• Node-API — the standard napi_* C ABI for native addons: building against the prefab package, registering and requiring addons, threading and finalizer contracts, and the documented divergences from Node (shared with the iOS runtime).
• Performance API — WHATWG performance (hr-time, user timing, performance timeline with PerformanceObserver), per-isolate time origins for workers, the native clock hook that future requestAnimationFrame work must share, and the documented spec deviations.
• AbortController / AbortSignal — the DOM abort primitives (AbortController, AbortSignal with the abort/timeout/any statics) layered on the runtime's EventTarget, the GC contract (weak timers and any() links, listener-driven persistence), and the DOMException reasons.
• TextEncoder / TextDecoder and atob / btoa — the WHATWG encoding and base64 globals (TextEncoder, TextDecoder, atob, btoa), the supported encodings with their label sets, streaming decode semantics, and the lazy-global tier that runs their builtins only on first use.
• Error handling — global error/unhandledrejection events, reportError, catching Java exceptions in JS (error.nativeException), forwarding JS throws to Java callers (interop.escapeException), JS stacks on Java exceptions (com.tns.JavaScriptStackTrace), configuration flags, and crash-reporter integration.
• structuredClone — the WHATWG structuredClone(value, { transfer }) global: what clones, how graph identity and cycles are preserved, ArrayBuffer transfer, and the DataCloneError DOMException on failure.
• Implementing additional Chrome DevTools protocol Domains

Notes on work that is done, kept because the reasoning is expensive to reconstruct rather than because anything needs doing.

• V8 10.3 → 14.9 migration — the API changes and their site counts, why each non-default gn arg exists, the accessor rules that are not mechanical, and the traps that only show up at runtime.