fix(federation/auth-guard): remediate CRIT-1/CRIT-2 + HIGH-1..4 review findings

- CRIT-1: Validate cert subjectUserId against grant.subjectUserId from DB;
  use authoritative DB value in FederationContext
- CRIT-2: Add @Inject(GrantsService) decorator (tsx/esbuild requirement)
- HIGH-1: Validate UTF8String TLV tag, length, and bounds in OID parser
- HIGH-2: Collapse all 403 wire messages to a generic string to prevent
  grant enumeration; keep internal logger detail
- HIGH-3: Assert federation wire envelope shape in all guard tests
- HIGH-4: Regression test for subjectUserId cert/DB mismatch

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/gateway/src/federation/__tests__/enrollment.service.spec.ts

@@ -24,10 +24,11 @@
  */
 
 import 'reflect-metadata';
-import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { describe, it, expect, vi, beforeEach, beforeAll } from 'vitest';
 import { GoneException, NotFoundException } from '@nestjs/common';
 import type { Db } from '@mosaicstack/db';
 import { EnrollmentService } from '../enrollment.service.js';
+import { makeSelfSignedCert } from './helpers/test-cert.js';
 
 // ---------------------------------------------------------------------------
 // Test constants
@@ -38,10 +39,18 @@ const PEER_ID = 'p2222222-2222-2222-2222-222222222222';
 const USER_ID = 'u3333333-3333-3333-3333-333333333333';
 const TOKEN = 'a'.repeat(64); // 64-char hex
 
-const MOCK_CERT_PEM = '-----BEGIN CERTIFICATE-----\nMOCK\n-----END CERTIFICATE-----\n';
+// Real self-signed EC P-256 cert — populated once in beforeAll.
-const MOCK_CHAIN_PEM = MOCK_CERT_PEM + MOCK_CERT_PEM;
+// Required because EnrollmentService.extractCertNotAfter calls new X509Certificate(certPem)
+// with strict parsing (PR #501 HIGH-2: no silent fallback).
+let REAL_CERT_PEM: string;
+
+const MOCK_CHAIN_PEM = () => REAL_CERT_PEM + REAL_CERT_PEM;
 const MOCK_SERIAL = 'ABCD1234';
 
+beforeAll(async () => {
+  REAL_CERT_PEM = await makeSelfSignedCert();
+});
+
 // ---------------------------------------------------------------------------
 // Factory helpers
 // ---------------------------------------------------------------------------
@@ -103,11 +112,27 @@ function makeDb({
   const claimUpdateMock = vi.fn().mockReturnValue({ set: setClaimMock });
 
   // transaction(cb) — cb receives txMock; txMock has update + insert
-  const txInsertValues = vi.fn().mockResolvedValue(undefined);
+  //
-  const txInsertMock = vi.fn().mockReturnValue({ values: txInsertValues });
+  // The tx mock must support two tx.update() call patterns (CRIT-2, PR #501):
-  const txWhereUpdate = vi.fn().mockResolvedValue(undefined);
+  //   1. Grant activation:  .update().set().where().returning() → resolves to [{ id }]
+  //   2. Peer update:       .update().set().where()             → resolves to undefined
+  //
+  // We achieve this by making txWhereUpdate return an object with BOTH a thenable
+  // interface (so `await tx.update().set().where()` works) AND a .returning() method.
+  const txGrantActivatedRow = { id: GRANT_ID };
+  const txReturningMock = vi.fn().mockResolvedValue([txGrantActivatedRow]);
+  const txWhereUpdate = vi.fn().mockReturnValue({
+    // .returning() for grant activation (first tx.update call)
+    returning: txReturningMock,
+    // thenables so `await tx.update().set().where()` also works for peer update
+    then: (resolve: (v: undefined) => void) => resolve(undefined),
+    catch: () => undefined,
+    finally: () => undefined,
+  });
   const txSetMock = vi.fn().mockReturnValue({ where: txWhereUpdate });
   const txUpdateMock = vi.fn().mockReturnValue({ set: txSetMock });
+  const txInsertValues = vi.fn().mockResolvedValue(undefined);
+  const txInsertMock = vi.fn().mockReturnValue({ values: txInsertValues });
   const txMock = { update: txUpdateMock, insert: txInsertMock };
   const transactionMock = vi
     .fn()
@@ -132,6 +157,7 @@ function makeDb({
       txInsertValues,
       txInsertMock,
       txWhereUpdate,
+      txReturningMock,
       txSetMock,
       txUpdateMock,
       txMock,
@@ -146,11 +172,13 @@ function makeDb({
 
 function makeCaService() {
   return {
-    issueCert: vi.fn().mockResolvedValue({
+    // REAL_CERT_PEM is populated by beforeAll — safe to reference via closure here
-      certPem: MOCK_CERT_PEM,
+    // because makeCaService() is only called after the suite's beforeAll runs.
-      certChainPem: MOCK_CHAIN_PEM,
+    issueCert: vi.fn().mockImplementation(async () => ({
+      certPem: REAL_CERT_PEM,
+      certChainPem: MOCK_CHAIN_PEM(),
       serialNumber: MOCK_SERIAL,
-    }),
+    })),
   };
 }
 
@@ -301,29 +329,29 @@ describe('EnrollmentService.redeem — success path', () => {
     });
     caService.issueCert.mockImplementation(async () => {
       callOrder.push('issueCert');
-      return { certPem: MOCK_CERT_PEM, certChainPem: MOCK_CHAIN_PEM, serialNumber: MOCK_SERIAL };
+      return { certPem: REAL_CERT_PEM, certChainPem: MOCK_CHAIN_PEM(), serialNumber: MOCK_SERIAL };
     });
 
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(callOrder).toEqual(['claim', 'issueCert']);
   });
 
   it('calls CaService.issueCert with grantId, subjectUserId, csrPem, ttlSeconds=300', async () => {
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(caService.issueCert).toHaveBeenCalledWith(
       expect.objectContaining({
         grantId: GRANT_ID,
         subjectUserId: USER_ID,
-        csrPem: MOCK_CERT_PEM,
+        csrPem: '---CSR---',
         ttlSeconds: 300,
       }),
     );
   });
 
   it('runs activate grant + peer update + audit inside a transaction', async () => {
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(db._mocks.transactionMock).toHaveBeenCalledOnce();
     // tx.update called twice: activate grant + update peer
@@ -333,17 +361,17 @@ describe('EnrollmentService.redeem — success path', () => {
   });
 
   it('activates grant (sets status=active) inside the transaction', async () => {
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(db._mocks.txSetMock).toHaveBeenCalledWith(expect.objectContaining({ status: 'active' }));
   });
 
   it('updates the federationPeers row with certPem, certSerial, state=active inside the transaction', async () => {
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(db._mocks.txSetMock).toHaveBeenCalledWith(
       expect.objectContaining({
-        certPem: MOCK_CERT_PEM,
+        certPem: REAL_CERT_PEM,
         certSerial: MOCK_SERIAL,
         state: 'active',
       }),
@@ -351,7 +379,7 @@ describe('EnrollmentService.redeem — success path', () => {
   });
 
   it('inserts an audit log row inside the transaction', async () => {
-    await service.redeem(TOKEN, MOCK_CERT_PEM);
+    await service.redeem(TOKEN, '---CSR---');
 
     expect(db._mocks.txInsertValues).toHaveBeenCalledWith(
       expect.objectContaining({
@@ -363,11 +391,11 @@ describe('EnrollmentService.redeem — success path', () => {
   });
 
   it('returns { certPem, certChainPem } from CaService', async () => {
-    const result = await service.redeem(TOKEN, MOCK_CERT_PEM);
+    const result = await service.redeem(TOKEN, '---CSR---');
 
     expect(result).toEqual({
-      certPem: MOCK_CERT_PEM,
+      certPem: REAL_CERT_PEM,
-      certChainPem: MOCK_CHAIN_PEM,
+      certChainPem: MOCK_CHAIN_PEM(),
     });
   });
 });

apps/gateway/src/federation/__tests__/helpers/test-cert.ts

@@ -0,0 +1,138 @@
+/**
+ * Test helpers for generating real X.509 PEM certificates in unit tests.
+ *
+ * PR #501 (FED-M2-11) introduced strict `new X509Certificate(certPem)` parsing
+ * in both EnrollmentService.extractCertNotAfter and CaService.issueCert — dummy
+ * cert strings now throw `error:0680007B:asn1 encoding routines::header too long`.
+ *
+ * These helpers produce minimal but cryptographically valid self-signed EC P-256
+ * certificates via @peculiar/x509 + Node.js webcrypto, suitable for test mocks.
+ *
+ * Two variants:
+ *  - makeSelfSignedCert()          Plain cert — satisfies node:crypto X509Certificate parse.
+ *  - makeMosaicIssuedCert(opts)    Cert with custom Mosaic OID extensions — satisfies the
+ *                                  CRIT-1 OID presence + value checks in CaService.issueCert.
+ */
+
+import { webcrypto } from 'node:crypto';
+import {
+  X509CertificateGenerator,
+  Extension,
+  KeyUsagesExtension,
+  KeyUsageFlags,
+  BasicConstraintsExtension,
+  cryptoProvider,
+} from '@peculiar/x509';
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+/**
+ * Encode a string as an ASN.1 UTF8String TLV:
+ *   0x0C (tag) + 1-byte length (for strings ≤ 127 bytes) + UTF-8 bytes.
+ *
+ * CaService.issueCert reads the extension value as:
+ *   decoder.decode(grantIdExt.value.slice(2))
+ * i.e. it skips the tag + length byte and decodes the remainder as UTF-8.
+ * So we must produce exactly this encoding as the OCTET STRING content.
+ */
+function encodeUtf8String(value: string): Uint8Array {
+  const utf8 = new TextEncoder().encode(value);
+  if (utf8.length > 127) {
+    throw new Error('encodeUtf8String: value too long for single-byte length encoding');
+  }
+  const buf = new Uint8Array(2 + utf8.length);
+  buf[0] = 0x0c; // ASN.1 UTF8String tag
+  buf[1] = utf8.length;
+  buf.set(utf8, 2);
+  return buf;
+}
+
+// ---------------------------------------------------------------------------
+// Mosaic OID constants (must match production CaService)
+// ---------------------------------------------------------------------------
+
+const OID_MOSAIC_GRANT_ID = '1.3.6.1.4.1.99999.1';
+const OID_MOSAIC_SUBJECT_USER_ID = '1.3.6.1.4.1.99999.2';
+
+// ---------------------------------------------------------------------------
+// Public API
+// ---------------------------------------------------------------------------
+
+/**
+ * Generate a minimal self-signed EC P-256 certificate valid for 1 day.
+ * CN=harness-test, no custom extensions.
+ *
+ * Suitable for:
+ *  - EnrollmentService.extractCertNotAfter (just needs parseable PEM)
+ *  - Any mock that returns certPem / certChainPem without OID checks
+ */
+export async function makeSelfSignedCert(): Promise<string> {
+  // Ensure @peculiar/x509 uses Node.js webcrypto (available as globalThis.crypto in Node 19+,
+  // but we set it explicitly here to be safe on all Node 18+ versions).
+  cryptoProvider.set(webcrypto as unknown as Parameters<typeof cryptoProvider.set>[0]);
+
+  const alg = { name: 'ECDSA', namedCurve: 'P-256', hash: 'SHA-256' } as const;
+  const keys = await webcrypto.subtle.generateKey(alg, false, ['sign', 'verify']);
+
+  const now = new Date();
+  const tomorrow = new Date(now.getTime() + 86_400_000);
+
+  const cert = await X509CertificateGenerator.createSelfSigned({
+    serialNumber: '01',
+    name: 'CN=harness-test',
+    notBefore: now,
+    notAfter: tomorrow,
+    signingAlgorithm: alg,
+    keys,
+    extensions: [
+      new BasicConstraintsExtension(false),
+      new KeyUsagesExtension(KeyUsageFlags.digitalSignature),
+    ],
+  });
+
+  return cert.toString('pem');
+}
+
+/**
+ * Generate a self-signed EC P-256 certificate that contains the two custom
+ * Mosaic OID extensions required by CaService.issueCert's CRIT-1 check:
+ *   OID 1.3.6.1.4.1.99999.1  → mosaic_grant_id   (value = grantId)
+ *   OID 1.3.6.1.4.1.99999.2  → mosaic_subject_user_id (value = subjectUserId)
+ *
+ * The extension value encoding matches the production parser's `.slice(2)` assumption:
+ * each extension value is an OCTET STRING wrapping an ASN.1 UTF8String TLV.
+ */
+export async function makeMosaicIssuedCert(opts: {
+  grantId: string;
+  subjectUserId: string;
+}): Promise<string> {
+  // Ensure @peculiar/x509 uses Node.js webcrypto.
+  cryptoProvider.set(webcrypto as unknown as Parameters<typeof cryptoProvider.set>[0]);
+
+  const alg = { name: 'ECDSA', namedCurve: 'P-256', hash: 'SHA-256' } as const;
+  const keys = await webcrypto.subtle.generateKey(alg, false, ['sign', 'verify']);
+
+  const now = new Date();
+  const tomorrow = new Date(now.getTime() + 86_400_000);
+
+  const cert = await X509CertificateGenerator.createSelfSigned({
+    serialNumber: '01',
+    name: 'CN=mosaic-issued-test',
+    notBefore: now,
+    notAfter: tomorrow,
+    signingAlgorithm: alg,
+    keys,
+    extensions: [
+      new BasicConstraintsExtension(false),
+      new KeyUsagesExtension(KeyUsageFlags.digitalSignature),
+      // mosaic_grant_id — OID 1.3.6.1.4.1.99999.1
+      new Extension(OID_MOSAIC_GRANT_ID, false, encodeUtf8String(opts.grantId)),
+      // mosaic_subject_user_id — OID 1.3.6.1.4.1.99999.2
+      new Extension(OID_MOSAIC_SUBJECT_USER_ID, false, encodeUtf8String(opts.subjectUserId)),
+    ],
+  });
+
+  return cert.toString('pem');
+}

apps/gateway/src/federation/ca.service.spec.ts

@@ -20,9 +20,10 @@
  */
 
 import 'reflect-metadata';
-import { describe, it, expect, vi, beforeEach, type Mock } from 'vitest';
+import { describe, it, expect, vi, beforeEach, beforeAll, type Mock } from 'vitest';
 import { jwtVerify, exportJWK, generateKeyPair } from 'jose';
 import { Pkcs10CertificateRequestGenerator } from '@peculiar/x509';
+import { makeMosaicIssuedCert } from './__tests__/helpers/test-cert.js';
 
 // ---------------------------------------------------------------------------
 // Mock node:https BEFORE importing CaService so the mock is in place when
@@ -74,6 +75,11 @@ const FAKE_CA_PEM = FAKE_CERT_PEM;
 const GRANT_ID = 'a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11';
 const SUBJECT_USER_ID = 'b1ffcd00-0d1c-5f09-cc7e-7cc0ce491b22';
 
+// Real self-signed cert containing both Mosaic OID extensions — populated in beforeAll.
+// Required because CaService.issueCert performs CRIT-1 OID presence/value checks on the
+// response cert (PR #501 — strict parsing, no silent fallback).
+let realIssuedCertPem: string;
+
 // ---------------------------------------------------------------------------
 // Generate a real EC P-256 key pair and CSR for integration-style tests
 // ---------------------------------------------------------------------------
@@ -194,6 +200,15 @@ function makeHttpsMock(statusCode: number, body: unknown, errorMsg?: string): vo
 describe('CaService', () => {
   let service: CaService;
 
+  beforeAll(async () => {
+    // Generate a cert with the two Mosaic OIDs so that CaService.issueCert's
+    // CRIT-1 OID checks pass when mock step-ca returns it as `crt`.
+    realIssuedCertPem = await makeMosaicIssuedCert({
+      grantId: GRANT_ID,
+      subjectUserId: SUBJECT_USER_ID,
+    });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
     service = new CaService();
@@ -226,9 +241,9 @@ describe('CaService', () => {
 
     // Now test that the service's validateCsr accepts it.
     // We call it indirectly via issueCert with a successful mock.
-    makeHttpsMock(200, { crt: FAKE_CERT_PEM, certChain: [FAKE_CERT_PEM, FAKE_CA_PEM] });
+    makeHttpsMock(200, { crt: realIssuedCertPem, certChain: [realIssuedCertPem, FAKE_CA_PEM] });
     const result = await service.issueCert(makeReq({ csrPem: realCsrPem }));
-    expect(result.certPem).toBe(FAKE_CERT_PEM);
+    expect(result.certPem).toBe(realIssuedCertPem);
   });
 
   it('throws INVALID_CSR for a malformed PEM-shaped CSR', async () => {
@@ -251,14 +266,14 @@ describe('CaService', () => {
   it('returns IssuedCertDto on success (certChain present)', async () => {
     if (!realCsrPem) realCsrPem = await generateRealCsr();
     makeHttpsMock(200, {
-      crt: FAKE_CERT_PEM,
+      crt: realIssuedCertPem,
-      certChain: [FAKE_CERT_PEM, FAKE_CA_PEM],
+      certChain: [realIssuedCertPem, FAKE_CA_PEM],
     });
 
     const result = await service.issueCert(makeReq());
 
-    expect(result.certPem).toBe(FAKE_CERT_PEM);
+    expect(result.certPem).toBe(realIssuedCertPem);
-    expect(result.certChainPem).toContain(FAKE_CERT_PEM);
+    expect(result.certChainPem).toContain(realIssuedCertPem);
     expect(result.certChainPem).toContain(FAKE_CA_PEM);
     expect(typeof result.serialNumber).toBe('string');
   });
@@ -270,14 +285,14 @@ describe('CaService', () => {
   it('builds certChainPem from crt+ca when certChain is absent', async () => {
     if (!realCsrPem) realCsrPem = await generateRealCsr();
     makeHttpsMock(200, {
-      crt: FAKE_CERT_PEM,
+      crt: realIssuedCertPem,
       ca: FAKE_CA_PEM,
     });
 
     const result = await service.issueCert(makeReq());
 
-    expect(result.certPem).toBe(FAKE_CERT_PEM);
+    expect(result.certPem).toBe(realIssuedCertPem);
-    expect(result.certChainPem).toContain(FAKE_CERT_PEM);
+    expect(result.certChainPem).toContain(realIssuedCertPem);
     expect(result.certChainPem).toContain(FAKE_CA_PEM);
   });
 
@@ -287,12 +302,12 @@ describe('CaService', () => {
 
   it('falls back to certPem alone when certChain and ca are absent', async () => {
     if (!realCsrPem) realCsrPem = await generateRealCsr();
-    makeHttpsMock(200, { crt: FAKE_CERT_PEM });
+    makeHttpsMock(200, { crt: realIssuedCertPem });
 
     const result = await service.issueCert(makeReq());
 
-    expect(result.certPem).toBe(FAKE_CERT_PEM);
+    expect(result.certPem).toBe(realIssuedCertPem);
-    expect(result.certChainPem).toBe(FAKE_CERT_PEM);
+    expect(result.certChainPem).toBe(realIssuedCertPem);
   });
 
   // -------------------------------------------------------------------------
@@ -398,7 +413,7 @@ describe('CaService', () => {
           statusCode: 200,
           on: (event: string, cb: (chunk?: Buffer) => void) => {
             if (event === 'data') {
-              cb(Buffer.from(JSON.stringify({ crt: FAKE_CERT_PEM })));
+              cb(Buffer.from(JSON.stringify({ crt: realIssuedCertPem })));
             }
             if (event === 'end') {
               cb();
@@ -555,7 +570,7 @@ describe('CaService', () => {
           statusCode: 200,
           on: (event: string, cb: (chunk?: Buffer) => void) => {
             if (event === 'data') {
-              cb(Buffer.from(JSON.stringify({ crt: FAKE_CERT_PEM })));
+              cb(Buffer.from(JSON.stringify({ crt: realIssuedCertPem })));
             }
             if (event === 'end') {
               cb();

apps/gateway/src/federation/federation.module.ts

@@ -5,10 +5,11 @@ import { EnrollmentController } from './enrollment.controller.js';
 import { EnrollmentService } from './enrollment.service.js';
 import { FederationController } from './federation.controller.js';
 import { GrantsService } from './grants.service.js';
+import { FederationAuthGuard } from './server/index.js';
 
 @Module({
   controllers: [EnrollmentController, FederationController],
-  providers: [AdminGuard, CaService, EnrollmentService, GrantsService],
+  providers: [AdminGuard, CaService, EnrollmentService, GrantsService, FederationAuthGuard],
-  exports: [CaService, EnrollmentService, GrantsService],
+  exports: [CaService, EnrollmentService, GrantsService, FederationAuthGuard],
 })
 export class FederationModule {}

apps/gateway/src/federation/grants.service.ts

@@ -10,12 +10,14 @@
  */
 
 import { ConflictException, Inject, Injectable, NotFoundException } from '@nestjs/common';
-import { type Db, and, eq, federationGrants } from '@mosaicstack/db';
+import { type Db, and, eq, federationGrants, federationPeers } from '@mosaicstack/db';
 import { DB } from '../database/database.module.js';
 import { parseFederationScope } from './scope-schema.js';
 import type { CreateGrantDto, ListGrantsDto } from './grants.dto.js';
 
 export type Grant = typeof federationGrants.$inferSelect;
+export type Peer = typeof federationPeers.$inferSelect;
+export type GrantWithPeer = Grant & { peer: Peer };
 
 @Injectable()
 export class GrantsService {
@@ -60,6 +62,33 @@ export class GrantsService {
     return grant;
   }
 
+  /**
+   * Fetch a single grant by ID, joined with its associated peer row.
+   * Used by FederationAuthGuard to perform grant status + cert serial checks
+   * in a single DB round-trip.
+   *
+   * Throws NotFoundException if the grant does not exist.
+   * Throws NotFoundException if the associated peer row is missing (data integrity issue).
+   */
+  async getGrantWithPeer(id: string): Promise<GrantWithPeer> {
+    const rows = await this.db
+      .select()
+      .from(federationGrants)
+      .innerJoin(federationPeers, eq(federationGrants.peerId, federationPeers.id))
+      .where(eq(federationGrants.id, id))
+      .limit(1);
+
+    const row = rows[0];
+    if (!row) {
+      throw new NotFoundException(`Grant ${id} not found`);
+    }
+
+    return {
+      ...row.federation_grants,
+      peer: row.federation_peers,
+    };
+  }
+
   /**
    * List grants with optional filters for peerId, subjectUserId, and status.
    */

apps/gateway/src/federation/oid.util.ts

@@ -0,0 +1,146 @@
+/**
+ * Shared OID extraction helpers for Mosaic federation certificates.
+ *
+ * Custom OID registry (PRD §6, docs/federation/SETUP.md):
+ *   1.3.6.1.4.1.99999.1  — mosaic_grant_id
+ *   1.3.6.1.4.1.99999.2  — mosaic_subject_user_id
+ *
+ * The encoding convention: each extension value is an OCTET STRING wrapping
+ * an ASN.1 UTF8String TLV:
+ *   0x0C (tag) + 1-byte length + UTF-8 bytes
+ *
+ * CaService encodes values this way via encodeUtf8String(), and this module
+ * decodes them with the corresponding `.slice(2)` to skip tag + length byte.
+ *
+ * This module is intentionally pure — no NestJS, no DB, no network I/O.
+ */
+
+import { X509Certificate } from '@peculiar/x509';
+
+// ---------------------------------------------------------------------------
+// OID constants
+// ---------------------------------------------------------------------------
+
+export const OID_MOSAIC_GRANT_ID = '1.3.6.1.4.1.99999.1';
+export const OID_MOSAIC_SUBJECT_USER_ID = '1.3.6.1.4.1.99999.2';
+
+// ---------------------------------------------------------------------------
+// Extraction result types
+// ---------------------------------------------------------------------------
+
+export interface MosaicOids {
+  grantId: string;
+  subjectUserId: string;
+}
+
+export type OidExtractionResult =
+  | { ok: true; value: MosaicOids }
+  | {
+      ok: false;
+      error: 'MISSING_GRANT_ID' | 'MISSING_SUBJECT_USER_ID' | 'PARSE_ERROR';
+      detail?: string;
+    };
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+const decoder = new TextDecoder();
+
+/**
+ * Decode an extension value encoded as ASN.1 UTF8String TLV
+ * (tag 0x0C + 1-byte length + UTF-8 bytes).
+ * Validates tag, length byte, and buffer bounds before decoding.
+ * Throws a descriptive Error on malformed input; caller wraps in try/catch.
+ */
+function decodeUtf8StringTlv(value: ArrayBuffer): string {
+  const bytes = new Uint8Array(value);
+
+  // Need at least tag + length bytes
+  if (bytes.length < 2) {
+    throw new Error(`UTF8String TLV too short: expected at least 2 bytes, got ${bytes.length}`);
+  }
+
+  // Tag byte must be 0x0C (ASN.1 UTF8String)
+  if (bytes[0] !== 0x0c) {
+    throw new Error(
+      `UTF8String TLV tag mismatch: expected 0x0C, got 0x${bytes[0]!.toString(16).toUpperCase()}`,
+    );
+  }
+
+  // Only single-byte length form is supported (values 0–127); long form not needed
+  // for OID strings of this length.
+  const declaredLength = bytes[1]!;
+  if (declaredLength > 127) {
+    throw new Error(
+      `UTF8String TLV uses long-form length (0x${declaredLength.toString(16).toUpperCase()}), which is not supported`,
+    );
+  }
+
+  // Declared length must match actual remaining bytes
+  if (declaredLength !== bytes.length - 2) {
+    throw new Error(
+      `UTF8String TLV length mismatch: declared ${declaredLength}, actual ${bytes.length - 2}`,
+    );
+  }
+
+  // Skip: tag (1 byte) + length (1 byte)
+  return decoder.decode(bytes.slice(2));
+}
+
+// ---------------------------------------------------------------------------
+// Public API
+// ---------------------------------------------------------------------------
+
+/**
+ * Extract Mosaic custom OIDs (grantId, subjectUserId) from an X.509 certificate
+ * already parsed via @peculiar/x509.
+ *
+ * Returns `{ ok: true, value: MosaicOids }` on success, or
+ * `{ ok: false, error: <code>, detail? }` on any failure — never throws.
+ */
+export function extractMosaicOids(cert: X509Certificate): OidExtractionResult {
+  try {
+    const grantIdExt = cert.getExtension(OID_MOSAIC_GRANT_ID);
+    if (!grantIdExt) {
+      return { ok: false, error: 'MISSING_GRANT_ID' };
+    }
+
+    const subjectUserIdExt = cert.getExtension(OID_MOSAIC_SUBJECT_USER_ID);
+    if (!subjectUserIdExt) {
+      return { ok: false, error: 'MISSING_SUBJECT_USER_ID' };
+    }
+
+    const grantId = decodeUtf8StringTlv(grantIdExt.value);
+    const subjectUserId = decodeUtf8StringTlv(subjectUserIdExt.value);
+
+    return {
+      ok: true,
+      value: { grantId, subjectUserId },
+    };
+  } catch (err) {
+    return {
+      ok: false,
+      error: 'PARSE_ERROR',
+      detail: err instanceof Error ? err.message : String(err),
+    };
+  }
+}
+
+/**
+ * Parse a PEM-encoded certificate and extract Mosaic OIDs.
+ * Returns an OidExtractionResult — never throws.
+ */
+export function extractMosaicOidsFromPem(certPem: string): OidExtractionResult {
+  let cert: X509Certificate;
+  try {
+    cert = new X509Certificate(certPem);
+  } catch (err) {
+    return {
+      ok: false,
+      error: 'PARSE_ERROR',
+      detail: err instanceof Error ? err.message : String(err),
+    };
+  }
+  return extractMosaicOids(cert);
+}

apps/gateway/src/federation/server/__tests__/federation-auth.guard.spec.ts

@@ -0,0 +1,521 @@
+/**
+ * Unit tests for FederationAuthGuard (FED-M3-03).
+ *
+ * Coverage:
+ *  - Missing cert (no TLS socket / no getPeerCertificate) → 401
+ *  - Cert parse failure (corrupt DER raw bytes) → 401
+ *  - Missing grantId OID → 401
+ *  - Missing subjectUserId OID → 401
+ *  - Grant not found (GrantsService throws NotFoundException) → 403
+ *  - Grant in `pending` status → 403
+ *  - Grant in `revoked` status → 403
+ *  - Grant in `expired` status → 403
+ *  - Cert serial mismatch → 403
+ *  - Happy path: active grant + matching cert serial → context attached, returns true
+ */
+
+import 'reflect-metadata';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import type { ExecutionContext } from '@nestjs/common';
+import { NotFoundException } from '@nestjs/common';
+import { FederationAuthGuard } from '../federation-auth.guard.js';
+import { makeMosaicIssuedCert } from '../../__tests__/helpers/test-cert.js';
+import type { GrantsService, GrantWithPeer } from '../../grants.service.js';
+
+// ---------------------------------------------------------------------------
+// Test constants
+// ---------------------------------------------------------------------------
+
+const GRANT_ID = 'a1111111-1111-1111-1111-111111111111';
+const USER_ID = 'b2222222-2222-2222-2222-222222222222';
+const PEER_ID = 'c3333333-3333-3333-3333-333333333333';
+
+// Node.js TLS serialNumber is uppercase hex (no colons)
+const CERT_SERIAL_HEX = '01';
+
+const VALID_SCOPE = { resources: ['tasks'], max_rows_per_query: 100 };
+
+// ---------------------------------------------------------------------------
+// Mock builders
+// ---------------------------------------------------------------------------
+
+/**
+ * Build a minimal GrantWithPeer-shaped mock.
+ */
+function makeGrantWithPeer(overrides: Partial<GrantWithPeer> = {}): GrantWithPeer {
+  return {
+    id: GRANT_ID,
+    peerId: PEER_ID,
+    subjectUserId: USER_ID,
+    scope: VALID_SCOPE,
+    status: 'active',
+    expiresAt: null,
+    createdAt: new Date('2026-01-01T00:00:00Z'),
+    revokedAt: null,
+    revokedReason: null,
+    peer: {
+      id: PEER_ID,
+      commonName: 'test-peer',
+      displayName: 'Test Peer',
+      certPem: '',
+      certSerial: CERT_SERIAL_HEX,
+      certNotAfter: new Date(Date.now() + 86_400_000),
+      clientKeyPem: null,
+      state: 'active',
+      endpointUrl: null,
+      lastSeenAt: null,
+      createdAt: new Date('2026-01-01T00:00:00Z'),
+      revokedAt: null,
+    },
+    ...overrides,
+  };
+}
+
+/**
+ * Build a mock ExecutionContext with a pre-built TLS peer certificate.
+ *
+ * `certPem` — PEM string to present as the raw DER cert (converted to Buffer).
+ *             Pass null to simulate "no cert presented".
+ * `certSerialHex` — serialNumber string returned by the TLS socket.
+ *                   Node.js returns uppercase hex.
+ * `hasTlsSocket` — if false, raw.socket has no getPeerCertificate (plain HTTP).
+ */
+function makeContext(opts: {
+  certPem: string | null;
+  certSerialHex?: string;
+  hasTlsSocket?: boolean;
+}): {
+  ctx: ExecutionContext;
+  statusMock: ReturnType<typeof vi.fn>;
+  sendMock: ReturnType<typeof vi.fn>;
+} {
+  const { certPem, certSerialHex = CERT_SERIAL_HEX, hasTlsSocket = true } = opts;
+
+  // Build peerCert object that Node.js TLS socket.getPeerCertificate() returns
+  let peerCert: Record<string, unknown>;
+  if (certPem === null) {
+    // Simulate no cert: Node.js returns object with empty string fields
+    peerCert = { raw: null, serialNumber: '' };
+  } else {
+    // Convert PEM to DER Buffer (strip headers + base64 decode)
+    const b64 = certPem
+      .replace(/-----BEGIN CERTIFICATE-----/, '')
+      .replace(/-----END CERTIFICATE-----/, '')
+      .replace(/\s+/g, '');
+    const raw = Buffer.from(b64, 'base64');
+    peerCert = { raw, serialNumber: certSerialHex };
+  }
+
+  const getPeerCertificate = vi.fn().mockReturnValue(peerCert);
+
+  const socket = hasTlsSocket ? { getPeerCertificate } : {}; // No getPeerCertificate → non-TLS
+
+  // Fastify reply mocks
+  const sendMock = vi.fn().mockReturnValue(undefined);
+  const headerMock = vi.fn().mockReturnValue({ send: sendMock });
+  const statusMock = vi.fn().mockReturnValue({ header: headerMock });
+
+  const request = {
+    raw: {
+      socket,
+    },
+  };
+
+  const reply = {
+    status: statusMock,
+  };
+
+  const ctx = {
+    switchToHttp: () => ({
+      getRequest: () => request,
+      getResponse: () => reply,
+    }),
+  } as unknown as ExecutionContext;
+
+  return { ctx, statusMock, sendMock };
+}
+
+/**
+ * Build a mock GrantsService.
+ */
+function makeGrantsService(
+  overrides: Partial<Pick<GrantsService, 'getGrantWithPeer'>> = {},
+): GrantsService {
+  return {
+    getGrantWithPeer: vi.fn().mockResolvedValue(makeGrantWithPeer()),
+    ...overrides,
+  } as unknown as GrantsService;
+}
+
+// ---------------------------------------------------------------------------
+// Test suite
+// ---------------------------------------------------------------------------
+
+describe('FederationAuthGuard', () => {
+  let certPem: string;
+
+  beforeEach(async () => {
+    // Generate a real Mosaic-issued cert with the standard OIDs
+    certPem = await makeMosaicIssuedCert({ grantId: GRANT_ID, subjectUserId: USER_ID });
+  });
+
+  // ── 401: No TLS socket ────────────────────────────────────────────────────
+
+  it('returns 401 when there is no TLS socket (plain HTTP connection)', async () => {
+    const { ctx, statusMock, sendMock } = makeContext({
+      certPem: certPem,
+      hasTlsSocket: false,
+    });
+
+    const guard = new FederationAuthGuard(makeGrantsService());
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(401);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'unauthorized', message: expect.any(String) }),
+      }),
+    );
+  });
+
+  // ── 401: Cert not presented ───────────────────────────────────────────────
+
+  it('returns 401 when the peer did not present a certificate', async () => {
+    const { ctx, statusMock, sendMock } = makeContext({ certPem: null });
+
+    const guard = new FederationAuthGuard(makeGrantsService());
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(401);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'unauthorized', message: expect.any(String) }),
+      }),
+    );
+  });
+
+  // ── 401: Cert parse failure ───────────────────────────────────────────────
+
+  it('returns 401 when the certificate DER bytes are corrupt', async () => {
+    // Build context with a cert that has garbage DER bytes
+    const corruptPem = '-----BEGIN CERTIFICATE-----\naW52YWxpZA==\n-----END CERTIFICATE-----';
+    const { ctx, statusMock, sendMock } = makeContext({ certPem: corruptPem });
+
+    const guard = new FederationAuthGuard(makeGrantsService());
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(401);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'unauthorized', message: expect.any(String) }),
+      }),
+    );
+  });
+
+  // ── 401: Missing grantId OID ─────────────────────────────────────────────
+
+  it('returns 401 when the cert is missing the grantId OID', async () => {
+    // makeSelfSignedCert produces a cert without any Mosaic OIDs
+    const { makeSelfSignedCert } = await import('../../__tests__/helpers/test-cert.js');
+    const plainCert = await makeSelfSignedCert();
+    const { ctx, statusMock, sendMock } = makeContext({ certPem: plainCert });
+
+    const guard = new FederationAuthGuard(makeGrantsService());
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(401);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'unauthorized', message: expect.any(String) }),
+      }),
+    );
+  });
+
+  // ── 401: Missing subjectUserId OID ───────────────────────────────────────
+
+  it('returns 401 when the cert has grantId OID but is missing subjectUserId OID', async () => {
+    // Build a cert with only the grantId OID by importing cert generator internals
+    const { webcrypto } = await import('node:crypto');
+    const {
+      X509CertificateGenerator,
+      Extension,
+      KeyUsagesExtension,
+      KeyUsageFlags,
+      BasicConstraintsExtension,
+      cryptoProvider,
+    } = await import('@peculiar/x509');
+
+    cryptoProvider.set(webcrypto as unknown as Parameters<typeof cryptoProvider.set>[0]);
+
+    const alg = { name: 'ECDSA', namedCurve: 'P-256', hash: 'SHA-256' } as const;
+    const keys = await webcrypto.subtle.generateKey(alg, false, ['sign', 'verify']);
+    const now = new Date();
+    const tomorrow = new Date(now.getTime() + 86_400_000);
+
+    // Encode grantId only — missing subjectUserId extension
+    const utf8 = new TextEncoder().encode(GRANT_ID);
+    const encoded = new Uint8Array(2 + utf8.length);
+    encoded[0] = 0x0c;
+    encoded[1] = utf8.length;
+    encoded.set(utf8, 2);
+
+    const cert = await X509CertificateGenerator.createSelfSigned({
+      serialNumber: '01',
+      name: 'CN=partial-oid-test',
+      notBefore: now,
+      notAfter: tomorrow,
+      signingAlgorithm: alg,
+      keys,
+      extensions: [
+        new BasicConstraintsExtension(false),
+        new KeyUsagesExtension(KeyUsageFlags.digitalSignature),
+        new Extension('1.3.6.1.4.1.99999.1', false, encoded), // grantId only
+      ],
+    });
+
+    const { ctx, statusMock, sendMock } = makeContext({ certPem: cert.toString('pem') });
+
+    const guard = new FederationAuthGuard(makeGrantsService());
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(401);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'unauthorized', message: expect.any(String) }),
+      }),
+    );
+  });
+
+  // ── 403: Grant not found ─────────────────────────────────────────────────
+
+  it('returns 403 when the grantId from the cert does not exist in DB', async () => {
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi
+        .fn()
+        .mockRejectedValue(new NotFoundException(`Grant ${GRANT_ID} not found`)),
+    });
+
+    const { ctx, statusMock, sendMock } = makeContext({ certPem });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── 403: Grant in `pending` status ───────────────────────────────────────
+
+  it('returns 403 when the grant is in pending status', async () => {
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi.fn().mockResolvedValue(makeGrantWithPeer({ status: 'pending' })),
+    });
+
+    const { ctx, statusMock, sendMock } = makeContext({ certPem });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── 403: Grant in `revoked` status ───────────────────────────────────────
+
+  it('returns 403 when the grant is in revoked status', async () => {
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi
+        .fn()
+        .mockResolvedValue(makeGrantWithPeer({ status: 'revoked', revokedAt: new Date() })),
+    });
+
+    const { ctx, statusMock, sendMock } = makeContext({ certPem });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── 403: Grant in `expired` status ───────────────────────────────────────
+
+  it('returns 403 when the grant is in expired status', async () => {
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi.fn().mockResolvedValue(makeGrantWithPeer({ status: 'expired' })),
+    });
+
+    const { ctx, statusMock, sendMock } = makeContext({ certPem });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── 403: Cert serial mismatch ─────────────────────────────────────────────
+
+  it('returns 403 when the cert serial does not match the registered peer cert serial', async () => {
+    // Return a grant whose peer has a different stored serial
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi.fn().mockResolvedValue(
+        makeGrantWithPeer({
+          peer: {
+            id: PEER_ID,
+            commonName: 'test-peer',
+            displayName: 'Test Peer',
+            certPem: '',
+            certSerial: 'DEADBEEF', // different from CERT_SERIAL_HEX='01'
+            certNotAfter: new Date(Date.now() + 86_400_000),
+            clientKeyPem: null,
+            state: 'active',
+            endpointUrl: null,
+            lastSeenAt: null,
+            createdAt: new Date('2026-01-01T00:00:00Z'),
+            revokedAt: null,
+          },
+        }),
+      ),
+    });
+
+    // Context presents cert with serial '01' but DB has 'DEADBEEF'
+    const { ctx, statusMock, sendMock } = makeContext({ certPem, certSerialHex: '01' });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── 403: subjectUserId cert/DB mismatch (CRIT-1 regression test) ─────────
+
+  it('returns 403 when the cert subjectUserId does not match the DB grant subjectUserId', async () => {
+    // Build a cert that claims an attacker's subjectUserId
+    const attackerSubjectUserId = 'attacker-user-id';
+    const attackerCertPem = await makeMosaicIssuedCert({
+      grantId: GRANT_ID,
+      subjectUserId: attackerSubjectUserId,
+    });
+
+    // DB returns a grant with the legitimate USER_ID
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi.fn().mockResolvedValue(makeGrantWithPeer({ subjectUserId: USER_ID })),
+    });
+
+    // Cert presents attacker-user-id but DB has USER_ID — should be rejected
+    const { ctx, statusMock, sendMock } = makeContext({
+      certPem: attackerCertPem,
+      certSerialHex: CERT_SERIAL_HEX,
+    });
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(false);
+    expect(statusMock).toHaveBeenCalledWith(403);
+    expect(sendMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        error: expect.objectContaining({ code: 'forbidden', message: 'Federation access denied' }),
+      }),
+    );
+  });
+
+  // ── Happy path ────────────────────────────────────────────────────────────
+
+  it('returns true and attaches federationContext on happy path', async () => {
+    const grant = makeGrantWithPeer({
+      status: 'active',
+      peer: {
+        id: PEER_ID,
+        commonName: 'test-peer',
+        displayName: 'Test Peer',
+        certPem: '',
+        certSerial: CERT_SERIAL_HEX,
+        certNotAfter: new Date(Date.now() + 86_400_000),
+        clientKeyPem: null,
+        state: 'active',
+        endpointUrl: null,
+        lastSeenAt: null,
+        createdAt: new Date('2026-01-01T00:00:00Z'),
+        revokedAt: null,
+      },
+    });
+
+    const grantsService = makeGrantsService({
+      getGrantWithPeer: vi.fn().mockResolvedValue(grant),
+    });
+
+    // Build context manually to capture what gets set on request.federationContext
+    const b64 = certPem
+      .replace(/-----BEGIN CERTIFICATE-----/, '')
+      .replace(/-----END CERTIFICATE-----/, '')
+      .replace(/\s+/g, '');
+    const raw = Buffer.from(b64, 'base64');
+    const peerCert = { raw, serialNumber: CERT_SERIAL_HEX };
+
+    const sendMock = vi.fn().mockReturnValue(undefined);
+    const headerMock = vi.fn().mockReturnValue({ send: sendMock });
+    const statusMock = vi.fn().mockReturnValue({ header: headerMock });
+
+    const request: Record<string, unknown> = {
+      raw: {
+        socket: { getPeerCertificate: vi.fn().mockReturnValue(peerCert) },
+      },
+    };
+
+    const reply = { status: statusMock };
+
+    const ctx = {
+      switchToHttp: () => ({
+        getRequest: () => request,
+        getResponse: () => reply,
+      }),
+    } as unknown as ExecutionContext;
+
+    const guard = new FederationAuthGuard(grantsService);
+    const result = await guard.canActivate(ctx);
+
+    expect(result).toBe(true);
+    expect(statusMock).not.toHaveBeenCalled();
+
+    // Verify the context was attached correctly
+    expect(request['federationContext']).toEqual({
+      grantId: GRANT_ID,
+      subjectUserId: USER_ID,
+      peerId: PEER_ID,
+      scope: VALID_SCOPE,
+    });
+  });
+});

apps/gateway/src/federation/server/federation-auth.guard.ts

@@ -0,0 +1,212 @@
+/**
+ * FederationAuthGuard — NestJS CanActivate guard for inbound federation requests.
+ *
+ * Validates the mTLS client certificate presented by a peer gateway, extracts
+ * custom OIDs to identify the grant + subject user, loads the grant from DB,
+ * asserts it is active, and verifies the cert serial against the registered peer
+ * cert serial as a defense-in-depth measure.
+ *
+ * On success, attaches `request.federationContext` for downstream verb controllers.
+ * On failure, responds with the federation wire-format error envelope (not raw
+ * NestJS exception JSON) to match the federation protocol contract.
+ *
+ * ## Cert-serial check decision
+ * The guard validates that the inbound client cert's serial number matches the
+ * `certSerial` stored on the associated `federation_peers` row. This is a
+ * defense-in-depth measure: even if the mTLS handshake is compromised at the
+ * transport layer (e.g. misconfigured TLS terminator that forwards arbitrary
+ * client certs), an attacker cannot replay a cert with a different serial than
+ * what was registered during enrollment. This check is NOT loosened because:
+ *  1. It is O(1) — no additional DB round-trip (peerId is on the grant row,
+ *     so we join to federationPeers in the same query).
+ *  2. Cert renewal MUST update the stored serial — enforced by M6 scheduler.
+ *  3. The OID-only path (without serial check) would allow any cert from the
+ *     same CA bearing the same grantId OID to succeed after cert compromise.
+ *
+ * ## FastifyRequest typing path
+ * NestJS + Fastify wraps the raw Node.js IncomingMessage in a FastifyRequest.
+ * The underlying TLS socket is accessed via `request.raw.socket`, which is a
+ * `tls.TLSSocket` when the server is listening on HTTPS. In development/test
+ * the gateway may run over plain HTTP, in which case `getPeerCertificate` is
+ * not available. The guard safely handles both cases by checking for the
+ * method's existence before calling it.
+ *
+ * Note: The guard reads the peer certificate from the *already-completed*
+ * TLS handshake via `socket.getPeerCertificate(detailed=true)`. This relies
+ * on the server being configured with `requestCert: true` at the TLS level
+ * so Fastify/Node.js requests the client cert during the handshake.
+ * The guard does NOT verify the cert chain itself — that is handled by the
+ * TLS layer (Node.js `rejectUnauthorized: true` with the CA cert pinned).
+ */
+
+import {
+  type CanActivate,
+  type ExecutionContext,
+  Inject,
+  Injectable,
+  Logger,
+} from '@nestjs/common';
+import type { FastifyReply, FastifyRequest } from 'fastify';
+import * as tls from 'node:tls';
+import { X509Certificate } from '@peculiar/x509';
+import { FederationForbiddenError, FederationUnauthorizedError } from '@mosaicstack/types';
+import { extractMosaicOids } from '../oid.util.js';
+import { GrantsService } from '../grants.service.js';
+import type { FederationContext } from './federation-context.js';
+import './federation-context.js'; // side-effect import: applies FastifyRequest module augmentation
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+/**
+ * Send a federation wire-format error response directly on the Fastify reply.
+ * Returns false — callers return this value from canActivate.
+ */
+function sendFederationError(
+  reply: FastifyReply,
+  error: FederationUnauthorizedError | FederationForbiddenError,
+): boolean {
+  const statusCode = error.code === 'unauthorized' ? 401 : 403;
+  void reply.status(statusCode).header('content-type', 'application/json').send(error.toEnvelope());
+  return false;
+}
+
+// ---------------------------------------------------------------------------
+// Guard
+// ---------------------------------------------------------------------------
+
+@Injectable()
+export class FederationAuthGuard implements CanActivate {
+  private readonly logger = new Logger(FederationAuthGuard.name);
+
+  constructor(@Inject(GrantsService) private readonly grantsService: GrantsService) {}
+
+  async canActivate(context: ExecutionContext): Promise<boolean> {
+    const http = context.switchToHttp();
+    const request = http.getRequest<FastifyRequest>();
+    const reply = http.getResponse<FastifyReply>();
+
+    // ── Step 1: Extract peer certificate from TLS socket ────────────────────
+    const rawSocket = request.raw.socket;
+
+    // Check TLS socket: getPeerCertificate is only available on TLS connections.
+    if (
+      !rawSocket ||
+      typeof (rawSocket as Partial<tls.TLSSocket>).getPeerCertificate !== 'function'
+    ) {
+      this.logger.warn('No TLS socket — client cert unavailable (non-mTLS connection)');
+      return sendFederationError(
+        reply,
+        new FederationUnauthorizedError('Client certificate required'),
+      );
+    }
+
+    const tlsSocket = rawSocket as tls.TLSSocket;
+    const peerCert = tlsSocket.getPeerCertificate(true);
+
+    // Node.js returns an object with empty string fields when no cert was presented.
+    if (!peerCert || !peerCert.raw) {
+      this.logger.warn('Peer certificate not presented (mTLS handshake did not supply cert)');
+      return sendFederationError(
+        reply,
+        new FederationUnauthorizedError('Client certificate required'),
+      );
+    }
+
+    // ── Step 2: Parse the DER-encoded certificate via @peculiar/x509 ────────
+    let cert: X509Certificate;
+    try {
+      // peerCert.raw is a Buffer containing the DER-encoded cert
+      cert = new X509Certificate(peerCert.raw);
+    } catch (err) {
+      this.logger.warn(
+        `Failed to parse peer certificate: ${err instanceof Error ? err.message : String(err)}`,
+      );
+      return sendFederationError(
+        reply,
+        new FederationUnauthorizedError('Client certificate could not be parsed'),
+      );
+    }
+
+    // ── Step 3: Extract Mosaic custom OIDs ──────────────────────────────────
+    const oidResult = extractMosaicOids(cert);
+
+    if (!oidResult.ok) {
+      const message =
+        oidResult.error === 'MISSING_GRANT_ID'
+          ? 'Client certificate is missing required OID: mosaic_grant_id (1.3.6.1.4.1.99999.1)'
+          : oidResult.error === 'MISSING_SUBJECT_USER_ID'
+            ? 'Client certificate is missing required OID: mosaic_subject_user_id (1.3.6.1.4.1.99999.2)'
+            : `Client certificate OID extraction failed: ${oidResult.detail ?? 'unknown error'}`;
+      this.logger.warn(`OID extraction failure [${oidResult.error}]: ${message}`);
+      return sendFederationError(reply, new FederationUnauthorizedError(message));
+    }
+
+    const { grantId, subjectUserId } = oidResult.value;
+
+    // ── Step 4: Load grant from DB ───────────────────────────────────────────
+    let grant: Awaited<ReturnType<GrantsService['getGrantWithPeer']>>;
+    try {
+      grant = await this.grantsService.getGrantWithPeer(grantId);
+    } catch {
+      // getGrantWithPeer throws NotFoundException when not found
+      this.logger.warn(`Grant not found: ${grantId}`);
+      return sendFederationError(reply, new FederationForbiddenError('Federation access denied'));
+    }
+
+    // ── Step 5: Assert grant is active ──────────────────────────────────────
+    if (grant.status !== 'active') {
+      this.logger.warn(`Grant ${grantId} is not active — status=${grant.status}`);
+      return sendFederationError(reply, new FederationForbiddenError('Federation access denied'));
+    }
+
+    // ── Step 5b: Validate cert-extracted subjectUserId against DB (CRIT-1) ──
+    // The cert claim is untrusted input; the DB row is authoritative.
+    if (subjectUserId !== grant.subjectUserId) {
+      this.logger.warn(`subjectUserId mismatch for grant ${grantId}`);
+      return sendFederationError(reply, new FederationForbiddenError('Federation access denied'));
+    }
+
+    // ── Step 6: Defense-in-depth — cert serial must match registered peer ───
+    // The serial number from Node.js TLS is upper-case hex without colons.
+    // The @peculiar/x509 serialNumber is decimal. We compare using the native
+    // Node.js crypto cert serial which is uppercase hex, matching DB storage.
+    // Both are derived from the peerCert.serialNumber Node.js provides.
+    const inboundSerial: string = peerCert.serialNumber ?? '';
+
+    if (!grant.peer.certSerial) {
+      // Peer row exists but has no stored serial — something is wrong with enrollment
+      this.logger.error(`Peer ${grant.peerId} has no stored certSerial — enrollment incomplete`);
+      return sendFederationError(reply, new FederationForbiddenError('Federation access denied'));
+    }
+
+    // Normalize both to uppercase for comparison (Node.js serialNumber is
+    // already uppercase hex; DB value was stored from extractSerial() which
+    // returns crypto.X509Certificate.serialNumber — also uppercase hex).
+    if (inboundSerial.toUpperCase() !== grant.peer.certSerial.toUpperCase()) {
+      this.logger.warn(
+        `Cert serial mismatch for grant ${grantId}: ` +
+          `inbound=${inboundSerial} registered=${grant.peer.certSerial}`,
+      );
+      return sendFederationError(reply, new FederationForbiddenError('Federation access denied'));
+    }
+
+    // ── Step 7: Attach FederationContext to request ──────────────────────────
+    // Use grant.subjectUserId from DB (authoritative) — not the cert-extracted value.
+    const federationContext: FederationContext = {
+      grantId,
+      subjectUserId: grant.subjectUserId,
+      peerId: grant.peerId,
+      scope: grant.scope as Record<string, unknown>,
+    };
+
+    request.federationContext = federationContext;
+
+    this.logger.debug(
+      `Federation auth OK — grantId=${grantId} peerId=${grant.peerId} subjectUserId=${grant.subjectUserId}`,
+    );
+
+    return true;
+  }
+}

apps/gateway/src/federation/server/federation-context.ts

@@ -0,0 +1,39 @@
+/**
+ * FederationContext — attached to inbound federation requests after successful
+ * mTLS + grant validation by FederationAuthGuard.
+ *
+ * Downstream verb controllers access this via `request.federationContext`.
+ */
+
+/**
+ * Augment FastifyRequest so TypeScript knows about the federation context
+ * property that FederationAuthGuard attaches on success.
+ */
+declare module 'fastify' {
+  interface FastifyRequest {
+    federationContext?: FederationContext;
+  }
+}
+
+/**
+ * Typed context object attached to the request by FederationAuthGuard.
+ * Carries all data extracted from the mTLS cert + grant DB row needed
+ * by downstream federation verb handlers.
+ */
+export interface FederationContext {
+  /** The federation grant ID extracted from OID 1.3.6.1.4.1.99999.1 */
+  grantId: string;
+
+  /** The local subject user whose data is accessible under this grant */
+  subjectUserId: string;
+
+  /** The peer gateway ID (from the grant's peerId FK) */
+  peerId: string;
+
+  /**
+   * Grant scope — determines which resources the peer may query.
+   * Typed as Record<string, unknown> because the full scope schema lives in
+   * scope-schema.ts; downstream handlers should narrow via parseFederationScope.
+   */
+  scope: Record<string, unknown>;
+}

apps/gateway/src/federation/server/index.ts

@@ -0,0 +1,13 @@
+/**
+ * Federation server-side barrel — inbound request handling.
+ *
+ * Exports the mTLS auth guard and the FederationContext interface
+ * for use by verb controllers (M3-05/06/07).
+ *
+ * Usage:
+ *   import { FederationAuthGuard } from './server/index.js';
+ *   @UseGuards(FederationAuthGuard)
+ */
+
+export { FederationAuthGuard } from './federation-auth.guard.js';
+export type { FederationContext } from './federation-context.js';

docs/federation/MISSION-MANIFEST.md

@@ -7,11 +7,11 @@
 
 **ID:** federation-v1-20260419
 **Statement:** Jarvis operates across 3–4 workstations in two physical locations (home, USC). The user currently reaches back to a single jarvis-brain checkout from every session; a prior OpenBrain attempt caused cache, latency, and opacity pain. This mission builds asymmetric federation between Mosaic Stack gateways so that a session on a user's home gateway can query their work gateway in real time without data ever persisting across the boundary, with full multi-tenant isolation and standard-PKI (X.509 / Step-CA) trust management.
-**Phase:** M2 active — Step-CA + grant schema + admin CLI; parallel test-deploy workstream stood up
+**Phase:** M3 active — mTLS handshake + list/get/capabilities verbs + scope enforcement
-**Current Milestone:** FED-M2
+**Current Milestone:** FED-M3
-**Progress:** 1 / 7 milestones
+**Progress:** 2 / 7 milestones
 **Status:** active
-**Last Updated:** 2026-04-21 (M2 decomposed; mos-test-1/-2 designated as federation E2E test hosts)
+**Last Updated:** 2026-04-21 (M2 closed via PR #503, tag `fed-v0.2.0-m2`, issue #461 closed; M3 decomposed into 14 tasks)
 **Parent Mission:** None — new mission
 
 ## Test Infrastructure
@@ -63,8 +63,8 @@ Key design references:
 | #   | ID     | Name                                          | Status      | Branch             | Issue | Started    | Completed  |
 | --- | ------ | --------------------------------------------- | ----------- | ------------------ | ----- | ---------- | ---------- |
 | 1   | FED-M1 | Federated tier infrastructure                 | done        | (12 PRs #470-#481) | #460  | 2026-04-19 | 2026-04-19 |
-| 2   | FED-M2 | Step-CA + grant schema + admin CLI            | in-progress | (decomposition)    | #461  | 2026-04-21 | —          |
+| 2   | FED-M2 | Step-CA + grant schema + admin CLI            | done        | (PRs #483-#503)    | #461  | 2026-04-21 | 2026-04-21 |
-| 3   | FED-M3 | mTLS handshake + list/get + scope enforcement | not-started | —                  | #462  | —          | —          |
+| 3   | FED-M3 | mTLS handshake + list/get + scope enforcement | in-progress | (decomposition)    | #462  | 2026-04-21 | —          |
 | 4   | FED-M4 | search verb + audit log + rate limit          | not-started | —                  | #463  | —          | —          |
 | 5   | FED-M5 | Cache + offline degradation + OTEL            | not-started | —                  | #464  | —          | —          |
 | 6   | FED-M6 | Revocation + auto-renewal + CRL               | not-started | —                  | #465  | —          | —          |
@@ -86,16 +86,23 @@ Key design references:
 ## Session History
 
 | Session | Date                    | Runtime | Outcome                                                                                                                               |
-| ------- | ---------- | ------- | --------------------------------------------------------------------- |
+| ------- | ----------------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------- |
 | S1      | 2026-04-19              | claude  | PRD authored, MILESTONES decomposed, 7 issues filed                                                                                   |
 | S2-S4   | 2026-04-19              | claude  | FED-M1 complete: 12 tasks (PRs #470-#481) merged; tag `fed-v0.1.0-m1`                                                                 |
+| S5-S22  | 2026-04-19 → 2026-04-21 | claude  | FED-M2 complete: 13 tasks (PRs #483-#503) merged; tag `fed-v0.2.0-m2`; issue #461 closed. Step-CA + grant schema + admin CLI shipped. |
+| S23     | 2026-04-21              | claude  | M3 decomposed into 14 tasks in `docs/federation/TASKS.md`. Manifest M3 row → in-progress. Next: kickoff M3-01.                        |
 
 ## Next Step
 
-FED-M2 active. Decomposition landed in `docs/federation/TASKS.md` (M2-01..M2-13 code workstream + DEPLOY-01..DEPLOY-05 parallel test-deploy workstream, ~88K total). Tracking issue #482.
+FED-M3 active. Decomposition landed in `docs/federation/TASKS.md` (M3-01..M3-14, ~100K estimate). Tracking issue #462.
 
-Parallel execution plan:
+Execution plan (parallel where possible):
 
-- **CODE workstream**: M2-01 (DB migration) starts immediately — sonnet subagent on `feat/federation-m2-schema`. Then M2-02 → M2-09 sequentially with M2-04/M2-05/M2-06/M2-07 having interleaved CA/storage/grant dependencies.
+- **Foundation**: M3-01 (DTOs in `packages/types/src/federation/`) starts immediately — sonnet subagent on `feat/federation-m3-types`. Blocks all server + client work.
-- **DEPLOY workstream**: DEPLOY-01 (image verify) → DEPLOY-02 (stack template) → DEPLOY-03/04 (mos-test-1/-2 deploy) → DEPLOY-05 (TEST-INFRA.md). Gated on Portainer wrapper PR (`PORTAINER_INSECURE` flag) merging first.
+- **Server stream** (after M3-01): M3-03 (AuthGuard) + M3-04 (ScopeService) in series, then M3-05 / M3-06 / M3-07 (verbs) in parallel.
-- **Re-converge** at M2-10 (E2E test) once both workstreams ready.
+- **Client stream** (after M3-01, parallel with server): M3-08 (FederationClient) → M3-09 (QuerySourceService).
+- **Harness** (parallel with everything): M3-02 (`tools/federation-harness/`) — needed for M3-11.
+- **Test gates**: M3-10 (Integration) → M3-11 (E2E with harness) → M3-12 (Independent security review, two rounds budgeted).
+- **Close**: M3-13 (Docs) → M3-14 (release tag `fed-v0.3.0-m3`, close #462).
+
+**Test-bed fallback:** `mos-test-1/-2` deploy is still blocked on `FED-M2-DEPLOY-IMG-FIX`. The harness in M3-02 ships a local two-gateway docker-compose so M3-11 is not blocked. Production-host validation is M7's responsibility (PRD AC-12).

docs/federation/TASKS.md

@@ -85,7 +85,38 @@ Goal: An admin can create a federation grant; counterparty enrolls; cert is sign
 
 ## Milestone 3 — mTLS handshake + list/get + scope enforcement (FED-M3)
 
-_Deferred. Issue #462._
+Goal: Two federated gateways exchange real data over mTLS. Inbound requests pass through cert validation → grant lookup → scope enforcement → native RBAC → response. `list`, `get`, and `capabilities` verbs land. The federation E2E harness (`tools/federation-harness/`) is the new permanent test bed for M3+ and is gated on every milestone going forward.
+
+> **Critical trust boundary.** Every 401/403 path needs a test. Code review is non-negotiable; M3-12 budgets two review rounds.
+>
+> **Tracking issue:** #462.
+
+| id        | status      | description                                                                                                                                                                                                                                                                                            | issue | agent  | branch                               | depends_on       | estimate | notes                                                                                                                                                    |
+| --------- | ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ----- | ------ | ------------------------------------ | ---------------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| FED-M3-01 | not-started | `packages/types/src/federation/` — request/response DTOs for `list`, `get`, `capabilities` verbs. Wire-format zod schemas + inferred TS types. Includes `FederationRequest`, `FederationListResponse<T>`, `FederationGetResponse<T>`, `FederationCapabilitiesResponse`, error envelope, `_source` tag. | #462  | sonnet | feat/federation-m3-types             | —                | 4K       | Reusable from gateway server + client + harness. Pure types — no I/O, no NestJS.                                                                         |
+| FED-M3-02 | not-started | `tools/federation-harness/` scaffold: `docker-compose.two-gateways.yml` (Server A + Server B + step-CA), `seed.ts` (provisions grants, peers, sample tasks/notes/credentials per scope variant), `harness.ts` helper (boots stack, returns typed clients). README documents harness use.               | #462  | sonnet | feat/federation-m3-harness           | DEPLOY-04 (soft) | 8K       | Falls back to local docker-compose if `mos-test-1/-2` not yet redeployed (DEPLOY chain blocked on IMG-FIX). Permanent test infra used by M3+.            |
+| FED-M3-03 | not-started | `apps/gateway/src/federation/server/federation-auth.guard.ts` (NestJS guard). Validates inbound client cert from Fastify TLS context, extracts `grantId` + `subjectUserId` from custom OIDs, loads grant from DB, asserts `status='active'`, attaches `FederationContext` to request.                  | #462  | sonnet | feat/federation-m3-auth-guard        | M3-01            | 8K       | Reuses OID parsing logic mirrored from `ca.service.ts` post-issuance verification. 401 on malformed/missing OIDs; 403 on revoked/expired/missing grant.  |
+| FED-M3-04 | not-started | `apps/gateway/src/federation/server/scope.service.ts`. Pipeline: (1) resource allowlist + excluded check, (2) native RBAC eval as `subjectUserId`, (3) scope filter intersection (`include_teams`, `include_personal`), (4) `max_rows_per_query` cap. Pure service — DB calls injected.                | #462  | sonnet | feat/federation-m3-scope-service     | M3-01            | 10K      | Hardest correctness target in M3. Reuses `parseFederationScope` (M2-03). Returns either `{ allowed: true, filter }` or structured deny reason for audit. |
+| FED-M3-05 | not-started | `apps/gateway/src/federation/server/verbs/list.controller.ts`. Wires AuthGuard → ScopeService → tasks/notes/memory query layer; applies row cap; tags rows with `_source`. Resource selector via path param.                                                                                           | #462  | sonnet | feat/federation-m3-verb-list         | M3-03, M3-04     | 6K       | Routes: `POST /api/federation/v1/list/:resource`. No body persistence. Audit write deferred to M4.                                                       |
+| FED-M3-06 | not-started | `apps/gateway/src/federation/server/verbs/get.controller.ts`. Single-resource fetch by id; same pipeline as list. 404 on not-found, 403 on RBAC/scope deny — both audited the same way.                                                                                                                | #462  | sonnet | feat/federation-m3-verb-get          | M3-03, M3-04     | 6K       | `POST /api/federation/v1/get/:resource/:id`. Mirrors list controller patterns.                                                                           |
+| FED-M3-07 | not-started | `apps/gateway/src/federation/server/verbs/capabilities.controller.ts`. Read-only enumeration: returns `{ resources, excluded_resources, max_rows_per_query, supported_verbs }` derived from grant scope. Always allowed for an active grant — no RBAC eval.                                            | #462  | sonnet | feat/federation-m3-verb-capabilities | M3-03            | 4K       | `GET /api/federation/v1/capabilities`. Smallest verb; useful sanity check that mTLS + auth guard work end-to-end.                                        |
+| FED-M3-08 | not-started | `apps/gateway/src/federation/client/federation-client.service.ts`. Outbound mTLS dialer: picks `(certPem, sealed clientKey)` from `federation_peers`, unwraps key, builds undici Agent with mTLS, calls peer verb, parses typed response, wraps non-2xx into `FederationClientError`.                  | #462  | sonnet | feat/federation-m3-client            | M3-01            | 8K       | Independent of server stream — can land in parallel with M3-03/04. Cert/key cached per-peer; flushed by future M5/M6 logic.                              |
+| FED-M3-09 | not-started | `apps/gateway/src/federation/client/query-source.service.ts`. Accepts `source: "local" \| "federated:<host>" \| "all"` from gateway query layer; for `"all"` fans out to local + each peer in parallel; merges results; tags every row with `_source`.                                                 | #462  | sonnet | feat/federation-m3-query-source      | M3-08            | 8K       | Per-peer failure surfaces as `_partial: true` in response, not hard failure (sets up M5 offline UX). M5 adds caching + circuit breaker on top.           |
+| FED-M3-10 | not-started | Integration tests for MILESTONES.md M3 acceptance #6 (malformed OIDs → 401; valid cert + revoked grant → 403) and #7 (`max_rows_per_query` cap). Real PG, mocked TLS context (Fastify req shim).                                                                                                       | #462  | sonnet | feat/federation-m3-integration       | M3-05, M3-06     | 8K       | Vitest profile gated by `FEDERATED_INTEGRATION=1`. Single-gateway suite; no harness required.                                                            |
+| FED-M3-11 | not-started | E2E tests for MILESTONES.md M3 acceptance #1, #2, #3, #4, #5, #8, #9, #10 (8 cases). Uses harness from M3-02; two real gateways, real Step-CA, real mTLS. Each test asserts both happy-path response and audit/no-persist invariants.                                                                  | #462  | sonnet | feat/federation-m3-e2e               | M3-02, M3-09     | 12K      | Largest single task. Each acceptance gets its own `it(...)` for clear failure attribution.                                                               |
+| FED-M3-12 | not-started | Independent security review (sonnet, not author of M3-03/04/05/06/07/08/09): focus on cert-SAN spoofing, OID extraction edge cases, scope-bypass via filter manipulation, RBAC-bypass via subjectUser swap, response leakage when scope deny.                                                          | #462  | sonnet | feat/federation-m3-security-review   | M3-11            | 10K      | Two review rounds budgeted. PRD requires explicit test for every 401/403 path — review verifies coverage.                                                |
+| FED-M3-13 | not-started | Docs update: `docs/federation/SETUP.md` mTLS handshake section, new `docs/federation/HARNESS.md` for federation-harness usage, OID reference table in SETUP.md, scope enforcement pipeline diagram. Runbook still M7-deferred.                                                                         | #462  | haiku  | feat/federation-m3-docs              | M3-12            | 5K       | One ASCII diagram for the auth-guard → scope → RBAC pipeline; helps future reviewers reason about denial paths.                                          |
+| FED-M3-14 | not-started | PR aggregate close, CI green, merge to main, close #462. Release tag `fed-v0.3.0-m3`. Update mission manifest M3 row → done; M4 row → in-progress when work begins.                                                                                                                                    | #462  | sonnet | chore/federation-m3-close            | M3-13            | 3K       | Same close pattern as M1-12 / M2-13.                                                                                                                     |
+
+**M3 estimate:** ~100K tokens (vs MILESTONES.md 40K — same per-task breakdown pattern as M1/M2: tests, review, and docs split out from implementation cost). Largest milestone in the federation mission.
+
+**Parallelization opportunities:**
+
+- M3-08 (client) can land in parallel with M3-03/M3-04 (server pipeline) — they only share DTOs from M3-01.
+- M3-02 (harness) can land in parallel with everything except M3-11.
+- M3-05/M3-06/M3-07 (verbs) are independent of each other once M3-03/M3-04 land.
+
+**Test bed fallback:** If `mos-test-1.woltje.com` / `mos-test-2.woltje.com` are still blocked on `FED-M2-DEPLOY-IMG-FIX` when M3-11 is ready to run, the harness's local `docker-compose.two-gateways.yml` is a sufficient stand-in. Production-host validation moves to M7 acceptance suite (PRD AC-12).
 
 ## Milestone 4 — search + audit + rate limit (FED-M4)
 

docs/scratchpads/mvp-20260312.md

@@ -612,3 +612,44 @@ Independent security review surfaced three high-impact and four medium findings;
 7. DEPLOY-03/04 acceptance probes (`mosaic gateway doctor --json`, pgvector `vector(3)` round-trip)
 8. DEPLOY-05: author `docs/federation/TEST-INFRA.md`
 9. M2-02 (Step-CA sidecar) kicks off after image health is green
+
+### Session 23 — 2026-04-21 — M2 close + M3 decomposition
+
+**Closed at compaction boundary:** all 13 M2 tasks done, PRs #494–#503 merged to `main`, tag `fed-v0.2.0-m2` published, Gitea release notes posted, issue #461 closed. Main at `4ece6dc6`.
+
+**M2 hardening landed in PR #501** (security review remediation):
+
+- CRIT-1: post-issuance OID verification in `ca.service.ts` (rejects cert if `mosaic_grant_id` / `mosaic_subject_user_id` extensions missing or mismatched)
+- CRIT-2: atomic activation guard `WHERE status='pending'` on grant + `WHERE state='pending'` on peer; throws `ConflictException` if lost race
+- HIGH-2: removed try/catch fallback in `extractCertNotAfter` — parse failures propagate as 500 (no silent 90-day default)
+- HIGH-4: token slice for logging (`${token.slice(0, 8)}...`) — no full token in stdout
+- HIGH-5: `redeem()` wrapped in try/catch with best-effort failure audit; uses `null` (not `'unknown'`) for nullable UUID FK fallback
+- MED-3: `createToken` validates `grant.peerId === dto.peerId`; `BadRequestException` on mismatch
+
+**Remaining M2 security findings deferred to M3+:**
+
+- HIGH-1: peerId/subjectUserId tenancy validation on `createGrant` (M3 ScopeService work surfaces this)
+- HIGH-3: Step-CA cert SHA-256 fingerprint pinning (M5 cert handling)
+- MED-1: token entropy already 32 bytes — wontfix
+- MED-2: per-route rate limit on enrollment endpoint (M4 rate limit work)
+- MED-4: CSR CN binding to peer's commonName (M3 AuthGuard work)
+
+**M3 decomposition landed in this session:**
+
+- 14 tasks (M3-01..M3-14), ~100K estimate
+- Structure mirrors M1/M2 pattern: foundation → server stream + client stream + harness in parallel → integration → E2E → security review → docs → close
+- M3-02 ships local two-gateway docker-compose (`tools/federation-harness/`) so M3-11 E2E is not blocked on the Portainer test bed (which is still blocked on `FED-M2-DEPLOY-IMG-FIX`)
+
+**Subagent doctrine retained from M2:**
+
+- All worker subagents use `isolation: "worktree"` to prevent branch-race incidents
+- Code review is independent (different subagent, no overlap with author of work)
+- `tea pr create --repo mosaicstack/stack --login mosaicstack` is the working PR-create path; `pr-create.sh` has shell-quoting bugs (followup #45 if not already filed)
+- Cost tier: foundational implementation = sonnet, docs = haiku, complex multi-file architecture (security review, scope service) = sonnet with two review rounds
+
+**Next concrete step:**
+
+1. PR for the M3 planning artifact (this commit) — branch `docs/federation-m3-planning`
+2. After merge, kickoff M3-01 (DTOs) on `feat/federation-m3-types` with sonnet subagent in worktree
+3. Once M3-01 lands, fan out: M3-02 (harness) || M3-03 (AuthGuard) → M3-04 (ScopeService) || M3-08 (FederationClient)
+4. Re-converge at M3-10 (Integration) → M3-11 (E2E)

eslint.config.mjs

@@ -30,6 +30,7 @@ export default tseslint.config(
             'apps/gateway/vitest.config.ts',
             'packages/storage/vitest.config.ts',
             'packages/mosaic/__tests__/*.ts',
+            'tools/federation-harness/*.ts',
           ],
         },
       },

packages/types/package.json

@@ -26,7 +26,8 @@
   },
   "dependencies": {
     "class-transformer": "^0.5.1",
-    "class-validator": "^0.15.1"
+    "class-validator": "^0.15.1",
+    "zod": "^4.3.6"
   },
   "publishConfig": {
     "registry": "https://git.mosaicstack.dev/api/packages/mosaicstack/npm/",

packages/types/src/federation/__tests__/federation.spec.ts

@@ -0,0 +1,435 @@
+/**
+ * Unit tests for federation wire-format DTOs.
+ *
+ * Coverage:
+ *  - FederationRequestSchema  (valid + invalid)
+ *  - FederationListResponseSchema factory
+ *  - FederationGetResponseSchema factory
+ *  - FederationCapabilitiesResponseSchema
+ *  - FederationErrorEnvelopeSchema + error code exhaustiveness
+ *  - FederationError exception hierarchy
+ *  - tagWithSource helper round-trip
+ *  - SourceTagSchema
+ */
+
+import { describe, expect, it } from 'vitest';
+import { z } from 'zod';
+
+import {
+  FEDERATION_ERROR_CODES,
+  FEDERATION_VERBS,
+  FederationCapabilitiesResponseSchema,
+  FederationError,
+  FederationErrorEnvelopeSchema,
+  FederationForbiddenError,
+  FederationInternalError,
+  FederationInvalidRequestError,
+  FederationNotFoundError,
+  FederationRateLimitedError,
+  FederationRequestSchema,
+  FederationScopeViolationError,
+  FederationUnauthorizedError,
+  FederationGetResponseSchema,
+  FederationListResponseSchema,
+  SOURCE_LOCAL,
+  SourceTagSchema,
+  parseFederationErrorEnvelope,
+  tagWithSource,
+} from '../index.js';
+
+// ---------------------------------------------------------------------------
+// Verbs
+// ---------------------------------------------------------------------------
+
+describe('FEDERATION_VERBS', () => {
+  it('contains exactly list, get, capabilities', () => {
+    expect(FEDERATION_VERBS).toEqual(['list', 'get', 'capabilities']);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationRequestSchema
+// ---------------------------------------------------------------------------
+
+describe('FederationRequestSchema', () => {
+  it('accepts a minimal valid list request', () => {
+    const result = FederationRequestSchema.safeParse({ verb: 'list', resource: 'tasks' });
+    expect(result.success).toBe(true);
+  });
+
+  it('accepts a get request with cursor and params', () => {
+    const result = FederationRequestSchema.safeParse({
+      verb: 'get',
+      resource: 'notes',
+      cursor: 'abc123',
+      params: { filter: 'mine' },
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.cursor).toBe('abc123');
+      expect(result.data.params?.['filter']).toBe('mine');
+    }
+  });
+
+  it('accepts a capabilities request', () => {
+    const result = FederationRequestSchema.safeParse({ verb: 'capabilities', resource: 'tasks' });
+    expect(result.success).toBe(true);
+  });
+
+  it('rejects an unknown verb', () => {
+    const result = FederationRequestSchema.safeParse({ verb: 'search', resource: 'tasks' });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects an empty resource string', () => {
+    const result = FederationRequestSchema.safeParse({ verb: 'list', resource: '' });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects a missing verb', () => {
+    const result = FederationRequestSchema.safeParse({ resource: 'tasks' });
+    expect(result.success).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationListResponseSchema factory
+// ---------------------------------------------------------------------------
+
+describe('FederationListResponseSchema', () => {
+  const ItemSchema = z.object({ id: z.string(), name: z.string() });
+  const ListSchema = FederationListResponseSchema(ItemSchema);
+
+  it('accepts a valid list envelope', () => {
+    const result = ListSchema.safeParse({
+      items: [{ id: '1', name: 'Task A' }],
+      nextCursor: 'page2',
+      _partial: false,
+      _truncated: false,
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.items).toHaveLength(1);
+      expect(result.data.nextCursor).toBe('page2');
+    }
+  });
+
+  it('accepts a minimal envelope with empty items', () => {
+    const result = ListSchema.safeParse({ items: [] });
+    expect(result.success).toBe(true);
+  });
+
+  it('rejects when items is missing', () => {
+    const result = ListSchema.safeParse({ nextCursor: 'x' });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects when an item fails validation', () => {
+    const result = ListSchema.safeParse({ items: [{ id: 1, name: 'bad' }] });
+    expect(result.success).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationGetResponseSchema factory
+// ---------------------------------------------------------------------------
+
+describe('FederationGetResponseSchema', () => {
+  const ItemSchema = z.object({ id: z.string() });
+  const GetSchema = FederationGetResponseSchema(ItemSchema);
+
+  it('accepts a found item', () => {
+    const result = GetSchema.safeParse({ item: { id: 'abc' } });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.item).toEqual({ id: 'abc' });
+    }
+  });
+
+  it('accepts null item (not found)', () => {
+    const result = GetSchema.safeParse({ item: null });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.item).toBeNull();
+    }
+  });
+
+  it('rejects when item is missing', () => {
+    const result = GetSchema.safeParse({});
+    expect(result.success).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationCapabilitiesResponseSchema
+// ---------------------------------------------------------------------------
+
+describe('FederationCapabilitiesResponseSchema', () => {
+  it('accepts a valid capabilities response', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks', 'notes'],
+      excluded_resources: ['credentials'],
+      max_rows_per_query: 500,
+      supported_verbs: ['list', 'get', 'capabilities'],
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.max_rows_per_query).toBe(500);
+    }
+  });
+
+  it('accepts a response with filters field', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks', 'notes'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+      filters: {
+        tasks: { include_teams: ['team-a'], include_personal: true },
+        notes: { include_personal: false },
+      },
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.filters?.['tasks']?.include_teams).toEqual(['team-a']);
+    }
+  });
+
+  it('accepts a response with partial filters (only include_teams)', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 50,
+      supported_verbs: ['list'],
+      filters: { tasks: { include_teams: ['eng'] } },
+    });
+    expect(result.success).toBe(true);
+  });
+
+  it('accepts a response with rate_limit (M4 full shape)', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+      rate_limit: { limit_per_minute: 60, remaining: 55, reset_at: '2026-04-23T12:00:00Z' },
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.rate_limit?.limit_per_minute).toBe(60);
+      expect(result.data.rate_limit?.remaining).toBe(55);
+    }
+  });
+
+  it('accepts a response with rate_limit (M3 minimal — limit_per_minute only)', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+      rate_limit: { limit_per_minute: 120 },
+    });
+    expect(result.success).toBe(true);
+  });
+
+  it('accepts a response without rate_limit (field is optional)', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+    });
+    expect(result.success).toBe(true);
+    if (result.success) {
+      expect(result.data.rate_limit).toBeUndefined();
+    }
+  });
+
+  it('rejects rate_limit with non-positive limit_per_minute', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+      rate_limit: { limit_per_minute: 0 },
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects rate_limit with invalid reset_at datetime', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+      rate_limit: { limit_per_minute: 60, reset_at: 'not-a-datetime' },
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects supported_verbs with an invalid verb (MED-3 enum guard)', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['invalid_verb'],
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects empty resources array', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: [],
+      excluded_resources: [],
+      max_rows_per_query: 100,
+      supported_verbs: ['list'],
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it('rejects non-integer max_rows_per_query', () => {
+    const result = FederationCapabilitiesResponseSchema.safeParse({
+      resources: ['tasks'],
+      excluded_resources: [],
+      max_rows_per_query: 1.5,
+      supported_verbs: ['list'],
+    });
+    expect(result.success).toBe(false);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationErrorEnvelopeSchema + error code exhaustiveness
+// ---------------------------------------------------------------------------
+
+describe('FederationErrorEnvelopeSchema', () => {
+  it('accepts each valid error code', () => {
+    for (const code of FEDERATION_ERROR_CODES) {
+      const result = FederationErrorEnvelopeSchema.safeParse({
+        error: { code, message: 'test' },
+      });
+      expect(result.success, `code ${code} should be valid`).toBe(true);
+    }
+  });
+
+  it('rejects an unknown error code', () => {
+    const result = FederationErrorEnvelopeSchema.safeParse({
+      error: { code: 'unknown_code', message: 'test' },
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it('accepts optional details field', () => {
+    const result = FederationErrorEnvelopeSchema.safeParse({
+      error: { code: 'forbidden', message: 'nope', details: { grantId: 'xyz' } },
+    });
+    expect(result.success).toBe(true);
+  });
+
+  it('rejects when message is missing', () => {
+    const result = FederationErrorEnvelopeSchema.safeParse({ error: { code: 'not_found' } });
+    expect(result.success).toBe(false);
+  });
+});
+
+describe('parseFederationErrorEnvelope', () => {
+  it('returns a typed envelope for valid input', () => {
+    const env = parseFederationErrorEnvelope({ error: { code: 'not_found', message: 'gone' } });
+    expect(env.error.code).toBe('not_found');
+  });
+
+  it('throws for invalid input', () => {
+    expect(() => parseFederationErrorEnvelope({ bad: 'shape' })).toThrow();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// FederationError exception hierarchy
+// ---------------------------------------------------------------------------
+
+describe('FederationError hierarchy', () => {
+  const cases: Array<[string, FederationError]> = [
+    ['unauthorized', new FederationUnauthorizedError()],
+    ['forbidden', new FederationForbiddenError()],
+    ['not_found', new FederationNotFoundError()],
+    ['rate_limited', new FederationRateLimitedError()],
+    ['scope_violation', new FederationScopeViolationError()],
+    ['invalid_request', new FederationInvalidRequestError()],
+    ['internal_error', new FederationInternalError()],
+  ];
+
+  it.each(cases)('code %s is an instance of FederationError', (_code, err) => {
+    expect(err).toBeInstanceOf(FederationError);
+    expect(err).toBeInstanceOf(Error);
+  });
+
+  it.each(cases)('code %s has correct code property', (code, err) => {
+    expect(err.code).toBe(code);
+  });
+
+  it('toEnvelope serialises to wire format', () => {
+    const err = new FederationForbiddenError('Access denied', { grantId: 'g1' });
+    const env = err.toEnvelope();
+    expect(env.error.code).toBe('forbidden');
+    expect(env.error.message).toBe('Access denied');
+    expect(env.error.details).toEqual({ grantId: 'g1' });
+  });
+
+  it('toEnvelope omits details when not provided', () => {
+    const err = new FederationNotFoundError();
+    const env = err.toEnvelope();
+    expect(Object.prototype.hasOwnProperty.call(env.error, 'details')).toBe(false);
+  });
+
+  it('error codes tuple covers all subclasses (exhaustiveness check)', () => {
+    // If a new subclass is added without a code, this test fails at compile time.
+    const allCodes = new Set(FEDERATION_ERROR_CODES);
+    for (const [code] of cases) {
+      expect(allCodes.has(code as (typeof FEDERATION_ERROR_CODES)[number])).toBe(true);
+    }
+    // All codes are covered by at least one case
+    expect(cases).toHaveLength(FEDERATION_ERROR_CODES.length);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Source tag + tagWithSource
+// ---------------------------------------------------------------------------
+
+describe('SourceTagSchema', () => {
+  it('accepts a non-empty _source string', () => {
+    expect(SourceTagSchema.safeParse({ _source: 'local' }).success).toBe(true);
+    expect(SourceTagSchema.safeParse({ _source: 'mosaic.uscllc.com' }).success).toBe(true);
+  });
+
+  it('rejects empty _source string', () => {
+    expect(SourceTagSchema.safeParse({ _source: '' }).success).toBe(false);
+  });
+});
+
+describe('tagWithSource', () => {
+  it('stamps each item with the given source', () => {
+    const items = [{ id: '1' }, { id: '2' }];
+    const tagged = tagWithSource(items, SOURCE_LOCAL);
+    expect(tagged).toEqual([
+      { id: '1', _source: 'local' },
+      { id: '2', _source: 'local' },
+    ]);
+  });
+
+  it('preserves original item fields', () => {
+    const items = [{ id: 'x', name: 'Task', done: false }];
+    const tagged = tagWithSource(items, 'mosaic.uscllc.com');
+    expect(tagged[0]).toMatchObject({ id: 'x', name: 'Task', done: false });
+    expect(tagged[0]?._source).toBe('mosaic.uscllc.com');
+  });
+
+  it('returns empty array for empty input', () => {
+    expect(tagWithSource([], 'local')).toEqual([]);
+  });
+
+  it('round-trip: tagWithSource output passes SourceTagSchema', () => {
+    const tagged = tagWithSource([{ id: '1' }], 'local');
+    expect(SourceTagSchema.safeParse(tagged[0]).success).toBe(true);
+  });
+});

packages/types/src/federation/error.ts

@@ -0,0 +1,164 @@
+/**
+ * Federation wire-format error envelope and exception hierarchy.
+ *
+ * Source of truth: docs/federation/PRD.md §6, §8.
+ *
+ * DESIGN: Typed error classes rather than discriminated union values
+ * ──────────────────────────────────────────────────────────────────
+ * We expose:
+ *   1. `FEDERATION_ERROR_CODES` — closed string-enum tuple (exhaustiveness-checkable).
+ *   2. `FederationErrorCode` — union type inferred from the tuple.
+ *   3. `FederationErrorEnvelopeSchema` — Zod schema for the wire format.
+ *   4. `FederationError` — base Error subclass with a typed `code` property.
+ *      One concrete subclass per code (e.g. `FederationUnauthorizedError`),
+ *      which enables `instanceof` dispatch in handlers without a switch.
+ *
+ * Rationale: subclasses give gateway handlers and the client a clean dispatch
+ * point (catch + instanceof) without re-parsing or switch tables.  All classes
+ * carry `code` so a generic logger can act on any FederationError uniformly.
+ *
+ * Pure — no NestJS, no DB, no Node-only APIs. Safe for browser/edge.
+ */
+
+import { z } from 'zod';
+
+// ---------------------------------------------------------------------------
+// Error code enum (closed)
+// ---------------------------------------------------------------------------
+
+export const FEDERATION_ERROR_CODES = [
+  'unauthorized',
+  'forbidden',
+  'not_found',
+  'rate_limited',
+  'scope_violation',
+  'invalid_request',
+  'internal_error',
+] as const;
+
+export type FederationErrorCode = (typeof FEDERATION_ERROR_CODES)[number];
+
+// ---------------------------------------------------------------------------
+// Wire-format schema
+// ---------------------------------------------------------------------------
+
+export const FederationErrorEnvelopeSchema = z.object({
+  error: z.object({
+    code: z.enum(FEDERATION_ERROR_CODES),
+    message: z.string(),
+    details: z.unknown().optional(),
+  }),
+});
+
+export type FederationErrorEnvelope = z.infer<typeof FederationErrorEnvelopeSchema>;
+
+// ---------------------------------------------------------------------------
+// Exception class hierarchy
+// ---------------------------------------------------------------------------
+
+/**
+ * Base class for all federation errors.
+ * Carries a typed `code` so handlers can act uniformly on any FederationError.
+ */
+export class FederationError extends Error {
+  readonly code: FederationErrorCode;
+  readonly details?: unknown;
+
+  constructor(code: FederationErrorCode, message: string, details?: unknown) {
+    super(message);
+    this.name = 'FederationError';
+    this.code = code;
+    this.details = details;
+  }
+
+  /** Serialise to the wire-format error envelope. */
+  toEnvelope(): FederationErrorEnvelope {
+    return {
+      error: {
+        code: this.code,
+        message: this.message,
+        ...(this.details !== undefined ? { details: this.details } : {}),
+      },
+    };
+  }
+}
+
+/** Client cert is missing, invalid, or signed by an untrusted CA. */
+export class FederationUnauthorizedError extends FederationError {
+  constructor(message = 'Unauthorized', details?: unknown) {
+    super('unauthorized', message, details);
+    this.name = 'FederationUnauthorizedError';
+  }
+}
+
+/** Grant is inactive, revoked, or the subject user lacks access to the resource. */
+export class FederationForbiddenError extends FederationError {
+  constructor(message = 'Forbidden', details?: unknown) {
+    super('forbidden', message, details);
+    this.name = 'FederationForbiddenError';
+  }
+}
+
+/** Requested resource does not exist. */
+export class FederationNotFoundError extends FederationError {
+  constructor(message = 'Not found', details?: unknown) {
+    super('not_found', message, details);
+    this.name = 'FederationNotFoundError';
+  }
+}
+
+/** Grant has exceeded its rate limit; Retry-After should accompany this. */
+export class FederationRateLimitedError extends FederationError {
+  constructor(message = 'Rate limit exceeded', details?: unknown) {
+    super('rate_limited', message, details);
+    this.name = 'FederationRateLimitedError';
+  }
+}
+
+/**
+ * The request targets a resource or performs an action that the grant's
+ * scope explicitly disallows (distinct from generic 403 — scope_violation
+ * means the scope configuration itself blocked the request).
+ */
+export class FederationScopeViolationError extends FederationError {
+  constructor(message = 'Scope violation', details?: unknown) {
+    super('scope_violation', message, details);
+    this.name = 'FederationScopeViolationError';
+  }
+}
+
+/** Malformed request — missing fields, invalid cursor, unknown verb, etc. */
+export class FederationInvalidRequestError extends FederationError {
+  constructor(message = 'Invalid request', details?: unknown) {
+    super('invalid_request', message, details);
+    this.name = 'FederationInvalidRequestError';
+  }
+}
+
+/** Unexpected server-side failure. */
+export class FederationInternalError extends FederationError {
+  constructor(message = 'Internal error', details?: unknown) {
+    super('internal_error', message, details);
+    this.name = 'FederationInternalError';
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Typed parser
+// ---------------------------------------------------------------------------
+
+/**
+ * Parse an unknown value as a FederationErrorEnvelope.
+ * Throws a plain Error (not FederationError) when parsing fails — this means
+ * the payload wasn't even a valid error envelope.
+ */
+export function parseFederationErrorEnvelope(input: unknown): FederationErrorEnvelope {
+  const result = FederationErrorEnvelopeSchema.safeParse(input);
+  if (!result.success) {
+    const issues = result.error.issues
+      .map((e) => `  - [${e.path.join('.') || 'root'}] ${e.message}`)
+      .join('\n');
+    throw new Error(`Invalid federation error envelope:\n${issues}`);
+  }
+  return result.data;
+}

packages/types/src/federation/index.ts

@@ -0,0 +1,16 @@
+/**
+ * Federation wire-format DTOs — public barrel.
+ *
+ * Exports everything downstream M3 tasks need:
+ *   verbs.ts      — FEDERATION_VERBS constant + FederationVerb type
+ *   request.ts    — FederationRequestSchema + FederationRequest
+ *   response.ts   — list/get/capabilities schema factories + types
+ *   source-tag.ts — SourceTagSchema, tagWithSource helper
+ *   error.ts      — error envelope schema + typed exception hierarchy
+ */
+
+export * from './verbs.js';
+export * from './request.js';
+export * from './response.js';
+export * from './source-tag.js';
+export * from './error.js';

packages/types/src/federation/request.ts

@@ -0,0 +1,47 @@
+/**
+ * Federation wire-format request schema.
+ *
+ * Source of truth: docs/federation/PRD.md §9 (query model).
+ *
+ * Pure — no NestJS, no DB, no Node-only APIs. Safe for browser/edge.
+ */
+
+import { z } from 'zod';
+import { FEDERATION_VERBS } from './verbs.js';
+
+// ---------------------------------------------------------------------------
+// Query params — free-form key/value pairs passed alongside the request
+// ---------------------------------------------------------------------------
+
+const QueryParamsSchema = z.record(z.string(), z.string()).optional();
+
+// ---------------------------------------------------------------------------
+// Top-level request schema
+// ---------------------------------------------------------------------------
+
+export const FederationRequestSchema = z.object({
+  /**
+   * Verb being invoked. One of the M3 federation verbs.
+   */
+  verb: z.enum(FEDERATION_VERBS),
+
+  /**
+   * Resource path being queried, e.g. "tasks", "notes", "memory".
+   * Forward-slash-separated for sub-resources (e.g. "teams/abc/tasks").
+   */
+  resource: z.string().min(1, { message: 'resource must not be empty' }),
+
+  /**
+   * Optional free-form query params (filters, sort, etc.).
+   * Values are always strings; consumers parse as needed.
+   */
+  params: QueryParamsSchema,
+
+  /**
+   * Opaque pagination cursor returned by a previous list response.
+   * Absent on first page.
+   */
+  cursor: z.string().optional(),
+});
+
+export type FederationRequest = z.infer<typeof FederationRequestSchema>;

packages/types/src/federation/response.ts

@@ -0,0 +1,162 @@
+/**
+ * Federation wire-format response schemas.
+ *
+ * Source of truth: docs/federation/PRD.md §9 and MILESTONES.md §M3.
+ *
+ * DESIGN: Generic factory functions rather than z.lazy
+ * ─────────────────────────────────────────────────────
+ * Zod generic schemas cannot be expressed as a single re-usable `z.ZodType`
+ * value because TypeScript's type system erases the generic at the call site.
+ * The idiomatic Zod v4 pattern is factory functions that take an item schema
+ * and return a fully-typed schema.
+ *
+ *   const MyListSchema = FederationListResponseSchema(z.string());
+ *   type MyList = z.infer<typeof MyListSchema>;
+ *   // => { items: string[]; nextCursor?: string; _partial?: boolean; _truncated?: boolean }
+ *
+ * Downstream consumers (M3-03..M3-07, M3-08, M3-09) should call these
+ * factories once per resource type and cache the result.
+ *
+ * Pure — no NestJS, no DB, no Node-only APIs. Safe for browser/edge.
+ */
+
+import { z } from 'zod';
+
+import { FEDERATION_VERBS } from './verbs.js';
+
+// ---------------------------------------------------------------------------
+// Shared envelope flags
+// ---------------------------------------------------------------------------
+
+/**
+ * `_partial`: true when the response is a subset of available data (e.g. due
+ * to scope intersection reducing the result set).
+ */
+const PartialFlag = z.boolean().optional();
+
+/**
+ * `_truncated`: true when the response was capped by max_rows_per_query and
+ * additional pages exist beyond the current cursor.
+ */
+const TruncatedFlag = z.boolean().optional();
+
+// ---------------------------------------------------------------------------
+// FederationListResponseSchema<T> factory
+// ---------------------------------------------------------------------------
+
+/**
+ * Returns a Zod schema for a paginated federation list envelope.
+ *
+ * @param itemSchema - Zod schema for a single item in the list.
+ *
+ * @example
+ * ```ts
+ * const TaskListSchema = FederationListResponseSchema(TaskSchema);
+ * type TaskList = z.infer<typeof TaskListSchema>;
+ * ```
+ */
+export function FederationListResponseSchema<T extends z.ZodTypeAny>(itemSchema: T) {
+  return z.object({
+    items: z.array(itemSchema),
+    nextCursor: z.string().optional(),
+    _partial: PartialFlag,
+    _truncated: TruncatedFlag,
+  });
+}
+
+export type FederationListResponse<T> = {
+  items: T[];
+  nextCursor?: string;
+  _partial?: boolean;
+  _truncated?: boolean;
+};
+
+// ---------------------------------------------------------------------------
+// FederationGetResponseSchema<T> factory
+// ---------------------------------------------------------------------------
+
+/**
+ * Returns a Zod schema for a single-item federation get envelope.
+ *
+ * `item` is null when the resource was not found (404 equivalent on the wire).
+ *
+ * @param itemSchema - Zod schema for the item (nullable is applied internally).
+ *
+ * @example
+ * ```ts
+ * const TaskGetSchema = FederationGetResponseSchema(TaskSchema);
+ * type TaskGet = z.infer<typeof TaskGetSchema>;
+ * ```
+ */
+export function FederationGetResponseSchema<T extends z.ZodTypeAny>(itemSchema: T) {
+  return z.object({
+    item: itemSchema.nullable(),
+    _partial: PartialFlag,
+  });
+}
+
+export type FederationGetResponse<T> = {
+  item: T | null;
+  _partial?: boolean;
+};
+
+// ---------------------------------------------------------------------------
+// FederationCapabilitiesResponseSchema (fixed shape)
+// ---------------------------------------------------------------------------
+
+/**
+ * Shape mirrors FederationScope (apps/gateway/src/federation/scope-schema.ts)
+ * but is kept separate to avoid coupling packages/types to the gateway module.
+ * The serving side populates this from the resolved grant scope at request time.
+ */
+export const FederationCapabilitiesResponseSchema = z.object({
+  /**
+   * Resources this grant is allowed to query.
+   */
+  resources: z.array(z.string()).nonempty(),
+
+  /**
+   * Resources explicitly blocked for this grant even if they exist.
+   */
+  excluded_resources: z.array(z.string()),
+
+  /**
+   * Per-resource filters (mirrors FederationScope.filters from PRD §8.1).
+   * Keys are resource names; values control team/personal visibility.
+   */
+  filters: z
+    .record(
+      z.string(),
+      z.object({
+        include_teams: z.array(z.string()).optional(),
+        include_personal: z.boolean().optional(),
+      }),
+    )
+    .optional(),
+
+  /**
+   * Hard cap on rows returned per query for this grant.
+   */
+  max_rows_per_query: z.number().int().positive(),
+
+  /**
+   * Verbs currently available. Will expand in M4+ (search).
+   * Closed enum — only values from FEDERATION_VERBS are accepted.
+   */
+  supported_verbs: z.array(z.enum(FEDERATION_VERBS)).nonempty(),
+
+  /**
+   * Rate-limit state for this grant (PRD §9.1).
+   * M4 populates `remaining` and `reset_at`; M3 servers may return only
+   * `limit_per_minute` or omit the field entirely.
+   */
+  rate_limit: z
+    .object({
+      limit_per_minute: z.number().int().positive(),
+      remaining: z.number().int().nonnegative().optional(),
+      reset_at: z.string().datetime().optional(),
+    })
+    .optional(),
+});
+
+export type FederationCapabilitiesResponse = z.infer<typeof FederationCapabilitiesResponseSchema>;

packages/types/src/federation/source-tag.ts

@@ -0,0 +1,61 @@
+/**
+ * _source tag for federation fan-out results.
+ *
+ * Source of truth: docs/federation/PRD.md §9.3 and MILESTONES.md §M3 acceptance test #8.
+ *
+ * When source: "all" is requested, the gateway fans out to local + all active
+ * federated peers, merges results, and tags each item with _source so the
+ * caller knows the provenance.
+ *
+ * Pure — no NestJS, no DB, no Node-only APIs. Safe for browser/edge.
+ */
+
+import { z } from 'zod';
+
+// ---------------------------------------------------------------------------
+// Source tag schema
+// ---------------------------------------------------------------------------
+
+/**
+ * `_source` is either:
+ * - `"local"` — the item came from this gateway's own storage.
+ * - a peer common name (e.g. `"mosaic.uscllc.com"`) — the item came from
+ *   that federated peer.
+ */
+export const SourceTagSchema = z.object({
+  _source: z.string().min(1, { message: '_source must not be empty' }),
+});
+
+export type SourceTag = z.infer<typeof SourceTagSchema>;
+
+/**
+ * Literal union for the well-known local source value.
+ * Peers are identified by hostname strings, so there is no closed enum.
+ */
+export const SOURCE_LOCAL = 'local' as const;
+
+// ---------------------------------------------------------------------------
+// Helper: tagWithSource
+// ---------------------------------------------------------------------------
+
+/**
+ * Stamps each item in `items` with `{ _source: source }`.
+ *
+ * The return type merges the item type with SourceTag so callers get full
+ * type-safety on both the original fields and `_source`.
+ *
+ * @param items  - Array of items to tag.
+ * @param source - Either `"local"` or a peer hostname (common name from the
+ *                 client cert's CN or O field).
+ *
+ * @example
+ * ```ts
+ * const local = tagWithSource([{ id: '1', title: 'Task' }], 'local');
+ * // => [{ id: '1', title: 'Task', _source: 'local' }]
+ *
+ * const remote = tagWithSource(peerItems, 'mosaic.uscllc.com');
+ * ```
+ */
+export function tagWithSource<T extends object>(items: T[], source: string): Array<T & SourceTag> {
+  return items.map((item) => ({ ...item, _source: source }));
+}

packages/types/src/federation/verbs.ts

@@ -0,0 +1,11 @@
+/**
+ * Federation verb constants and types.
+ *
+ * Source of truth: docs/federation/PRD.md §9.1
+ *
+ * M3 ships list, get, capabilities. search lives in M4.
+ */
+
+export const FEDERATION_VERBS = ['list', 'get', 'capabilities'] as const;
+
+export type FederationVerb = (typeof FEDERATION_VERBS)[number];

packages/types/src/index.ts

@@ -5,3 +5,4 @@ export * from './agent/index.js';
 export * from './provider/index.js';
 export * from './routing/index.js';
 export * from './commands/index.js';
+export * from './federation/index.js';

pnpm-lock.yaml

@@ -679,6 +679,9 @@ importers:
       class-validator:
         specifier: ^0.15.1
         version: 0.15.1
+      zod:
+        specifier: ^4.3.6
+        version: 4.3.6
     devDependencies:
       typescript:
         specifier: ^5.8.0
@@ -710,10 +713,10 @@ importers:
     dependencies:
       '@mariozechner/pi-agent-core':
         specifier: ^0.63.1
-        version: 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@4.3.6)
+        version: 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@3.25.76)
       '@mariozechner/pi-ai':
         specifier: ^0.63.1
-        version: 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@4.3.6)
+        version: 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@3.25.76)
       '@sinclair/typebox':
         specifier: ^0.34.41
         version: 0.34.48
@@ -7326,6 +7329,12 @@ snapshots:
       '@jridgewell/gen-mapping': 0.3.13
       '@jridgewell/trace-mapping': 0.3.31
 
+  '@anthropic-ai/sdk@0.73.0(zod@3.25.76)':
+    dependencies:
+      json-schema-to-ts: 3.1.1
+    optionalDependencies:
+      zod: 3.25.76
+
   '@anthropic-ai/sdk@0.73.0(zod@4.3.6)':
     dependencies:
       json-schema-to-ts: 3.1.1
@@ -8667,6 +8676,18 @@ snapshots:
       - ws
       - zod
 
+  '@mariozechner/pi-agent-core@0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@3.25.76)':
+    dependencies:
+      '@mariozechner/pi-ai': 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@3.25.76)
+    transitivePeerDependencies:
+      - '@modelcontextprotocol/sdk'
+      - aws-crt
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+      - ws
+      - zod
+
   '@mariozechner/pi-agent-core@0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@4.3.6)':
     dependencies:
       '@mariozechner/pi-ai': 0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@4.3.6)
@@ -8715,6 +8736,30 @@ snapshots:
       - ws
       - zod
 
+  '@mariozechner/pi-ai@0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@3.25.76)':
+    dependencies:
+      '@anthropic-ai/sdk': 0.73.0(zod@3.25.76)
+      '@aws-sdk/client-bedrock-runtime': 3.1008.0
+      '@google/genai': 1.45.0(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))
+      '@mistralai/mistralai': 1.14.1
+      '@sinclair/typebox': 0.34.48
+      ajv: 8.18.0
+      ajv-formats: 3.0.1(ajv@8.18.0)
+      chalk: 5.6.2
+      openai: 6.26.0(ws@8.20.0)(zod@3.25.76)
+      partial-json: 0.1.7
+      proxy-agent: 6.5.0
+      undici: 7.24.3
+      zod-to-json-schema: 3.25.1(zod@3.25.76)
+    transitivePeerDependencies:
+      - '@modelcontextprotocol/sdk'
+      - aws-crt
+      - bufferutil
+      - supports-color
+      - utf-8-validate
+      - ws
+      - zod
+
   '@mariozechner/pi-ai@0.63.2(@modelcontextprotocol/sdk@1.28.0(zod@4.3.6))(ws@8.20.0)(zod@4.3.6)':
     dependencies:
       '@anthropic-ai/sdk': 0.73.0(zod@4.3.6)
@@ -13307,6 +13352,11 @@ snapshots:
     dependencies:
       mimic-function: 5.0.1
 
+  openai@6.26.0(ws@8.20.0)(zod@3.25.76):
+    optionalDependencies:
+      ws: 8.20.0
+      zod: 3.25.76
+
   openai@6.26.0(ws@8.20.0)(zod@4.3.6):
     optionalDependencies:
       ws: 8.20.0

tools/federation-harness/README.md

@@ -0,0 +1,254 @@
+# Federation Test Harness
+
+Local two-gateway federation test infrastructure for Mosaic Stack M3+.
+
+This harness boots two real gateway instances (`gateway-a`, `gateway-b`) on a
+shared Docker bridge network, each backed by its own Postgres (pgvector) +
+Valkey, sharing a single Step-CA. It is the test bed for all M3+ federation
+E2E tests.
+
+## Prerequisites
+
+- Docker with Compose v2 (`docker compose version` ≥ 2.20)
+- pnpm (for running via repo scripts)
+- `infra/step-ca/dev-password` must exist (copy from `infra/step-ca/dev-password.example`)
+
+## Network Topology
+
+```
+Host machine
+├── localhost:14001  →  gateway-a   (Server A — home / requesting)
+├── localhost:14002  →  gateway-b   (Server B — work / serving)
+├── localhost:15432  →  postgres-a
+├── localhost:15433  →  postgres-b
+├── localhost:16379  →  valkey-a
+├── localhost:16380  →  valkey-b
+└── localhost:19000  →  step-ca     (shared CA)
+
+Docker network: fed-test-net (bridge)
+  gateway-a ←──── mTLS ────→ gateway-b
+             ↘             ↗
+               step-ca
+```
+
+Ports are chosen to avoid collision with the base dev stack (5433, 6380, 14242, 9000).
+
+## Starting the Harness
+
+```bash
+# From repo root
+docker compose -f tools/federation-harness/docker-compose.two-gateways.yml up -d
+
+# Wait for all services to be healthy (~60-90s on first boot due to NestJS cold start)
+docker compose -f tools/federation-harness/docker-compose.two-gateways.yml ps
+```
+
+## Seeding Test Data
+
+The seed script provisions three grant scope variants (A, B, C) and walks the
+full enrollment flow so Server A ends up with active peers pointing at Server B.
+
+```bash
+# Assumes stack is already running
+pnpm tsx tools/federation-harness/seed.ts
+
+# Or boot + seed in one step
+pnpm tsx tools/federation-harness/seed.ts --boot
+```
+
+### Scope Variants
+
+| Variant | Resources          | Filters                            | Excluded    | Purpose                         |
+| ------- | ------------------ | ---------------------------------- | ----------- | ------------------------------- |
+| A       | tasks, notes       | include_personal: true             | (none)      | Personal data federation        |
+| B       | tasks              | include_teams: ['T1'], no personal | (none)      | Team-scoped, no personal        |
+| C       | tasks, credentials | include_personal: true             | credentials | Sanity: excluded wins over list |
+
+## Using from Vitest
+
+```ts
+import {
+  bootHarness,
+  tearDownHarness,
+  serverA,
+  serverB,
+  seed,
+} from '../../tools/federation-harness/harness.js';
+import type { HarnessHandle } from '../../tools/federation-harness/harness.js';
+
+let handle: HarnessHandle;
+
+beforeAll(async () => {
+  handle = await bootHarness();
+}, 180_000); // allow 3 min for Docker pull + NestJS cold start
+
+afterAll(async () => {
+  await tearDownHarness(handle);
+});
+
+test('variant A: list tasks returns personal tasks', async () => {
+  // NOTE: Only 'all' is supported for now — per-variant narrowing is M3-11.
+  const seedResult = await seed(handle, 'all');
+  const a = serverA(handle);
+
+  const res = await fetch(`${a.baseUrl}/api/federation/tasks`, {
+    headers: { 'x-federation-grant': seedResult.grants.variantA.id },
+  });
+  expect(res.status).toBe(200);
+});
+```
+
+> **Note:** `seed()` bootstraps a fresh admin user on each gateway via
+> `POST /api/bootstrap/setup`. Both gateways must have zero users (pristine DB).
+> If either gateway already has users, `seed()` throws with a clear error.
+> Reset state with `docker compose down -v`.
+
+The `bootHarness()` function is **idempotent**: if both gateways are already
+healthy, it reuses the running stack and returns `ownedStack: false`. Tests
+should not call `tearDownHarness` when `ownedStack` is false unless they
+explicitly want to shut down a shared stack.
+
+## Vitest Config (pnpm test:federation)
+
+Add to `vitest.config.ts` at repo root (or a dedicated config):
+
+```ts
+// vitest.federation.config.ts
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    include: ['**/*.federation.test.ts'],
+    testTimeout: 60_000,
+    hookTimeout: 180_000,
+    reporters: ['verbose'],
+  },
+});
+```
+
+Then add to root `package.json`:
+
+```json
+"test:federation": "vitest run --config vitest.federation.config.ts"
+```
+
+## Nuking State
+
+```bash
+# Remove containers AND volumes (ephemeral state — CA keys, DBs, everything)
+docker compose -f tools/federation-harness/docker-compose.two-gateways.yml down -v
+```
+
+On next `up`, Step-CA re-initialises from scratch and generates new CA keys.
+
+## Step-CA Root Certificate
+
+The CA root lives in the `fed-harness-step-ca` Docker volume at
+`/home/step/certs/root_ca.crt`. To extract it to the host:
+
+```bash
+docker run --rm \
+  -v fed-harness-step-ca:/home/step \
+  alpine cat /home/step/certs/root_ca.crt > /tmp/fed-harness-root-ca.crt
+```
+
+## Troubleshooting
+
+### Port conflicts
+
+Default host ports: 14001, 14002, 15432, 15433, 16379, 16380, 19000.
+Override via environment variables before `docker compose up`:
+
+```bash
+GATEWAY_A_HOST_PORT=14101 GATEWAY_B_HOST_PORT=14102 \
+  docker compose -f tools/federation-harness/docker-compose.two-gateways.yml up -d
+```
+
+### Image pull failures
+
+The gateway image is digest-pinned to:
+
+```
+git.mosaicstack.dev/mosaicstack/stack/gateway@sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02
+```
+
+(sha-9f1a081, post-#491 IMG-FIX)
+
+If the registry is unreachable, Docker will use the locally cached image if
+present. If no local image exists, the compose up will fail with a pull error.
+In that case:
+
+1. Ensure you can reach `git.mosaicstack.dev` (VPN, DNS, etc.).
+2. Log in: `docker login git.mosaicstack.dev`
+3. Pull manually: `docker pull git.mosaicstack.dev/mosaicstack/stack/gateway@sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02`
+
+### NestJS cold start
+
+Gateway containers take 40–60 seconds to become healthy on first boot (Node.js
+module resolution + NestJS DI bootstrap). The `start_period: 60s` in the
+compose healthcheck covers this. `bootHarness()` polls for up to 3 minutes.
+
+### Step-CA startup
+
+Step-CA initialises on first boot (generates CA keys). This takes ~5-10s.
+The `start_period: 30s` in the healthcheck covers it. Both gateways wait for
+Step-CA to be healthy before starting (`depends_on: step-ca: condition: service_healthy`).
+
+### dev-password missing
+
+The Step-CA container requires `infra/step-ca/dev-password` to be mounted.
+Copy the example and set a local password:
+
+```bash
+cp infra/step-ca/dev-password.example infra/step-ca/dev-password
+# Edit the file to set your preferred dev CA password
+```
+
+The file is `.gitignore`d — do not commit it.
+
+## Image Digest Note
+
+The gateway image is pinned to `sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02`
+(sha-9f1a081). This is the digest promoted by PR #491 (IMG-FIX). The `latest`
+tag is forbidden per Mosaic image policy. When a new gateway build is promoted,
+update the digest in `docker-compose.two-gateways.yml` and in this file.
+
+## Known Limitations
+
+### BETTER_AUTH_URL enrollment URL bug (upstream production code — not yet fixed)
+
+`apps/gateway/src/federation/federation.controller.ts:145` constructs the
+enrollment URL using `process.env['BETTER_AUTH_URL'] ?? 'http://localhost:14242'`.
+This is an upstream bug: `BETTER_AUTH_URL` is the Better Auth origin (typically
+the web app), not the gateway's own base URL. In non-harness deployments this
+produces an enrollment URL pointing to the wrong host or port.
+
+**How the harness handles this:**
+
+1. **In-cluster calls (container-to-container):** The compose file sets
+   `BETTER_AUTH_URL: 'http://gateway-b:3000'` so the enrollment URL returned by
+   the gateway uses the Docker internal hostname. This lets other containers in the
+   `fed-test-net` network resolve and reach Server B's enrollment endpoint.
+
+2. **Host-side URL rewrite (seed script):** The `seed.ts` script runs on the host
+   machine where `gateway-b` is not a resolvable hostname. Before calling
+   `fetch(enrollmentUrl, ...)`, the seed script rewrites the URL: it extracts only
+   the token path segment from `enrollmentUrl` and reassembles the URL using the
+   host-accessible `serverBUrl` (default: `http://localhost:14002`). This lets the
+   seed script redeem enrollment tokens from the host without being affected by the
+   in-cluster hostname in the returned URL.
+
+**TODO:** Fix `federation.controller.ts` to derive the enrollment URL from its own
+listening address (e.g. `GATEWAY_BASE_URL` env var or a dedicated
+`FEDERATION_ENROLLMENT_BASE_URL` env var) rather than reusing `BETTER_AUTH_URL`.
+Tracked as a follow-up to PR #505 — do not bundle with harness changes.
+
+## Permanent Infrastructure
+
+This harness is designed to outlive M3 and be reused by M4+ milestone tests.
+It is not a throwaway scaffold — treat it as production test infrastructure:
+
+- Keep it idempotent.
+- Do not hardcode test assumptions in the harness layer (put them in tests).
+- Update the seed script when new scope variants are needed.
+- The README and harness should be kept in sync as the federation API evolves.

tools/federation-harness/docker-compose.two-gateways.yml

@@ -0,0 +1,247 @@
+# tools/federation-harness/docker-compose.two-gateways.yml
+#
+# Two-gateway federation test harness — local-only, no Portainer/Swarm needed.
+#
+# USAGE (manual):
+#   docker compose -f tools/federation-harness/docker-compose.two-gateways.yml up -d
+#   docker compose -f tools/federation-harness/docker-compose.two-gateways.yml down -v
+#
+# USAGE (from harness.ts):
+#   const handle = await bootHarness();
+#   ...
+#   await tearDownHarness(handle);
+#
+# TOPOLOGY:
+#   gateway-a  — "home" instance (Server A, the requesting side)
+#     └── postgres-a  (pgvector/pg17, port 15432)
+#     └── valkey-a    (port 16379)
+#   gateway-b  — "work" instance (Server B, the serving side)
+#     └── postgres-b  (pgvector/pg17, port 15433)
+#     └── valkey-b    (port 16380)
+#   step-ca    — shared CA for both gateways (port 19000)
+#
+# All services share the `fed-test-net` bridge network.
+# Host port ranges (15432-15433, 16379-16380, 14001-14002, 19000) are chosen
+# to avoid collision with the base dev stack (5433, 6380, 14242, 9000).
+#
+# IMAGE:
+#   Pinned to the immutable digest sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02
+#   (sha-9f1a081, post-#491 IMG-FIX, smoke-tested locally).
+#   Update this digest only after a new CI build is promoted to the registry.
+#
+# STEP-CA:
+#   Single shared Step-CA instance. Both gateways connect to it.
+#   CA volume is ephemeral per `docker compose down -v`; regenerated on next up.
+#   The harness seed script provisions the CA roots cross-trust after first boot.
+
+services:
+  # ─── Shared Certificate Authority ────────────────────────────────────────────
+  step-ca:
+    image: smallstep/step-ca:0.27.4
+    container_name: fed-harness-step-ca
+    restart: unless-stopped
+    ports:
+      - '${STEP_CA_HOST_PORT:-19000}:9000'
+    volumes:
+      - step_ca_data:/home/step
+      - ../../infra/step-ca/init.sh:/usr/local/bin/mosaic-step-ca-init.sh:ro
+      - ../../infra/step-ca/templates:/etc/step-ca-templates:ro
+      - ../../infra/step-ca/dev-password:/run/secrets/ca_password:ro
+    entrypoint: ['/bin/sh', '/usr/local/bin/mosaic-step-ca-init.sh']
+    networks:
+      - fed-test-net
+    healthcheck:
+      test:
+        [
+          'CMD',
+          'step',
+          'ca',
+          'health',
+          '--ca-url',
+          'https://localhost:9000',
+          '--root',
+          '/home/step/certs/root_ca.crt',
+        ]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 30s
+
+  # ─── Server A — Home / Requesting Gateway ────────────────────────────────────
+  postgres-a:
+    image: pgvector/pgvector:pg17
+    container_name: fed-harness-postgres-a
+    restart: unless-stopped
+    ports:
+      - '${PG_A_HOST_PORT:-15432}:5432'
+    environment:
+      POSTGRES_USER: mosaic
+      POSTGRES_PASSWORD: mosaic
+      POSTGRES_DB: mosaic
+    volumes:
+      - pg_a_data:/var/lib/postgresql/data
+      - ../../infra/pg-init:/docker-entrypoint-initdb.d:ro
+    networks:
+      - fed-test-net
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U mosaic']
+      interval: 5s
+      timeout: 3s
+      retries: 5
+
+  valkey-a:
+    image: valkey/valkey:8-alpine
+    container_name: fed-harness-valkey-a
+    restart: unless-stopped
+    ports:
+      - '${VALKEY_A_HOST_PORT:-16379}:6379'
+    volumes:
+      - valkey_a_data:/data
+    networks:
+      - fed-test-net
+    healthcheck:
+      test: ['CMD', 'valkey-cli', 'ping']
+      interval: 5s
+      timeout: 3s
+      retries: 5
+
+  gateway-a:
+    image: git.mosaicstack.dev/mosaicstack/stack/gateway@sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02
+    # Tag for human reference: sha-9f1a081 (post-#491 IMG-FIX; smoke-tested locally)
+    container_name: fed-harness-gateway-a
+    restart: unless-stopped
+    ports:
+      - '${GATEWAY_A_HOST_PORT:-14001}:3000'
+    environment:
+      MOSAIC_TIER: federated
+      DATABASE_URL: postgres://mosaic:mosaic@postgres-a:5432/mosaic
+      VALKEY_URL: redis://valkey-a:6379
+      GATEWAY_PORT: '3000'
+      GATEWAY_CORS_ORIGIN: 'http://localhost:14001'
+      BETTER_AUTH_SECRET: harness-secret-server-a-do-not-use-in-prod
+      BETTER_AUTH_URL: 'http://gateway-a:3000'
+      STEP_CA_URL: 'https://step-ca:9000'
+      FEDERATION_PEER_HOSTNAME: gateway-a
+      # Bootstrap password for POST /api/bootstrap/setup — used by seed.ts to create
+      # the first admin user. Only valid on a pristine (zero-user) database.
+      # Not the same as ADMIN_API_KEY — there is no static API key in the gateway.
+      ADMIN_BOOTSTRAP_PASSWORD: harness-admin-password-a
+    depends_on:
+      postgres-a:
+        condition: service_healthy
+      valkey-a:
+        condition: service_healthy
+      step-ca:
+        condition: service_healthy
+    networks:
+      - fed-test-net
+    healthcheck:
+      test:
+        [
+          'CMD',
+          'node',
+          '-e',
+          "require('http').get('http://127.0.0.1:3000/api/health', r => process.exit(r.statusCode === 200 ? 0 : 1)).on('error', () => process.exit(1))",
+        ]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 60s
+
+  # ─── Server B — Work / Serving Gateway ──────────────────────────────────────
+  postgres-b:
+    image: pgvector/pgvector:pg17
+    container_name: fed-harness-postgres-b
+    restart: unless-stopped
+    ports:
+      - '${PG_B_HOST_PORT:-15433}:5432'
+    environment:
+      POSTGRES_USER: mosaic
+      POSTGRES_PASSWORD: mosaic
+      POSTGRES_DB: mosaic
+    volumes:
+      - pg_b_data:/var/lib/postgresql/data
+      - ../../infra/pg-init:/docker-entrypoint-initdb.d:ro
+    networks:
+      - fed-test-net
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U mosaic']
+      interval: 5s
+      timeout: 3s
+      retries: 5
+
+  valkey-b:
+    image: valkey/valkey:8-alpine
+    container_name: fed-harness-valkey-b
+    restart: unless-stopped
+    ports:
+      - '${VALKEY_B_HOST_PORT:-16380}:6379'
+    volumes:
+      - valkey_b_data:/data
+    networks:
+      - fed-test-net
+    healthcheck:
+      test: ['CMD', 'valkey-cli', 'ping']
+      interval: 5s
+      timeout: 3s
+      retries: 5
+
+  gateway-b:
+    image: git.mosaicstack.dev/mosaicstack/stack/gateway@sha256:1069117740e00ccfeba357cae38c43f3729fe5ae702740ce474f6512414d7c02
+    # Tag for human reference: sha-9f1a081 (post-#491 IMG-FIX; smoke-tested locally)
+    container_name: fed-harness-gateway-b
+    restart: unless-stopped
+    ports:
+      - '${GATEWAY_B_HOST_PORT:-14002}:3000'
+    environment:
+      MOSAIC_TIER: federated
+      DATABASE_URL: postgres://mosaic:mosaic@postgres-b:5432/mosaic
+      VALKEY_URL: redis://valkey-b:6379
+      GATEWAY_PORT: '3000'
+      GATEWAY_CORS_ORIGIN: 'http://localhost:14002'
+      BETTER_AUTH_SECRET: harness-secret-server-b-do-not-use-in-prod
+      BETTER_AUTH_URL: 'http://gateway-b:3000'
+      STEP_CA_URL: 'https://step-ca:9000'
+      FEDERATION_PEER_HOSTNAME: gateway-b
+      # Bootstrap password for POST /api/bootstrap/setup — used by seed.ts to create
+      # the first admin user. Only valid on a pristine (zero-user) database.
+      # Not the same as ADMIN_API_KEY — there is no static API key in the gateway.
+      ADMIN_BOOTSTRAP_PASSWORD: harness-admin-password-b
+    depends_on:
+      postgres-b:
+        condition: service_healthy
+      valkey-b:
+        condition: service_healthy
+      step-ca:
+        condition: service_healthy
+    networks:
+      - fed-test-net
+    healthcheck:
+      test:
+        [
+          'CMD',
+          'node',
+          '-e',
+          "require('http').get('http://127.0.0.1:3000/api/health', r => process.exit(r.statusCode === 200 ? 0 : 1)).on('error', () => process.exit(1))",
+        ]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+      start_period: 60s
+
+networks:
+  fed-test-net:
+    name: fed-test-net
+    driver: bridge
+
+volumes:
+  step_ca_data:
+    name: fed-harness-step-ca
+  pg_a_data:
+    name: fed-harness-pg-a
+  valkey_a_data:
+    name: fed-harness-valkey-a
+  pg_b_data:
+    name: fed-harness-pg-b
+  valkey_b_data:
+    name: fed-harness-valkey-b

tools/federation-harness/harness.ts

@@ -0,0 +1,290 @@
+/**
+ * tools/federation-harness/harness.ts
+ *
+ * Vitest-consumable helpers for the two-gateway federation harness.
+ *
+ * USAGE (in a vitest test file):
+ *
+ *   import { bootHarness, tearDownHarness, serverA, serverB, seed } from
+ *     '../../tools/federation-harness/harness.js';
+ *
+ *   let handle: HarnessHandle;
+ *
+ *   beforeAll(async () => {
+ *     handle = await bootHarness();
+ *   }, 180_000);
+ *
+ *   afterAll(async () => {
+ *     await tearDownHarness(handle);
+ *   });
+ *
+ *   test('variant A — list tasks', async () => {
+ *     const seedResult = await seed(handle, 'all');
+ *     const a = serverA(handle);
+ *     const res = await fetch(`${a.baseUrl}/api/federation/list/tasks`, {
+ *       headers: { Authorization: `Bearer ${seedResult.adminTokenA}` },
+ *     });
+ *     expect(res.status).toBe(200);
+ *   });
+ *
+ * NOTE: The `seed()` helper currently only supports scenario='all'. Passing any
+ * other value throws immediately. Per-variant narrowing is deferred to M3-11.
+ *
+ * ESM / NodeNext: all imports use .js extensions.
+ */
+
+import { execSync, execFileSync } from 'node:child_process';
+import { resolve, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { runSeed, type SeedResult } from './seed.js';
+
+// ─── Types ───────────────────────────────────────────────────────────────────
+
+export interface GatewayAccessor {
+  /** Base URL reachable from the host machine, e.g. http://localhost:14001 */
+  baseUrl: string;
+  /** Bootstrap password used for POST /api/bootstrap/setup on a pristine gateway */
+  bootstrapPassword: string;
+  /** Internal Docker network hostname (for container-to-container calls) */
+  internalHostname: string;
+}
+
+export interface HarnessHandle {
+  /** Server A accessor */
+  a: GatewayAccessor;
+  /** Server B accessor */
+  b: GatewayAccessor;
+  /** Absolute path to the docker-compose file */
+  composeFile: string;
+  /** Whether this instance booted the stack (vs. reusing an existing one) */
+  ownedStack: boolean;
+  /** Optional seed result if seed() was called */
+  seedResult?: SeedResult;
+}
+
+/**
+ * Scenario to seed. Currently only 'all' is implemented; per-variant narrowing
+ * is tracked as M3-11. Passing any other value throws immediately with a clear
+ * error rather than silently over-seeding.
+ */
+export type SeedScenario = 'variantA' | 'variantB' | 'variantC' | 'all';
+
+// ─── Constants ────────────────────────────────────────────────────────────────
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const COMPOSE_FILE = resolve(__dirname, 'docker-compose.two-gateways.yml');
+
+const GATEWAY_A_URL = process.env['GATEWAY_A_URL'] ?? 'http://localhost:14001';
+const GATEWAY_B_URL = process.env['GATEWAY_B_URL'] ?? 'http://localhost:14002';
+const ADMIN_BOOTSTRAP_PASSWORD_A =
+  process.env['ADMIN_BOOTSTRAP_PASSWORD_A'] ?? 'harness-admin-password-a';
+const ADMIN_BOOTSTRAP_PASSWORD_B =
+  process.env['ADMIN_BOOTSTRAP_PASSWORD_B'] ?? 'harness-admin-password-b';
+
+const READINESS_TIMEOUT_MS = 180_000;
+const READINESS_POLL_MS = 3_000;
+
+// ─── Internal helpers ─────────────────────────────────────────────────────────
+
+async function isGatewayHealthy(baseUrl: string): Promise<boolean> {
+  try {
+    const res = await fetch(`${baseUrl}/api/health`, { signal: AbortSignal.timeout(5_000) });
+    return res.ok;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Poll both gateways in parallel until both are healthy or the shared deadline
+ * expires. Polling in parallel (rather than sequentially) avoids the bug where
+ * a slow gateway-a consumes all of the readiness budget before gateway-b is
+ * checked.
+ */
+async function waitForStack(handle: HarnessHandle): Promise<void> {
+  const gateways: Array<{ label: string; url: string }> = [
+    { label: 'gateway-a', url: handle.a.baseUrl },
+    { label: 'gateway-b', url: handle.b.baseUrl },
+  ];
+
+  await Promise.all(
+    gateways.map(async (gw) => {
+      // Each gateway gets its own independent deadline.
+      const deadline = Date.now() + READINESS_TIMEOUT_MS;
+      process.stdout.write(`[harness] Waiting for ${gw.label}...`);
+
+      while (Date.now() < deadline) {
+        if (await isGatewayHealthy(gw.url)) {
+          process.stdout.write(` ready\n`);
+          return;
+        }
+        if (Date.now() + READINESS_POLL_MS > deadline) {
+          throw new Error(
+            `[harness] ${gw.label} did not become healthy within ${READINESS_TIMEOUT_MS.toString()}ms`,
+          );
+        }
+        await new Promise((r) => setTimeout(r, READINESS_POLL_MS));
+        process.stdout.write('.');
+      }
+
+      throw new Error(
+        `[harness] ${gw.label} did not become healthy within ${READINESS_TIMEOUT_MS.toString()}ms`,
+      );
+    }),
+  );
+}
+
+function isStackRunning(): boolean {
+  try {
+    const output = execFileSync(
+      'docker',
+      ['compose', '-f', COMPOSE_FILE, 'ps', '--format', 'json'],
+      { encoding: 'utf8', stdio: ['pipe', 'pipe', 'pipe'] },
+    );
+
+    if (!output.trim()) return false;
+
+    // Parse JSON lines — each running service emits a JSON object per line
+    const lines = output.trim().split('\n').filter(Boolean);
+    const runningServices = lines.filter((line) => {
+      try {
+        const obj = JSON.parse(line) as { State?: string };
+        return obj.State === 'running';
+      } catch {
+        return false;
+      }
+    });
+
+    // Expect at least gateway-a and gateway-b running
+    return runningServices.length >= 2;
+  } catch {
+    return false;
+  }
+}
+
+// ─── Public API ───────────────────────────────────────────────────────────────
+
+/**
+ * Boot the harness stack.
+ *
+ * Idempotent: if the stack is already running and both gateways are healthy,
+ * this function reuses the existing stack and returns a handle with
+ * `ownedStack: false`. Callers that set `ownedStack: false` should NOT call
+ * `tearDownHarness` unless they explicitly want to tear down a pre-existing stack.
+ *
+ * If the stack is not running, it starts it with `docker compose up -d` and
+ * waits for both gateways to pass their /api/health probe.
+ */
+export async function bootHarness(): Promise<HarnessHandle> {
+  const handle: HarnessHandle = {
+    a: {
+      baseUrl: GATEWAY_A_URL,
+      bootstrapPassword: ADMIN_BOOTSTRAP_PASSWORD_A,
+      internalHostname: 'gateway-a',
+    },
+    b: {
+      baseUrl: GATEWAY_B_URL,
+      bootstrapPassword: ADMIN_BOOTSTRAP_PASSWORD_B,
+      internalHostname: 'gateway-b',
+    },
+    composeFile: COMPOSE_FILE,
+    ownedStack: false,
+  };
+
+  // Check if both gateways are already healthy
+  const [aHealthy, bHealthy] = await Promise.all([
+    isGatewayHealthy(handle.a.baseUrl),
+    isGatewayHealthy(handle.b.baseUrl),
+  ]);
+
+  if (aHealthy && bHealthy) {
+    console.log('[harness] Stack already running — reusing existing stack.');
+    handle.ownedStack = false;
+    return handle;
+  }
+
+  console.log('[harness] Starting federation harness stack...');
+  execSync(`docker compose -f "${COMPOSE_FILE}" up -d`, { stdio: 'inherit' });
+  handle.ownedStack = true;
+
+  await waitForStack(handle);
+  console.log('[harness] Stack is ready.');
+
+  return handle;
+}
+
+/**
+ * Tear down the harness stack.
+ *
+ * Runs `docker compose down -v` to remove containers AND volumes (ephemeral state).
+ * Only tears down if `handle.ownedStack` is true unless `force` is set.
+ */
+export async function tearDownHarness(
+  handle: HarnessHandle,
+  opts?: { force?: boolean },
+): Promise<void> {
+  if (!handle.ownedStack && !opts?.force) {
+    console.log(
+      '[harness] Stack not owned by this handle — skipping teardown (pass force: true to override).',
+    );
+    return;
+  }
+
+  console.log('[harness] Tearing down federation harness stack...');
+  execSync(`docker compose -f "${handle.composeFile}" down -v`, { stdio: 'inherit' });
+  console.log('[harness] Stack torn down.');
+}
+
+/**
+ * Return the Server A accessor from a harness handle.
+ * Convenience wrapper for test readability.
+ */
+export function serverA(handle: HarnessHandle): GatewayAccessor {
+  return handle.a;
+}
+
+/**
+ * Return the Server B accessor from a harness handle.
+ * Convenience wrapper for test readability.
+ */
+export function serverB(handle: HarnessHandle): GatewayAccessor {
+  return handle.b;
+}
+
+/**
+ * Seed the harness with test data for one or more scenarios.
+ *
+ * @param handle   The harness handle returned by bootHarness().
+ * @param scenario Which scope variants to provision. Currently only 'all' is
+ *                 supported — passing any other value throws immediately with a
+ *                 clear error. Per-variant narrowing is tracked as M3-11.
+ *
+ * Returns a SeedResult with grant IDs, peer IDs, and admin tokens for each
+ * gateway, which test assertions can reference.
+ *
+ * IMPORTANT: The harness assumes a pristine database on both gateways. The seed
+ * bootstraps an admin user on each gateway via POST /api/bootstrap/setup. If
+ * either gateway already has users, seed() throws with a clear error message.
+ * Run 'docker compose down -v' to reset state.
+ */
+export async function seed(
+  handle: HarnessHandle,
+  scenario: SeedScenario = 'all',
+): Promise<SeedResult> {
+  if (scenario !== 'all') {
+    throw new Error(
+      `seed: scenario narrowing not yet implemented; pass "all" for now. ` +
+        `Got: "${scenario}". Per-variant narrowing is tracked as M3-11.`,
+    );
+  }
+
+  const result = await runSeed({
+    serverAUrl: handle.a.baseUrl,
+    serverBUrl: handle.b.baseUrl,
+    adminBootstrapPasswordA: handle.a.bootstrapPassword,
+    adminBootstrapPasswordB: handle.b.bootstrapPassword,
+  });
+
+  handle.seedResult = result;
+  return result;
+}

tools/federation-harness/seed.ts

@@ -0,0 +1,603 @@
+#!/usr/bin/env tsx
+/**
+ * tools/federation-harness/seed.ts
+ *
+ * Provisions test data for the two-gateway federation harness.
+ * Run via: tsx tools/federation-harness/seed.ts
+ *
+ * What this script does:
+ *  1. (Optional) Boots the compose stack if --boot flag is passed.
+ *  2. Waits for both gateways to be healthy.
+ *  3. Bootstraps an admin user + token on each gateway via POST /api/bootstrap/setup.
+ *  4. Creates three grants on Server B matching the M3 acceptance test scenarios:
+ *     - Scope variant A: tasks + notes, include_personal: true
+ *     - Scope variant B: tasks only, include_teams: ['T1'], exclude T2
+ *     - Scope variant C: tasks + credentials in resources, credentials excluded (sanity)
+ *  5. For each grant, walks the full enrollment flow:
+ *       a. Server B creates a peer keypair (represents the requesting side).
+ *       b. Server B creates the grant referencing that peer.
+ *       c. Server B issues an enrollment token.
+ *       d. Server A creates its own peer keypair (represents its view of B).
+ *       e. Server A redeems the enrollment token at Server B's enrollment endpoint,
+ *          submitting A's CSR → receives signed cert back.
+ *       f. Server A stores the cert on its peer record → peer becomes active.
+ *  6. Inserts representative test tasks/notes/credentials on Server B.
+ *
+ * IMPORTANT: This script uses the real admin REST API — no direct DB writes.
+ * It exercises the full enrollment flow as M3 acceptance tests will.
+ *
+ * ESM / NodeNext: all imports use .js extensions.
+ */
+
+import { execSync } from 'node:child_process';
+import { resolve, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+// ─── Constants ───────────────────────────────────────────────────────────────
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const COMPOSE_FILE = resolve(__dirname, 'docker-compose.two-gateways.yml');
+
+/** Base URLs as seen from the host machine (mapped host ports). */
+const SERVER_A_URL = process.env['GATEWAY_A_URL'] ?? 'http://localhost:14001';
+const SERVER_B_URL = process.env['GATEWAY_B_URL'] ?? 'http://localhost:14002';
+
+/**
+ * Bootstrap passwords used when calling POST /api/bootstrap/setup on each
+ * gateway. Each gateway starts with zero users and requires a one-time setup
+ * call before any admin-guarded endpoints can be used.
+ */
+const ADMIN_BOOTSTRAP_PASSWORD_A =
+  process.env['ADMIN_BOOTSTRAP_PASSWORD_A'] ?? 'harness-admin-password-a';
+const ADMIN_BOOTSTRAP_PASSWORD_B =
+  process.env['ADMIN_BOOTSTRAP_PASSWORD_B'] ?? 'harness-admin-password-b';
+
+const READINESS_TIMEOUT_MS = 120_000;
+const READINESS_POLL_MS = 3_000;
+
+// ─── Scope variant definitions (for M3 acceptance tests) ─────────────────────
+
+/** Scope variant A — tasks + notes, personal data included. */
+export const SCOPE_VARIANT_A = {
+  resources: ['tasks', 'notes'],
+  filters: {
+    tasks: { include_personal: true },
+    notes: { include_personal: true },
+  },
+  excluded_resources: [] as string[],
+  max_rows_per_query: 500,
+};
+
+/** Scope variant B — tasks only, team T1 only, no personal. */
+export const SCOPE_VARIANT_B = {
+  resources: ['tasks'],
+  filters: {
+    tasks: { include_teams: ['T1'], include_personal: false },
+  },
+  excluded_resources: [] as string[],
+  max_rows_per_query: 500,
+};
+
+/**
+ * Scope variant C — tasks + credentials in resources list, but credentials
+ * explicitly in excluded_resources. Sanity test: credentials must still be
+ * inaccessible even though they appear in resources.
+ */
+export const SCOPE_VARIANT_C = {
+  resources: ['tasks', 'credentials'],
+  filters: {
+    tasks: { include_personal: true },
+  },
+  excluded_resources: ['credentials'],
+  max_rows_per_query: 500,
+};
+
+// ─── Inline types (no import from packages/types — M3-01 branch not yet merged) ─
+
+interface AdminFetchOptions {
+  method?: string;
+  body?: unknown;
+  adminToken: string;
+}
+
+interface PeerRecord {
+  peerId: string;
+  csrPem: string;
+}
+
+interface GrantRecord {
+  id: string;
+  status: string;
+  scope: unknown;
+}
+
+interface EnrollmentTokenResult {
+  token: string;
+  expiresAt: string;
+  enrollmentUrl: string;
+}
+
+interface EnrollmentRedeemResult {
+  certPem: string;
+  certChainPem: string;
+}
+
+interface BootstrapResult {
+  adminUserId: string;
+  adminToken: string;
+}
+
+export interface SeedResult {
+  serverAUrl: string;
+  serverBUrl: string;
+  adminTokenA: string;
+  adminTokenB: string;
+  adminUserIdA: string;
+  adminUserIdB: string;
+  grants: {
+    variantA: GrantRecord;
+    variantB: GrantRecord;
+    variantC: GrantRecord;
+  };
+  peers: {
+    variantA: PeerRecord & { grantId: string };
+    variantB: PeerRecord & { grantId: string };
+    variantC: PeerRecord & { grantId: string };
+  };
+}
+
+// ─── HTTP helpers ─────────────────────────────────────────────────────────────
+
+/**
+ * Authenticated admin fetch. Sends `Authorization: Bearer <adminToken>` which
+ * is the only path supported by AdminGuard (DB-backed sha256 token lookup).
+ * No `x-admin-key` header path exists in the gateway.
+ */
+async function adminFetch<T>(baseUrl: string, path: string, opts: AdminFetchOptions): Promise<T> {
+  const url = `${baseUrl}${path}`;
+  const res = await fetch(url, {
+    method: opts.method ?? 'GET',
+    headers: {
+      'Content-Type': 'application/json',
+      Authorization: `Bearer ${opts.adminToken}`,
+    },
+    body: opts.body !== undefined ? JSON.stringify(opts.body) : undefined,
+  });
+
+  if (!res.ok) {
+    const text = await res.text().catch(() => '(no body)');
+    throw new Error(`${opts.method ?? 'GET'} ${url} → ${res.status}: ${text}`);
+  }
+
+  return res.json() as Promise<T>;
+}
+
+// ─── Admin bootstrap ──────────────────────────────────────────────────────────
+
+/**
+ * Bootstrap an admin user on a pristine gateway.
+ *
+ * Steps:
+ *  1. GET /api/bootstrap/status — confirms needsSetup === true.
+ *  2. POST /api/bootstrap/setup with { name, email, password } — returns
+ *     { user, token: { plaintext } }.
+ *
+ * The harness assumes a fresh DB. If needsSetup is false the harness fails
+ * fast with a clear error rather than proceeding with an unknown token.
+ */
+async function bootstrapAdmin(
+  baseUrl: string,
+  label: string,
+  password: string,
+): Promise<BootstrapResult> {
+  console.log(`[seed] Bootstrapping admin on ${label} (${baseUrl})...`);
+
+  // 1. Check status
+  const statusRes = await fetch(`${baseUrl}/api/bootstrap/status`);
+  if (!statusRes.ok) {
+    throw new Error(`[seed] GET ${baseUrl}/api/bootstrap/status → ${statusRes.status.toString()}`);
+  }
+  const status = (await statusRes.json()) as { needsSetup: boolean };
+
+  if (!status.needsSetup) {
+    throw new Error(
+      `[seed] ${label} at ${baseUrl} already has users (needsSetup=false). ` +
+        `The harness requires a pristine database. Run 'docker compose down -v' to reset.`,
+    );
+  }
+
+  // 2. Bootstrap
+  const setupRes = await fetch(`${baseUrl}/api/bootstrap/setup`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      name: `Harness Admin (${label})`,
+      email: `harness-admin-${label.toLowerCase().replace(/\s+/g, '-')}@example.invalid`,
+      password,
+    }),
+  });
+
+  if (!setupRes.ok) {
+    const body = await setupRes.text().catch(() => '(no body)');
+    throw new Error(
+      `[seed] POST ${baseUrl}/api/bootstrap/setup → ${setupRes.status.toString()}: ${body}`,
+    );
+  }
+
+  const result = (await setupRes.json()) as {
+    user: { id: string };
+    token: { plaintext: string };
+  };
+
+  console.log(`[seed]   ${label} admin user: ${result.user.id}`);
+  console.log(`[seed]   ${label} admin token: ${result.token.plaintext.slice(0, 8)}...`);
+
+  return {
+    adminUserId: result.user.id,
+    adminToken: result.token.plaintext,
+  };
+}
+
+// ─── Readiness probe ──────────────────────────────────────────────────────────
+
+async function waitForGateway(baseUrl: string, label: string): Promise<void> {
+  const deadline = Date.now() + READINESS_TIMEOUT_MS;
+  let lastError: string = '';
+
+  while (Date.now() < deadline) {
+    try {
+      const res = await fetch(`${baseUrl}/api/health`, { signal: AbortSignal.timeout(5_000) });
+      if (res.ok) {
+        console.log(`[seed] ${label} is ready (${baseUrl})`);
+        return;
+      }
+      lastError = `HTTP ${res.status.toString()}`;
+    } catch (err) {
+      lastError = err instanceof Error ? err.message : String(err);
+    }
+    await new Promise((r) => setTimeout(r, READINESS_POLL_MS));
+  }
+
+  throw new Error(
+    `[seed] ${label} did not become ready within ${READINESS_TIMEOUT_MS.toString()}ms — last error: ${lastError}`,
+  );
+}
+
+// ─── Enrollment flow ──────────────────────────────────────────────────────────
+
+/**
+ * Walk the full enrollment flow for one grant.
+ *
+ * The correct two-sided flow (matching the data model's FK semantics):
+ *
+ *  1. On Server B: POST /api/admin/federation/peers/keypair
+ *       → peerId_B (Server B's peer record representing the requesting side)
+ *  2. On Server B: POST /api/admin/federation/grants with peerId: peerId_B
+ *       → grant (FK to Server B's own federation_peers table — no violation)
+ *  3. On Server B: POST /api/admin/federation/grants/:id/tokens
+ *       → enrollmentUrl pointing back to Server B
+ *  4. On Server A: POST /api/admin/federation/peers/keypair
+ *       → peerId_A + csrPem_A (Server A's local record of Server B)
+ *  5. Server A → Server B: POST enrollmentUrl with { csrPem: csrPem_A }
+ *       → certPem signed by Server B's CA
+ *  6. On Server A: PATCH /api/admin/federation/peers/:peerId_A/cert with certPem
+ *       → Server A's peer record transitions to active
+ *
+ * Returns the activated grant (from Server B) and Server A's peer record.
+ */
+async function enrollGrant(opts: {
+  label: string;
+  subjectUserId: string;
+  scope: unknown;
+  adminTokenA: string;
+  adminTokenB: string;
+  serverAUrl: string;
+  serverBUrl: string;
+}): Promise<{ grant: GrantRecord; peer: PeerRecord & { grantId: string } }> {
+  const { label, subjectUserId, scope, adminTokenA, adminTokenB, serverAUrl, serverBUrl } = opts;
+  console.log(`\n[seed] Enrolling grant for scope variant ${label}...`);
+
+  // 1. Create peer keypair on Server B (represents the requesting peer from B's perspective)
+  const peerB = await adminFetch<PeerRecord>(serverBUrl, '/api/admin/federation/peers/keypair', {
+    method: 'POST',
+    adminToken: adminTokenB,
+    body: {
+      commonName: `harness-peer-${label.toLowerCase()}-from-b`,
+      displayName: `Harness Peer ${label} (Server A as seen from B)`,
+      endpointUrl: serverAUrl,
+    },
+  });
+  console.log(`[seed]   Created peer on B: ${peerB.peerId}`);
+
+  // 2. Create grant on Server B referencing B's own peer record
+  const grant = await adminFetch<GrantRecord>(serverBUrl, '/api/admin/federation/grants', {
+    method: 'POST',
+    adminToken: adminTokenB,
+    body: {
+      peerId: peerB.peerId,
+      subjectUserId,
+      scope,
+    },
+  });
+  console.log(`[seed]   Created grant on B: ${grant.id} (status: ${grant.status})`);
+
+  // 3. Generate enrollment token on Server B
+  const tokenResult = await adminFetch<EnrollmentTokenResult>(
+    serverBUrl,
+    `/api/admin/federation/grants/${grant.id}/tokens`,
+    { method: 'POST', adminToken: adminTokenB, body: { ttlSeconds: 900 } },
+  );
+  console.log(`[seed]   Enrollment token: ${tokenResult.token.slice(0, 8)}...`);
+  console.log(`[seed]   Enrollment URL: ${tokenResult.enrollmentUrl}`);
+
+  // 4. Create peer keypair on Server A (Server A's local record of Server B)
+  const peerA = await adminFetch<PeerRecord>(serverAUrl, '/api/admin/federation/peers/keypair', {
+    method: 'POST',
+    adminToken: adminTokenA,
+    body: {
+      commonName: `harness-peer-${label.toLowerCase()}-from-a`,
+      displayName: `Harness Peer ${label} (Server B as seen from A)`,
+      endpointUrl: serverBUrl,
+    },
+  });
+  console.log(`[seed]   Created peer on A: ${peerA.peerId}`);
+
+  // 5. Redeem token at Server B's enrollment endpoint with A's CSR.
+  //    The enrollment endpoint is not admin-guarded — the one-time token IS the credential.
+  //
+  //    The enrollmentUrl returned by the gateway is built using BETTER_AUTH_URL which
+  //    resolves to the in-cluster Docker hostname (gateway-b:3000). That URL is only
+  //    reachable from other containers, not from the host machine running this script.
+  //    We rewrite the host portion to use the host-accessible serverBUrl so the
+  //    seed script can reach the endpoint from the host.
+  const parsedEnrollment = new URL(tokenResult.enrollmentUrl);
+  const tokenSegment = parsedEnrollment.pathname.split('/').pop()!;
+  const redeemUrl = `${serverBUrl}/api/federation/enrollment/${tokenSegment}`;
+  console.log(`[seed]   Rewritten redeem URL (host-accessible): ${redeemUrl}`);
+  const redeemRes = await fetch(redeemUrl, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ csrPem: peerA.csrPem }),
+  });
+
+  if (!redeemRes.ok) {
+    const body = await redeemRes.text().catch(() => '(no body)');
+    throw new Error(`Enrollment redemption failed: ${redeemRes.status.toString()} — ${body}`);
+  }
+
+  const redeemResult = (await redeemRes.json()) as EnrollmentRedeemResult;
+  console.log(`[seed]   Cert issued (${redeemResult.certPem.length.toString()} bytes)`);
+
+  // 6. Store cert on Server A's peer record → transitions to active
+  await adminFetch<unknown>(serverAUrl, `/api/admin/federation/peers/${peerA.peerId}/cert`, {
+    method: 'PATCH',
+    adminToken: adminTokenA,
+    body: { certPem: redeemResult.certPem },
+  });
+  console.log(`[seed]   Cert stored on A — peer ${peerA.peerId} is now active`);
+
+  // Verify grant flipped to active on B
+  const activeGrant = await adminFetch<GrantRecord>(
+    serverBUrl,
+    `/api/admin/federation/grants/${grant.id}`,
+    { adminToken: adminTokenB },
+  );
+  console.log(`[seed]   Grant status on B: ${activeGrant.status}`);
+
+  return { grant: activeGrant, peer: { ...peerA, grantId: grant.id } };
+}
+
+// ─── Test data insertion ──────────────────────────────────────────────────────
+
+/**
+ * Insert representative test data on Server B via its admin APIs.
+ *
+ * NOTE: The gateway's task/note/credential APIs require an authenticated user
+ * session. For the harness, we seed via admin-level endpoints if available,
+ * or document the gap here for M3-11 to fill in with proper user session seeding.
+ *
+ * ASSUMPTION: Server B exposes POST /api/admin/tasks (or similar) for test data.
+ * If that endpoint does not yet exist, this function logs a warning and skips
+ * without failing — M3-11 will add the session-based seeding path.
+ */
+async function seedTestData(
+  subjectUserId: string,
+  scopeLabel: string,
+  serverBUrl: string,
+  adminTokenB: string,
+): Promise<void> {
+  console.log(`\n[seed] Seeding test data on Server B for ${scopeLabel}...`);
+
+  const testTasks = [
+    {
+      title: `${scopeLabel} Task 1`,
+      description: 'Federation harness test task',
+      userId: subjectUserId,
+    },
+    {
+      title: `${scopeLabel} Task 2`,
+      description: 'Team-scoped test task',
+      userId: subjectUserId,
+      teamId: 'T1',
+    },
+  ];
+
+  const testNotes = [
+    {
+      title: `${scopeLabel} Note 1`,
+      content: 'Personal note for federation test',
+      userId: subjectUserId,
+    },
+  ];
+
+  // Attempt to insert — tolerate 404 (endpoint not yet implemented)
+  for (const task of testTasks) {
+    try {
+      await adminFetch<unknown>(serverBUrl, '/api/admin/tasks', {
+        method: 'POST',
+        adminToken: adminTokenB,
+        body: task,
+      });
+      console.log(`[seed]   Inserted task: "${task.title}"`);
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : String(err);
+      if (msg.includes('404') || msg.includes('Cannot POST')) {
+        console.warn(
+          `[seed]   WARN: /api/admin/tasks not found — skipping task insertion (expected until M3-11)`,
+        );
+        break;
+      }
+      throw err;
+    }
+  }
+
+  for (const note of testNotes) {
+    try {
+      await adminFetch<unknown>(serverBUrl, '/api/admin/notes', {
+        method: 'POST',
+        adminToken: adminTokenB,
+        body: note,
+      });
+      console.log(`[seed]   Inserted note: "${note.title}"`);
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : String(err);
+      if (msg.includes('404') || msg.includes('Cannot POST')) {
+        console.warn(
+          `[seed]   WARN: /api/admin/notes not found — skipping note insertion (expected until M3-11)`,
+        );
+        break;
+      }
+      throw err;
+    }
+  }
+
+  console.log(`[seed] Test data seeding for ${scopeLabel} complete.`);
+}
+
+// ─── Main entrypoint ──────────────────────────────────────────────────────────
+
+export async function runSeed(opts?: {
+  serverAUrl?: string;
+  serverBUrl?: string;
+  adminBootstrapPasswordA?: string;
+  adminBootstrapPasswordB?: string;
+  subjectUserIds?: { variantA: string; variantB: string; variantC: string };
+}): Promise<SeedResult> {
+  const aUrl = opts?.serverAUrl ?? SERVER_A_URL;
+  const bUrl = opts?.serverBUrl ?? SERVER_B_URL;
+  const passwordA = opts?.adminBootstrapPasswordA ?? ADMIN_BOOTSTRAP_PASSWORD_A;
+  const passwordB = opts?.adminBootstrapPasswordB ?? ADMIN_BOOTSTRAP_PASSWORD_B;
+
+  // Use provided or default subject user IDs.
+  // In a real run these would be real user UUIDs from Server B's DB.
+  // For the harness, the admin bootstrap user on Server B is used as the subject.
+  // These are overridden after bootstrap if opts.subjectUserIds is not provided.
+  const subjectIds = opts?.subjectUserIds;
+
+  console.log('[seed] Waiting for gateways to be ready...');
+  await Promise.all([waitForGateway(aUrl, 'Server A'), waitForGateway(bUrl, 'Server B')]);
+
+  // Bootstrap admin users on both gateways (requires pristine DBs).
+  console.log('\n[seed] Bootstrapping admin accounts...');
+  const [bootstrapA, bootstrapB] = await Promise.all([
+    bootstrapAdmin(aUrl, 'Server A', passwordA),
+    bootstrapAdmin(bUrl, 'Server B', passwordB),
+  ]);
+
+  // Default subject user IDs to the admin user on Server B (guaranteed to exist).
+  const resolvedSubjectIds = subjectIds ?? {
+    variantA: bootstrapB.adminUserId,
+    variantB: bootstrapB.adminUserId,
+    variantC: bootstrapB.adminUserId,
+  };
+
+  // Enroll all three scope variants sequentially to avoid race conditions on
+  // the step-ca signing queue. Parallel enrollment would work too but
+  // sequential is easier to debug when something goes wrong.
+  console.log('\n[seed] Enrolling scope variants...');
+  const resultA = await enrollGrant({
+    label: 'A',
+    subjectUserId: resolvedSubjectIds.variantA,
+    scope: SCOPE_VARIANT_A,
+    adminTokenA: bootstrapA.adminToken,
+    adminTokenB: bootstrapB.adminToken,
+    serverAUrl: aUrl,
+    serverBUrl: bUrl,
+  });
+  const resultB = await enrollGrant({
+    label: 'B',
+    subjectUserId: resolvedSubjectIds.variantB,
+    scope: SCOPE_VARIANT_B,
+    adminTokenA: bootstrapA.adminToken,
+    adminTokenB: bootstrapB.adminToken,
+    serverAUrl: aUrl,
+    serverBUrl: bUrl,
+  });
+  const resultC = await enrollGrant({
+    label: 'C',
+    subjectUserId: resolvedSubjectIds.variantC,
+    scope: SCOPE_VARIANT_C,
+    adminTokenA: bootstrapA.adminToken,
+    adminTokenB: bootstrapB.adminToken,
+    serverAUrl: aUrl,
+    serverBUrl: bUrl,
+  });
+
+  // Seed test data on Server B for each scope variant
+  await Promise.all([
+    seedTestData(resolvedSubjectIds.variantA, 'A', bUrl, bootstrapB.adminToken),
+    seedTestData(resolvedSubjectIds.variantB, 'B', bUrl, bootstrapB.adminToken),
+    seedTestData(resolvedSubjectIds.variantC, 'C', bUrl, bootstrapB.adminToken),
+  ]);
+
+  const result: SeedResult = {
+    serverAUrl: aUrl,
+    serverBUrl: bUrl,
+    adminTokenA: bootstrapA.adminToken,
+    adminTokenB: bootstrapB.adminToken,
+    adminUserIdA: bootstrapA.adminUserId,
+    adminUserIdB: bootstrapB.adminUserId,
+    grants: {
+      variantA: resultA.grant,
+      variantB: resultB.grant,
+      variantC: resultC.grant,
+    },
+    peers: {
+      variantA: resultA.peer,
+      variantB: resultB.peer,
+      variantC: resultC.peer,
+    },
+  };
+
+  console.log('\n[seed] Seed complete.');
+  console.log('[seed] Summary:');
+  console.log(`  Variant A grant: ${result.grants.variantA.id} (${result.grants.variantA.status})`);
+  console.log(`  Variant B grant: ${result.grants.variantB.id} (${result.grants.variantB.status})`);
+  console.log(`  Variant C grant: ${result.grants.variantC.id} (${result.grants.variantC.status})`);
+
+  return result;
+}
+
+// ─── CLI entry ────────────────────────────────────────────────────────────────
+
+const isCli =
+  process.argv[1] != null &&
+  fileURLToPath(import.meta.url).endsWith(process.argv[1]!.split('/').pop()!);
+
+if (isCli) {
+  const shouldBoot = process.argv.includes('--boot');
+
+  if (shouldBoot) {
+    console.log('[seed] --boot flag detected — starting compose stack...');
+    execSync(`docker compose -f "${COMPOSE_FILE}" up -d`, { stdio: 'inherit' });
+  }
+
+  runSeed()
+    .then(() => {
+      process.exit(0);
+    })
+    .catch((err) => {
+      console.error('[seed] Fatal:', err);
+      process.exit(1);
+    });
+}