diff --git a/frontend/src/app.d.ts b/frontend/src/app.d.ts
index da08e6d..785b0e4 100644
--- a/frontend/src/app.d.ts
+++ b/frontend/src/app.d.ts
@@ -1,12 +1,10 @@
-// See https://svelte.dev/docs/kit/types#app.d.ts
-// for information about these interfaces
+import type { ConvexHttpClient } from 'convex/browser';
+
 declare global {
 	namespace App {
-		// interface Error {}
-		// interface Locals {}
-		// interface PageData {}
-		// interface PageState {}
-		// interface Platform {}
+		interface Locals {
+			convex: ConvexHttpClient;
+		}
 	}
 }
 
diff --git a/frontend/src/hooks.server.ts b/frontend/src/hooks.server.ts
new file mode 100644
index 0000000..77eff0a
--- /dev/null
+++ b/frontend/src/hooks.server.ts
@@ -0,0 +1,8 @@
+import { ConvexHttpClient } from 'convex/browser';
+import { PUBLIC_CONVEX_URL } from '$env/static/public';
+import type { Handle } from '@sveltejs/kit';
+
+export const handle: Handle = async ({ event, resolve }) => {
+	event.locals.convex = new ConvexHttpClient(PUBLIC_CONVEX_URL);
+	return resolve(event);
+};
diff --git a/frontend/src/routes/[mnemonic]/+server.ts b/frontend/src/routes/[mnemonic]/+server.ts
new file mode 100644
index 0000000..e937f7e
--- /dev/null
+++ b/frontend/src/routes/[mnemonic]/+server.ts
@@ -0,0 +1,31 @@
+import { api } from '$lib/convex/_generated/api';
+import { error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+
+export const POST: RequestHandler = async ({ params, request, locals }) => {
+	const mnemonic = params.mnemonic;
+
+	const chatData = await locals.convex.query(api.chats.getByMnemonic, { mnemonic });
+	if (!chatData) {
+		throw error(404, 'Chat not found');
+	}
+
+	const contentType = request.headers.get('content-type') || 'image/jpeg';
+	const buffer = await request.arrayBuffer();
+	const base64 = Buffer.from(buffer).toString('base64');
+
+	const caption = request.headers.get('x-caption') || '';
+
+	await locals.convex.mutation(api.messages.create, {
+		chatId: chatData._id,
+		role: 'user',
+		content: caption,
+		source: 'web',
+		imageBase64: base64,
+		imageMediaType: contentType
+	});
+
+	return new Response(JSON.stringify({ ok: true }), {
+		headers: { 'Content-Type': 'application/json' }
+	});
+};