fix(models): don't trust foreign catalog pricing for custom/unknown providers

Custom providers (custom:xxx) serve their own pricing; models.dev stores
OpenRouter prices for the same model ids. The cost guard fired on that
foreign pricing and blocked composer/CLI model switches on custom
providers with a wildly wrong warning (#54348).

expensive_model_warning now only trusts model_info/models.dev pricing
when the provider maps to a models.dev provider and the info's
provider_id matches, and only consults the pricing-entry lookup when
the billing route is known. Salvaged from #54422; the PR's desktop-hook
half predates the use-model-controls rewrite and is superseded by the
hook's existing rollback handling.

hermes_cli/model_cost_guard.py

@@ -6,7 +6,7 @@ from dataclasses import dataclass
 from decimal import Decimal, InvalidOperation
 from typing import Optional
 
-from agent.models_dev import ModelInfo
+from agent.models_dev import ModelInfo, PROVIDER_TO_MODELS_DEV
 
 
 INPUT_COST_WARNING_THRESHOLD = Decimal("20")
@@ -54,6 +54,40 @@ def _pricing_from_model_info(
     )
 
 
+def _known_models_dev_provider(provider: Optional[str]) -> Optional[str]:
+    normalized = (provider or "").strip().lower()
+    if not normalized:
+        return None
+    return PROVIDER_TO_MODELS_DEV.get(normalized)
+
+
+def _can_trust_model_info_pricing(
+    provider: Optional[str],
+    model_info: Optional[ModelInfo],
+) -> bool:
+    expected_provider = _known_models_dev_provider(provider)
+    if not expected_provider or model_info is None:
+        return False
+
+    actual_provider = str(getattr(model_info, "provider_id", "") or "").strip().lower()
+    return not actual_provider or actual_provider == expected_provider
+
+
+def _can_trust_pricing_lookup(
+    model_name: str,
+    *,
+    provider: Optional[str],
+    base_url: Optional[str],
+) -> bool:
+    try:
+        from agent.usage_pricing import resolve_billing_route
+
+        route = resolve_billing_route(model_name, provider=provider, base_url=base_url)
+    except Exception:
+        return False
+    return route.billing_mode != "unknown"
+
+
 def expensive_model_warning(
     model_name: str,
     *,
@@ -71,8 +105,18 @@ def expensive_model_warning(
     if not model:
         return None
 
-    input_cost, output_cost, source = _pricing_from_model_info(model_info)
-    if input_cost is None and output_cost is None and provider:
+    input_cost: Optional[Decimal] = None
+    output_cost: Optional[Decimal] = None
+    source = ""
+
+    if _can_trust_model_info_pricing(provider, model_info):
+        input_cost, output_cost, source = _pricing_from_model_info(model_info)
+
+    if (
+        input_cost is None
+        and output_cost is None
+        and _known_models_dev_provider(provider)
+    ):
         try:
             from agent.models_dev import get_model_info
 
@@ -81,7 +125,12 @@ def expensive_model_warning(
             )
         except Exception:
             pass
-    if input_cost is None and output_cost is None:
+
+    if (
+        input_cost is None
+        and output_cost is None
+        and _can_trust_pricing_lookup(model, provider=provider, base_url=base_url)
+    ):
         try:
             from agent.usage_pricing import get_pricing_entry
 

tests/hermes_cli/test_model_cost_guard.py

@@ -1,5 +1,7 @@
 from decimal import Decimal
 
+import pytest
+
 from agent.models_dev import ModelInfo
 from agent.usage_pricing import PricingEntry
 from hermes_cli.model_cost_guard import expensive_model_warning
@@ -10,16 +12,114 @@ def test_no_warning_when_known_prices_are_at_threshold():
         id="edge/model",
         name="edge/model",
         family="",
-        provider_id="test",
+        provider_id="anthropic",
         cost_input=20.0,
         cost_output=100.0,
     )
 
-    assert expensive_model_warning("edge/model", provider="test", model_info=info) is None
+    assert expensive_model_warning("edge/model", provider="anthropic", model_info=info) is None
 
 
+def test_warns_when_models_dev_input_price_exceeds_threshold():
+    info = ModelInfo(
+        id="expensive/input",
+        name="expensive/input",
+        family="",
+        provider_id="anthropic",
+        cost_input=20.01,
+        cost_output=1.0,
+    )
+
+    warning = expensive_model_warning(
+        "expensive/input",
+        provider="anthropic",
+        model_info=info,
+    )
+
+    assert warning is not None
+    assert warning.input_cost_per_million == Decimal("20.01")
+    assert "EXPENSIVE MODEL WARNING" in warning.message
+    assert "$20/M input" in warning.message
 
 
+@pytest.mark.parametrize("provider", ["custom", "custom:routerai", "routerai"])
+def test_skips_foreign_models_dev_pricing_for_custom_or_unknown_providers(provider):
+    info = ModelInfo(
+        id="openai/gpt-5.5-pro",
+        name="openai/gpt-5.5-pro",
+        family="",
+        provider_id="openrouter",
+        cost_input=25.0,
+        cost_output=125.0,
+    )
+
+    assert (
+        expensive_model_warning(
+            "openai/gpt-5.5-pro",
+            provider=provider,
+            model_info=info,
+        )
+        is None
+    )
+
+
+def test_skips_untrusted_provider_pricing_lookup_for_custom_provider(monkeypatch):
+    monkeypatch.setattr("agent.models_dev.get_model_info", lambda *_args, **_kwargs: None)
+    pricing_calls = []
+
+    def fake_get_pricing_entry(*_args, **_kwargs):
+        pricing_calls.append(_args)
+        return PricingEntry(
+            input_cost_per_million=Decimal("25"),
+            output_cost_per_million=Decimal("125"),
+            source="provider_models_api",
+        )
+
+    monkeypatch.setattr("agent.usage_pricing.get_pricing_entry", fake_get_pricing_entry)
+
+    warning = expensive_model_warning(
+        "openai/gpt-5.5-pro",
+        provider="custom:routerai",
+        base_url="https://routerai.example/v1",
+    )
+
+    assert warning is None
+    assert pricing_calls == []
+
+
+def test_warns_when_pricing_entry_output_price_exceeds_threshold(monkeypatch):
+    monkeypatch.setattr("agent.models_dev.get_model_info", lambda *_args, **_kwargs: None)
+    monkeypatch.setattr(
+        "agent.usage_pricing.get_pricing_entry",
+        lambda *_args, **_kwargs: PricingEntry(
+            input_cost_per_million=Decimal("1.00"),
+            output_cost_per_million=Decimal("100.01"),
+            source="provider_models_api",
+        ),
+    )
+
+    warning = expensive_model_warning("provider/expensive-output", provider="openrouter")
+
+    assert warning is not None
+    assert warning.output_cost_per_million == Decimal("100.01")
+    assert "$100.01/M" in warning.message
+
+
+def test_openai_gpt55_pro_adds_suggestion(monkeypatch):
+    monkeypatch.setattr("agent.models_dev.get_model_info", lambda *_args, **_kwargs: None)
+    monkeypatch.setattr(
+        "agent.usage_pricing.get_pricing_entry",
+        lambda *_args, **_kwargs: PricingEntry(
+            input_cost_per_million=Decimal("25"),
+            output_cost_per_million=Decimal("125"),
+            source="provider_models_api",
+        ),
+    )
+
+    warning = expensive_model_warning("openai/gpt-5.5-pro", provider="openrouter")
+
+    assert warning is not None
+    assert "did you mean to select openai/gpt-5.5?" in warning.message
 
 
 def test_openai_gpt55_pro_warns_for_nous_portal_pricing(monkeypatch):