TL;DR

• WordPress 7.1 added a wp_pre_execute_ability filter that lets any plugin fully short-circuit Abilities API calls (including permission checks).
• Media Library infinite scrolling is back on by default (reversed since 5.8).
• Speculative loading still defaults to conservative; new constants let hosts override it instead of the planned auto-detection.
• Core grew 25% almost entirely from lazy-loaded admin JS (vips + video workers) with no measurable front-end impact.
• Not a security release - just inherits the 7.0.x fixes.

also - it's the first release that included my fix so now I'm officially Core Contributor :)