[BriceFab]

Problem and proposal

Closes #14376.

Expose opt-in native capabilities for plugins supporting classic combat and clients that do not use an off-hand. Existing public events can control damage and gameplay policy, but cannot select native projectile intersection/flight order, all player knockback/movement paths, or off-hand eligibility across native selectors. Post-event corrections can therefore use lost collision state or leave predictive inventory disagreement.

This is an extension proposal, not a claim that modern vanilla combat is defective. Native defaults remain unchanged. The implementation targets maintained ver/26.2, upstream base 58e6e45d67c998909581f9079189ef51eb6f1267; it has not been ported or validated against main/26.3.

Implementation and boundaries

• Player runtime combat profile for classic component clipping/jumps, accepted knockback, ordinary fall/fire behavior and explosion calculations/attribution. Modern spear, mace-smash and shield-block impulses retain native paths.
• Arrow, throwable and fishing-hook flight order, intersections and owner grace, plus initial projectile position. Initial velocity, balancing and enabled projectile types remain the caller's responsibility.
• Runtime off-hand equipment eligibility, native inventory routing/placement/merge eligibility and indirect held-item selectors. The setting is copied on respawn; residual storage is retained. Plugins must still handle swap, creative, interact and resurrection policy using public events.
• Native event cancellation, damage acceptance, protection and ownership remain authoritative. No custom identities, server balance/configuration, protocol spoofing, client trust or anti-cheat exemption is added. Integrators must coordinate matching client and anti-cheat prediction themselves.

The branch contains a single generic commit on public upstream ancestry. The feature patch changes are regenerated context/index updates needed by the source patches, not additional optimizations. The broad capability surface is proposed for maintainer review; it can be split or narrowed based on accepted API scope.

Executed validation

On this source tree before its commit (no code changes since):

./gradlew applyPatches
BUILD SUCCESSFUL in 1m 7s
./gradlew fixupSourcePatches rebuildPatches
BUILD SUCCESSFUL in 7s
./gradlew :paper-api:check :paper-server:check createPaperclipJar
BUILD SUCCESSFUL in 2m 21s

API XML: 519 executions, no failures/errors, 2 skips. Server XML: 9330 executions, no failures/errors, 22 skips. Suites may execute cases more than once; these are not unique test counts. Native default controls cover the unselected profile, modern weapons and ordinary equipment routes. Regressions cover launch/flight, collision boundaries, Punch, embedded-arrow release, fishing pulls, player impulses and off-hand routing/selectors.

Paperclip SHA-256: c64fba9a36662d9782a79c19f6f6dade1132756d41eeb97e33b5c6990d1aeffa. No connected-client runtime campaign is attributed to this upstream export.

[mbax]

Closing this as it violates agents.md, with the human not reviewing the change or writing communication themselves.