fix(llm): route http_client to the matching sync/async Anthropic client

AGENTS.md

@@ -97,6 +97,7 @@ ENVIRONMENT MANAGEMENT:
 - `WeakKeyDictionary` works for caching per-driver since `neo4j.Driver` is hashable
 - Neo4j 2026 CREATE VECTOR INDEX syntax: WITH clause must come BEFORE OPTIONS, not after
 - E2E tests for SEARCH clause: use `docker compose -f tests/e2e/docker-compose.neo4j2026.yml up -d`
+- If `tests/unit/llm/test_anthropic_llm.py` fails with `AttributeError: module 'anthropic' has no attribute 'omit'`, or other unit test files error on missing optional-dependency imports (openai, cohere, etc.) at collection time, the local `.venv` is stale relative to `pyproject.toml` extras. Run `uv sync --all-extras` to fix.
 
 ---
 

CHANGELOG.md

@@ -10,6 +10,10 @@
 
 - (**breaking**) `AnthropicLLM.supports_structured_output` is now `True`. As a result, `SchemaFromTextExtractor` and `LLMEntityRelationExtractor` (and `SimpleKGPipeline`, which enables structured output automatically when the LLM supports it) now use structured output by default with `AnthropicLLM`. This requires a Claude 4.5+ model (e.g. `claude-sonnet-4-5`); using `AnthropicLLM` with an older Claude model in these components will now raise an error where it previously worked. To keep the previous behavior, use a Claude 4.5+ model, or construct `LLMEntityRelationExtractor` / `SchemaFromTextExtractor` directly with `use_structured_output=False`.
 
+### Fixed
+
+- Fixed a bug in `AnthropicLLM` where an `http_client` passed via kwargs (whether an `httpx.Client` or `httpx.AsyncClient`) was forwarded to both the sync `anthropic.Anthropic` and async `anthropic.AsyncAnthropic` clients, causing a type mismatch. `http_client` is now routed to the matching sync/async client only; other kwargs remain shared. An `http_client` of an unrecognized type now emits a warning and is ignored instead of raising, matching `OpenAILLM`'s existing behavior.
+
 ## 1.18.0
 
 ### Changed

src/neo4j_graphrag/llm/anthropic_llm.py

@@ -14,6 +14,7 @@
 from __future__ import annotations
 
 import json
+import warnings
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -25,6 +26,12 @@
     cast,
 )
 
+# 3rd party dependencies
+try:
+    import httpx
+except ImportError:
+    httpx = None  # type: ignore[assignment]
+
 from pydantic import BaseModel, ValidationError
 
 from neo4j_graphrag.exceptions import LLMGenerationError
@@ -218,8 +225,20 @@ def __init__(
             **kwargs,
         )
         self.anthropic = anthropic
-        self.client = anthropic.Anthropic(**kwargs)
-        self.async_client = anthropic.AsyncAnthropic(**kwargs)
+        http_client = kwargs.pop("http_client", None)
+        sync_params = kwargs.copy()
+        async_params = kwargs.copy()
+        if httpx is not None and isinstance(http_client, httpx.Client):
+            sync_params["http_client"] = http_client
+        elif httpx is not None and isinstance(http_client, httpx.AsyncClient):
+            async_params["http_client"] = http_client
+        elif http_client is not None:
+            warnings.warn(
+                f"Invalid http_client type (got {type(http_client)}, expected httpx.Client or httpx.AsyncClient). Using default client.",
+                stacklevel=2,
+            )
+        self.client = anthropic.Anthropic(**sync_params)
+        self.async_client = anthropic.AsyncAnthropic(**async_params)
 
     def invoke(
         self,

tests/unit/llm/test_anthropic_llm.py

@@ -19,6 +19,7 @@
 from unittest.mock import AsyncMock, MagicMock, Mock, patch
 
 import anthropic
+import httpx
 import pytest
 from neo4j_graphrag.exceptions import LLMGenerationError
 from neo4j_graphrag.experimental.components.types import Neo4jGraph
@@ -538,6 +539,66 @@ def test_anthropic_llm_close(mock_anthropic: Mock) -> None:
     mock_anthropic.AsyncAnthropic.return_value.close.assert_called_once()
 
 
+# ---------------------------------------------------------------------------
+# http_client sync/async routing tests
+# ---------------------------------------------------------------------------
+
+
+def test_anthropic_llm_with_httpx_client(mock_anthropic: Mock) -> None:
+    """Test that httpx.Client is forwarded only to the sync Anthropic client."""
+    http_client = httpx.Client()
+    try:
+        with warnings.catch_warnings(record=True) as caught:
+            warnings.simplefilter("always")
+            AnthropicLLM(model_name="claude-3-opus-20240229", http_client=http_client)
+
+        assert not any("Invalid http_client" in str(w.message) for w in caught)
+        _, sync_kwargs = mock_anthropic.Anthropic.call_args
+        assert sync_kwargs.get("http_client") is http_client
+        _, async_kwargs = mock_anthropic.AsyncAnthropic.call_args
+        assert "http_client" not in async_kwargs
+    finally:
+        http_client.close()
+
+
+@pytest.mark.asyncio
+async def test_anthropic_llm_with_httpx_async_client(mock_anthropic: Mock) -> None:
+    """Test that httpx.AsyncClient is forwarded only to the async Anthropic client."""
+    async_http_client = httpx.AsyncClient()
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        AnthropicLLM(model_name="claude-3-opus-20240229", http_client=async_http_client)
+
+    assert not any("Invalid http_client" in str(w.message) for w in caught)
+    _, sync_kwargs = mock_anthropic.Anthropic.call_args
+    assert "http_client" not in sync_kwargs
+    _, async_kwargs = mock_anthropic.AsyncAnthropic.call_args
+    assert async_kwargs.get("http_client") is async_http_client
+
+    await async_http_client.aclose()
+
+
+def test_anthropic_llm_no_http_client_no_warning(mock_anthropic: Mock) -> None:
+    """Test that omitting http_client does not emit a warning."""
+    with warnings.catch_warnings(record=True) as caught:
+        warnings.simplefilter("always")
+        AnthropicLLM(model_name="claude-3-opus-20240229")
+
+    assert not any("Invalid http_client" in str(w.message) for w in caught)
+
+
+def test_anthropic_llm_with_invalid_http_client_warns(mock_anthropic: Mock) -> None:
+    """Test that an invalid http_client type emits a warning and falls back to
+    default construction for both clients."""
+    with pytest.warns(UserWarning, match="Invalid http_client type"):
+        AnthropicLLM(model_name="claude-3-opus-20240229", http_client="not-a-client")
+
+    _, sync_kwargs = mock_anthropic.Anthropic.call_args
+    _, async_kwargs = mock_anthropic.AsyncAnthropic.call_args
+    assert "http_client" not in sync_kwargs
+    assert "http_client" not in async_kwargs
+
+
 @pytest.mark.asyncio
 async def test_anthropic_llm_aclose(mock_anthropic: Mock) -> None:
     mock_anthropic.AsyncAnthropic.return_value.close = AsyncMock()