chore: Integrate xAI as provider (#773)

# Motivation

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# Content

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# Testing

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# Please check the following before marking your PR as ready for review

- [x] I have added tests for my changes
- [x] I have updated the documentation or added new documentation as
needed

---------

Co-authored-by: kopekC <28070492+kopekC@users.noreply.github.com>

Author: kopekC

pyproject.toml

@@ -78,6 +78,7 @@ dependencies = [
   "datasets",
   "colorlog>=6.9.0",
   "langsmith",
+  "langchain-xai>=0.2.1",
 ]
 
 license = { text = "Apache-2.0" }

src/codegen/extensions/langchain/llm.py

@@ -13,6 +13,7 @@
 from langchain_core.runnables import Runnable
 from langchain_core.tools import BaseTool
 from langchain_openai import ChatOpenAI
+from langchain_xai import ChatXAI
 from pydantic import Field
 
 
@@ -76,6 +77,9 @@ def _get_model_kwargs(self) -> dict[str, Any]:
 
         if self.model_provider == "anthropic":
             return {**base_kwargs, "model": self.model_name}
+        elif self.model_provider == "xai":
+            xai_api_base = os.getenv("XAI_API_BASE", "https://api.x.ai/v1/")
+            return {**base_kwargs, "model": self.model_name, "xai_api_base": xai_api_base}
         else:  # openai
             return {**base_kwargs, "model": self.model_name}
 
@@ -93,7 +97,13 @@ def _get_model(self) -> BaseChatModel:
                 raise ValueError(msg)
             return ChatOpenAI(**self._get_model_kwargs())
 
-        msg = f"Unknown model provider: {self.model_provider}. Must be one of: anthropic, openai"
+        elif self.model_provider == "xai":
+            if not os.getenv("XAI_API_KEY"):
+                msg = "XAI_API_KEY not found in environment. Please set it in your .env file or environment variables."
+                raise ValueError(msg)
+            return ChatXAI(**self._get_model_kwargs())
+
+        msg = f"Unknown model provider: {self.model_provider}. Must be one of: anthropic, openai, xai"
         raise ValueError(msg)
 
     def _generate(