diff --git a/docs/superpowers/specs/2026-06-02-phase-w-transition-membership-and-pview-render-design.md b/docs/superpowers/specs/2026-06-02-phase-w-transition-membership-and-pview-render-design.md
index 963b26c..0f0af09 100644
--- a/docs/superpowers/specs/2026-06-02-phase-w-transition-membership-and-pview-render-design.md
+++ b/docs/superpowers/specs/2026-06-02-phase-w-transition-membership-and-pview-render-design.md
@@ -47,6 +47,39 @@ membership-return fix alone is expected to stop the flicker; the prune is correc
 after. (This makes the shipped W2b doubly wrong — wrong location *and* wrong mechanism — and it
 is reverted.)
 
+## 1a. Stage-1 gate finding (2026-06-02) — the deeper root is `FindEnvCollisions:1947`
+
+Stage 1 (return `sp.CurCellId`) shipped (`3e1d502`) and was visually gated. **The doorway strobe
+PERSISTS:** `[cell-transit]` (now fed by `sp.CurCellId`) still flips `0170↔0031` at a ~0.2 m
+jitter. So the swept cell is itself tainted — Codex's "verify before delete" caution was correct.
+
+**Airtight root (code analysis):** `Transition.FindEnvCollisions` re-derives the cell from the
+**static** sphere origin via `engine.ResolveCellId(sp.GlobalSphere[0].Origin, …)` at
+`TransitionTypes.cs:1947` at the *start* of every sweep pass and overwrites `sp.CheckCellId`
+(`:1949`). `ValidateTransition` then latches that into `sp.CurCellId`. This is a **second, earlier
+static re-derive** the four studies under-analyzed (they all targeted the late return-site). It is
+the **only** path that can set an indoor swept cell to outdoor: the containment pick
+(`FindCellSet`/`BuildCellSetAndPickContaining` at `:2075`) skips outdoor landcells (no `CellBSP`),
+so `:1947→:1949` is the sole outdoor-taint source. Stage 1's return fix was necessary but
+insufficient; `:1947` is the load-bearing taint.
+
+**Why it's not a one-line delete:** `:1947` is dual-purpose — it is *both* the jitter source *and*
+the only indoor→outdoor exit mechanism acdream has (naive removal fixes the strobe but strands the
+player indoors, unable to walk out). Stage 2 must **replace** it with a retail-faithful directed
+exit-portal crossing (`CEnvCell::find_transit_cells` exit-portal path — become outdoor by crossing
+the doorway polygon, not by a static re-resolve) plus the `do_not_load_cells` prune for indoor
+candidate stability, and re-gate `CellTransit.FindTransitCellsSphere`'s unconditional
+`exitOutside=true` (`CellTransit.cs:95-123`). This is the genuine transition-cell-tracking rework;
+it is `#98`-area (FindEnvCollisions/CheckOtherCells) and must be approached carefully, not guessed.
+
+**Render residuals seen at the Stage-1 gate (all expected; Stages 3-5):** outside-looking-in shows
+no interior (walls/floor missing, cellar mouth shows ground) = no PView exterior→interior portal
+(U.5); bluish background + all particles/NPCs at the threshold/stairs = ungated entities + the
+strobe-induced render-root flip (Stage 2 stabilizes the flip; Stage 4 seals); sky-through-door is
+blue/no-clouds and down/up portals show blue = `OutsideView`/portal not drawn (Stage 4); cellar
+renders best (walls+roof) with a blue flicker over the exit = closest to sealed, residual portal.
+None of these are Stage-1 regressions.
+
 ## 2. Target architecture (retail-faithful)
 
 **One cell graph, one membership authority, render obeys it.**