diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c3b3d39..c9d8f73 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,6 +20,11 @@ jobs:
     steps:
       - name: Check out repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          # `actions/checkout` defaults to leaving the job token in `.git/config`, where any later
+          # step — including one a pull request added to this file — could read or reuse it. Nothing
+          # in this workflow pushes, so the credential is never needed after checkout.
+          persist-credentials: false
 
       - name: Set up Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
@@ -44,6 +49,11 @@ jobs:
     steps:
       - name: Check out repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          # `actions/checkout` defaults to leaving the job token in `.git/config`, where any later
+          # step — including one a pull request added to this file — could read or reuse it. Nothing
+          # in this workflow pushes, so the credential is never needed after checkout.
+          persist-credentials: false
 
       - name: Exercise PostgreSQL and S3 infrastructure
         run: bash scripts/smoke-infrastructure.sh
@@ -55,6 +65,11 @@ jobs:
     steps:
       - name: Check out repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          # `actions/checkout` defaults to leaving the job token in `.git/config`, where any later
+          # step — including one a pull request added to this file — could read or reuse it. Nothing
+          # in this workflow pushes, so the credential is never needed after checkout.
+          persist-credentials: false
 
       - name: Set up Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0