diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index c01e135..62176e7 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -38,10 +38,19 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      # `vercel build` runs the project's install command (pnpm), so pnpm must
+      # be on PATH or the build fails with `spawn pnpm ENOENT`. pnpm 10 matches
+      # local dev (10.11.1) and Vercel's detected version for this project.
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
       - name: Setup Node
         uses: actions/setup-node@v4
         with:
           node-version: '24'
+          cache: pnpm
 
       - name: Install Vercel CLI
         run: npm install -g vercel@latest