Confession: i've lost count of how many times an agent has killed my running dev server and started a new one on a different port. it's the single most annoying thing about coding with AI right now.

Turns out Next.js 16.2 just fixed it so dig into the snack below.

let's dig in 🍿

PRESENTED BY SUPABASE

Supabase is the backend for your app: it gives you a database plus the “boring but necessary” stuff around it (user sign-in, file storage, background functions, and real-time updates) in one place.

It’s built on Postgres (a widely used database), so your data is portable and you’re not locked into a proprietary system.

For founders and PMs building with AI, it’s the fastest way to go from prototype to a real, working app, all without stitching together five different services or learning a bunch of infrastructure first.

Next.js 16.2 stops this with one quick change.
​
​💡 Why it happens​
Your AI doesn't know the server is already running. So it tries to start a new one and kills the existing process
​
​🧠 The Fix​
​→ Next.js 16.2 creates a .next/dev/lock file automatically
​→ It locks the port
​→ Your agent sees the lock and leaves the server alone
​
No more duplicate processes.
No more killed dev servers.
Aka NEVER EVER try to start a new dev server when one is already running.

🚀 The Takeaway

One tiny lock file solves one of the most annoying AI agent behaviours when working with Next.js.

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🎁 If you're interested, you can download this free cheatsheet covering 29 common mistakes just like this one in React and Next.js.

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​ SECURITY VULNERABILITIES

​Next.js just got it's worst vulnerabiities, make sure to upgrade if you haven't already.

​🔥 Love it!​

​😐 It’s okay​

​👎 Not good​

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