# Linux155 — chamber floor plane reached the stop rule

| Landing chamber | Before (L151) | After (L155) |
|---|---|---|
| passage/0-1/0 · upper | ![L151 upper landing](../Linux151/captures/after-l151-0-1-0-upper-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |
| passage/0-1/0 · lower | ![L151 lower landing](../Linux151/captures/after-l151-0-1-0-lower-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |
| passage/1-2/0 · upper | ![L151 upper landing](../Linux151/captures/after-l151-1-2-0-upper-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |
| passage/1-2/0 · lower | ![L151 lower landing](../Linux151/captures/after-l151-1-2-0-lower-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |
| passage/2-3/0 · upper | ![L151 upper landing](../Linux151/captures/after-l151-2-3-0-upper-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |
| passage/2-3/0 · lower | ![L151 lower landing](../Linux151/captures/after-l151-2-3-0-lower-landing.jpg) | Not captured: the planner rejected the candidate before a resolved layout was written. |

## Result

Stopped after three failed fits for cause 1, as instructed. A single planar chamber floor cannot satisfy the seed-2 Surface World route's ground and capsule-foot bounds while joining the current passage floor at the bore. The rejected candidate was removed from production source. The branch remains at HEAD, evaluator v239. Causes 2 and 3 were not attempted; no baseline or version change was made.

## Measured plane conflict

The receiving route runs along +X through the upper chamber. Its route-point Z is the player-center height; the ground bound is route Z − 0.98 m, and the capsule-foot bound is route Z − 0.88 m. The chamber center floor at the bore is `-374.831 m`. With the endpoint fixed to the planned `h(s)` value:

- At route point `x=24.25 m`, the capsule-foot bound requires `gradient_x ≤ -1,024 Q16` (−1.56%).
- At route point `x=26.75 m`, the ground bound requires `gradient_x ≥ 1,989 Q16` (+3.03%).

The constraints do not overlap. The third fit allowed the bore endpoint and first 10 m of `h(s)` to rise together by up to 99 subvoxels (`0.0967 m`, the remaining capsule-foot clearance). At that limit the same points require `gradient_x ≤ -9,472 Q16` and `gradient_x ≥ 39 Q16`; they still do not overlap.

## Attempts

1. Fit the floor slope above route ground and preserve the bore-center height. The route support audit fell from 5 unsupported samples to 0, but the passage then blocked 481 capsule samples. Plan grade stayed under 15°. Log: [`cause1-seed2.log`](../../../../Saved/Linux/l155/cause1-seed2.log).
2. Add the capsule-foot upper bound. Strict planning rejected the layout because no gradient fit both bounds with the bore floor fixed. Log: [`cause1-bounded-seed2.log`](../../../../Saved/Linux/l155/cause1-bounded-seed2.log).
3. Allow a bounded center raise and taper it through the first 10 m of `h(s)`. The route and capsule constraints remained infeasible; planning rejected before producing a layout. Log: [`cause1-between-seed2.log`](../../../../Saved/Linux/l155/cause1-between-seed2.log). The final rejected fit is archived in [`failed-plane-fit.patch`](failed-plane-fit.patch).

## Checks and limits

- Clang 19 candidate builds passed for each compiled planner variant. The first candidate's focused seed-2 audit completed and failed on 481 blocked capsule samples; the second and third failed strict layout planning.
- `git diff --check` passed after restoring the production source to HEAD. No production or Unreal `Source/` files remain changed.
- L154 had already measured the HEAD fast-tier failure on the Floating Islands chamber content band. Fast tier was not rerun after the three-fix stop.
- Not run: causes 2 and 3, full fast tier, either 16-seed sweep, determinism, owner baselines, L80 timing, Linux UE build/start/movement, or after captures.

## Remaining risk

The measured conflict is between a single plane and the receiving route's local height variation across the 7.5 m chamber footprint. Resolving it needs a different floor representation or a change to the receiver route/bore join. The chamber support-audit exemption and Floating Islands content-band failure remain open.