# Slice J5.6 — projectile-simulation ownership

Date: 2026-07-26
Scope: ownership relocation only; no retail algorithm, packet, collision
policy, impact authority, or presentation change

## Objective

Move the mutable projectile component, projectile workset, prediction version,
authoritative correction, and retail projectile step into the same
`AcDream.Runtime` physics lifetime that already owns the canonical entity
record, body, object clock, collision engine, shadows, and full cell.

App remains responsible for:

- resolving the projectile's immutable Setup/DAT collision sphere;
- supplying the current graphical projection validity acknowledgement;
- rebucketing and positioning the retained render projection after a Runtime
  commit;
- synchronizing the render shadow and effect pose;
- drawing meshes, trails, particles, sounds, and impact effects.

ACE remains authoritative for targets, hits, damage, impact scripts, and
deletion.

## Named-retail oracle

Primary source:
`docs/research/named-retail/acclient_2013_pseudo_c.txt`.

- `CPhysicsObj::UpdateObjectInternal` `0x005156B0`
- `CPhysicsObj::update_object` `0x00515D10`
- `CPhysicsObj::SetPositionInternal(CTransition const*)` `0x00515330`
- `CPhysicsObj::set_velocity` `0x005113F0`
- `OBJECTINFO::missile_ignore` `0x0050CEB0`
- `Frame::set_vector_heading` `0x00535DB0`

The complete translated retail projectile control flow is pinned in
`docs/research/2026-07-13-retail-projectile-vfx-pseudocode.md`. The existing
Core `ProjectilePhysicsStepper` and collision driver were cross-checked there
against ACE's physics implementation and Holtburger/ACViewer's DAT
interpretation. J5.6 reuses those algorithms unchanged.

## Preserved control flow

```text
for each spatial projectile owned by the current incarnation:
    reject static, frozen, parented, hidden, cell-less, or inactive bodies
    advance the retained CPhysicsObj clock in retail 0.2-second quanta
    for each due quantum:
        calculate acceleration from the final PhysicsState
        clamp speed to 50 world units/second
        integrate position, velocity, omega, and AlignPath orientation
        continuously sweep the authored Setup-local collision sphere
        apply retail missile-ignore and inelastic/elastic collision rules
        commit the accepted frame and full cell to the canonical record
        stop the split prediction if any authority/incarnation token changed
    publish one immutable committed frame to the host
```

The graphical host may reject the presentation acknowledgement after a
re-entrant delete, replacement, rebucket, or session reset. That rejection
invalidates the pending prediction; it cannot roll back or redirect a newer
canonical owner.

## Previous ownership gap

Before J5.6:

- `RuntimeEntityRecord` owned identity, body, state, clocks, and cell;
- `RuntimePhysicsState` owned the engine, shadows, remotes, and ordinary/remote
  worksets;
- App `ProjectileController` still owned the projectile component, projectile
  workset snapshot, quantum stepping, correction, and canonical cell commit.

That split made a no-window Runtime unable to fly the same projectile without
reconstructing App behavior and left projectile mutation on the wrong side of
the presentation boundary.

## Implemented boundary

- `RuntimeEntityRecord.Projectile` is the sole mutable projectile component
  slot.
- `RuntimeProjectile` owns the canonical body, authored collision sphere, and
  prediction-authority version.
- `RuntimePhysicsState` owns binding, refresh, spatial membership, authoritative
  vector/state correction, and the exact-key projectile workset.
- `RuntimeProjectilePhysicsUpdater` owns the unchanged retail quantum,
  integration, sweep, collision, cell-crossing, and split-prediction logic.
- Runtime cell commits flow through the same typed
  `RuntimePhysicsCellCommit` used by ordinary and remote objects.
- App `ProjectileController` resolves DAT/Setup shape data, delegates the
  simulation, and applies only retained render projection, shadow, and effect
  pose acknowledgements.
- Delete, GUID reuse, visibility withdrawal, pending-to-loaded recovery,
  authoritative correction, and session teardown use the canonical Runtime
  record and workset; they never reconstruct from stale spawn data.

No gameplay outcome moved client-side. No projectile-specific render pass,
second GUID map, body mirror, effect owner, or collision owner was introduced.

## Automated acceptance

On production commit
`2aee33569f0268d7bc0f4f52437dfa0b405432a4`:

- Runtime tests: 317 passed.
- App tests: 3,718 passed / 3 skipped.
- Focused Core projectile tests: 47 passed.
- Complete Release solution: 8,591 passed / 5 skipped.
- Release solution build: zero warnings and zero errors.

The focused fixtures cover:

- canonical component/body/workset identity;
- 0.2-second catch-up quanta and prediction invalidation;
- clamp, gravity, omega, full 3-D AlignPath, and collision;
- thin walls and inelastic stopping;
- missile/ethereal/designated-target exclusion;
- loaded, pending, landblock crossing, and hydration;
- State/Vector/Position correction order;
- deletion, same-GUID reuse, reset, and 96-owner lifetime stress;
- no duplicate mesh, body, shadow, script, effect, or projectile owner.

## Connected acceptance

All connected processes used the exact embedded/source commit
`2aee33569f0268d7bc0f4f52437dfa0b405432a4` and closed gracefully.

- Arrow plus representative spell projectile:
  `.test-out/j56-projectile-20260726-143256`
  recorded an authoritative missile attack, live Arrow spawn, live Acid Stream
  spawn, and matching authoritative deletes.
- Crossbow bolt:
  `.test-out/j56-crossbow-evidence-20260726-145612`
  recorded a missile attack, live Quarrel spawn with Setup `0x0200012A`,
  authoritative ammo pickup/update, projectile delete, and target death.
- Lifecycle/reconnect:
  `logs/connected-world-gate-20260726-145731/report.json`
  passed capped login plus fresh uncapped reconnect, all seven checkpoints,
  zero failures, and two code-zero exits.
- Canonical nine-stop route:
  `logs/connected-r6-soak-20260726-151349.report.json`
  materialized all nine destinations, passed the Caul/Holtburg/Caul-return
  forward, jump, combat, and movement-truth exercises, matched source and
  binary, and exited with code zero and zero failures.

The first route attempt,
`logs/connected-r6-soak-20260726-150347.report.json`, intentionally remains in
the evidence trail. Its strict plateau check saw the already-known late lazy
mesh population (`582 -> 604`) while sampled entity counts happened to match
and therefore reported one failure. The immediate warm-machine rerun saw the
same class of late population (`581 -> 598`) together with one changed visible
owner and correctly classified it as workload variation. The accepted J5.5
baseline exhibited the same late Caul behavior (`575 -> 597`), and the J5.6
diff contains no mesh-cache, mesh-preparation, streaming, or residency change.
This is not waived as a projectile result and no threshold was loosened.

## Divergence and rollback

J5.6 changes ownership only. The retail algorithm, constants, packet order,
server authority, and presentation are unchanged, so it introduces no new
retail-divergence row.

Exact rollback:

```text
git revert 2aee33569f0268d7bc0f4f52437dfa0b405432a4
```