wip(assembler): M2 round 3 -- opt-in hybrid sharp mesher (WorldAssemblerHybridV1) in the Unreal Core route

Default MarchingCubesV1 unchanged (W1/W8/W16 = round-6 hashes). Hybrid DC only in LOD0 interior cells
with tagged features; tile-border cells and LOD1+ stay MC. BuildHost: fixtures repeat exactly, cooked
collision bounds = render bounds, same-LOD borders pass, sampled SurfaceWorld cliff bit-identical to MC.
Open: tagged tiles cost 5.7-6.7x MC; corner-top field contact error 20 cm; 5 MC doorway LOD cases.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -1,7 +1,11 @@
 [CmdletBinding()]
 param(
     [ValidateRange(60, 900)][int]$TimeoutSeconds = 900,
-    [string]$WorldAssemblyManifestPath = ''
+    [string]$WorldAssemblyManifestPath = '',
+    [ValidateSet('MarchingCubesV1', 'WorldAssemblerHybridV1')][string]$CoreMesherRecipe = 'MarchingCubesV1',
+    [switch]$EnableHybridFixturePlacement,
+    [switch]$HybridCliffOnly,
+    [switch]$HybridFixturesOnly
 )
 
 # Exercise AVoxelWorld Core streaming, collision, anchor movement, and carving in BuildHost only.
@@ -83,6 +87,21 @@ $ManifestData = Get-Content -LiteralPath $StagedWorldAssembly -Raw | ConvertFrom
 if ($ManifestData.content_hash -ne '8933693d9560ba9f') {
     throw "BuildHost world assembly input is not the reviewed round-4 manifest: $($ManifestData.content_hash)"
 }
+if ($EnableHybridFixturePlacement -and $CoreMesherRecipe -ne 'WorldAssemblerHybridV1') {
+    throw 'Hybrid fixture placement requires -CoreMesherRecipe WorldAssemblerHybridV1.'
+}
+if ($HybridCliffOnly -and $CoreMesherRecipe -ne 'WorldAssemblerHybridV1') {
+    throw '-HybridCliffOnly requires -CoreMesherRecipe WorldAssemblerHybridV1.'
+}
+if ($HybridCliffOnly -and $EnableHybridFixturePlacement) {
+    throw '-HybridCliffOnly uses the reviewed native cliff manifest and cannot add the surface fixtures.'
+}
+if ($HybridFixturesOnly -and $CoreMesherRecipe -ne 'WorldAssemblerHybridV1') {
+    throw '-HybridFixturesOnly requires -CoreMesherRecipe WorldAssemblerHybridV1.'
+}
+if ($HybridFixturesOnly -and ($HybridCliffOnly -or $EnableHybridFixturePlacement)) {
+    throw '-HybridFixturesOnly cannot be combined with the other focused hybrid modes.'
+}
 
 $CrashBefore = @{}
 foreach ($CrashRoot in $CrashRoots) {
@@ -107,6 +126,10 @@ function Get-NewCrashFolders {
     return @($Found.ToArray())
 }
 
+$HybridMesherFlag = if ($CoreMesherRecipe -eq 'WorldAssemblerHybridV1') { 1 } else { 0 }
+$HybridFixturePlacementFlag = if ($EnableHybridFixturePlacement) { 1 } else { 0 }
+$HybridCliffOnlyFlag = if ($HybridCliffOnly) { 1 } else { 0 }
+$HybridFixturesOnlyFlag = if ($HybridFixturesOnly) { 1 } else { 0 }
 $BaseArguments = @(
     ('-project="{0}"' -f $HostProject),
     '-nullrhi', '-unattended', '-nop4', '-nosplash', '-NoSound',
@@ -119,6 +142,10 @@ $BaseArguments = @(
     '-modes=export', '-gameconfig=1', '-coreworldtest=1',
     '-settingsref=/Game/VoxelForge/DA_Settings.DA_Settings',
     ('-coreworldassembly="{0}"' -f $StagedWorldAssembly),
+    ("-corehybridmesher=$HybridMesherFlag"),
+    ("-corehybridfixtureplacement=$HybridFixturePlacementFlag"),
+    ("-corehybridcliffonly=$HybridCliffOnlyFlag"),
+    ("-corehybridfixturesonly=$HybridFixturesOnlyFlag"),
     ('-out="{0}"' -f $OutputDirectory)
 )
 
@@ -199,6 +226,40 @@ if (-not (Test-Path -LiteralPath $FinalLog -PathType Leaf)) {
     $FinalLog = Join-Path $LogDirectory 'CoreWorldValidation.retry.log'
 }
 $Text = Get-Content -LiteralPath $FinalLog -Raw
+if ($HybridFixturesOnly) {
+    foreach ($Fixture in @('corner90', 'doorway', 'riser1m', 'cliff_ledge', 'organic_cave_chamber')) {
+        $FixtureMarker = '\[WorldAssemblerHybridPluginFixture\] name=' +
+            [regex]::Escape($Fixture) + ' lod=0 .*exact_repeat=1'
+        if ($Text -notmatch $FixtureMarker) {
+            throw "BuildHost fixture log is missing '$Fixture'. See $FinalLog."
+        }
+    }
+    if ($Text -notmatch '\[WorldAssemblerHybridPluginBorder\] same_lod=PASS independent=1' -or
+        $Text -notmatch '\[WorldAssemblerHybridPluginBorder\] lod0_lod1_doorway=1 cases=125 over_50cm_cases=0') {
+        throw "BuildHost fixture log is missing passing border probes. See $FinalLog."
+    }
+    $NewCrashes = @(Get-NewCrashFolders)
+    if ($NewCrashes.Count -gt 0) {
+        throw "New UECC crash folders appeared during plugin fixture checks: $($NewCrashes -join '; ')"
+    }
+    Write-Host "VOXELFORGE_CORE_HYBRID_FIXTURES_PASS recipe=$CoreMesherRecipe analytic=5 borders=1"
+    Write-Host "Core actor log: $FinalLog"
+    Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"
+    return
+}
+if ($HybridCliffOnly) {
+    if ($Text -notmatch '\[WorldAssemblerHybridNativeCliff\] key=\(-22,13,-58\) lod=0 .*bit_identical=1 type4_only=1') {
+        throw "BuildHost log is missing the sampled native SurfaceWorld cliff identity proof. See $FinalLog."
+    }
+    $NewCrashes = @(Get-NewCrashFolders)
+    if ($NewCrashes.Count -gt 0) {
+        throw "New UECC crash folders appeared during the native cliff check: $($NewCrashes -join '; ')"
+    }
+    Write-Host "VOXELFORGE_CORE_HYBRID_CLIFF_PASS recipe=$CoreMesherRecipe bit_identical=1"
+    Write-Host "Core actor log: $FinalLog"
+    Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"
+    return
+}
 foreach ($Phase in @('initial', 'anchor', 'edit', 'surface_travel', 'surface_strate_travel')) {
     if ($Text -notmatch "\[VoxelForgeCoreWorldTest\] pass phase=$Phase") {
         throw "BuildHost Core actor log is missing the '$Phase' validation marker. See $FinalLog."
@@ -207,8 +268,42 @@ foreach ($Phase in @('initial', 'anchor', 'edit', 'surface_travel', 'surface_str
 if ($Text -notmatch '\[VoxelForgeCoreWorldTest\] worker_hash_matrix=1/8/16 stable=1') {
     throw "BuildHost Core actor log is missing the W1/W8/W16 determinism marker. See $FinalLog."
 }
-if ($Text -notmatch '\[VoxelForgeCoreWorldTest\] world_assembly_hash=8933693d9560ba9f plans=1 native=1') {
-    throw "BuildHost Core actor log does not prove the reviewed native SurfaceWorld plan was attached. See $FinalLog."
+$ExpectedRuntimeAssemblyHash = $ManifestData.content_hash
+if ($EnableHybridFixturePlacement) {
+    $FixtureHashMatch = [regex]::Match($Text,
+        '\[VoxelForgeCoreWorldTest\] hybrid_fixture_placement=1 boxes=9 contacts=5 manifest_hash=([0-9a-f]{16})')
+    if (-not $FixtureHashMatch.Success) {
+        throw "BuildHost actor log is missing the generated hybrid fixture manifest hash. See $FinalLog."
+    }
+    $ExpectedRuntimeAssemblyHash = $FixtureHashMatch.Groups[1].Value
+}
+$AssemblyMarker = '\[VoxelForgeCoreWorldTest\] world_assembly_hash=' +
+    [regex]::Escape($ExpectedRuntimeAssemblyHash) + ' plans=1 native=1'
+if ($Text -notmatch $AssemblyMarker) {
+    throw "BuildHost actor log does not prove the expected native SurfaceWorld plan was attached. See $FinalLog."
+}
+$RecipeMarker = '\[VoxelForgeCoreWorldTest\] world_initialized=1 recipe=' +
+    [regex]::Escape($CoreMesherRecipe)
+if ($Text -notmatch $RecipeMarker) {
+    throw "BuildHost actor log does not confirm the requested $CoreMesherRecipe runtime selection. See $FinalLog."
+}
+if ($CoreMesherRecipe -eq 'WorldAssemblerHybridV1') {
+    foreach ($Fixture in @('corner90', 'doorway', 'riser1m', 'cliff_ledge', 'organic_cave_chamber')) {
+        $FixtureMarker = '\[WorldAssemblerHybridPluginFixture\] name=' +
+            [regex]::Escape($Fixture) + ' lod=0 .*exact_repeat=1'
+        if ($Text -notmatch $FixtureMarker) {
+            throw "BuildHost log is missing the production mesher fixture '$Fixture'. See $FinalLog."
+        }
+    }
+    if ($Text -notmatch '\[WorldAssemblerHybridPluginBorder\] same_lod=PASS independent=1') {
+        throw "BuildHost log is missing the independent same-LOD border proof. See $FinalLog."
+    }
+    if ($Text -notmatch '\[WorldAssemblerHybridPluginBorder\] lod0_lod1_doorway=1 cases=125 over_50cm_cases=0') {
+        throw "BuildHost log is missing a passing 125-phase MC doorway contour result. See $FinalLog."
+    }
+}
+if ($EnableHybridFixturePlacement -and $Text -notmatch '\[VoxelForgeHybridCollisionContact\] pass=1 probes=5') {
+    throw "BuildHost log is missing the cooked hybrid fixture trace contacts. See $FinalLog."
 }
 if ($Text -notmatch '\[VoxelForgeCoreWorldTest\] native_biome_field=1 .*sampled_biomes=[2-9]') {
     throw "BuildHost Core actor log does not prove native SurfaceWorld biome assignment. See $FinalLog."
@@ -241,6 +336,6 @@ $NewCrashes = @(Get-NewCrashFolders)
 if ($NewCrashes.Count -gt 0) {
     throw "New UECC crash folders appeared during Core actor validation: $($NewCrashes -join '; ')"
 }
-Write-Host 'VOXELFORGE_CORE_WORLD_PASS streaming=1 collision=1 anchor_move=1 carve=1'
+Write-Host "VOXELFORGE_CORE_WORLD_PASS recipe=$CoreMesherRecipe fixtures=$HybridFixturePlacementFlag streaming=1 collision=1 anchor_move=1 carve=1"
 Write-Host "Core actor log: $FinalLog"
 Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"