ng serve (devserver) is currently broken at angular 8.0.0-beta.3 due to ts_devserver bug.
Bug is fixed in bazelbuild/rules_typescript@dffa7a2 and released in @bazel/typescript 0.24.1
Upgrade to schematics is pending #28625
Until then, users are blocked. (They won't be able to upgrade @bazel/typescript themselves due to versionCompat enforced by angular/bazel)