fix(anthropic): handle empty response.content safely to prevent IndexError

Closes #178

Author: abhi-0203

rlm/clients/anthropic.py

@@ -44,7 +44,8 @@ def completion(self, prompt: str | list[dict[str, Any]], model: str | None = Non
 
         response = self.client.messages.create(**kwargs)
         self._track_cost(response, model)
-        return response.content[0].text
+        texts = [b.text for b in response.content if getattr(b, "type", "") == "text"]
+        return texts[0] if texts else ""
 
     async def acompletion(
         self, prompt: str | list[dict[str, Any]], model: str | None = None
@@ -61,7 +62,8 @@ async def acompletion(
 
         response = await self.async_client.messages.create(**kwargs)
         self._track_cost(response, model)
-        return response.content[0].text
+        texts = [b.text for b in response.content if getattr(b, "type", "") == "text"]
+        return texts[0] if texts else ""
 
     def _prepare_messages(
         self, prompt: str | list[dict[str, Any]]

tests/clients/test_anthropic.py

@@ -0,0 +1,60 @@
+"""Tests for the Anthropic client."""
+
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from rlm.clients.anthropic import AnthropicClient
+from rlm.core.types import ModelUsageSummary, UsageSummary
+
+
+class TestAnthropicClientUnit:
+    """Unit tests that don't require API calls."""
+
+    def test_init_with_api_key(self):
+        """Test client initialization with explicit API key."""
+        with patch("rlm.clients.anthropic.anthropic.Anthropic"):
+            with patch("rlm.clients.anthropic.anthropic.AsyncAnthropic"):
+                client = AnthropicClient(api_key="test-key", model_name="claude-3-5-sonnet")
+                assert client.model_name == "claude-3-5-sonnet"
+
+    def test_completion_empty_content(self):
+        """Test completion returns empty string when response.content is empty."""
+        mock_response = MagicMock()
+        mock_response.content = []
+        mock_response.usage.input_tokens = 10
+        mock_response.usage.output_tokens = 0
+
+        with patch("rlm.clients.anthropic.anthropic.Anthropic") as mock_client_class:
+            mock_client = MagicMock()
+            mock_client.messages.create.return_value = mock_response
+            mock_client_class.return_value = mock_client
+
+            with patch("rlm.clients.anthropic.anthropic.AsyncAnthropic"):
+                client = AnthropicClient(api_key="test-key", model_name="claude-3-5-sonnet")
+                result = client.completion("Hello")
+
+                assert result == ""
+
+    def test_completion_with_text_content(self):
+        """Test completion returns text when response.content has text blocks."""
+        mock_block = MagicMock()
+        mock_block.type = "text"
+        mock_block.text = "Hello from Claude!"
+
+        mock_response = MagicMock()
+        mock_response.content = [mock_block]
+        mock_response.usage.input_tokens = 10
+        mock_response.usage.output_tokens = 5
+
+        with patch("rlm.clients.anthropic.anthropic.Anthropic") as mock_client_class:
+            mock_client = MagicMock()
+            mock_client.messages.create.return_value = mock_response
+            mock_client_class.return_value = mock_client
+
+            with patch("rlm.clients.anthropic.anthropic.AsyncAnthropic"):
+                client = AnthropicClient(api_key="test-key", model_name="claude-3-5-sonnet")
+                result = client.completion("Hello")
+
+                assert result == "Hello from Claude!"