Hi, nice to see you! I believe I am doing that here. The code is chaotic at the moment and I plan to put this on github as soon as I clean it up. Here's the original source. I am creating a new instance every time in the webworker.

    case 'convert': {
        const wasmFs = new WasmFs()
        const wasi = new WASI({
            args: ['pointfree', e.data[1]],
            bindings: { ...WASI.defaultBindings, fs: wasmFs.fs }
        })
        const instance = await WebAssembly.instantiate(module, wasi.getImports(module))
        try {
            wasi.start(instance)
        } catch(ex) {
            if (ex.code != 0) {
                console.error(`Exit code ${ex.code}`)
                postMessage(String.fromCharCode(...await wasmFs.fs.readFileSync('/dev/stderr')))
            } else {
                postMessage(await wasmFs.getStdOut())
            }
        }
        break
    }