diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index e2ce32033..1323c10f7 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -56,6 +56,18 @@ jobs:
           agentcore --version
           agentcore create --name sanitytest --language Python --framework Strands --model-provider Bedrock --memory none --json
           test -f sanitytest/agentcore/agentcore.json
+      # Synthesize the generated CDK app against whatever aws-cdk-lib `create` just
+      # resolved from the template's floating range. This is the only CI step that
+      # exercises the cloud-assembly schema write+read path with the LATEST published
+      # aws-cdk-lib, so it catches upstream CDK schema bumps that outrun the bundled
+      # CDK reader (the regression in #1465). Runs without AWS credentials.
+      - name: Smoke-test CDK synth (catches cloud-assembly schema mismatch)
+        if: matrix.node-version == '20.x'
+        working-directory: sanitytest/agentcore/cdk
+        run: |
+          echo '[{"name":"default","account":"000000000000","region":"us-east-1"}]' > ../aws-targets.json
+          npm run cdk -- synth --quiet
+          test -f cdk.out/manifest.json
       - name: Upload tarball artifact
         if: matrix.node-version == '20.x'
         uses: actions/upload-artifact@v7