# L158 — Flat landing pad

| Tunnel end | Before (L151) | After (L158) | Wide pad view (L158) |
|---|---|---|---|
| passage/0-1/0 · upper | ![L151 upper landing, passage 0-1](../Linux151/captures/after-l151-0-1-0-upper-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |
| passage/0-1/0 · lower | ![L151 lower landing, passage 0-1](../Linux151/captures/after-l151-0-1-0-lower-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |
| passage/1-2/0 · upper | ![L151 upper landing, passage 1-2](../Linux151/captures/after-l151-1-2-0-upper-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |
| passage/1-2/0 · lower | ![L151 lower landing, passage 1-2](../Linux151/captures/after-l151-1-2-0-lower-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |
| passage/2-3/0 · upper | ![L151 upper landing, passage 2-3](../Linux151/captures/after-l151-2-3-0-upper-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |
| passage/2-3/0 · lower | ![L151 lower landing, passage 2-3](../Linux151/captures/after-l151-2-3-0-lower-landing.jpg) | Not captured: seed 0 stops during pad planning. | Not captured. |

## Result

**L158 is stopped and not shipped.** Three planner attempts failed the seed-0 fast fixture. The last one could not find a lower pad floor satisfying both its edge-ring interval and the route transition. The pad stamp never reached composed-field evaluation, so this is not evidence that the clamp formula itself fails. It does meet the requested stop condition; I did not continue tuning it.

The attempted v240 source edits were restored to `wip/l134-cave-planner` HEAD. No baselines were changed. The pre-existing untracked `Linux18/exports/` directory was left untouched.

## What failed

- Attempt 1 clamped both route ends without limiting each clamp to its own `R+B`; strict validation found an upper mouth binding error and route grades above 15°.
- Attempt 2 limited route rewrites to each pad’s `R+B`; strict validation still found route grades above 15° at the transition.
- Attempt 3 linearly rewrote the route profile between the flat-disc boundary and an outside route point, and checked that point during site fitting. The fast fixture then failed before snapshot creation: `lower landing pad has no feasible floor on its edge ring or next route site`.

These attempts and the final failed log are under `Saved/Linux/l158/fast/`. The final run used source stamp `447f2cb268a0b3a06c1994f6c58914f698e9ea66d686bd16e78f20ec72233c81`.

## Checks and measurements

- Clang 19 candidate build passed with `--fp-contract=off --jobs=4`, CPUs 0–11, and the 6 GiB address-space limit.
- Fast tier failed at `owner-floating-islands-style2-clang` with exit code 2. The [log](../../../../Saved/Linux/l158/fast/owner-floating-islands-style2-clang.log) records the lower-pad planning failure; the [tier summary](../../../../Saved/Linux/l158/fast/fast-summary.json) records the failed gate.
- `git diff --check` passed after restoring the candidate source. The worktree has no tracked source changes.
- No performance timings were taken, so there is no timing window or L80 result to report.

The 16-seed Tunnel Network and Vertical Shafts sweeps, `LandingPadAudit` and its four controls, interior-air/shell/seam/route/envelope gates, Clang/GCC W1/W8/W12, L80 for all four layers, UE start and 30 m/s run, and L158 captures were not run. No evaluator-version bump or baselines were retained. No Unreal `Source/` files changed.

## Remaining risk

The requested planner constraints remain unresolved. In particular, the last check coupled the pad edge-ring floor to an outside passage-route height and had no feasible lower site on the fast fixture. Since planning stopped before field composition, the clamp’s actual terrain blend, bore mask, bounds, and seed-sweep behavior remain unmeasured.