Scoped together because both concern item/container placement; they turn out to
share no production file, but the shared inventory premise had to be corrected
once rather than twice.
The governing correction: both routes' inventory sections rest on
"RegisterEntityWithInitialResidence is never called from any production path."
C3c (529e0e9d) made that false — LiveEntityRuntime.cs:544-548 and
RuntimeLiveEntitySessionController.cs:118-123. Every conclusion reasoning from
"nothing upstream to cancel" is obsolete.
Route 6 (drops) is COMPLETE. No route-6 disposition exists: a dropped item is
Remote + TopLevel -> SetPosition/Placement|Slide, which is route 1's
classification exactly, and both drop flavors already converge on
LiveEntityHydrationController.OnCreate (split-recovery at
InventoryWorldDropProjectionController.cs:66). BuildSpawn overrides every
positional field, so the stale-source-position requirement is met.
Route 6 also retires a false premise in this campaign's own plan
(2026-08-02-placement-cutover.md:98-100): "replay create-time effects" is NOT
established as a defect. acdream's only create-time replay is the F754/F755
queue keyed by GUID, which is retail's own HandleCreateObject @0x00454C80
behaviour. The one plausible mechanism — a cloned DefaultScriptType — never
fires at create in either client; retail's play_default_script is reached only
from DoCollision @0x0058C3A0 and the hook dispatcher @0x00526C08/@0x00526C14.
And retail's "split-recovery marking" is a SELECTION transfer, not effect
suppression: UIAttemptSplitTo3D @0x0058D850 records WCID/stack/time and
DeclareValid @0x0058E340 re-selects at @0x0058E481. That port is missing but is
selection UX, not placement — file it outside C4.
Route 7 is one slice, ~300-490 lines, and must not be split: the Runtime commit
and the App demotion are two halves of one transfer. Retail performs NO
placement here — DoPickupEvent @0x00452240 is unset_parent + leave_world;
DoParentEvent @0x00452290 is set_parent + SetPlacementFrame. No SetPosition, no
leash. So route 7 inverts 4b-2's rule: never arm ConstrainTo.
Route 7's real defect: the child's canonical cell has two writers. Retail
re-cells inside set_parent (change_cell @0x00515AD6 + recalc_cross_cells
@0x00515B15); acdream commits the child cell-less in Runtime and re-cells it
from a RENDER TICK (EquippedChildRenderController.TickChild:408 ->
RebucketLiveEntity). Headless has no such controller, so every headless
parented child stays cell-less forever — the headless gap and the two-writer
split are the same bug.
Load-bearing unestablished item, recorded rather than guessed: whether retail
re-cells children when the parent crosses a cell. UpdateChild @0x00512D50 ->
set_frame @0x00514090 is frame-only and never writes objcell_id;
change_cell/set_cell's child handling was not read. Settle that before
demoting App's rebucket — demoting it blind risks route 4a's R1 / #184
invisible-but-solid.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
