How this platform works

As you write code, TCC (Tiny C Compiler) runs in your browser via WASM to provide instant typechecking without server roundtrips.

When you you click Run your code is saved in local storage and sent to the backend.

The backend will compile your code to a BPF object using clang and spin up a fresh VM to execute it..

The VM

Each submission gets an ephemeral VM with:

• 0.5vCPU, 64MB RAM
• Kernel 6.18.2 (latest LTS)
• No network
• A 500ms self-destruct timer

Boot time is 40~50ms thanks to Firecracker (with some unholy patches), and a very minimal kernel.

The VM boots into a custom /init process, that does the bare minimum setup (mount /sys, set up a loopback interface, …), loads your BPF object and starts streaming events.

Getting events out of the vm

Your code must #include ep_platform.h, which creates a BPF ringbuf map for all output.

The DEBUG_ and SUBMIT_ macros write events to this map.

Inside the VM, the init process polls this ringbuf and forwards events to the host via vsock. The backend streams these events via SSE your browser.