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fix(mcp): deterministic order for MCP-annotated beans (#4618)
Signed-off-by: Kuntal Maity kuntal.1461@gmail.com Signed-off-by: Kuntal Maity <kuntal.1461@gmail.com>
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‎auto-configurations/mcp/spring-ai-autoconfigure-mcp-client-common/src/main/java/org/springframework/ai/mcp/client/common/autoconfigure/annotations/McpClientSpecificationFactoryAutoConfiguration.java‎

Lines changed: 16 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -57,26 +57,26 @@ static class SyncClientSpecificationConfiguration {
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@Bean
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List<SyncLoggingSpecification> loggingSpecs(ClientMcpAnnotatedBeans beansWithMcpMethodAnnotations) {
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return SyncMcpAnnotationProviders
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.loggingSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpLogging.class));
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return new SupplierBackedList<>(() -> SyncMcpAnnotationProviders
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.loggingSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpLogging.class)));
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}
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@Bean
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List<SyncSamplingSpecification> samplingSpecs(ClientMcpAnnotatedBeans beansWithMcpMethodAnnotations) {
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return SyncMcpAnnotationProviders
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.samplingSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpSampling.class));
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return new SupplierBackedList<>(() -> SyncMcpAnnotationProviders
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.samplingSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpSampling.class)));
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}
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@Bean
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List<SyncElicitationSpecification> elicitationSpecs(ClientMcpAnnotatedBeans beansWithMcpMethodAnnotations) {
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return SyncMcpAnnotationProviders
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.elicitationSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpElicitation.class));
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return new SupplierBackedList<>(() -> SyncMcpAnnotationProviders
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.elicitationSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpElicitation.class)));
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}
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@Bean
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List<SyncProgressSpecification> progressSpecs(ClientMcpAnnotatedBeans beansWithMcpMethodAnnotations) {
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return SyncMcpAnnotationProviders
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.progressSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpProgress.class));
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return new SupplierBackedList<>(() -> SyncMcpAnnotationProviders
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.progressSpecifications(beansWithMcpMethodAnnotations.getBeansByAnnotation(McpProgress.class)));
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}
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}
@@ -87,22 +87,26 @@ static class AsyncClientSpecificationConfiguration {
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@Bean
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List<AsyncLoggingSpecification> loggingSpecs(ClientMcpAnnotatedBeans beanRegistry) {
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return AsyncMcpAnnotationProviders.loggingSpecifications(beanRegistry.getAllAnnotatedBeans());
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return new SupplierBackedList<>(
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() -> AsyncMcpAnnotationProviders.loggingSpecifications(beanRegistry.getAllAnnotatedBeans()));
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}
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@Bean
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List<AsyncSamplingSpecification> samplingSpecs(ClientMcpAnnotatedBeans beanRegistry) {
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return AsyncMcpAnnotationProviders.samplingSpecifications(beanRegistry.getAllAnnotatedBeans());
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return new SupplierBackedList<>(
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() -> AsyncMcpAnnotationProviders.samplingSpecifications(beanRegistry.getAllAnnotatedBeans()));
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}
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@Bean
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List<AsyncElicitationSpecification> elicitationSpecs(ClientMcpAnnotatedBeans beanRegistry) {
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return AsyncMcpAnnotationProviders.elicitationSpecifications(beanRegistry.getAllAnnotatedBeans());
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return new SupplierBackedList<>(
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() -> AsyncMcpAnnotationProviders.elicitationSpecifications(beanRegistry.getAllAnnotatedBeans()));
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}
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@Bean
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List<AsyncProgressSpecification> progressSpecs(ClientMcpAnnotatedBeans beanRegistry) {
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return AsyncMcpAnnotationProviders.progressSpecifications(beanRegistry.getAllAnnotatedBeans());
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return new SupplierBackedList<>(
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() -> AsyncMcpAnnotationProviders.progressSpecifications(beanRegistry.getAllAnnotatedBeans()));
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}
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}

‎auto-configurations/mcp/spring-ai-autoconfigure-mcp-client-common/src/main/java/org/springframework/ai/mcp/client/common/autoconfigure/annotations/SupplierBackedList.java‎

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@@ -0,0 +1,70 @@
1+
/*
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* Copyright 2025-2025 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.ai.mcp.client.common.autoconfigure.annotations;
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import java.util.AbstractList;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Objects;
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import java.util.Spliterator;
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import java.util.Spliterators;
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import java.util.function.Supplier;
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import java.util.stream.Stream;
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import java.util.stream.StreamSupport;
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/**
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* A simple {@link java.util.List} backed by a {@link Supplier} of lists. Each access
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* reads from the supplier, so the contents reflect the supplier's current state.
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*/
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/**
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* @author Kuntal Maity
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*/
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final class SupplierBackedList<T> extends AbstractList<T> {
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private final Supplier<List<T>> supplier;
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SupplierBackedList(Supplier<List<T>> supplier) {
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this.supplier = Objects.requireNonNull(supplier, "supplier must not be null");
42+
}
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@Override
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public T get(int index) {
46+
return this.supplier.get().get(index);
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}
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@Override
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public int size() {
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return this.supplier.get().size();
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}
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@Override
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public Iterator<T> iterator() {
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// Iterate over a snapshot for iteration consistency
57+
return List.copyOf(this.supplier.get()).iterator();
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}
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@Override
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public Spliterator<T> spliterator() {
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return Spliterators.spliterator(iterator(), size(), Spliterator.ORDERED | Spliterator.SIZED);
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}
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@Override
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public Stream<T> stream() {
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return StreamSupport.stream(spliterator(), false);
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}
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}

‎auto-configurations/mcp/spring-ai-autoconfigure-mcp-client-common/src/test/java/org/springframework/ai/mcp/client/common/autoconfigure/annotations/McpClientSpecOrderingReproTests.java‎

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/*
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* Copyright 2025-2025 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.ai.mcp.client.common.autoconfigure.annotations;
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import java.util.List;
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import io.modelcontextprotocol.spec.McpSchema.ProgressNotification;
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import org.junit.jupiter.api.Test;
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import org.springaicommunity.mcp.annotation.McpProgress;
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import org.springaicommunity.mcp.method.progress.SyncProgressSpecification;
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import org.springframework.ai.mcp.client.common.autoconfigure.annotations.McpClientAnnotationScannerAutoConfiguration.ClientMcpAnnotatedBeans;
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import org.springframework.boot.autoconfigure.AutoConfigurations;
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import org.springframework.boot.test.context.runner.ApplicationContextRunner;
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import org.springframework.context.annotation.ComponentScan;
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import org.springframework.context.annotation.Configuration;
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import org.springframework.context.annotation.Lazy;
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import org.springframework.stereotype.Component;
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import static org.assertj.core.api.Assertions.assertThat;
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/**
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* Reproduction test for ordering bug where McpClientSpecificationFactoryAutoConfiguration
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* is created before any @Component beans with @McpProgress (or other MCP annotations) are
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* instantiated, resulting in empty specification lists.
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*/
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class McpClientSpecOrderingReproTests {
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private final ApplicationContextRunner runner = new ApplicationContextRunner()
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.withConfiguration(AutoConfigurations.of(McpClientAnnotationScannerAutoConfiguration.class,
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McpClientSpecificationFactoryAutoConfiguration.class))
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.withUserConfiguration(ScanConfig.class);
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@Configuration
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@ComponentScan(basePackageClasses = ScannedClientHandlers.class)
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static class ScanConfig {
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}
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@Component
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@Lazy
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static class ScannedClientHandlers {
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@McpProgress(clients = "server1")
58+
public void onProgress(ProgressNotification pn) {
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}
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}
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@Test
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void progressSpecsIncludeScannedComponent_evenWhenCreatedAfterSpecsBean() {
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runner.run(ctx -> {
66+
// 1) Trigger spec list bean creation early
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@SuppressWarnings("unchecked")
68+
List<SyncProgressSpecification> specs = (List<SyncProgressSpecification>) ctx.getBean("progressSpecs");
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// 2) Now force creation of the scanned @Component (post-processor runs here)
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ctx.getBean(ScannedClientHandlers.class);
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// 3) Registry sees the component…
74+
ClientMcpAnnotatedBeans registry = ctx.getBean(ClientMcpAnnotatedBeans.class);
75+
assertThat(registry.getBeansByAnnotation(McpProgress.class)).hasSize(1);
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// 4) Expected behavior: specs reflect newly-registered handler
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// Under the bug, this assertion fails (list stays empty)
79+
assertThat(specs).hasSize(1);
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});
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}
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}

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