diff --git a/goldens/public-api/angular_devkit/core/index.api.md b/goldens/public-api/angular_devkit/core/index.api.md
index 748faf2bbeb4..a6810f5a8da8 100644
--- a/goldens/public-api/angular_devkit/core/index.api.md
+++ b/goldens/public-api/angular_devkit/core/index.api.md
@@ -553,7 +553,7 @@ function oneLine(strings: TemplateStringsArray, ...values: any[]): string;
 // @public (undocumented)
 function parseJsonPointer(pointer: JsonPointer): string[];
 
-// @public (undocumented)
+// @public
 export class PartiallyOrderedSet<T> {
     // (undocumented)
     [Symbol.iterator](): IterableIterator<T, undefined, unknown>;
diff --git a/packages/angular_devkit/architect/src/jobs/create-job-handler.ts b/packages/angular_devkit/architect/src/jobs/create-job-handler.ts
index 06aabd61e5f3..6363b7b70767 100644
--- a/packages/angular_devkit/architect/src/jobs/create-job-handler.ts
+++ b/packages/angular_devkit/architect/src/jobs/create-job-handler.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { BaseException, JsonValue, isPromise, logging } from '@angular-devkit/core';
+import { BaseException, JsonValue, logging } from '@angular-devkit/core';
 import {
   Observable,
   Observer,
@@ -27,6 +27,11 @@ import {
   JobOutboundMessageKind,
 } from './api';
 
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function isPromise(obj: any): obj is Promise<any> {
+  return !!obj && typeof obj.then === 'function';
+}
+
 export class ChannelAlreadyExistException extends BaseException {
   constructor(name: string) {
     super(`Channel ${JSON.stringify(name)} already exist.`);
diff --git a/packages/angular_devkit/core/src/json/schema/interface.ts b/packages/angular_devkit/core/src/json/schema/interface.ts
index 10f89efaf94e..8974746319f7 100644
--- a/packages/angular_devkit/core/src/json/schema/interface.ts
+++ b/packages/angular_devkit/core/src/json/schema/interface.ts
@@ -85,7 +85,7 @@ export interface SchemaRegistry {
   /**
    * Add a transformation step before the validation of any Json.
    * @param {JsonVisitor} visitor The visitor to transform every value.
-   * @param {JsonVisitor[]} deps A list of other visitors to run before.
+   * @param {JsonVisitor[]} deps [Deprecated] A list of other visitors to run before. Add transforms in the desired execution order instead.
    */
   addPreTransform(visitor: JsonVisitor, deps?: JsonVisitor[]): void;
 
@@ -94,7 +94,7 @@ export interface SchemaRegistry {
    * after the POST, so if transformations are not compatible with the Schema it will not result
    * in an error.
    * @param {JsonVisitor} visitor The visitor to transform every value.
-   * @param {JsonVisitor[]} deps A list of other visitors to run before.
+   * @param {JsonVisitor[]} deps [Deprecated] A list of other visitors to run before. Add transforms in the desired execution order instead.
    */
   addPostTransform(visitor: JsonVisitor, deps?: JsonVisitor[]): void;
 }
diff --git a/packages/angular_devkit/core/src/json/schema/registry.ts b/packages/angular_devkit/core/src/json/schema/registry.ts
index 11632b64f86a..d433a41bd460 100644
--- a/packages/angular_devkit/core/src/json/schema/registry.ts
+++ b/packages/angular_devkit/core/src/json/schema/registry.ts
@@ -13,7 +13,7 @@ import * as https from 'node:https';
 import * as Url from 'node:url';
 import { Observable, from, isObservable, lastValueFrom } from 'rxjs';
 import { BaseException } from '../../exception';
-import { PartiallyOrderedSet, deepCopy } from '../../utils';
+import { PartiallyOrderedSet } from '../../utils';
 import { JsonArray, JsonObject, JsonValue, isJsonObject } from '../utils';
 import {
   JsonPointer,
@@ -171,7 +171,7 @@ export class CoreSchemaRegistry implements SchemaRegistry {
   /**
    * Add a transformation step before the validation of any Json.
    * @param {JsonVisitor} visitor The visitor to transform every value.
-   * @param {JsonVisitor[]} deps A list of other visitors to run before.
+   * @param {JsonVisitor[]} deps [Deprecated] A list of other visitors to run before. Add transforms in the desired execution order instead.
    */
   addPreTransform(visitor: JsonVisitor, deps?: JsonVisitor[]): void {
     this._pre.add(visitor, deps);
@@ -182,7 +182,7 @@ export class CoreSchemaRegistry implements SchemaRegistry {
    * after the POST, so if transformations are not compatible with the Schema it will not result
    * in an error.
    * @param {JsonVisitor} visitor The visitor to transform every value.
-   * @param {JsonVisitor[]} deps A list of other visitors to run before.
+   * @param {JsonVisitor[]} deps [Deprecated] A list of other visitors to run before. Add transforms in the desired execution order instead.
    */
   addPostTransform(visitor: JsonVisitor, deps?: JsonVisitor[]): void {
     this._post.add(visitor, deps);
@@ -257,7 +257,7 @@ export class CoreSchemaRegistry implements SchemaRegistry {
       }
     }
 
-    const schemaCopy = deepCopy(validate.schema as JsonObject);
+    const schemaCopy = structuredClone(validate.schema as JsonObject);
     visitJsonSchema(schemaCopy, visitor);
 
     return schemaCopy;
diff --git a/packages/angular_devkit/core/src/utils/lang.ts b/packages/angular_devkit/core/src/utils/lang.ts
index ffa8f2d034ed..ca59b945cbc8 100644
--- a/packages/angular_devkit/core/src/utils/lang.ts
+++ b/packages/angular_devkit/core/src/utils/lang.ts
@@ -10,6 +10,8 @@
 
 /**
  * Determine if the argument is shaped like a Promise
+ *
+ * @deprecated Use `typeof obj?.then === 'function'` instead.
  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export function isPromise(obj: any): obj is Promise<any> {
diff --git a/packages/angular_devkit/core/src/utils/object.ts b/packages/angular_devkit/core/src/utils/object.ts
index cc0218023bb0..9e7e5b78d3ad 100644
--- a/packages/angular_devkit/core/src/utils/object.ts
+++ b/packages/angular_devkit/core/src/utils/object.ts
@@ -8,6 +8,9 @@
 
 const copySymbol = Symbol();
 
+/**
+ * @deprecated Use `structuredClone` instead.
+ */
 export function deepCopy<T>(value: T): T {
   if (Array.isArray(value)) {
     return value.map((o) => deepCopy(o)) as unknown as T;
diff --git a/packages/angular_devkit/core/src/utils/partially-ordered-set.ts b/packages/angular_devkit/core/src/utils/partially-ordered-set.ts
index 297210c6ff89..21e3fb5c5410 100644
--- a/packages/angular_devkit/core/src/utils/partially-ordered-set.ts
+++ b/packages/angular_devkit/core/src/utils/partially-ordered-set.ts
@@ -19,6 +19,9 @@ export class CircularDependencyFoundException extends BaseException {
   }
 }
 
+/**
+ * @deprecated Use standard arrays and ensure correct insertion order instead.
+ */
 export class PartiallyOrderedSet<T> {
   private _items = new Map<T, Set<T>>();
 
diff --git a/packages/angular_devkit/schematics/tools/schema-option-transform.ts b/packages/angular_devkit/schematics/tools/schema-option-transform.ts
index f8198039b7ec..79abe6da6af0 100644
--- a/packages/angular_devkit/schematics/tools/schema-option-transform.ts
+++ b/packages/angular_devkit/schematics/tools/schema-option-transform.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { deepCopy, schema } from '@angular-devkit/core';
+import { schema } from '@angular-devkit/core';
 import { Observable, from, of as observableOf } from 'rxjs';
 import { first, map, mergeMap } from 'rxjs/operators';
 import { FileSystemSchematicContext, FileSystemSchematicDescription } from './description';
@@ -28,7 +28,7 @@ export function validateOptionsWithSchema(registry: schema.SchemaRegistry) {
     context?: FileSystemSchematicContext,
   ): Observable<T> => {
     // Prevent a schematic from changing the options object by making a copy of it.
-    options = deepCopy(options);
+    options = structuredClone(options);
 
     const withPrompts = context ? context.interactive : true;