@microsandbox

⚡ easy, fast, and programmable microVM. ship with your app, self-host, BYOC, or run on our cloud. ideal for AI agents, dev containers, CI/CD, and more · YC F26

 toronto
docs.microsandbox.dev
Joined April 2025
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you can now return custom HTTP denial messages to your agent or harness when a network or secret policy blocks a request in a microsandbox. 🛡️ tell it what to do next, or disable responses to close the connection without an explanation.
typescript example configuring custom HTTP denial messages in microsandbox for blocked network access and secret use. below, a 403 forbidden json response contains the code “secret_policy_denied,” the message “review secret access.” and the domain “example.com.”

ALT typescript example configuring custom HTTP denial messages in microsandbox for blocked network access and secret use. below, a 403 forbidden json response contains the code “secret_policy_denied,” the message “review secret access.” and the domain “example.com.”

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see docs to learn more: docs.microsandbox.dev/networ…

Overview - microsandbox

Control network access and isolation

docs.microsandbox.dev
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microsandbox retweeted
Dave Kiss
@davekissOct 15
🏖️ How to run your own local sandboxes (give this to your agent): A spare Linux box can run your coding agent's sandboxes with each one getting its own microVM and private env vars Mine's running on a Framework, completely replaced Vercel Sandbox for my demos - @microsandbox runs each sandbox as a VM with its own kernel instead of a container - the VM gets a placeholder key; the proxy swaps in the real one only on calls to that host and keys expire with the sandbox - a firewall keeps it off the host's own services, my home network and tailnet; only the public internet - each one gets 2 CPUs and 4 GB, up to 10 run at once and stops after idle for 30 minutes prompt in reply one line install: curl -fsSL install.microsandbox.dev | sh
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any API key your agent can read is one prompt injection away from leaking. in microsandbox, the key never enters the guest. instead the agent gets a placeholder, and the real key gets swapped in on the way out. here's what that looks like ↓
microsandbox
@microsandboxOct 2
introducing msb in 90s, a new series. episode 1: pause and resume pause a running computer. resume it right where it left off.
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the --secret flag: msb create python --secret [email protected] GITHUB_TOKEN → read from your env, never stored api.github.com → the only host that gets the real key send the placeholder anywhere else and the request is blocked.
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walk through it yourself in a minute: github.com/superradcompany/m… what should we explain next?
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microsandbox v0.7.7 + v0.7.8 are out! ⚙️ run commands in the background (jobs) 🔑 choose which headers receive secrets 🌐 use HTTP CONNECT proxies 🧹 inspect and clean up local storage plus control over clock syncing when restoring snapshots, and more. 🧵
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more replies
where did the disk space go? msb df shows local storage usage. msb prune --dry-run previews unused runtime memory files you can remove, without touching saved snapshots or disks.
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12 people helped ship these releases, including 5 first-time contributors. thank you for building microsandbox with us 💜 full release notes: docs.microsandbox.dev/change… docs.microsandbox.dev/change…

v0.7.7 - microsandbox

Connect through HTTP proxies, inspect local storage, and control the clock in snapshot-based tests.

docs.microsandbox.dev
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toks
@toksdotdevOct 2
.@microsandbox now 5th on DAX bench. we've been investing a lot into performance of our runtime over the past couple months, and it shows. some of those changes got rolled out to the cloud only recently (still private beta). trailing on TTI bench, with lots of improvements in our backlog. expect to see more of those wins as we roll out more exciting features and improvements.
ComputeSDK
@computesdkOct 2
Sandbox Dax 🏁 🥇@isorun 🥈@Miosa_AI 🥉@sfcompute
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introducing msb in 90s, a new series. episode 1: pause and resume pause a running computer. resume it right where it left off.
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msb pause freezes a whole microsandbox in ~10 ms: every process, its memory, its progress. paused, a sandbox that was maxing out a core drops to >1%. msb resume brings it back in ~10-25 ms and the job carries on from the exact step it stopped at.
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walk through it yourself in a minute: github.com/superradcompany/m… that's episode 1 of msb in 90s. what should we explain next?
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microsandbox retweeted
appcypher
@theappcypherOct 2
if you want this too but don't have lovable-level time and money, @microsandbox is the open-source alternative that gives you this and more. O_DIRECT is shipped for disk and memory is next.
Jonathan Grahl
@jonathangrahlOct 2
We've patched Firecracker snapshots to support io_uring and O_DIRECT writes 🤭 Our sandboxes utilize around 2G of resident memory in the p90 case, due to deps like Vite, FFmpeg or Chromium. That's becoming less of a problem with these types of improvements! Feels good.
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you can now snapshot and branch a running computer. memory snapshots are live in microsandbox, on macos, linux and windows.
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a full snapshot captures the whole sandbox: disk, memory, every running process. snapshots take ~30ms (~40ms at 4 GiB) after the first one. branching into a new running sandbox takes ~100ms.
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so you can: - set up an environment once, reuse it already warm - branch one moment and try different approaches - snapshot before a risky change, come back anytime available now in v0.7.4 (arm64 and x86-64). cloud support coming soon. docs.microsandbox.dev/sandbo…

Snapshots - microsandbox

Save files or running workloads and restore them into new sandboxes

docs.microsandbox.dev
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