fix(account-snapshot): treat timeout/http5xx as transient fallback failures

Co-authored-by: genichin <4282227+genichin@users.noreply.github.com>

tests/application/test_account_snapshot.py

@@ -75,10 +75,11 @@ def test_refresh_persists_independent_holdings_and_cash_capture_times():
     assert second.cash_captured_at == first.cash_captured_at
 
 
-def test_sell_falls_back_only_for_transport_failure_and_within_sell_ttl():
+@pytest.mark.parametrize("error_code", ["transport_failed", "timeout", "http_5xx"])
+def test_sell_falls_back_for_transient_live_read_failures_within_sell_ttl(error_code):
     broker, _, service, now = _wire()
     assert service.refresh()
-    broker.balance_error = "transport_failed"
+    broker.balance_error = error_code
     now[0] += timedelta(seconds=601)
 
     assert service.holdings_for_sell() == [BalanceItem("005930", 2)]
@@ -126,6 +127,16 @@ def test_buy_guard_accounts_for_existing_pending_cash_and_never_renews_age():
     )
 
 
+@pytest.mark.parametrize("error_code", ["transport_failed", "timeout", "http_5xx"])
+def test_buy_guard_keeps_existing_cash_snapshot_on_transient_cash_refresh_failure(error_code):
+    broker, _, service, _ = _wire()
+    assert service.refresh()
+    broker.cash_error = error_code
+
+    assert service.refresh() is False
+    assert service.buy_guard(qty=2, limit_price=100_000) is None
+
+
 def test_current_account_hash_is_required_on_every_consume():
     broker, _, service, _ = _wire()
     assert service.refresh()

trex_core/application/account_snapshot.py

@@ -217,7 +217,7 @@ class AccountSnapshotService:
         try:
             return self._broker.get_balance()
         except BrokerBalanceError as exc:
-            if exc.code != "transport_failed":
+            if exc.code not in {"transport_failed", "timeout", "http_5xx"}:
                 raise AccountSnapshotUnavailable(
                     "live_read_failed", detail_code=exc.code
                 ) from None
@@ -253,7 +253,7 @@ class AccountSnapshotService:
         reserved_cash: float = 0.0,
     ) -> Optional[str]:
         """Return a stable rejection reason, or None when bounded admission passes."""
-        if self._last_cash_error not in {None, "transport_failed"}:
+        if self._last_cash_error not in {None, "transport_failed", "timeout", "http_5xx"}:
             return "account_snapshot_unavailable"
         try:
             snapshot = self._load_current()