If anyone is curious, more details on our SDK can be found here actually https://github.com/cloudflare/sandbox-sdk
Cloudflare Sandbox SDK
11–20 of 95 posts
Re: Cloudflare Sandbox SDK
#12These CF website relaunches are just that right? Workers last week (https://workers.cloudflare.com) and now this one yesterday. I mean, if CF has something newsworthy here they should do a blog post announcing it because otherwise it's just a refreshed website. It's hard to tell if there's anything new here.
It's the same SDK stuff from earlier this year right? https://developers.cloudflare.com/changelog/2025-06-24-annou...
Re: Cloudflare Sandbox SDK
#13Looks nice. We rolled out our own that does pretty much the same thing but perhaps more because our solution can also mount persistent storage that can be carried between multiple runners. It does take 1-5 seconds to boot the environment (firecracker vms). If this sandbox is faster I will instruct the team to consider for fast starup. This is also very similar to Vercel's sandbox thing. The same technology? What I do…
> It does take 1-5 seconds to boot the environment (firecracker vms).
I'd say 1-5 secs is fast. Curious to know what use cases require faster boot up, and today suffer from this latency?
Re: Cloudflare Sandbox SDK
#14Looks like there's one feature missing from this that I care about: I'd like more finely grained control over what outbound internet connections code running on the box can make.
As far as I can tell it's all or nothing right now:
this.ctx.container.start({
enableInternet: false,
});
As such, I'd like to be able to allow-list just specific network points. Maybe I'm OK with the container talking to an API I provide but not to the world at wide. Or perhaps I'm OK with it fetching data from npm and PyPI but I don't want it to be able to access anything else (a common pattern these days, e.g. Claude's Code Interpreter does this.)
Re: Cloudflare Sandbox SDK
#15Looks like there's one feature missing from this that I care about: I'd like more finely grained control over what outbound internet connections code running on the box can make. As far as I can tell it's all or nothing right now: this.ctx.container.start({ enableInternet: false, }); I want to run untrusted code (from users or LLMs) in these containers, and I'd like to avoid someone malicious using my container to la…
This simple feature bumps up the complexity of such a firewall by several orders of magnitude, which is why no similar runtime (like Deno) offers it.
Networking as a whole can easily be controlled by the OS or any intermediate layer. For controlling access to specific sites you need to either filter it at the DNS level, which can be trivially bypassed, or bake something into the application binary itself. But if you are enabling untrusted code and giving that code access to a TCP channel then it is effectively impossible to restrict what it can or cannot access.
Re: Cloudflare Sandbox SDK
#16Looks like there's one feature missing from this that I care about: I'd like more finely grained control over what outbound internet connections code running on the box can make. As far as I can tell it's all or nothing right now: this.ctx.container.start({ enableInternet: false, }); I want to run untrusted code (from users or LLMs) in these containers, and I'd like to avoid someone malicious using my container to la…
I’m extending Packj sandbox for agentic code execution [1]. You can specify allowlist for network/fs.
1. https://github.com/ossillate-inc/packj/blob/main/packj/sandb...
Re: Cloudflare Sandbox SDK
#17Looks like there's one feature missing from this that I care about: I'd like more finely grained control over what outbound internet connections code running on the box can make. As far as I can tell it's all or nothing right now: this.ctx.container.start({ enableInternet: false, }); I want to run untrusted code (from users or LLMs) in these containers, and I'd like to avoid someone malicious using my container to la…
This simple feature bumps up the complexity of such a firewall by several orders of magnitude, which is why no similar runtime (like Deno) offers it. Networking as a whole can easily be controlled by the OS or any intermediate layer. For controlling access to specific sites you need to either filter it at the DNS level, which can be trivially bypassed, or bake something into the application binary itself. But if you…
At least on macOS, there is a third way where you can control the network connection on the PID/binary level by setting up a network system extension and then setting up a content filter so you can allow/deny requests. It is pretty trivial to set this up, but the real challenge is usually in how you want to express your rules.
Little Snitch does this pretty well: https://www.obdev.at/products/littlesnitch/index.html
Re: Cloudflare Sandbox SDK
#18These CF website relaunches are just that right? Workers last week ( https://workers.cloudflare.com ) and now this one yesterday. I mean, if CF has something newsworthy here they should do a blog post announcing it because otherwise it's just a refreshed website. It's hard to tell if there's anything new here. It's the same SDK stuff from earlier this year right? https://developers.cloudflare.com/changelog/2025-06-24…
it barely had any features then, this version is full of new functionality: streaming logs, long running processes, code interpreter and lots of other things and full docs site as well
Re: Cloudflare Sandbox SDK
#19Looks nice. We rolled out our own that does pretty much the same thing but perhaps more because our solution can also mount persistent storage that can be carried between multiple runners. It does take 1-5 seconds to boot the environment (firecracker vms). If this sandbox is faster I will instruct the team to consider for fast starup. This is also very similar to Vercel's sandbox thing. The same technology? What I do…
> It does take 1-5 seconds to boot the environment (firecracker vms). I'd say 1-5 secs is fast. Curious to know what use cases require faster boot up, and today suffer from this latency?
When your agent performs 20 tasks saving seconds here and there becomes a very big deal. I cannot even begin to describe how much time we've spent on optimising code paths to make the overall execution fast.
Last week I was on a call with a customer. They where running OpenAI side-by-side with our solution. I was pleased that we managed to fulfil the request under a minute while OpenAI took 4.5 minutes.
The LLM is not the biggest contributor to latency in my opinion.
Re: Cloudflare Sandbox SDK
#20Earlier quoted context omitted.
> It does take 1-5 seconds to boot the environment (firecracker vms). I'd say 1-5 secs is fast. Curious to know what use cases require faster boot up, and today suffer from this latency?
When your agent performs 20 tasks saving seconds here and there becomes a very big deal. I cannot even begin to describe how much time we've spent on optimising code paths to make the overall execution fast. Last week I was on a call with a customer. They where running OpenAI side-by-side with our solution. I was pleased that we managed to fulfil the request under a minute while OpenAI took 4.5 minutes. The LLM is no…
Thanks! While I agree with you on "saving seconds" and overall latency argument, according to my understanding, most agentic use cases are asynchronous and VM boot up time may just be a tiny fraction of overall task execution time (e.g., deep research and similar long running tasks in the background).