diff --git a/.github/workflows/main-build.yml b/.github/workflows/main-build.yml
index 59aa787f4..3dec9809e 100644
--- a/.github/workflows/main-build.yml
+++ b/.github/workflows/main-build.yml
@@ -24,7 +24,8 @@ concurrency:
 
 jobs:
   nightly-mac:
-    runs-on: macos-14
+    # macos-14 retired 2026-11-02; macos-15 is the pinned arm64 successor
+    runs-on: macos-15
     timeout-minutes: 90
     steps:
       - name: Checkout