diff --git a/packages/iios-service/src/identity/identity.module.ts b/packages/iios-service/src/identity/identity.module.ts
index 83433ec..f88a8cd 100644
--- a/packages/iios-service/src/identity/identity.module.ts
+++ b/packages/iios-service/src/identity/identity.module.ts
@@ -1,9 +1,10 @@
 import { Global, Module } from '@nestjs/common';
 import { ActorResolver } from './actor.resolver';
+import { SessionVerifier } from '../platform/session.verifier';
 
 @Global()
 @Module({
-  providers: [ActorResolver],
-  exports: [ActorResolver],
+  providers: [ActorResolver, SessionVerifier],
+  exports: [ActorResolver, SessionVerifier],
 })
 export class IdentityModule {}
diff --git a/packages/iios-service/src/inbox/inbox.controller.ts b/packages/iios-service/src/inbox/inbox.controller.ts
new file mode 100644
index 0000000..bcdfc48
--- /dev/null
+++ b/packages/iios-service/src/inbox/inbox.controller.ts
@@ -0,0 +1,34 @@
+import { BadRequestException, Body, Controller, Get, Headers, Param, Patch, Query } from '@nestjs/common';
+import { IiosInboxState } from '@prisma/client';
+import { InboxService } from './inbox.service';
+import { SessionVerifier } from '../platform/session.verifier';
+import { PatchInboxDto } from './inbox.dto';
+import type { MessagePrincipal } from '../identity/actor.resolver';
+
+@Controller('v1/inbox')
+export class InboxController {
+  constructor(
+    private readonly inbox: InboxService,
+    private readonly session: SessionVerifier,
+  ) {}
+
+  @Get('items')
+  async list(@Headers('authorization') authorization?: string, @Query('state') state?: string) {
+    return this.inbox.list(this.principal(authorization), { state: state as IiosInboxState | undefined });
+  }
+
+  @Patch('items/:id')
+  async patch(
+    @Param('id') id: string,
+    @Body() body: PatchInboxDto,
+    @Headers('authorization') authorization?: string,
+  ) {
+    return this.inbox.transition(id, this.principal(authorization), body.state, body.reason);
+  }
+
+  private principal(authorization?: string): MessagePrincipal {
+    const token = (authorization ?? '').replace(/^Bearer\s+/i, '');
+    if (!token) throw new BadRequestException('Authorization bearer token is required');
+    return this.session.verify(token);
+  }
+}
diff --git a/packages/iios-service/src/inbox/inbox.dto.ts b/packages/iios-service/src/inbox/inbox.dto.ts
new file mode 100644
index 0000000..36eae91
--- /dev/null
+++ b/packages/iios-service/src/inbox/inbox.dto.ts
@@ -0,0 +1,8 @@
+import { IsIn, IsOptional, IsString } from 'class-validator';
+
+const STATES = ['OPEN', 'SNOOZED', 'DONE', 'ARCHIVED', 'CANCELLED', 'STALE'] as const;
+
+export class PatchInboxDto {
+  @IsIn(STATES) state!: (typeof STATES)[number];
+  @IsOptional() @IsString() reason?: string;
+}
diff --git a/packages/iios-service/src/inbox/inbox.module.ts b/packages/iios-service/src/inbox/inbox.module.ts
index 8c324b2..593683d 100644
--- a/packages/iios-service/src/inbox/inbox.module.ts
+++ b/packages/iios-service/src/inbox/inbox.module.ts
@@ -1,10 +1,13 @@
 import { Module } from '@nestjs/common';
 import { OutboxModule } from '../outbox/outbox.module';
 import { InboxProjector } from './inbox.projector';
+import { InboxService } from './inbox.service';
+import { InboxController } from './inbox.controller';
 
 @Module({
   imports: [OutboxModule],
-  providers: [InboxProjector],
-  exports: [InboxProjector],
+  controllers: [InboxController],
+  providers: [InboxProjector, InboxService],
+  exports: [InboxProjector, InboxService],
 })
 export class InboxModule {}
diff --git a/packages/iios-service/src/inbox/inbox.service.ts b/packages/iios-service/src/inbox/inbox.service.ts
new file mode 100644
index 0000000..5d54e3f
--- /dev/null
+++ b/packages/iios-service/src/inbox/inbox.service.ts
@@ -0,0 +1,63 @@
+import { BadRequestException, ForbiddenException, Inject, Injectable, NotFoundException } from '@nestjs/common';
+import { IiosInboxState } from '@prisma/client';
+import type { IiosPlatformPorts } from '@insignia/iios-contracts';
+import { PrismaService } from '../prisma/prisma.service';
+import { PLATFORM_PORTS } from '../platform/platform-ports';
+import { decideOrThrow } from '../platform/fail-closed';
+import { ActorResolver, type MessagePrincipal } from '../identity/actor.resolver';
+
+/** Allowed inbox state transitions. */
+const TRANSITIONS: Record<IiosInboxState, IiosInboxState[]> = {
+  OPEN: ['SNOOZED', 'DONE', 'STALE', 'ARCHIVED'],
+  SNOOZED: ['OPEN', 'DONE', 'STALE', 'ARCHIVED'],
+  DONE: ['OPEN', 'ARCHIVED'],
+  STALE: ['OPEN', 'ARCHIVED'],
+  ARCHIVED: [],
+  CANCELLED: [],
+};
+
+@Injectable()
+export class InboxService {
+  constructor(
+    private readonly prisma: PrismaService,
+    @Inject(PLATFORM_PORTS) private readonly ports: IiosPlatformPorts,
+    private readonly actors: ActorResolver,
+  ) {}
+
+  /** List the caller's items (optionally filtered by state). Fail-closed. */
+  async list(principal: MessagePrincipal, opts: { state?: IiosInboxState } = {}) {
+    await decideOrThrow(this.ports, { action: 'iios.inbox.list', scope: principal });
+    const scope = await this.actors.resolveScope(principal);
+    const actor = await this.actors.resolveActor(scope.id, principal);
+    return this.prisma.iiosInboxItem.findMany({
+      where: { ownerActorId: actor.id, ...(opts.state ? { state: opts.state } : {}) },
+      orderBy: [{ priority: 'asc' }, { updatedAt: 'desc' }],
+    });
+  }
+
+  /** Transition one of the caller's items. Validates the state machine + fails closed. */
+  async transition(
+    itemId: string,
+    principal: MessagePrincipal,
+    toState: IiosInboxState,
+    reason?: string,
+  ) {
+    const item = await this.prisma.iiosInboxItem.findUnique({ where: { id: itemId } });
+    if (!item) throw new NotFoundException('inbox item not found');
+    await decideOrThrow(this.ports, { action: 'iios.inbox.transition', itemId, scopeId: item.scopeId });
+
+    const actor = await this.actors.resolveActor(item.scopeId, principal);
+    if (item.ownerActorId !== actor.id) throw new ForbiddenException('not your inbox item');
+    if (!TRANSITIONS[item.state].includes(toState)) {
+      throw new BadRequestException(`illegal transition ${item.state} -> ${toState}`);
+    }
+
+    const [updated] = await this.prisma.$transaction([
+      this.prisma.iiosInboxItem.update({ where: { id: itemId }, data: { state: toState } }),
+      this.prisma.iiosInboxItemStateHistory.create({
+        data: { inboxItemId: itemId, fromState: item.state, toState, actorId: actor.id, reasonCode: reason },
+      }),
+    ]);
+    return updated;
+  }
+}
diff --git a/packages/iios-service/src/inbox/inbox.spec.ts b/packages/iios-service/src/inbox/inbox.spec.ts
index 532e5cd..f0e55f3 100644
--- a/packages/iios-service/src/inbox/inbox.spec.ts
+++ b/packages/iios-service/src/inbox/inbox.spec.ts
@@ -2,11 +2,12 @@ import { describe, it, expect, beforeAll, afterAll, beforeEach } from 'vitest';
 import { PrismaClient } from '@prisma/client';
 import { resetDb } from '../test-utils/reset-db';
 import { makeFakePorts } from '@insignia/iios-testkit';
-import { IIOS_EVENTS, type CloudEvent } from '@insignia/iios-contracts';
+import { IIOS_EVENTS, PolicyDeniedError, type CloudEvent } from '@insignia/iios-contracts';
 import { MessageService, type MessagePrincipal } from '../messaging/message.service';
 import { ActorResolver } from '../identity/actor.resolver';
 import { OutboxBus } from '../outbox/outbox.bus';
 import { InboxProjector } from './inbox.projector';
+import { InboxService } from './inbox.service';
 import type { PrismaService } from '../prisma/prisma.service';
 
 const url = process.env.DATABASE_URL ?? 'postgresql://iios:iios@localhost:5434/iios?schema=public';
@@ -103,3 +104,42 @@ describe('InboxProjector (P3 work surface)', () => {
     expect(history.length).toBeGreaterThanOrEqual(1);
   });
 });
+
+describe('InboxService (state machine + list)', () => {
+  const inbox = (ports = makeFakePorts()) => new InboxService(asService, ports, actors);
+
+  async function makeItemForBob(): Promise<string> {
+    const { threadId } = await ms().openThread(null, bob);
+    const scope = await prisma.iiosScope.findFirstOrThrow();
+    const item = await prisma.iiosInboxItem.create({
+      data: { scopeId: scope.id, ownerActorId: await actorIdFor('bob'), kind: 'NEEDS_REPLY', title: 't', threadId },
+    });
+    return item.id;
+  }
+
+  it('snooze / done / reopen / stale transitions land correctly and write history', async () => {
+    const svc = inbox();
+    const id = await makeItemForBob();
+    await svc.transition(id, bob, 'SNOOZED');
+    await svc.transition(id, bob, 'DONE');
+    await svc.transition(id, bob, 'OPEN'); // reopen
+    await svc.transition(id, bob, 'STALE');
+    expect((await prisma.iiosInboxItem.findUniqueOrThrow({ where: { id } })).state).toBe('STALE');
+    expect((await prisma.iiosInboxItemStateHistory.findMany({ where: { inboxItemId: id } })).length).toBe(4);
+  });
+
+  it('rejects an illegal transition', async () => {
+    const svc = inbox();
+    const id = await makeItemForBob();
+    await svc.transition(id, bob, 'ARCHIVED');
+    await expect(svc.transition(id, bob, 'OPEN')).rejects.toThrow(); // ARCHIVED has no out-transitions
+  });
+
+  it('list returns the owner OPEN items and is fail-closed', async () => {
+    await makeItemForBob();
+    expect((await inbox().list(bob, { state: 'OPEN' })).length).toBe(1);
+    const denied = makeFakePorts();
+    denied.opa.deny();
+    await expect(inbox(denied).list(bob, {})).rejects.toBeInstanceOf(PolicyDeniedError);
+  });
+});
diff --git a/packages/iios-service/src/messaging/message.module.ts b/packages/iios-service/src/messaging/message.module.ts
index 614e914..765dff1 100644
--- a/packages/iios-service/src/messaging/message.module.ts
+++ b/packages/iios-service/src/messaging/message.module.ts
@@ -1,12 +1,11 @@
 import { Module } from '@nestjs/common';
 import { MessageService } from './message.service';
 import { MessageGateway } from './message.gateway';
-import { SessionVerifier } from '../platform/session.verifier';
 import { OutboxModule } from '../outbox/outbox.module';
 
 @Module({
   imports: [OutboxModule],
-  providers: [MessageService, MessageGateway, SessionVerifier],
-  exports: [MessageService, SessionVerifier],
+  providers: [MessageService, MessageGateway],
+  exports: [MessageService],
 })
 export class MessageModule {}