feat(java): JDK 25 default virtual-thread executor via multi-release JAR

.github/workflows/java-publish-maven.yml

@@ -54,10 +54,10 @@ jobs:
 
       - uses: ./.github/actions/setup-copilot
 
-      - name: Set up JDK 17
+      - name: Set up JDK 25
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
-          java-version: "17"
+          java-version: "25"
           distribution: "microsoft"
           cache: "maven"
           server-id: central

.github/workflows/java-publish-snapshot.yml

@@ -30,10 +30,10 @@ jobs:
 
       - uses: ./.github/actions/setup-copilot
 
-      - name: Set up JDK 17
+      - name: Set up JDK 25
         uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
-          java-version: "17"
+          java-version: "25"
           distribution: "microsoft"
           cache: "maven"
           server-id: central

.github/workflows/java-sdk-tests.yml

@@ -37,10 +37,20 @@ permissions:
 
 jobs:
   java-sdk:
-    name: "Java SDK Tests"
+    name: "Java SDK Tests (JDK ${{ matrix.java-version }})"
     if: github.event.repository.fork == false
 
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # JDK 17 is the baseline --release target; JDK 25 also activates the
+        # java25-multi-release Maven profile, producing the MR-JAR overlay
+        # (META-INF/versions/25/) and exercising the virtual-thread default
+        # executor branch end-to-end via InternalExecutorProviderIT. The
+        # build-time verify-java25-overlay antrun guard fires only when the
+        # profile is active, so it is also exercised on the JDK 25 entry.
+        java-version: ["17", "25"]
     defaults:
       run:
         shell: bash
@@ -52,7 +62,7 @@ jobs:
 
       - uses: actions/setup-java@be666c2fcd27ec809703dec50e508c2fdc7f6654 # v5
         with:
-          java-version: "17"
+          java-version: ${{ matrix.java-version }}
           distribution: "microsoft"
           cache: "maven"
 
@@ -86,8 +96,12 @@ jobs:
           COPILOT_CLI_PATH: ${{ steps.setup-copilot.outputs.cli-path }}
         run: mvn verify
 
+      # Side-effects below (site artifact, JaCoCo badge, badge PR) are scoped
+      # to the JDK 17 matrix entry so the badge source-of-truth and the
+      # uploaded site artifact remain a single, stable baseline regardless
+      # of the second matrix entry's outcome.
       - name: Upload test results for site generation
-        if: success() && github.ref == 'refs/heads/main'
+        if: success() && github.ref == 'refs/heads/main' && matrix.java-version == '17'
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         with:
           name: test-results-for-site
@@ -98,12 +112,12 @@ jobs:
           retention-days: 1
 
       - name: Generate JaCoCo badge
-        if: success() && github.ref == 'refs/heads/main'
+        if: success() && github.ref == 'refs/heads/main' && matrix.java-version == '17'
         working-directory: .
         run: .github/scripts/generate-java-coverage-badge.sh java/target/site/jacoco-coverage/jacoco.csv .github/badges
 
       - name: Create PR for JaCoCo badge update
-        if: success() && github.ref == 'refs/heads/main'
+        if: success() && github.ref == 'refs/heads/main' && matrix.java-version == '17'
         uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v7
         with:
           commit-message: "Update Java JaCoCo coverage badge"
@@ -121,7 +135,7 @@ jobs:
         if: failure()
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         with:
-          name: java-test-results
+          name: java-test-results-jdk${{ matrix.java-version }}
           path: |
             java/target/surefire-reports/
             java/target/surefire-reports-isolated/

java/README.md

@@ -21,7 +21,7 @@ Java SDK for programmatic control of GitHub Copilot CLI, enabling you to build A
 
 ### Requirements
 
-- Java 17 or later. **JDK 25 recommended**. Selecting JDK 25 enables the use of virtual threads, as shown in the [Quick Start](#quick-start).
+- Java 17 or later. **JDK 25 recommended**. On JDK 25 and later, the SDK automatically uses virtual threads for its default internal executor.
 - GitHub Copilot CLI 1.0.17 or later installed and in `PATH` (or provide custom `cliPath`)
 
 ### Maven
@@ -66,23 +66,16 @@ implementation 'com.github:copilot-sdk-java:1.0.0-beta-java.4'
 import com.github.copilot.CopilotClient;
 import com.github.copilot.generated.AssistantMessageEvent;
 import com.github.copilot.generated.SessionUsageInfoEvent;
-import com.github.copilot.rpc.CopilotClientOptions;
 import com.github.copilot.rpc.MessageOptions;
 import com.github.copilot.rpc.PermissionHandler;
 import com.github.copilot.rpc.SessionConfig;
 
-import java.util.concurrent.Executors;
-
 public class CopilotSDK {
     public static void main(String[] args) throws Exception {
         var lastMessage = new String[]{null};
 
         // Create and start client
-        try (var client = new CopilotClient()) {  // JDK 25+: comment out this line
-        // JDK 25+: uncomment the following 3 lines for virtual thread support
-        // var options = new CopilotClientOptions()
-        //     .setExecutor(Executors.newVirtualThreadPerTaskExecutor());
-        // try (var client = new CopilotClient(options)) {
+        try (var client = new CopilotClient()) {
             client.start().get();
 
             // Create a session

java/pom.xml

@@ -307,6 +307,33 @@
                     </execution>
                 </executions>
             </plugin>
+            <!--
+                Failsafe runs integration tests against the actually packaged
+                JAR (after the package phase). Used to validate multi-release
+                JAR behaviour end-to-end without reflecting on private fields
+                or hand-rolling a synthetic JAR. See
+                src/test/java/com/github/copilot/InternalExecutorProviderIT.java.
+            -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-failsafe-plugin</artifactId>
+                <version>3.5.5</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>integration-test</goal>
+                            <goal>verify</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <systemPropertyVariables>
+                        <project.build.directory>${project.build.directory}</project.build.directory>
+                        <project.build.finalName>${project.build.finalName}</project.build.finalName>
+                        <project.build.testOutputDirectory>${project.build.testOutputDirectory}</project.build.testOutputDirectory>
+                    </systemPropertyVariables>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
@@ -447,6 +474,10 @@
                         <configuration>
                             <dataFile>${project.build.directory}/jacoco-test-results/sdk-tests.exec</dataFile>
                             <outputDirectory>${project.reporting.outputDirectory}/jacoco-coverage</outputDirectory>
+                            <excludes>
+                                <!-- Exclude multi-release classes to avoid duplicate class analysis. -->
+                                <exclude>META-INF/versions/**/*.class</exclude>
+                            </excludes>
                         </configuration>
                     </execution>
                 </executions>
@@ -507,6 +538,88 @@
                 <surefire.jvm.args>-XX:+EnableDynamicAgentLoading</surefire.jvm.args>
             </properties>
         </profile>
+        <profile>
+            <id>java25-multi-release</id>
+            <activation>
+                <jdk>[25,)</jdk>
+            </activation>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-compiler-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>compile-java25</id>
+                                <phase>compile</phase>
+                                <goals>
+                                    <goal>compile</goal>
+                                </goals>
+                                <configuration>
+                                    <release>25</release>
+                                    <useIncrementalCompilation>false</useIncrementalCompilation>
+                                    <compileSourceRoots>
+                                        <compileSourceRoot>${project.basedir}/src/main/java25</compileSourceRoot>
+                                    </compileSourceRoots>
+                                    <multiReleaseOutput>true</multiReleaseOutput>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-jar-plugin</artifactId>
+                        <configuration>
+                            <archive>
+                                <manifestEntries>
+                                    <Multi-Release>true</Multi-Release>
+                                </manifestEntries>
+                            </archive>
+                        </configuration>
+                    </plugin>
+                    <!--
+                        Structural guard: when this profile is active (JDK 25+
+                        builds), assert that the packaged JAR contains the
+                        JDK 25 multi-release overlay class. Catches accidental
+                        profile-disable / classifier / shading regressions
+                        before the failsafe IT runs.
+                    -->
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-antrun-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>verify-java25-overlay</id>
+                                <phase>package</phase>
+                                <goals>
+                                    <goal>run</goal>
+                                </goals>
+                                <configuration>
+                                    <target>
+                                        <condition property="java25.overlay.present">
+                                            <resourceexists>
+                                                <zipentry zipfile="${project.build.directory}/${project.build.finalName}.jar"
+                                                          name="META-INF/versions/25/com/github/copilot/InternalExecutorProvider.class"/>
+                                            </resourceexists>
+                                        </condition>
+                                        <fail unless="java25.overlay.present">
+JDK 25 multi-release overlay class is missing from the packaged JAR.
+Expected entry: META-INF/versions/25/com/github/copilot/InternalExecutorProvider.class
+JAR: ${project.build.directory}/${project.build.finalName}.jar
+
+This usually means the 'java25-multi-release' Maven profile did not activate
+(e.g. the build is running on a JDK older than 25) or maven-compiler-plugin
+did not produce the multi-release output. Re-build on JDK 25+ and verify the
+'compile-java25' execution ran during the 'compile' phase.
+                                        </fail>
+                                    </target>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
         <!-- Skip git-clone + npm install of the copilot-sdk test harness -->
         <profile>
             <id>skip-test-harness</id>