diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index cbfb87c..699b152 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -2,21 +2,27 @@ name: tests
 on:
   [push, pull_request]
 
+permissions:
+  contents: read
+
 jobs:
   test:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
+    timeout-minutes: 10
 
     strategy:
+      fail-fast: false
       matrix:
         ruby-version: ['2.6', '2.7', '3.0']
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v7
       - name: Set up Ruby ${{ matrix.ruby-version }}
         uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby-version }}
+          bundler: '2.4.22'
           bundler-cache: true
       - name: Run tests
         run: bundle exec rspec
\ No newline at end of file
diff --git a/Gemfile b/Gemfile
index ee112d8..617a6c2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,8 @@
 
 source 'https://rubygems.org'
 
-gem 'support', git: 'https://github.com/sinatra/mustermann.git'
+# Mustermann main now requires Ruby 3.3; keep legacy test helpers reproducible.
+gem 'support', git: 'https://github.com/sinatra/mustermann.git', tag: 'v3.0.4'
 
 gemspec
 
diff --git a/README.md b/README.md
index c860815..a2de196 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,14 @@
 
 This gem implements the `grape` pattern type for Mustermann.
 
+## Retirement notice
+
+**This adapter is retired; no further development is planned in this repository.** Starting with [Grape 3.3.0](https://rubygems.org/gems/grape/versions/3.3.0), released June 20, 2026, Grape maintains its path-pattern grammar internally as `Grape::Router::MustermannPattern` and depends on `mustermann` directly instead of `mustermann-grape` ([grape#2755](https://github.com/ruby-grape/grape/pull/2755)). Current Grape applications do not need this adapter; normal Grape routing requires no migration.
+
+Existing [RubyGems releases](https://rubygems.org/gems/mustermann-grape) remain available for older Grape versions that depend on this gem and for applications using the adapter directly. Retiring this repository does not remove those releases.
+
+If your application calls `Mustermann.new(pattern, type: :grape)`, keep an explicit `gem 'mustermann-grape'` dependency and `require 'mustermann/grape'`. Grape's internal pattern class does not register `type: :grape` and is not a public replacement for that standalone API. Report routing issues affecting current Grape in the [Grape repository](https://github.com/ruby-grape/grape/issues).
+
 [![tests](https://github.com/ruby-grape/mustermann-grape/workflows/tests/badge.svg)](https://github.com/ruby-grape/mustermann-grape/actions?query=workflow%3Atests)
 
 ## Overview