VoxelForge/Standalone/Research/WorldAssemblerM3/Linux13/REPORT.md

# VoxelForge M3 Linux13 — route-invariant density

## Field decision and fix

The approved reference is the Core base shape built from the reviewed owner manifest: `Heightfield2D`
for SurfaceWorld and `FloatingIslandFieldV1` for FloatingIslands. L12's base route sampled that
field. Its analytic pages instead fell through to the copied legacy owner `GetDensityAt` evaluator,
so the same key could sample different values after the player crossed into a page. In the L12
SurfaceWorld audit, all 48 base-covered LOD1 candidates had different density; 10 also differed in
mesh, payload, and topology. A 214,375-sample L12 negative-control run measured max/mean density
delta `0.076171875 / 0.0133467594`, 29 sign changes, 170 edge-crossing changes, and up to 1.7778
voxels of surface displacement. The manifest field is the approved Core world and is the reference
kept here.

Changing the page manifest flag alone did not fix FloatingIslands: 8/8 page pairs still failed,
with max density delta `433.925781`, 262,676 sign changes, and 17,188 edge-crossing changes across
343,000 samples. The source fix binds each compiled page to its world's base `FStandaloneShapeWorld`
before publication. Page density, lattice, detail, classification, and solid queries now delegate
to that one evaluator; the legacy page-local evaluator is no longer an independent output route.
`WorldAssemblyEvaluatorVersion` is bumped from 5 to 6.

## Route parity

The L12 evaluator-v5 negative control fails as required: 5/5 selected base/page pairs mismatch. After the fix,
four audits passed: SurfaceWorld seeds 0, 1, and 17, plus FloatingIslands seed 0.

| Compared routes | Pairs | Mismatches |
|---|---:|---:|
| Base vs page (28 clipmap-requested pages; 26 base-covered page controls) | 54 | 0 |
| Base vs native-only shape-free route (SurfaceWorld LOD0) | 27 | 0 |
| Edited base vs edited page | 4 | 0 |
| Same key built in initial and moved-world history | 2 | 0 |
| Tile samples vs exact Core queries at LOD2–8 | 56 | 0 |

All 87 tile-generation pairs match density, mesh, payload, and topology hashes. The 56 higher-LOD
pairs compare the sampled tile lattice to direct `densityAt` / `densityAtLattice` queries; these
also match all sampled densities and solid/air signs. The owner fixture has
`full_res_clip_levels=2`, so analytic page routes exist only at LOD0–1. In total, page comparisons
covered 2,315,250 density samples with zero delta, sign, edge-crossing, or surface-root differences;
6,172,229 exact-query samples had zero mismatches. The audit exits nonzero on any output-hash,
sample, route-verification, exact-query, or proof-violation mismatch.

The history probe builds the same LOD0 key in a second Core world after a 96 m camera move. Both
SurfaceWorld and FloatingIslands match all four hashes across those two build histories. The edit
probe applies a sequence-1 density offset centered on a sampled sign crossing; it changes the field,
and edited base/page results still match.

### Page proof audit

The fill-and-check audit generated page tiles with full density capture and uniform-block proof
verification, so it checked the field those pages actually sample. Across the four audits it checked
1,274 blocks / 1,695,694 samples: 518 blocks used the exact fallback, 6 were unknown, and there were
zero false proofs or violations. SurfaceWorld walkability passed 5,642/5,642, 6,080/6,080, and
4,785/4,785 samples for seeds 0, 1, and 17; FloatingIslands passed 4,000/4,000. Shape readiness
passed 27/27 near-ring tiles where eligible. FloatingIslands has no eligible native-only tiles.

## Cost, hashing off

W12, seed 0, `--force-generate`, camera `0,-35,-487.94`, with the same crossing setup as L12:

| Move | Entering tiles | L12 crossing | L13 crossing | L13 peak RSS |
|---|---:|---:|---:|---:|
| 8 m | 144 | 0.0347 s | 0.0399 s | 468 MiB |
| 16 m | 288 | 0.1249 s | 0.0856 s | 513 MiB |
| 24 m | 432 | 0.1635 s | 0.1242 s | 512 MiB |
| 32 m | 576 | 0.1717 s | 0.1692 s | 511 MiB |
| 1 km | 2,260 | 1.2474 s | 0.7696 s | 673 MiB |

Three W12 spawn runs had medians of 157 ms first tile, 180 ms near ring, and 1.499 s whole view;
L12 medians were 146 ms, 161 ms, and 1.361 s. Each spawn run generated the same 2,553-tile
benchmark view. The final timings are in `Saved/Linux/l13-crossing-final-*.log` and
`Saved/Linux/l13-spawn-final-*.log`.

## Determinism and invariants

All 28 required configurations passed: SurfaceWorld and FloatingIslands seed 0; Clang
`-ffp-contract=off` and GCC default; W1/W8/W12, with five W12 repeats per compiler and recipe. Each
run matched all 12 rows (full detail, whole view, LOD0–8, exact queries) against L12/L11.

| Recipe | Full detail D/M/P/T | Whole view D/M/P/T | Exact density / unclamped / detail / collision |
|---|---|---|---|
| SurfaceWorld | `0x0ee0579bd15cbbe4 / 0x32e5d4964d610fee / 0x1932b96ee4b1d910 / 0x69743c6bad3447dc` | `0xc10697a8f48380c7 / 0xe75c9119a1498cd5 / 0x49a9a8d1835a6c8c / 0xedcb23288b5e8724` | `0xe4d4a8eb95b35933 / 0xe4d4a8eb95b35933 / 0xefcba20c0c70c415 / 0xe604823a249029bf` |
| FloatingIslands | `0x6d842d2878b08ef6 / 0x4b868a3184f08035 / 0x2cedf2236788752d / 0xeac17d5e0cb5044a` | `0x5be4d8cde79b2a76 / 0x96f75041f6861b3a / 0x3700a516cc89d50c / 0x6b99948d6eab4f21` | `0x61daded9c303becb / 0x61daded9c303becb / 0xefcba20c0c70c415 / 0x84d37463be9b0573` |

The crossing output changes as intended. The 24 m W1 and W12 moved-tile hashes match each other:
`0x337ca62131576728 / 0x7612f48e2ddbbaab / 0x69a67ed4add83b87 / 0xf11ac1ebd0f7ddb8` (D/M/P/T),
replacing L12's `0x174588abdc8c0d2c / 0x4c401e27d9d05dea / 0xeb10d9801c5ef125 / 0xf59d12304d0dcb4a`.

The L3 FP-contract preamble and runtime self-test, L4 `FLazy`, L7 shared column cache, L9/L12
proofs, and L11 native-only readiness/crash fixes were preserved. The L6 screen-space controls
still pass their six same-LOD checks and reject the missing/floating-surface, global-octave, and
stride-2 negative controls as required. Its whole gate still rejects the known far-field error over
the 1 px bound (exit 6); the route binding does not affect those LOD3–8 base-field comparisons.
The asynchronous MPSC/Epoch path and `ARCHITECTURE.md` §8.10 invariants are unchanged. No Unreal
adapter files were touched; the Core exact-query and collision-sign routes were checked, but Unreal
collision cooking was not built here. `ARCHITECTURE.md` §8.36 and `CODEMAP.md` §3.22 document the new
route law.

Builds and runs used CPUs 0–11, at most 12 workers, a 6 GiB address-space cap, and a 6,000,000,000
byte RSS monitor. The governor remained `powersave`. Peak sampled RSS was 904 MiB across runs
(673 MiB in the no-hash cost table); the GCC build process group peaked at 4.27 GiB. Clang and GCC
builds passed. No system changes or Unreal builds were made.

## Failed and retried runs

- `l13-route-baseline-s0-w12.log` exited 2 because the inferred binary-relative owner JSON path did
  not exist; reruns used the explicit repository JSON. The first baseline capture used the wrong
  camera, then an audit pass had empty proof-skipped density captures; the final L12 negative
  control is `l13-route-baseline-s0-w12-r4.log`.
- `l13-route-fi-diagnostic.log` and `l13-route-fi-diagnostic-r2.log` intentionally exposed the
  remaining FloatingIslands split before the shared-source binding; both exit 9 on 8/8 mismatches.
- `l13-route-edit-s0.log` exited 9 because its brush did not change the selected tile. Centering the
  brush on a sampled sign crossing fixed the audit in `l13-route-edit-s0-r2.log`.
- `l13-route-history-sw-s0.log` exited 9 because the second-world probe exceeded the 4,096-node
  region compiler envelope. The retry compiles one matching LOD0 anchor tile and passes.
- The first `l13-cost-*` measurements omitted `--force-generate` and used the owner JSON start;
  those are not used above. The final crossing and spawn runs use L12's camera and force-generation
  setting. The screen-space run's exit 6 is its expected far-field rejection, not a retried run.
- All final builds, the 28 hash runs, eight no-hash cost runs, and two crossing-hash runs completed
  within their limits. No commit, push, or stash was made.

## Multiplayer note for the owner

Peers with the same manifest, seed, evaluator version 6, and tile key now reconstruct the same Core
density and tile output through each available base, page, or native-only route, regardless of
arrival history; terrain geometry still does not need to cross the network. Player edits remain an
explicit versioned diff that must be ordered and synchronized between peers.

## Orchestrator review (Claude)

- **Spawn cost re-run by me, 5 interleaved W12 pairs, no hashing:** whole view L12
  1.385/1.405/1.419/1.443/1.460 s vs L13 1.401/1.448/1.430/1.435/1.451 s (median 1.419 → 1.435 s,
  +1.1%, within noise); near ring 0.168 → 0.171 s. The +10% in the cost table above compares L13 runs
  with L12 numbers from another session; interleaved, there is no measurable spawn regression.
- The fix is structural: pages are bound to their world's single base `FStandaloneShapeWorld`
  evaluator before publication, so routes can't diverge by construction. The negative control fails
  on L12 (5/5), and the 87 tile pairs, 56 exact-query pairs and 2.3M page samples show 0 mismatches
  after. The page lifetime is safe because the base shape is owned by the `World` and outlives its pages.
- Crossing output changed, as intended (evaluator version 5 → 6); the spawn and island worlds are
  unchanged.