diff --git a/tools/connected-backend-differential.route.txt b/tools/connected-backend-differential.route.txt
new file mode 100644
index 00000000..dfb2e6ba
--- /dev/null
+++ b/tools/connected-backend-differential.route.txt
@@ -0,0 +1,77 @@
+# Campaign V slice V7: the connected route the GL-versus-Vulkan differential
+# runs TWICE, once per backend, pairing the PNGs by name.
+#
+# Two separate launches have to agree pixel-for-pixel, which is a much stricter
+# requirement than either connected route was written for. Everything below is
+# in service of that:
+#
+#   * Every teleloc carries the identity quaternion, so the heading at each stop
+#     is the same on both runs rather than whatever the previous heading was.
+#   * The world clock is pinned by the client-only time-of-day override
+#     (AcdreamCycleTimeOfDay cycles live -> 0.00 -> 0.25 -> 0.50, so three
+#     presses land on noon). Without it the sky gradient, the sun angle and
+#     every lit surface drift with wall time between the two launches, which is
+#     the same effect that makes the offline gate mask its top 280 rows.
+#   * Nothing moves the character. The only thing between arrival and capture is
+#     a settle window, because a timed turn cannot be relied on to stop at the
+#     same angle twice.
+#   * There is no `checkpoint` verb here. The differential's verdict is the
+#     paired PNG, and the ownership ledger has its own gate
+#     (run-connected-world-lifecycle-gate.ps1) that this route does not duplicate.
+#
+# MSAA is forced OFF by the gate script rather than here, on BOTH launches.
+# Sample positions are not specified across implementations and cost 8.8% of the
+# frame at 4x -- measured, plan section 5.5.16 -- so a differential run with MSAA
+# on measures the two drivers' sample patterns and nothing else.
+#
+# Residual divergence this route cannot remove, and which is a finding rather
+# than a failure: PHASE. Two launches cannot agree on an emitter's age, a
+# creature's animation cursor, a portal's scrolling texture, or the cloud
+# sheet's position -- the cloud sheet in particular advances with WALL time and
+# not with the Dereth clock the override above pins, which is why the offline
+# pixel gate masks its own top 280 rows. The V6m smoke run measured the shape
+# of it at stop 1 with MSAA off: 18.52% of the frame differed, 89% of that in
+# the top 240 rows (cloud sheet, treeline, the portal), and rows 300-720 --
+# terrain, blending, roads, buildings, character, entire retained UI --
+# contributed about 9,500 pixels between them, almost all of it thin outlines
+# on silhouette edges. That is why every stop below is chosen for its static
+# content and why the settle windows are long.
+
+wait world-ready 90000
+wait world-visible 30000
+sleep 8000
+input press AcdreamCycleTimeOfDay
+input press AcdreamCycleTimeOfDay
+input press AcdreamCycleTimeOfDay
+sleep 5000
+
+# 1. Holtburg: the dense outdoor town. Terrain, terrain blending, the road
+#    overlay, static world meshes, scenery and the whole retained UI in one
+#    frame. This is the SMOKE stop -- the one pair -Smoke compares on its own.
+command /teleloc 0xA9B40019 84.0 7.1 94.005 1 0 0 0
+wait materialized 1 90000
+wait world-visible 30000
+sleep 25000
+screenshot holtburg_town 15000
+
+# 2. Facility Hub: an interior EnvCell, and the durable fix for the campaign's
+#    oldest coverage gap. Plan section 5.1 records that the offline gate sees no
+#    EnvCell at all and that EnvCellRenderer's Vulkan arm is proven by one
+#    eyes-on frame; this stop is the first automated instrument that looks at
+#    one. Cell 0x164 is >= 0x100, which is what makes it indoor: walls, floor,
+#    per-cell lighting and the doorway clip region rather than terrain.
+command /teleloc 0x8A020164 70.35 -40.66 -5.9 1 0 0 0
+wait materialized 2 90000
+wait world-visible 30000
+sleep 25000
+screenshot facility_hub_interior 15000
+
+# 3. Aerlinthe: dense island geometry, the water edge and a long view. The
+#    stop that exercises fog and the far end of the depth range, where a
+#    precision divergence between the two backends would show first.
+command /teleloc 0x09040008 11.4 188.6 87.705 1 0 0 0
+wait materialized 3 90000
+wait world-visible 30000
+sleep 25000
+screenshot aerlinthe_island 15000
+sleep 3000
diff --git a/tools/run-backend-differential-gate.ps1 b/tools/run-backend-differential-gate.ps1
new file mode 100644
index 00000000..00a3682d
--- /dev/null
+++ b/tools/run-backend-differential-gate.ps1
@@ -0,0 +1,380 @@
+<#
+.SYNOPSIS
+    Campaign V slice V7 instrument: the GL-versus-Vulkan connected differential.
+
+.DESCRIPTION
+    Runs the SAME connected route twice against the local ACE server -- once with
+    ACDREAM_RENDER_BACKEND=gl, once with =vulkan -- pairs the screenshots by name,
+    compares each pair with the `compare-screenshots` CLI at the plan's pinned
+    tolerance, and prints one verdict table.
+
+    This is the instrument for plan section 2's pixel-acceptance contract:
+
+        compare-screenshots expected.png actual.png out.json
+            channel tolerance 2, maximum differing fraction 0.001,
+            MSAA off, ACDREAM_DAY_GROUP pinned,
+            at every deterministic checkpoint of the connected route.
+
+    THREE THINGS ARE FORCED, and each is load-bearing.
+
+    1.  ACDREAM_MSAA_SAMPLES=0 ON BOTH LAUNCHES. Multisample resolve positions
+        are explicitly unspecified across implementations. Plan section 5.5.16
+        MEASURED what leaving them on costs: 8.83% of the frame differed at 4x,
+        81,359 pixels of 921,600, essentially all of it hugging foliage and
+        silhouette edges. That is two drivers' sample patterns, not a renderer
+        divergence, and it swamps the 0.001 threshold by ninety-fold. Forcing it
+        off on both runs is what makes the remaining difference attributable.
+        Note that it must be forced on BOTH -- matching a GL run at 4x against a
+        Vulkan run at 0 would be worse than either.
+
+    2.  ACDREAM_DAY_GROUP pinned. The sky animates and the Dereth clock advances
+        with wall time; two launches minutes apart cannot agree about either.
+        The route additionally pins the client-only time-of-day override.
+
+    3.  A DESKTOP WITNESS per run, with the guards the repeat-run gate
+        (run-repeat-connected-gate.ps1) learned the hard way. The client's own
+        capture is the differential's subject, but a blank frame reads back as a
+        valid PNG (plan section 5.5.2), so a second instrument that shares
+        nothing with the renderer decides whether the run is worth comparing at
+        all. Its failure modes are the same three that gate documents:
+
+          * an overlapping window or a locked screen -- CopyFromScreen grabs
+            whatever is composited at those coordinates, so run this with
+            nothing else on the primary monitor and the desktop unlocked;
+          * stray input -- a foregrounded window takes keystrokes and scrolls,
+            which moves the camera off the pinned stop and produces an enormous
+            spurious difference. The client log is scanned for camera-affecting
+            input afterwards and the run is aborted if any arrived;
+          * a hard kill -- ACE holds the session about three minutes and the
+            SECOND launch of this gate is the one that pays for it, so both runs
+            close through WM_CLOSE.
+
+.PARAMETER Out
+    Directory for both captures, the comparison reports and the verdict JSON.
+
+.PARAMETER Route
+    The route both backends run. Defaults to the differential route, which is
+    written for two-launch determinism -- see its header before substituting one.
+
+.PARAMETER Smoke
+    Compare only the FIRST stop. The route is truncated after its first
+    `screenshot` verb, so the run is short and the artifact records exactly what
+    ran. Use this to measure the distance between the backends without paying
+    for the whole route; the full route is the V7 gate.
+
+.PARAMETER Tolerance
+    Per-channel absolute difference allowed. Default 2, the plan's pinned value.
+
+.PARAMETER MaxDifferentFraction
+    Fraction of differing pixels allowed. Default 0.001, likewise pinned.
+
+.PARAMETER DayGroup
+    Sky day-group index pinned on both launches. Default 0.
+
+.PARAMETER MaskTopPixels
+    Height in pixels of a top band excluded from every comparison. DEFAULT 0 --
+    nothing is masked, and the gate is a strict identity check on the whole
+    frame.
+
+    It exists because the V6m smoke run measured what the band costs and the
+    number belongs where the next reader will find it. With the world clock
+    pinned by the route and MSAA off, a GL-versus-Vulkan pair at Holtburg
+    differed in 18.52% of the frame -- and 89% of that difference sat in the top
+    240 rows, which is the scrolling cloud sheet plus the treeline it sits
+    behind. The cloud sheet advances with WALL time, not the Dereth clock, so
+    two launches minutes apart can never agree there; this is the same
+    population the offline pixel gate masks its top 280 rows for. Rows 300-720
+    -- terrain, blending, roads, buildings, the character and the whole retained
+    UI -- contributed about 9,500 differing pixels between them.
+
+    Whether V7 accepts a mask, pins the cloud phase, or fixes something the
+    smoke was actually seeing is V7's decision, not this script's, which is why
+    the default is off. Do NOT reach for this to make a failing gate pass: plan
+    section 7.1 rule 2.
+
+.PARAMETER MinRenderedBytes
+    Desktop-grab PNG size below which a run is called blank and the comparison
+    is refused. Default 500000, the repeat gate's measured separator.
+
+.PARAMETER CooldownSeconds
+    Wait between the two launches so ACE clears the first graceful logout.
+    Default 15.
+
+.EXAMPLE
+    tools/run-backend-differential-gate.ps1 -Out artifacts/v7-differential -Smoke
+    tools/run-backend-differential-gate.ps1 -Out artifacts/v7-differential
+#>
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory = $true)][string]$Out,
+    [string]$Route,
+    [switch]$Smoke,
+    [int]$Tolerance = 2,
+    [double]$MaxDifferentFraction = 0.001,
+    [int]$DayGroup = 0,
+    [int]$MaskTopPixels = 0,
+    [int]$MinRenderedBytes = 500000,
+    [int]$CooldownSeconds = 15,
+    [int]$RouteTimeoutSeconds = 600,
+    [switch]$SkipBuild
+)
+
+$ErrorActionPreference = 'Stop'
+$repo = Split-Path -Parent $PSScriptRoot
+$exe = Join-Path $repo 'src\AcDream.App\bin\Release\net10.0\AcDream.App.exe'
+$cli = Join-Path $repo 'src\AcDream.Cli\bin\Release\net10.0\AcDream.Cli.dll'
+if (-not $Route) { $Route = Join-Path $repo 'tools\connected-backend-differential.route.txt' }
+
+function Write-Step($message) { Write-Host "[differential] $message" }
+
+# --- Preconditions ------------------------------------------------------------
+if (Get-Process -Name AcDream.App -ErrorAction SilentlyContinue) {
+    throw 'AcDream.App is already running. This gate uses the shared test account and must not steal its session.'
+}
+if (@(Get-NetUDPEndpoint -LocalPort 9000 -ErrorAction SilentlyContinue).Count -eq 0) {
+    throw 'local ACE is not listening on UDP port 9000.'
+}
+if (-not (Test-Path $Route)) { throw "Route not found: $Route" }
+
+if (-not $SkipBuild) {
+    Write-Step 'building Release'
+    & dotnet build (Join-Path $repo 'AcDream.slnx') -c Release --nologo -v q | Out-Null
+    if ($LASTEXITCODE -ne 0) { throw "Release build failed with exit code $LASTEXITCODE." }
+}
+if (-not (Test-Path $exe)) { throw "Client not found at $exe." }
+if (-not (Test-Path $cli)) { throw "AcDream.Cli not found at $cli." }
+
+if (Test-Path $Out) { Remove-Item -Recurse -Force $Out }
+New-Item -ItemType Directory -Force -Path $Out | Out-Null
+
+# The route both runs execute. -Smoke truncates after the first capture; the
+# truncated file is written into the artifact directory so what ran is on record.
+$routeLines = Get-Content -LiteralPath $Route
+if ($Smoke) {
+    $firstShot = -1
+    for ($i = 0; $i -lt $routeLines.Count; $i++) {
+        if ($routeLines[$i].TrimStart().StartsWith('screenshot ')) { $firstShot = $i; break }
+    }
+    if ($firstShot -lt 0) { throw "The route has no screenshot verb to truncate at: $Route" }
+    $routeLines = @($routeLines[0..$firstShot]) + @('sleep 3000')
+    Write-Step "smoke mode: route truncated after its first capture ($($firstShot + 1) lines)"
+}
+$effectiveRoute = Join-Path $Out 'route.txt'
+Set-Content -Encoding utf8 -Path $effectiveRoute -Value $routeLines
+
+Add-Type -AssemblyName System.Drawing
+Add-Type @'
+using System;
+using System.Runtime.InteropServices;
+public static class DifferentialGateSurface {
+    [DllImport("user32.dll")] public static extern bool SetForegroundWindow(IntPtr hWnd);
+    [DllImport("user32.dll")] public static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
+    [DllImport("user32.dll")] public static extern bool GetClientRect(IntPtr hWnd, out RECT r);
+    [DllImport("user32.dll")] public static extern bool ClientToScreen(IntPtr hWnd, ref POINT p);
+    [StructLayout(LayoutKind.Sequential)] public struct RECT { public int L, T, R, B; }
+    [StructLayout(LayoutKind.Sequential)] public struct POINT { public int X, Y; }
+}
+'@
+
+function Invoke-BackendRun([string]$Backend) {
+    $dir = Join-Path $Out $Backend
+    New-Item -ItemType Directory -Force -Path $dir | Out-Null
+    $log = Join-Path $dir 'client.log'
+    $grab = Join-Path $dir 'desktop-grab.png'
+
+    $env:ACDREAM_DAT_DIR = Join-Path $env:USERPROFILE "Documents\Asheron's Call"
+    $env:ACDREAM_LIVE = '1'
+    $env:ACDREAM_TEST_HOST = '127.0.0.1'
+    $env:ACDREAM_TEST_PORT = '9000'
+    $env:ACDREAM_TEST_USER = 'testaccount'
+    $env:ACDREAM_TEST_PASS = 'testpassword'
+    $env:ACDREAM_RETAIL_UI = '1'
+    $env:ACDREAM_DEVTOOLS = '0'
+    $env:ACDREAM_DAY_GROUP = "$DayGroup"
+    # Both launches, always. See the .DESCRIPTION note 1.
+    $env:ACDREAM_MSAA_SAMPLES = '0'
+    $env:ACDREAM_RENDER_BACKEND = $Backend
+    $env:ACDREAM_UI_PROBE_SCRIPT = $effectiveRoute
+    $env:ACDREAM_AUTOMATION_ARTIFACT_DIR = $dir
+
+    Write-Step "launching $Backend (MSAA off, day group $DayGroup)"
+    # Normal window style: the desktop witness needs a composited frame.
+    $proc = Start-Process -FilePath $exe -WorkingDirectory $repo `
+        -RedirectStandardOutput $log -RedirectStandardError "$log.err" -PassThru
+
+    $completed = $false
+    $deadline = (Get-Date).AddSeconds($RouteTimeoutSeconds)
+    while ((Get-Date) -lt $deadline) {
+        if (Select-String -Path $log -SimpleMatch '[UI-PROBE] UI probe script complete' `
+                -ErrorAction SilentlyContinue) { $completed = $true; break }
+        if ($proc.HasExited) { break }
+        Start-Sleep -Milliseconds 1000
+    }
+
+    # The desktop witness, taken while the client is still in its trailing sleep
+    # and therefore still rendering the last scene of the route.
+    $grabBytes = 0
+    if (-not $proc.HasExited) {
+        try {
+            $proc.Refresh()
+            $h = $proc.MainWindowHandle
+            if ($h -ne [IntPtr]::Zero) {
+                [DifferentialGateSurface]::ShowWindow($h, 9) | Out-Null   # SW_RESTORE
+                [DifferentialGateSurface]::SetForegroundWindow($h) | Out-Null
+                Start-Sleep -Milliseconds 1200
+                $r = New-Object DifferentialGateSurface+RECT
+                [DifferentialGateSurface]::GetClientRect($h, [ref]$r) | Out-Null
+                $p = New-Object DifferentialGateSurface+POINT
+                [DifferentialGateSurface]::ClientToScreen($h, [ref]$p) | Out-Null
+                $w = $r.R - $r.L; $ht = $r.B - $r.T
+                if ($w -gt 0 -and $ht -gt 0) {
+                    $bmp = New-Object System.Drawing.Bitmap $w, $ht
+                    $g = [System.Drawing.Graphics]::FromImage($bmp)
+                    $g.CopyFromScreen($p.X, $p.Y, 0, 0, (New-Object System.Drawing.Size $w, $ht))
+                    $bmp.Save($grab, [System.Drawing.Imaging.ImageFormat]::Png)
+                    $g.Dispose(); $bmp.Dispose()
+                    $grabBytes = (Get-Item $grab).Length
+                }
+            }
+        }
+        catch { Write-Step "desktop grab failed on ${Backend}: $_" }
+    }
+
+    # Graceful close, always: a hard kill leaves ACE holding the session about
+    # three minutes, and the second launch is the one that would pay for it.
+    $app = Get-Process -Name AcDream.App -ErrorAction SilentlyContinue
+    if ($app) {
+        $app.CloseMainWindow() | Out-Null
+        if (-not $app.WaitForExit(20000)) {
+            Write-Step "WM_CLOSE timed out on $Backend; forcing"
+            $app | Stop-Process -Force
+        }
+    }
+
+    Remove-Item Env:\ACDREAM_RENDER_BACKEND -ErrorAction SilentlyContinue
+    Remove-Item Env:\ACDREAM_MSAA_SAMPLES -ErrorAction SilentlyContinue
+
+    $strayInput = @(Select-String -Path $log -Pattern 'ScrollUp|ScrollDown|ZoomIn|ZoomOut|CameraZoom' `
+        -CaseSensitive -ErrorAction SilentlyContinue)
+    $witness = if ($grabBytes -ge $MinRenderedBytes) { 'RENDERED' }
+               elseif ($grabBytes -gt 0) { 'BLANK' }
+               else { 'NO-CAPTURE' }
+
+    return [pscustomobject][ordered]@{
+        Backend = $Backend
+        RouteCompleted = $completed
+        GrabBytes = $grabBytes
+        Witness = $witness
+        StrayInputLines = @($strayInput | Select-Object -First 5 | ForEach-Object { $_.Line })
+        Screenshots = Join-Path $dir 'screenshots'
+        Log = $log
+    }
+}
+
+$gl = Invoke-BackendRun 'gl'
+Write-Step "cooldown ${CooldownSeconds}s so ACE clears the graceful logout"
+Start-Sleep -Seconds $CooldownSeconds
+$vk = Invoke-BackendRun 'vulkan'
+
+# --- Sanity, before any pixel is compared ------------------------------------
+$aborts = @()
+foreach ($run in @($gl, $vk)) {
+    if (-not $run.RouteCompleted) { $aborts += "$($run.Backend): the route did not complete" }
+    if ($run.Witness -ne 'RENDERED') {
+        $aborts += "$($run.Backend): desktop witness says $($run.Witness) ($($run.GrabBytes) B) -- locked screen, an overlapping window, or a blank frame"
+    }
+    if ($run.StrayInputLines.Count -gt 0) {
+        $aborts += "$($run.Backend): camera-affecting input reached the window; the capture is not comparable"
+    }
+}
+
+$pairs = @()
+if ($aborts.Count -eq 0) {
+    $glShots = @(Get-ChildItem $gl.Screenshots -Filter *.png -ErrorAction SilentlyContinue)
+    if ($glShots.Count -eq 0) { $aborts += 'gl: no screenshots were captured' }
+
+    # The comparer skips any pixel whose mask alpha is non-zero, so the excluded
+    # band is opaque and everything compared is transparent. Same construction as
+    # the offline pixel gate's sky mask; off unless -MaskTopPixels was given.
+    $maskPath = $null
+    if ($MaskTopPixels -gt 0 -and $glShots.Count -gt 0) {
+        $probeImage = [System.Drawing.Bitmap]::FromFile($glShots[0].FullName)
+        $mw = $probeImage.Width; $mh = $probeImage.Height
+        $probeImage.Dispose()
+        $mask = New-Object System.Drawing.Bitmap($mw, $mh, [System.Drawing.Imaging.PixelFormat]::Format32bppArgb)
+        $graphics = [System.Drawing.Graphics]::FromImage($mask)
+        $graphics.Clear([System.Drawing.Color]::FromArgb(0, 0, 0, 0))
+        $opaque = New-Object System.Drawing.SolidBrush ([System.Drawing.Color]::FromArgb(255, 255, 0, 255))
+        $graphics.FillRectangle($opaque, 0, 0, $mw, [Math]::Min($MaskTopPixels, $mh))
+        $graphics.Dispose(); $opaque.Dispose()
+        $maskPath = Join-Path $Out 'mask.png'
+        $mask.Save($maskPath, [System.Drawing.Imaging.ImageFormat]::Png)
+        $mask.Dispose()
+        Write-Step "masking the top $MaskTopPixels rows of every pair"
+    }
+
+    foreach ($shot in $glShots) {
+        $counterpart = Join-Path $vk.Screenshots $shot.Name
+        if (-not (Test-Path $counterpart)) {
+            $pairs += [pscustomobject][ordered]@{
+                Stop = $shot.BaseName; Verdict = 'UNPAIRED'
+                DifferentPixels = $null; Fraction = $null; MaxChannelDelta = $null
+            }
+            continue
+        }
+        $report = Join-Path $Out "compare-$($shot.BaseName).json"
+        if ($maskPath) {
+            & dotnet $cli compare-screenshots $shot.FullName $counterpart $report $Tolerance $MaxDifferentFraction $maskPath | Out-Null
+        }
+        else {
+            & dotnet $cli compare-screenshots $shot.FullName $counterpart $report $Tolerance $MaxDifferentFraction | Out-Null
+        }
+        $verdict = Get-Content $report -Raw | ConvertFrom-Json
+        $outcome = if ($verdict.passed) { 'MATCH' } else { 'DIVERGED' }
+        $pairs += [pscustomobject][ordered]@{
+            Stop = $shot.BaseName
+            Verdict = $outcome
+            DifferentPixels = $verdict.differentPixels
+            Fraction = $verdict.differentPixelFraction
+            MaxChannelDelta = $verdict.maximumChannelDelta
+        }
+    }
+}
+
+# --- Verdict ------------------------------------------------------------------
+Write-Host ''
+if ($aborts.Count -gt 0) {
+    Write-Host '[differential] ABORTED before comparison:' -ForegroundColor Red
+    $aborts | ForEach-Object { Write-Host "  - $_" -ForegroundColor Red }
+}
+else {
+    $pairs | Format-Table -AutoSize | Out-String | Write-Host
+}
+
+$diverged = @($pairs | Where-Object Verdict -ne 'MATCH')
+$report = [pscustomobject][ordered]@{
+    Passed = ($aborts.Count -eq 0 -and $diverged.Count -eq 0)
+    Smoke = [bool]$Smoke
+    Commit = (& git -C $repo rev-parse HEAD).Trim()
+    Route = $Route
+    EffectiveRoute = $effectiveRoute
+    ChannelTolerance = $Tolerance
+    MaxDifferentPixelFraction = $MaxDifferentFraction
+    MsaaSamples = 0
+    DayGroup = $DayGroup
+    MaskTopPixels = $MaskTopPixels
+    Runs = @($gl, $vk)
+    Pairs = @($pairs)
+    Aborts = @($aborts)
+}
+$reportPath = Join-Path $Out 'differential.json'
+$report | ConvertTo-Json -Depth 8 | Set-Content -LiteralPath $reportPath -Encoding utf8
+Write-Step "report: $reportPath"
+
+if ($aborts.Count -gt 0) { exit 2 }
+if ($diverged.Count -gt 0) {
+    Write-Host ("[differential] FAILED: {0}/{1} stop(s) diverged." -f $diverged.Count, $pairs.Count) -ForegroundColor Red
+    exit 1
+}
+Write-Step ("PASS: {0}/{0} stop(s) match at tolerance {1} / fraction {2}." -f $pairs.Count, $Tolerance, $MaxDifferentFraction)
+exit 0