Make transformer lazy import

src/agentlab/llm/chat_api.py

@@ -8,12 +8,10 @@
 
 import anthropic
 import openai
-from huggingface_hub import InferenceClient
 from openai import NOT_GIVEN, OpenAI
 
 import agentlab.llm.tracking as tracking
 from agentlab.llm.base_api import AbstractChatModel, BaseModelArgs
-from agentlab.llm.huggingface_utils import HFBaseChatModel
 from agentlab.llm.llm_utils import AIMessage, Discussion
 
 
@@ -139,6 +137,8 @@ def make_model(self):
                 self.model_url = os.environ["AGENTLAB_MODEL_URL"]
             if self.token is None:
                 self.token = os.environ["AGENTLAB_MODEL_TOKEN"]
+            # Lazy import to avoid importing HF utilities on non-HF paths
+            from agentlab.llm.huggingface_utils import HuggingFaceURLChatModel
 
             return HuggingFaceURLChatModel(
                 model_name=self.model_name,
@@ -438,28 +438,26 @@ def __init__(
         )
 
 
-class HuggingFaceURLChatModel(HFBaseChatModel):
-    def __init__(
-        self,
-        model_name: str,
-        base_model_name: str,
-        model_url: str,
-        token: Optional[str] = None,
-        temperature: Optional[int] = 1e-1,
-        max_new_tokens: Optional[int] = 512,
-        n_retry_server: Optional[int] = 4,
-        log_probs: Optional[bool] = False,
-    ):
-        super().__init__(model_name, base_model_name, n_retry_server, log_probs)
-        if temperature < 1e-3:
-            logging.warning("Models might behave weirdly when temperature is too low.")
-        self.temperature = temperature
+def __getattr__(name: str):
+    """Lazy re-export of optional classes to keep imports light.
+
+    This lets users import HuggingFaceURLChatModel from agentlab.llm.chat_api
+    without importing heavy dependencies unless actually used.
+
+    Args:
+        name: The name of the attribute to retrieve.
+
+    Returns:
+        The requested class or raises AttributeError if not found.
 
-        if token is None:
-            token = os.environ["TGI_TOKEN"]
+    Raises:
+        AttributeError: If the requested attribute is not available.
+    """
+    if name == "HuggingFaceURLChatModel":
+        from agentlab.llm.huggingface_utils import HuggingFaceURLChatModel
 
-        client = InferenceClient(model=model_url, token=token)
-        self.llm = partial(client.text_generation, max_new_tokens=max_new_tokens, details=log_probs)
+        return HuggingFaceURLChatModel
+    raise AttributeError(name)
 
 
 class VLLMChatModel(ChatModel):

src/agentlab/llm/huggingface_utils.py

@@ -1,9 +1,10 @@
 import logging
+import os
 import time
+from functools import partial
 from typing import Any, List, Optional, Union
 
 from pydantic import Field
-from transformers import AutoTokenizer, GPT2TokenizerFast
 
 from agentlab.llm.base_api import AbstractChatModel
 from agentlab.llm.llm_utils import AIMessage, Discussion
@@ -45,6 +46,14 @@ def __init__(self, model_name, base_model_name, n_retry_server, log_probs):
         self.n_retry_server = n_retry_server
         self.log_probs = log_probs
 
+        # Lazy import to avoid heavy transformers import when unused
+        try:
+            from transformers import AutoTokenizer, GPT2TokenizerFast  # type: ignore
+        except Exception as e:  # pragma: no cover - surfaced only when transformers missing
+            raise ImportError(
+                "The 'transformers' package is required for HuggingFace models. Install it to use HF backends."
+            ) from e
+
         if base_model_name is None:
             self.tokenizer = AutoTokenizer.from_pretrained(model_name)
         else:
@@ -60,7 +69,7 @@ def __call__(
         self,
         messages: list[dict],
         n_samples: int = 1,
-        temperature: float = None,
+        temperature: Optional[float] = None,
     ) -> Union[AIMessage, List[AIMessage]]:
         """
         Generate one or more responses for the given messages.
@@ -85,7 +94,7 @@ def __call__(
             except Exception as e:
                 if "Conversation roles must alternate" in str(e):
                     logging.warning(
-                        f"Failed to apply the chat template. Maybe because it doesn't support the 'system' role. "
+                        "Failed to apply the chat template. Maybe because it doesn't support the 'system' role. "
                         "Retrying with the 'system' role appended to the 'user' role."
                     )
                     messages = _prepend_system_to_first_user(messages)
@@ -100,7 +109,11 @@ def __call__(
             itr = 0
             while True:
                 try:
-                    temperature = temperature if temperature is not None else self.temperature
+                    temperature = (
+                        temperature
+                        if temperature is not None
+                        else getattr(self, "temperature", 0.1)
+                    )
                     answer = self.llm(prompt, temperature=temperature)
                     response = AIMessage(answer)
                     if self.log_probs:
@@ -144,9 +157,52 @@ def _prepend_system_to_first_user(messages, column_remap={}):
         for msg in messages:
             if msg[role_key] == human_key:
                 # Prepend system content to the first user content
-                msg[text_key] = system_content + "\n" + msg[text_key]
+                msg[text_key] = str(system_content) + "\n" + str(msg[text_key])
                 # Remove the original system message
                 del messages[system_index]
                 break  # Ensures that only the first user message is modified
 
     return messages
+
+
+class HuggingFaceURLChatModel(HFBaseChatModel):
+    """HF backend using a Text Generation Inference (TGI) HTTP endpoint.
+
+    This class is placed here to keep all heavy HF imports optional and only
+    loaded when a HF backend is explicitly requested.
+    """
+
+    def __init__(
+        self,
+        model_name: str,
+        model_url: str,
+        base_model_name: Optional[str] = None,
+        token: Optional[str] = None,
+        temperature: Optional[float] = 1e-1,
+        max_new_tokens: Optional[int] = 512,
+        n_retry_server: Optional[int] = 4,
+        log_probs: Optional[bool] = False,
+    ):
+        super().__init__(model_name, base_model_name, n_retry_server, log_probs)
+        if temperature is not None and temperature < 1e-3:
+            logging.warning("Models might behave weirdly when temperature is too low.")
+        self.temperature = temperature
+
+        if token is None:
+            # support both env var names used elsewhere
+            token = os.environ.get("TGI_TOKEN") or os.environ.get("AGENTLAB_MODEL_TOKEN")
+
+        # Lazy import huggingface_hub here to avoid import on non-HF paths
+        try:
+            from huggingface_hub import InferenceClient  # type: ignore
+        except Exception as e:  # pragma: no cover - surfaced only when package missing
+            raise ImportError(
+                "The 'huggingface_hub' package is required for HuggingFace URL backends."
+            ) from e
+
+        client = InferenceClient(model=model_url, token=token)
+        self.llm = partial(
+            client.text_generation,
+            max_new_tokens=max_new_tokens,
+            details=log_probs,
+        )

src/agentlab/llm/llm_utils.py

@@ -18,7 +18,6 @@
 import tiktoken
 import yaml
 from PIL import Image
-from transformers import AutoModel, AutoTokenizer
 
 langchain_community = importlib.util.find_spec("langchain_community")
 if langchain_community is not None:
@@ -512,6 +511,13 @@ def get_tokenizer_old(model_name="openai/gpt-4"):
         )
         return tiktoken.encoding_for_model("gpt-4")
     else:
+        # Lazy import of transformers only when needed
+        try:
+            from transformers import AutoTokenizer  # type: ignore
+        except Exception as e:
+            raise ImportError(
+                "The 'transformers' package is required to use non-OpenAI/Azure tokenizers."
+            ) from e
         return AutoTokenizer.from_pretrained(model_name)
 
 
@@ -522,6 +528,8 @@ def get_tokenizer(model_name="gpt-4"):
     except KeyError:
         logging.info(f"Could not find a tokenizer for model {model_name}. Trying HuggingFace.")
     try:
+        from transformers import AutoTokenizer  # type: ignore
+
         return AutoTokenizer.from_pretrained(model_name)
     except Exception as e:
         logging.info(f"Could not find a tokenizer for model {model_name}: {e} Defaulting to gpt-4.")
@@ -676,8 +684,8 @@ def parse_html_tags(text, keys=(), optional_keys=(), merge_multiple=False):
     retry_messages = []
 
     for key in all_keys:
-        if not key in content_dict:
-            if not key in optional_keys:
+        if key not in content_dict:
+            if key not in optional_keys:
                 retry_messages.append(f"Missing the key <{key}> in the answer.")
         else:
             val = content_dict[key]
@@ -697,6 +705,13 @@ def parse_html_tags(text, keys=(), optional_keys=(), merge_multiple=False):
 
 
 def download_and_save_model(model_name: str, save_dir: str = "."):
+    # Lazy import of transformers only when explicitly downloading a model
+    try:
+        from transformers import AutoModel  # type: ignore
+    except Exception as e:
+        raise ImportError(
+            "The 'transformers' package is required to download and save models."
+        ) from e
     model = AutoModel.from_pretrained(model_name)
     model.save_pretrained(save_dir)
     print(f"Model downloaded and saved to {save_dir}")