diff --git a/README.md b/README.md
index 525e8f51..b086ed7d 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,7 @@ pip install -r requirements.txt
 #### OpenAI Models
 
 By default, the system uses the `OPENAI_API_KEY` environment variable for OpenAI models.
+Additionally, if you are using a custom OpenAI-compatible API endpoint (e.g., a local LLM server), you can specify its URL using the `BASE_URL` environment variable.
 
 #### Gemini Models
 
@@ -85,6 +86,10 @@ Our code can optionally use a Semantic Scholar API Key (`S2_API_KEY`) for higher
 Ensure you provide the necessary API keys as environment variables for the models you intend to use. For example:
 ```bash
 export OPENAI_API_KEY="YOUR_OPENAI_KEY_HERE"
+# Optional: For custom OpenAI-compatible endpoints
+# export BASE_URL="YOUR_CUSTOM_API_BASE_URL"
+
+# For Semantic Scholar API (Optional)
 export S2_API_KEY="YOUR_S2_KEY_HERE"
 # Set AWS credentials if using Bedrock
 # export AWS_ACCESS_KEY_ID="YOUR_AWS_ACCESS_KEY_ID"
diff --git a/ai_scientist/llm.py b/ai_scientist/llm.py
index afd85a41..ba1fde90 100644
--- a/ai_scientist/llm.py
+++ b/ai_scientist/llm.py
@@ -7,6 +7,7 @@
 import anthropic
 import backoff
 import openai
+import os
 
 MAX_NUM_TOKENS = 4096
 
@@ -426,12 +427,10 @@ def create_client(model) -> tuple[Any, str]:
         client_model = model.split("/")[-1]
         print(f"Using Vertex AI with model {client_model}.")
         return anthropic.AnthropicVertex(), client_model
-    elif "gpt" in model:
-        print(f"Using OpenAI API with model {model}.")
-        return openai.OpenAI(), model
-    elif "o1" in model or "o3" in model:
+    elif "gpt" in model or "o1" in model or "o3" in model:
         print(f"Using OpenAI API with model {model}.")
-        return openai.OpenAI(), model
+        base_url = os.getenv('BASE_URL')
+        return openai.OpenAI(base_url=base_url if base_url else None), model
     elif model == "deepseek-coder-v2-0724":
         print(f"Using OpenAI API with {model}.")
         return (
diff --git a/ai_scientist/treesearch/backend/backend_openai.py b/ai_scientist/treesearch/backend/backend_openai.py
index ae318ec4..6ac0721c 100644
--- a/ai_scientist/treesearch/backend/backend_openai.py
+++ b/ai_scientist/treesearch/backend/backend_openai.py
@@ -22,7 +22,9 @@
 @once
 def _setup_openai_client():
     global _client
-    _client = openai.OpenAI(max_retries=0)
+    import os
+    base_url = os.getenv('BASE_URL')
+    _client = openai.OpenAI(max_retries=0, base_url=base_url if base_url else None)
 
 
 def query(
diff --git a/ai_scientist/treesearch/log_summarization.py b/ai_scientist/treesearch/log_summarization.py
index 436cdd18..2aa3773b 100644
--- a/ai_scientist/treesearch/log_summarization.py
+++ b/ai_scientist/treesearch/log_summarization.py
@@ -8,9 +8,11 @@
 
 parent_dir = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", ".."))
 sys.path.insert(0, parent_dir)
+import os
 from ai_scientist.llm import get_response_from_llm, extract_json_between_markers
 
-client = openai.OpenAI()
+base_url = os.getenv('BASE_URL')
+client = openai.OpenAI(base_url=base_url if base_url else None)
 model = "gpt-4o-2024-08-06"
 
 report_summarizer_sys_msg = """You are an expert machine learning researcher.
diff --git a/ai_scientist/vlm.py b/ai_scientist/vlm.py
index 240015eb..5410cc2a 100644
--- a/ai_scientist/vlm.py
+++ b/ai_scientist/vlm.py
@@ -165,7 +165,9 @@ def create_client(model: str) -> tuple[Any, str]:
         "o3-mini",
     ]:
         print(f"Using OpenAI API with model {model}.")
-        return openai.OpenAI(), model
+        import os
+        base_url = os.getenv('BASE_URL')
+        return openai.OpenAI(base_url=base_url if base_url else None), model
     else:
         raise ValueError(f"Model {model} not supported.")