diff --git a/docs/dev-process.md b/docs/dev-process.md
index 59e6aaea..f1147b16 100644
--- a/docs/dev-process.md
+++ b/docs/dev-process.md
@@ -63,6 +63,18 @@ The classes it currently tracks:
 - whole serialized formats are converted by an **offline sidecar** rather than
   patched at runtime.
 
+**Two process lessons from the sibling GEVR VR port** (same decomp lineage,
+reference-only survey in `scratchpad/GEVR-TRIAGE.md` item D — their corpus
+hit both repeatedly enough to name them): (1) **a grep standing in for a
+read** — a site list built by grepping one helper name or spelling misses
+siblings spelled differently or living in an adjacent file (their own
+missed-smoke-scissor-site example); treat a grep-built site list as a draft,
+not a census, until it's been read against. (2) **write the falsifier before
+the run** — state up front what result would kill the hypothesis ("if X
+survives, hypothesis Y is dead"), not just what would confirm it; this fits
+the existing budget/findings discipline directly and costs one sentence per
+brief.
+
 ## 3. Parallelise by file, consolidate often
 
 Lewis ran multiple git worktrees and found the real cost was
diff --git a/docs/dev/WIDESCREEN-FOV-PLAN.md b/docs/dev/WIDESCREEN-FOV-PLAN.md
index 164ec8f3..8577d50d 100644
--- a/docs/dev/WIDESCREEN-FOV-PLAN.md
+++ b/docs/dev/WIDESCREEN-FOV-PLAN.md
@@ -125,6 +125,43 @@ From the `pd_port` checkout (N64 PD had no widescreen; the port added it):
   ("Decide Phase 1" below) — correcting an earlier note here that overstated
   this as settled.
 
+### 6. GEVR portal-scissor findings — read before Phase 2/3 game-code work
+
+The sibling GEVR VR port (same n64decomp/007 lineage, reference-only survey
+in `scratchpad/GEVR-TRIAGE.md` item A) independently measured, on the same
+decomp, that widescreen "missing wall / see-through slab" artifacts come
+from the **per-room portal `SETSCISSOR` rects**, not the room-visibility
+pass (their cull census was byte-identical between arms) — giving every room
+the full view removed the artifacts (one level, one viewpoint; treat as a
+hypothesis, not settled). Re-derived in **our** tree (2026-07):
+
+| Class | Our sites | Notes |
+|---|---|---|
+| SCISSOR — room passes | `bg.c:685`, `bg.c:747` (`bgScissorCurrentPlayerViewF`) | primary + secondary/xlu |
+| SCISSOR — default variants | `bg.c:723`, `bg.c:1306`, `chrprop.c:598` (via `bgScissorCurrentPlayerViewDefault`, `bg.c:1332`) | |
+| SCISSOR — characters | `chr.c:3070/3074` (`chrRender`) | |
+| SCISSOR — explosions | `explosion.c:876/880` **and `explosion.c:1488/1492` (smoke)** | the smoke site is the one GEVR missed on their first pass |
+| CULL (removes props, not pixels) | `propobj.c:13584` `posIsOnScreen` (used at `:5881`) | a too-tight rect *deletes* a prop — GEVR's black-wall candidate |
+| **AI / SPAWN logic** | `chraction.c:10628` `chrIsPosOffScreen` → `bgGet2dBboxByRoomId` (`bg.c:573`) | reads the rect for character AI/spawn decisions |
+
+**Design trap (their hardest-won lesson):** do NOT put a clip/widescreen
+knob inside `bgGet2dBboxByRoomId` — it's the chokepoint that also feeds
+`chrIsPosOffScreen`, so a "clip-only" change there would silently alter what
+characters do. Scissor sites can be widened directly; the cull box and the
+AI/spawn consumer must be reasoned about separately.
+
+**Caveats:** (1) removing all per-room scissoring has an unknown
+overdraw/perf cost — measure before shipping; (2) their fix evidence is one
+level + one viewpoint; (3) the "two notions of view width" trap (their doc
+278): a port knob that redefines native content width from the *window*
+aspect while the game's scissor-tracked canvas stays 4:3 leaves ~29% of
+columns undrawn → stale-buffer slabs. Whatever this plan's implementation
+does, the game's canvas notion and the window notion must be reconciled
+explicitly at one named place — re-verify the line numbers above (cheap
+greps: `bgScissorCurrentPlayerView`, `bgGet2dBboxByRoomId`, `posIsOnScreen`,
+`chrIsPosOffScreen`) before acting on them, since this table predates any
+Phase 2/3 work actually landing.
+
 ## Option B — the standard (native 16:9, PD-parity)
 
 ### Architecture
diff --git a/docs/porting-notes.md b/docs/porting-notes.md
index d1a44af0..aba04c8c 100644
--- a/docs/porting-notes.md
+++ b/docs/porting-notes.md
@@ -1225,3 +1225,30 @@ and turns every such overrun into a fatal `*** stack smashing detected ***`
   path (`cd C:\Users\...`) is unreliable in this same shell and can silently
   mis-parse to a mangled path on a later command in the same tool call —
   prefer `cd /c/Users/...` (forward slashes) for the build working directory.
+- **A crash fault address of `0xffffffffffffffff` on x86-64 usually means a
+  non-canonical #GP from a garbage-high-bits pointer (bits 63:48 not a sign
+  extension of bit 47), not a computed `-1` sentinel** (cross-validated
+  against the sibling GEVR VR port, same decomp lineage — see
+  `scratchpad/GEVR-TRIAGE.md` item C; we independently hit the same register
+  shape in D191). Two companion habits worth keeping: re-read map anchors
+  from the freshly rebuilt map after every rebuild (a stale map silently
+  resolves the wrong symbol), and confirm the fault PC actually disassembles
+  on an instruction boundary before trusting a resolved symbol.
+- **Frame-rate assumptions — read before proposing any non-60 Hz mode**
+  (cross-validated against GEVR, `scratchpad/GEVR-TRIAGE.md` item B). GE's
+  logic is delta-scaled through `g_GlobalTimerDelta` (~216 call sites); the
+  PAL build (×1.2) is a shipping proof that delta-scaled code tolerates
+  other rates. But: **Bond's walk is frame-rate dependent by construction**
+  — `MoveBond` (`bondview2.c`) is an exponential approach toward a target,
+  advanced once per frame with no timestep, so convergence is measured in
+  frames, not seconds (GEVR measured ~1.487× walk speed at 90 Hz vs 60 Hz,
+  ≈90/60 exactly). Turn/aim *is* delta-scaled; walk is not. High-refresh or
+  uncapped presentation modes are therefore out of scope without a
+  game-logic change, which is forbidden — we tick at fixed 60 Hz (D52
+  pacing) by design, not as a limitation to fix. Also: `g_ClockTimer` must
+  stay integer (24 iteration sites depend on it); of 44
+  `/g_GlobalTimerDelta` divide sites, 40 are guarded (three different
+  spellings) and 4 are not (front-end cast camera `front.c:8271-8273`,
+  `propobj.c:~2393`) — those 4 rely on div-by-zero yielding NaN/inf without
+  trapping on both MIPS and x86-64 SSE, matching retail behavior; do not
+  "fix" them.