diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ac4f70..6504455 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ permissions:
 jobs:
   build-test:
     name: Build, test, and validate site
-    runs-on: windows-latest
+    runs-on: windows-2025
     steps:
       - name: Checkout
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
@@ -54,9 +54,9 @@ jobs:
       - name: Build Subscriber with warnings as errors
         run: dotnet build src/ARSVIN.Subscriber/ARSVIN.Subscriber.csproj -c Release --no-restore -warnaserror
 
-      - name: Test with coverage gate
+      - name: Test with whole-engine and protocol-core coverage gates
         shell: pwsh
-        run: .\scripts\test-with-coverage.ps1 -MinimumLineCoverage 50 -NoRestore
+        run: .\scripts\test-with-coverage.ps1 -MinimumWholeEngineLineCoverage 5.5 -MinimumLineCoverage 50 -NoRestore
 
       - name: Upload test and coverage evidence
         if: always()
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 8c4996e..ec25ceb 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -15,7 +15,7 @@ permissions:
 jobs:
   analyze:
     name: Analyze C# solution
-    runs-on: windows-latest
+    runs-on: windows-2025
     steps:
       - name: Checkout
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
diff --git a/.github/workflows/pages.yml b/.github/workflows/pages.yml
index 099c23b..2b1de49 100644
--- a/.github/workflows/pages.yml
+++ b/.github/workflows/pages.yml
@@ -8,6 +8,7 @@ on:
       - 'docs/**'
       - 'scripts/build-public-site.py'
       - 'scripts/validate-public-site.ps1'
+      - 'scripts/validate-public-site.py'
       - '.github/workflows/pages.yml'
   workflow_dispatch:
 
@@ -25,7 +26,7 @@ jobs:
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 4e46619..ceb63bf 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -41,7 +41,7 @@ env:
 jobs:
   package:
     name: Validate portable EXEs and installer
-    runs-on: windows-latest
+    runs-on: windows-2025
     outputs:
       version: ${{ steps.version.outputs.value }}
       tag_name: ${{ steps.version.outputs.tag_name }}
@@ -60,8 +60,9 @@ jobs:
           dotnet-version: 8.0.4xx
           cache: true
           cache-dependency-path: |
-            **/*.csproj
             Directory.Packages.props
+            src/**/packages.lock.json
+            tests/**/packages.lock.json
 
       - name: Resolve version
         id: version
@@ -327,7 +328,7 @@ jobs:
     name: Publish GitHub Release
     if: github.ref_type == 'tag'
     needs: package
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     permissions:
       contents: write
       id-token: write
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2e7bc9e..354abd5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ All notable ARSVIN changes are documented here using a lightweight Keep a Change
 - Added recursive validation for all HTML metadata, structured data, canonical uniqueness, local references, search-index targets, sitemap coverage, web-manifest icons, and robots metadata.
 - Added committed NuGet lock files for Publisher, Subscriber, the shared engine, and Tests.
 - Added CI evidence upload for the committed dependency lock graph.
+- Added a 5.5% whole-engine line-coverage regression floor alongside the existing 50% protocol-core floor.
 
 ### Changed
 
@@ -20,11 +21,14 @@ All notable ARSVIN changes are documented here using a lightweight Keep a Change
 - The product landing page now links directly to Quick Start, SV Profile Support, COMTRADE Replay, Subscriber Verification, Safety Boundaries, and the complete documentation index.
 - Validated CI, CodeQL, build, test, publish, and release paths now restore NuGet dependencies in locked mode.
 - README, build guidance, contributor guidance, repository structure, release examples, and coverage baselines now match the current shared-engine implementation.
+- CI, CodeQL, and release validation now use the explicit `windows-2025` runner image; Pages and release publication use `ubuntu-24.04`.
+- GitHub Pages now retriggers when the Python public-site validator changes.
 
 ### Security
 
 - Published GitHub Releases are now immutable in automation; a release job fails before attestation or upload when the semantic-version tag already has a GitHub Release.
 - Artifact corrections require a new semantic-version patch instead of replacing previously published binaries, checksums, or SBOMs.
+- Workflow execution no longer depends on moving `windows-latest` or `ubuntu-latest` labels.
 
 ### Planned
 
diff --git a/scripts/test-with-coverage.ps1 b/scripts/test-with-coverage.ps1
index 727dbbb..b3608b7 100644
--- a/scripts/test-with-coverage.ps1
+++ b/scripts/test-with-coverage.ps1
@@ -3,6 +3,9 @@ param(
     [ValidateRange(0, 100)]
     [double] $MinimumLineCoverage = 50,
 
+    [ValidateRange(0, 100)]
+    [double] $MinimumWholeEngineLineCoverage = 5.5,
+
     [switch] $NoRestore
 )
 
@@ -30,9 +33,8 @@ if ($NoRestore) {
     $arguments += '--no-restore'
 }
 
-# Instrument the complete production engine. The report remains a truthful
-# whole-engine baseline, while the regression gate below is calculated over
-# the protocol-core surface that has an established test baseline.
+# Instrument the complete production engine. CI now protects both the truthful
+# whole-engine baseline and the higher protocol-core regression baseline.
 $arguments += @(
     '/p:RestoreLockedMode=true',
     '/p:TreatWarningsAsErrors=true',
@@ -130,6 +132,7 @@ $coreLineCoverage = [Math]::Round(($coreLinesCovered / $coreLinesValid) * 100, 2
 
 Write-Host "Whole engine lines: $overallLinesValid"
 Write-Host "Whole engine line coverage: $overallLineCoverage%"
+Write-Host "Whole engine minimum required: $MinimumWholeEngineLineCoverage%"
 Write-Host "Protocol core files: $($coreFiles.Count)"
 Write-Host "Protocol core lines: $coreLinesValid"
 Write-Host "Protocol core covered lines: $coreLinesCovered"
@@ -145,6 +148,7 @@ if ($env:GITHUB_STEP_SUMMARY) {
 |---|---:|
 | Whole `ARSVIN.Engine` instrumented lines | **$overallLinesValid** |
 | Whole engine line coverage | **$overallLineCoverage%** |
+| Whole-engine regression floor | **$MinimumWholeEngineLineCoverage%** |
 | Tested protocol-core files | **$($coreFiles.Count)** |
 | Protocol-core instrumented lines | **$coreLinesValid** |
 | Protocol-core covered lines | **$coreLinesCovered** |
@@ -154,6 +158,14 @@ if ($env:GITHUB_STEP_SUMMARY) {
 "@ | Add-Content $env:GITHUB_STEP_SUMMARY
 }
 
+$coverageFailures = [System.Collections.Generic.List[string]]::new()
+if ($overallLineCoverage -lt $MinimumWholeEngineLineCoverage) {
+    $coverageFailures.Add("Whole-engine line coverage $overallLineCoverage% is below the required $MinimumWholeEngineLineCoverage%.")
+}
 if ($coreLineCoverage -lt $MinimumLineCoverage) {
-    throw "Protocol-core line coverage $coreLineCoverage% is below the required $MinimumLineCoverage%."
+    $coverageFailures.Add("Protocol-core line coverage $coreLineCoverage% is below the required $MinimumLineCoverage%.")
+}
+
+if ($coverageFailures.Count -gt 0) {
+    throw ($coverageFailures -join ' ')
 }