot", lambda payload, cfg: published.append((payload, cfg)))
+
+    response = main.app.test_client().post(
+        "/account-facts-sync",
+        headers={"Authorization": "Bearer synthetic-facts-token"},
+    )
+    assert response.status_code == 200
+    assert collector_calls == [{"expected_account": "synthetic-native-id", "include_positions": False}]
+    assert published[0][0]["broker_account_id"] == "synthetic-native-id"
+    assert published[0][1].account_id == "synthetic-native-id"
+    assert client.closed is True