# S6 contract (Campaign S) — contain the undecodable PerfectClip TOI tails (AP-83 / AP-91)

**Date:** 2026-08-07. **Implementer:** one Sonnet agent, after S4b lands.
**Review:** one Opus pass (small slice). **No visual gate** — fully automated.

## What this is, and is not

AP-83 and AP-91 record that the PerfectClip time-of-impact tails in
`CylCollideWithPoint` and `SphereCollideWithPoint`/`FindSphereTimeOfCollision`
(TransitionTypes.cs) were decoded via ACE because the retail x87 sequences do
not decompile. **There is no retail text to port — this slice does NOT "fix"
them.** The deliverable is proof about reachability plus a loud guard, so the
rows become auditable instead of aspirational (the AP-22 resolution shape).

## Premise correction, pinned at scoping — the rows' "no mover sets
PerfectClip" is FALSE as stated

`PhysicsCameraCollisionProbe.cs:69` sets `ObjectInfoState.PerfectClip` on the
CAMERA mover (faithful to retail's camera flags). So containment must be
proven as: **the camera's resolve can never reach the Cyl/Sphere PerfectClip
TOI tails.** Candidate arguments to verify (do not assume any):
1. The viewer exemption block in `FindObjCollisions`/`CollisionExemption`
   (viewer-vs-creature skip, `CollisionExemption.cs:83-85` region) — does it
   skip ALL shadow objects for a viewer mover, or only creatures? A static
   prop with CylSpheres in the camera's sweep would reach the tail if not.
2. Whether the camera resolve enumerates shadow objects at all (retail's
   `update_viewer` sweep may be environment-only — check our port's call
   shape at the camera probe's ResolveWithTransition arguments).
If BOTH arguments fail — the camera genuinely can reach a Cyl/Sphere TOI
tail — that is a FINDING, not a failure: the ACE-derived math is then LIVE
production code for the camera, and the rows get rewritten to say so with
the camera named as the reachable population (severity: camera-feel only).

## Deliverables

1. **Reachability proof or refutation**, written into a short doc: for each
   of the two tails, the exact call chain from every PerfectClip-setting
   mover (grep-proof of the full setter population first — today it is the
   camera probe alone, verify), and where each chain is cut (file:line), or
   not.
2. **The loud guard:** at the head of each TOI tail, a debug-only assertion
   (or diagnostics counter + one-shot log, matching house style for
   invariants) that fires if the tail executes with a mover whose reachability
   was proven impossible — so a future flag change cannot silently start
   executing ACE-derived math nobody re-verified. If the camera IS reachable,
   the guard instead records the tail as camera-live (counter, not assert).
3. **Tests:** one per tail driving the production resolve with a
   PerfectClip mover against a Cyl/Sphere-shaped shadow entity, asserting
   whichever reachability the proof established (reached → the guard counter
   increments and the ACE-derived result is pinned as a golden; unreached →
   the exemption cuts it and the guard stays silent). Sabotage: disable the
   exemption that cuts the chain and watch the reachability flip.
4. Register rewrite text for AP-83/AP-91 handed to the session lead
   (rows stay ACTIVE either way — the math remains ACE-derived — but their
   population claim becomes measured).

## Scope — OUT

Any change to the TOI math itself. The camera's flag set (retail-faithful).
Register/ISSUES edits (session lead).

## Acceptance

Scoped build/test green (Core + Core.Tests; clean-room for the verdict run);
sabotage reported verbatim; nothing committed. Absolute paths, no subagents,
contradictions → STOP.