diff --git a/docs/release-integrity/TASKS.md b/docs/release-integrity/TASKS.md
index 47341cc8..a77c7350 100644
--- a/docs/release-integrity/TASKS.md
+++ b/docs/release-integrity/TASKS.md
@@ -22,7 +22,7 @@
 | RI-1-002 | done        | RI-N1 negative control: checked-in tests proving a broken mandatory check blocks every publish step and that DAG edges cannot be bypassed                                                                                                                                        | #1275 | pi-glm-5.3 | mosaicstack/stack | test/ri-050-publish-gate-negative | RI-1-001                                                   | 12K      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
 | RI-2-001 | done        | RI-N2 (Forge): remove stub-executor false success; `--simulate` typed `simulated` results that satisfy nothing; literal-`true` gates and echo-review replaced with real gates or typed waiting-for-authority                                                                     | #1275 | pi-glm-5.3 | mosaicstack/stack | fix/ri-050-forge-fail-closed      | RI-0-001                                                   | 20K      | Independent review APPROVED 2026-08-17 (Gitea review 172 on PR #1278, head 99b8f6ea; reviewing seat fargo — recorded under shared host principal mos-dt-0, provenance correction posted by fred; wrapper gap filed by fred). Executed at head: forge tests 116/116, lint green, typecheck green after building macp dist (minimal-install artifact, not a defect), workspace typecheck 45/45, no external type consumers of the changed interfaces. CI red = known lane-wide fleet-test failure only, carries no information about this change (fred, log-content analysis, pipelines 2456-2458). Non-blocking finding: README L141-143 + skills/mosaic-forge/SKILL.md document bare forge run/resume, which now fails closed — fast-follow docs touch. Merge queued behind #1270. UPDATE 2026-08-18: #1270 merged; CI GREEN at head 4917df1f via serialized retry (pipeline 2477) - root cause of prior reds was CI-agent contention (web SPA timeouts under concurrent pipelines), superseding the fleet-test-failure theory. |
 | RI-2-002 | done        | RI-N2 (MACP): gate runner fails closed on empty commands, stub executors, and unimplemented CI-provider gates unless explicit simulate; typed capability failures                                                                                                                | #1275 | pi-glm-5.3 | mosaicstack/stack | fix/ri-050-macp-fail-closed       | RI-0-001                                                   | 15K      | PR #1293 (head 2097379e): CI green (pipeline 2465), independent review APPROVED (Gitea review 173, jarvis seat, 2026-08-17) - macp 109/109 verified at head. Merge queued behind #1276/#1277/#1278.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
-| RI-3-001 | in-progress | RI-N4: complete probe inventory mapping every TS and shell quality-rail check to one canonical check with disposition (preserve/strengthen/retire, each named)                                                                                                                   | #1275 | pi-glm-5.3 | mosaicstack/stack | docs/ri-050-qr-probe-inventory    | RI-0-001                                                   | 12K      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
+| RI-3-001 | done        | RI-N4: complete probe inventory mapping every TS and shell quality-rail check to one canonical check with disposition (preserve/strengthen/retire, each named)                                                                                                                   | #1275 | pi-glm-5.3 | mosaicstack/stack | docs/ri-050-qr-probe-inventory    | RI-0-001                                                   | 12K      | PR #1302 (head e06a47fac591): CI green (2484), independent review APPROVED (Gitea review 187, fargo seat, 2026-08-18) — 54 rows / 21 canonical checks / dispositions 43-2-9-0 verified by row-count and code spot-checks. Merged by fargo at pinned head.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | RI-3-002 | not-started | RI-N4: TS evaluator absorbs effective shell probes; typed results (passed/failed/blocked/error/not-applicable) with versioned digested check definitions; shell commands become thin adapters; contract/parity/negative-control tests                                            | #1275 | pi-glm-5.3 | mosaicstack/stack | feat/ri-050-qr-evaluator          | RI-3-001                                                   | 30K      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
 | RI-4-001 | in-progress | RI-N3: one PRD application service — `mission --plan` persists mission↔PRD linkage (ids/versions/selected requirements); `mosaic prdy` routes through the service or becomes a named import/export adapter; Markdown is a labeled generated view; explicit conflict-aware import | #1275 | pi-glm-5.3 | mosaicstack/stack | feat/ri-050-prd-authority         | RI-0-001                                                   | 35K      | PR #1294 (head 8d258e1d): CI green (pipeline 2466), independent review APPROVED (Gitea review 174, jarvis seat, 2026-08-17) - prdy 20/20 + command specs 9/9 at head. Merge queued behind #1276/#1277/#1278.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
 | RI-5-001 | done        | RI-N5: typed freshness states (current/stale/partial/unknown/unavailable); no failed-fetch-renders-empty; stale derived verdicts → unknown; mutations disabled when stale; failure-matrix tests                                                                                  | #1275 | pi-glm-5.3 | mosaicstack/stack | feat/ri-050-web-stale-safety      | RI-0-001                                                   | 25K      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
diff --git a/packages/quality-rails/README.md b/packages/quality-rails/README.md
new file mode 100644
index 00000000..ba82ad3a
--- /dev/null
+++ b/packages/quality-rails/README.md
@@ -0,0 +1,63 @@
+# @mosaicstack/quality-rails
+
+Quality-rails scaffolding and — since RI-3-002 (RI-N4) — the **typed
+quality-rails evaluator**: the single authoritative producer of check verdicts
+for the checks it owns.
+
+## Evaluator (RI-N4)
+
+Every verdict is typed and fail-closed:
+
+```
+{ status: 'passed' | 'failed' | 'blocked' | 'error' | 'not-applicable',
+  checkId, checkVersion, subject, reason }
+```
+
+Missing implementations, missing inputs, unknown check ids, process errors,
+timeouts, and malformed probe output can never become `passed` or an
+unqualified skip — they surface as `blocked`/`error` with a reason (vocabulary
+mirrors MACP's `GateStatus` discipline).
+
+- Check definitions live as **data** with a version and a sha256 content
+  digest (`definitionDigest`); every recorded verdict names the definition
+  version that produced it.
+- Check sets are selected **per subject kind** (`node`, `python`, `rust`,
+  `monorepo`, `unknown`) via the versioned, digested check-set policy — this
+  repository (a `monorepo` subject) does not share the node template's file
+  list.
+- Shell probes stay **thin adapters**: the TS evaluator invokes them and owns
+  the verdict parsing (e.g. QC-20's planted-commit probe).
+
+### Owned checks
+
+| check id                    | canonical check | mechanism                                                              |
+| --------------------------- | --------------- | ---------------------------------------------------------------------- |
+| `qc-19-rails-files-present` | QC-19           | typed absorption of the former presence-only `check`/`doctor` loop     |
+| `qc-20-enforcement-verify`  | QC-20           | thin shell adapter (framework `verify.sh`); verdict parsing owned here |
+
+The canonical check ids QC-1..QC-21 and their dispositions are defined in
+`docs/release-integrity/probe-inventory.md` (the RI-3-001 inventory — the
+evaluator's input, not its output).
+
+### Usage
+
+```sh
+# CLI (same typed report as the programmatic API)
+node dist/cli.js quality-rails evaluate --project <path> [--probe-path <verify.sh>] [--json]
+node dist/cli.js quality-rails check --project <path> [--json]   # QC-19 only, fail-closed exit
+```
+
+```ts
+import { evaluateSubject } from '@mosaicstack/quality-rails';
+
+const report = await evaluateSubject({ subjectPath: '/path/to/project' });
+// report.state: 'passed' | 'failed' | 'blocked' | 'error'
+```
+
+`pnpm verify:release` invokes this evaluator as its `quality-rails` stage
+(canonical-only stage, QC-19 on the monorepo subject).
+
+## Scaffolding (pre-existing)
+
+`init` scaffolds rails files per detected kind/profile; `doctor` is advisory
+and reports typed states.
diff --git a/packages/quality-rails/src/cli-evaluate.spec.ts b/packages/quality-rails/src/cli-evaluate.spec.ts
new file mode 100644
index 00000000..4bee2b2a
--- /dev/null
+++ b/packages/quality-rails/src/cli-evaluate.spec.ts
@@ -0,0 +1,194 @@
+import { mkdir, mkdtemp, writeFile, chmod } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { createQualityRailsCli } from './cli.js';
+import { QC_19_RAILS_FILES_PRESENT } from './evaluator/definitions.js';
+import { evaluateSubject } from './evaluator/runner.js';
+import type { EvaluationReport } from './evaluator/types.js';
+
+// CLI ↔ programmatic contract (RI-3-002): the same subject must produce the
+// same typed verdicts through every entry point the card adds — the
+// `evaluate`/`check` CLI surfaces and the `evaluateSubject` API.
+
+async function makeTempDir(): Promise<string> {
+  return mkdtemp(join(tmpdir(), 'qr-cli-'));
+}
+
+async function scaffoldNodeFixture(skip: string[] = []): Promise<string> {
+  const dir = await makeTempDir();
+  await writeFile(join(dir, 'package.json'), '{}\n', 'utf8');
+  for (const relativePath of [
+    '.eslintrc',
+    'biome.json',
+    '.githooks/pre-commit',
+    'PR-CHECKLIST.md',
+  ]) {
+    if (skip.includes(relativePath)) continue;
+    await mkdir(join(dir, relativePath, '..'), { recursive: true });
+    await writeFile(join(dir, relativePath), 'fixture\n', 'utf8');
+  }
+  return dir;
+}
+
+async function makePassingProbe(dir: string): Promise<string> {
+  const scriptPath = join(dir, 'probe-pass.sh');
+  await writeFile(
+    scriptPath,
+    [
+      '#!/bin/bash',
+      'echo "✅ PASS: Type errors blocked"',
+      'echo "✅ PASS: Lint errors blocked"',
+      'echo "Verification Summary"',
+      'exit 0',
+    ].join('\n') + '\n',
+    'utf8',
+  );
+  await chmod(scriptPath, 0o755);
+  return scriptPath;
+}
+
+describe('CLI entry points vs the programmatic evaluator', () => {
+  let logSpy: ReturnType<typeof vi.spyOn>;
+  let previousExitCode: string | number | undefined;
+
+  beforeEach(() => {
+    logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    previousExitCode = process.exitCode ?? undefined;
+  });
+
+  afterEach(() => {
+    logSpy.mockRestore();
+    process.exitCode = previousExitCode;
+  });
+
+  it('evaluate --json produces the SAME typed report as evaluateSubject (full check set + probe)', async () => {
+    const dir = await scaffoldNodeFixture();
+    const probePath = await makePassingProbe(dir);
+
+    const programmatic = await evaluateSubject({
+      subjectPath: dir,
+      inputs: { 'qc-20-enforcement-verify': { probePath } },
+    });
+
+    const program = createQualityRailsCli();
+    await program.parseAsync([
+      'node',
+      'cli.js',
+      'quality-rails',
+      'evaluate',
+      '--project',
+      dir,
+      '--probe-path',
+      probePath,
+      '--json',
+    ]);
+
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    const cliReport = JSON.parse(printed) as EvaluationReport;
+    expect(cliReport).toEqual(programmatic);
+    expect(cliReport.state).toBe('passed');
+    expect(process.exitCode).toBe(0);
+  });
+
+  it('check --json produces the SAME QC-19 verdict as evaluateSubject (absorbed loop)', async () => {
+    const dir = await scaffoldNodeFixture(['biome.json', '.githooks/pre-commit']);
+
+    const programmatic = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_19_RAILS_FILES_PRESENT.id],
+    });
+    expect(programmatic.state).toBe('failed');
+
+    const program = createQualityRailsCli();
+    await program.parseAsync([
+      'node',
+      'cli.js',
+      'quality-rails',
+      'check',
+      '--project',
+      dir,
+      '--json',
+    ]);
+
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    const cliReport = JSON.parse(printed) as EvaluationReport;
+    expect(cliReport).toEqual(programmatic);
+    expect(process.exitCode).toBe(1);
+  });
+
+  it('check on a complete subject exits 0 with a passed verdict', async () => {
+    const dir = await scaffoldNodeFixture();
+    const program = createQualityRailsCli();
+    await program.parseAsync([
+      'node',
+      'cli.js',
+      'quality-rails',
+      'check',
+      '--project',
+      dir,
+      '--json',
+    ]);
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    const cliReport = JSON.parse(printed) as EvaluationReport;
+    expect(cliReport.state).toBe('passed');
+    expect(process.exitCode).toBe(0);
+  });
+
+  it('evaluate with an unknown check id exits 1 and reports error, never passed', async () => {
+    const dir = await scaffoldNodeFixture();
+    const program = createQualityRailsCli();
+    await program.parseAsync([
+      'node',
+      'cli.js',
+      'quality-rails',
+      'evaluate',
+      '--project',
+      dir,
+      '--check',
+      'qc-99-bogus',
+      '--json',
+    ]);
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    const cliReport = JSON.parse(printed) as EvaluationReport;
+    expect(cliReport.results).toHaveLength(1);
+    const first = cliReport.results[0];
+    expect(first?.status).toBe('error');
+    expect(first?.reason).toContain('unknown check id');
+    expect(process.exitCode).toBe(1);
+  });
+
+  it('evaluate on a scaffold subject without --probe-path stays fail-closed (blocked, exit 1)', async () => {
+    const dir = await scaffoldNodeFixture();
+    const program = createQualityRailsCli();
+    await program.parseAsync([
+      'node',
+      'cli.js',
+      'quality-rails',
+      'evaluate',
+      '--project',
+      dir,
+      '--json',
+    ]);
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    const cliReport = JSON.parse(printed) as EvaluationReport;
+    const qc20 = cliReport.results.find((r) => r.checkId === 'qc-20-enforcement-verify');
+    expect(qc20).toBeDefined();
+    expect(qc20?.status).toBe('blocked');
+    expect(qc20?.reason).toContain('probePath');
+    expect(cliReport.state).toBe('blocked');
+    expect(process.exitCode).toBe(1);
+  });
+
+  it('doctor stays advisory (no nonzero exit) but reports TYPED states, including blocked', async () => {
+    const dir = await scaffoldNodeFixture();
+    const program = createQualityRailsCli();
+    await program.parseAsync(['node', 'cli.js', 'quality-rails', 'doctor', '--project', dir]);
+
+    const printed = logSpy.mock.calls.map((call) => String(call[0])).join('\n');
+    expect(printed).toContain('blocked: qc-20-enforcement-verify');
+    expect(process.exitCode ?? 0).toBe(0);
+  });
+});
diff --git a/packages/quality-rails/src/cli.ts b/packages/quality-rails/src/cli.ts
index 0c5908f3..2ab38b72 100644
--- a/packages/quality-rails/src/cli.ts
+++ b/packages/quality-rails/src/cli.ts
@@ -1,5 +1,3 @@
-import { constants } from 'node:fs';
-import { access } from 'node:fs/promises';
 import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 
@@ -8,18 +6,12 @@ import { Command } from 'commander';
 import { detectProjectKind } from './detect.js';
 import { scaffoldQualityRails } from './scaffolder.js';
 import type { ProjectKind, QualityProfile, RailsConfig } from './types.js';
+import { QC_19_RAILS_FILES_PRESENT } from './evaluator/definitions.js';
+import { evaluateSubject } from './evaluator/runner.js';
+import type { EvaluationReport } from './evaluator/types.js';
 
 const VALID_PROFILES: readonly QualityProfile[] = ['strict', 'standard', 'minimal'];
 
-async function fileExists(filePath: string): Promise<boolean> {
-  try {
-    await access(filePath, constants.F_OK);
-    return true;
-  } catch {
-    return false;
-  }
-}
-
 function parseProfile(rawProfile: string): QualityProfile {
   if (VALID_PROFILES.includes(rawProfile as QualityProfile)) {
     return rawProfile as QualityProfile;
@@ -59,22 +51,6 @@ function defaultFormatters(kind: ProjectKind): string[] {
   return [];
 }
 
-function expectedFilesForKind(kind: ProjectKind): string[] {
-  if (kind === 'node') {
-    return ['.eslintrc', 'biome.json', '.githooks/pre-commit', 'PR-CHECKLIST.md'];
-  }
-
-  if (kind === 'python') {
-    return ['pyproject.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'];
-  }
-
-  if (kind === 'rust') {
-    return ['rustfmt.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'];
-  }
-
-  return ['.githooks/pre-commit', 'PR-CHECKLIST.md'];
-}
-
 function printScaffoldResult(
   config: RailsConfig,
   filesWritten: string[],
@@ -106,6 +82,20 @@ function printScaffoldResult(
   }
 }
 
+function printEvaluationReport(report: EvaluationReport): void {
+  console.log(
+    `[quality-rails] evaluation for ${report.subject.path} (kind=${report.subject.kind}, check-set v${report.checkSetVersion})`,
+  );
+  for (const result of report.results) {
+    const reason = result.reason === undefined ? '' : ` — ${result.reason}`;
+    const digest = report.definitionDigests[result.checkId] ?? 'no digest';
+    console.log(
+      `  - ${result.status}: ${result.checkId} (v${result.checkVersion} [${digest}])${reason}`,
+    );
+  }
+  console.log(`[quality-rails] aggregate: ${report.state}`);
+}
+
 /**
  * Register quality-rails subcommands on an existing Commander program.
  * This avoids cross-package Commander version mismatches by using the
@@ -148,56 +138,93 @@ function buildQualityRailsCommand(qualityRails: Command): void {
       printScaffoldResult(config, result.filesWritten, result.warnings, result.commandsToRun);
     });
 
+  // `check` (QC-19) is ABSORBED by the RI-N4 evaluator: the presence loop
+  // that lived here is now the versioned, digested, typed check definition
+  // `qc-19-rails-files-present`. The CLI keeps its human surface (missing
+  // files listed, exit 1) and gains `--json` for the typed verdicts. Exit
+  // code is fail-closed: any non-green aggregate (failed/blocked/error) is 1.
   qualityRails
     .command('check')
     .requiredOption('--project <path>', 'Project path')
-    .action(async (options: { project: string }) => {
+    .option('--json', 'print the typed evaluation report as JSON')
+    .action(async (options: { project: string; json?: boolean }) => {
       const projectPath = resolve(options.project);
-      const kind = await detectProjectKind(projectPath);
-      const expected = expectedFilesForKind(kind);
-      const missing: string[] = [];
+      const report = await evaluateSubject({
+        subjectPath: projectPath,
+        checkIds: [QC_19_RAILS_FILES_PRESENT.id],
+      });
 
-      for (const relativePath of expected) {
-        const exists = await fileExists(resolve(projectPath, relativePath));
-        if (!exists) {
-          missing.push(relativePath);
-        }
+      if (options.json) {
+        console.log(JSON.stringify(report));
+      } else {
+        printEvaluationReport(report);
       }
 
-      if (missing.length > 0) {
-        console.error('[quality-rails] missing files:');
-        for (const relativePath of missing) {
-          console.error(`  - ${relativePath}`);
-        }
-        process.exitCode = 1;
-        return;
-      }
-
-      console.log(`[quality-rails] all expected files present for ${kind} project`);
+      process.exitCode = report.state === 'passed' ? 0 : 1;
     });
 
+  // `doctor` (QC-19) stays advisory (documented contract: a doctor that
+  // cannot fail), but now reports TYPED states — a blocked or failing rail is
+  // visible instead of silently printed as `ok`/`missing`.
   qualityRails
     .command('doctor')
     .requiredOption('--project <path>', 'Project path')
     .action(async (options: { project: string }) => {
       const projectPath = resolve(options.project);
-      const kind = await detectProjectKind(projectPath);
-      const expected = expectedFilesForKind(kind);
+      const report = await evaluateSubject({ subjectPath: projectPath });
 
       console.log(`[quality-rails] doctor for ${projectPath}`);
-      console.log(`detected project kind: ${kind}`);
-
-      for (const relativePath of expected) {
-        const exists = await fileExists(resolve(projectPath, relativePath));
-        console.log(`  - ${exists ? 'ok' : 'missing'}: ${relativePath}`);
+      console.log(`detected project kind: ${report.subject.kind}`);
+      for (const result of report.results) {
+        const reason = result.reason === undefined ? '' : ` — ${result.reason}`;
+        console.log(`  - ${result.status}: ${result.checkId}${reason}`);
       }
 
-      if (kind === 'unknown') {
+      if (report.subject.kind === 'unknown') {
         console.log(
           'recommendation: add package.json, pyproject.toml, or Cargo.toml for better defaults.',
         );
       }
     });
+
+  // `evaluate` is the canonical RI-N4 evaluator entry point: typed verdicts
+  // for the subject's full per-kind check set, same results as the
+  // programmatic API (evaluateSubject).
+  qualityRails
+    .command('evaluate')
+    .description('Run the typed quality-rails evaluator against a subject project')
+    .requiredOption('--project <path>', 'Project path')
+    .option('--check <id...>', 'restrict evaluation to these check ids')
+    .option(
+      '--probe-path <path>',
+      'path to the QC-20 behavioral probe script (framework verify.sh)',
+    )
+    .option('--json', 'print the typed evaluation report as JSON')
+    .action(
+      async (options: {
+        project: string;
+        check?: string[];
+        probePath?: string;
+        json?: boolean;
+      }) => {
+        const projectPath = resolve(options.project);
+        const report = await evaluateSubject({
+          subjectPath: projectPath,
+          checkIds: options.check,
+          inputs: options.probePath
+            ? { 'qc-20-enforcement-verify': { probePath: options.probePath } }
+            : undefined,
+        });
+
+        if (options.json) {
+          console.log(JSON.stringify(report));
+        } else {
+          printEvaluationReport(report);
+        }
+
+        process.exitCode = report.state === 'passed' ? 0 : 1;
+      },
+    );
 }
 
 export async function runQualityRailsCli(argv: string[] = process.argv): Promise<void> {
diff --git a/packages/quality-rails/src/evaluator/adapter.ts b/packages/quality-rails/src/evaluator/adapter.ts
new file mode 100644
index 00000000..a731c0bf
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/adapter.ts
@@ -0,0 +1,67 @@
+import { spawn } from 'node:child_process';
+import type { ChildProcess } from 'node:child_process';
+
+import type { AdapterOutcome, AdapterRequest, ProcessAdapter } from './types.js';
+
+/**
+ * Default thin process adapter (spawn-based). Runs a command to completion with
+ * a hard timeout and reports exit code + captured output — it owns NO verdict
+ * logic. Interpreting the outcome is always the check implementation's job.
+ */
+export function createSpawnProcessAdapter(): ProcessAdapter {
+  return {
+    run(request: AdapterRequest): Promise<AdapterOutcome> {
+      return new Promise((resolve) => {
+        let child: ChildProcess;
+        try {
+          child = spawn(request.file, request.args, {
+            cwd: request.cwd,
+            stdio: ['ignore', 'pipe', 'pipe'],
+          });
+        } catch (error) {
+          resolve({
+            ok: false,
+            kind: 'spawn-error',
+            message: error instanceof Error ? error.message : String(error),
+          });
+          return;
+        }
+
+        let stdout = '';
+        let stderr = '';
+        let settled = false;
+
+        const timer = setTimeout(() => {
+          if (settled) return;
+          settled = true;
+          child.kill('SIGKILL');
+          resolve({
+            ok: false,
+            kind: 'timeout',
+            message: `process timed out after ${request.timeoutMs}ms: ${request.file}`,
+          });
+        }, request.timeoutMs);
+
+        const settle = (outcome: AdapterOutcome): void => {
+          if (settled) return;
+          settled = true;
+          clearTimeout(timer);
+          resolve(outcome);
+        };
+
+        child.stdout?.on('data', (chunk: Buffer) => {
+          stdout += chunk.toString('utf8');
+        });
+        child.stderr?.on('data', (chunk: Buffer) => {
+          stderr += chunk.toString('utf8');
+        });
+        child.on('error', (error: Error) => {
+          settle({ ok: false, kind: 'spawn-error', message: error.message });
+        });
+        child.on('close', (code: number | null) => {
+          settle({ ok: true, exitCode: code, stdout, stderr });
+        });
+      });
+    },
+  };
+}
diff --git a/packages/quality-rails/src/evaluator/definitions.ts b/packages/quality-rails/src/evaluator/definitions.ts
new file mode 100644
index 00000000..796da0e2
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/definitions.ts
@@ -0,0 +1,258 @@
+import { constants } from 'node:fs';
+import { access } from 'node:fs/promises';
+import { isAbsolute, resolve } from 'node:path';
+
+import { digestOfPolicy, digestOfSpec } from './digest.js';
+import type {
+  CheckContext,
+  CheckDefinition,
+  CheckDefinitionSpec,
+  CheckOutcome,
+  CheckSetPolicy,
+  CheckSetPolicySpec,
+  SubjectKind,
+} from './types.js';
+
+// Check definitions for the RI-N4 evaluator (card RI-3-002). Each definition is
+// DATA with a version and a content digest (see digest.ts); the executable
+// half is attached via defineCheck. Check-set SELECTION is per subject kind
+// (probe-inventory gap 7): this monorepo does not match the node template's
+// file list, so the QC-19 definition carries a distinct file set for the
+// `monorepo` subject kind and the policy selects checks per kind.
+
+export function defineCheck(
+  spec: CheckDefinitionSpec,
+  evaluate: (ctx: CheckContext) => Promise<CheckOutcome>,
+): CheckDefinition {
+  return { ...spec, definitionDigest: digestOfSpec(spec), evaluate };
+}
+
+async function fileExists(filePath: string): Promise<boolean> {
+  try {
+    await access(filePath, constants.F_OK);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+// ─── QC-19: downstream rails presence ────────────────────────────────────────
+//
+// Typed absorption of the former presence-only `quality-rails check` loop in
+// cli.ts. The scaffold-kind file lists below are carried over VERBATIM so the
+// evaluator's typed verdicts are parity-equivalent with the presence loop on
+// the same fixture; the `monorepo` list is new (per-subject check sets).
+
+const qc19Spec: CheckDefinitionSpec = {
+  id: 'qc-19-rails-files-present',
+  version: '1.0.0',
+  canonicalCheck: 'QC-19',
+  description:
+    'The subject still carries its quality-rails files. Typed absorption of the former presence-only check loop; presence is necessary, not sufficient (RI-N4).',
+  appliesTo: ['node', 'python', 'rust', 'monorepo', 'unknown'],
+  params: {
+    expectedFilesByKind: {
+      node: ['.eslintrc', 'biome.json', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+      python: ['pyproject.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+      rust: ['rustfmt.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+      monorepo: [
+        '.husky/pre-commit',
+        '.husky/pre-push',
+        'eslint.config.mjs',
+        '.prettierrc',
+        '.lintstagedrc',
+      ],
+      unknown: ['.githooks/pre-commit', 'PR-CHECKLIST.md'],
+    },
+  },
+};
+
+async function evaluateQc19(ctx: CheckContext): Promise<CheckOutcome> {
+  const byKind = ctx.params['expectedFilesByKind'] as Record<string, readonly string[]> | undefined;
+  if (byKind === undefined) {
+    return { status: 'error', reason: 'definition params missing expectedFilesByKind' };
+  }
+  const expected = byKind[ctx.subject.kind];
+  if (expected === undefined) {
+    // Fail-closed: an undefined file set for a declared subject kind is a
+    // definition gap, never a green outcome.
+    return {
+      status: 'blocked',
+      reason: `no expected-file set defined for subject kind '${ctx.subject.kind}'`,
+    };
+  }
+
+  const missing: string[] = [];
+  for (const relativePath of expected) {
+    if (!(await fileExists(resolve(ctx.subject.path, relativePath)))) {
+      missing.push(relativePath);
+    }
+  }
+  if (missing.length > 0) {
+    return {
+      status: 'failed',
+      reason: `missing rails files (${ctx.subject.kind}): ${missing.join(', ')}`,
+    };
+  }
+  return { status: 'passed' };
+}
+
+// ─── QC-20: downstream enforcement verification (behavioral probe) ──────────
+//
+// The planted-commit behavioral probe (framework tools/quality/scripts/verify.sh)
+// stays a THIN SHELL ADAPTER: the TS evaluator invokes it and OWNS the verdict
+// parsing (RI-N4: grep-on-output verdict logic moves into the typed evaluator).
+// Probe contract (verify.sh): exit 0 ⇔ every sub-probe passed, exit 1 ⇔ at
+// least one sub-probe failed; sub-probe verdicts appear as `PASS:` / `FAIL:`
+// marker lines and the script always prints a `Verification Summary` section.
+// Any deviation from that contract (other exit codes, unparseable output,
+// missing probe, process failure, timeout) is `error`/`blocked` — never
+// `passed`.
+
+const qc20Spec: CheckDefinitionSpec = {
+  id: 'qc-20-enforcement-verify',
+  version: '1.0.0',
+  canonicalCheck: 'QC-20',
+  description:
+    'The behavioral planted-commit probe runs against the subject and every sub-probe blocks as intended. The shell probe is a thin adapter; verdict parsing is owned by this evaluator.',
+  appliesTo: ['node', 'python', 'rust', 'unknown'],
+  params: {
+    command: 'bash',
+    timeoutMs: 120_000,
+    passMarker: 'PASS:',
+    failMarker: 'FAIL:',
+    summaryMarker: 'Verification Summary',
+  },
+};
+
+function linesWith(text: string, marker: string): string[] {
+  return text
+    .split('\n')
+    .map((line) => line.trim())
+    .filter((line) => line.includes(marker));
+}
+
+async function evaluateQc20(ctx: CheckContext): Promise<CheckOutcome> {
+  const rawProbePath = ctx.inputs['probePath'];
+  if (typeof rawProbePath !== 'string' || rawProbePath.trim().length === 0) {
+    return {
+      status: 'blocked',
+      reason:
+        'missing input: probePath — the behavioral probe script must be provided (e.g. the framework verify.sh)',
+    };
+  }
+  const probePath = isAbsolute(rawProbePath)
+    ? rawProbePath
+    : resolve(ctx.subject.path, rawProbePath);
+  if (!(await fileExists(probePath))) {
+    return { status: 'blocked', reason: `probe script not found: ${probePath}` };
+  }
+
+  const command = typeof ctx.params['command'] === 'string' ? ctx.params['command'] : 'bash';
+  const timeoutMs = typeof ctx.params['timeoutMs'] === 'number' ? ctx.params['timeoutMs'] : 120_000;
+  const passMarker =
+    typeof ctx.params['passMarker'] === 'string' ? ctx.params['passMarker'] : 'PASS:';
+  const failMarker =
+    typeof ctx.params['failMarker'] === 'string' ? ctx.params['failMarker'] : 'FAIL:';
+  const summaryMarker =
+    typeof ctx.params['summaryMarker'] === 'string'
+      ? ctx.params['summaryMarker']
+      : 'Verification Summary';
+
+  const outcome = await ctx.adapter.run({
+    file: command,
+    args: [probePath],
+    cwd: ctx.subject.path,
+    timeoutMs,
+  });
+
+  if (!outcome.ok) {
+    // Process error or timeout: the probe never produced a trustworthy result.
+    return {
+      status: 'error',
+      reason: `probe process ${outcome.kind}: ${outcome.message}`,
+    };
+  }
+
+  const output = `${outcome.stdout}\n${outcome.stderr}`;
+  const failLines = linesWith(output, failMarker);
+  const passLines = linesWith(output, passMarker);
+
+  if (outcome.exitCode === 0) {
+    // A green exit must be corroborated by a parseable green transcript:
+    // at least one pass marker, no fail markers, and the summary section.
+    if (passLines.length > 0 && failLines.length === 0 && output.includes(summaryMarker)) {
+      return { status: 'passed' };
+    }
+    return {
+      status: 'error',
+      reason: `malformed probe output: exit 0 without a parseable pass transcript (${passLines.length} pass markers, ${failLines.length} fail markers, summary ${output.includes(summaryMarker) ? 'present' : 'absent'})`,
+    };
+  }
+
+  if (outcome.exitCode === 1) {
+    if (failLines.length === 0) {
+      return {
+        status: 'error',
+        reason: 'malformed probe output: exit 1 without parseable FAIL markers',
+      };
+    }
+    return {
+      status: 'failed',
+      reason: `enforcement probe reported ${failLines.length} failing sub-probe(s): ${failLines.join(' | ')}`,
+    };
+  }
+
+  return {
+    status: 'error',
+    reason: `probe exited with unexpected code ${String(outcome.exitCode)} — outcome not interpretable`,
+  };
+}
+
+// ─── Per-subject check-set policy ───────────────────────────────────────────
+//
+// Gap 7 of the probe inventory: check sets must be selected per subject, not
+// one global list. Downstream scaffold kinds get the presence check plus the
+// behavioral probe (QC-20 blocks until a probePath input is provided — an
+// unverified subject can never evaluate green). The monorepo subject is this
+// repository itself: its rails are the husky hooks + shared lint/format
+// configs, covered by QC-19; the downstream planted-commit probe does not
+// apply to it (this repo's own commit gates are QC-13/QC-14, outside this
+// evaluator's owned checks).
+
+const checkSetPolicySpec: CheckSetPolicySpec = {
+  version: '1.0.0',
+  byKind: {
+    node: ['qc-19-rails-files-present', 'qc-20-enforcement-verify'],
+    python: ['qc-19-rails-files-present', 'qc-20-enforcement-verify'],
+    rust: ['qc-19-rails-files-present', 'qc-20-enforcement-verify'],
+    unknown: ['qc-19-rails-files-present', 'qc-20-enforcement-verify'],
+    monorepo: ['qc-19-rails-files-present'],
+  },
+};
+
+export const CHECK_SET_POLICY: CheckSetPolicy = {
+  ...checkSetPolicySpec,
+  policyDigest: digestOfPolicy(checkSetPolicySpec),
+};
+
+export const QC_19_RAILS_FILES_PRESENT = defineCheck(qc19Spec, evaluateQc19);
+export const QC_20_ENFORCEMENT_VERIFY = defineCheck(qc20Spec, evaluateQc20);
+
+/** Built-in check definitions, keyed by id. */
+export function builtInDefinitions(): CheckDefinition[] {
+  return [QC_19_RAILS_FILES_PRESENT, QC_20_ENFORCEMENT_VERIFY];
+}
+
+export function checkSetForKind(
+  kind: SubjectKind,
+  policy: CheckSetPolicy = CHECK_SET_POLICY,
+): readonly string[] {
+  const selected = policy.byKind[kind];
+  if (selected === undefined) {
+    // Fail-closed selection: an unknown kind yields an EMPTY set only to the
+    // caller; the runner treats an empty result list as `blocked`, never green.
+    return [];
+  }
+  return selected;
+}
diff --git a/packages/quality-rails/src/evaluator/digest.ts b/packages/quality-rails/src/evaluator/digest.ts
new file mode 100644
index 00000000..dab0d9a6
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/digest.ts
@@ -0,0 +1,45 @@
+import { createHash } from 'node:crypto';
+
+import type { CheckDefinitionSpec, CheckSetPolicySpec } from './types.js';
+
+// Deterministic JSON: object keys sorted at every level so two specs with the
+// same content always produce the same bytes (and thus the same digest).
+export function canonicalJson(value: unknown): string {
+  if (value === null || typeof value !== 'object') {
+    return JSON.stringify(value);
+  }
+  if (Array.isArray(value)) {
+    return `[${value.map((entry) => canonicalJson(entry)).join(',')}]`;
+  }
+  const record = value as Record<string, unknown>;
+  const keys = Object.keys(record).sort();
+  return `{${keys.map((key) => `${JSON.stringify(key)}:${canonicalJson(record[key])}`).join(',')}}`;
+}
+
+/** sha256 over the canonical JSON of `value`. */
+export function digestContent(value: unknown): string {
+  return createHash('sha256').update(canonicalJson(value), 'utf8').digest('hex');
+}
+
+/**
+ * Content digest of a check definition: covers the declarative spec (id,
+ * version, canonical check, description, applicability, params) — everything a
+ * reviewer reasons about — while excluding the executable function object.
+ * Changing any covered field changes the digest, so a recorded digest always
+ * identifies exactly which definition content produced a verdict.
+ */
+export function digestOfSpec(spec: CheckDefinitionSpec): string {
+  return digestContent({
+    id: spec.id,
+    version: spec.version,
+    canonicalCheck: spec.canonicalCheck,
+    description: spec.description,
+    appliesTo: spec.appliesTo,
+    params: spec.params,
+  });
+}
+
+/** Content digest of the per-subject check-set policy. */
+export function digestOfPolicy(spec: CheckSetPolicySpec): string {
+  return digestContent(spec);
+}
diff --git a/packages/quality-rails/src/evaluator/evaluator.spec.ts b/packages/quality-rails/src/evaluator/evaluator.spec.ts
new file mode 100644
index 00000000..2ccb9a30
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/evaluator.spec.ts
@@ -0,0 +1,525 @@
+import { mkdtemp, mkdir, writeFile, chmod } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+import { describe, expect, it } from 'vitest';
+
+import { createSpawnProcessAdapter } from './adapter.js';
+import {
+  builtInDefinitions,
+  CHECK_SET_POLICY,
+  checkSetForKind,
+  defineCheck,
+  QC_19_RAILS_FILES_PRESENT,
+  QC_20_ENFORCEMENT_VERIFY,
+} from './definitions.js';
+import { digestOfSpec } from './digest.js';
+import { aggregateState, evaluateSubject } from './runner.js';
+import type {
+  AdapterOutcome,
+  CheckDefinitionSpec,
+  CheckResult,
+  EvaluationReport,
+  ProcessAdapter,
+} from './types.js';
+
+// ─── helpers ────────────────────────────────────────────────────────────────
+
+function firstResult(report: EvaluationReport): CheckResult {
+  const result = report.results[0];
+  if (result === undefined) {
+    throw new Error('expected the report to contain at least one result');
+  }
+  return result;
+}
+
+async function makeTempDir(): Promise<string> {
+  return mkdtemp(join(tmpdir(), 'qr-evaluator-'));
+}
+
+async function writeProbeScript(dir: string, name: string, body: string): Promise<string> {
+  const scriptPath = join(dir, name);
+  await writeFile(scriptPath, `${body}\n`, 'utf8');
+  await chmod(scriptPath, 0o755);
+  return scriptPath;
+}
+
+/** Adapter stub that always returns the given outcome (no real process). */
+function stubAdapter(outcome: AdapterOutcome): ProcessAdapter {
+  return {
+    run: async () => outcome,
+  };
+}
+
+// VERBATIM copy of the pre-absorption presence loop (former cli.ts
+// expectedFilesForKind + fileExists loop). This is the PARITY ORACLE: the
+// evaluator's typed QC-19 verdict must agree with what the absorbed check
+// concluded on the same fixture.
+const LEGACY_EXPECTED: Record<'node' | 'python' | 'rust' | 'unknown', string[]> = {
+  node: ['.eslintrc', 'biome.json', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+  python: ['pyproject.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+  rust: ['rustfmt.toml', '.githooks/pre-commit', 'PR-CHECKLIST.md'],
+  unknown: ['.githooks/pre-commit', 'PR-CHECKLIST.md'],
+};
+
+async function legacyPresenceLoop(projectPath: string, kind: keyof typeof LEGACY_EXPECTED) {
+  const missing: string[] = [];
+  for (const relativePath of LEGACY_EXPECTED[kind]) {
+    const fs = await import('node:fs/promises');
+    try {
+      await fs.access(join(projectPath, relativePath));
+    } catch {
+      missing.push(relativePath);
+    }
+  }
+  return missing;
+}
+
+async function scaffoldFixture(kind: keyof typeof LEGACY_EXPECTED, skip: string[] = []) {
+  const dir = await makeTempDir();
+  if (kind === 'node') {
+    await writeFile(join(dir, 'package.json'), '{}\n', 'utf8');
+  }
+  if (kind === 'python') {
+    await writeFile(join(dir, 'pyproject.toml'), '[project]\n', 'utf8');
+  }
+  if (kind === 'rust') {
+    await writeFile(join(dir, 'Cargo.toml'), '[package]\n', 'utf8');
+  }
+  for (const relativePath of LEGACY_EXPECTED[kind]) {
+    if (skip.includes(relativePath)) continue;
+    await mkdir(join(dir, relativePath, '..'), { recursive: true });
+    await writeFile(join(dir, relativePath), 'fixture\n', 'utf8');
+  }
+  return dir;
+}
+
+// ─── QC-19 parity: typed verdict == absorbed presence loop ──────────────────
+
+describe('QC-19 parity with the absorbed presence loop', () => {
+  const kinds: Array<keyof typeof LEGACY_EXPECTED> = ['node', 'python', 'rust', 'unknown'];
+
+  it.each(kinds)('positive fixture (%s): loop said ok ⇒ evaluator passed', async (kind) => {
+    const dir = await scaffoldFixture(kind);
+    const oracleMissing = await legacyPresenceLoop(dir, kind);
+    expect(oracleMissing).toEqual([]);
+
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_19_RAILS_FILES_PRESENT.id],
+    });
+    const result = report.results.find((r) => r.checkId === QC_19_RAILS_FILES_PRESENT.id);
+    expect(result?.status).toBe('passed');
+    expect(result?.reason).toBeUndefined();
+    expect(report.state).toBe('passed');
+  });
+
+  it.each(kinds)(
+    'negative fixture (%s): loop listed missing ⇒ evaluator failed with them',
+    async (kind) => {
+      const all = LEGACY_EXPECTED[kind];
+      const skip = all.slice(0, Math.max(1, all.length - 1)); // leave exactly 1 present
+      const dir = await scaffoldFixture(kind, skip);
+      const oracleMissing = await legacyPresenceLoop(dir, kind);
+      expect(oracleMissing.length).toBeGreaterThan(0);
+
+      const report = await evaluateSubject({
+        subjectPath: dir,
+        checkIds: [QC_19_RAILS_FILES_PRESENT.id],
+      });
+      const result = report.results.find((r) => r.checkId === QC_19_RAILS_FILES_PRESENT.id);
+      expect(result?.status).toBe('failed');
+      expect(report.state).toBe('failed');
+      for (const missingFile of oracleMissing) {
+        expect(result?.reason).toContain(missingFile);
+      }
+      // No false attribution: a present file must not be named in the reason.
+      const presentFile = all.find((file) => !skip.includes(file));
+      if (presentFile !== undefined) {
+        expect(result?.reason).not.toContain(` ${presentFile},`);
+      }
+    },
+  );
+});
+
+// ─── per-subject check sets (inventory gap 7) ────────────────────────────────
+
+describe('per-subject check sets', () => {
+  it('monorepo subject selects only QC-19 with the monorepo file set', async () => {
+    const dir = await makeTempDir();
+    await writeFile(join(dir, 'pnpm-workspace.yaml'), 'packages:\n  - packages/*\n', 'utf8');
+    for (const file of [
+      '.husky/pre-commit',
+      '.husky/pre-push',
+      'eslint.config.mjs',
+      '.prettierrc',
+      '.lintstagedrc',
+    ]) {
+      await mkdir(join(dir, file, '..'), { recursive: true });
+      await writeFile(join(dir, file), 'fixture\n', 'utf8');
+    }
+
+    const report = await evaluateSubject({ subjectPath: dir });
+    expect(report.subject.kind).toBe('monorepo');
+    expect(report.results.map((r) => r.checkId)).toEqual(['qc-19-rails-files-present']);
+    expect(report.state).toBe('passed');
+  });
+
+  it('a monorepo missing one of its rails files fails QC-19 (not the node list)', async () => {
+    const dir = await makeTempDir();
+    await writeFile(join(dir, 'pnpm-workspace.yaml'), 'packages:\n', 'utf8');
+    const report = await evaluateSubject({ subjectPath: dir });
+    const result = report.results.find((r) => r.checkId === QC_19_RAILS_FILES_PRESENT.id);
+    expect(result?.status).toBe('failed');
+    expect(result?.reason).toContain('.husky/pre-commit');
+    // The node-template list must NOT be applied to a monorepo subject.
+    expect(result?.reason).not.toContain('biome.json');
+  });
+
+  it('the policy selects the behavioral probe for scaffold kinds but not monorepo', () => {
+    expect(checkSetForKind('node')).toContain(QC_20_ENFORCEMENT_VERIFY.id);
+    expect(checkSetForKind('unknown')).toContain(QC_20_ENFORCEMENT_VERIFY.id);
+    expect(checkSetForKind('monorepo')).not.toContain(QC_20_ENFORCEMENT_VERIFY.id);
+    expect(CHECK_SET_POLICY.version).toBe('1.0.0');
+  });
+});
+
+// ─── negative controls (the point of the card) ───────────────────────────────
+
+describe('negative controls', () => {
+  it('unknown check id ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: ['qc-99-does-not-exist'],
+    });
+    expect(report.results).toHaveLength(1);
+    const result = firstResult(report);
+    expect(result.status).toBe('error');
+    expect(result.reason).toContain("unknown check id 'qc-99-does-not-exist'");
+    expect(result.status === 'passed').toBe(false);
+    expect(report.state).toBe('error');
+  });
+
+  it('missing subject (directory absent) ⇒ blocked for every check, never passed', async () => {
+    const report = await evaluateSubject({
+      subjectPath: join(tmpdir(), `qr-evaluator-absent-${Date.now()}`),
+    });
+    expect(report.results.length).toBeGreaterThan(0);
+    for (const result of report.results) {
+      expect(result.status).toBe('blocked');
+      expect(result.reason).toContain('subject directory does not exist');
+    }
+    expect(report.state).toBe('blocked');
+  });
+
+  it('QC-20 without probePath input ⇒ blocked, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+    });
+    const result = firstResult(report);
+    expect(result.status).toBe('blocked');
+    expect(result.reason).toContain('missing input: probePath');
+  });
+
+  it('QC-20 with a nonexistent probe script ⇒ blocked, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: join(dir, 'no-such-probe.sh') } },
+    });
+    expect(firstResult(report).status).toBe('blocked');
+    expect(firstResult(report).reason).toContain('probe script not found');
+  });
+
+  it('adapter process error (spawn failure) ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: join(dir, 'PR-CHECKLIST.md') } },
+      adapter: stubAdapter({ ok: false, kind: 'spawn-error', message: 'ENOENT bash' }),
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('probe process spawn-error');
+    expect(firstResult(report).status === 'passed').toBe(false);
+  });
+
+  it('adapter timeout ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: join(dir, 'PR-CHECKLIST.md') } },
+      adapter: stubAdapter({ ok: false, kind: 'timeout', message: 'timed out after 120000ms' }),
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('probe process timeout');
+  });
+
+  it('probe exit 1 with parseable FAIL markers ⇒ failed (interpretably red), never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(
+      dir,
+      'probe-fail.sh',
+      `echo "Test 1: ..."\necho "❌ FAIL: Type errors NOT blocked"\necho "Verification Summary"\nexit 1`,
+    );
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('failed');
+    expect(firstResult(report).reason).toContain('FAIL: Type errors NOT blocked');
+    expect(report.state).toBe('failed');
+  });
+
+  it('probe exit 1 WITHOUT parseable FAIL markers ⇒ malformed ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(dir, 'probe-mute.sh', `echo "nothing to see"\nexit 1`);
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('malformed probe output');
+  });
+
+  it('probe exit 0 without a parseable pass transcript ⇒ malformed ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(dir, 'probe-lie.sh', `echo "all good"\nexit 0`);
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('malformed probe output');
+    expect(firstResult(report).reason).toContain('exit 0');
+  });
+
+  it('probe exit 0 WITH fail markers ⇒ contradictory transcript ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(
+      dir,
+      'probe-contradict.sh',
+      `echo "✅ PASS: one"\necho "❌ FAIL: two"\necho "Verification Summary"\nexit 0`,
+    );
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('error');
+  });
+
+  it('probe unexpected exit code (7) ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(dir, 'probe-crash.sh', `echo "boom"\nexit 7`);
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('unexpected code 7');
+  });
+
+  it('check implementation throwing ⇒ error, never passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const spec: CheckDefinitionSpec = {
+      id: 'test-throws',
+      version: '1.0.0',
+      canonicalCheck: 'QC-TEST',
+      description: 'sabotage-shaped definition that always throws',
+      appliesTo: ['node'],
+      params: {},
+    };
+    const throwing = defineCheck(spec, async () => {
+      throw new Error('kaboom');
+    });
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: ['test-throws'],
+      definitions: [throwing],
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('kaboom');
+  });
+
+  it('non-passed verdict without a reason ⇒ upgraded to error, never an unqualified skip', async () => {
+    const dir = await scaffoldFixture('node');
+    const spec: CheckDefinitionSpec = {
+      id: 'test-silent-fail',
+      version: '1.0.0',
+      canonicalCheck: 'QC-TEST',
+      description: 'returns failed without a reason',
+      appliesTo: ['node'],
+      params: {},
+    };
+    const silent = defineCheck(spec, async () => ({ status: 'failed' }));
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: ['test-silent-fail'],
+      definitions: [silent],
+    });
+    expect(firstResult(report).status).toBe('error');
+    expect(firstResult(report).reason).toContain('without a reason');
+  });
+
+  it('empty result list aggregates to blocked, never passed', () => {
+    expect(aggregateState([])).toBe('blocked');
+  });
+});
+
+// ─── QC-20 parity: typed verdict == shell probe's own conclusion ────────────
+
+describe('QC-20 parity with the shell probe contract', () => {
+  it('green transcript (exit 0) ⇒ evaluator passed', async () => {
+    const dir = await scaffoldFixture('node');
+    const probe = await writeProbeScript(
+      dir,
+      'probe-pass.sh',
+      [
+        'echo "✅ PASS: Type errors blocked"',
+        'echo "✅ PASS: any types blocked"',
+        'echo "✅ PASS: Lint errors blocked"',
+        'echo "Verification Summary"',
+        'echo "✅ Passed: 3"',
+        'exit 0',
+      ].join('\n'),
+    );
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: probe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    expect(firstResult(report).status).toBe('passed');
+    expect(report.state).toBe('passed');
+  });
+
+  it('the REAL framework verify.sh on a non-git subject concludes failed (exit 1) ⇒ evaluator failed', async () => {
+    // Real-probe parity: verify.sh without a git repo cannot block planted
+    // commits, exits 1 with FAIL markers — the evaluator must record exactly
+    // `failed` with those markers, matching the probe's own conclusion.
+    const realProbe = fileURLToPath(
+      new URL('../../../mosaic/framework/tools/quality/scripts/verify.sh', import.meta.url),
+    );
+    const dir = await makeTempDir(); // not a git repository, no hooks
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_20_ENFORCEMENT_VERIFY.id],
+      inputs: { 'qc-20-enforcement-verify': { probePath: realProbe } },
+      adapter: createSpawnProcessAdapter(),
+    });
+    const result = firstResult(report);
+    expect(result.status).toBe('failed');
+    expect(result.reason).toMatch(/FAIL:/);
+    expect(report.state).toBe('failed');
+  });
+});
+
+// ─── version / digest discipline ─────────────────────────────────────────────
+
+describe('versioned, digested check definitions', () => {
+  it('every verdict records the definition version that produced it', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({ subjectPath: dir });
+    for (const result of report.results) {
+      expect(result.checkVersion).toBe('1.0.0');
+    }
+    expect(report.checkSetVersion).toBe(CHECK_SET_POLICY.version);
+  });
+
+  it('the report records each definition’s content digest', async () => {
+    const dir = await scaffoldFixture('node');
+    const report = await evaluateSubject({ subjectPath: dir });
+    expect(report.definitionDigests[QC_19_RAILS_FILES_PRESENT.id]).toBe(
+      QC_19_RAILS_FILES_PRESENT.definitionDigest,
+    );
+    expect(report.definitionDigests[QC_20_ENFORCEMENT_VERIFY.id]).toBe(
+      QC_20_ENFORCEMENT_VERIFY.definitionDigest,
+    );
+  });
+
+  it('digests are stable for identical content', () => {
+    const spec = QC_19_RAILS_FILES_PRESENT;
+    expect(digestOfSpec(spec)).toBe(digestOfSpec(spec));
+  });
+
+  it('changing a definition’s content changes its digest', () => {
+    const base = { ...QC_19_RAILS_FILES_PRESENT } as CheckDefinitionSpec;
+    const baseDigest = digestOfSpec(base);
+
+    const changedParams: CheckDefinitionSpec = {
+      ...base,
+      params: {
+        expectedFilesByKind: {
+          ...(base.params['expectedFilesByKind'] as Record<string, string[]>),
+          node: ['.eslintrc', 'biome.json', '.githooks/pre-commit', 'PR-CHECKLIST.md', 'NEW.md'],
+        },
+      },
+    };
+    expect(digestOfSpec(changedParams)).not.toBe(baseDigest);
+
+    const changedVersion: CheckDefinitionSpec = { ...base, version: '1.1.0' };
+    expect(digestOfSpec(changedVersion)).not.toBe(baseDigest);
+  });
+
+  it('a definition with changed content produces a different recorded digest and version', async () => {
+    const dir = await scaffoldFixture('node');
+    const modified = defineCheck(
+      { ...QC_19_RAILS_FILES_PRESENT, version: '2.0.0' } as unknown as CheckDefinitionSpec,
+      async () => ({ status: 'passed' }),
+    );
+    const report = await evaluateSubject({
+      subjectPath: dir,
+      checkIds: [QC_19_RAILS_FILES_PRESENT.id],
+      definitions: [
+        modified,
+        ...builtInDefinitions().filter((d) => d.id !== QC_19_RAILS_FILES_PRESENT.id),
+      ],
+    });
+    const result = firstResult(report);
+    expect(result.checkVersion).toBe('2.0.0');
+    expect(report.definitionDigests[QC_19_RAILS_FILES_PRESENT.id]).toBe(modified.definitionDigest);
+    expect(modified.definitionDigest).not.toBe(QC_19_RAILS_FILES_PRESENT.definitionDigest);
+  });
+});
+
+// ─── aggregate state ordering (MACP-style discipline) ───────────────────────
+
+describe('aggregate state precedence', () => {
+  const result = (status: 'passed' | 'failed' | 'blocked' | 'error') => ({
+    status,
+    checkId: 'x',
+    checkVersion: '1.0.0',
+    subject: '/tmp/x',
+  });
+
+  it('all passed (with not-applicable) ⇒ passed', () => {
+    expect(
+      aggregateState([
+        result('passed'),
+        { ...result('passed'), status: 'not-applicable' as const },
+      ]),
+    ).toBe('passed');
+  });
+
+  it('error outranks blocked and failed; blocked outranks failed', () => {
+    expect(aggregateState([result('blocked'), result('error')])).toBe('error');
+    expect(aggregateState([result('failed'), result('blocked')])).toBe('blocked');
+    expect(aggregateState([result('passed'), result('failed')])).toBe('failed');
+  });
+});
diff --git a/packages/quality-rails/src/evaluator/runner.ts b/packages/quality-rails/src/evaluator/runner.ts
new file mode 100644
index 00000000..71e8e11f
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/runner.ts
@@ -0,0 +1,183 @@
+import { constants } from 'node:fs';
+import { access, stat } from 'node:fs/promises';
+import { join, resolve } from 'node:path';
+
+import { createSpawnProcessAdapter } from './adapter.js';
+import { builtInDefinitions, CHECK_SET_POLICY, checkSetForKind } from './definitions.js';
+import type {
+  AggregateState,
+  CheckResult,
+  CheckStatus,
+  EvaluateOptions,
+  EvaluationReport,
+  ProcessAdapter,
+  Subject,
+  SubjectKind,
+} from './types.js';
+import { detectProjectKind } from '../detect.js';
+
+async function pathExists(targetPath: string): Promise<boolean> {
+  try {
+    await access(targetPath, constants.F_OK);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+async function isDirectory(targetPath: string): Promise<boolean> {
+  try {
+    return (await stat(targetPath)).isDirectory();
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Subject-kind detection for the evaluator. Extends the scaffold detection
+ * (detect.ts) with the `monorepo` kind: a pnpm workspace is this repository's
+ * own subject shape and carries a different rails file set (probe-inventory
+ * gap 7 — check sets are per subject, not one global file list).
+ */
+export async function detectSubjectKind(subjectPath: string): Promise<SubjectKind> {
+  if (await pathExists(join(subjectPath, 'pnpm-workspace.yaml'))) {
+    return 'monorepo';
+  }
+  const kind = await detectProjectKind(subjectPath);
+  return kind;
+}
+
+/**
+ * Aggregate state, MACP-style discipline: `passed` only when at least one
+ * check produced a verdict AND every verdict is `passed` or an explicitly
+ * qualified `not-applicable`. Precedence is fail-closed: error > blocked >
+ * failed > passed; an empty result list aggregates to `blocked`.
+ */
+export function aggregateState(results: readonly CheckResult[]): AggregateState {
+  if (results.length === 0) {
+    return 'blocked';
+  }
+  const has = (status: CheckStatus): boolean => results.some((result) => result.status === status);
+  if (has('error')) {
+    return 'error';
+  }
+  if (has('blocked')) {
+    return 'blocked';
+  }
+  if (has('failed')) {
+    return 'failed';
+  }
+  return 'passed';
+}
+
+function reasonFrom(error: unknown): string {
+  return error instanceof Error ? error.message : String(error);
+}
+
+/**
+ * Evaluate one subject against a set of checks, producing typed verdicts.
+ *
+ * Fail-closed invariants (RI-N4):
+ * - unknown check id            → `error` (never passed)
+ * - subject directory absent    → every verdict `blocked`
+ * - check implementation threw  → `error`
+ * - non-passed without a reason → `error` (no unqualified skips)
+ * - check not applicable        → `not-applicable` WITH a reason
+ */
+export async function evaluateSubject(options: EvaluateOptions): Promise<EvaluationReport> {
+  const subjectPath = resolve(options.subjectPath);
+  const subject: Subject = {
+    path: subjectPath,
+    kind: await detectSubjectKind(subjectPath),
+  };
+
+  const definitions = options.definitions ?? builtInDefinitions();
+  const byId = new Map(definitions.map((definition) => [definition.id, definition]));
+  const requested = options.checkIds ?? checkSetForKind(subject.kind);
+  const adapter: ProcessAdapter = options.adapter ?? createSpawnProcessAdapter();
+
+  const results: CheckResult[] = [];
+  const definitionDigests: Record<string, string> = {};
+
+  for (const checkId of requested) {
+    const definition = byId.get(checkId);
+    if (definition === undefined) {
+      const known = definitions.map((entry) => entry.id).join(', ');
+      results.push({
+        status: 'error',
+        checkId,
+        checkVersion: 'unknown',
+        subject: subjectPath,
+        reason: `unknown check id '${checkId}' — no registered definition (known: ${known})`,
+      });
+      continue;
+    }
+
+    definitionDigests[checkId] = definition.definitionDigest;
+
+    if (!(await isDirectory(subjectPath))) {
+      results.push({
+        status: 'blocked',
+        checkId,
+        checkVersion: definition.version,
+        subject: subjectPath,
+        reason: `subject directory does not exist: ${subjectPath}`,
+      });
+      continue;
+    }
+
+    if (!definition.appliesTo.includes(subject.kind)) {
+      results.push({
+        status: 'not-applicable',
+        checkId,
+        checkVersion: definition.version,
+        subject: subjectPath,
+        reason: `check '${checkId}' does not apply to subject kind '${subject.kind}'`,
+      });
+      continue;
+    }
+
+    try {
+      const inputs = options.inputs?.[checkId] ?? {};
+      const outcome = await definition.evaluate({
+        subject,
+        params: definition.params,
+        inputs,
+        adapter,
+      });
+      if (outcome.status !== 'passed' && (outcome.reason === undefined || outcome.reason === '')) {
+        results.push({
+          status: 'error',
+          checkId,
+          checkVersion: definition.version,
+          subject: subjectPath,
+          reason: `check returned status '${outcome.status}' without a reason — treated as error`,
+        });
+        continue;
+      }
+      results.push({
+        status: outcome.status,
+        checkId,
+        checkVersion: definition.version,
+        subject: subjectPath,
+        reason: outcome.reason,
+      });
+    } catch (error) {
+      results.push({
+        status: 'error',
+        checkId,
+        checkVersion: definition.version,
+        subject: subjectPath,
+        reason: `check implementation threw: ${reasonFrom(error)}`,
+      });
+    }
+  }
+
+  return {
+    subject,
+    results,
+    definitionDigests,
+    checkSetVersion: CHECK_SET_POLICY.version,
+    state: aggregateState(results),
+  };
+}
diff --git a/packages/quality-rails/src/evaluator/types.ts b/packages/quality-rails/src/evaluator/types.ts
new file mode 100644
index 00000000..8edd4080
--- /dev/null
+++ b/packages/quality-rails/src/evaluator/types.ts
@@ -0,0 +1,148 @@
+// Evaluator core types — RI-N4 (card RI-3-002, SDLC-D-037 second half).
+//
+// The quality-rails evaluator is the SOLE authoritative producer of check
+// verdicts for the checks it owns. Every verdict is typed and fail-closed:
+// missing implementations, missing inputs, unknown check ids, process errors,
+// timeouts, and malformed adapter output can never become `passed` or an
+// unqualified skip — they surface as `blocked` or `error` with a reason.
+// (Vocabulary mirrors MACP's GateStatus discipline from packages/macp.)
+
+/**
+ * Typed verdict for a single check execution.
+ *
+ * - `passed` — the check really ran and its condition held.
+ * - `failed` — the check really ran and its condition did NOT hold.
+ * - `blocked` — the check could not run at all (missing subject, missing
+ *   input). Never a green outcome.
+ * - `error` — the check attempted to run but its outcome cannot be trusted
+ *   (unknown check id, implementation threw, process error, timeout, malformed
+ *   adapter output). Never a green outcome.
+ * - `not-applicable` — the check definition explicitly declares it does not
+ *   apply to this subject (a qualified skip, always with a reason).
+ */
+export type CheckStatus = 'passed' | 'failed' | 'blocked' | 'error' | 'not-applicable';
+
+/** Aggregate outcome, MACP-style: `passed` only when every result is green. */
+export type AggregateState = 'passed' | 'failed' | 'blocked' | 'error';
+
+/** Kinds of subjects the evaluator can assess. */
+export type SubjectKind = 'node' | 'python' | 'rust' | 'monorepo' | 'unknown';
+
+/**
+ * A single check verdict. This is the canonical result shape: `status`,
+ * `checkId`, `checkVersion`, `subject`, `reason`. `reason` is REQUIRED
+ * (enforced by the runner) for every status other than `passed`.
+ */
+export interface CheckResult {
+  status: CheckStatus;
+  checkId: string;
+  checkVersion: string;
+  subject: string;
+  reason?: string;
+}
+
+/** The project being evaluated. */
+export interface Subject {
+  /** Absolute path. */
+  path: string;
+  kind: SubjectKind;
+}
+
+/**
+ * The data half of a check definition. Definitions live as DATA with a version
+ * and a content digest (see `digestOfSpec`); the executable half is attached
+ * separately so the digest covers only reviewable, declarative content.
+ */
+export interface CheckDefinitionSpec {
+  /** Stable id, e.g. `qc-19-rails-files-present`. */
+  id: string;
+  /** Semver of this definition's data+semantics. */
+  version: string;
+  /** Canonical check id from docs/release-integrity/probe-inventory.md (QC-n). */
+  canonicalCheck: string;
+  description: string;
+  /** Subject kinds this check can assess (others yield `not-applicable`). */
+  appliesTo: readonly SubjectKind[];
+  /** Declarative parameters (file lists, markers, timeouts) — digest-covered. */
+  params: Record<string, unknown>;
+}
+
+/** A fully assembled check definition: spec + digest + implementation. */
+export interface CheckDefinition extends CheckDefinitionSpec {
+  /** sha256 content digest of the spec (canonical JSON projection). */
+  definitionDigest: string;
+  evaluate(ctx: CheckContext): Promise<CheckOutcome>;
+}
+
+/** What a check implementation returns; the runner stamps id/version/subject. */
+export interface CheckOutcome {
+  status: CheckStatus;
+  reason?: string;
+}
+
+/** Caller-provided inputs for one check invocation (e.g. the QC-20 probe path). */
+export type CheckInputs = Record<string, unknown>;
+
+/** Everything a check implementation may use. */
+export interface CheckContext {
+  subject: Subject;
+  params: Record<string, unknown>;
+  inputs: CheckInputs;
+  adapter: ProcessAdapter;
+}
+
+/** Outcome of running a shell probe through the thin process adapter. */
+export type AdapterOutcome =
+  | { ok: true; exitCode: number | null; stdout: string; stderr: string }
+  | { ok: false; kind: 'spawn-error' | 'timeout'; message: string };
+
+/** Request for the process adapter. */
+export interface AdapterRequest {
+  file: string;
+  args: string[];
+  cwd: string;
+  timeoutMs: number;
+}
+
+/**
+ * Thin process adapter: runs a command, owns NO verdict logic. Verdict parsing
+ * always lives in the check implementation (TS), never in the shell probe.
+ */
+export interface ProcessAdapter {
+  run(request: AdapterRequest): Promise<AdapterOutcome>;
+}
+
+/** Per-subject-kind check-set selection policy (versioned and digested). */
+export interface CheckSetPolicySpec {
+  version: string;
+  byKind: Record<SubjectKind, readonly string[]>;
+}
+
+export interface CheckSetPolicy extends CheckSetPolicySpec {
+  /** sha256 content digest of the policy spec. */
+  policyDigest: string;
+}
+
+/** Full typed evaluation report for one subject. */
+export interface EvaluationReport {
+  subject: Subject;
+  results: CheckResult[];
+  /** checkId → content digest of the definition that produced the verdicts. */
+  definitionDigests: Record<string, string>;
+  /** Version of the check-set policy used for subject selection. */
+  checkSetVersion: string;
+  state: AggregateState;
+}
+
+/** Options for `evaluateSubject`. */
+export interface EvaluateOptions {
+  subjectPath: string;
+  /** Restrict to these check ids; defaults to the subject kind's check set. */
+  checkIds?: string[];
+  /** Per-check inputs, keyed by check id (e.g. `{ 'qc-20-enforcement-verify': { probePath } }`). */
+  inputs?: Record<string, CheckInputs>;
+  /** Replace the built-in definitions (tests / future batches). */
+  definitions?: CheckDefinition[];
+  /** Inject a process adapter (tests / instrumentation). */
+  adapter?: ProcessAdapter;
+}
diff --git a/packages/quality-rails/src/index.ts b/packages/quality-rails/src/index.ts
index 3f61eb1f..c0c927ef 100644
--- a/packages/quality-rails/src/index.ts
+++ b/packages/quality-rails/src/index.ts
@@ -3,3 +3,35 @@ export * from './detect.js';
 export * from './scaffolder.js';
 export * from './templates.js';
 export * from './types.js';
+
+// RI-N4 evaluator (card RI-3-002): the public, programmatic entry points.
+export {
+  builtInDefinitions,
+  CHECK_SET_POLICY,
+  checkSetForKind,
+  defineCheck,
+  QC_19_RAILS_FILES_PRESENT,
+  QC_20_ENFORCEMENT_VERIFY,
+} from './evaluator/definitions.js';
+export { canonicalJson, digestContent, digestOfPolicy, digestOfSpec } from './evaluator/digest.js';
+export { createSpawnProcessAdapter } from './evaluator/adapter.js';
+export { aggregateState, detectSubjectKind, evaluateSubject } from './evaluator/runner.js';
+export type {
+  AdapterOutcome,
+  AdapterRequest,
+  AggregateState,
+  CheckContext,
+  CheckDefinition,
+  CheckDefinitionSpec,
+  CheckInputs,
+  CheckOutcome,
+  CheckResult,
+  CheckSetPolicy,
+  CheckSetPolicySpec,
+  CheckStatus,
+  EvaluateOptions,
+  EvaluationReport,
+  ProcessAdapter,
+  Subject,
+  SubjectKind,
+} from './evaluator/types.js';
diff --git a/scripts/verify-release.mjs b/scripts/verify-release.mjs
index f0b518f4..ca7ab100 100644
--- a/scripts/verify-release.mjs
+++ b/scripts/verify-release.mjs
@@ -22,6 +22,12 @@
 //   format        | format              | pnpm format:check
 //   test          | test                | pnpm test
 //   build         | publish.yml build   | pnpm build
+//   quality-rails | (canonical-only)    | the TS quality-rails evaluator
+//                |                     | (RI-N4, QC-19 monorepo subject). Like
+//                |                     | `build`, this stage has no ci.yml
+//                |                     | mirror; it is implemented by
+//                |                     | importing the evaluator CLI rather
+//                |                     | than duplicating its presence logic.
 //
 // Caller-provided prerequisites (kept at the pipeline level — see the comments
 // in .woodpecker/ci.yml): `bash` + `rsync` for the guard stages, `openssl` and
@@ -90,6 +96,15 @@ export const STAGES = [
     name: 'build',
     commands: ['pnpm build'],
   },
+  {
+    // RI-N4 (QC-19, card RI-3-002): the typed quality-rails evaluator, invoked
+    // as the implementation of the check it owns instead of a duplicated
+    // presence loop here. Canonical-only stage (no ci.yml mirror — same shape
+    // as `build`); runs AFTER build so the evaluator's dist/ exists. Subject
+    // is this repository (`.` → monorepo subject kind, per-subject check set).
+    name: 'quality-rails',
+    commands: ['node packages/quality-rails/dist/cli.js quality-rails evaluate --project .'],
+  },
 ];
 
 export function stageByName(name) {
diff --git a/scripts/verify-release.test.mjs b/scripts/verify-release.test.mjs
index 49e9ff5b..677c65af 100644
--- a/scripts/verify-release.test.mjs
+++ b/scripts/verify-release.test.mjs
@@ -4,7 +4,7 @@ import { createRequire } from 'node:module';
 import path from 'node:path';
 import test from 'node:test';
 
-import { STAGES } from './verify-release.mjs';
+import { STAGES, stageByName } from './verify-release.mjs';
 
 // SDLC-D-034 checkout invariant: publication in .woodpecker/publish.yml is
 // bound to exact-commit terminal verification. This suite parses the real
@@ -229,10 +229,21 @@ steps:
 function assertStagesMirrorCi(stages, ci) {
   const canonical = Object.fromEntries(stages.map((stage) => [stage.name, stage.commands]));
 
-  // The complete mandatory set, in gate order.
+  // The complete mandatory set, in gate order. `quality-rails` is a
+  // canonical-only stage (RI-N4, QC-19): like `build`, it has no ci.yml
+  // mirror to match — its contract is asserted separately below.
   assert.deepEqual(
     stages.map((stage) => stage.name),
-    ['sanitization', 'upgrade-guard', 'typecheck', 'lint', 'format', 'test', 'build'],
+    [
+      'sanitization',
+      'upgrade-guard',
+      'typecheck',
+      'lint',
+      'format',
+      'test',
+      'build',
+      'quality-rails',
+    ],
   );
 
   // Guard stages: ci.yml commands minus its `apk add` environment prep must be
@@ -301,3 +312,38 @@ test('the root package.json exposes verify:release as the canonical command', as
   const packageJson = JSON.parse(await readFile(path.join(process.cwd(), 'package.json'), 'utf8'));
   assert.match(packageJson.scripts['verify:release'], /scripts\/verify-release\.mjs/);
 });
+
+// RI-N4 (card RI-3-002): the `quality-rails` stage must route through the TS
+// evaluator instead of duplicating its presence logic inline. The evaluator
+// owns QC-19; this file keeps that delegation honest.
+function assertEvaluatorStage(stage) {
+  assert.ok(stage, 'canonical stages must include a quality-rails stage');
+  assert.ok(Array.isArray(stage.commands) && stage.commands.length > 0);
+  for (const command of stage.commands) {
+    assert.match(
+      command,
+      /packages\/quality-rails\/dist\/cli\.js.*quality-rails evaluate/,
+      `quality-rails stage command must invoke the evaluator CLI, got: '${command}'`,
+    );
+  }
+}
+
+test('the quality-rails stage invokes the evaluator rather than duplicating its logic', () => {
+  assertEvaluatorStage(stageByName('quality-rails'));
+});
+
+test('a quality-rails stage that re-implements presence logic inline fails the checker', () => {
+  // Negative control: replacing the evaluator invocation with an inline
+  // `test -f` presence loop is exactly the duplication RI-N4 forbids — the
+  // checker must go red on it.
+  const duplicated = {
+    name: 'quality-rails',
+    commands: ['test -f .husky/pre-commit && test -f .husky/pre-push'],
+  };
+  assert.throws(() => assertEvaluatorStage(duplicated), /must invoke the evaluator CLI/);
+});
+
+test('a quality-rails stage that silently drops the evaluator command fails the checker', () => {
+  const empty = { name: 'quality-rails', commands: [] };
+  assert.throws(() => assertEvaluatorStage(empty), /commands/);
+});