diff --git a/apps/gateway/src/federation/federation.module.ts b/apps/gateway/src/federation/federation.module.ts
index a2e01ef..da77bbf 100644
--- a/apps/gateway/src/federation/federation.module.ts
+++ b/apps/gateway/src/federation/federation.module.ts
@@ -6,7 +6,7 @@ import { EnrollmentService } from './enrollment.service.js';
 import { FederationController } from './federation.controller.js';
 import { GrantsService } from './grants.service.js';
 import { FederationClientService } from './client/index.js';
-import { FederationAuthGuard } from './server/index.js';
+import { FederationAuthGuard, FederationScopeService } from './server/index.js';
 
 @Module({
   controllers: [EnrollmentController, FederationController],
@@ -17,6 +17,7 @@ import { FederationAuthGuard } from './server/index.js';
     GrantsService,
     FederationClientService,
     FederationAuthGuard,
+    FederationScopeService,
   ],
   exports: [
     CaService,
@@ -24,6 +25,7 @@ import { FederationAuthGuard } from './server/index.js';
     GrantsService,
     FederationClientService,
     FederationAuthGuard,
+    FederationScopeService,
   ],
 })
 export class FederationModule {}
diff --git a/apps/gateway/src/federation/server/__tests__/scope.service.spec.ts b/apps/gateway/src/federation/server/__tests__/scope.service.spec.ts
new file mode 100644
index 0000000..0bbbe65
--- /dev/null
+++ b/apps/gateway/src/federation/server/__tests__/scope.service.spec.ts
@@ -0,0 +1,300 @@
+/**
+ * Unit tests for FederationScopeService (FED-M3-04).
+ *
+ * Coverage:
+ *  - resource allowlist deny
+ *  - excluded resource deny
+ *  - invalid scope deny
+ *  - invalid requested limit deny
+ *  - native RBAC deny as subjectUserId
+ *  - scope/native filter intersection for personal and team rows
+ *  - max_rows_per_query cap
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { FederationScopeService, type FederationNativeRbacEvaluator } from '../scope.service.js';
+import type { FederationContext } from '../federation-context.js';
+
+const GRANT_ID = 'grant-1';
+const PEER_ID = 'peer-1';
+const SUBJECT_USER_ID = 'user-1';
+
+function makeContext(scope: Record<string, unknown>): FederationContext {
+  return {
+    grantId: GRANT_ID,
+    peerId: PEER_ID,
+    subjectUserId: SUBJECT_USER_ID,
+    scope,
+  };
+}
+
+function makeNativeRbac(
+  result: Awaited<ReturnType<FederationNativeRbacEvaluator['evaluateReadAccess']>>,
+): FederationNativeRbacEvaluator {
+  return {
+    evaluateReadAccess: vi.fn().mockResolvedValue(result),
+  };
+}
+
+describe('FederationScopeService', () => {
+  let service: FederationScopeService;
+
+  beforeEach(() => {
+    service = new FederationScopeService();
+  });
+
+  it('allows a granted resource and returns a capped query filter', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: ['team-1', 'team-2'] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({
+        resources: ['tasks'],
+        filters: { tasks: { include_teams: ['team-1', 'team-3'], include_personal: true } },
+        max_rows_per_query: 50,
+      }),
+      resource: 'tasks',
+      requestedLimit: 500,
+      nativeRbac,
+    });
+
+    expect(result).toEqual({
+      allowed: true,
+      filter: {
+        resource: 'tasks',
+        subjectUserId: SUBJECT_USER_ID,
+        includePersonal: true,
+        teamIds: ['team-1'],
+        limit: 50,
+        maxRowsPerQuery: 50,
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).toHaveBeenCalledWith({
+      grantId: GRANT_ID,
+      peerId: PEER_ID,
+      subjectUserId: SUBJECT_USER_ID,
+      resource: 'tasks',
+    });
+  });
+
+  it('defaults absent resource filters to native RBAC personal and team visibility', async () => {
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: ['notes'], max_rows_per_query: 100 }),
+      resource: 'notes',
+      nativeRbac: makeNativeRbac({
+        allowed: true,
+        access: { includePersonal: true, teamIds: ['team-1', 'team-2'] },
+      }),
+    });
+
+    expect(result).toMatchObject({
+      allowed: true,
+      filter: {
+        includePersonal: true,
+        teamIds: ['team-1', 'team-2'],
+        limit: 100,
+      },
+    });
+  });
+
+  it('honors include_personal false even when native RBAC allows personal rows', async () => {
+    const result = await service.evaluateAccess({
+      context: makeContext({
+        resources: ['memory'],
+        filters: { memory: { include_personal: false } },
+        max_rows_per_query: 25,
+      }),
+      resource: 'memory',
+      nativeRbac: makeNativeRbac({
+        allowed: true,
+        access: { includePersonal: true, teamIds: [] },
+      }),
+    });
+
+    expect(result).toMatchObject({
+      allowed: true,
+      filter: {
+        includePersonal: false,
+        teamIds: [],
+      },
+    });
+  });
+
+  it('does not widen native RBAC when scope includes teams the user cannot access', async () => {
+    const result = await service.evaluateAccess({
+      context: makeContext({
+        resources: ['tasks'],
+        filters: { tasks: { include_teams: ['team-2'], include_personal: false } },
+        max_rows_per_query: 25,
+      }),
+      resource: 'tasks',
+      nativeRbac: makeNativeRbac({
+        allowed: true,
+        access: { includePersonal: true, teamIds: ['team-1'] },
+      }),
+    });
+
+    expect(result).toMatchObject({
+      allowed: true,
+      filter: {
+        includePersonal: false,
+        teamIds: [],
+      },
+    });
+  });
+
+  it('denies invalid grant scope before RBAC evaluation', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: [] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: [], max_rows_per_query: 100 }),
+      resource: 'tasks',
+      nativeRbac,
+    });
+
+    expect(result).toMatchObject({
+      allowed: false,
+      deny: {
+        code: 'invalid_scope',
+        stage: 'scope_parse',
+        statusCode: 400,
+        grantId: GRANT_ID,
+        subjectUserId: SUBJECT_USER_ID,
+        resource: 'tasks',
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).not.toHaveBeenCalled();
+  });
+
+  it('denies unsupported resource names before RBAC evaluation', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: [] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: ['tasks'], max_rows_per_query: 100 }),
+      resource: 'unknown_resource',
+      nativeRbac,
+    });
+
+    expect(result).toMatchObject({
+      allowed: false,
+      deny: {
+        code: 'invalid_resource',
+        stage: 'resource_allowlist',
+        statusCode: 403,
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).not.toHaveBeenCalled();
+  });
+
+  it('denies resources explicitly present in excluded_resources before allowlist miss', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: [] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({
+        resources: ['tasks'],
+        excluded_resources: ['credentials'],
+        max_rows_per_query: 100,
+      }),
+      resource: 'credentials',
+      nativeRbac,
+    });
+
+    expect(result).toMatchObject({
+      allowed: false,
+      deny: {
+        code: 'resource_excluded',
+        stage: 'resource_exclusion',
+        statusCode: 403,
+        resource: 'credentials',
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).not.toHaveBeenCalled();
+  });
+
+  it('denies supported resources that are not granted by scope', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: [] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: ['tasks'], max_rows_per_query: 100 }),
+      resource: 'notes',
+      nativeRbac,
+    });
+
+    expect(result).toMatchObject({
+      allowed: false,
+      deny: {
+        code: 'resource_not_granted',
+        stage: 'resource_allowlist',
+        statusCode: 403,
+        resource: 'notes',
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).not.toHaveBeenCalled();
+  });
+
+  it('denies invalid requested row limits before RBAC evaluation', async () => {
+    const nativeRbac = makeNativeRbac({
+      allowed: true,
+      access: { includePersonal: true, teamIds: [] },
+    });
+
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: ['tasks'], max_rows_per_query: 100 }),
+      resource: 'tasks',
+      requestedLimit: 0,
+      nativeRbac,
+    });
+
+    expect(result).toMatchObject({
+      allowed: false,
+      deny: {
+        code: 'invalid_limit',
+        stage: 'row_cap',
+        statusCode: 400,
+        details: { requestedLimit: 0 },
+      },
+    });
+    expect(nativeRbac.evaluateReadAccess).not.toHaveBeenCalled();
+  });
+
+  it('denies when native RBAC rejects subjectUserId access to the resource', async () => {
+    const result = await service.evaluateAccess({
+      context: makeContext({ resources: ['tasks'], max_rows_per_query: 100 }),
+      resource: 'tasks',
+      nativeRbac: makeNativeRbac({
+        allowed: false,
+        reason: 'read:tasks denied',
+        details: { permission: 'tasks:read' },
+      }),
+    });
+
+    expect(result).toEqual({
+      allowed: false,
+      deny: {
+        code: 'native_rbac_denied',
+        stage: 'native_rbac',
+        statusCode: 403,
+        message: 'read:tasks denied',
+        grantId: GRANT_ID,
+        peerId: PEER_ID,
+        subjectUserId: SUBJECT_USER_ID,
+        resource: 'tasks',
+        details: { permission: 'tasks:read' },
+      },
+    });
+  });
+});
diff --git a/apps/gateway/src/federation/server/index.ts b/apps/gateway/src/federation/server/index.ts
index d369e00..aee7306 100644
--- a/apps/gateway/src/federation/server/index.ts
+++ b/apps/gateway/src/federation/server/index.ts
@@ -10,4 +10,22 @@
  */
 
 export { FederationAuthGuard } from './federation-auth.guard.js';
+export { FederationScopeService } from './scope.service.js';
 export type { FederationContext } from './federation-context.js';
+export type {
+  FederationNativeRbacAccess,
+  FederationNativeRbacAllowedResult,
+  FederationNativeRbacDeniedResult,
+  FederationNativeRbacEvaluator,
+  FederationNativeRbacRequest,
+  FederationNativeRbacResult,
+  FederationScopeAllowedResult,
+  FederationScopeDeniedResult,
+  FederationScopeDenyCode,
+  FederationScopeDenyDetails,
+  FederationScopeDenyReason,
+  FederationScopeDenyStage,
+  FederationScopeEvaluationInput,
+  FederationScopeEvaluationResult,
+  FederationScopeQueryFilter,
+} from './scope.service.js';
diff --git a/apps/gateway/src/federation/server/scope.service.ts b/apps/gateway/src/federation/server/scope.service.ts
new file mode 100644
index 0000000..355d311
--- /dev/null
+++ b/apps/gateway/src/federation/server/scope.service.ts
@@ -0,0 +1,272 @@
+/**
+ * FederationScopeService — M3 server-side scope enforcement pipeline.
+ *
+ * Pure trust-boundary service: it validates the grant scope, asks an injected
+ * native RBAC evaluator what the subject user can read locally, intersects that
+ * answer with the federation scope filters, and returns a query filter for the
+ * verb controllers. The service performs no DB calls directly.
+ */
+
+import { Injectable } from '@nestjs/common';
+import {
+  FEDERATION_RESOURCE_VALUES,
+  type FederationResource,
+  FederationScopeError,
+  parseFederationScope,
+} from '../scope-schema.js';
+import type { FederationContext } from './federation-context.js';
+
+const federationResourceSet: ReadonlySet<string> = new Set<string>(FEDERATION_RESOURCE_VALUES);
+
+export type FederationScopeDenyStage =
+  | 'scope_parse'
+  | 'resource_allowlist'
+  | 'resource_exclusion'
+  | 'native_rbac'
+  | 'row_cap';
+
+export type FederationScopeDenyCode =
+  | 'invalid_scope'
+  | 'invalid_resource'
+  | 'resource_not_granted'
+  | 'resource_excluded'
+  | 'native_rbac_denied'
+  | 'invalid_limit';
+
+export type FederationScopeDenyStatus = 400 | 403;
+
+export interface FederationScopeDenyDetails {
+  readonly [key: string]: string | number | boolean | readonly string[];
+}
+
+export interface FederationScopeDenyReason {
+  readonly code: FederationScopeDenyCode;
+  readonly stage: FederationScopeDenyStage;
+  readonly statusCode: FederationScopeDenyStatus;
+  readonly message: string;
+  readonly grantId: string;
+  readonly peerId: string;
+  readonly subjectUserId: string;
+  readonly resource: string;
+  readonly details?: FederationScopeDenyDetails;
+}
+
+export interface FederationNativeRbacRequest {
+  readonly grantId: string;
+  readonly peerId: string;
+  readonly subjectUserId: string;
+  readonly resource: FederationResource;
+}
+
+export interface FederationNativeRbacAccess {
+  /** Whether this user may read personal rows for this resource. */
+  readonly includePersonal: boolean;
+
+  /** Team IDs this user may read for this resource under native RBAC. */
+  readonly teamIds: readonly string[];
+}
+
+export interface FederationNativeRbacAllowedResult {
+  readonly allowed: true;
+  readonly access: FederationNativeRbacAccess;
+}
+
+export interface FederationNativeRbacDeniedResult {
+  readonly allowed: false;
+  readonly reason?: string;
+  readonly details?: FederationScopeDenyDetails;
+}
+
+export type FederationNativeRbacResult =
+  | FederationNativeRbacAllowedResult
+  | FederationNativeRbacDeniedResult;
+
+export interface FederationNativeRbacEvaluator {
+  evaluateReadAccess(request: FederationNativeRbacRequest): Promise<FederationNativeRbacResult>;
+}
+
+export interface FederationScopeEvaluationInput {
+  readonly context: FederationContext;
+  readonly resource: string;
+  readonly requestedLimit?: number;
+  readonly nativeRbac: FederationNativeRbacEvaluator;
+}
+
+export interface FederationScopeQueryFilter {
+  readonly resource: FederationResource;
+  readonly subjectUserId: string;
+  readonly includePersonal: boolean;
+  readonly teamIds: readonly string[];
+  readonly limit: number;
+  readonly maxRowsPerQuery: number;
+}
+
+export interface FederationScopeAllowedResult {
+  readonly allowed: true;
+  readonly filter: FederationScopeQueryFilter;
+}
+
+export interface FederationScopeDeniedResult {
+  readonly allowed: false;
+  readonly deny: FederationScopeDenyReason;
+}
+
+export type FederationScopeEvaluationResult =
+  | FederationScopeAllowedResult
+  | FederationScopeDeniedResult;
+
+function isFederationResource(resource: string): resource is FederationResource {
+  return federationResourceSet.has(resource);
+}
+
+function uniqueStrings(values: readonly string[]): readonly string[] {
+  return Array.from(new Set<string>(values));
+}
+
+function intersectTeamIds(
+  nativeTeamIds: readonly string[],
+  scopedTeamIds: readonly string[] | undefined,
+): readonly string[] {
+  const uniqueNativeTeamIds = uniqueStrings(nativeTeamIds);
+
+  if (scopedTeamIds === undefined) {
+    return uniqueNativeTeamIds;
+  }
+
+  const nativeSet = new Set<string>(uniqueNativeTeamIds);
+  return uniqueStrings(scopedTeamIds).filter((teamId: string): boolean => nativeSet.has(teamId));
+}
+
+function makeDenyReason(params: {
+  readonly code: FederationScopeDenyCode;
+  readonly stage: FederationScopeDenyStage;
+  readonly statusCode?: FederationScopeDenyStatus;
+  readonly message: string;
+  readonly context: FederationContext;
+  readonly resource: string;
+  readonly details?: FederationScopeDenyDetails;
+}): FederationScopeDeniedResult {
+  return {
+    allowed: false,
+    deny: {
+      code: params.code,
+      stage: params.stage,
+      statusCode: params.statusCode ?? 403,
+      message: params.message,
+      grantId: params.context.grantId,
+      peerId: params.context.peerId,
+      subjectUserId: params.context.subjectUserId,
+      resource: params.resource,
+      ...(params.details !== undefined ? { details: params.details } : {}),
+    },
+  };
+}
+
+@Injectable()
+export class FederationScopeService {
+  async evaluateAccess(
+    input: FederationScopeEvaluationInput,
+  ): Promise<FederationScopeEvaluationResult> {
+    const { context, resource, requestedLimit, nativeRbac } = input;
+
+    let scope: ReturnType<typeof parseFederationScope>;
+    try {
+      scope = parseFederationScope(context.scope);
+    } catch (error: unknown) {
+      const message =
+        error instanceof FederationScopeError
+          ? 'Federation grant scope is invalid'
+          : 'Federation grant scope could not be parsed';
+      const details = error instanceof Error ? { reason: error.message } : undefined;
+      return makeDenyReason({
+        code: 'invalid_scope',
+        stage: 'scope_parse',
+        statusCode: 400,
+        message,
+        context,
+        resource,
+        ...(details !== undefined ? { details } : {}),
+      });
+    }
+
+    if (!isFederationResource(resource)) {
+      return makeDenyReason({
+        code: 'invalid_resource',
+        stage: 'resource_allowlist',
+        message: 'Requested federation resource is not supported',
+        context,
+        resource,
+        details: { supportedResources: FEDERATION_RESOURCE_VALUES },
+      });
+    }
+
+    if (scope.excluded_resources.includes(resource)) {
+      return makeDenyReason({
+        code: 'resource_excluded',
+        stage: 'resource_exclusion',
+        message: 'Requested federation resource is explicitly excluded by grant scope',
+        context,
+        resource,
+      });
+    }
+
+    if (!scope.resources.includes(resource)) {
+      return makeDenyReason({
+        code: 'resource_not_granted',
+        stage: 'resource_allowlist',
+        message: 'Requested federation resource is not granted by scope',
+        context,
+        resource,
+        details: { grantedResources: scope.resources },
+      });
+    }
+
+    if (requestedLimit !== undefined && (!Number.isInteger(requestedLimit) || requestedLimit < 1)) {
+      return makeDenyReason({
+        code: 'invalid_limit',
+        stage: 'row_cap',
+        statusCode: 400,
+        message: 'Requested row limit must be a positive integer',
+        context,
+        resource,
+        details: { requestedLimit },
+      });
+    }
+
+    const nativeResult = await nativeRbac.evaluateReadAccess({
+      grantId: context.grantId,
+      peerId: context.peerId,
+      subjectUserId: context.subjectUserId,
+      resource,
+    });
+
+    if (!nativeResult.allowed) {
+      return makeDenyReason({
+        code: 'native_rbac_denied',
+        stage: 'native_rbac',
+        message: nativeResult.reason ?? 'Subject user is not allowed to read this resource',
+        context,
+        resource,
+        ...(nativeResult.details !== undefined ? { details: nativeResult.details } : {}),
+      });
+    }
+
+    const scopeFilter = scope.filters?.[resource];
+    const includePersonal =
+      Boolean(scopeFilter?.include_personal ?? true) && nativeResult.access.includePersonal;
+    const teamIds = intersectTeamIds(nativeResult.access.teamIds, scopeFilter?.include_teams);
+    const limit = Math.min(requestedLimit ?? scope.max_rows_per_query, scope.max_rows_per_query);
+
+    return {
+      allowed: true,
+      filter: {
+        resource,
+        subjectUserId: context.subjectUserId,
+        includePersonal,
+        teamIds,
+        limit,
+        maxRowsPerQuery: scope.max_rows_per_query,
+      },
+    };
+  }
+}
diff --git a/docs/scratchpads/462-fed-m3-04-scope-service.md b/docs/scratchpads/462-fed-m3-04-scope-service.md
new file mode 100644
index 0000000..ed5d10c
--- /dev/null
+++ b/docs/scratchpads/462-fed-m3-04-scope-service.md
@@ -0,0 +1,60 @@
+# Scratchpad — FED-M3-04 Scope Service
+
+## Objective
+
+Implement `apps/gateway/src/federation/server/scope.service.ts` for the M3 inbound federation scope-enforcement pipeline.
+
+## Scope / Constraints
+
+- Task: FED-M3-04, issue #462.
+- Branch: `feat/federation-m3-scope-service` from `origin/main` @ 0.0.48.
+- Pure service: no direct DB access; native RBAC/data access is injected per evaluation call.
+- Reuse `parseFederationScope` from M2-03.
+- Workers do not edit `docs/federation/TASKS.md` per repo AGENTS.md.
+
+## Acceptance Criteria
+
+1. Resource allowlist and `excluded_resources` enforced.
+2. Native RBAC evaluated as `subjectUserId` through an injected evaluator.
+3. Scope filter intersection supports `include_teams` and `include_personal` without widening native RBAC.
+4. `max_rows_per_query` caps requested limits.
+5. Service returns `{ allowed: true, filter }` or a structured deny reason usable by M4 audit.
+6. Unit tests cover every deny path.
+
+## Plan
+
+1. Inspect existing federation scope/schema/auth guard contracts.
+2. Add pure `FederationScopeService` plus typed result/filter/deny interfaces.
+3. Add focused unit tests for happy paths, filter intersection, row cap, and deny paths.
+4. Export/register service for future verb controllers.
+5. Run situational tests, baseline gates, code review, then PR.
+
+## Budget
+
+- Provided model tier: sonnet.
+- Estimate from task row: 10K tokens.
+- Working cap assumption: keep implementation focused to FED-M3-04 surfaces only.
+
+## Progress
+
+- Intake complete; dirty base worktree avoided by creating isolated worktree at `/home/jarvis/src/mosaic-mono-v1-fed-m3-04`.
+- Project PRD and federation task spec reviewed.
+- Added `FederationScopeService` with structured allow/deny result types and injected native RBAC evaluator contract.
+- Added unit coverage for happy path, row cap, filter intersection, and every deny path.
+- Exported/registered the service for upcoming M3 verb controllers.
+
+## Verification Evidence
+
+- `pnpm --filter @mosaicstack/gateway test -- src/federation/server/__tests__/scope.service.spec.ts` — pass (10 tests).
+- `pnpm build` — pass (23 successful tasks).
+- `pnpm typecheck` — pass (41 successful tasks).
+- `pnpm lint` — pass (23 successful tasks).
+- `pnpm format:check` — pass.
+- `pnpm test` — pass after starting local `postgres`/`valkey` and running `pnpm --filter @mosaicstack/db db:push` for the DB-backed cross-user isolation suite (41 successful tasks; gateway 477 passed / 11 skipped).
+- Code review: `~/.config/mosaic/tools/codex/codex-code-review.sh --uncommitted` — approve, 0 findings.
+- Security review: `~/.config/mosaic/tools/codex/codex-security-review.sh --uncommitted` — risk none, 0 findings.
+
+## Risks / Blockers
+
+- Issue #462 is already closed in provider output; likely milestone tracking mismatch. Will still reference #462 in PR body unless orchestrator redirects.
+- Local full-test setup required `docker compose up -d postgres valkey` + `db:push`; containers were stopped with `docker compose down` after verification.