WASM support

[kitknox]

This is to document and get feedback on WASM support in rootshell. I've landed initial support that allows you to cross compile elsewhere to WASI, copy the resulting binary to the rootshell iOS local shell and then run it. Support exists for sandboxed filesystem read/write access, TCP sockets, DNS, and TLS/HTTPS network requests. Sessions can run cooked or raw. This is going to need to be strictly framed using the Educational use exception for App Store purposes. Bundling of package managers for pre-compiled WASM binaries may be a step too far. I plan on working to get a minimal version approved before spending too much time on something that might just be rejected. (Even though other apps like a-Shell already leverage WASM in a terminal type environment.)

I did a demo port of outside which is a rust TUI weather application. It was fairly small to do as an initial port and exercises filesystem and network access in a raw mode session. This repo is also GPL which we otherwise cannot directly bundle in the binary on the App Store as well.

I will get a repo up that documents the compilation steps, and how the network primitives work. I have demos working so far in both rust and go. Note that the "system calls" for network access have to go through an expensive bridge. This port is smaller than a hello world in go which comes out above 2MB and is noticeably slower to launch.

-rwxr-xr-x  1 kit  staff   1.3M May 11 16:47 outside.wasm*

Link to WASM port is here.

[travelingflwr]

Looking this over now. This would make my feature request unnecessary.

[kitknox]

I updated the example outside fork to dynamically handle window resizes. Here is a compiled WASM file for anyone that wants to quickly see this in action.

outside.wasm.zip

[travelingflwr]

I’m thinking about building a Pi Code Agent-inspired minimal agent harness as a learning/toy project to share with the community. A few questions to figure out the right approach:

1. JS bridge — does the Wasm runtime expose any JavaScript surface, or is it pure WASI?

2. Shell passthrough — are there host functions available to call back into Rootshell’s native shell from within a Wasm module? (thinking run_command style)

3. Network — can Wasm modules make outbound HTTP calls directly, or does that also need to go through a host function? (planning to target Ollama as the LLM backend)Basically trying to figure out if the architecture is Rust→Wasm with embedded QuickJS for scripting, or if there’s already a JS layer I can lean on.

Amy

[kitknox]

@travelingflwr The current implementation is wrapped around WKWebView and leverages the WASM runtime provided by Apple. This gives us low overhead and JIT access from what I understand, but also at the whim of Apple in terms of what it supports. While I may bundle other options in the future this seemed like a reasonable place to start. This all does go through a Javascript bridge, but with a static implementation currently that is shipped with the rest of the app bundle. In theory I could offer integration points to inject whatever you want there to interface back to WASI with.

There is currently no shell pass through. It is technically possible and I’ve already been thinking about this for other reasons.

On the network side you have access to raw TCP and UDP sockets. I also implemented a TLS API so that you don’t always have to bring your own full stack and all of that overhead. While this will work well for many use cases, if you need client certifications or customization around the cert validation this is currently not a good fit. For your use case it sounds like the TLS API would work well. Just bring your own HTTP.

From my initial testing Rust is a better fit in this environment than go if you are starting something new so your plan there makes sense. I would expect any penalty for bridging from WASI to Javascript and then getting the native JS execution speed to be far better than anything you embed inside Rust. I think I can just extend an API over WASI for you to inject whatever you want?

[kitknox]

The main repo now has WASM documentation and examples in both rust and go.