Fixes bug pointed out by @dsaluja (https://github.com/dsaluja)

Fixes other providers not fixed by https://github.com/BeehiveInnovations/zen-mcp-server/pull/66
New regression tests

tests/test_openai_compatible_token_usage.py

@@ -0,0 +1,135 @@
+"""Tests for OpenAI-compatible provider token usage extraction."""
+
+import unittest
+from unittest.mock import Mock
+
+from providers.openai_compatible import OpenAICompatibleProvider
+
+
+class TestOpenAICompatibleTokenUsage(unittest.TestCase):
+    """Test OpenAI-compatible provider token usage handling."""
+
+    def setUp(self):
+        """Set up test fixtures."""
+
+        # Create a concrete implementation for testing
+        class TestProvider(OpenAICompatibleProvider):
+            FRIENDLY_NAME = "Test"
+            SUPPORTED_MODELS = {"test-model": {"context_window": 4096}}
+
+            def get_capabilities(self, model_name):
+                return Mock()
+
+            def get_provider_type(self):
+                return Mock()
+
+            def validate_model_name(self, model_name):
+                return True
+
+        self.provider = TestProvider("test-key")
+
+    def test_extract_usage_with_valid_tokens(self):
+        """Test token extraction with valid token counts."""
+        response = Mock()
+        response.usage = Mock()
+        response.usage.prompt_tokens = 100
+        response.usage.completion_tokens = 50
+        response.usage.total_tokens = 150
+
+        usage = self.provider._extract_usage(response)
+
+        self.assertEqual(usage["input_tokens"], 100)
+        self.assertEqual(usage["output_tokens"], 50)
+        self.assertEqual(usage["total_tokens"], 150)
+
+    def test_extract_usage_with_none_prompt_tokens(self):
+        """Test token extraction when prompt_tokens is None (regression test for bug)."""
+        response = Mock()
+        response.usage = Mock()
+        response.usage.prompt_tokens = None  # This was causing crashes
+        response.usage.completion_tokens = 50
+        response.usage.total_tokens = None
+
+        usage = self.provider._extract_usage(response)
+
+        # Should default to 0 when None
+        self.assertEqual(usage["input_tokens"], 0)
+        self.assertEqual(usage["output_tokens"], 50)
+        self.assertEqual(usage["total_tokens"], 0)
+
+    def test_extract_usage_with_none_completion_tokens(self):
+        """Test token extraction when completion_tokens is None (regression test for bug)."""
+        response = Mock()
+        response.usage = Mock()
+        response.usage.prompt_tokens = 100
+        response.usage.completion_tokens = None  # This was causing crashes
+        response.usage.total_tokens = None
+
+        usage = self.provider._extract_usage(response)
+
+        self.assertEqual(usage["input_tokens"], 100)
+        # Should default to 0 when None
+        self.assertEqual(usage["output_tokens"], 0)
+        self.assertEqual(usage["total_tokens"], 0)
+
+    def test_extract_usage_with_all_none_tokens(self):
+        """Test token extraction when all token counts are None."""
+        response = Mock()
+        response.usage = Mock()
+        response.usage.prompt_tokens = None
+        response.usage.completion_tokens = None
+        response.usage.total_tokens = None
+
+        usage = self.provider._extract_usage(response)
+
+        # Should default to 0 for all when None
+        self.assertEqual(usage["input_tokens"], 0)
+        self.assertEqual(usage["output_tokens"], 0)
+        self.assertEqual(usage["total_tokens"], 0)
+
+    def test_extract_usage_without_usage(self):
+        """Test token extraction when response has no usage."""
+        response = Mock(spec=[])  # No usage attribute
+
+        usage = self.provider._extract_usage(response)
+
+        # Should return empty dict
+        self.assertEqual(usage, {})
+
+    def test_extract_usage_with_zero_tokens(self):
+        """Test token extraction with zero token counts."""
+        response = Mock()
+        response.usage = Mock()
+        response.usage.prompt_tokens = 0
+        response.usage.completion_tokens = 0
+        response.usage.total_tokens = 0
+
+        usage = self.provider._extract_usage(response)
+
+        self.assertEqual(usage["input_tokens"], 0)
+        self.assertEqual(usage["output_tokens"], 0)
+        self.assertEqual(usage["total_tokens"], 0)
+
+    def test_alternative_token_format_with_none(self):
+        """Test alternative token format (input_tokens/output_tokens) with None values."""
+        # This tests the other code path in generate_content_openai_responses
+        # Simulate a response with input_tokens/output_tokens attributes that could be None
+        response = Mock()
+        response.input_tokens = None  # This was causing crashes
+        response.output_tokens = 50
+
+        # Test the pattern: getattr(response, "input_tokens", 0) or 0
+        input_tokens = getattr(response, "input_tokens", 0) or 0
+        output_tokens = getattr(response, "output_tokens", 0) or 0
+
+        # Should not crash and should handle None gracefully
+        self.assertEqual(input_tokens, 0)
+        self.assertEqual(output_tokens, 50)
+
+        # Test that addition works
+        total = input_tokens + output_tokens
+        self.assertEqual(total, 50)
+
+
+if __name__ == "__main__":
+    unittest.main()