The Execute Code, Execute Function and Execute Tool endpoints are all backed by a set of execution environments. Every time you run code, it runs inside exactly one of these environments.

Unless you’ve created a Custom Runtime, your code will run inside the default WASI environment. When you create a custom runtime, the flags on your account determine which environment the custom runtime is associated with.

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WASI

The default execution environment is WASI, which is a server-side interface for WebAssembly. This environment is extremely performant but has some limitations, notably limited support for third-party dependencies.

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microVM

When you run code in a Custom Runtime for Python or JavaScript, by default that code runs inside our microVM execution environment. This environment is more flexible than WASI but isn’t quite as fast.

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V8 (beta)

For JavaScript specifically, we are devleloping a new execution environment based on V8. This environment offers the flexibility of our microVM environment but with better performance. If you’re interested in trying it out please get in touch.