Server-Sent Events Disconnecting in Cursor Application
Your Cursor-generated application uses Server-Sent Events (SSE) for real-time updates (live notifications, streaming responses, dashboards), but the SSE connection drops after a few seconds or minutes. Users see the real-time feed freeze, and the browser's EventSource silently reconnects only to disconnect again in a loop.
SSE connections are long-lived HTTP connections that must stay open indefinitely. This conflicts with many infrastructure components that expect short request-response cycles. Reverse proxies, load balancers, serverless platforms, and CDNs all have default timeouts that terminate SSE connections prematurely.
The issue is often intermittent — it works fine during development where there's no proxy layer, but fails in production where Nginx, Cloudflare, or a serverless platform sits between the client and server.
Error Messages You Might See
Common Causes
- Reverse proxy timeout — Nginx, Apache, or Cloudflare terminates idle connections after 60-120 seconds by default
- Serverless function timeout — Vercel (30s), Netlify (26s), and Lambda (15min max) kill long-running functions, terminating the SSE stream
- No keep-alive heartbeat — Without periodic data sent on the connection, intermediaries assume it's dead and close it
- Missing SSE headers — The response lacks required headers like
Content-Type: text/event-stream,Cache-Control: no-cache, orConnection: keep-alive - Response buffering enabled — Nginx or Node.js response compression buffers SSE data instead of streaming it, causing events to arrive in batches or not at all
How to Fix It
- Send heartbeat comments every 15-30 seconds — Send SSE comment lines (
: heartbeat\n\n) at regular intervals to keep the connection alive through proxies and load balancers - Configure proxy timeouts — For Nginx: set
proxy_read_timeout 86400s;andproxy_buffering off;. For Cloudflare: enable WebSockets/SSE in the dashboard or use Cloudflare Tunnel - Disable response buffering — Add
X-Accel-Buffering: noheader for Nginx, and disable compression on SSE endpoints - Implement robust client reconnection — Use EventSource's built-in reconnection with a custom
retry:field, and includeLast-Event-IDhandling to resume from where the client left off - Avoid serverless for SSE — If your SSE needs long-lived connections, deploy on a traditional server (VPS, container) rather than serverless functions. Alternatively, use a managed service like Ably or Pusher
- Set correct response headers — Ensure every SSE endpoint sends:
Content-Type: text/event-stream,Cache-Control: no-cache,Connection: keep-alive
Real developers can help you.
Bastien Labelle
Full stack dev w/ 20+ years of experience
Rudra Bhikadiya
I build and fix web apps across Next.js, Node.js, and DBs.
Comfortable jumping into messy code, broken APIs, and mysterious bugs.
If your project works in theory but not in reality, I help close that gap.
Krishna Sai Kuncha
Experienced Professional Full stack Developer with 8+ years of experience across react, python, js, ts, golang and react-native. Developed inhouse websearch tooling for AI before websearch was solved : )
Anthony Akpan
Developer with 8 years of experience building softwares fro startups
Milan Surelia
Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems.
Expertise:
💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web.
🖋️ Sharing insights through technical writing, blogging, and open-source contributions.
🤝 Collaborating closely with designers, PMs, and developers to build seamless mobile experiences.
Notable Achievements:
🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX.
🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development.
🌟 Open source contributions on Github & StackOverflow for Flutter & Dart
🎖️ Worked on improving app performance and user experience with smart solutions.
Milan is always happy to connect, work on new ideas, and explore the latest in technology.
Yovel Cohen
I got a lot of experience in building Long-horizon AI Agents in production, Backend apps that scale to millions of users and frontend knowledge as well.
Prakash Prajapati
I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale.
Nam Tran
10 years as fullstack developer
Matthew Jordan
I've been working at a large software company named Kainos for 2 years, and mainly specialise in Platform Engineering. I regularly enjoy working on software products outside of work, and I'm a huge fan of game development using Unity. I personally enjoy Python & C# in my spare time, but I also specialise in multiple different platform-related technologies from my day job.
legrab
I'll fill this later
You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.
Get HelpFrequently Asked Questions
Can I use SSE with serverless platforms like Vercel?
Standard SSE with long-lived connections doesn't work well with serverless platforms due to function execution time limits. Vercel supports streaming responses for up to 30 seconds. For longer connections, use a dedicated WebSocket service (Ably, Pusher, Supabase Realtime) or deploy the SSE endpoint on a traditional server.
How is SSE different from WebSockets?
SSE is unidirectional (server to client only), uses standard HTTP, and has built-in reconnection. WebSockets are bidirectional, use a separate protocol (ws://), and require manual reconnection logic. Use SSE when you only need server-to-client updates; use WebSockets when you need two-way communication.