Description of the new feature / enhancement
Currently, Microsoft Execution Containers (MXC) provides policy-driven containment through native OS primitives (ProcessContainer on Windows, Bubblewrap on Linux, Seatbelt on macOS) and virtualization (MicroVM/Hyperlight).
While OS-native and VM backends excel at isolating traditional process executions, they can introduce startup overhead when handling high-frequency, short-lived AI agent tool calls or require OS-specific kernel capabilities. Additionally, WebAssembly (specifically WASIX) is rapidly becoming a standard runtime target for sandboxing untrusted dynamic code generation and plugin execution across heterogeneous environments.
Proposed technical implementation details
Introduce a wasix (or wasm) backend option within MXC (wxc-exec / TypeScript SDK @microsoft/mxc-sdk).
The WASIX backend would leverage a WebAssembly runtime (such as Wasmer or Wasmtime extended with WASIX support) to execute WebAssembly binaries or WASI/WASIX-compiled runtimes (like Python WASM) under MXC policy constraints.
Key Aspects:
- Schema Extension: Extend the JSON policy schema to support
wasix as a backend target:
{
"script": "app.wasm",
"backend": "wasix",
"wasix": {
"runtime": "wasmer",
"entrypoint": "_start"
},
"filesystem": {
"readwritePaths": ["/tmp/workspace"],
"readonlyPaths": ["/usr/lib"]
},
"network": {
"defaultPolicy": "block",
"allowedHosts": ["api.github.com"]
}
}
Description of the new feature / enhancement
Currently, Microsoft Execution Containers (MXC) provides policy-driven containment through native OS primitives (
ProcessContaineron Windows,Bubblewrapon Linux,Seatbelton macOS) and virtualization (MicroVM/Hyperlight).While OS-native and VM backends excel at isolating traditional process executions, they can introduce startup overhead when handling high-frequency, short-lived AI agent tool calls or require OS-specific kernel capabilities. Additionally, WebAssembly (specifically WASIX) is rapidly becoming a standard runtime target for sandboxing untrusted dynamic code generation and plugin execution across heterogeneous environments.
Proposed technical implementation details
Introduce a
wasix(orwasm) backend option within MXC (wxc-exec/ TypeScript SDK@microsoft/mxc-sdk).The WASIX backend would leverage a WebAssembly runtime (such as Wasmer or Wasmtime extended with WASIX support) to execute WebAssembly binaries or WASI/WASIX-compiled runtimes (like Python WASM) under MXC policy constraints.
Key Aspects:
wasixas a backend target:{ "script": "app.wasm", "backend": "wasix", "wasix": { "runtime": "wasmer", "entrypoint": "_start" }, "filesystem": { "readwritePaths": ["/tmp/workspace"], "readonlyPaths": ["/usr/lib"] }, "network": { "defaultPolicy": "block", "allowedHosts": ["api.github.com"] } }