diff --git a/src/stagehand/_client.py b/src/stagehand/_client.py
index 3997b5e..f631485 100644
--- a/src/stagehand/_client.py
+++ b/src/stagehand/_client.py
@@ -60,6 +60,7 @@ def __init__(
         browserbase_api_key: str | None = None,
         browserbase_project_id: str | None = None,
         model_api_key: str | None = None,
+        model_base_url: str | None = None,
         server: Literal["remote", "local"] = "remote",
         _local_stagehand_binary_path: str | os.PathLike[str] | None = None,
         local_host: str = "127.0.0.1",
@@ -121,6 +122,10 @@ def __init__(
             )
         self.model_api_key = model_api_key
 
+        if model_base_url is None:
+            model_base_url = os.environ.get("MODEL_BASE_URL")
+        self.model_base_url = model_base_url
+
         self._sea_server: SeaServerManager | None = None
         if server == "local":
             # We'll switch `base_url` to the started server before the first request.
@@ -195,7 +200,7 @@ def qs(self) -> Querystring:
     @property
     @override
     def auth_headers(self) -> dict[str, str]:
-        return {**self._bb_api_key_auth, **self._bb_project_id_auth, **self._llm_model_api_key_auth}
+        return {**self._bb_api_key_auth, **self._bb_project_id_auth, **self._llm_model_api_key_auth, **self._llm_model_base_url_header}
 
     @property
     def _bb_api_key_auth(self) -> dict[str, str]:
@@ -212,6 +217,11 @@ def _llm_model_api_key_auth(self) -> dict[str, str]:
         model_api_key = self.model_api_key
         return {"x-model-api-key": model_api_key}
 
+    @property
+    def _llm_model_base_url_header(self) -> dict[str, str]:
+        model_base_url = self.model_base_url
+        return {"x-model-base-url": model_base_url} if model_base_url else {}
+
     @property
     @override
     def default_headers(self) -> dict[str, str | Omit]:
@@ -229,6 +239,7 @@ def copy(
         browserbase_api_key: str | None = None,
         browserbase_project_id: str | None = None,
         model_api_key: str | None = None,
+        model_base_url: str | None = None,
         server: Literal["remote", "local"] | None = None,
         _local_stagehand_binary_path: str | os.PathLike[str] | None = None,
         local_host: str | None = None,
@@ -274,6 +285,7 @@ def copy(
             browserbase_api_key=browserbase_api_key or self.browserbase_api_key,
             browserbase_project_id=browserbase_project_id or self.browserbase_project_id,
             model_api_key=model_api_key or self.model_api_key,
+            model_base_url=model_base_url or self.model_base_url,
             server=server or self._server_mode,
             _local_stagehand_binary_path=_local_stagehand_binary_path if _local_stagehand_binary_path is not None else self._local_stagehand_binary_path,
             local_host=local_host or self._local_host,
@@ -348,6 +360,7 @@ def __init__(
         browserbase_api_key: str | None = None,
         browserbase_project_id: str | None = None,
         model_api_key: str | None = None,
+        model_base_url: str | None = None,
         server: Literal["remote", "local"] = "remote",
         _local_stagehand_binary_path: str | os.PathLike[str] | None = None,
         local_host: str = "127.0.0.1",
@@ -409,6 +422,10 @@ def __init__(
             )
         self.model_api_key = model_api_key
 
+        if model_base_url is None:
+            model_base_url = os.environ.get("MODEL_BASE_URL")
+        self.model_base_url = model_base_url
+
         self._sea_server: SeaServerManager | None = None
         if server == "local":
             if base_url is None:
@@ -482,7 +499,7 @@ def qs(self) -> Querystring:
     @property
     @override
     def auth_headers(self) -> dict[str, str]:
-        return {**self._bb_api_key_auth, **self._bb_project_id_auth, **self._llm_model_api_key_auth}
+        return {**self._bb_api_key_auth, **self._bb_project_id_auth, **self._llm_model_api_key_auth, **self._llm_model_base_url_header}
 
     @property
     def _bb_api_key_auth(self) -> dict[str, str]:
@@ -499,6 +516,11 @@ def _llm_model_api_key_auth(self) -> dict[str, str]:
         model_api_key = self.model_api_key
         return {"x-model-api-key": model_api_key}
 
+    @property
+    def _llm_model_base_url_header(self) -> dict[str, str]:
+        model_base_url = self.model_base_url
+        return {"x-model-base-url": model_base_url} if model_base_url else {}
+
     @property
     @override
     def default_headers(self) -> dict[str, str | Omit]:
@@ -516,6 +538,7 @@ def copy(
         browserbase_api_key: str | None = None,
         browserbase_project_id: str | None = None,
         model_api_key: str | None = None,
+        model_base_url: str | None = None,
         server: Literal["remote", "local"] | None = None,
         _local_stagehand_binary_path: str | os.PathLike[str] | None = None,
         local_host: str | None = None,
@@ -561,6 +584,7 @@ def copy(
             browserbase_api_key=browserbase_api_key or self.browserbase_api_key,
             browserbase_project_id=browserbase_project_id or self.browserbase_project_id,
             model_api_key=model_api_key or self.model_api_key,
+            model_base_url=model_base_url or self.model_base_url,
             server=server or self._server_mode,
             _local_stagehand_binary_path=_local_stagehand_binary_path if _local_stagehand_binary_path is not None else self._local_stagehand_binary_path,
             local_host=local_host or self._local_host,