diff --git a/CLAUDE.md b/CLAUDE.md
index ffb1e50f..bf229cc1 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -40,6 +40,81 @@ The package provides the `agentex` CLI with these main commands:
 - Debug agents: `agentex agents run --manifest manifest.yaml --debug-worker`
 - Debug with custom port: `agentex agents run --manifest manifest.yaml --debug-worker --debug-port 5679`
 
+### Custom OpenAI Client for Agents SDK
+
+Configure custom OpenAI clients **specifically for the OpenAI Agents SDK** integration (Agent and Runner classes).
+
+⚠️ **Scope**: This configuration ONLY affects OpenAI Agents SDK operations. It does NOT affect:
+- LiteLLM integration (configure LiteLLM separately via environment variables or LiteLLM config)
+- SGP integration
+- Direct OpenAI API calls
+
+#### Requirements
+- Must use **async** client: `AsyncOpenAI` or `AsyncAzureOpenAI`
+- Sync clients (`OpenAI`) are not supported by the Agents SDK
+
+#### Basic Usage (Custom Endpoint)
+
+Use this for custom OpenAI-compatible endpoints such as LiteLLM proxy for cost tracking:
+
+```python
+from openai import AsyncOpenAI
+from agentex.lib.adk.providers._modules.openai_agents_config import (
+    initialize_openai_agents_client
+)
+
+# Configure custom endpoint
+client = AsyncOpenAI(
+    base_url="https://your-proxy.com/v1",
+    api_key=os.getenv("CUSTOM_API_KEY")
+)
+initialize_openai_agents_client(client)
+```
+
+#### Azure OpenAI
+
+```python
+from openai import AsyncAzureOpenAI
+from agentex.lib.adk.providers._modules.openai_agents_config import (
+    initialize_openai_agents_client
+)
+
+client = AsyncAzureOpenAI(
+    azure_endpoint=os.getenv("AZURE_OPENAI_ENDPOINT"),
+    api_key=os.getenv("AZURE_OPENAI_KEY"),
+    api_version="2024-02-01"
+)
+initialize_openai_agents_client(client)
+```
+
+#### Temporal Workers
+
+Call `initialize_openai_agents_client()` in your worker startup script **BEFORE** starting the worker:
+
+```python
+# run_worker.py
+import os
+from openai import AsyncOpenAI
+from agentex.lib.adk.providers._modules.openai_agents_config import (
+    initialize_openai_agents_client
+)
+
+# Step 1: Configure client before starting worker
+if os.getenv("CUSTOM_OPENAI_BASE_URL"):
+    client = AsyncOpenAI(
+        base_url=os.getenv("CUSTOM_OPENAI_BASE_URL"),
+        api_key=os.getenv("OPENAI_API_KEY")
+    )
+    initialize_openai_agents_client(client)
+
+# Step 2: Start worker (all agent operations will use configured client)
+# ... worker startup code ...
+```
+
+#### Backward Compatibility
+
+If `initialize_openai_agents_client()` is not called, the OpenAI Agents SDK uses default OpenAI configuration via the `OPENAI_API_KEY` environment variable. All existing code continues to work without changes.
+
 ## Architecture Overview
 
 ### Code Structure
diff --git a/src/agentex/lib/adk/providers/_modules/openai_agents_config.py b/src/agentex/lib/adk/providers/_modules/openai_agents_config.py
new file mode 100644
index 00000000..ddd1292a
--- /dev/null
+++ b/src/agentex/lib/adk/providers/_modules/openai_agents_config.py
@@ -0,0 +1,116 @@
+"""
+OpenAI Agents SDK Client Configuration
+
+Configures custom OpenAI clients specifically for the OpenAI Agents SDK.
+This affects ONLY the OpenAI Agents SDK integration (Agent and Runner).
+
+For LiteLLM integration, use separate LiteLLM configuration methods.
+"""
+
+from typing import Union
+from openai import AsyncOpenAI, AsyncAzureOpenAI
+from agents import set_default_openai_client
+from agentex.lib.utils.logging import make_logger
+
+logger = make_logger(__name__)
+
+# Type alias for supported async OpenAI clients
+AsyncOpenAIClient = Union[AsyncOpenAI, AsyncAzureOpenAI]
+
+_client_initialized = False
+
+
+def initialize_openai_agents_client(client: AsyncOpenAIClient) -> None:
+    """
+    Initialize custom OpenAI client for OpenAI Agents SDK operations.
+
+    ⚠️ IMPORTANT: This ONLY affects the OpenAI Agents SDK integration
+    (Agent and Runner classes). It does NOT affect:
+    - LiteLLM integration (use LiteLLM configuration separately)
+    - SGP integration
+    - Direct OpenAI API calls
+
+    This should be called ONCE at application or worker startup, before any
+    agents are created using the OpenAI Agents SDK.
+
+    Args:
+        client: Pre-configured async OpenAI client (AsyncOpenAI or AsyncAzureOpenAI)
+
+    Raises:
+        TypeError: If a non-async client is passed (will be caught by type checker)
+
+    Examples:
+        # Custom endpoint (e.g., LiteLLM proxy for cost tracking):
+        from openai import AsyncOpenAI
+        from agentex.lib.adk.providers._modules.openai_agents_config import (
+            initialize_openai_agents_client
+        )
+
+        client = AsyncOpenAI(
+            base_url="https://your-proxy.com/v1",
+            api_key=os.getenv("CUSTOM_API_KEY")
+        )
+        initialize_openai_agents_client(client)
+
+        # Azure OpenAI:
+        from openai import AsyncAzureOpenAI
+
+        client = AsyncAzureOpenAI(
+            azure_endpoint=os.getenv("AZURE_OPENAI_ENDPOINT"),
+            api_key=os.getenv("AZURE_OPENAI_KEY"),
+            api_version="2024-02-01"
+        )
+        initialize_openai_agents_client(client)
+
+        # For Temporal workers, call this in worker startup:
+        # run_worker.py:
+        #   initialize_openai_agents_client(client)
+        #   # Then start worker...
+
+    Note:
+        If not called, the OpenAI Agents SDK uses default OpenAI configuration
+        via the OPENAI_API_KEY environment variable.
+    """
+    global _client_initialized
+
+    if _client_initialized:
+        logger.warning(
+            "OpenAI Agents SDK client already initialized. "
+            "Ignoring subsequent initialization. "
+            "This may indicate multiple workers or initialization calls."
+        )
+        return
+
+    # Runtime validation for async client
+    if not isinstance(client, (AsyncOpenAI, AsyncAzureOpenAI)):
+        raise TypeError(
+            f"Client must be AsyncOpenAI or AsyncAzureOpenAI, got {type(client).__name__}. "
+            f"The OpenAI Agents SDK requires async clients. "
+            f"Use AsyncOpenAI instead of OpenAI."
+        )
+
+    set_default_openai_client(client)
+    logger.info(f"OpenAI Agents SDK client configured: {type(client).__name__}")
+
+    _client_initialized = True
+
+
+def is_openai_agents_client_initialized() -> bool:
+    """
+    Check if custom OpenAI Agents SDK client has been initialized.
+
+    Returns:
+        bool: True if initialize_openai_agents_client() has been called
+    """
+    return _client_initialized
+
+
+def reset_openai_agents_client_initialization() -> None:
+    """
+    Reset initialization flag (primarily for testing).
+
+    Warning: This does NOT reset the actual client in the agents library,
+    only the initialization tracking flag in this module.
+    """
+    global _client_initialized
+    _client_initialized = False