Note that you don't need to use Deno or JavaScript at all to use this product. Here's their Python client SDK: https://pypi.org/project/deno-sandbox/
from deno_sandbox import DenoDeploy
sdk = DenoDeploy()
with sdk.sandbox.create() as sb:
# Run a shell command
process = sb.spawn("echo", args=["Hello from the sandbox!"])
process.wait()
# Write and read files
sb.fs.write_text_file("/tmp/example.txt", "Hello, World!")
content = sb.fs.read_text_file("/tmp/example.txt")
print(content)
Looks like the API protocol itself uses websockets: https://tools.simonwillison.net/zip-wheel-explorer?package=d...