diff --git a/src/channels/channels.controller.ts b/src/channels/channels.controller.ts
index 19f82c6..f131d09 100644
--- a/src/channels/channels.controller.ts
+++ b/src/channels/channels.controller.ts
@@ -54,4 +54,11 @@ export class ChannelsController {
     if (!userId) throw new UnauthorizedException('missing user');
     return this.channelsService.leaveChannel(channelId, userId);
   }
+
+  @Post(':id/close')
+  close(@Req() req: AuthedRequest, @Param('id') channelId: string) {
+    const userId = req.userId ?? '';
+    if (!userId) throw new UnauthorizedException('missing user');
+    return this.channelsService.closeChannel(channelId, userId);
+  }
 }
diff --git a/src/channels/channels.service.ts b/src/channels/channels.service.ts
index 63e02ea..1d66861 100644
--- a/src/channels/channels.service.ts
+++ b/src/channels/channels.service.ts
@@ -64,6 +64,18 @@ export class ChannelsService {
     return rows.map((r) => ({ userId: r.userId }));
   }
 
+  async closeChannel(channelId: string, userId: string) {
+    const channel = await this.channelRepo.findOne({ where: { id: channelId } });
+    if (!channel) throw new NotFoundException('channel not found');
+    const member = await this.memberRepo.findOne({ where: { channelId, userId } });
+    if (!member && !channel.isPublic) {
+      throw new ForbiddenException('not a channel member');
+    }
+    channel.closed = true;
+    await this.channelRepo.save(channel);
+    return { status: 'ok', channelId, closed: true };
+  }
+
   async joinChannel(channelId: string, userId: string) {
     const channel = await this.channelRepo.findOne({ where: { id: channelId } });
     if (!channel) throw new NotFoundException('channel not found');
diff --git a/src/entities/channel.entity.ts b/src/entities/channel.entity.ts
index 127a199..c21ee6b 100644
--- a/src/entities/channel.entity.ts
+++ b/src/entities/channel.entity.ts
@@ -31,6 +31,10 @@ export class Channel {
   @Column({ type: 'boolean', default: false })
   isPublic!: boolean;
 
+  // closed (e.g. discussion-complete): history readable, new posts rejected
+  @Column({ type: 'boolean', default: false })
+  closed!: boolean;
+
   @Index()
   @Column({ default: 0 })
   lastSeq!: number;
diff --git a/src/messaging/messaging.controller.ts b/src/messaging/messaging.controller.ts
index 72a97f3..f38693f 100644
--- a/src/messaging/messaging.controller.ts
+++ b/src/messaging/messaging.controller.ts
@@ -1,5 +1,6 @@
 import {
   Body,
+  ConflictException,
   Controller,
   Delete,
   Get,
@@ -143,6 +144,9 @@ export class MessagingController {
 
     const channel = await this.channelRepo.findOne({ where: { id: channelId } });
     if (!channel) throw new NotFoundException('channel not found');
+    if (channel.closed) {
+      throw new ConflictException({ error: 'channel_closed', message: 'channel is closed' });
+    }
     const xType = channel.xType ?? 'general';
     const isRotating = xType === 'discuss' || xType === 'work';
     const authorUserId = String(body.authorUserId ?? 'anonymous');