diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dc3266c..ad9e6da 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -40,6 +40,14 @@ jobs:
       - name: Installer detection regression checks
         shell: pwsh
         run: ./installer/checks/Test-Detection.ps1
+      - name: Release Defender activation contract checks (isolated mocks)
+        shell: pwsh
+        run: ./scripts/checks/Test-ReleaseDefender.ps1
+      - name: Verify Defender activation on hosted runner
+        shell: pwsh
+        run: |
+          ./scripts/Enable-ReleaseDefender.ps1
+          ./scripts/Check-ReleaseArtifacts.ps1 -Paths @('ClaudeRevit/bin/Release/release/ClaudeRevit.dll') -ReportPath defender-ci.json -SourceCommit '${{ github.sha }}'
       - name: Upload Revit 2027 build
         uses: actions/upload-artifact@v4
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 37c26cb..70f81c1 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -116,7 +116,7 @@ jobs:
       - name: Scan release payloads and final packages
         shell: pwsh
         run: |
-          Update-MpSignature -ErrorAction Stop
+          ./scripts/Enable-ReleaseDefender.ps1
           $targets = @((Resolve-Path 'installer/payload').Path)
           $targets += Get-ChildItem "ClaudeRevit-${{ steps.vars.outputs.version }}-Revit*.zip" | ForEach-Object FullName
           $targets += '${{ steps.installer.outputs.path }}'
diff --git a/README.md b/README.md
index e54a86a..9520434 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ MCP agents: choose **Claude Code · MCP** or **Codex · MCP**, then select a mod
 and reasoning effort. Choices are saved independently. Codex reads its model
 catalog from the installed CLI. See [agent selection and setup](docs/openai-codex.md).
 
-**v3.8.4:** mandatory objective benchmark checks, repeated-run calibration, channel/angle/tube/paired-timber sections, dependent nodes and actual bore checks, multicategory live SPDS sources, optional verified experience and saved resumable jobs. Seven generated sections, shared nesting, checkpoint recovery, dependent nodes, live steel/timber quantities and eight BIMStarter references have now been exercised in Revit. [Executed results and limits](docs/native-acceptance-2026-10.md) · [Release notes](docs/releases/v3.8.4.md) · [BIMStarter findings](docs/bimstarter-reference-cases.md).
+**v3.8.5:** mandatory objective benchmark checks, repeated-run calibration, channel/angle/tube/paired-timber sections, dependent nodes and actual bore checks, multicategory live SPDS sources, optional verified experience and saved resumable jobs. Seven generated sections, shared nesting, checkpoint recovery, dependent nodes, live steel/timber quantities and eight BIMStarter references have now been exercised in Revit. Includes the release-runner Defender activation fix after v3.8.4 publication was blocked. [Executed results and limits](docs/native-acceptance-2026-10.md) · [Release notes](docs/releases/v3.8.5.md) · [BIMStarter findings](docs/bimstarter-reference-cases.md).
 
 **v3.8.3:** live SPDS steel/timber schedules, native steel connection inspection, persistent keyed nodes and geometry-driving parametric sections with independent flex checks. Instance values survive type changes; compiler/worker failures and timing are journaled. Code execution is always enabled, with no permission checkbox. [Structural workflows and limits](docs/structural-workflows.md) · [Release notes](docs/releases/v3.8.3.md).
 
diff --git a/README.ru.md b/README.ru.md
index aa5f2a5..eaf0f5f 100644
--- a/README.ru.md
+++ b/README.ru.md
@@ -6,7 +6,7 @@
 глубину рассуждений. Настройки агентов сохраняются отдельно; Codex получает
 список моделей из установленного CLI. [Выбор агента и настройка](docs/openai-codex.md).
 
-**v3.8.4:** обязательные объективные проверки бенчмарка, повторы и калибровка времени, швеллер/уголок/труба/парное деревянное сечение, зависимости узлов и проверка реальных отверстий, живые таблицы нескольких категорий, необязательный проверенный опыт и возобновляемые задания. В Revit проверены семь созданных сечений, вложенность, восстановление заданий, зависимости узлов, обновление стальных/деревянных таблиц и восемь семейств BIMStarter. [Результаты и ограничения](docs/native-acceptance-2026-10.md) · [Изменения](docs/releases/v3.8.4.md) · [Разбор семейств BIMStarter](docs/bimstarter-reference-cases.md).
+**v3.8.5:** обязательные объективные проверки бенчмарка, повторы и калибровка времени, швеллер/уголок/труба/парное деревянное сечение, зависимости узлов и проверка реальных отверстий, живые таблицы нескольких категорий, необязательный проверенный опыт и возобновляемые задания. В Revit проверены семь созданных сечений, вложенность, восстановление заданий, зависимости узлов, обновление стальных/деревянных таблиц и восемь семейств BIMStarter. Добавлено включение Defender на сервере сборки: публикация v3.8.4 была остановлена проверкой безопасности. [Результаты и ограничения](docs/native-acceptance-2026-10.md) · [Изменения](docs/releases/v3.8.5.md) · [Разбор семейств BIMStarter](docs/bimstarter-reference-cases.md).
 
 **v3.8.3:** живые спецификации СПДС для стали и дерева, проверка загруженных нативных стальных соединений, сохраняемые узлы с адресным обновлением и параметрические сечения с независимыми flex-проверками. Параметры экземпляра сохраняются при смене типа; журнал отдельно учитывает компиляцию и её ошибки. Выполнение кода доступно всегда, переключатель разрешения удалён. [Инструменты и ограничения](docs/structural-workflows.md) · [Релиз](docs/releases/v3.8.3.md).
 
diff --git a/docs/installer-security.md b/docs/installer-security.md
index e491ef3..4ec376b 100644
--- a/docs/installer-security.md
+++ b/docs/installer-security.md
@@ -71,3 +71,12 @@ archive contents and exclusions are handled by the scanner without changing
 real-time protection or restoring files. See the
 [official command reference](https://learn.microsoft.com/en-us/defender-endpoint/command-line-arguments-microsoft-defender-antivirus).
 A passing scan is a time-specific result from one engine, not a safety guarantee.
+
+GitHub's [Windows image configuration](https://github.com/actions/runner-images/blob/main/images/windows/scripts/build/Configure-WindowsDefender.ps1)
+disables monitoring and can force passive mode. The first v3.8.4 release attempt
+built every package but failed closed at this gate; nothing was published.
+`Enable-ReleaseDefender.ps1` now activates protection only on a disposable hosted
+Windows runner, removes that image's two whole-drive exclusions and updates
+intelligence. It follows Microsoft's [always-on protection settings](https://learn.microsoft.com/en-us/defender-endpoint/configure-real-time-protection-microsoft-defender-antivirus).
+Developer-machine invocation is rejected. Activation failure still blocks release;
+the original scan gate is retained. Isolated contract tests mock all system calls.
diff --git a/docs/releases/v3.8.5.md b/docs/releases/v3.8.5.md
new file mode 100644
index 0000000..95290d5
--- /dev/null
+++ b/docs/releases/v3.8.5.md
@@ -0,0 +1,7 @@
+# v3.8.5 — verified modeling and checked release packaging
+
+Includes all [v3.8.4 modeling changes](https://github.com/debug23win/ClaudeRevit/blob/main/docs/releases/v3.8.4.md): objective benchmark evidence, repeated-run calibration, seven constrained section shapes, dependent nodes/bore inspection, live multicategory SPDS summaries, optional verified experience and saved checkpoint jobs. See [executed native results and limits](https://github.com/debug23win/ClaudeRevit/blob/main/docs/native-acceptance-2026-10.md).
+
+The v3.8.4 build completed, but publication was blocked because GitHub's Windows image had Defender inactive. This patch activates it only on the disposable hosted runner, removes its whole-drive exclusions, updates intelligence and retains the mandatory scan of payloads, final ZIPs and the exact installer. Activation, detection or scan failures still block release. No developer-computer security settings are changed.
+
+215 unit tests and WPF/MCP/subscription CLI/installer checks passed. Native Revit 2027 cases cover generated sections, shared nesting, recovery, dependent-node edits, bores, eight BIMStarter references and live steel/timber quantities. Reference visibility variants and generated structural-template placement remain bounded as described in the acceptance report. Steel summaries are separate live grouped schedules, not an exact single-table form 2 facsimile; agree formatting before issuing drawings.
diff --git a/scripts/Check-ReleaseArtifacts.ps1 b/scripts/Check-ReleaseArtifacts.ps1
index 1a7cada..b0eca43 100644
--- a/scripts/Check-ReleaseArtifacts.ps1
+++ b/scripts/Check-ReleaseArtifacts.ps1
@@ -7,9 +7,10 @@ param(
 # Fail closed. A successful scan is evidence from one engine at one time, not a
 # guarantee of safety. Do not add exclusions, restore quarantine or disable AV.
 $ErrorActionPreference = 'Stop'
-$report = [ordered]@{ source_commit = $SourceCommit; utc = [DateTime]::UtcNow.ToString('o'); status = 'incomplete'; engine = $null; files = @(); error = $null }
+$report = [ordered]@{ source_commit = $SourceCommit; utc = [DateTime]::UtcNow.ToString('o'); status = 'incomplete'; protection = $null; engine = $null; files = @(); error = $null }
 try {
     $status = Get-MpComputerStatus -ErrorAction Stop
+    $report.protection = @{ mode = $status.AMRunningMode; antivirus_enabled = [bool]$status.AntivirusEnabled; realtime_enabled = [bool]$status.RealTimeProtectionEnabled }
     if (-not $status.AntivirusEnabled -or -not $status.RealTimeProtectionEnabled) {
         throw 'Microsoft Defender must be active; release scanning cannot be skipped.'
     }
diff --git a/scripts/Enable-ReleaseDefender.ps1 b/scripts/Enable-ReleaseDefender.ps1
new file mode 100644
index 0000000..b2f66fc
--- /dev/null
+++ b/scripts/Enable-ReleaseDefender.ps1
@@ -0,0 +1,25 @@
+# GitHub's disposable Windows images disable monitoring and can force passive mode.
+# Strengthen that runner before packaging; never change a developer's AV settings.
+$ErrorActionPreference = 'Stop'
+if ($env:GITHUB_ACTIONS -ne 'true' -or $env:RUNNER_OS -ne 'Windows' -or $env:RUNNER_ENVIRONMENT -ne 'github-hosted') {
+    throw 'Defender activation is restricted to disposable GitHub-hosted Windows runners.'
+}
+$policy = 'HKLM:\SOFTWARE\Policies\Microsoft\Windows Advanced Threat Protection'
+if (Test-Path -LiteralPath $policy) {
+    Set-ItemProperty -LiteralPath $policy -Name ForceDefenderPassiveMode -Value 0 -Type DWord
+}
+Start-Service -Name WinDefend -ErrorAction Stop
+Set-MpPreference -DisableRealtimeMonitoring $false -DisableBehaviorMonitoring $false -DisableArchiveScanning $false -DisableScriptScanning $false -DisableIOAVProtection $false -ErrorAction Stop
+# Remove only the two whole-drive exclusions supplied by the runner image.
+$broadExclusions = @((Get-MpPreference).ExclusionPath | Where-Object { $_ -in @('C:\','D:\') })
+if ($broadExclusions.Count) { Remove-MpPreference -ExclusionPath $broadExclusions -ErrorAction Stop }
+Update-MpSignature -ErrorAction Stop
+for ($attempt = 0; $attempt -lt 12; $attempt++) {
+    $status = Get-MpComputerStatus -ErrorAction Stop
+    if ($status.AntivirusEnabled -and $status.RealTimeProtectionEnabled) {
+        $status | Select-Object AMRunningMode, AntivirusEnabled, RealTimeProtectionEnabled, AntivirusSignatureVersion
+        return
+    }
+    Start-Sleep -Seconds 2
+}
+throw 'Defender activation failed; release publication remains blocked.'
diff --git a/scripts/checks/Test-ReleaseDefender.ps1 b/scripts/checks/Test-ReleaseDefender.ps1
new file mode 100644
index 0000000..fdc7d52
--- /dev/null
+++ b/scripts/checks/Test-ReleaseDefender.ps1
@@ -0,0 +1,31 @@
+# Isolated contract checks: mocks never change AV, services, registry or network.
+$ErrorActionPreference = 'Stop'
+$activationScript = Join-Path $PSScriptRoot '..\Enable-ReleaseDefender.ps1'
+$original = @{}
+foreach ($name in @('GITHUB_ACTIONS','RUNNER_OS','RUNNER_ENVIRONMENT')) { $original[$name] = [Environment]::GetEnvironmentVariable($name) }
+function Assert($condition, $message) { if (-not $condition) { throw $message } }
+try {
+    $env:GITHUB_ACTIONS = 'false'
+    try { & $activationScript; throw 'Local invocation was allowed' }
+    catch { Assert ($_.Exception.Message -like '*restricted to disposable*') 'Local guard failed' }
+    $qaMock=@{}
+    function Test-Path { param($LiteralPath) return $true }
+    function Set-ItemProperty { param($LiteralPath,$Name,$Value,$Type) Assert ($Name -eq 'ForceDefenderPassiveMode' -and $Value -eq 0) 'Policy must enable active mode'; $qaMock.policyWrites++ }
+    function Start-Service { [CmdletBinding()]param($Name) Assert ($Name -eq 'WinDefend') 'Unexpected service'; $qaMock.serviceStarts++ }
+    function Set-MpPreference { [CmdletBinding()]param($DisableRealtimeMonitoring,$DisableBehaviorMonitoring,$DisableArchiveScanning,$DisableScriptScanning,$DisableIOAVProtection) Assert (-not ($DisableRealtimeMonitoring -or $DisableBehaviorMonitoring -or $DisableArchiveScanning -or $DisableScriptScanning -or $DisableIOAVProtection)) 'Protection was weakened'; $qaMock.preferenceWrites++ }
+    function Get-MpPreference { return @{ExclusionPath=@('C:\','D:\','C:\retained-example')} }
+    function Remove-MpPreference { [CmdletBinding()]param($ExclusionPath) Assert (($ExclusionPath -join ',') -eq 'C:\,D:\') 'Only runner whole-drive exclusions may be removed'; $qaMock.exclusionRemovals++ }
+    function Update-MpSignature { [CmdletBinding()]param() $qaMock.signatureUpdates++ }
+    function Get-MpComputerStatus { [CmdletBinding()]param() $qaMock.statusReads++; return @{ AntivirusEnabled=$qaMock.ready; RealTimeProtectionEnabled=$qaMock.ready } }
+    function Start-Sleep { param($Seconds) $qaMock.waits++ }
+    $env:GITHUB_ACTIONS='true'; $env:RUNNER_OS='Windows'; $env:RUNNER_ENVIRONMENT='github-hosted'
+    $qaMock.policyWrites=0; $qaMock.serviceStarts=0; $qaMock.preferenceWrites=0; $qaMock.exclusionRemovals=0; $qaMock.signatureUpdates=0; $qaMock.statusReads=0; $qaMock.waits=0; $qaMock.ready=$true
+    & $activationScript | Out-Null
+    Assert ($qaMock.policyWrites -eq 1 -and $qaMock.serviceStarts -eq 1 -and $qaMock.preferenceWrites -eq 1 -and $qaMock.exclusionRemovals -eq 1 -and $qaMock.signatureUpdates -eq 1 -and $qaMock.statusReads -eq 1) 'Ready scanner was not verified'
+    $qaMock.ready=$false; $qaMock.statusReads=0; $qaMock.waits=0
+    try { & $activationScript | Out-Null; throw 'Inactive scanner was accepted' }
+    catch { Assert ($_.Exception.Message -like '*publication remains blocked*') 'Inactive scanner did not fail closed' }
+    Assert ($qaMock.statusReads -eq 12 -and $qaMock.waits -eq 12) 'Activation wait must be bounded'
+    Write-Output 'RELEASE_DEFENDER_CHECKS_PASSED'
+}
+finally { foreach ($name in $original.Keys) { [Environment]::SetEnvironmentVariable($name,$original[$name]) } }