# Grep sweep — deleted collision machinery (2026-08-02, against the WIP O1-O3 tree)

Produced by an adversarial-review subagent (completed after the review
round was halted). Verdict summary: the deletions are CLEAN — no
surviving consumer of the journal/peer-rebase/draft-retirement/staging-
clone machinery, and no post-`Revoke()` dereference path found. Two
actionable leftovers and a stale-docs catalog for whoever lands the
collision work.

## Actionable

1. `CollisionWorldStateSlot.TransferTo` (`CollisionWorldState.cs:270-281`)
   is fully DEAD — zero callers incl. tests. Delete it (comments at
   `PhysicsEngine.cs:311/:379` reference it historically and are
   accurate).
2. Two test names are stale terminology with live bodies:
   `RuntimePhysicsStateTests.cs:1730`
   (`PostCommitOwnerMutationWinsOverQueuedPeerRebase`) and `:2264`
   (`PendingOrActivePeerRebaseCannotResurrectRetiredLandblock`) — rename
   when touched.

## Confirmed DEAD (zero refs in src/tests/tools/docs)

- `LandblockRetirementCursor`/`Step`/`CreateLandblockRetirementCursor`
- `CollisionStagingBuilder.Advance/.WorkUnits/.Completed/.SuppressLandblock`
- `CopyOneOutsideTarget`
- Owner journal: `_collisionOwnerJournal`, `EnqueueCommittedRebase`,
  write-through, draft retirement

## Confirmed LIVE (name overlap, different concept — do not "clean up")

- `InstallLandblockClone` (`PhysicsEngine.cs:576,673`) — the per-landblock
  delta-apply installer, not the old clone loop.
- `MirrorOwnerFrom` (`ShadowObjectRegistry.cs:1961,2011,2079`) —
  repurposed for the O3 commit-time reflood.
- `OwnerMutated`/`OwnerPrefixMembershipChanged` events — general-purpose,
  unrelated to the deleted journal.
- `RetryDeferred` (`RuntimeSetPositionState.cs:4103` et al.) — the
  deferred-SetPosition subsystem, unrelated.
- `LandblockReplacementBuilder` `.WorkUnits/.Advance/.Completed` — the
  live seal builder, not the deleted staging builder.

## Post-Revoke audit

`Revoke()` has exactly one call site (`PhysicsEngine.cs:381`, end of
`CommitLandblockReplacement`). `MarkCommitted` (`RuntimePhysicsState.cs:
372-380`) + `LandblockPhysicsPublisher.cs:505/:1177-1183` guards mean no
production or test site dereferences a revoked slot. `prepared.Engine`/
`DataCache` remain unguarded by design (ObjectDisposedException is the
intended revoked behavior).

## Stale docs/comments that now describe the DELETED design (rewrite when
landing the collision work)

- `docs/architecture/acdream-architecture.md:504-566` — full section on
  journal/write-through/rebase/root-transfer: STALE, needs rewrite to
  the per-landblock delta commit.
- `memory/project_collision_port.md:50-88` — same content class, STALE.
- `docs/research/2026-07-31-atomic-collision-generation.md` — whole file
  documents the deleted mechanism with no supersession note (the
  prepared banner is in docs-drafts.md).
- `src/AcDream.Core/Physics/PhysicsDataCache.cs:126-130` XML doc —
  describes the deleted one-leaf-per-step materialization.
- `src/AcDream.App/Streaming/LandblockPhysicsPublisher.cs:621-625`
  comment — "zero-work root transfer" no longer true.
- Correctly archival (no action): `retail-divergence-register.md:113`
  (~~AD-6~~ retired entry); the placement-cutover plan + C3c closeout
  (they name the clone as the known problem being fixed).