diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 53e2cba..872da82 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,14 +13,17 @@ concurrency:
 jobs:
   build-and-test:
     name: Build and test
-    runs-on: macos-latest
+    runs-on: macos-26
 
     steps:
       - uses: actions/checkout@v4
 
-      # macos-latest already ships the default Xcode; selecting a version by path is
-      # brittle because runner images move it. Print it instead so a failure log says
-      # which toolchain produced it.
+      # This manifest declares swift-tools-version 6.4, so the runner needs Xcode 26.
+      # macos-latest still ships an older default; select it explicitly.
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: '26'
+
       - name: Show toolchain
         run: |
           xcode-select -p