Indoor cell BSP queries at TransitionTypes.cs:1442 were calling
BSPQuery.FindCollisions with Quaternion.Identity + defaulted
Vector3.Zero worldOrigin. Inside the BSP, Path 3 (step_sphere_down)
and Path 4 (land-on-surface) use those params to build the
world-space ContactPlane. Result: planes written with D ~ 0 instead
of the cell's world floor Z (e.g. -94.02 for Holtburg cottages).
320 corrupt CP writes per Holtburg session per the [cp-write] probe.
Fix: decompose cellPhysics.WorldTransform once at the call site,
pass the rotation as localToWorld and the translation as
worldOrigin. Mirrors the existing correct pattern at :1808
(FindObjCollisions, passes obj.Rotation + obj.Position).
Retail oracle: BSPTREE::find_collisions (acclient_2013_pseudo_c.txt:323924)
calls Plane::localtoglobal at :323921 before set_contact_plane.
Our TransformNormal + TransformVertices + BuildWorldPlane chain is
the equivalent — it just needs the right rotation + origin.
Spec: docs/superpowers/specs/2026-05-20-indoor-bsp-worldorigin-fix-design.md.
Plan: docs/superpowers/plans/2026-05-20-indoor-bsp-worldorigin-fix.md.
Evidence: launch-cp-probe.log capture 2026-05-20, [cp-write] probe.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
de8ffde4ca