wip(assembler): M3 round 3 -- separated islands + Unreal island route (owner build 18:46)

Islands read as separate (91.89% open sky at mid-height), underside cavity closed,
rim teeth were capture shading. Island manifest import + BuildHost proof passed on the
pre-cache tree; M1 SurfaceWorld and M2 V1/V2 gates passed.

Known open: final XY-column cache compiled in the owner build but is unverified;
island LOD0 p95 ~155 ms misses the 133 ms sprint deadline (legacy ~43 ms); the island
manifest only fits the BuildHost fixture layout (owner's world: Core init fails,
empty world) -> round 4 builds plans inside Unreal.

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

Tools/BuildVoxelForgeCoreHost.ps1

@@ -130,11 +130,11 @@ $buildSucceeded = $false
 for ($attempt = 1; $attempt -le 2 -and -not $buildSucceeded; ++$attempt) {
     $attemptStdout = if ($attempt -eq 1) { $BuildStdout } else { Join-Path $LogRoot 'UBT-CoreIntegration.retry.stdout.log' }
     $attemptStderr = if ($attempt -eq 1) { $BuildStderr } else { Join-Path $LogRoot 'UBT-CoreIntegration.retry.stderr.log' }
-    Write-Host "BuildHost UBT attempt $attempt of 2; max parallel actions=$MaxParallelActions; normal priority."
+    Write-Host "BuildHost UBT attempt $attempt of 2; max parallel actions=$MaxParallelActions; BelowNormal priority."
     $process = Start-Process -FilePath $dotnet -ArgumentList $argumentList -WorkingDirectory $PluginRoot `
         -RedirectStandardOutput $attemptStdout -RedirectStandardError $attemptStderr `
         -WindowStyle Hidden -PassThru
-    $process.PriorityClass = [Diagnostics.ProcessPriorityClass]::Normal
+    $process.PriorityClass = [Diagnostics.ProcessPriorityClass]::BelowNormal
     $started = [datetime]::UtcNow
     while (-not $process.HasExited) {
         Start-Sleep -Seconds 5

Tools/TestVoxelForgeCoreWorldHost.ps1

@@ -5,7 +5,8 @@ param(
     [ValidateSet('MarchingCubesV1', 'WorldAssemblerHybridV1', 'WorldAssemblerHybridV2')][string]$CoreMesherRecipe = 'MarchingCubesV1',
     [switch]$EnableHybridFixturePlacement,
     [switch]$HybridCliffOnly,
-    [switch]$HybridFixturesOnly
+    [switch]$HybridFixturesOnly,
+    [switch]$FloatingIslandsOnly
 )
 
 # Exercise AVoxelWorld Core streaming, collision, anchor movement, and carving in BuildHost only.
@@ -41,7 +42,11 @@ function Assert-UnderPath([string]$Candidate, [string]$Root) {
 Assert-UnderPath $HostRoot (Join-Path $PluginRoot 'Saved\BuildHost')
 Assert-UnderPath $OutputRoot (Join-Path $StagePlugin 'Saved')
 if ([string]::IsNullOrWhiteSpace($WorldAssemblyManifestPath)) {
-    $WorldAssemblyManifestPath = Join-Path $PluginRoot 'Standalone\Research\WorldAssemblerM1\round4\world_assembly.json'
+    $WorldAssemblyManifestPath = if ($FloatingIslandsOnly) {
+        Join-Path $PluginRoot 'Standalone\Research\WorldAssemblerM3\Round3\results\world_assembly_floating_islands.json'
+    } else {
+        Join-Path $PluginRoot 'Standalone\Research\WorldAssemblerM1\round4\world_assembly.json'
+    }
 }
 $WorldAssemblyManifestPath = [IO.Path]::GetFullPath($WorldAssemblyManifestPath)
 Assert-UnderPath $WorldAssemblyManifestPath $PluginRoot
@@ -84,7 +89,13 @@ foreach ($directory in @($OutputDirectory, $InputDirectory, $LogDirectory, $Loca
 }
 Copy-Item -LiteralPath $WorldAssemblyManifestPath -Destination $StagedWorldAssembly -Force
 $ManifestData = Get-Content -LiteralPath $StagedWorldAssembly -Raw | ConvertFrom-Json
-if ($ManifestData.content_hash -ne '8933693d9560ba9f') {
+if ($FloatingIslandsOnly) {
+    if ($ManifestData.content_hash -ne '94b563f1ce622def' -or
+        @($ManifestData.floating_islands).Count -ne 1 -or
+        @($ManifestData.plan.strates).Count -ne 0) {
+        throw "BuildHost world assembly input is not the reviewed round-3 island manifest: $($ManifestData.content_hash)"
+    }
+} elseif ($ManifestData.content_hash -ne '8933693d9560ba9f') {
     throw "BuildHost world assembly input is not the reviewed round-4 manifest: $($ManifestData.content_hash)"
 }
 if ($EnableHybridFixturePlacement -and $CoreMesherRecipe -eq 'MarchingCubesV1') {
@@ -102,6 +113,10 @@ if ($HybridFixturesOnly -and $CoreMesherRecipe -eq 'MarchingCubesV1') {
 if ($HybridFixturesOnly -and ($HybridCliffOnly -or $EnableHybridFixturePlacement)) {
     throw '-HybridFixturesOnly cannot be combined with the other focused hybrid modes.'
 }
+if ($FloatingIslandsOnly -and ($CoreMesherRecipe -ne 'MarchingCubesV1' -or
+    $EnableHybridFixturePlacement -or $HybridCliffOnly -or $HybridFixturesOnly)) {
+    throw '-FloatingIslandsOnly uses the reviewed MC island manifest and cannot be combined with hybrid modes.'
+}
 
 $CrashBefore = @{}
 foreach ($CrashRoot in $CrashRoots) {
@@ -134,6 +149,7 @@ $HybridMesherFlag = switch ($CoreMesherRecipe) {
 $HybridFixturePlacementFlag = if ($EnableHybridFixturePlacement) { 1 } else { 0 }
 $HybridCliffOnlyFlag = if ($HybridCliffOnly) { 1 } else { 0 }
 $HybridFixturesOnlyFlag = if ($HybridFixturesOnly) { 1 } else { 0 }
+$FloatingIslandsOnlyFlag = if ($FloatingIslandsOnly) { 1 } else { 0 }
 $BaseArguments = @(
     ('-project="{0}"' -f $HostProject),
     '-nullrhi', '-unattended', '-nop4', '-nosplash', '-NoSound',
@@ -144,6 +160,7 @@ $BaseArguments = @(
     ('-LocalDataCachePath="{0}"' -f $DerivedDataCache),
     '-run=VoxelForgeExplore', '-seed=0', '-archetype=TunnelNetwork', '-slot=0',
     '-modes=export', '-gameconfig=1', '-coreworldtest=1',
+    ("-coreislandtest=$FloatingIslandsOnlyFlag"),
     '-settingsref=/Game/VoxelForge/DA_Settings.DA_Settings',
     ('-coreworldassembly="{0}"' -f $StagedWorldAssembly),
     ("-corehybridmesher=$HybridMesherFlag"),
@@ -152,6 +169,11 @@ $BaseArguments = @(
     ("-corehybridfixturesonly=$HybridFixturesOnlyFlag"),
     ('-out="{0}"' -f $OutputDirectory)
 )
+if ($FloatingIslandsOnly) {
+    # Keep this stationary route fixture out of the movement gate; island/span cooked contacts are probed directly.
+    # Garder ce fixture immobile hors du gate de mouvement ; les contacts cuisines ile/pont sont verifies directement.
+    $BaseArguments += '-voxel.CollisionGate=0'
+}
 
 $OldLocalAppData = $env:LOCALAPPDATA
 $env:LOCALAPPDATA = $LocalAppData
@@ -171,11 +193,11 @@ try {
         $StdoutPath = Join-Path $LogDirectory $StdoutFileName
         $StderrPath = Join-Path $LogDirectory $StderrFileName
         $Arguments = @($BaseArguments) + ('-abslog="{0}"' -f $LogPath)
-        Write-Host "BuildHost Core actor commandlet attempt $Attempt of 2; normal priority."
+        Write-Host "BuildHost Core actor commandlet attempt $Attempt of 2; BelowNormal priority."
         $Process = Start-Process -FilePath $EditorCmd -ArgumentList $Arguments -WorkingDirectory $HostRoot `
             -RedirectStandardOutput $StdoutPath -RedirectStandardError $StderrPath `
             -WindowStyle Hidden -PassThru
-        $Process.PriorityClass = [Diagnostics.ProcessPriorityClass]::Normal
+        $Process.PriorityClass = [Diagnostics.ProcessPriorityClass]::BelowNormal
         $StartedUtc = [datetime]::UtcNow
         $PeakPrivateBytes = [int64]0
         while (-not $Process.HasExited) {
@@ -198,7 +220,8 @@ try {
         $ExitCode = $Process.ExitCode
         if ([string]::IsNullOrEmpty([string]$ExitCode) -and (Test-Path -LiteralPath $LogPath -PathType Leaf)) {
             $CompletedLog = Get-Content -LiteralPath $LogPath -Raw
-            if ($CompletedLog -match '\[VoxelForgeCoreWorldTest\] pass complete=1' -and
+            if (($CompletedLog -match '\[VoxelForgeCoreWorldTest\] pass complete=1' -or
+                $CompletedLog -match '\[VoxelForgeCoreIslandTest\] pass complete=1') -and
                 $CompletedLog -match 'Commandlet VoxelForgeExploreCommandlet_\d+ finished execution \(result 0\)') {
                 $ExitCode = 0
             } elseif ($CompletedLog -match 'Commandlet VoxelForgeExploreCommandlet_\d+ finished execution \(result (-?\d+)\)') {
@@ -230,6 +253,44 @@ if (-not (Test-Path -LiteralPath $FinalLog -PathType Leaf)) {
     $FinalLog = Join-Path $LogDirectory 'CoreWorldValidation.retry.log'
 }
 $Text = Get-Content -LiteralPath $FinalLog -Raw
+if ($FloatingIslandsOnly) {
+    foreach ($Marker in @(
+        '[VoxelForgeCoreIslandTest] manifest_import=PASS',
+        '[VoxelForgeCoreIslandTest] standalone_reference=PASS',
+        '[VoxelForgeCoreIslandTest] worker_hash_matrix=1/8/16 stable=1',
+        '[VoxelForgeCoreIslandTest] pass phase=initial',
+        '[VoxelForgeCoreIslandTest] height_anchor_agreement=PASS',
+        '[VoxelForgeCoreIslandTest] content_anchor=PASS',
+        '[VoxelForgeCoreIslandTest] blueprint_edit=PASS',
+        '[VoxelForgeCoreIslandTest] switch_off_legacy=PASS',
+        '[VoxelForgeCoreIslandTest] pass complete=1',
+        '[VoxelForgePawnSpeedFixture] source=staged_blueprints walk_cm_s=600.000 sprint_cm_s=6000.000'
+    )) {
+        if ($Text.IndexOf($Marker, [StringComparison]::Ordinal) -lt 0) {
+            throw "BuildHost floating-island log is missing '$Marker'. See $FinalLog."
+        }
+    }
+    foreach ($Surface in @('island_top', 'span')) {
+        if ($Text -notmatch ('\[VoxelForgeCoreIslandTest\] capsule_contact=PASS surface=' +
+            [regex]::Escape($Surface) + ' .*collision_ready=1')) {
+            throw "BuildHost island log is missing cooked capsule contact for '$Surface'. See $FinalLog."
+        }
+    }
+    foreach ($Lod in @(0, 1)) {
+        if ($Text -notmatch ('\[VoxelForgeIslandStreaming\] timing lod=' + $Lod + ' kind=.*air .*core_p95_ms=') -or
+            $Text -notmatch ('\[VoxelForgeIslandStreaming\] timing lod=' + $Lod + ' kind=.*(island|mixed|span) .*legacy_p95_ms=')) {
+            throw "BuildHost island log is missing matched air and surface timing at LOD$Lod. See $FinalLog."
+        }
+    }
+    $NewCrashes = @(Get-NewCrashFolders)
+    if ($NewCrashes.Count -gt 0) {
+        throw "New UECC crash folders appeared during the island actor test: $($NewCrashes -join '; ')"
+    }
+    Write-Host "VOXELFORGE_CORE_FLOATING_ISLANDS_PASS manifest=$($ManifestData.content_hash) hashes=standalone water_fixed=1 lod=0,1 workers=1,8,16"
+    Write-Host "Core actor log: $FinalLog"
+    Write-Host "Peak commandlet private bytes sampled: $PeakPrivateBytes"
+    return
+}
 if ($HybridFixturesOnly) {
     foreach ($Fixture in @('corner90', 'doorway', 'riser1m', 'cliff_ledge', 'organic_cave_chamber')) {
         $FixtureMarker = '\[WorldAssemblerHybridPluginFixture\] name=' +