test(llm_clients): add model validation warning tests for LLM clients

- Add tests to verify warnings for unknown models in OpenAI, Anthropic, and Google clients
- Confirm no warnings are issued for known models in OpenAI client
- Verify OpenRouter provider allows custom models without warnings
- Implement helper assertion for checking single unknown model warning
- Ensure tests patch underlying LLM constructors for isolation and inspection

tests/test_llm_clients.py

@@ -0,0 +1,90 @@
+import warnings
+import unittest
+from unittest.mock import patch
+
+from tradingagents.llm_clients.anthropic_client import AnthropicClient
+from tradingagents.llm_clients.google_client import GoogleClient
+from tradingagents.llm_clients.openai_client import OpenAIClient
+
+
+class LLMClientModelValidationTests(unittest.TestCase):
+    def assert_single_unknown_model_warning(self, warning_records, provider_name, model):
+        self.assertEqual(len(warning_records), 1)
+        self.assertIs(warning_records[0].category, UserWarning)
+        self.assertIn(
+            f"Unknown {provider_name} model '{model}'.",
+            str(warning_records[0].message),
+        )
+
+    def test_openai_client_warns_for_unknown_model(self):
+        model = "fake-openai-model"
+
+        with patch(
+            "tradingagents.llm_clients.openai_client.UnifiedChatOpenAI",
+            side_effect=lambda **kwargs: kwargs,
+        ):
+            with warnings.catch_warnings(record=True) as warning_records:
+                warnings.simplefilter("always")
+                llm = OpenAIClient(model).get_llm()
+
+        self.assertEqual(llm["model"], model)
+        self.assert_single_unknown_model_warning(warning_records, "OpenAI", model)
+
+    def test_anthropic_client_warns_for_unknown_model(self):
+        model = "fake-claude-model"
+
+        with patch(
+            "tradingagents.llm_clients.anthropic_client.ChatAnthropic",
+            side_effect=lambda **kwargs: kwargs,
+        ):
+            with warnings.catch_warnings(record=True) as warning_records:
+                warnings.simplefilter("always")
+                llm = AnthropicClient(model).get_llm()
+
+        self.assertEqual(llm["model"], model)
+        self.assert_single_unknown_model_warning(warning_records, "Anthropic", model)
+
+    def test_google_client_warns_for_unknown_model(self):
+        model = "fake-gemini-model"
+
+        with patch(
+            "tradingagents.llm_clients.google_client.NormalizedChatGoogleGenerativeAI",
+            side_effect=lambda **kwargs: kwargs,
+        ):
+            with warnings.catch_warnings(record=True) as warning_records:
+                warnings.simplefilter("always")
+                llm = GoogleClient(model).get_llm()
+
+        self.assertEqual(llm["model"], model)
+        self.assert_single_unknown_model_warning(warning_records, "Google", model)
+
+    def test_openai_client_does_not_warn_for_known_model(self):
+        with patch(
+            "tradingagents.llm_clients.openai_client.UnifiedChatOpenAI",
+            side_effect=lambda **kwargs: kwargs,
+        ):
+            with warnings.catch_warnings(record=True) as warning_records:
+                warnings.simplefilter("always")
+                llm = OpenAIClient("gpt-5-mini").get_llm()
+
+        self.assertEqual(llm["model"], "gpt-5-mini")
+        self.assertEqual(warning_records, [])
+
+    def test_openrouter_allows_custom_model_without_warning(self):
+        model = "custom-openrouter-model"
+
+        with patch(
+            "tradingagents.llm_clients.openai_client.UnifiedChatOpenAI",
+            side_effect=lambda **kwargs: kwargs,
+        ):
+            with warnings.catch_warnings(record=True) as warning_records:
+                warnings.simplefilter("always")
+                llm = OpenAIClient(model, provider="openrouter").get_llm()
+
+        self.assertEqual(llm["model"], model)
+        self.assertEqual(llm["base_url"], "https://openrouter.ai/api/v1")
+        self.assertEqual(warning_records, [])
+
+
+if __name__ == "__main__":
+    unittest.main()

tradingagents/llm_clients/TODO.md

@@ -2,8 +2,8 @@
 
 ## Issues to Fix
 
-### 1. `validate_model()` is never called
-- Add validation call in `get_llm()` with warning (not error) for unknown models
+### 1. Resolved: `validate_model()` is now called in `get_llm()`
+- Added shared warning-based validation via `warn_if_unknown_model()` in each provider client
 
 ### 2. Inconsistent parameter handling
 | Client | API Key Param | Special Params |