diff --git a/.github/scripts/__tests__/pr-triage-classify.test.js b/.github/scripts/__tests__/pr-triage-classify.test.js
new file mode 100644
index 00000000..8b03d3af
--- /dev/null
+++ b/.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(''));
+ });
+
+ 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'));
+ });
+});
diff --git a/.github/scripts/pr-triage-classify.js b/.github/scripts/pr-triage-classify.js
new file mode 100644
index 00000000..5d501901
--- /dev/null
+++ b/.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 [
+ '',
+ `## ${info.emoji} ${info.headline}`,
+ '',
+ info.detail,
+ triggerSection,
+ contextSection,
+ '',
+ `**Review process**: ${info.process}`,
+ `**SLA**: ${info.sla}`,
+ '',
+ 'Stats
',
+ '',
+ `- Production files changed: ${prodFiles.length}`,
+ `- Production lines changed: ${prodLines}${testLines > 0 ? ` (+ ${testLines} in test files, excluded from tier calculation)` : ''}`,
+ `- Branch: \`${branchName}\``,
+ `- Author: ${author}`,
+ '',
+ 'Stats
`,
- '',
- `- Files changed: ${files.length}`,
- `- Lines changed: ${linesChanged}${testLines > 0 ? ` (+ ${testLines} in test files, excluded from tier calculation)` : ''}`,
- `- Branch: \`${branchName}\``,
- `- Author: ${author}`,
- '',
- '