chore: Refactor PR classification + add tests (#2129)

## Summary
- Refactor for readability + add tests
- Allow small agent-branch PRs to reach Tier 2 (< 50 prod lines, ≤ 3 files)
- Add cross-layer detection to keep multi-package changes at Tier 3+
- Raise Tier 2 ceiling from 100 → 150 production lines
- Exclude test and changeset files from line counts used for tier decisions
- Extract pure classification logic into .github/scripts/ for testability
- Gate classify job on tests passing in pr-triage.yml
- Only CI changes to main.yaml and release.yaml are tier 4
- Test changes in critical paths don't count toward tiering decisions

.github/scripts/__tests__/pr-triage-classify.test.js

@@ -0,0 +1,569 @@
+'use strict';
+
+// Tests for the pure classification functions in pr-triage-classify.js.
+// Uses Node's built-in test runner (no extra dependencies required).
+// Run with: node --test .github/scripts/__tests__/pr-triage-classify.test.js
+
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+
+const {
+  isTestFile, isTrivialFile, isCriticalFile,
+  computeSignals, determineTier, buildTierComment,
+} = require('../pr-triage-classify');
+
+// ── Test helpers ─────────────────────────────────────────────────────────────
+
+/** Minimal PR object matching the shape returned by the GitHub API */
+function makePR(login, ref) {
+  return { user: { login }, head: { ref } };
+}
+
+/** Minimal file entry matching the shape returned by pulls.listFiles */
+function makeFile(filename, additions = 10, deletions = 5) {
+  return { filename, additions, deletions };
+}
+
+/** Classify a PR end-to-end from raw inputs (the common test path) */
+function classify(login, ref, files) {
+  return determineTier(computeSignals(makePR(login, ref), files));
+}
+
+// ── File classification helpers ──────────────────────────────────────────────
+
+describe('isTestFile', () => {
+  it('matches __tests__ directory', () => {
+    assert.ok(isTestFile('packages/api/src/__tests__/foo.test.ts'));
+    assert.ok(isTestFile('packages/app/src/components/__tests__/Foo.test.tsx'));
+  });
+
+  it('matches .test.* and .spec.* extensions', () => {
+    assert.ok(isTestFile('packages/app/src/Foo.test.tsx'));
+    assert.ok(isTestFile('packages/app/src/Foo.spec.js'));
+    assert.ok(isTestFile('packages/api/src/bar.test.ts'));
+  });
+
+  it('matches packages/app/tests/ prefix', () => {
+    assert.ok(isTestFile('packages/app/tests/e2e/navigation.ts'));
+  });
+
+  it('does not match regular source files', () => {
+    assert.ok(!isTestFile('packages/api/src/routers/foo.ts'));
+    assert.ok(!isTestFile('packages/app/src/App.tsx'));
+  });
+});
+
+describe('isTrivialFile', () => {
+  it('matches docs and images', () => {
+    assert.ok(isTrivialFile('README.md'));
+    assert.ok(isTrivialFile('docs/setup.txt'));
+    assert.ok(isTrivialFile('assets/logo.png'));
+    assert.ok(isTrivialFile('assets/icon.svg'));
+  });
+
+  it('matches lock files and yarn config', () => {
+    assert.ok(isTrivialFile('yarn.lock'));
+    assert.ok(isTrivialFile('package-lock.json'));
+    assert.ok(isTrivialFile('.yarnrc.yml'));
+  });
+
+  it('matches .changeset/ files', () => {
+    assert.ok(isTrivialFile('.changeset/some-change.md'));
+    assert.ok(isTrivialFile('.changeset/fancy-bears-dance.md'));
+  });
+
+  it('matches .env.example and .github/images/', () => {
+    assert.ok(isTrivialFile('.env.example'));
+    assert.ok(isTrivialFile('.github/images/screenshot.png'));
+  });
+
+  it('matches .github/scripts/ files', () => {
+    assert.ok(isTrivialFile('.github/scripts/pr-triage.js'));
+    assert.ok(isTrivialFile('.github/scripts/pr-triage-classify.js'));
+  });
+
+  it('matches .github/workflows/ files', () => {
+    assert.ok(isTrivialFile('.github/workflows/pr-triage.yml'));
+    assert.ok(isTrivialFile('.github/workflows/knip.yml'));
+    // main.yml and release.yml are also trivial per isTrivialFile, but they are
+    // caught first by isCriticalFile in computeSignals, so they still → Tier 4
+    assert.ok(isTrivialFile('.github/workflows/main.yml'));
+  });
+
+  it('does not match production source files', () => {
+    assert.ok(!isTrivialFile('packages/app/src/App.tsx'));
+    assert.ok(!isTrivialFile('packages/api/src/routers/logs.ts'));
+    assert.ok(!isTrivialFile('Makefile'));
+    assert.ok(!isTrivialFile('knip.json'));
+  });
+});
+
+describe('isCriticalFile', () => {
+  it('matches auth middleware', () => {
+    assert.ok(isCriticalFile('packages/api/src/middleware/auth.ts'));
+    assert.ok(isCriticalFile('packages/api/src/middleware/auth/index.ts'));
+  });
+
+  it('matches sensitive API routes', () => {
+    assert.ok(isCriticalFile('packages/api/src/routers/api/me.ts'));
+    assert.ok(isCriticalFile('packages/api/src/routers/api/team.ts'));
+    assert.ok(isCriticalFile('packages/api/src/routers/external-api/logs.ts'));
+  });
+
+  it('matches core data models', () => {
+    assert.ok(isCriticalFile('packages/api/src/models/user.ts'));
+    assert.ok(isCriticalFile('packages/api/src/models/team.ts'));
+    assert.ok(isCriticalFile('packages/api/src/models/teamInvite.ts'));
+  });
+
+  it('matches config, tasks, otel, clickhouse, and core CI workflows', () => {
+    assert.ok(isCriticalFile('packages/api/src/config.ts'));
+    assert.ok(isCriticalFile('packages/api/src/tasks/alertChecker.ts'));
+    assert.ok(isCriticalFile('packages/otel-collector/config.yaml'));
+    assert.ok(isCriticalFile('docker/clickhouse/config.xml'));
+    assert.ok(isCriticalFile('.github/workflows/main.yml'));
+    assert.ok(isCriticalFile('.github/workflows/release.yml'));
+  });
+
+  it('does NOT flag non-core workflow files as critical', () => {
+    assert.ok(!isCriticalFile('.github/workflows/pr-triage.yml'));
+    assert.ok(!isCriticalFile('.github/workflows/knip.yml'));
+    assert.ok(!isCriticalFile('.github/workflows/claude.yml'));
+  });
+
+  it('matches docker/hyperdx/', () => {
+    assert.ok(isCriticalFile('docker/hyperdx/Dockerfile'));
+  });
+
+  it('does NOT match non-critical API models', () => {
+    assert.ok(!isCriticalFile('packages/api/src/models/alert.ts'));
+    assert.ok(!isCriticalFile('packages/api/src/models/dashboard.ts'));
+  });
+
+  it('does NOT match regular app and API files', () => {
+    assert.ok(!isCriticalFile('packages/app/src/App.tsx'));
+    assert.ok(!isCriticalFile('packages/api/src/routers/logs.ts'));
+  });
+
+  // Note: isCriticalFile DOES return true for test files under critical paths
+  // (e.g. packages/api/src/tasks/tests/util.test.ts). The exclusion happens in
+  // computeSignals, which filters test files out before building criticalFiles.
+  it('returns true for test files under critical paths (exclusion is in computeSignals)', () => {
+    assert.ok(isCriticalFile('packages/api/src/tasks/tests/util.test.ts'));
+  });
+});
+
+// ── computeSignals ───────────────────────────────────────────────────────────
+
+describe('computeSignals', () => {
+  it('separates prod, test, and trivial file line counts', () => {
+    const pr = makePR('alice', 'feature/foo');
+    const files = [
+      makeFile('packages/app/src/Foo.tsx', 20, 5),                     // prod: 25 lines
+      makeFile('packages/app/src/__tests__/Foo.test.tsx', 50, 0),      // test: 50 lines
+      makeFile('README.md', 2, 1),                                      // trivial: excluded
+    ];
+    const s = computeSignals(pr, files);
+    assert.equal(s.prodFiles.length, 1);
+    assert.equal(s.prodLines, 25);
+    assert.equal(s.testLines, 50);
+  });
+
+  it('excludes changeset files from prod counts', () => {
+    const pr = makePR('alice', 'feature/foo');
+    const files = [
+      makeFile('packages/app/src/Foo.tsx', 20, 5),
+      makeFile('.changeset/witty-foxes-run.md', 5, 0),  // trivial
+    ];
+    const s = computeSignals(pr, files);
+    assert.equal(s.prodFiles.length, 1);
+    assert.equal(s.prodLines, 25);
+  });
+
+  it('detects agent branches by prefix', () => {
+    for (const prefix of ['claude/', 'agent/', 'ai/']) {
+      const s = computeSignals(makePR('alice', `${prefix}fix-thing`), []);
+      assert.ok(s.isAgentBranch, `expected isAgentBranch for prefix "${prefix}"`);
+    }
+    assert.ok(!computeSignals(makePR('alice', 'feature/normal'), []).isAgentBranch);
+  });
+
+  it('detects bot authors', () => {
+    assert.ok(computeSignals(makePR('dependabot[bot]', 'dependabot/npm/foo'), []).isBotAuthor);
+    assert.ok(!computeSignals(makePR('alice', 'feature/foo'), []).isBotAuthor);
+  });
+
+  it('sets allFilesTrivial when every file is trivial', () => {
+    const files = [makeFile('README.md'), makeFile('yarn.lock')];
+    assert.ok(computeSignals(makePR('alice', 'docs/update'), files).allFilesTrivial);
+  });
+
+  it('does not set allFilesTrivial for mixed files', () => {
+    const files = [makeFile('README.md'), makeFile('packages/app/src/Foo.tsx')];
+    assert.ok(!computeSignals(makePR('alice', 'feat/foo'), files).allFilesTrivial);
+  });
+
+  it('detects cross-layer changes (frontend + backend)', () => {
+    const files = [
+      makeFile('packages/app/src/NewFeature.tsx'),         // frontend
+      makeFile('packages/api/src/services/newFeature.ts'), // backend (not models/routers)
+    ];
+    const s = computeSignals(makePR('alice', 'feat/new'), files);
+    assert.ok(s.isCrossLayer);
+    assert.ok(s.touchesFrontend);
+    assert.ok(s.touchesBackend);
+  });
+
+  it('detects cross-layer changes (backend + shared-utils)', () => {
+    const files = [
+      makeFile('packages/api/src/services/foo.ts'),
+      makeFile('packages/common-utils/src/queryParser.ts'),
+    ];
+    const s = computeSignals(makePR('alice', 'feat/foo'), files);
+    assert.ok(s.isCrossLayer);
+    assert.ok(s.touchesSharedUtils);
+  });
+
+  it('does not flag single-package changes as cross-layer', () => {
+    const files = [
+      makeFile('packages/app/src/Foo.tsx'),
+      makeFile('packages/app/src/Bar.tsx'),
+    ];
+    assert.ok(!computeSignals(makePR('alice', 'feat/foo'), files).isCrossLayer);
+  });
+
+  it('blocks agent branch from Tier 2 when prod lines exceed threshold', () => {
+    // 60 prod lines > AGENT_TIER2_MAX_LINES (50)
+    const s = computeSignals(makePR('alice', 'claude/feature'), [
+      makeFile('packages/app/src/Foo.tsx', 60, 0),
+    ]);
+    assert.ok(s.agentBlocksTier2);
+  });
+
+  it('blocks agent branch from Tier 2 when prod file count exceeds threshold', () => {
+    // 5 prod files > AGENT_TIER2_MAX_PROD_FILES (3)
+    const files = Array.from({ length: 5 }, (_, i) =>
+      makeFile(`packages/app/src/File${i}.tsx`, 5, 2)
+    );
+    const s = computeSignals(makePR('alice', 'claude/feature'), files);
+    assert.ok(s.agentBlocksTier2);
+  });
+
+  it('does NOT block agent branch when change is small and focused', () => {
+    // 16 prod lines, 1 prod file — well under both thresholds
+    const s = computeSignals(makePR('mikeshi', 'claude/fix-mobile-nav'), [
+      makeFile('packages/app/src/AppNav.tsx', 11, 5),
+    ]);
+    assert.ok(!s.agentBlocksTier2);
+  });
+});
+
+// ── determineTier ────────────────────────────────────────────────────────────
+
+describe('determineTier', () => {
+  describe('Tier 1', () => {
+    it('bot author', () => {
+      assert.equal(classify('dependabot[bot]', 'dependabot/npm/foo', [
+        makeFile('package.json', 5, 3),
+      ]), 1);
+    });
+
+    // package.json is not in TIER1_PATTERNS (it's a production file), but bot
+    // author short-circuits to Tier 1 before the trivial-file check fires.
+    it('bot author with package.json (non-trivial file) is still Tier 1', () => {
+      assert.equal(classify('dependabot[bot]', 'dependabot/npm/lodash', [
+        makeFile('package.json', 5, 3),
+        makeFile('packages/api/package.json', 2, 2),
+      ]), 1);
+    });
+
+    it('all trivial files (docs + lock)', () => {
+      assert.equal(classify('alice', 'docs/update-readme', [
+        makeFile('README.md', 10, 2),
+        makeFile('docs/setup.md', 5, 0),
+        makeFile('yarn.lock', 100, 80),
+      ]), 1);
+    });
+
+    it('changeset-only PR', () => {
+      assert.equal(classify('alice', 'release/v2.1', [
+        makeFile('.changeset/witty-foxes-run.md', 4, 0),
+      ]), 1);
+    });
+  });
+
+  describe('Tier 4', () => {
+    it('touches auth middleware', () => {
+      assert.equal(classify('alice', 'fix/auth-bug', [
+        makeFile('packages/api/src/middleware/auth.ts', 20, 5),
+      ]), 4);
+    });
+
+    it('touches ClickHouse docker config', () => {
+      assert.equal(classify('alice', 'infra/clickhouse-update', [
+        makeFile('docker/clickhouse/config.xml', 10, 2),
+      ]), 4);
+    });
+
+    it('touches main.yml or release.yml', () => {
+      assert.equal(classify('alice', 'ci/add-step', [
+        makeFile('.github/workflows/main.yml', 15, 3),
+      ]), 4);
+      assert.equal(classify('alice', 'ci/release-fix', [
+        makeFile('.github/workflows/release.yml', 8, 2),
+      ]), 4);
+    });
+
+    it('non-critical workflow-only changes are Tier 1 (workflow files are trivial)', () => {
+      assert.equal(classify('alice', 'ci/add-triage-step', [
+        makeFile('.github/workflows/pr-triage.yml', 10, 2),
+      ]), 1);
+    });
+
+    it('does NOT flag test files under critical paths as Tier 4', () => {
+      // e.g. packages/api/src/tasks/tests/util.test.ts should not be critical
+      assert.equal(classify('alice', 'feat/alert-tests', [
+        makeFile('packages/api/src/tasks/tests/util.test.ts', 40, 0),
+        makeFile('packages/api/src/tasks/checkAlerts/tests/checkAlerts.test.ts', 80, 0),
+      ]), 2);
+    });
+
+    it('touches core user/team models', () => {
+      assert.equal(classify('alice', 'feat/user-fields', [
+        makeFile('packages/api/src/models/user.ts', 10, 2),
+      ]), 4);
+    });
+
+    it('escalates Tier 3 human branch past 1000 prod lines', () => {
+      assert.equal(classify('alice', 'feat/huge-refactor', [
+        makeFile('packages/app/src/BigComponent.tsx', 600, 450),  // 1050 lines
+      ]), 4);
+    });
+
+    it('escalates Tier 3 agent branch past 400 prod lines (stricter threshold)', () => {
+      assert.equal(classify('alice', 'claude/large-feature', [
+        makeFile('packages/app/src/BigFeature.tsx', 300, 120),  // 420 lines
+      ]), 4);
+    });
+  });
+
+  describe('Tier 2', () => {
+    it('small single-layer frontend change', () => {
+      assert.equal(classify('alice', 'fix/button-style', [
+        makeFile('packages/app/src/components/Button.tsx', 20, 10),
+      ]), 2);
+    });
+
+    it('small single-layer backend change (not models/routers)', () => {
+      assert.equal(classify('alice', 'fix/service-bug', [
+        makeFile('packages/api/src/services/logs.ts', 30, 15),
+      ]), 2);
+    });
+
+    it('agent branch small enough to qualify (PR #1431 pattern: 1 file, 16 lines)', () => {
+      assert.equal(classify('mikeshi', 'claude/fix-mobile-nav', [
+        makeFile('packages/app/src/AppNav.tsx', 11, 5),
+      ]), 2);
+    });
+
+    it('agent branch exactly at file limit (3 prod files, small lines)', () => {
+      const files = Array.from({ length: 3 }, (_, i) =>
+        makeFile(`packages/app/src/File${i}.tsx`, 10, 5)
+      );
+      assert.equal(classify('alice', 'claude/small-multi', files), 2);
+    });
+
+    it('human branch at 149 prod lines (just under threshold)', () => {
+      assert.equal(classify('alice', 'fix/component', [
+        makeFile('packages/app/src/Foo.tsx', 100, 49),  // 149 lines
+      ]), 2);
+    });
+
+    it('agent branch at exactly 49 prod lines qualifies for Tier 2', () => {
+      assert.equal(classify('alice', 'claude/fix', [
+        makeFile('packages/app/src/Foo.tsx', 49, 0),
+      ]), 2);
+    });
+  });
+
+  describe('Tier 3', () => {
+    it('cross-layer change (frontend + backend)', () => {
+      assert.equal(classify('alice', 'feat/new-feature', [
+        makeFile('packages/app/src/NewFeature.tsx', 30, 5),
+        makeFile('packages/api/src/services/newFeature.ts', 40, 10),
+      ]), 3);
+    });
+
+    it('touches API routes (non-critical)', () => {
+      assert.equal(classify('alice', 'feat/new-route', [
+        makeFile('packages/api/src/routers/logs.ts', 30, 5),
+      ]), 3);
+    });
+
+    it('touches API models (non-critical)', () => {
+      assert.equal(classify('alice', 'feat/model-field', [
+        makeFile('packages/api/src/models/alert.ts', 20, 3),
+      ]), 3);
+    });
+
+    it('agent branch at exactly 50 prod lines is blocked from Tier 2', () => {
+      assert.equal(classify('alice', 'claude/feature', [
+        makeFile('packages/app/src/Foo.tsx', 50, 0),  // exactly AGENT_TIER2_MAX_LINES — >= blocks it
+      ]), 3);
+    });
+
+    it('agent branch over prod-line threshold (60 > 50) → Tier 3, not Tier 2', () => {
+      assert.equal(classify('alice', 'claude/medium-feature', [
+        makeFile('packages/app/src/Foo.tsx', 60, 0),
+      ]), 3);
+    });
+
+    it('agent branch over file count threshold (4 files) → Tier 3', () => {
+      const files = Array.from({ length: 4 }, (_, i) =>
+        makeFile(`packages/app/src/File${i}.tsx`, 10, 5)
+      );
+      assert.equal(classify('alice', 'claude/big-feature', files), 3);
+    });
+
+    it('does NOT escalate agent branch at exactly 400 lines (threshold is exclusive)', () => {
+      // prodLines > threshold, not >=, so 400 stays at Tier 3
+      assert.equal(classify('alice', 'claude/medium-large', [
+        makeFile('packages/app/src/Feature.tsx', 200, 200),  // exactly 400
+      ]), 3);
+    });
+
+    it('large test additions with small prod change stay Tier 3 (PR #2122 pattern)', () => {
+      // Alert threshold PR: 1300 total adds but ~1100 are tests
+      const files = [
+        makeFile('packages/api/src/services/checkAlerts.ts', 180, 70),       // prod: 250 lines
+        makeFile('packages/api/src/__tests__/checkAlerts.test.ts', 1100, 0), // test: excluded
+      ];
+      // 250 prod lines > TIER2_MAX_LINES (150) → Tier 3, not Tier 4
+      assert.equal(classify('alice', 'feat/alert-thresholds', files), 3);
+    });
+
+    it('human branch at exactly 150 prod lines is Tier 3, not Tier 2', () => {
+      assert.equal(classify('alice', 'fix/component', [
+        makeFile('packages/app/src/Foo.tsx', 100, 50),  // exactly TIER2_MAX_LINES — < is exclusive
+      ]), 3);
+    });
+
+    it('does NOT escalate human branch at exactly 1000 prod lines', () => {
+      assert.equal(classify('alice', 'feat/medium-large', [
+        makeFile('packages/app/src/Feature.tsx', 500, 500),  // exactly 1000
+      ]), 3);
+    });
+  });
+});
+
+// ── buildTierComment ─────────────────────────────────────────────────────────
+
+describe('buildTierComment', () => {
+  /** Build a signal object with sensible defaults, overrideable per test */
+  function makeSignals(overrides = {}) {
+    return {
+      author: 'alice',
+      branchName: 'feature/foo',
+      prodFiles: [makeFile('packages/app/src/Foo.tsx')],
+      prodLines: 50,
+      testLines: 0,
+      criticalFiles: [],
+      isAgentBranch: false,
+      isBotAuthor: false,
+      allFilesTrivial: false,
+      touchesApiModels: false,
+      touchesFrontend: true,
+      touchesBackend: false,
+      touchesSharedUtils: false,
+      isCrossLayer: false,
+      agentBlocksTier2: false,
+      ...overrides,
+    };
+  }
+
+  it('always includes the pr-triage sentinel marker', () => {
+    assert.ok(buildTierComment(2, makeSignals()).includes('<!-- pr-triage -->'));
+  });
+
+  it('includes the correct headline for each tier', () => {
+    assert.ok(buildTierComment(1, makeSignals()).includes('Tier 1'));
+    assert.ok(buildTierComment(2, makeSignals()).includes('Tier 2'));
+    assert.ok(buildTierComment(3, makeSignals()).includes('Tier 3'));
+    assert.ok(buildTierComment(4, makeSignals()).includes('Tier 4'));
+  });
+
+  it('includes override instructions with the correct tier label', () => {
+    const body = buildTierComment(3, makeSignals());
+    assert.ok(body.includes('review/tier-3'));
+    assert.ok(body.includes('Manual overrides are preserved'));
+  });
+
+  it('lists critical files when present', () => {
+    const signals = makeSignals({
+      criticalFiles: [makeFile('packages/api/src/middleware/auth.ts')],
+    });
+    const body = buildTierComment(4, signals);
+    assert.ok(body.includes('Critical-path files'));
+    assert.ok(body.includes('auth.ts'));
+  });
+
+  it('explains cross-layer trigger with which layers are involved', () => {
+    const signals = makeSignals({
+      isCrossLayer: true,
+      touchesFrontend: true,
+      touchesBackend: true,
+      touchesSharedUtils: false,
+    });
+    const body = buildTierComment(3, signals);
+    assert.ok(body.includes('Cross-layer change'));
+    assert.ok(body.includes('packages/app'));
+    assert.ok(body.includes('packages/api'));
+  });
+
+  it('explains API model/route trigger', () => {
+    const body = buildTierComment(3, makeSignals({ touchesApiModels: true }));
+    assert.ok(body.includes('API routes or data models'));
+  });
+
+  it('explains agent branch bump to Tier 3', () => {
+    const signals = makeSignals({
+      isAgentBranch: true,
+      agentBlocksTier2: true,
+      branchName: 'claude/big-feature',
+      prodLines: 80,
+      prodFiles: Array.from({ length: 5 }, (_, i) => makeFile(`packages/app/src/File${i}.tsx`)),
+    });
+    const body = buildTierComment(3, signals);
+    assert.ok(body.includes('bumped to Tier 3'));
+  });
+
+  it('notes when agent branch is small enough for Tier 2', () => {
+    const signals = makeSignals({
+      isAgentBranch: true,
+      agentBlocksTier2: false,
+      branchName: 'claude/tiny-fix',
+    });
+    const body = buildTierComment(2, signals);
+    assert.ok(body.includes('small enough to qualify for Tier 2'));
+  });
+
+  it('shows test line count in stats when non-zero', () => {
+    const body = buildTierComment(2, makeSignals({ testLines: 200 }));
+    assert.ok(body.includes('200 in test files'));
+  });
+
+  it('omits test line note when testLines is 0', () => {
+    const body = buildTierComment(2, makeSignals({ testLines: 0 }));
+    assert.ok(!body.includes('test files'));
+  });
+
+  it('includes a catch-all trigger for standard Tier 3 PRs with no specific signals', () => {
+    const body = buildTierComment(3, makeSignals());
+    assert.ok(body.includes('Standard feature/fix'));
+  });
+
+  it('includes bot-author trigger for Tier 1 bot PRs', () => {
+    const body = buildTierComment(1, makeSignals({ isBotAuthor: true, author: 'dependabot[bot]' }));
+    assert.ok(body.includes('Bot author'));
+  });
+});

.github/scripts/pr-triage-classify.js

@@ -0,0 +1,257 @@
+'use strict';
+
+// ── File classification patterns ─────────────────────────────────────────────
+const TIER4_PATTERNS = [
+  /^packages\/api\/src\/middleware\/auth/,
+  /^packages\/api\/src\/routers\/api\/me\./,
+  /^packages\/api\/src\/routers\/api\/team\./,
+  /^packages\/api\/src\/routers\/external-api\//,
+  /^packages\/api\/src\/models\/(user|team|teamInvite)\./,
+  /^packages\/api\/src\/config\./,
+  /^packages\/api\/src\/tasks\//,
+  /^packages\/otel-collector\//,
+  /^docker\/otel-collector\//,
+  /^docker\/clickhouse\//,
+  /^docker\/hyperdx\//,
+  /^\.github\/workflows\/(main|release)\.yml$/,
+];
+
+const TIER1_PATTERNS = [
+  /\.(md|txt|png|jpg|jpeg|gif|svg|ico)$/i,
+  /^yarn\.lock$/,
+  /^package-lock\.json$/,
+  /^\.yarnrc\.yml$/,
+  /^\.github\/images\//,
+  /^\.env\.example$/,
+  /^\.changeset\//,  // version-bump config files; no functional code
+  /^\.github\/scripts\//,   // GitHub Actions scripts; not application code
+  /^\.github\/workflows\//,  // workflow files (main.yml/release.yml still caught by TIER4_PATTERNS)
+];
+
+const TEST_FILE_PATTERNS = [
+  /\/__tests__\//,
+  /\.test\.[jt]sx?$/,
+  /\.spec\.[jt]sx?$/,
+  /^packages\/app\/tests\//,
+];
+
+// ── Thresholds (all line counts exclude test and trivial files) ───────────────
+const TIER2_MAX_LINES = 150;           // max prod lines eligible for Tier 2
+const TIER4_ESCALATION_HUMAN = 1000;   // Tier 3 → 4 for human branches
+const TIER4_ESCALATION_AGENT = 400;    // Tier 3 → 4 for agent branches (stricter)
+
+// Agent branches can reach Tier 2 only for very small, focused changes
+const AGENT_TIER2_MAX_LINES = 50;
+const AGENT_TIER2_MAX_PROD_FILES = 3;
+
+// ── Other constants ──────────────────────────────────────────────────────────
+const BOT_AUTHORS = ['dependabot', 'dependabot[bot]'];
+const AGENT_BRANCH_PREFIXES = ['claude/', 'agent/', 'ai/'];
+
+const TIER_LABELS = {
+  1: { name: 'review/tier-1', color: '0E8A16', description: 'Trivial — auto-merge candidate once CI passes' },
+  2: { name: 'review/tier-2', color: '1D76DB', description: 'Low risk — AI review + quick human skim' },
+  3: { name: 'review/tier-3', color: 'E4E669', description: 'Standard — full human review required' },
+  4: { name: 'review/tier-4', color: 'B60205', description: 'Critical — deep review + domain expert sign-off' },
+};
+
+const TIER_INFO = {
+  1: {
+    emoji: '🟢',
+    headline: 'Tier 1 — Trivial',
+    detail: 'Docs, images, lock files, or a dependency bump. No functional code changes detected.',
+    process: 'Auto-merge once CI passes. No human review required.',
+    sla: 'Resolves automatically.',
+  },
+  2: {
+    emoji: '🔵',
+    headline: 'Tier 2 — Low Risk',
+    detail: 'Small, isolated change with no API route or data model modifications.',
+    process: 'AI review + quick human skim (target: 5–15 min). Reviewer validates AI assessment and checks for domain-specific concerns.',
+    sla: 'Resolve within 4 business hours.',
+  },
+  3: {
+    emoji: '🟡',
+    headline: 'Tier 3 — Standard',
+    detail: 'Introduces new logic, modifies core functionality, or touches areas with non-trivial risk.',
+    process: 'Full human review — logic, architecture, edge cases.',
+    sla: 'First-pass feedback within 1 business day.',
+  },
+  4: {
+    emoji: '🔴',
+    headline: 'Tier 4 — Critical',
+    detail: 'Touches auth, data models, config, tasks, OTel pipeline, ClickHouse, or CI/CD.',
+    process: 'Deep review from a domain expert. Synchronous walkthrough may be required.',
+    sla: 'Schedule synchronous review within 2 business days.',
+  },
+};
+
+// ── File classification helpers ──────────────────────────────────────────────
+const isTestFile    = f => TEST_FILE_PATTERNS.some(p => p.test(f));
+const isTrivialFile = f => TIER1_PATTERNS.some(p => p.test(f));
+const isCriticalFile = f => TIER4_PATTERNS.some(p => p.test(f));
+
+// ── Signal computation ───────────────────────────────────────────────────────
+// Returns a flat object of all facts needed for tier determination and comment
+// generation. All derived from PR metadata + file list — no GitHub API calls.
+//
+// @param {object} pr       - GitHub PR object: { user: { login }, head: { ref } }
+// @param {Array}  filesRes - GitHub files array: [{ filename, additions, deletions }]
+function computeSignals(pr, filesRes) {
+  const author     = pr.user.login;
+  const branchName = pr.head.ref;
+
+  const testFiles     = filesRes.filter(f => isTestFile(f.filename));
+  const prodFiles     = filesRes.filter(f => !isTestFile(f.filename) && !isTrivialFile(f.filename));
+  const criticalFiles = filesRes.filter(f => isCriticalFile(f.filename) && !isTestFile(f.filename));
+
+  const prodLines = prodFiles.reduce((sum, f) => sum + f.additions + f.deletions, 0);
+  const testLines = testFiles.reduce((sum, f) => sum + f.additions + f.deletions, 0);
+
+  const isAgentBranch   = AGENT_BRANCH_PREFIXES.some(p => branchName.startsWith(p));
+  const isBotAuthor     = BOT_AUTHORS.includes(author);
+  const allFilesTrivial = filesRes.length > 0 && filesRes.every(f => isTrivialFile(f.filename));
+
+  // Blocks Tier 2 — API models and routes carry implicit cross-cutting risk
+  const touchesApiModels = prodFiles.some(f =>
+    f.filename.startsWith('packages/api/src/models/') ||
+    f.filename.startsWith('packages/api/src/routers/')
+  );
+
+  // Cross-layer: production changes spanning multiple monorepo packages
+  const touchesFrontend    = prodFiles.some(f => f.filename.startsWith('packages/app/'));
+  const touchesBackend     = prodFiles.some(f => f.filename.startsWith('packages/api/'));
+  const touchesSharedUtils = prodFiles.some(f => f.filename.startsWith('packages/common-utils/'));
+  const isCrossLayer = [touchesFrontend, touchesBackend, touchesSharedUtils].filter(Boolean).length >= 2;
+
+  // Agent branches can reach Tier 2 only when the change is very small and focused
+  const agentBlocksTier2 = isAgentBranch &&
+    (prodLines >= AGENT_TIER2_MAX_LINES || prodFiles.length > AGENT_TIER2_MAX_PROD_FILES);
+
+  return {
+    author, branchName,
+    prodFiles, prodLines, testLines, criticalFiles,
+    isAgentBranch, isBotAuthor, allFilesTrivial,
+    touchesApiModels, touchesFrontend, touchesBackend, touchesSharedUtils,
+    isCrossLayer, agentBlocksTier2,
+  };
+}
+
+// ── Tier determination ───────────────────────────────────────────────────────
+// @param {object} signals - output of computeSignals()
+// @returns {number} tier  - 1 | 2 | 3 | 4
+function determineTier(signals) {
+  const {
+    criticalFiles, isBotAuthor, allFilesTrivial,
+    prodLines, touchesApiModels, isCrossLayer, agentBlocksTier2, isAgentBranch,
+  } = signals;
+
+  // Tier 4: touches critical infrastructure (auth, config, pipeline, CI/CD)
+  if (criticalFiles.length > 0) return 4;
+
+  // Tier 1: bot-authored or only docs/images/lock files changed
+  if (isBotAuthor || allFilesTrivial) return 1;
+
+  // Tier 2: small, isolated, single-layer change
+  //   Agent branches qualify when the change is very small and focused
+  //   (agentBlocksTier2 is false when under AGENT_TIER2_MAX_LINES / MAX_PROD_FILES)
+  const qualifiesForTier2 =
+    prodLines < TIER2_MAX_LINES &&
+    !touchesApiModels &&
+    !isCrossLayer &&
+    !agentBlocksTier2;
+  if (qualifiesForTier2) return 2;
+
+  // Tier 3: everything else — escalate very large diffs to Tier 4
+  const sizeThreshold = isAgentBranch ? TIER4_ESCALATION_AGENT : TIER4_ESCALATION_HUMAN;
+  return prodLines > sizeThreshold ? 4 : 3;
+}
+
+// ── Comment generation ───────────────────────────────────────────────────────
+// @param {number} tier    - 1 | 2 | 3 | 4
+// @param {object} signals - output of computeSignals()
+// @returns {string}       - Markdown comment body
+function buildTierComment(tier, signals) {
+  const {
+    author, branchName,
+    prodFiles, prodLines, testLines, criticalFiles,
+    isAgentBranch, isBotAuthor, allFilesTrivial,
+    touchesApiModels, touchesFrontend, touchesBackend, touchesSharedUtils,
+    isCrossLayer, agentBlocksTier2,
+  } = signals;
+
+  const info = TIER_INFO[tier];
+  const sizeThreshold = isAgentBranch ? TIER4_ESCALATION_AGENT : TIER4_ESCALATION_HUMAN;
+
+  // Primary triggers — the specific reasons this tier was assigned
+  const triggers = [];
+  if (criticalFiles.length > 0) {
+    triggers.push(`**Critical-path files** (${criticalFiles.length}):\n${criticalFiles.map(f => `    - \`${f.filename}\``).join('\n')}`);
+  }
+  if (tier === 4 && prodLines > sizeThreshold && criticalFiles.length === 0) {
+    triggers.push(`**Large diff**: ${prodLines} production lines changed (threshold: ${sizeThreshold})`);
+  }
+  if (isBotAuthor) triggers.push(`**Bot author**: \`${author}\``);
+  if (allFilesTrivial && !isBotAuthor) triggers.push('**All files are docs / images / lock files**');
+  if (isCrossLayer) {
+    const layers = [
+      touchesFrontend    && 'frontend (`packages/app`)',
+      touchesBackend     && 'backend (`packages/api`)',
+      touchesSharedUtils && 'shared utils (`packages/common-utils`)',
+    ].filter(Boolean);
+    triggers.push(`**Cross-layer change**: touches ${layers.join(' + ')}`);
+  }
+  if (touchesApiModels && criticalFiles.length === 0) {
+    triggers.push('**Touches API routes or data models** — hidden complexity risk');
+  }
+  if (isAgentBranch && agentBlocksTier2 && tier <= 3) {
+    triggers.push(`**Agent-generated branch** (\`${branchName}\`) with ${prodLines} prod lines across ${prodFiles.length} files — bumped to Tier 3 for mandatory human review`);
+  }
+  if (triggers.length === 0) {
+    triggers.push('**Standard feature/fix** — introduces new logic or modifies core functionality');
+  }
+
+  // Informational context — didn't drive the tier on their own
+  const contextSignals = [];
+  if (isAgentBranch && !agentBlocksTier2 && tier === 2) {
+    contextSignals.push(`agent branch (\`${branchName}\`) — change small enough to qualify for Tier 2`);
+  } else if (isAgentBranch && tier === 4) {
+    contextSignals.push(`agent branch (\`${branchName}\`)`);
+  }
+
+  const triggerSection = `\n**Why this tier:**\n${triggers.map(t => `- ${t}`).join('\n')}`;
+  const contextSection = contextSignals.length > 0
+    ? `\n**Additional context:** ${contextSignals.join(', ')}`
+    : '';
+
+  return [
+    '<!-- pr-triage -->',
+    `## ${info.emoji} ${info.headline}`,
+    '',
+    info.detail,
+    triggerSection,
+    contextSection,
+    '',
+    `**Review process**: ${info.process}`,
+    `**SLA**: ${info.sla}`,
+    '',
+    '<details><summary>Stats</summary>',
+    '',
+    `- Production files changed: ${prodFiles.length}`,
+    `- Production lines changed: ${prodLines}${testLines > 0 ? ` (+ ${testLines} in test files, excluded from tier calculation)` : ''}`,
+    `- Branch: \`${branchName}\``,
+    `- Author: ${author}`,
+    '',
+    '</details>',
+    '',
+    `> To override this classification, remove the \`${TIER_LABELS[tier].name}\` label and apply a different \`review/tier-*\` label. Manual overrides are preserved on subsequent pushes.`,
+  ].join('\n');
+}
+
+module.exports = {
+  // Constants needed by the orchestration script
+  TIER_LABELS, TIER_INFO,
+  // Pure functions
+  isTestFile, isTrivialFile, isCriticalFile,
+  computeSignals, determineTier, buildTierComment,
+};

.github/scripts/pr-triage.js

@@ -0,0 +1,123 @@
+'use strict';
+
+// Entry point for actions/github-script@v7 via script-path.
+// Pure classification logic lives in pr-triage-classify.js so it can be
+// unit-tested without GitHub API machinery.
+
+const {
+  TIER_LABELS,
+  computeSignals, determineTier, buildTierComment,
+} = require('./pr-triage-classify');
+
+module.exports = async ({ github, context }) => {
+  const owner = context.repo.owner;
+  const repo  = context.repo.repo;
+
+  // ── Determine which PRs to process ──────────────────────────────────────
+  let prNumbers;
+  if (context.eventName === 'workflow_dispatch') {
+    // Use context.payload.inputs to avoid script-injection via template interpolation
+    const input = (context.payload.inputs?.pr_number ?? '').trim();
+    if (input !== '') {
+      const num = Number(input);
+      if (!Number.isInteger(num) || num <= 0) {
+        throw new Error(`Invalid PR number: "${input}"`);
+      }
+      prNumbers = [num];
+    } else {
+      const openPRs = await github.paginate(
+        github.rest.pulls.list,
+        { owner, repo, state: 'open', per_page: 100 }
+      );
+      prNumbers = openPRs.map(pr => pr.number);
+      console.log(`Bulk triage: found ${prNumbers.length} open PRs`);
+    }
+  } else {
+    prNumbers = [context.payload.pull_request.number];
+  }
+
+  // ── Ensure tier labels exist (once, before the loop) ────────────────────
+  const repoLabels = await github.paginate(
+    github.rest.issues.listLabelsForRepo,
+    { owner, repo, per_page: 100 }
+  );
+  const repoLabelNames = new Set(repoLabels.map(l => l.name));
+  for (const label of Object.values(TIER_LABELS)) {
+    if (!repoLabelNames.has(label.name)) {
+      await github.rest.issues.createLabel({ owner, repo, ...label });
+      repoLabelNames.add(label.name);
+    }
+  }
+
+  // ── Classify a single PR ─────────────────────────────────────────────────
+  async function classifyPR(prNumber) {
+    const filesRes = await github.paginate(
+      github.rest.pulls.listFiles,
+      { owner, repo, pull_number: prNumber, per_page: 100 }
+    );
+    const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number: prNumber });
+    const { data: currentLabels } = await github.rest.issues.listLabelsOnIssue({ owner, repo, issue_number: prNumber });
+    const currentLabelNames = new Set(currentLabels.map(l => l.name));
+
+    // Skip drafts (bulk mode; PR events already filter these via the job condition)
+    if (pr.draft) {
+      console.log(`PR #${prNumber}: skipping draft`);
+      return;
+    }
+
+    // Respect manual tier overrides — don't overwrite labels applied by humans
+    const existingTierLabel = currentLabels.find(l => l.name.startsWith('review/tier-'));
+    if (existingTierLabel) {
+      const events = await github.paginate(
+        github.rest.issues.listEvents,
+        { owner, repo, issue_number: prNumber, per_page: 100 }
+      );
+      const lastLabelEvent = events
+        .filter(e => e.event === 'labeled' && e.label?.name === existingTierLabel.name)
+        .pop();
+      if (lastLabelEvent && lastLabelEvent.actor.type !== 'Bot') {
+        console.log(`PR #${prNumber}: tier manually set to ${existingTierLabel.name} by ${lastLabelEvent.actor.login} — skipping`);
+        return;
+      }
+    }
+
+    const signals = computeSignals(pr, filesRes);
+    const tier    = determineTier(signals);
+    const body    = buildTierComment(tier, signals);
+
+    // Apply the tier label (remove any stale tier label first)
+    for (const label of currentLabels) {
+      if (label.name.startsWith('review/tier-') && label.name !== TIER_LABELS[tier].name) {
+        await github.rest.issues.removeLabel({ owner, repo, issue_number: prNumber, name: label.name });
+      }
+    }
+    if (!currentLabelNames.has(TIER_LABELS[tier].name)) {
+      await github.rest.issues.addLabels({ owner, repo, issue_number: prNumber, labels: [TIER_LABELS[tier].name] });
+    }
+
+    // Post or update the triage comment
+    const comments = await github.paginate(
+      github.rest.issues.listComments,
+      { owner, repo, issue_number: prNumber, per_page: 100 }
+    );
+    const existingComment = comments.find(
+      c => c.user.login === 'github-actions[bot]' && c.body.includes('<!-- pr-triage -->')
+    );
+    if (existingComment) {
+      await github.rest.issues.updateComment({ owner, repo, comment_id: existingComment.id, body });
+    } else {
+      await github.rest.issues.createComment({ owner, repo, issue_number: prNumber, body });
+    }
+
+    console.log(`PR #${prNumber}: Tier ${tier} (${signals.prodLines} prod lines, ${signals.prodFiles.length} prod files, ${signals.testLines} test lines)`);
+  }
+
+  // ── Process all target PRs ───────────────────────────────────────────────
+  for (const prNumber of prNumbers) {
+    try {
+      await classifyPR(prNumber);
+    } catch (err) {
+      console.error(`PR #${prNumber}: classification failed — ${err.message}`);
+    }
+  }
+};

.github/workflows/pr-triage.yml

@@ -2,6 +2,7 @@ name: PR Triage
 
 on:
   pull_request:
+    branches: [main]
     types: [opened, synchronize, reopened, ready_for_review]
   workflow_dispatch:
     inputs:
@@ -16,278 +17,39 @@ permissions:
   pull-requests: write
   issues: write
 
+concurrency:
+  group:
+    ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id
+    }}
+  cancel-in-progress: true
+
 jobs:
+  test:
+    name: Test triage logic
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+      - run: node --test .github/scripts/__tests__/pr-triage-classify.test.js
+
   classify:
     name: Classify PR risk tier
+    needs: test
     runs-on: ubuntu-24.04
+    timeout-minutes: 8
     # For pull_request events skip drafts; workflow_dispatch always runs
     if:
       ${{ github.event_name == 'workflow_dispatch' ||
       !github.event.pull_request.draft }}
     steps:
+      - uses: actions/checkout@v4
       - name: Classify and label PR(s)
         uses: actions/github-script@v7
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           script: |
-            const owner = context.repo.owner;
+            const path = require('path');
-            const repo = context.repo.repo;
+            const run = require(path.join(process.env.GITHUB_WORKSPACE, '.github/scripts/pr-triage.js'));
-
+            await run({ github, context });
-            // ── Determine which PRs to process ──────────────────────────────
-            let prNumbers;
-            if (context.eventName === 'workflow_dispatch') {
-              // Use context.payload.inputs to avoid script-injection via template interpolation
-              const input = (context.payload.inputs?.pr_number ?? '').trim();
-              if (input && input !== '') {
-                prNumbers = [Number(input)];
-              } else {
-                const openPRs = await github.paginate(
-                  github.rest.pulls.list,
-                  { owner, repo, state: 'open', per_page: 100 }
-                );
-                prNumbers = openPRs.map(pr => pr.number);
-                console.log(`Bulk triage: found ${prNumbers.length} open PRs`);
-              }
-            } else {
-              prNumbers = [context.payload.pull_request.number];
-            }
-
-            // ── Shared constants ─────────────────────────────────────────────
-            const TIER4_PATTERNS = [
-              /^packages\/api\/src\/middleware\/auth/,
-              /^packages\/api\/src\/routers\/api\/me\./,
-              /^packages\/api\/src\/routers\/api\/team\./,
-              /^packages\/api\/src\/routers\/external-api\//,
-              /^packages\/api\/src\/models\/(user|team|teamInvite)\./,
-              /^packages\/api\/src\/config\./,
-              /^packages\/api\/src\/tasks\//,
-              /^packages\/otel-collector\//,
-              /^docker\/otel-collector\//,
-              /^docker\/clickhouse\//,
-              /^\.github\/workflows\//,
-            ];
-
-            const TIER1_PATTERNS = [
-              /\.(md|txt|png|jpg|jpeg|gif|svg|ico)$/i,
-              /^yarn\.lock$/,
-              /^package-lock\.json$/,
-              /^\.yarnrc\.yml$/,
-              /^\.github\/images\//,
-              /^\.env\.example$/,
-            ];
-
-            const BOT_AUTHORS = ['dependabot', 'dependabot[bot]'];
-            const AGENT_BRANCH_PREFIXES = ['claude/', 'agent/', 'ai/'];
-
-            const TIER_LABELS = {
-              1: { name: 'review/tier-1', color: '0E8A16', description: 'Trivial — auto-merge candidate once CI passes' },
-              2: { name: 'review/tier-2', color: '1D76DB', description: 'Low risk — AI review + quick human skim' },
-              3: { name: 'review/tier-3', color: 'E4E669', description: 'Standard — full human review required' },
-              4: { name: 'review/tier-4', color: 'B60205', description: 'Critical — deep review + domain expert sign-off' },
-            };
-
-            const TIER_INFO = {
-              1: {
-                emoji: '🟢',
-                headline: 'Tier 1 — Trivial',
-                detail: 'Docs, images, lock files, or a dependency bump. No functional code changes detected.',
-                process: 'Auto-merge once CI passes. No human review required.',
-                sla: 'Resolves automatically.',
-              },
-              2: {
-                emoji: '🔵',
-                headline: 'Tier 2 — Low Risk',
-                detail: 'Small, isolated change with no API route or data model modifications.',
-                process: 'AI review + quick human skim (target: 5–15 min). Reviewer validates AI assessment and checks for domain-specific concerns.',
-                sla: 'Resolve within 4 business hours.',
-              },
-              3: {
-                emoji: '🟡',
-                headline: 'Tier 3 — Standard',
-                detail: 'Introduces new logic, modifies core functionality, or touches areas with non-trivial risk.',
-                process: 'Full human review — logic, architecture, edge cases.',
-                sla: 'First-pass feedback within 1 business day.',
-              },
-              4: {
-                emoji: '🔴',
-                headline: 'Tier 4 — Critical',
-                detail: 'Touches auth, data models, config, tasks, OTel pipeline, ClickHouse, or CI/CD.',
-                process: 'Deep review from a domain expert. Synchronous walkthrough may be required.',
-                sla: 'Schedule synchronous review within 2 business days.',
-              },
-            };
-
-            // ── Ensure tier labels exist (once, before the loop) ─────────────
-            const repoLabels = await github.paginate(
-              github.rest.issues.listLabelsForRepo,
-              { owner, repo, per_page: 100 }
-            );
-            const repoLabelNames = new Set(repoLabels.map(l => l.name));
-            for (const label of Object.values(TIER_LABELS)) {
-              if (!repoLabelNames.has(label.name)) {
-                await github.rest.issues.createLabel({ owner, repo, ...label });
-                repoLabelNames.add(label.name);
-              }
-            }
-
-            // ── Classify a single PR ─────────────────────────────────────────
-            async function classifyPR(prNumber) {
-              // Fetch changed files
-              const filesRes = await github.paginate(
-                github.rest.pulls.listFiles,
-                { owner, repo, pull_number: prNumber, per_page: 100 }
-              );
-              const files = filesRes.map(f => f.filename);
-              const TEST_FILE_PATTERNS = [
-                /\/__tests__\//,
-                /\.test\.[jt]sx?$/,
-                /\.spec\.[jt]sx?$/,
-                /^packages\/app\/tests\//,
-              ];
-              const isTestFile = f => TEST_FILE_PATTERNS.some(p => p.test(f));
-              const nonTestFiles = filesRes.filter(f => !isTestFile(f.filename));
-              const testLines = filesRes.filter(f => isTestFile(f.filename)).reduce((sum, f) => sum + f.additions + f.deletions, 0);
-              const linesChanged = nonTestFiles.reduce((sum, f) => sum + f.additions + f.deletions, 0);
-
-              // Fetch PR metadata
-              const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number: prNumber });
-              const author = pr.user.login;
-              const branchName = pr.head.ref;
-
-              // Skip drafts when running in bulk mode
-              if (pr.draft) {
-                console.log(`Skipping PR #${prNumber}: draft`);
-                return;
-              }
-
-              // Check for manual tier override — if a human last applied the label, respect it
-              const { data: currentLabels } = await github.rest.issues.listLabelsOnIssue({ owner, repo, issue_number: prNumber });
-              const existingTierLabel = currentLabels.find(l => l.name.startsWith('review/tier-'));
-              if (existingTierLabel) {
-                const events = await github.paginate(
-                  github.rest.issues.listEvents,
-                  { owner, repo, issue_number: prNumber, per_page: 100 }
-                );
-                const lastLabelEvent = events
-                  .filter(e => e.event === 'labeled' && e.label?.name === existingTierLabel.name)
-                  .pop();
-                if (lastLabelEvent && lastLabelEvent.actor.type !== 'Bot') {
-                  console.log(`PR #${prNumber}: tier manually set to ${existingTierLabel.name} by ${lastLabelEvent.actor.login} — skipping`);
-                  return;
-                }
-              }
-
-              // Classify
-              const isTier4 = files.some(f => TIER4_PATTERNS.some(p => p.test(f)));
-              const isTrivialAuthor = BOT_AUTHORS.includes(author);
-              const allFilesTrivial = files.length > 0 && files.every(f => TIER1_PATTERNS.some(p => p.test(f)));
-              const isTier1 = isTrivialAuthor || allFilesTrivial;
-              const isAgentBranch = AGENT_BRANCH_PREFIXES.some(p => branchName.startsWith(p));
-              const touchesApiModels = files.some(f =>
-                f.startsWith('packages/api/src/models/') || f.startsWith('packages/api/src/routers/')
-              );
-              const isSmallDiff = linesChanged < 100;
-              // Agent branches are bumped to Tier 3 regardless of size to ensure human review
-              const isTier2 = !isTier4 && !isTier1 && isSmallDiff && !touchesApiModels && !isAgentBranch;
-
-              let tier;
-              if (isTier4) tier = 4;
-              else if (isTier1) tier = 1;
-              else if (isTier2) tier = 2;
-              else tier = 3;
-
-              // Escalate very large non-critical PRs to Tier 4. Agent branches use a lower
-              // threshold (400 lines) since they warrant deeper scrutiny. Human-authored PRs
-              // are only escalated for truly massive diffs (1000+ lines); Tier 3 already
-              // requires full human review, so smaller large PRs don't need the extra urgency.
-              const sizeThreshold = isAgentBranch ? 400 : 1000;
-              if (tier === 3 && linesChanged > sizeThreshold) tier = 4;
-
-              // Apply label
-              for (const existing of currentLabels) {
-                if (existing.name.startsWith('review/tier-') && existing.name !== TIER_LABELS[tier].name) {
-                  await github.rest.issues.removeLabel({ owner, repo, issue_number: prNumber, name: existing.name });
-                }
-              }
-              if (!currentLabels.find(l => l.name === TIER_LABELS[tier].name)) {
-                await github.rest.issues.addLabels({ owner, repo, issue_number: prNumber, labels: [TIER_LABELS[tier].name] });
-              }
-
-              // Build comment body
-              const info = TIER_INFO[tier];
-
-              // Primary triggers — what actually determined (or escalated) the tier
-              const triggers = [];
-              const criticalFiles = files.filter(f => TIER4_PATTERNS.some(p => p.test(f)));
-              if (criticalFiles.length > 0) {
-                triggers.push(`**Critical-path files** (${criticalFiles.length}):\n${criticalFiles.map(f => `    - \`${f}\``).join('\n')}`);
-              }
-              if (tier === 4 && linesChanged > sizeThreshold && criticalFiles.length === 0) {
-                triggers.push(`**Large diff**: ${linesChanged} lines changed (threshold: ${sizeThreshold})`);
-              }
-              if (isTrivialAuthor) triggers.push(`**Bot author**: \`${author}\``);
-              if (allFilesTrivial && !isTrivialAuthor) triggers.push('**All files are docs / images / lock files**');
-              // Agent branch prevents Tier 2 — it's a cause for Tier 3, not just context
-              if (isAgentBranch && tier <= 3) triggers.push(`**Agent-generated branch** (\`${branchName}\`) — bumped to Tier 3 for mandatory human review`);
-              // Catch-all for Tier 3 PRs that don't match any specific trigger above
-              if (triggers.length === 0 && tier === 3) triggers.push('**Standard feature/fix** — introduces new logic or modifies core functionality');
-
-              // Informational signals — didn't drive the tier by themselves
-              const contextSignals = [];
-              if (isAgentBranch && tier === 4) contextSignals.push(`agent branch (\`${branchName}\`)`);
-              if (touchesApiModels && criticalFiles.length === 0) contextSignals.push('touches API routes or data models');
-              if (linesChanged > sizeThreshold && criticalFiles.length > 0) contextSignals.push(`large diff (${linesChanged} lines)`);
-
-              const triggerSection = triggers.length > 0
-                ? `\n**Why this tier:**\n${triggers.map(t => `- ${t}`).join('\n')}`
-                : '';
-              const contextSection = contextSignals.length > 0
-                ? `\n**Additional context:** ${contextSignals.join(', ')}`
-                : '';
-
-              const body = [
-                '<!-- pr-triage -->',
-                `## ${info.emoji} ${info.headline}`,
-                '',
-                info.detail,
-                triggerSection,
-                contextSection,
-                '',
-                `**Review process**: ${info.process}`,
-                `**SLA**: ${info.sla}`,
-                '',
-                `<details><summary>Stats</summary>`,
-                '',
-                `- Files changed: ${files.length}`,
-                `- Lines changed: ${linesChanged}${testLines > 0 ? ` (+ ${testLines} in test files, excluded from tier calculation)` : ''}`,
-                `- Branch: \`${branchName}\``,
-                `- Author: ${author}`,
-                '',
-                '</details>',
-                '',
-                `> To override this classification, remove the \`${TIER_LABELS[tier].name}\` label and apply a different \`review/tier-*\` label. Manual overrides are preserved on subsequent pushes.`,
-              ].join('\n');
-
-              // Post or update the single triage comment
-              const comments = await github.paginate(
-                github.rest.issues.listComments,
-                { owner, repo, issue_number: prNumber, per_page: 100 }
-              );
-              const existing = comments.find(c => c.user.login === 'github-actions[bot]' && c.body.includes('<!-- pr-triage -->'));
-              if (existing) {
-                await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body });
-              } else {
-                await github.rest.issues.createComment({ owner, repo, issue_number: prNumber, body });
-              }
-
-              console.log(`PR #${prNumber}: Tier ${tier} (${linesChanged} lines, ${files.length} files)`);
-            }
-
-            // ── Process all target PRs ───────────────────────────────────────
-            for (const prNumber of prNumbers) {
-              try {
-                await classifyPR(prNumber);
-              } catch (err) {
-                console.error(`PR #${prNumber}: classification failed — ${err.message}`);
-              }
-            }

Makefile

@@ -187,6 +187,10 @@ dev-unit:
 ci-unit:
 	npx nx run-many -t ci:unit
 
+.PHONY: ci-triage
+ci-triage:
+	node --test .github/scripts/__tests__/pr-triage-classify.test.js
+
 # ---------------------------------------------------------------------------
 # E2E tests — port isolation is handled by scripts/test-e2e.sh
 # ---------------------------------------------------------------------------

knip.json

@@ -27,7 +27,7 @@
       "project": ["src/**/*.ts"]
     }
   },
-  "ignore": ["scripts/dev-portal/**"],
+  "ignore": ["scripts/dev-portal/**", ".github/scripts/**"],
   "ignoreBinaries": ["make", "migrate", "playwright"],
   "ignoreDependencies": [
     "@dotenvx/dotenvx",