fix(health): preserve transient failure codes through stale snapshot fallback

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

tests/application/test_account_snapshot.py

@@ -209,3 +209,15 @@ def test_slots_rpc_normalizes_snapshot_store_read_failure():
     with pytest.raises(AccountSnapshotUnavailable) as raised:
         service.holdings_for_slots_rpc()
     assert raised.value.code == "read_failed"
+
+
+def test_sell_stale_snapshot_preserves_transient_live_failure_detail_code():
+    broker, _, service, now = _wire()
+    assert service.refresh()
+    broker.balance_error = "timeout"
+    now[0] += timedelta(seconds=3601)
+
+    with pytest.raises(AccountSnapshotUnavailable) as raised:
+        service.holdings_for_sell()
+    assert raised.value.code == "expired"
+    assert raised.value.detail_code == "timeout"

trex_core/application/account_snapshot.py

@@ -214,6 +214,7 @@ class AccountSnapshotService:
 
     def holdings_for_sell(self) -> list[BalanceItem]:
         """Prefer a live balance; fallback only on transient transport failure."""
+        transient_code: str | None = None
         try:
             return self._broker.get_balance()
         except BrokerBalanceError as exc:
@@ -221,8 +222,14 @@ class AccountSnapshotService:
                 raise AccountSnapshotUnavailable(
                     "live_read_failed", detail_code=exc.code
                 ) from None
+            transient_code = exc.code
         snapshot = self._load_current()
-        age = self._age(snapshot.holdings_captured_at, self._sell_max_age)
+        try:
+            age = self._age(snapshot.holdings_captured_at, self._sell_max_age)
+        except AccountSnapshotUnavailable as exc:
+            raise AccountSnapshotUnavailable(
+                exc.code, detail_code=transient_code
+            ) from None
         _log.warning(
             "sell balance using account snapshot: age_sec=%.0f",
             age,

trex_core/application/execution.py

@@ -443,9 +443,11 @@ class ExecutionService:
         try:
             holdings = self._sell_dispatch_balance_reader()
         except AccountSnapshotUnavailable as exc:
-            code = "stale_snapshot" if exc.code == "expired" else (
-                getattr(exc, "detail_code", None) or exc.code
-            )
+            detail_code = getattr(exc, "detail_code", None)
+            if exc.code == "expired" and detail_code is None:
+                code = "stale_snapshot"
+            else:
+                code = detail_code or exc.code
             lifecycle, backoff = self._balance_health.record_failure(
                 self._balance_worker, code=code
             )