Add plugin rerank invocation action

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."""