Add plugin rerank invocation action

Bumps the pinned langbot-plugin SDK from 0.4.4 to 0.4.5, which adds
`provider_specific_fields` to the Message/ToolCall entities. This is the
SDK dependency required by the Gemini thought_signature fix (#1899, #2265).

The lock update is scoped to langbot-plugin only. pylibseekdb is deliberately
held at 1.1.0: a free re-resolve drifts it to 1.3.0 (pyseekdb==1.1.0.post3
has no upper bound on it), which is out of scope here and should be handled
in a separate dependency-upgrade PR.

pyproject.toml

@@ -70,7 +70,7 @@ dependencies = [
     "chromadb>=1.0.0,<2.0.0",
     "qdrant-client (>=1.15.1,<2.0.0)",
     "pyseekdb==1.1.0.post3",
-    "langbot-plugin==0.4.4",
+    "langbot-plugin==0.4.5",
     "asyncpg>=0.30.0",
     "line-bot-sdk>=3.19.0",
     "matrix-nio>=0.25.2",

src/langbot/pkg/plugin/handler.py

@@ -514,6 +514,35 @@ class RuntimeConnectionHandler(handler.Handler):
             except Exception as e:
                 return _make_rag_error_response(e, 'EmbeddingError', embedding_model_uuid=embedding_model_uuid)
 
+        @self.action(PluginToRuntimeAction.INVOKE_RERANK)
+        async def invoke_rerank(data: dict[str, Any]) -> handler.ActionResponse:
+            rerank_model_uuid = data['rerank_model_uuid']
+            query = data['query']
+            documents = data['documents']
+            top_k = data.get('top_k')
+            extra_args = data.get('extra_args', {})
+
+            try:
+                rerank_model = await self.ap.model_mgr.get_rerank_model_by_uuid(rerank_model_uuid)
+            except ValueError:
+                return handler.ActionResponse.error(
+                    message=f'Rerank model with rerank_model_uuid {rerank_model_uuid} not found',
+                )
+
+            try:
+                scores = await rerank_model.provider.invoke_rerank(
+                    model=rerank_model,
+                    query=query,
+                    documents=documents[:64],
+                    extra_args=extra_args,
+                )
+                scored = sorted(scores, key=lambda x: x.get('relevance_score', 0), reverse=True)
+                if top_k is not None:
+                    scored = scored[: int(top_k)]
+                return handler.ActionResponse.success(data={'results': scored})
+            except Exception as e:
+                return _make_rag_error_response(e, 'RerankError', rerank_model_uuid=rerank_model_uuid)
+
         @self.action(PluginToRuntimeAction.VECTOR_UPSERT)
         async def vector_upsert(data: dict[str, Any]) -> handler.ActionResponse:
             collection_id = data['collection_id']

tests/unit_tests/plugin/test_handler_actions.py

@@ -27,6 +27,66 @@ def compiled_params(statement):
     return statement.compile().params
 
 
+class TestRagRerankAction:
+    """Tests for RAG rerank action handler."""
+
+    @pytest.fixture
+    def app(self):
+        mock_app = Mock()
+        mock_app.model_mgr = Mock()
+        mock_app.logger = Mock()
+        return mock_app
+
+    @pytest.mark.asyncio
+    async def test_invokes_rerank_model_and_sorts_scores(self, app):
+        """Rerank action uses the selected model and returns top scores."""
+        provider = Mock()
+        provider.invoke_rerank = AsyncMock(
+            return_value=[
+                {'index': 0, 'relevance_score': 0.2},
+                {'index': 1, 'relevance_score': 0.9},
+            ]
+        )
+        rerank_model = SimpleNamespace(provider=provider)
+        app.model_mgr.get_rerank_model_by_uuid = AsyncMock(return_value=rerank_model)
+        runtime_handler = make_handler(app)
+
+        response = await runtime_handler.actions[PluginToRuntimeAction.INVOKE_RERANK.value]({
+            'rerank_model_uuid': 'rerank-1',
+            'query': 'hello',
+            'documents': ['a', 'b'],
+            'top_k': 1,
+            'extra_args': {'return_documents': False},
+        })
+
+        assert response.code == 0
+        assert response.data['results'] == [{'index': 1, 'relevance_score': 0.9}]
+        app.model_mgr.get_rerank_model_by_uuid.assert_awaited_once_with('rerank-1')
+        provider.invoke_rerank.assert_awaited_once_with(
+            model=rerank_model,
+            query='hello',
+            documents=['a', 'b'],
+            extra_args={'return_documents': False},
+        )
+
+    @pytest.mark.asyncio
+    async def test_returns_error_when_rerank_model_missing(self, app):
+        """Missing rerank model returns an action error."""
+        app.model_mgr.get_rerank_model_by_uuid = AsyncMock(
+            side_effect=ValueError('not found')
+        )
+        runtime_handler = make_handler(app)
+
+        response = await runtime_handler.actions[PluginToRuntimeAction.INVOKE_RERANK.value]({
+            'rerank_model_uuid': 'missing',
+            'query': 'hello',
+            'documents': ['a'],
+        })
+
+        assert response.code != 0
+        assert 'Rerank model with rerank_model_uuid missing not found' in response.message
+
+
 class TestInitializePluginSettings:
     """Tests for initialize_plugin_settings action handler."""
 

uv.lock

@@ -2082,7 +2082,7 @@ requires-dist = [
     { name = "ebooklib", specifier = ">=0.18" },
     { name = "gewechat-client", specifier = ">=0.1.5" },
     { name = "html2text", specifier = ">=2024.2.26" },
-    { name = "langbot-plugin", specifier = "==0.4.4" },
+    { name = "langbot-plugin", specifier = "==0.4.5" },
     { name = "langchain", specifier = ">=0.2.0" },
     { name = "langchain-core", specifier = ">=1.3.3" },
     { name = "langchain-text-splitters", specifier = ">=1.1.2" },
@@ -2146,7 +2146,7 @@ dev = [
 
 [[package]]
 name = "langbot-plugin"
-version = "0.4.4"
+version = "0.4.5"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "aiofiles" },
@@ -2167,9 +2167,9 @@ dependencies = [
     { name = "watchdog" },
     { name = "websockets" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/68/1a/636c057f6e07a0c87dc7b9c1a373d73df82787b7706ba3ba1a95f633ce7c/langbot_plugin-0.4.4.tar.gz", hash = "sha256:8fdad2d22fe8360d2911557fac17f258f57e85f1a36bd50cd488cb44f61225a4", size = 312741, upload-time = "2026-06-13T11:59:36.772Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/f3/db/db33ec42b3242ea7de0c93b0523a8d32a3df76b13de177fd31671db0ba3f/langbot_plugin-0.4.5.tar.gz", hash = "sha256:3cafa5694f31e9e4b4a3d870c1bc23ee7ac6e8d271a0140c5198993471f220ec", size = 326504, upload-time = "2026-06-19T14:53:51.687Z" }
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+    { url = "https://files.pythonhosted.org/packages/81/92/8a08f8793de479fffa12a1906a25b6ff5b67a018520fa72d981569e1a6e4/langbot_plugin-0.4.5-py3-none-any.whl", hash = "sha256:12ab9aff0fb2459f75a11ba6999d2b5dfc753dcc7d265b078777b24e04b23c83", size = 215602, upload-time = "2026-06-19T14:53:50.021Z" },
 ]
 
 [[package]]