diff --git a/packages/@ember/-internals/glimmer/lib/component-managers/mount.ts b/packages/@ember/-internals/glimmer/lib/component-managers/mount.ts
index cf0bd78b57f..c1911994289 100644
--- a/packages/@ember/-internals/glimmer/lib/component-managers/mount.ts
+++ b/packages/@ember/-internals/glimmer/lib/component-managers/mount.ts
@@ -1,5 +1,6 @@
 import { Owner } from '@ember/-internals/owner';
 import { generateControllerFactory } from '@ember/-internals/routing';
+import { assert } from '@ember/debug';
 import EngineInstance from '@ember/engine/instance';
 import { associateDestroyableChild } from '@glimmer/destroyable';
 import {
@@ -74,6 +75,7 @@ class MountManager
     // we should resolve the engine app template in the helper
     // it also should use the owner that looked up the mount helper.
 
+    assert('Expected owner to be an EngineInstance', owner instanceof EngineInstance);
     let engine = owner.buildChildEngineInstance(name);
 
     engine.boot();
diff --git a/packages/@ember/-internals/glimmer/lib/component-managers/outlet.ts b/packages/@ember/-internals/glimmer/lib/component-managers/outlet.ts
index a2f904ea418..0ad930765ba 100644
--- a/packages/@ember/-internals/glimmer/lib/component-managers/outlet.ts
+++ b/packages/@ember/-internals/glimmer/lib/component-managers/outlet.ts
@@ -95,14 +95,14 @@ class OutletComponentManager
       let currentOwner = valueForRef(currentStateRef)!.render!.owner;
 
       if (parentOwner && parentOwner !== currentOwner) {
-        let engine = currentOwner as EngineInstance;
+        assert(
+          'Expected currentOwner to be an EngineInstance',
+          currentOwner instanceof EngineInstance
+        );
 
-        assert('invalid engine: missing mountPoint', typeof currentOwner.mountPoint === 'string');
-        assert('invalid engine: missing routable', currentOwner.routable === true);
+        let mountPoint = currentOwner.mountPoint;
 
-        let mountPoint = engine.mountPoint!;
-
-        state.engine = engine;
+        state.engine = currentOwner;
         state.engineBucket = { mountPoint };
       }
     }
diff --git a/packages/@ember/-internals/glimmer/lib/components/link-to.ts b/packages/@ember/-internals/glimmer/lib/components/link-to.ts
index 0320e62a57c..5025ff4ef57 100644
--- a/packages/@ember/-internals/glimmer/lib/components/link-to.ts
+++ b/packages/@ember/-internals/glimmer/lib/components/link-to.ts
@@ -1,4 +1,3 @@
-import { Owner } from '@ember/-internals/owner';
 import { Route, RouterState, RoutingService } from '@ember/-internals/routing';
 import { isSimpleClick } from '@ember/-internals/views';
 import { assert, debugFreeze, inspect, warn } from '@ember/debug';
@@ -490,11 +489,13 @@ class LinkTo extends InternalComponent {
   }
 
   private get isEngine(): boolean {
-    return getEngineParent(this.owner as EngineInstance) !== undefined;
+    let owner = this.owner;
+    return owner instanceof EngineInstance && getEngineParent(owner) !== undefined;
   }
 
   private get engineMountPoint(): string | undefined {
-    return (this.owner as Owner | EngineInstance).mountPoint;
+    let owner = this.owner;
+    return owner instanceof EngineInstance ? owner.mountPoint : undefined;
   }
 
   private classFor(state: 'active' | 'loading' | 'disabled'): string {
diff --git a/packages/@ember/-internals/glimmer/tests/integration/application/debug-render-tree-test.ts b/packages/@ember/-internals/glimmer/tests/integration/application/debug-render-tree-test.ts
index 05cde32219d..8ec31d978e2 100644
--- a/packages/@ember/-internals/glimmer/tests/integration/application/debug-render-tree-test.ts
+++ b/packages/@ember/-internals/glimmer/tests/integration/application/debug-render-tree-test.ts
@@ -7,12 +7,12 @@ import {
 
 import { ENV } from '@ember/-internals/environment';
 import { Component, setComponentManager } from '@ember/-internals/glimmer';
-import { EngineInstanceOptions, Owner } from '@ember/-internals/owner';
+import { Owner } from '@ember/-internals/owner';
 import { Route } from '@ember/-internals/routing';
 import Controller from '@ember/controller';
 import { assert, captureRenderTree } from '@ember/debug';
 import Engine from '@ember/engine';
-import EngineInstance from '@ember/engine/instance';
+import EngineInstance, { EngineInstanceOptions } from '@ember/engine/instance';
 import { CapturedRenderNode } from '@glimmer/interfaces';
 import { componentCapabilities, setComponentTemplate } from '@glimmer/manager';
 import { templateOnlyComponent } from '@glimmer/runtime';
diff --git a/packages/@ember/-internals/owner/index.ts b/packages/@ember/-internals/owner/index.ts
index b355f45ea5d..4448d616c1e 100644
--- a/packages/@ember/-internals/owner/index.ts
+++ b/packages/@ember/-internals/owner/index.ts
@@ -1,9 +1,12 @@
 import { getOwner as glimmerGetOwner, setOwner as glimmerSetOwner } from '@glimmer/owner';
+import { TypeOptions } from '../container/lib/registry';
 
 /**
 @module @ember/application
 */
 
+export { TypeOptions };
+
 export interface FactoryClass {
   positionalParams?: string | string[] | undefined | null;
 }
@@ -16,25 +19,26 @@ export interface Factory<T, C extends FactoryClass | object = FactoryClass> {
   create(props?: { [prop: string]: any }): T;
 }
 
-export interface EngineInstanceOptions {
-  mountPoint: string;
-  routable: boolean;
-}
-
-import EngineInstance from '@ember/engine/instance';
-import { TypeOptions } from '../container/lib/registry';
+// A combination of the public methods on ContainerProxyMixin and RegistryProxyMixin
 export interface Owner {
+  // From ContainerProxy
+  ownerInjection(): void;
   lookup(fullName: string, options?: TypeOptions): unknown;
   factoryFor(fullName: string): Factory<unknown> | undefined;
-  register(fullName: string, factory: Factory<unknown>, options?: TypeOptions): void;
-  hasRegistration(name: string): boolean;
 
-  /** @internal */
-  mountPoint?: string;
-  /** @internal */
-  routable?: boolean;
-  /** @internal */
-  buildChildEngineInstance(name: string, options?: EngineInstanceOptions): EngineInstance;
+  // From RegistryProxy
+  resolveRegistration<T, C>(fullName: string): Factory<T, C> | undefined;
+  register(fullName: string, factory: Factory<unknown>, options?: TypeOptions): void;
+  unregister(fullName: string): void;
+  hasRegistration(fullName: string): boolean;
+  registeredOption<K extends keyof TypeOptions>(
+    fullName: string,
+    optionName: K
+  ): TypeOptions[K] | undefined;
+  registerOptions(fullName: string, options: TypeOptions): void;
+  registeredOptions(fullName: string): TypeOptions | undefined;
+  registerOptionsForType(type: string, options: TypeOptions): void;
+  registeredOptionsForType(type: string): TypeOptions | undefined;
 }
 
 /**
diff --git a/packages/@ember/-internals/routing/lib/system/route.ts b/packages/@ember/-internals/routing/lib/system/route.ts
index 6cc78f42568..ccee0955350 100644
--- a/packages/@ember/-internals/routing/lib/system/route.ts
+++ b/packages/@ember/-internals/routing/lib/system/route.ts
@@ -23,6 +23,7 @@ import {
 import { isProxy, lookupDescriptor, symbol } from '@ember/-internals/utils';
 import Controller from '@ember/controller';
 import { assert, info, isTesting } from '@ember/debug';
+import EngineInstance from '@ember/engine/instance';
 import { dependentKeyCompat } from '@ember/object/compat';
 import { once } from '@ember/runloop';
 import { DEBUG } from '@glimmer/env';
@@ -548,7 +549,7 @@ class Route<T = unknown>
   _setRouteName(name: string) {
     this.routeName = name;
     let owner = getOwner(this);
-    assert('Route is unexpectedly missing an owner', owner);
+    assert('Expected route to have EngineInstance as owner', owner instanceof EngineInstance);
     this.fullRouteName = getEngineRouteName(owner, name)!;
   }
 
@@ -1679,7 +1680,7 @@ class Route<T = unknown>
   modelFor(_name: string): unknown | undefined {
     let name;
     let owner = getOwner(this);
-    assert('Route is unexpectedly missing an owner', owner);
+    assert('Expected router owner to be an EngineInstance', owner instanceof EngineInstance);
     let transition =
       this._router && this._router._routerMicrolib
         ? this._router._routerMicrolib.activeTransition
@@ -2332,7 +2333,7 @@ function addQueryParamsObservers(controller: any, propNames: string[]) {
   });
 }
 
-function getEngineRouteName(engine: Owner, routeName: string) {
+function getEngineRouteName(engine: EngineInstance, routeName: string) {
   if (engine.routable) {
     let prefix = engine.mountPoint;
 
diff --git a/packages/@ember/-internals/routing/lib/system/router.ts b/packages/@ember/-internals/routing/lib/system/router.ts
index bf2907212d7..22a815443b4 100644
--- a/packages/@ember/-internals/routing/lib/system/router.ts
+++ b/packages/@ember/-internals/routing/lib/system/router.ts
@@ -46,6 +46,7 @@ import Router, {
   TransitionState,
 } from 'router_js';
 import { EngineRouteInfo } from './engines';
+import EngineInstance from '@ember/engine/instance';
 
 function defaultDidTransition<R extends Route>(
   this: EmberRouter<R>,
@@ -113,11 +114,6 @@ interface OutletState<T extends RenderOutletState = RenderOutletState> {
   wasUsed?: boolean;
 }
 
-interface EngineInstance extends Owner {
-  boot(): void;
-  destroy(): void;
-}
-
 export interface QueryParam {
   prop: string;
   urlKey: string;
@@ -1409,7 +1405,7 @@ class EmberRouter<R extends Route = Route> extends EmberObject.extend(Evented) i
 
     if (!engineInstance) {
       let owner = getOwner(this);
-      assert('Router is unexpectedly missing an owner', owner);
+      assert('Expected router to have EngineInstance as owner', owner instanceof EngineInstance);
 
       assert(
         `You attempted to mount the engine '${name}' in your router map, but the engine can not be found.`,
diff --git a/packages/@ember/-internals/routing/lib/utils.ts b/packages/@ember/-internals/routing/lib/utils.ts
index 6589ccff7d1..cb97efa92fb 100644
--- a/packages/@ember/-internals/routing/lib/utils.ts
+++ b/packages/@ember/-internals/routing/lib/utils.ts
@@ -1,6 +1,7 @@
 import { get } from '@ember/-internals/metal';
 import { getOwner } from '@ember/-internals/owner';
 import { assert, deprecate } from '@ember/debug';
+import EngineInstance from '@ember/engine/instance';
 import EmberError from '@ember/error';
 import Router, { STATE_SYMBOL, InternalRouteInfo, ModelFor } from 'router_js';
 import Route from './system/route';
@@ -247,7 +248,7 @@ export function prefixRouteNameArg<T extends NamedRouteArgs<Route> | UnnamedRout
 ): T {
   let routeName: string;
   let owner = getOwner(route);
-  assert('Route is unexpectedly missing an owner', owner);
+  assert('Expected route to have EngineInstance as owner', owner instanceof EngineInstance);
 
   let prefix = owner.mountPoint;
 
diff --git a/packages/@ember/-internals/runtime/lib/mixins/container_proxy.d.ts b/packages/@ember/-internals/runtime/lib/mixins/container_proxy.d.ts
index 31d9dbee6b1..2f9cbf8e112 100644
--- a/packages/@ember/-internals/runtime/lib/mixins/container_proxy.d.ts
+++ b/packages/@ember/-internals/runtime/lib/mixins/container_proxy.d.ts
@@ -1,10 +1,15 @@
 import { Container } from '@ember/-internals/container';
+import { TypeOptions } from '@ember/-internals/container/lib/registry';
+import { Factory } from '@ember/-internals/owner';
 import Mixin from '../../types/mixin';
 
 interface ContainerProxy {
-  ownerInjection: Container['ownerInjection'];
-  lookup: Container['lookup'];
-  factoryFor: Container['factoryFor'];
+  /** @internal */
+  __container__: Container;
+
+  ownerInjection(): void;
+  lookup(fullName: string, options?: TypeOptions): unknown;
+  factoryFor(fullName: string): Factory<unknown> | undefined;
 }
 declare const ContainerProxy: Mixin;
 
diff --git a/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.d.ts b/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.d.ts
index b18c207573b..08b5901250a 100644
--- a/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.d.ts
+++ b/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.d.ts
@@ -1,16 +1,23 @@
 import { Registry } from '@ember/-internals/container';
+import { TypeOptions } from '@ember/-internals/container/lib/registry';
+import { Factory } from '@ember/-internals/owner';
 import Mixin from '../../types/mixin';
 
 interface RegistryProxyMixin {
-  resolveRegistration: Registry['resolve'];
-  register: Registry['register'];
-  unregister: Registry['unregister'];
-  hasRegistration: Registry['has'];
-  registeredOption: Registry['getOption'];
-  registerOptions: Registry['options'];
-  registeredOptions: Registry['getOptions'];
-  registerOptionsForType: Registry['optionsForType'];
-  registeredOptionsForType: Registry['getOptionsForType'];
+  /** @internal */
+  __registry__: Registry;
+  resolveRegistration<T, C>(fullName: string): Factory<T, C> | undefined;
+  register(fullName: string, factory: Factory<unknown>, options?: TypeOptions): void;
+  unregister(fullName: string): void;
+  hasRegistration(fullName: string): boolean;
+  registeredOption<K extends keyof TypeOptions>(
+    fullName: string,
+    optionName: K
+  ): TypeOptions[K] | undefined;
+  registerOptions(fullName: string, options: TypeOptions): void;
+  registeredOptions(fullName: string): TypeOptions | undefined;
+  registerOptionsForType(type: string, options: TypeOptions): void;
+  registeredOptionsForType(type: string): TypeOptions | undefined;
 }
 declare const RegistryProxyMixin: Mixin;
 
diff --git a/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.js b/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.js
index 5f7a011dca9..59d1c4f70e1 100644
--- a/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.js
+++ b/packages/@ember/-internals/runtime/lib/mixins/registry_proxy.js
@@ -254,6 +254,7 @@ export default Mixin.create({
     @param  factoryNameOrType {String}
     @param  property {String}
     @param  injectionName {String}
+    @deprecated
   **/
   inject: registryAlias('injection'),
 });
diff --git a/packages/@ember/application/lib/application.d.ts b/packages/@ember/application/lib/application.d.ts
index bb3f709db98..96c93190ac6 100644
--- a/packages/@ember/application/lib/application.d.ts
+++ b/packages/@ember/application/lib/application.d.ts
@@ -1,6 +1,6 @@
-import { EngineInstanceOptions } from '@ember/-internals/owner';
 import { EventDispatcher } from '@ember/-internals/views';
 import Engine from '@ember/engine';
+import { EngineInstanceOptions } from '@ember/engine/instance';
 import ApplicationInstance, { BootOptions } from '../instance';
 
 export default class Application extends Engine {
diff --git a/packages/@ember/engine/index.d.ts b/packages/@ember/engine/index.d.ts
index 36a691b14a1..a867217311b 100644
--- a/packages/@ember/engine/index.d.ts
+++ b/packages/@ember/engine/index.d.ts
@@ -1,5 +1,4 @@
-import EngineInstance from './instance';
-import { EngineInstanceOptions } from '@ember/-internals/owner';
+import EngineInstance, { EngineInstanceOptions } from './instance';
 import { Namespace, RegistryProxyMixin } from '@ember/-internals/runtime';
 
 export { getEngineParent } from '@ember/engine/lib/engine-parent';
diff --git a/packages/@ember/engine/instance.d.ts b/packages/@ember/engine/instance.d.ts
index 76516f6f970..7dd7f96164f 100644
--- a/packages/@ember/engine/instance.d.ts
+++ b/packages/@ember/engine/instance.d.ts
@@ -3,12 +3,18 @@ import { Owner } from '@ember/-internals/owner';
 import { BootOptions } from '@ember/application/instance';
 import EmberObject from '@ember/object';
 
+export interface EngineInstanceOptions {
+  mountPoint: string;
+  routable: boolean;
+}
+
 interface EngineInstance extends RegistryProxyMixin, ContainerProxyMixin, Owner {}
 
 declare class EngineInstance extends EmberObject {
-  init(...args: unknown[]): void;
   boot(options?: BootOptions): void;
-  unregister(fullName: string): void;
+  mountPoint: string;
+  routable: boolean;
+  buildChildEngineInstance(name: string, options?: EngineInstanceOptions): EngineInstance;
 }
 
 export default EngineInstance;