From 64bdc8699844c6671277c663d98aac16bc0f4042 Mon Sep 17 00:00:00 2001
From: Thushanth Bengre <thushanth-bengre-langchain@users.noreply.github.com>
Date: Thu, 24 Sep 2026 14:18:43 +0000
Subject: [PATCH] feat(typesafe): select SemIf for `TsToolSelectorMiddleware`

Allow a classifier model override while retaining Jev as the default.

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
---
 libs/partners/typesafe/README.md                 |  2 +-
 .../experimental/middleware/tool_selector.py     |  5 +++++
 .../middleware/test_tool_selector.py             | 16 ++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/libs/partners/typesafe/README.md b/libs/partners/typesafe/README.md
index 7f181dff79..caae3daedc 100644
--- a/libs/partners/typesafe/README.md
+++ b/libs/partners/typesafe/README.md
@@ -87,7 +87,7 @@ agent = create_agent(
 )
 ```
 
-The middleware asks one independent `Noul` question per candidate tool ("is this tool needed next?"), batched into a single TypeSafe request against the latest human message, before every model call. Tools whose probability clears `relevance_threshold` (default `0.5`) are kept, ranked by that probability, and capped at `max_tools` if set. Use `always_include` to keep specific tools regardless of classification. This API is experimental and may change without notice.
+The middleware asks one independent `Noul` question per candidate tool ("is this tool needed next?"), batched into a single TypeSafe request against the latest human message, before every model call. Tools whose probability clears `relevance_threshold` (default `0.5`) are kept, ranked by that probability, and capped at `max_tools` if set. Use `always_include` to keep specific tools regardless of classification. To use SemIf instead of the default Jev model, set `classifier_model="semif-qwen3.5-4b"` and configure `TYPESAFE_BASE_URL` and `TYPESAFE_API_KEY` for a gateway that supports SemIf. This API is experimental and may change without notice.
 
 ### LangChain messages as state
 
diff --git a/libs/partners/typesafe/langchain_typesafe/experimental/middleware/tool_selector.py b/libs/partners/typesafe/langchain_typesafe/experimental/middleware/tool_selector.py
index 810d95e293..e56f44515f 100644
--- a/libs/partners/typesafe/langchain_typesafe/experimental/middleware/tool_selector.py
+++ b/libs/partners/typesafe/langchain_typesafe/experimental/middleware/tool_selector.py
@@ -67,6 +67,8 @@ class TsToolSelectorMiddleware(
             are kept. No limit if not specified.
         always_include: Tool names to always include regardless of classification.
             These do not count against `max_tools` and are not sent to TypeSafe.
+        classifier_model: Model used for classification. Set to `semif-qwen3.5-4b`
+            to use SemIf through a compatible gateway; defaults to Jev.
 
     Raises:
         ValueError: If `relevance_threshold` is not between `0` and `1`.
@@ -93,6 +95,7 @@ class TsToolSelectorMiddleware(
         relevance_threshold: float = 0.5,
         max_tools: int | None = None,
         always_include: list[str] | None = None,
+        classifier_model: str = "jev-latest",
     ) -> None:
         """Initialize the tool selector."""
         super().__init__()
@@ -102,6 +105,7 @@ class TsToolSelectorMiddleware(
         self.relevance_threshold = relevance_threshold
         self.max_tools = max_tools
         self.always_include = always_include or []
+        self.classifier_model = classifier_model
 
     def _prepare_selection_request(
         self, request: ModelRequest[ContextT]
@@ -160,6 +164,7 @@ class TsToolSelectorMiddleware(
     def _build_classifier(self, tools: list[BaseTool]) -> TypeSafeClassifier:
         """Build a classifier with one `Noul` question per candidate tool."""
         return TypeSafeClassifier(
+            model=self.classifier_model,
             questions={
                 f"{_TOOL_QUESTION_PREFIX}{tool.name}": Noul(
                     instructions=(
diff --git a/libs/partners/typesafe/tests/unit_tests/experimental/middleware/test_tool_selector.py b/libs/partners/typesafe/tests/unit_tests/experimental/middleware/test_tool_selector.py
index 8b01dcc33c..2e86c07e04 100644
--- a/libs/partners/typesafe/tests/unit_tests/experimental/middleware/test_tool_selector.py
+++ b/libs/partners/typesafe/tests/unit_tests/experimental/middleware/test_tool_selector.py
@@ -92,6 +92,22 @@ def test_middleware_constructs_classifier_per_call() -> None:
     assert "current weather" in questions["tool::get_weather"].instructions
 
 
+@pytest.mark.parametrize("model", ["jev-latest", "semif-qwen3.5-4b"])
+def test_classifier_uses_requested_model(model: str) -> None:
+    """Route tool classification to the configured model without changing selection."""
+    classifier = _classifier(_response({"get_weather": 0.9}))
+    request = _request([get_weather], [HumanMessage("What's the weather?")])
+    middleware = TsToolSelectorMiddleware(classifier_model=model)
+
+    with patch(
+        "langchain_typesafe.experimental.middleware.tool_selector.TypeSafeClassifier",
+        return_value=classifier,
+    ) as classifier_class:
+        middleware.wrap_model_call(request, lambda _req: MagicMock())
+
+    assert classifier_class.call_args.kwargs["model"] == model
+
+
 def test_sync_selection_filters_tools_above_threshold() -> None:
     """Keep only tools whose `Noul` probability clears the threshold."""
     classifier = _classifier(