[NullVoxPopuli-ai-agent]

Merge #21726 first. This PR sits on top of it. Review only the last commit, b2e0f39e7e.

With EMBER_DROP_CLASSIC_FEATURES=true, Service from @ember/service is a plain class. It extends no other class.

import Service, { service } from '@ember/service';

export default class SessionService extends Service {
  @service router;

  constructor(owner) {
    super(owner);
    this.socket = new WebSocket('/session');
  }

  willDestroy() {
    super.willDestroy(...arguments);
    this.socket.close();
  }
}

Behavior with the flag

• The owner passes itself to the constructor, as it does for Glimmer components. getOwner(this) works in the constructor.
• @service injection works, because it only needs the owner.
• willDestroy stays the teardown hook. The plain class has no destroy method. When the owner is destroyed, or on unregister, the container calls willDestroy(), then destroy() from @ember/destroyable. isDestroyed(service) is then true, and destructors from registerDestructor run.
• The container knows the plain class by a mark from setPlainFrameworkClass, set only in the flag build. Other instances keep the destroy() call.
• super.willDestroy() works, because the base has an empty willDestroy().
• init, get, set, extend, reopen, destroy, isDestroying and isDestroyed do not exist on the class.
• A static create stays, because the container creates every instance through it.

Without the flag, Service does not change. A cast keeps the published type as the classic class, so apps get no new type errors.

Internal services

RouterService and the private RoutingService extend the exported class, so they run on the plain class in the flag build. They needed no source changes. The willDestroy hook of RouterService runs in both builds.

Tests

Change	Why
New @ember/service/tests/drop_classic_features_test.js	Checks the plain class: no base class, owner in the constructor, injection, the willDestroy hook. Registers only with the flag.
New ember/tests/without-EMBER_DROP_CLASSIC_FEATURES/service_test.js	Checks the classic API in builds without the flag: the EmberObject base, init, Service.extend, properties from create, get/set, willDestroy, the destroy flags, and get() on the router service. Registers only without the flag.
init() to constructor(owner) in three tests	Works on both base classes
service.get('x') to service.x in three router service test files	Works on both base classes
serviceInstance.set(...) to set(serviceInstance, ...)	Works on both base classes
The ProxyMixin service test skips with the flag	It uses Service.extend

Checks

Mode	Result
Default	9241 tests, 0 failures
ALL_DEPRECATIONS_ENABLED=true	9241 tests, 0 failures
OVERRIDE_DEPRECATION_VERSION=15.0.0	8264 tests, 0 failures
Production build	9078 tests, 0 failures
EMBER_DROP_CLASSIC_FEATURES=true	9241 tests, 0 failures

The type checks of the internals and the published types pass, with and without stable decorators. eslint, prettier and the docs check pass.

🤖 Generated with Claude Code