v8-jit

SKILL.md

V8 JIT Optimization

Use this skill when writing or optimizing performance-critical code paths in
Next.js server internals — especially per-request hot paths like rendering,
streaming, routing, and caching.

Background: V8's Tiered Compilation

V8 compiles JavaScript through multiple tiers:

Ignition (interpreter) — executes bytecode immediately.

Sparkplug — fast baseline compiler (no optimization).

Maglev — mid-tier optimizing compiler.

Turbofan — full optimizing compiler (speculative, type-feedback-driven).

Code starts in Ignition and is promoted to higher tiers based on execution
frequency and collected type feedback. Turbofan produces the fastest machine
code but bails out (deopts) when assumptions are violated at runtime.