diff --git a/docs/ISSUES.md b/docs/ISSUES.md
index 71a3d0cb..9da21c58 100644
--- a/docs/ISSUES.md
+++ b/docs/ISSUES.md
@@ -46,37 +46,37 @@ Copy this block when adding a new issue:
 
 ---
 
-## #186 — Indoor→indoor GREY flap at a connecting room (top floor, new house type)
+## #186 — [DONE 2026-07-08 · `8257b9ba`] Indoor→indoor GREY flap at a connecting room (top floor, new house type)
 
-**Status:** OPEN (diagnosed by class only — NOT captured for this instance; investigation report-only)
-**Severity:** MEDIUM · **Filed:** 2026-07-08 · **Component:** render / indoor visibility (viewer-cell root)
+**Status:** CLOSED 2026-07-08 — live gate PASSED (no grey at any camera angle) + probe
+(216 `root=0118` frames, 0 still grey; `0118->0116` now `TRV`, `vis=4`).
+**Severity:** MEDIUM · **Filed:** 2026-07-08 · **Component:** render / indoor visibility (portal side-cull)
 
-**Description:** Top floor of a house type not tried before; a connecting opening/room between two
-parts of the house. Passing through → a brief **GREY** flap (world background). Stopping at the precise
-spot → the WHOLE screen is grey and stays; **turning the camera clears it, turning back → grey again**
-(camera-direction dependent, player stationary).
+**Description:** Top floor of a new house type; a thin connecting cell between two rooms. Passing
+through → brief GREY flap; stopping at the spot → whole screen grey and stays; turning the camera
+clears it, turning back → grey again (camera-direction dependent, player stationary).
 
-**Root cause — NARROWED (report-only; retail SEAMLESS at the same spot → real acdream bug). FULL HANDOFF:
-`docs/research/2026-07-08-186-connector-grey-flap-handoff.md`.** The eye seats in a sparse 5-render-poly
-CONNECTOR cell `0xF6820118` (between player room `0116` and room `0117`), in the doorway threshold looking
-BACK toward `0116`; acdream's render DROPS `0116` (its back-portal is side-culled) so the doorway aperture
-shows the fog clear color = grey. Retail keeps `0116` drawn. **RULED OUT (do not revisit):** null-root/AD-21
-(root valid indoor 88248/88249 frames); viewer-cell root-lag/AD-20 (`eyeInRoot=Y` — eye genuinely inside
-`0118`'s BSP); the color-clear gating (retail's gated `Clear` @ DrawCells `0x005a48a9` is depth/stencil,
-fires AFTER `LScape::draw` — the tempting "3-line fix" is DEAD). Confirmed via workflow `wf_362bbeda-933`
-(4 tracers + synthesis) + live `ACDREAM_PROBE_FLAP` capture + offline cell dump. It's the doorway-FLAP
-FLOOD/PICK family (frozen render, DO-NOT-RETRY-heavy — the deleted `EyeInsidePortalOpening` rescue, the
-`PortalSideEpsilon` root-lag).
+**Root cause (CONFIRMED via live retail cdb trace + dat diagnostic — the report-only "narrowed" note
+was the right FAMILY but the WRONG mechanism):** the render portal side-cull reconstructed each
+doorway's interior side (`PortalClipPlane.InsideSide`) from the cell's **AABB centroid**. For the thin
+connector `0xF6820118` (5 render polys) the bounding-box center falls on the WRONG side of the
+`0118->0116` doorway → the eye read as a back-portal → the forward room `0116` was culled → the
+aperture showed the fog clear color = grey. Retail's `PView::InitCell` (0x005a4b70) AND acdream's own
+PHYSICS path (`CellTransit.cs:190`) read the explicit dat **`PortalSide` bit** (`(Flags&2)==0`); the
+render path was the only one guessing from geometry.
 
-**Next step (retail cdb, do FIRST — binary MATCHES `refs/acclient.pdb`):** at the grey pose, `bp
-SmartBox::update_viewer 0x00453ce0` (dump `viewer_cell` id) and/or `bp PView::DrawCells 0x005a4840` (dump
-`cell_draw_list`). retail `viewer_cell==0116` → PICK fix (acdream over-switches to the connector /
-boom coasts the eye in at `pulledIn=-0.00`); retail roots `0118` but draws `0116` too → FLOOD fix
-(retail admits the back-portal; acdream's side-CULL is the site). Apparatus + code sites + DO-NOT-RETRY
-in the handoff.
+**Fix (`8257b9ba`):** `GameWindow.BuildLoadedCell` derives `InsideSide` from the dat `PortalSide` bit,
+matching retail + physics. Surgical — the dat diagnostic
+(`Issue186…PortalSide_CentroidVsDatBit_AtGreyEye`) shows the bit agrees with the old centroid on every
+portal of these cells EXCEPT the one #186 breaks; the `CornerFlood`/`Issue113` dat helpers updated to the
+same bit keep every real Holtburg/tower/hall flood identical (App 741 / Core 2631 green). Touches neither
+`PortalSideEpsilon` nor the deleted `EyeInsidePortalOpening` rescue.
 
-**Acceptance:** no grey flap passing through OR stopping in the connecting room at any camera angle;
-regression pass on the outside→inside doorway + other multi-room houses.
+**The retail trace OVERTURNED both prior hypotheses:** NOT PICK (both clients root at `0118` at the pose,
+eye ≈ identical) and NOT the handoff's FLOOD-epsilon framing — retail draws `0116` from the `0118` root
+because its dat side bit admits the portal; acdream's centroid guess culled it. Apparatus (kept):
+`tools/cdb/issue186-connector-decider.cdb` (viewer_cell + cell_draw_list decider) + the offline geometry
+test. Handoff (now historical): `docs/research/2026-07-08-186-connector-grey-flap-handoff.md`.
 
 ---
 
diff --git a/docs/research/2026-07-08-186-connector-grey-flap-handoff.md b/docs/research/2026-07-08-186-connector-grey-flap-handoff.md
index 66db80ea..e48edf59 100644
--- a/docs/research/2026-07-08-186-connector-grey-flap-handoff.md
+++ b/docs/research/2026-07-08-186-connector-grey-flap-handoff.md
@@ -1,6 +1,19 @@
 # Handoff: #186 — indoor GREY flap at a top-floor connecting room (new house type)
 
-**Date:** 2026-07-08 · **Status:** ROOT CAUSE NARROWED (report-only) — fix NOT started. It lives in
+> **✅ RESOLVED 2026-07-08 · fix `8257b9ba` · live gate PASSED.** The retail cdb trace (§3, run via
+> `tools/cdb/issue186-connector-decider.cdb`) OVERTURNED both hypotheses below. Retail roots at the
+> connector `0118` at the grey pose (same as acdream — so NOT the PICK fork) AND still DRAWS the player
+> room `0116` from that root — because retail's `PView::InitCell` side test reads the dat **`PortalSide`
+> bit**, while acdream's render path reconstructed the portal's interior side from the cell **AABB
+> centroid**, which mis-sides a THIN connector cell (`0118`, 5 render polys → centroid on the wrong side
+> of the `0118→0116` doorway → back-portal cull → grey). Fix = derive `InsideSide` from the dat bit in
+> `GameWindow.BuildLoadedCell`, matching retail + acdream's own physics (`CellTransit.cs:190`). Surgical
+> (dat diagnostic: agrees with the old centroid on every portal but the one #186 broke). **The §2/§3
+> "acdream drops the room" read was right; the "acdream over-switches the root / flood-epsilon" mechanism
+> was WRONG — it was the InsideSide *source*, not the pick or the epsilon.** Everything below is the
+> pre-fix investigation, kept for the trail.
+
+**Date:** 2026-07-08 · **Status:** ~~ROOT CAUSE NARROWED (report-only) — fix NOT started.~~ RESOLVED (see banner). It lives in
 the FROZEN portal-flood / viewer-cell render code (the doorway-FLAP family that cost weeks), so it needs
 a **retail cdb trace** to pin the last fork BEFORE any code, then a careful change. Milestone: M1.5.