fix(anthropic): handle thinking response blocks

src/outlines/models/anthropic.py

@@ -194,7 +194,10 @@ def generate(
                 **messages,
                 **inference_kwargs,
             )
-        return completion.content[0].text
+        for block in completion.content:
+            if block.type == "text":
+                return block.text
+        raise ValueError("Anthropic response did not contain a text block.")
 
     def generate_batch(
         self,

tests/models/test_anthropic.py

@@ -1,7 +1,10 @@
 import io
+from types import SimpleNamespace
 from typing import Generator
+from unittest.mock import MagicMock
 
 from anthropic import Anthropic as AnthropicClient
+from anthropic.types import TextBlock, ThinkingBlock
 from PIL import Image as PILImage
 import pytest
 
@@ -83,6 +86,24 @@ def __init__(self, foo):
         model.generate("prompt", Foo(1))
 
 
+def test_anthropic_response_uses_text_after_thinking_block():
+    client = MagicMock()
+    client.messages.create.return_value = SimpleNamespace(
+        content=[
+            ThinkingBlock(
+                signature="signature",
+                thinking="internal reasoning",
+                type="thinking",
+            ),
+            TextBlock(text="final answer", type="text"),
+        ]
+    )
+
+    model = Anthropic(client, MODEL_NAME)
+
+    assert model.generate("prompt", max_tokens=1) == "final answer"
+
+
 @pytest.mark.api_call
 def test_anthropic_simple_call(model):
     result = model.generate("Respond with one word. Not more.", max_tokens=1024)