fix(gateway): /usage falls back to the configured provider when no route is known

With no live/cached agent and no persisted billing route (fresh session right
after `hermes auth add openai-codex`, or an evicted agent with an empty
transcript) /usage returned the bare stub and never tried the account-usage
fetch even though on-disk credentials could answer it. Resolve the provider
from `model.provider` in the gateway config, as /status already does; the
fetch stays fail-open. Complements the credential-pool-aware Codex resolver
that already covers the token-lookup half of this report.

Fixes #15167

gateway/slash_commands_status.py

@@ -73,6 +73,14 @@ HISTORY_UNREADABLE = ("⚠️ I can't read this conversation's history right now
                       "to start fresh.")
 
 
+def _configured_provider() -> str:
+    """``model.provider`` from the gateway config ("" when unset)."""
+    from gateway.run import _load_gateway_config
+    user_config = _load_gateway_config()
+    model_cfg = user_config.get("model", {}) if isinstance(user_config, dict) else {}
+    return _clean_str(model_cfg.get("provider")) if isinstance(model_cfg, dict) else ""
+
+
 def _quiet_sync(call, default=None):
     """Sync twin of ``_quiet``."""
     try:
@@ -573,6 +581,11 @@ class GatewayStatusCommandsMixin:
         )
         if not provider and getattr(self, "_session_db", None) is not None:
             provider, base_url = await self._persisted_billing_route(source)
+        if not provider:
+            # Fresh or evicted session with no persisted route (e.g. /usage right after login):
+            # fall back to the configured provider, as /status does, so account limits such as
+            # Codex subscription windows still render from on-disk credentials (#15167).
+            provider = await _quiet(lambda: asyncio.to_thread(_configured_provider)) or None
         if wants_reset:
             if str(provider or "").strip().lower() != "openai-codex":
                 return t("gateway.usage.reset_wrong_provider")

tests/gateway/test_usage_command.py

@@ -162,6 +162,43 @@ class TestUsageAccountSection:
         assert "📊 **Session Info**" in result
         assert "📈 **Account limits**" in result
 
+    @pytest.mark.asyncio
+    async def test_usage_command_falls_back_to_configured_provider_without_history(self, monkeypatch):
+        """#15167: no agent, no persisted route, empty transcript -> still fetch account limits
+        for the configured provider instead of the bare "no data" stub."""
+        runner = _make_runner(SK)
+        runner._session_db = AsyncSessionDB(MagicMock())
+        runner._session_db._db.get_session.return_value = {}
+        runner._session_db._db.get_recent_session_model_route.return_value = None
+        session_entry = MagicMock()
+        session_entry.session_id = "sess-fresh"
+        runner.session_store.get_or_create_session.return_value = session_entry
+        runner.session_store.load_transcript.return_value = []
+
+        calls = []
+
+        async def _fake_to_thread(fn, *args, **kwargs):
+            calls.append({"fn": fn, "args": args, "kwargs": kwargs})
+            return fn(*args, **kwargs)
+
+        monkeypatch.setattr("gateway.run.asyncio.to_thread", _fake_to_thread)
+        monkeypatch.setattr("gateway.run._load_gateway_config", lambda: {"model": {"provider": "openai-codex"}})
+        monkeypatch.setattr(
+            "gateway.slash_commands_status.fetch_account_usage",
+            lambda provider, base_url=None, api_key=None: object(),
+        )
+        monkeypatch.setattr(
+            "gateway.slash_commands_status.render_account_usage_lines",
+            lambda snapshot, markdown=False: ["📈 **Account limits**", "Provider: openai-codex (Plus)",
+                                              "Weekly: 91% remaining (9% used)"],
+        )
+        monkeypatch.setattr("agent.account_usage.nous_credits_lines", lambda markdown=False: [])
+
+        result = await runner._handle_usage_command(MagicMock())
+
+        assert any(c["args"] == ("openai-codex",) for c in calls)
+        assert "📈 **Account limits**" in result and "Weekly: 91% remaining" in result
+
     @pytest.mark.asyncio
     async def test_usage_command_prefers_recent_persisted_route(self, monkeypatch):
         runner = _make_runner(SK)