Runtime documentation

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.
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-named Error that stands in for DOMException.
Implementing additional Chrome DevTools protocol Domains

Knowledge

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.