diff --git a/.github/workflows/ubuntu-latest-docs.yml b/.github/workflows/ubuntu-latest-docs.yml
index d1c06f746..1d69dd5bf 100644
--- a/.github/workflows/ubuntu-latest-docs.yml
+++ b/.github/workflows/ubuntu-latest-docs.yml
@@ -21,6 +21,7 @@ on:
   pull_request:
     branches:
       - main
+      - 'release/v*'
     paths:
       - 'docs/**'
       - '.assets/**'
diff --git a/.github/workflows/ubuntu-latest.yml b/.github/workflows/ubuntu-latest.yml
index 73c0e46c4..ab40a8071 100644
--- a/.github/workflows/ubuntu-latest.yml
+++ b/.github/workflows/ubuntu-latest.yml
@@ -20,6 +20,7 @@ on:
   pull_request:
     branches:
       - main
+      - 'release/v*'
     paths-ignore:
       - 'docs/**'
       - '.assets/**'
diff --git a/build/Build.CI.GitHubActions.cs b/build/Build.CI.GitHubActions.cs
index 6c9c0ce79..ddb849f52 100644
--- a/build/Build.CI.GitHubActions.cs
+++ b/build/Build.CI.GitHubActions.cs
@@ -32,7 +32,9 @@
     FetchDepth = 0,
     Submodules = GitHubActionsSubmodules.Recursive,
     CheckoutRef = "${{ github.head_ref }}",
-    OnPullRequestBranches = new[] { MainBranch },
+    // Trigger for PRs targeting main OR any release/vN branch — both are
+    // long-lived and protected; both require the ubuntu-latest status check.
+    OnPullRequestBranches = new[] { MainBranch, ReleaseBranchPattern },
     OnPullRequestExcludePaths = new[] { "docs/**", ".assets/**", "**/*.md" },
     InvokedTargets = new[] { nameof(ITest.Test), nameof(IPack.Pack) },
     PublishArtifacts = false)]
diff --git a/build/Build.cs b/build/Build.cs
index 35b724935..3a6ed903d 100644
--- a/build/Build.cs
+++ b/build/Build.cs
@@ -46,6 +46,13 @@ partial class Build
 
     const string MainBranch = "main";
 
+    // Glob matching the long-lived release-branch family (release/v11, release/v12, ...).
+    // Used by Build.CI.GitHubActions to extend PR-validation workflows to cover PRs
+    // targeting any release branch — branch protection on release/vN requires the
+    // ubuntu-latest status check, which only fires if the workflow's branches: list
+    // matches the PR's base ref. See milestone #13.
+    const string ReleaseBranchPattern = "release/v*";
+
     // Trunk-based versioning. Nerdbank.GitVersioning computes the canonical version
     // (major.minor from version.json + git-height as patch). ThisAssembly is generated by
     // NB.GV at compile time; AssemblyInformationalVersion looks like "10.3.5+abc1234" so we