Whole fight for AI sandbox

Why AI agent need sandbox to execute code and its not cheap

Tags: Vercel, Cloudfare, Sandbox, API, AI

Hello there!!

I was working on my own AI coding agent to develop an AI website builder. Building any AI agent is not that hard unless we need to put the application in production for large-scale users, mainly 100+ users at a time, on the website. That's the time and situation when one understands the real cost of running these B2C businesses with a FREE version that has more than 100k monthly visitors; it's not as easy or cheap as it sounds.

It's actually way harder, and I'll give you reasons why things get messy in production and how the actual server costs are increasing

I'll also share a story about why sandbox development for AI agents to execute code in an isolated environment became the most underrated concept in programming in 2026. Every major tech company, including Vercel, Cloudflare, Hostinger, and AWS, will release its own code sandbox for AI agents.

I am combining 2 problems into one because they are closely linked. Problem 1: Running code in production or on an isolated server for more than 10k concurrent users is not cheap. Problem 2 is that developing a cheap isolated code execution sandbox is quite hard. Even if one is built, the next problem is making a fast sandbox that emulates Linux or macOS perfectly.

Developing an AI Website Builder

I was working on developing my own Lovable (v0) and using my own API keys to avoid paying $20+ per month.

Some argue that even after developing one for myself, the code output won't be good enough, APIs might be slow, making the app quite slow for large codebases, the quality of code and test-cases is not production-level, solid and tangible to trust

I agree with it, but the above concerns relate to code quality and context engineering, which I believe can be addressed. API latency and concurrent handling can be improved with some pooling concepts, which is why they are bottlenecks. not the main reason why most of the companies are not building a website builder on their own, and BYOK (Bring Your Own Keys)

The main reason is running isolated containers or sandboxes that run the code. The nextjs repository renders the output in the browser. This is the main problem: building sandboxes is not that easy, and we don't have many good open-source options, unlike for UI libraries.

A few sandbox options are as follows

Codesandbox

Vercel Sandbox

Cloudflare sandboxes or Workers

But each comes with its own PROS and CONS, plus its own production cost. Some charge per minute, show send bills per usage, and trust me, developing a sandbox is not easy for a solo developer.

Vercel sandboxes shut down the instance when not in use, making them quite slow for first-time users. Cloudflare workers are not cheap and are not affordable for solo indie hackers to run the sandboxes for 10k monthly active users. It's really not that cheap. Forget about the database costs of writing on disk when using supabase or Firebase.

I don't want to demotivate, but knowing the reality gives a clearer picture.

Do not jump directly to building your own SaaS to replace another SaaS application to save 20-50 USD per month; it makes no sense, IMO.

That is why I am bullish on the idea that AI will kill all SaaS. SaaS is not dead; it is changing. Those small CRUD API operations people usually pay for will be replaced easily using Vibe coding. Still, not actually, but other SaaS that solve pain points will stick and grow even more.

One good example is the Simple Screenshot API, which generates $10k/month, and I've found many indie hackers developing the same SaaS even now, in 2026.

Example, https://screenshotone.com/ and https://screenshotscout.com/

Now we will move ahead to our actual blog. Sandboxes and isolated containers are easy to integrate or develop; they need fs module access and work fast with honojs, but running them on servers in production for 10k users is not feasible and consider the fact that you have to provide free access to the thousands of users as well.

Why is my AI Website Builder not in Production?

I've built my own AI website builder similar to v0 and lovable, but I didn't put it LIVE.

A few reasons, first, let's break down the cost

1. OpenRouter API key or OpenAI API key costs around $50-100/month, depending on the traffic
2. Server sandbox costs around $100/month, dealing with 1k users per month
3. Costing for the backend API is around $50-100/month, dealing with 1k users per month

In total, $300-$500/month will be your basic minimal costing for running the app live for 1k users/month and considering only 2% to 10% conversion rate of your SaaS, one can do the MATHS and make the break-even after every 20 paid users per month, which is not that hard, but neither is it that easy.

Sometimes building is not that hard, but running it live for hundreds of users is much tougher than building, and marketing is even tougher than that.

But if you are building for B2C and can't get funding from YC or other VCs, then this MATHS is easier and cheaper to afford, making break-even after every 20 customers is quite affordable for an already funded startup or company, but if doing it alone you need to invest a decent $$$

Moving ahead, this is the main reason I've found that the main companies are building Sandboxes on their own. Vercel and Cloudflare both released sandboxes and workers, respectively, after the AI coding agents took the market space.

Every AI agent needs a sandbox to run the code and return the output, and this will keep on increasing in the future, which gives the first-come advantage to these large tech companies like Vercel and Cloudflare. Even scraping companies run the scrapers on isolated sandboxes, as it is fast and safe, and hence increases the market demand

But we have a lot of other open-source sandbox options, and sandboxes are also not bottlenecks the main pain point is running sandboxes on the server, and the costs it incur for large userbase is the actual bottleneck.

We still have only few companies working on these problems and I'ven't seen any YC based startup working on it as well in the last 2 years, maybe someone in future will bring AI agent-based isolated sandboxes that are fast and cheap to run on servers for thousands of agents and users.

Till the next time, have a good day

Shrey