After upgrading the CDK CLI package with npm, every CDK command in the app failed with Cloud assembly schema version mismatch: Maximum schema version supported is 10.0.0, but found 11.0.0, plus This CDK CLI is not compatible with the CDK library used by your application. The CLI and library versions looked compatible on paper. The root cause was a bug in npm version 7 itself, which broke the CLI install; npm 6 and below were unaffected.