diff --git a/README.md b/README.md
index f8a0b572..24ffb339 100644
--- a/README.md
+++ b/README.md
@@ -145,6 +145,8 @@ When the option `cache-dependency-path` is specified, the hash is based on the m
 
 The workflow output `cache-hit` is set to indicate if an exact match was found for the key [as actions/cache does](https://github.com/actions/cache/tree/main#outputs).
 
+The workflow output `cache-primary-key` exposes the primary cache key computed by the action for the configured build tool. It is useful for composing with [`actions/cache`](https://github.com/actions/cache) or [`actions/cache/restore`](https://github.com/actions/cache/tree/main/restore) in later steps or dependent jobs that need to reuse the exact same key. It is empty when caching is not enabled or when caching is skipped (for example, when the cache service is unavailable).
+
 The cache input is optional, and caching is turned off by default.
 
 **Maven Wrapper:** when `cache: 'maven'` is enabled, the action also caches and restores the Maven Wrapper distribution downloaded to `~/.m2/wrapper/dists` (in addition to the local repository), so wrapper-based (`./mvnw`) builds don't re-download the wrapper on every run. This is keyed on `**/.mvn/wrapper/maven-wrapper.properties` as shown above.
diff --git a/__tests__/cache.test.ts b/__tests__/cache.test.ts
index 69056870..90f68efe 100644
--- a/__tests__/cache.test.ts
+++ b/__tests__/cache.test.ts
@@ -78,6 +78,10 @@ describe('dependency cache', () => {
       ReturnType<typeof glob.hashFiles>,
       Parameters<typeof glob.hashFiles>
     >;
+    let spySetOutput: jest.SpyInstance<
+      ReturnType<typeof core.setOutput>,
+      Parameters<typeof core.setOutput>
+    >;
 
     beforeEach(() => {
       spyCacheRestore = jest
@@ -86,6 +90,7 @@ describe('dependency cache', () => {
           Promise.resolve(undefined)
         );
       spyGlobHashFiles = jest.spyOn(glob, 'hashFiles');
+      spySetOutput = jest.spyOn(core, 'setOutput').mockImplementation(() => {});
       spyWarning.mockImplementation(() => null);
     });
 
@@ -120,6 +125,15 @@ describe('dependency cache', () => {
         expect(spyWarning).not.toHaveBeenCalled();
         expect(spyInfo).toHaveBeenCalledWith('maven cache is not found');
       });
+      it('sets the cache-primary-key output', async () => {
+        createFile(join(workspace, 'pom.xml'));
+
+        await restore('maven', '');
+        expect(spySetOutput).toHaveBeenCalledWith(
+          'cache-primary-key',
+          expect.stringContaining('setup-java-')
+        );
+      });
       it('downloads cache based on maven-wrapper.properties', async () => {
         createDirectory(join(workspace, '.mvn'));
         createDirectory(join(workspace, '.mvn', 'wrapper'));
diff --git a/action.yml b/action.yml
index 781c8245..5237f1a8 100644
--- a/action.yml
+++ b/action.yml
@@ -103,6 +103,8 @@ outputs:
     description: 'Path to where the java environment has been installed (same as $JAVA_HOME)'
   cache-hit:
     description: 'A boolean value to indicate an exact match was found for the primary key'
+  cache-primary-key:
+    description: 'The primary cache key computed by the action for the configured build tool. Empty when caching is not enabled or when caching is skipped (e.g. cache service unavailable). Useful for composing with actions/cache or actions/cache/restore across jobs.'
 runs:
   using: 'node24'
   main: 'dist/setup/index.js'
diff --git a/dist/cleanup/index.js b/dist/cleanup/index.js
index 01fb8505..1154a0bc 100644
--- a/dist/cleanup/index.js
+++ b/dist/cleanup/index.js
@@ -52056,6 +52056,7 @@ function restore(id, cacheDependencyPath) {
         const primaryKey = yield computeCacheKey(packageManager, cacheDependencyPath);
         core.debug(`primary key is ${primaryKey}`);
         core.saveState(STATE_CACHE_PRIMARY_KEY, primaryKey);
+        core.setOutput(STATE_CACHE_PRIMARY_KEY, primaryKey);
         // No "restoreKeys" is set, to start with a clear cache after dependency update (see https://github.com/actions/setup-java/issues/269)
         const matchedKey = yield cache.restoreCache(packageManager.path, primaryKey);
         if (matchedKey) {
diff --git a/dist/setup/index.js b/dist/setup/index.js
index 30395de2..7b098a52 100644
--- a/dist/setup/index.js
+++ b/dist/setup/index.js
@@ -77921,6 +77921,7 @@ function restore(id, cacheDependencyPath) {
         const primaryKey = yield computeCacheKey(packageManager, cacheDependencyPath);
         core.debug(`primary key is ${primaryKey}`);
         core.saveState(STATE_CACHE_PRIMARY_KEY, primaryKey);
+        core.setOutput(STATE_CACHE_PRIMARY_KEY, primaryKey);
         // No "restoreKeys" is set, to start with a clear cache after dependency update (see https://github.com/actions/setup-java/issues/269)
         const matchedKey = yield cache.restoreCache(packageManager.path, primaryKey);
         if (matchedKey) {
diff --git a/src/cache.ts b/src/cache.ts
index 42c086c1..263cc0d8 100644
--- a/src/cache.ts
+++ b/src/cache.ts
@@ -118,6 +118,7 @@ export async function restore(id: string, cacheDependencyPath: string) {
   const primaryKey = await computeCacheKey(packageManager, cacheDependencyPath);
   core.debug(`primary key is ${primaryKey}`);
   core.saveState(STATE_CACHE_PRIMARY_KEY, primaryKey);
+  core.setOutput(STATE_CACHE_PRIMARY_KEY, primaryKey);
 
   // No "restoreKeys" is set, to start with a clear cache after dependency update (see https://github.com/actions/setup-java/issues/269)
   const matchedKey = await cache.restoreCache(packageManager.path, primaryKey);