The WebAssembly sandbox is a local sandbox for simple Python evaluators — pure-logic checks like regex matches, JSON parsing, and scoring functions. It runs locally inside the Phoenix server, starts in milliseconds, and needs no credentials.
What it supports
The WebAssembly sandbox runs your Python in an isolated WebAssembly runtime on the Phoenix server. It is intentionally limited to self-contained code:
| Capability | Supported? |
|---|
| Environment variables | ❌ Not supported — use a hosted sandbox |
| Network access | ❌ Not supported — use a hosted sandbox |
| Third-party dependencies | ❌ Not supported — use a hosted sandbox |
Running untrusted code
WebAssembly runs the Python interpreter inside a strictly isolated environment — memory is partitioned and the script has no built-in access to the filesystem, network, or operating system. The sandbox still runs in the Phoenix server process, so the script shares CPU and memory with Phoenix. For the full security model, see WebAssembly’s Security documentation.
