From 6a3824fbb0d5538af2a3c9a9fc578575ec9d96f5 Mon Sep 17 00:00:00 2001
From: Gift Amadi <120387225+giftexceed@users.noreply.github.com>
Date: Mon, 22 Jun 2026 15:40:01 +0000
Subject: [PATCH] fix(listener): return after handling GET
 /api/preferences/:userId

The GET preferences handler wrote its response but did not return, so
execution fell through to the catch-all 404 handler, which called
res.writeHead() again and threw "Cannot write headers after they are
sent to the client". Add the explicit 200 + JSON content-type header and
return after responding, matching the other route handlers.

Fixes the failing "GET /api/preferences/:userId returns preferences for
the given user" test in events-server.test.ts.
---
 listener/src/api/events-server.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/listener/src/api/events-server.ts b/listener/src/api/events-server.ts
index 197e189..a99fbb7 100644
--- a/listener/src/api/events-server.ts
+++ b/listener/src/api/events-server.ts
@@ -484,7 +484,9 @@ export function createEventsServer(options: EventsServerOptions): http.Server {
       const userId = decodeURIComponent(getPrefsMatch[1]);
       logger.info('Handling GET /api/preferences/:userId', { requestId, correlationId, userId });
       const prefs = preferenceStore.get(userId);
+      res.writeHead(200, { 'Content-Type': 'application/json' });
       res.end(JSON.stringify(prefs));
+      return;
     }
 
     // PUT /api/preferences/:userId