diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1815c4150..1beb26a55 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -201,6 +201,8 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 #### Symbols, tests and the viewer
 
+- Java packages named `build` under standard main and test source roots are now indexed without pulling Gradle or Maven build output into the graph. (#1642)
+
 - **Files under an `e2e/` directory count as tests.** Their calls no longer appear as production callers in Steps, dead-code and test badges.
 
 - **Production code under a `samples` or `examples` package path is no longer treated as test code.** A Kotlin or Java project whose package path runs through `com/google/samples/…` (Now in Android, for one) had nearly every file counted as a fixture, so the Map opened on `build-logic`, the entry points hid the app, and dead-code and test badges were wrong. Only the project layout above a `src/` folder decides now; the package path below it never does.
diff --git a/__tests__/extraction.test.ts b/__tests__/extraction.test.ts
index ad0ba2374..991309c27 100644
--- a/__tests__/extraction.test.ts
+++ b/__tests__/extraction.test.ts
@@ -7637,6 +7637,39 @@ describe('Nested non-submodule git repos', () => {
     expect(ig.ignores('dist/')).toBe(true); // valid rule survives
     expect(ig.ignores('src/app.ts')).toBe(false);
   });
+
+  it('keeps Java packages named build while excluding build output (#1642)', () => {
+    const sourceFile = 'module/src/main/java/com/acme/build/RealtimePlusService.java';
+    const testFile = 'module/src/test/java/com/acme/build/RealtimePlusServiceTest.java';
+    const outputFile = 'module/build/generated/Generated.java';
+
+    for (const rel of [sourceFile, testFile, outputFile]) {
+      const abs = path.join(tempDir, rel);
+      fs.mkdirSync(path.dirname(abs), { recursive: true });
+      fs.writeFileSync(abs, 'class Example {}\n');
+    }
+
+    const scope = buildScopeIgnore(tempDir);
+    expect(scope.ignores(sourceFile)).toBe(false);
+    expect(scope.ignores(testFile)).toBe(false);
+    expect(scope.ignores(outputFile)).toBe(true);
+
+    const files = scanDirectory(tempDir);
+    expect(files).toContain(sourceFile);
+    expect(files).toContain(testFile);
+    expect(files).not.toContain(outputFile);
+  });
+
+  it('lets an explicit .gitignore exclude a Java package named build (#1642)', () => {
+    const sourceFile = 'src/main/java/com/acme/build/Hidden.java';
+    const abs = path.join(tempDir, sourceFile);
+    fs.mkdirSync(path.dirname(abs), { recursive: true });
+    fs.writeFileSync(abs, 'class Hidden {}\n');
+    fs.writeFileSync(path.join(tempDir, '.gitignore'), 'src/main/java/**/build/\n');
+
+    expect(buildScopeIgnore(tempDir).ignores(sourceFile)).toBe(true);
+    expect(scanDirectory(tempDir)).not.toContain(sourceFile);
+  });
 });
 
 // =============================================================================
diff --git a/src/extraction/index.ts b/src/extraction/index.ts
index 93be48352..a62381414 100644
--- a/src/extraction/index.ts
+++ b/src/extraction/index.ts
@@ -227,6 +227,12 @@ const DEFAULT_IGNORE_PATTERNS: string[] = [
   'bazel-*/',        // Bazel output symlink trees
   // Android resource dirs at any depth, with their qualifier variants (#1047).
   ...ANDROID_RES_TYPES.map((t) => `**/res/${t}*/`),
+  // `build` is also a legal Java package segment. Keep it under conventional
+  // Java source roots while continuing to exclude module/build output (#1642).
+  '!**/src/main/java/**/build/',
+  '!**/src/main/java/**/build/**',
+  '!**/src/test/java/**/build/',
+  '!**/src/test/java/**/build/**',
 ];
 
 /** True if `buf` decodes as strict UTF-8 (no invalid byte sequences). */