Chore(ci): cancel superseded pull request CI runs via concurrency groups

.github/workflows/cross-language-integration.yml

@@ -6,6 +6,11 @@ on:
   pull_request:
     branches: [main]
 
+# Cancel superseded PR runs; the run_id fallback keeps push-to-main runs ungrouped.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   run-tests:
     runs-on: macos-latest

.github/workflows/license-check.yml

@@ -6,6 +6,11 @@ on:
   pull_request:
     branches: [main]
 
+# Cancel superseded PR runs; the run_id fallback keeps push-to-main runs ungrouped.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   check-license:
     runs-on: ubuntu-latest

.github/workflows/validation.yaml

@@ -6,6 +6,11 @@ on:
   pull_request:
     branches: [main]
 
+# Cancel superseded PR runs; the run_id fallback keeps push-to-main runs ungrouped.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 env:
   NODE_OPTIONS: "--max-old-space-size=8192"
 

tests/integration/workflows/workflow_concurrency_test.ts

@@ -0,0 +1,91 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import yaml from 'js-yaml';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import {describe, expect, it} from 'vitest';
+
+const WORKFLOWS_DIR = path.join(process.cwd(), '.github/workflows');
+
+/** Activity types GitHub uses when a `pull_request` trigger omits `types`. */
+const DEFAULT_PULL_REQUEST_TYPES = ['opened', 'synchronize', 'reopened'];
+
+/** The subset of a workflow file this test inspects. */
+interface Workflow {
+  on?: {pull_request?: {types?: string[]} | null};
+  concurrency?: {group?: string; 'cancel-in-progress'?: boolean};
+}
+
+function isWorkflow(value: unknown): value is Workflow {
+  return typeof value === 'object' && value !== null;
+}
+
+function loadWorkflow(file: string): Workflow {
+  const source = fs.readFileSync(path.join(WORKFLOWS_DIR, file), 'utf8');
+  const parsed: unknown = yaml.load(source);
+  return isWorkflow(parsed) ? parsed : {};
+}
+
+/**
+ * A workflow can be superseded only if a later push to the same pull request
+ * re-triggers it, i.e. if its `pull_request` activity types include
+ * `synchronize`.
+ */
+function isSupersedable(workflow: Workflow): boolean {
+  const pullRequest = workflow.on?.pull_request;
+  if (pullRequest === undefined) {
+    return false;
+  }
+  const types = pullRequest?.types ?? DEFAULT_PULL_REQUEST_TYPES;
+  return types.includes('synchronize');
+}
+
+const workflows = fs
+  .readdirSync(WORKFLOWS_DIR)
+  .filter((file) => file.endsWith('.yml') || file.endsWith('.yaml'))
+  .map((file): [string, Workflow] => [file, loadWorkflow(file)]);
+
+const supersedable = workflows.filter(([, workflow]) =>
+  isSupersedable(workflow),
+);
+
+describe('Workflow concurrency', () => {
+  it('discovers at least one supersedable workflow', () => {
+    for (const [file, workflow] of workflows) {
+      // js-yaml keeps `on` a string key (YAML 1.2); a missing trigger block
+      // would make every assertion below vacuous.
+      expect(
+        workflow.on,
+        `${file} declares no 'on' trigger block`,
+      ).toBeDefined();
+    }
+
+    expect(supersedable.length).toBeGreaterThan(0);
+  });
+
+  it.each(supersedable)(
+    '%s cancels superseded pull request runs',
+    (file, workflow) => {
+      const concurrency = workflow.concurrency;
+      expect(
+        concurrency,
+        `${file} declares no concurrency group`,
+      ).toBeDefined();
+
+      // The run-id fallback is what keeps runs on main out of a shared group.
+      expect(concurrency?.group).toContain('github.event.pull_request.number');
+      expect(concurrency?.group).toContain('github.run_id');
+      expect(concurrency?.['cancel-in-progress']).toBe(true);
+    },
+  );
+
+  it('release-please.yml never cancels an in-progress release run', () => {
+    const {concurrency} = loadWorkflow('release-please.yml');
+
+    expect(concurrency?.['cancel-in-progress'] ?? false).toBe(false);
+  });
+});