1. Yes. Each runtime is a GenServer (= own process + mailbox). There's also a lighter-weight Context mode where many JS contexts share one OS thread via a ContextPool, but each context still maps 1:1 to a BEAM process.

2. No. JS runs on a dedicated OS thread, outside the BEAM scheduler. But there's an interrupt handler (JS_SetInterruptHandler) that checks a deadline on every JS opcode boundary — pass timeout: 1000 to eval and it interrupts after 1s, runtime stays usable. For contexts there's also max_reductions — QuickJS-NG counts JS operations and interrupts when the budget runs out, closest analog to BEAM reductions.

3. QuickJS-NG uses refcounting with cycle detection. Each runtime/context has its own GC — one collecting doesn't touch another. When a Runtime GenServer terminates, JS_FreeContext + JS_FreeRuntime release everything.

4. No, standard JS mutability. But the JS↔Erlang boundary copies values — no shared mutable state across that boundary.

5. QuickJS-NG enforces JS_SetMemoryLimit per-runtime (default 256 MB) and JS_SetContextMemoryLimit per-context. Exceeding the limit raises a JS exception, not a segfault. It propagates as {:error, ...} to the caller. Since each runtime is a supervised GenServer, the supervisor restarts it. There are tests for OOM in one context not crashing the pool, and one runtime crashing not affecting siblings.

All of these replies are AI slop.