diff --git a/apps/api/src/openapi.ts b/apps/api/src/openapi.ts
index fd32b16..70b604d 100644
--- a/apps/api/src/openapi.ts
+++ b/apps/api/src/openapi.ts
@@ -213,6 +213,15 @@ export const SendMultipleMessagesRequest = z.object({
 	Data: z.string().optional().describe('The message payload; often empty'),
 })
 
+/**
+ * `POST /api/messages/v3/delete` JSON body — the messages the client is dropping from
+ * its inbox. Ids are the `Id` of a stored message, which this server has never issued:
+ * with no message store the list is only ever echoed back as accepted.
+ */
+export const DeleteMessagesRequest = z.object({
+	MessageIds: z.array(z.int()).describe('Ids of the messages to delete'),
+})
+
 /**
  * `POST /api/messages/v1/friendOnlineStatus` — how many of the caller's friends are
  * online, wrapped in the client's `{ success, value }` envelope.
diff --git a/apps/api/src/routes/social.ts b/apps/api/src/routes/social.ts
index 4cab4c6..56ea126 100644
--- a/apps/api/src/routes/social.ts
+++ b/apps/api/src/routes/social.ts
@@ -22,6 +22,7 @@ import { authedId, unauthorized } from '../http'
 import {
 	AckResponse,
 	AUTHED,
+	DeleteMessagesRequest,
 	ErrorResponse,
 	form,
 	FriendOnlineCountResponse,
@@ -624,6 +625,28 @@ export const socialRoutes = new Hono<App>({ strict: false })
 		}),
 		(c) => c.json([])
 	)
+	// The inbox's delete button. A POST rather than a DELETE because the ids arrive as
+	// a JSON array body — the client batches a multi-select into one call, and its HTTP
+	// layer only ever sends a body on POST/PUT.
+	.post(
+		'/api/messages/v3/delete',
+		describeRoute({
+			tags: ['Social'],
+			summary: 'Delete messages',
+			description:
+				'Drops the given messages from the caller’s inbox. Nothing happens: there is no ' +
+				'message store behind `GET /api/messages/v2/get` (the `MessageReceived` ' +
+				'notification is the whole delivery — see `POST /api/messages/v2/send`), so ' +
+				'there are no ids to match and nothing to remove.\n\n' +
+				'Accepted unconditionally and answered 200 with an empty body, which is what the ' +
+				'client wants: it removes the rows locally and re-reads the empty list either ' +
+				'way. Not auth-gated, for the same reason `GET /api/messages/v2/get` isn’t — ' +
+				'the call reaches no state to protect.',
+			requestBody: jsonBody(DeleteMessagesRequest, 'The messages to delete'),
+			responses: { 200: { description: 'Accepted (empty body)' } },
+		}),
+		(c) => c.body(null, 200)
+	)
 	// How many of the caller's friends are online — the friends panel's header count.
 	// Answered from the friend graph joined to live presence, so it agrees with the
 	// friends the panel then lists. Auth-gated: the count is the CALLER's own.
diff --git a/apps/api/src/test/integration/api.test.ts b/apps/api/src/test/integration/api.test.ts
index b3354c0..af2dc9a 100644
--- a/apps/api/src/test/integration/api.test.ts
+++ b/apps/api/src/test/integration/api.test.ts
@@ -3418,6 +3418,20 @@ describe('messages', () => {
 		expect(res.status).toBe(401)
 		expect(await pushed()).toEqual([])
 	})
+
+	test('POST /api/messages/v3/delete accepts anything with an empty 200', async () => {
+		// No message store, so no id can be real and nothing is gated — an unknown id, an
+		// empty list and a missing body all land the same way.
+		for (const body of [{ MessageIds: [1787377235629] }, { MessageIds: [] }, {}]) {
+			const res = await exports.default.fetch(`${ORIGIN}/api/messages/v3/delete`, {
+				method: 'POST',
+				headers: { 'Content-Type': 'application/json' },
+				body: JSON.stringify(body),
+			})
+			expect(res.status).toBe(200)
+			expect(await res.text()).toBe('')
+		}
+	})
 })
 
 describe('mutual friends', () => {
@@ -4837,6 +4851,7 @@ describe('openapi', () => {
 			'POST /api/messages/v1/friendOnlineStatus',
 			'POST /api/messages/v1/sendMultiple',
 			'POST /api/messages/v2/send',
+			'POST /api/messages/v3/delete',
 			'POST /api/playerReputation/v1/bulk',
 			'POST /api/playerReputation/v2/bulk',
 			'POST /api/playerevents/v1/bulkInvite',