D311: likely root-caused by D336 (head-bob alias read); headless Caverns clean at 2x pool; close after a live combat session

docs/dev/findings.md

@@ -12394,6 +12394,8 @@ This confirms the M-160/M-164/M-165 hypothesis (`## D173`'s own consolidated-nex
 
 **Status:** GUARDED (freeze class neutralized; upstream poison source OPEN — M-194 probe armed). **RULE-2-SIGNOFF (2026-09-19, release review — M-192 item 2):** user approved retention as the stability-maximizing option; classified as a defensive guard against non-finite state in the same class as the accepted D156 guards — it fires only on poison values that indicate an already-broken state and snaps to a valid frame rather than altering any legitimate animation. Previously disclosed in-thread as a D156-guard extension following the already-accepted D156 precedent in this same file; revert is still two small blocks. Cross-refs: D156 (original guard + Facility outro hang), D309/D310 (ruled out for this freeze — no AI involvement).
 
+**2026-09-24 — likely root cause found in D336.** D311's own static pass named `bheadAdjustAnimation` as the one path where a corrupted value reaches `model->speed`. D336 showed that path computing Bond's head-bob start frame from a never-written alias field (`field_5C0` = N64 `model.animframe1`), i.e. uninitialised player-struct bytes, whose garbage depends on memory layout (room-pool size, previous level). That matches D311's intermittent `oldspeed=-1.75e18`-at-transition signature. After the D336 fix: headless Caverns (`-level_39`, user settings incl. the 2× room pool `ma=512000`, scripted movement/turning, ~80 s) gave **0 D156 guards, 0 D311 anomaly lines, no crash**. **Close after one live Caverns combat session (~2 min) stays D156/D311-silent.**
+
 ## D312 — Throwable items (mines, grenades, etc.) can clip through walls in certain spots (user report, v0.3.0 pre-release playtest, 2026-09-18) — FIXED: `bgBuildRoomVtxBounds` mis-reads the G_VTX vertex count on PC (Gfx_le `dma.par` bit-layout shift), collapsing whole batches of wall geometry out of the collision query (diagnosed + fixed, 2026-09-18).
 
 **Reported:** user's last-minute v0.3.0 playtest: thrown/placed throwable items — mines, grenades, "etc." — can pass through wall geometry in certain spots rather than colliding with it. Spot-dependent ("certain spots"), not universal.