feat(client): allow passing async httpx client

langfuse/_client/client.py

@@ -155,7 +155,8 @@ class Langfuse:
         base_url (Optional[str]): The Langfuse API base URL. Defaults to "https://cloud.langfuse.com". Can also be set via LANGFUSE_BASE_URL environment variable.
         host (Optional[str]): Deprecated. Use base_url instead. The Langfuse API host URL. Defaults to "https://cloud.langfuse.com".
         timeout (Optional[int]): Timeout in seconds for API requests. Defaults to 5 seconds.
-        httpx_client (Optional[httpx.Client]): Custom httpx client for making non-tracing HTTP requests. If not provided, a default client will be created.
+        httpx_client (Optional[httpx.Client]): Custom synchronous httpx client for making non-tracing HTTP requests. If not provided, a default client will be created.
+        async_httpx_client (Optional[httpx.AsyncClient]): Custom asynchronous httpx client for `client.async_api`. If not provided, a default async client will be created.
         debug (bool): Enable debug logging. Defaults to False. Can also be set via LANGFUSE_DEBUG environment variable.
         tracing_enabled (Optional[bool]): Enable or disable tracing. Defaults to True. Can also be set via LANGFUSE_TRACING_ENABLED environment variable.
         flush_at (Optional[int]): Number of spans to batch before sending to the API. Defaults to 512. Can also be set via LANGFUSE_FLUSH_AT environment variable.
@@ -179,7 +180,7 @@ class Langfuse:
             )
             ```
         should_export_span (Optional[Callable[[ReadableSpan], bool]]): Callback to decide whether to export a span. If omitted, Langfuse uses the default filter (Langfuse SDK spans, spans with `gen_ai.*` attributes, and known LLM instrumentation scopes).
-        additional_headers (Optional[Dict[str, str]]): Additional headers to include in all API requests and OTLPSpanExporter requests. These headers will be merged with default headers. Note: If httpx_client is provided, additional_headers must be set directly on your custom httpx_client as well.
+        additional_headers (Optional[Dict[str, str]]): Additional headers to include in all API requests and OTLPSpanExporter requests. These headers will be merged with default headers. Note: If `httpx_client` or `async_httpx_client` is provided, `additional_headers` must be set directly on your custom client as well.
         tracer_provider(Optional[TracerProvider]): OpenTelemetry TracerProvider to use for Langfuse. This can be useful to set to have disconnected tracing between Langfuse and other OpenTelemetry-span emitting libraries. Note: To track active spans, the context is still shared between TracerProviders. This may lead to broken trace trees.
 
     Example:
@@ -231,6 +232,7 @@ def __init__(
         host: Optional[str] = None,
         timeout: Optional[int] = None,
         httpx_client: Optional[httpx.Client] = None,
+        async_httpx_client: Optional[httpx.AsyncClient] = None,
         debug: bool = False,
         tracing_enabled: Optional[bool] = True,
         flush_at: Optional[int] = None,
@@ -332,6 +334,7 @@ def __init__(
             flush_at=flush_at,
             flush_interval=flush_interval,
             httpx_client=httpx_client,
+            async_httpx_client=async_httpx_client,
             media_upload_thread_count=media_upload_thread_count,
             sample_rate=sample_rate,
             mask=mask,

langfuse/_client/get_client.py

@@ -55,6 +55,7 @@ def _create_client_from_instance(
         additional_headers=instance.additional_headers,
         tracer_provider=instance.tracer_provider,
         httpx_client=instance.httpx_client,
+        async_httpx_client=instance.async_httpx_client,
     )
 
 

langfuse/_client/resource_manager.py

@@ -90,6 +90,7 @@ def __new__(
         flush_at: Optional[int] = None,
         flush_interval: Optional[float] = None,
         httpx_client: Optional[httpx.Client] = None,
+        async_httpx_client: Optional[httpx.AsyncClient] = None,
         media_upload_thread_count: Optional[int] = None,
         sample_rate: Optional[float] = None,
         mask: Optional[MaskFunction] = None,
@@ -123,6 +124,7 @@ def __new__(
                     flush_at=flush_at,
                     flush_interval=flush_interval,
                     httpx_client=httpx_client,
+                    async_httpx_client=async_httpx_client,
                     media_upload_thread_count=media_upload_thread_count,
                     sample_rate=sample_rate,
                     mask=mask,
@@ -152,6 +154,7 @@ def _initialize_instance(
         flush_interval: Optional[float] = None,
         media_upload_thread_count: Optional[int] = None,
         httpx_client: Optional[httpx.Client] = None,
+        async_httpx_client: Optional[httpx.AsyncClient] = None,
         sample_rate: Optional[float] = None,
         mask: Optional[MaskFunction] = None,
         tracing_enabled: bool = True,
@@ -218,6 +221,15 @@ def _initialize_instance(
             client_headers = additional_headers if additional_headers else {}
             self.httpx_client = httpx.Client(timeout=timeout, headers=client_headers)
 
+        if async_httpx_client is not None:
+            self.async_httpx_client = async_httpx_client
+        else:
+            async_client_headers = additional_headers if additional_headers else {}
+            self.async_httpx_client = httpx.AsyncClient(
+                timeout=timeout,
+                headers=async_client_headers,
+            )
+
         self.api = LangfuseAPI(
             base_url=base_url,
             username=self.public_key,
@@ -235,6 +247,7 @@ def _initialize_instance(
             x_langfuse_sdk_name="python",
             x_langfuse_sdk_version=langfuse_version,
             x_langfuse_public_key=self.public_key,
+            httpx_client=self.async_httpx_client,
             timeout=timeout,
         )
         score_ingestion_client = LangfuseClient(

tests/test_additional_headers_simple.py

@@ -3,6 +3,8 @@
 This module tests that additional headers are properly configured in the HTTP clients.
 """
 
+import asyncio
+
 import httpx
 
 from langfuse._client.client import Langfuse
@@ -115,6 +117,28 @@ def test_media_manager_uses_custom_httpx_client(self):
         assert langfuse._resources is not None
         assert langfuse._resources._media_manager._httpx_client is custom_client
 
+    def test_async_api_uses_custom_async_httpx_client(self):
+        """Test that async_api reuses the configured custom async httpx client."""
+        custom_async_client = httpx.AsyncClient()
+
+        try:
+            langfuse = Langfuse(
+                public_key="test-public-key",
+                secret_key="test-secret-key",
+                host="https://mock-host.com",
+                async_httpx_client=custom_async_client,
+                tracing_enabled=False,
+            )
+
+            assert langfuse._resources is not None
+            assert langfuse._resources.async_httpx_client is custom_async_client
+            assert (
+                langfuse.async_api._client_wrapper.httpx_client.httpx_client
+                is custom_async_client
+            )
+        finally:
+            asyncio.run(custom_async_client.aclose())
+
     def test_none_additional_headers_works(self):
         """Test that passing None for additional_headers works without errors."""
         langfuse = Langfuse(

tests/test_resource_manager.py

@@ -1,5 +1,9 @@
 """Test the LangfuseResourceManager and get_client() function."""
 
+import asyncio
+
+import httpx
+
 from langfuse import Langfuse
 from langfuse._client.get_client import get_client
 from langfuse._client.resource_manager import LangfuseResourceManager
@@ -94,3 +98,30 @@ def should_export_b(span):
 
     client_a.shutdown()
     client_b.shutdown()
+
+
+def test_get_client_preserves_custom_async_httpx_client():
+    """Test that get_client() preserves the custom async httpx client."""
+    with LangfuseResourceManager._lock:
+        LangfuseResourceManager._instances.clear()
+
+    custom_async_client = httpx.AsyncClient()
+
+    try:
+        Langfuse(
+            public_key="pk-async-client",
+            secret_key="sk-async-client",
+            async_httpx_client=custom_async_client,
+            tracing_enabled=False,
+        )
+        retrieved_client = get_client()
+
+        assert retrieved_client._resources is not None
+        assert retrieved_client._resources.async_httpx_client is custom_async_client
+        assert (
+            retrieved_client.async_api._client_wrapper.httpx_client.httpx_client
+            is custom_async_client
+        )
+    finally:
+        LangfuseResourceManager.reset()
+        asyncio.run(custom_async_client.aclose())