diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03ca1ae..24b44f7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,8 +11,9 @@ jobs:
     name: Python OSS alpha
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: astral-sh/setup-uv@v3
+      # Immutable pins for actions/checkout v4 and astral-sh/setup-uv v3.
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262
+      - uses: astral-sh/setup-uv@caf0cab7a618c569241d31dcd442f54681755d39
         with:
           enable-cache: true
       - run: uv python install 3.11
@@ -24,11 +25,12 @@ jobs:
     name: Node OSS alpha
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: pnpm/action-setup@v4
+      # Immutable pins for actions/checkout v4 and pnpm/action-setup v4.
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262
+      - uses: pnpm/action-setup@b906affcce14559ad1aafd4ab0e942779e9f58b1
         with:
           version: 9.12.0
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020
         with:
           node-version: 18.18.0
           cache: pnpm