# L67 — four-strate passage walkability

## Cause and fix

The FI, TN, and VS paths use the compiled analytic base evaluator and then the shared strate composer. The “native” 5/5 result was the same composed field with resolved passages removed; it was not a raw-generator probe. The band stage is therefore not the difference. The passage carve and the support/capsule gates are.

- **0–1 SW→FI:** at the failed probe `(21.366, -11.480, -726.367)`, passage 0 first restored support, then passage 1’s bore changed density to `+1.613` (`carve_sdf=-0.292`), removing it. The shared composer now defers that support only when a physically overlapping later bore can reach it, then applies it after the later carve. The column’s natural relief is predictor-driven and tapers at the root; relief rose from `0.172 m` to `0.219 m`.
- **1–2 FI→TN:** at `(2.419, -13.433, -735.870)`, support restoration was rejected by an adjacent route segment’s player-capsule test (`clearance=-0.245 m`, required `0.045 m`). The segment-specific overlap candidates now keep that test local to physically relevant route geometry. The reported `0.2498 m` step came from the audit switching to a neighboring zero crossing on its `0.25 m` scan. Refining and following the same root shows a continuous floor; the step audit now reports `0.000 m`.
- **2–3 TN→VS:** at `(-1.365, -15.673, -897.088)`, the same capsule gate rejected support next to route segment 81 (`clearance=-0.329 m`). The shared segment-overlap handling fixes this link too.

The L66 `passageIndex>0` / `strates.size()>2` switches are gone. “Internal chain” now means both mouths lie inside their endpoint strata content bands and neither endpoint is a SurfaceWorld landing. Lower-mouth body overlap uses actual 3D distance to the mouth and tread, independent of plan length or passage index.

## Audit

All existing thresholds are unchanged. The L66 baseline binary reproduced the original failures.

| Passage | L66 negative control | L67 result |
|---|---|---|
| 0–1 SW→FI | 59 unsupported; column relief `0.172 m < 0.20 m` | 0 unsupported / 0 blocked / 0 grade failures; wall/floor ripple `1.49 / 0.06 cm`; column relief `0.219 m`; wall relief `0.267 m` |
| 1–2 FI→TN | 3 unsupported; wall/floor ripple `6.78 / 2.90 cm`; apparent `0.2498 m` step | 0 / 0 / 0; wall/floor ripple `2.29 / 1.23 cm`; refined step `0.000 m`; wall relief `0.257 m` |
| 2–3 TN→VS | 2 unsupported | 0 / 0 / 0; wall/floor ripple `1.48 / 0.47 cm`; wall relief `0.248 m` |

All three now pass support, blocked, grade, mouth-binding, ripple, and naturalness gates. The detailed final audit is in [`owner-four-strata-route4.log`](../../../../Saved/Linux/l67/logs/owner-four-strata-route4.log); the measured composition trace is in [`l66-root-refined-audit.log`](../../../../Saved/Linux/l67/logs/l66-root-refined-audit.log).

## Controls, hashes, and builds

- The L66 build remains a negative control: it reproduces `59 / 3 / 2` unsupported and the `0.172 m` column relief failure. The expected audit exit is 10.
- The pinned fast tier passes: **269 PASS, 5 diagnostic, overall PASS**. The prior L52 surface-world hash comparison is diagnostic because the route output changed; the changed style-1 baseline is [pinned at v212](hash-baselines/owner-hash-surface-world-style1-v212.log). See the [fast summary](../../../../Saved/Linux/l67/verify/fast-summary.json).
- Evaluator version is **212** (from 211), required because shared tread composition and route selection changed generated output. Source stamp: `d49aa8d941fb390818569243d7783f3e2799795244a8d7ca48e3e640d4a2876f`.
- All four strata produced 12 equal hash rows at each of W1/W8/W12 ([determinism summary](../../../../Saved/Linux/l67/verify/owner-w1-w8-w12-determinism.json)). Clang and GCC builds both pass.
- Changed implementation files are `Standalone/Core/include/VoxelForgeCore/VoxelForgeCore.h`, `Standalone/Core/src/ResolvedLayoutInternal.h`, `Standalone/Core/src/ShapeWorldInternal.h`, `Standalone/Source/OwnerWorldLoader.h`, `Standalone/Source/StreamBenchmarkPipeline.h`, and `Standalone/Tools/verify/verify.py`. No Unreal `Source/` files changed.

## Cost

Three interleaved whole-view pairs per strate, L66→L67 median seconds ([summary](../../../../Saved/Linux/l67/cost/cost-summary.json)):

| Strate | L66 | L67 | Change |
|---:|---:|---:|---:|
| 0 | 1.101 | 1.121 | +1.8% |
| 1 | 1.575 | 1.552 | −1.5% |
| 2 | 0.581 | 0.602 | +3.6% |
| 3 | 0.216 | 0.212 | −1.9% |

Strate 2’s samples overlap (`0.582–0.600 s`) and paired results are within observed run variation. The route chooser now selects the shortest candidate within `0.10 m` of maximum sampled tread clearance, with tangent alignment as a tie-breaker. It also skips an extra closure turn when mouth separation exceeds the tread envelope; the FI→TN route is `114.231 m` rather than the earlier `165.799 m` candidate.

## Captures

Seven JPEGs are in `captures/`; each is under 300 KB. The TN→VS endpoint meshes are sparse in these offscreen views, so those two frames show the nearby cave/strate surface more clearly than the tread.

- 0–1 arrival [26,342 B](captures/passage-0-1-0-arrival-mouth.jpg), departure [40,012 B](captures/passage-0-1-0-departure-mouth.jpg)
- 1–2 arrival [34,298 B](captures/passage-1-2-0-arrival-mouth.jpg), departure [42,450 B](captures/passage-1-2-0-departure-mouth.jpg)
- 2–3 arrival [23,937 B](captures/passage-2-3-0-arrival-mouth.jpg), departure [23,380 B](captures/passage-2-3-0-departure-mouth.jpg)
- Mid-tunnel, 1–2 [22,392 B](captures/passage-1-2-0-mid-tunnel.jpg)

## Failed runs

- The expected L66 negative-control audit exited 10 after reproducing the failures.
- One p0 clipped arrival-camera trial exited 3 because the clip plane left two open contours. It was replaced by the successful uncut SurfaceWorld entrance view.
- A p2 clipped arrival-camera trial also exited 3 on open contours. The final endpoint image uses the no-clip interior view. Both cap failures are recorded in [`failed-capture-trials.log`](../../../../Saved/Linux/l67/logs/failed-capture-trials.log).
- No final capture, Clang/GCC build, determinism run, fast-tier gate, or cost run failed. No run exceeded 30 minutes.

## Audit controls (follow-up)

This section supersedes the earlier wall-ripple values; the support, blocked, grade, mouth, and column results remain as reported. The residual-only gauge omitted `pose.radius` and hid an authored-radius beat:

| Field / gauge | Old gauge (authored radius, linear detrend) | Residual-only gauge |
|---|---:|---:|
| L66 four-strata field | 6.78 cm | 2.21 cm |
| L67 four-strata field | 14.52 cm | 2.29 cm |

On the old gauge, the geometry change raised 1–2 by 7.74 cm. On L67 geometry, the residual-only gauge then removed 12.23 cm; the reported 6.78→2.29 cm drop therefore masked the radius beat. The final gauge keeps `sampleRadius + 0.5*(left+right)` and cubic-detrends each 32 m window. The 0.18 m is the probe depth inside the authored radius; its former standalone subtraction is removed. The cubic baseline leaves the 0–1 and 2–3 taper profiles below 0.01 cm, while 1–2 retains a 4.77 cm authored-radius beat at 7.06 m. Final ripple results are 1.45 / 7.27 / 0.92 cm: 1–2 fails the unchanged 3.5 cm wall limit. Support, blocked, grade, and mouth-binding checks still pass for all three; overall passage audit is 2/3. See [`audit-control-l67-final-owner.log`](../../../../Saved/Linux/l67/logs/audit-control-l67-final-owner.log) and [`audit-control-authored-radius-all.log`](../../../../Saved/Linux/l67/logs/audit-control-authored-radius-all.log).

| Negative control under the updated gauge | Measured | Result |
|---|---:|---|
| L35 wall ribs | 9.75 cm at 6.50 m; limit 3.50 cm | Detected |
| Synthetic wall spheres / floor beads | 5.98 / 5.98 cm; limits 3.50 / 2.50 cm | Detected |
| Synthetic signed-distance floor step | 0.25 m step; 2.97 cm ripple vs 2.50 cm limit | Detected |
| L36 washboard field, five-step root refinement | 6.46 cm; limit 2.50 cm | Detected |
| L23 terrace profile | 2.00 m flat then 0.25 m step | Detected |

No control passed, so no old audit behavior was restored. Logs: [L35 ribs](../../../../Saved/Linux/l67/logs/audit-control-l35-wall-ribs-cubic-audit.log), [L36 washboard](../../../../Saved/Linux/l67/logs/audit-control-l36-washboard-l35field-bisection.log). The L67 synthetic controls are in the final owner log above. One direct link of the current headless code against archived Core libraries failed route setup and was discarded; the control runs used source/Core-matched L35 builds. The follow-up changed only `Standalone/Source/StreamBenchmarkPipeline.h`; Clang Linux build succeeded. No timing run, commit, push, or stash was made.