diff --git a/.github/workflows/pkg-pr-new.yml b/.github/workflows/pkg-pr-new.yml
index 2b1b6807..759a56e6 100644
--- a/.github/workflows/pkg-pr-new.yml
+++ b/.github/workflows/pkg-pr-new.yml
@@ -82,7 +82,8 @@ jobs:
           tags: cloudflare/sandbox:${{ steps.package-version.outputs.version }}
           cache-from: |
             type=gha,scope=preview-pr-${{ github.event.pull_request.number }}
-            type=gha,scope=pr-${{ github.event.pull_request.number }}
+            type=gha,scope=pr-${{ github.event.pull_request.number }}-amd64
+            type=gha,scope=release-amd64
             type=gha,scope=release
           cache-to: type=gha,mode=max,scope=preview-pr-${{ github.event.pull_request.number }}
           build-args: |
diff --git a/.github/workflows/pullrequest.yml b/.github/workflows/pullrequest.yml
index 1a024bc1..3138cb55 100644
--- a/.github/workflows/pullrequest.yml
+++ b/.github/workflows/pullrequest.yml
@@ -120,12 +120,13 @@ jobs:
         with:
           context: .
           file: packages/sandbox/Dockerfile
+          platforms: linux/amd64  # Explicit single-arch for compatibility with release-amd64 cache
           load: true  # Load into Docker daemon for local testing
           tags: cloudflare/sandbox-test:${{ needs.unit-tests.outputs.version || '0.0.0' }}
           cache-from: |
-            type=gha,scope=pr-${{ github.event.pull_request.number }}
-            type=gha,scope=release
-          cache-to: type=gha,mode=max,scope=pr-${{ github.event.pull_request.number }}
+            type=gha,scope=pr-${{ github.event.pull_request.number }}-amd64
+            type=gha,scope=release-amd64
+          cache-to: type=gha,mode=max,scope=pr-${{ github.event.pull_request.number }}-amd64
           build-args: |
             SANDBOX_VERSION=${{ needs.unit-tests.outputs.version || '0.0.0' }}
 
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index ec123771..581118a6 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -113,6 +113,18 @@ jobs:
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
+      - name: Build and cache single-arch image (for PR cache reuse)
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: packages/sandbox/Dockerfile
+          platforms: linux/amd64
+          push: false  # Don't push, just cache
+          cache-from: type=gha,scope=release-amd64
+          cache-to: type=gha,mode=max,scope=release-amd64
+          build-args: |
+            SANDBOX_VERSION=${{ needs.unit-tests.outputs.version }}
+
       - name: Build and push Docker image (beta)
         uses: docker/build-push-action@v6
         with:
@@ -121,7 +133,9 @@ jobs:
           platforms: linux/amd64,linux/arm64
           push: true
           tags: cloudflare/sandbox:${{ needs.unit-tests.outputs.version }}-beta
-          cache-from: type=gha,scope=release
+          cache-from: |
+            type=gha,scope=release-amd64
+            type=gha,scope=release
           cache-to: type=gha,mode=max,scope=release
           build-args: |
             SANDBOX_VERSION=${{ needs.unit-tests.outputs.version }}
@@ -170,6 +184,18 @@ jobs:
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
+      - name: Build and cache single-arch image (for PR cache reuse)
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: packages/sandbox/Dockerfile
+          platforms: linux/amd64
+          push: false  # Don't push, just cache
+          cache-from: type=gha,scope=release-amd64
+          cache-to: type=gha,mode=max,scope=release-amd64
+          build-args: |
+            SANDBOX_VERSION=${{ needs.unit-tests.outputs.version }}
+
       - name: Build and push Docker image
         uses: docker/build-push-action@v6
         with:
@@ -178,7 +204,9 @@ jobs:
           platforms: linux/amd64,linux/arm64
           push: true
           tags: cloudflare/sandbox:${{ needs.unit-tests.outputs.version }}
-          cache-from: type=gha,scope=release
+          cache-from: |
+            type=gha,scope=release-amd64
+            type=gha,scope=release
           cache-to: type=gha,mode=max,scope=release
           build-args: |
             SANDBOX_VERSION=${{ needs.unit-tests.outputs.version }}