Add LLMProviderError for provider-level error detection

- Introduce LLMProviderError to distinguish provider API errors (rate
  limits, auth failures, safety blocks) from response format issues
- Add _raise_provider_error helper that checks error dict, error string,
  and Gemini promptFeedback.blockReason before content extraction

Author: johnteee

teaagent/__init__.py

@@ -39,6 +39,7 @@
     LLMConfigurationError,
     LLMHTTPError,
     LLMMessage,
+    LLMProviderError,
     LLMRequest,
     LLMResponse,
     LLMResponseFormatError,
@@ -144,6 +145,7 @@
     'LLMConfigurationError',
     'LLMHTTPError',
     'LLMMessage',
+    'LLMProviderError',
     'LLMRequest',
     'LLMResponse',
     'LLMResponseFormatError',

teaagent/llm.py

@@ -21,6 +21,10 @@ class LLMHTTPError(LLMAdapterError):
     pass
 
 
+class LLMProviderError(LLMAdapterError):
+    pass
+
+
 class LLMResponseFormatError(LLMAdapterError):
     pass
 
@@ -330,6 +334,7 @@ def complete(self, request: LLMRequest) -> LLMResponse:
 
 
 def _extract_openai_content(provider: str, response: dict[str, Any]) -> str:
+    _raise_provider_error(provider, response)
     choices = response.get('choices')
     if not isinstance(choices, list) or not choices:
         raise LLMResponseFormatError(f'{provider} response missing choices')
@@ -359,6 +364,7 @@ def _first_choice_delta(provider: str, response: dict[str, Any]) -> dict[str, An
 
 
 def _extract_claude_content(response: dict[str, Any]) -> str:
+    _raise_provider_error('claude', response)
     content_blocks = response.get('content')
     if not isinstance(content_blocks, list):
         raise LLMResponseFormatError('claude response missing content blocks')
@@ -374,6 +380,7 @@ def _extract_claude_content(response: dict[str, Any]) -> str:
 
 
 def _extract_gemini_content(response: dict[str, Any]) -> str:
+    _raise_provider_error('gemini', response)
     candidates = response.get('candidates')
     if not isinstance(candidates, list) or not candidates:
         raise LLMResponseFormatError('gemini response missing candidates')
@@ -396,6 +403,20 @@ def _extract_gemini_content(response: dict[str, Any]) -> str:
     return text
 
 
+def _raise_provider_error(provider: str, response: dict[str, Any]) -> None:
+    error = response.get('error')
+    if isinstance(error, dict):
+        message = error.get('message') or error.get('status') or error
+        raise LLMProviderError(f'{provider} provider error: {message}')
+    if isinstance(error, str):
+        raise LLMProviderError(f'{provider} provider error: {error}')
+    prompt_feedback = response.get('promptFeedback')
+    if isinstance(prompt_feedback, dict) and prompt_feedback.get('blockReason'):
+        raise LLMProviderError(
+            f'{provider} provider blocked prompt: {prompt_feedback["blockReason"]}'
+        )
+
+
 PROVIDER_CONFIGS = {
     'claude': ProviderConfig(
         name='claude',

tests/test_llm.py

@@ -9,6 +9,7 @@
 
 from teaagent import (
     LLMMessage,
+    LLMProviderError,
     LLMRequest,
     LLMResponseFormatError,
     available_providers,
@@ -223,11 +224,19 @@ def test_openai_streaming_reads_sse_lines_incrementally(self) -> None:
         self.assertEqual(result.input_tokens, 2)
         self.assertEqual(result.output_tokens, 3)
 
-    def test_openai_adapter_rejects_malformed_response(self) -> None:
+    def test_openai_adapter_reports_provider_error_payload(self) -> None:
         transport = FakeTransport({'error': {'message': 'blocked'}})
         with patch.dict(os.environ, {'OPENAI_API_KEY': 'key'}, clear=True):
             adapter = create_llm_adapter('gpt', transport=transport, model='gpt-test')
 
+            with self.assertRaises(LLMProviderError):
+                adapter.complete(LLMRequest(messages=[LLMMessage('user', 'hi')]))
+
+    def test_openai_adapter_rejects_malformed_response(self) -> None:
+        transport = FakeTransport({'choices': []})
+        with patch.dict(os.environ, {'OPENAI_API_KEY': 'key'}, clear=True):
+            adapter = create_llm_adapter('gpt', transport=transport, model='gpt-test')
+
             with self.assertRaises(LLMResponseFormatError):
                 adapter.complete(LLMRequest(messages=[LLMMessage('user', 'hi')]))
 
@@ -240,13 +249,21 @@ def test_claude_adapter_rejects_malformed_response(self) -> None:
                 adapter.complete(LLMRequest(messages=[LLMMessage('user', 'hi')]))
 
     def test_gemini_adapter_rejects_malformed_response(self) -> None:
-        transport = FakeTransport({'promptFeedback': {'blockReason': 'SAFETY'}})
+        transport = FakeTransport({'candidates': [{'content': {'parts': []}}]})
         with patch.dict(os.environ, {'GEMINI_API_KEY': 'key'}, clear=True):
             adapter = create_llm_adapter('gemini', transport=transport)
 
             with self.assertRaises(LLMResponseFormatError):
                 adapter.complete(LLMRequest(messages=[LLMMessage('user', 'hi')]))
 
+    def test_gemini_adapter_reports_safety_block(self) -> None:
+        transport = FakeTransport({'promptFeedback': {'blockReason': 'SAFETY'}})
+        with patch.dict(os.environ, {'GEMINI_API_KEY': 'key'}, clear=True):
+            adapter = create_llm_adapter('gemini', transport=transport)
+
+            with self.assertRaises(LLMProviderError):
+                adapter.complete(LLMRequest(messages=[LLMMessage('user', 'hi')]))
+
 
 if __name__ == '__main__':
     unittest.main()