# C4 route 6 — drops and split-recovery: pinned contract (2026-08-04)

Scoped in
[`2026-08-04-c4-routes-6-7-scoping.md`](2026-08-04-c4-routes-6-7-scoping.md)
§6. Pinned after route 4b-3 landed (`6dc7ba51`, gate passed `21cd6e9b`).

**Route 6 requires ZERO production lines.** It is a closure, not a slice: C3c
(`529e0e9d`) already flipped both hosts' Create paths onto the residence lease,
and a dropped item is byte-for-byte route 1's create classification. The
deliverable is evidence + coverage tests + one planning-record correction.

**If implementing this contract requires a production change, STOP AND REPORT.**
A production diff here means the scoping's central finding is wrong, and that
is a finding worth more than the slice.

## Why there is nothing to build

A dropped item is an ordinary non-local CreateObject:
`RuntimePositionEntityKind.Remote`, `RuntimeCreateResidenceKind.TopLevel`,
`ClassifyCreate` → disposition `SetPosition` with
`InitialCreateFlags = Placement | Slide`. Route 6 is a *source* of route-1
traffic, not a route of its own.

Both drop flavours already converge on the canonical transaction:

- **Whole-item drop** — `ItemInteractionController.ExecutePlacementActions`'s
  `DropToWorld` case sends the drop with no physics and no position; the
  server's CreateObject returns through
  `LiveEntityHydrationController.OnCreate` → `RegisterLiveEntity` →
  `RegisterEntityWithInitialResidence`.
- **Split-to-world** — `InventoryWorldDropProjectionController`'s
  `TryRecoverUnknownPosition` calls **the identical `_hydration.OnCreate`
  entry point**. Same residence lease, same conductor, same placement.

So the campaign handoff's route-6 requirement ("`TryRecoverUnknownPosition`
may create the logical object, but it must enter the same canonical
create-placement transaction") is already met, by C3c, with zero route-6 code.

## The false premise this closure exists to retire

`docs/plans/2026-08-02-placement-cutover.md:98-100` states route-6
split-recovery creates "need an effect-replay suppression signal". **That is
unsubstantiated and must be corrected in this landing.**

acdream's only create-time effect replay is the F754/F755 queue drain keyed by
server GUID (`EntityEffectController.ReplayPendingForLiveEntity`), written only
by inbound `PlayPhysicsScript`/`PlayPhysicsScriptType` for that exact GUID. A
fresh split GUID has nothing queued unless ACE actually sent an effect for it,
and draining it then is retail's own behaviour
(`SmartBox::HandlePlayScriptID` @0x00452020 / `HandlePlayScriptType`
@0x00452070 queue while absent; `HandleCreateObject` @0x00454C80 drains).

The one plausible mechanism — a cloned `DefaultScriptType` surviving
`BuildSpawn` — **does not fire at create in either client.** acdream's
`PlayDefault` has exactly two callers, both animation hooks
(`DefaultScriptHook`, `DefaultScriptPartHook`). Retail matches:
`CPhysicsObj::play_default_script` @0x005132B0 / @0x00513300 is reached only
from `ACCWeenieObject::DoCollision` @0x0058C3A0 (call @0x0058C3B4) and the
animation-hook dispatcher (@0x00526C08, @0x00526C14). **Neither client plays a
default script from `set_description` or CreateObject.**

**Verify both retail claims yourself before relying on them.**

## Retail truth for split-recovery marking

`ACCWeenieObject::UIAttemptSplitTo3D` @0x0058D850 records exactly three fields:
`splitStackSize` @0x0058D8A2, `splitClassID` @0x0058D8A8, `splitTime`
@0x0058D8AE. `UIAttemptSplitToContainer` @0x0058D7D0 records the identical
three. The consumer is `ACCWeenieObject::DeclareValid` @0x0058E340, whose
recovery action is `SetSelectedObject(this->id, 0)` @0x0058E481 — **a SELECTION
transfer, with a 10-second expiry @0x0058E49F-@0x0058E4B2. Not effect
suppression, and nothing placement-related.**

`ACCWeenieObject::UIAttemptPutIn3D` @0x0058D700 (whole-item drop) records no
marker at all and performs no placement.

## Deliverables

1. **Coverage tests, 150-250 lines**, against the now-flipped path — the list
   the campaign handoff names: whole item, split stack, new GUID, second drop
   position, unavailable destination, newer Position arriving while waiting.
   Note "attached child becoming a world root" from that list is **NOT route
   6's** — it is a cell-less Position on an existing entity, owned by 4b-3.
2. **R6-c settled by assertion, not by argument.** `BuildSpawn` clones
   `Children` / `Movement` / `AnimationFrame` / `SetupTableId` wholesale from
   the source. Expected inert for a stackable inventory item but never
   measured. Assert it in the tests rather than reasoning about it.
3. **The plan correction** at `docs/plans/2026-08-02-placement-cutover.md:98-100`.
   All three clauses are stale: the effect-replay premise is unsubstantiated
   (above), and route 7's `TryCommitParent`/`CommitWithdrawal`
   cancellation-symmetry and host-visible cancellation receipts were BOTH
   closed at C0. Replace with what actually remains: route 7's child-cell
   two-writer split and the headless parent-realize gap.
4. **R6-a filed as an issue, NOT implemented here.** `DeclareValid`'s
   `SetSelectedObject` is not ported and the container-split flavour has no
   marker. That is selection UX, not placement; mixing it into a placement
   closure makes the landing un-reviewable. Add to `docs/ISSUES.md`.

## What must remain true

- **Zero production lines.** No `src/**` change. See the stop condition above.
- **Tests must fail against broken behaviour.** No source-text pins, no
  tautologies. The 4b-3 lesson (round-2 finding B1): a test asserting only what
  must NOT happen cannot detect a deleted write — assert the positive half too.
- AP-124 (the WCID/count approximation in the recovery match) stays open and
  registered; retiring it needs ACE to send CreateObject to the initiator, not
  a client change.

## Gates

- Complete Release suite. **Baseline 11,013 passed / 4 skipped / 0 failed** at
  `6dc7ba51` — measure and record; do not inherit. Known flakes, do not chase
  and do not conflate: #302 (`PortalProjectionTests`, GC-allocation) and #308
  (`NakEmissionTests.LossSoak_…`, wall-clock, full-suite load only).
- **Connected gate (user-run), cheap and directly visible:** drop a whole item
  on open ground — it must land at your feet, resting, immediately pickable.
  Split a partial stack to the ground — correct quantity on the pile, remainder
  in inventory. Drop a second item within ~1 m — both remain visible and
  separately pickable. Repeat once indoors and once after a portal recall. Walk
  two landblocks away and back — both piles still there, still pickable.
  **Regressions:** item at world origin or your *previous* position (stale
  pose); invisible but blocking (#184 class); sunk into or floating above the
  floor; not pickable; the split pile never appears (recovery window failed);
  the second drop swallowed by the first.