diff --git a/goldens/public-api/common/index.api.md b/goldens/public-api/common/index.api.md
index 211fcfa68334..4a5a43b7a270 100644
--- a/goldens/public-api/common/index.api.md
+++ b/goldens/public-api/common/index.api.md
@@ -379,18 +379,18 @@ export class KeyValuePipe implements PipeTransform {
     // (undocumented)
     transform<K, V>(input: ReadonlyMap<K, V>, compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null): Array<KeyValue<K, V>>;
     // (undocumented)
-    transform<K extends number, V>(input: Record<K, V>, compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null): Array<KeyValue<string, V>>;
-    // (undocumented)
     transform<K extends string, V>(input: Record<K, V> | ReadonlyMap<K, V>, compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null): Array<KeyValue<K, V>>;
     // (undocumented)
+    transform<K extends number, V>(input: Record<K, V>, compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null): Array<KeyValue<string, V>>;
+    // (undocumented)
     transform(input: null | undefined, compareFn?: ((a: KeyValue<unknown, unknown>, b: KeyValue<unknown, unknown>) => number) | null): null;
     // (undocumented)
     transform<K, V>(input: ReadonlyMap<K, V> | null | undefined, compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null): Array<KeyValue<K, V>> | null;
     // (undocumented)
-    transform<K extends number, V>(input: Record<K, V> | null | undefined, compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null): Array<KeyValue<string, V>> | null;
-    // (undocumented)
     transform<K extends string, V>(input: Record<K, V> | ReadonlyMap<K, V> | null | undefined, compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null): Array<KeyValue<K, V>> | null;
     // (undocumented)
+    transform<K extends number, V>(input: Record<K, V> | null | undefined, compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null): Array<KeyValue<string, V>> | null;
+    // (undocumented)
     transform<T>(input: T, compareFn?: T extends object ? (a: T[keyof T], b: T[keyof T]) => number : never): T extends object ? Array<KeyValue<keyof T, T[keyof T]>> : null;
     // (undocumented)
     static ɵfac: i0.ɵɵFactoryDeclaration<KeyValuePipe, never>;
diff --git a/packages/common/src/pipes/keyvalue_pipe.ts b/packages/common/src/pipes/keyvalue_pipe.ts
index 17e61214d401..8278f432075f 100644
--- a/packages/common/src/pipes/keyvalue_pipe.ts
+++ b/packages/common/src/pipes/keyvalue_pipe.ts
@@ -75,14 +75,23 @@ export class KeyValuePipe implements PipeTransform {
     input: ReadonlyMap<K, V>,
     compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null,
   ): Array<KeyValue<K, V>>;
-  transform<K extends number, V>(
-    input: Record<K, V>,
-    compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null,
-  ): Array<KeyValue<string, V>>;
+  // TypeScript tries overloads top-to-bottom and stops at the first match. A
+  // plain object with string-literal keys (e.g. `Record<'a' | 'b', V>`) also
+  // happens to satisfy the more general `K extends number` overload below once
+  // inference falls back to its constraint — so if that overload is checked
+  // first, it wins by accident and silently widens `key` from `'a' | 'b'` to
+  // plain `string`. Putting the string overload first means it claims
+  // string-keyed input before the number overload ever gets a chance, while
+  // genuinely numeric-keyed input (which fails `K extends string`) still falls
+  // through to the number overload exactly as before.
   transform<K extends string, V>(
     input: Record<K, V> | ReadonlyMap<K, V>,
     compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null,
   ): Array<KeyValue<K, V>>;
+  transform<K extends number, V>(
+    input: Record<K, V>,
+    compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null,
+  ): Array<KeyValue<string, V>>;
   transform(
     input: null | undefined,
     compareFn?: ((a: KeyValue<unknown, unknown>, b: KeyValue<unknown, unknown>) => number) | null,
@@ -91,16 +100,16 @@ export class KeyValuePipe implements PipeTransform {
     input: ReadonlyMap<K, V> | null | undefined,
     compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null,
   ): Array<KeyValue<K, V>> | null;
-  transform<K extends number, V>(
-    input: Record<K, V> | null | undefined,
-    compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null,
-  ): Array<KeyValue<string, V>> | null;
-
   transform<K extends string, V>(
     input: Record<K, V> | ReadonlyMap<K, V> | null | undefined,
     compareFn?: ((a: KeyValue<K, V>, b: KeyValue<K, V>) => number) | null,
   ): Array<KeyValue<K, V>> | null;
 
+  transform<K extends number, V>(
+    input: Record<K, V> | null | undefined,
+    compareFn?: ((a: KeyValue<string, V>, b: KeyValue<string, V>) => number) | null,
+  ): Array<KeyValue<string, V>> | null;
+
   transform<T>(
     input: T,
     compareFn?: T extends object ? (a: T[keyof T], b: T[keyof T]) => number : never,
diff --git a/packages/common/test/pipes/keyvalue_pipe_spec.ts b/packages/common/test/pipes/keyvalue_pipe_spec.ts
index 9b4727f5eef5..d63e39a82921 100644
--- a/packages/common/test/pipes/keyvalue_pipe_spec.ts
+++ b/packages/common/test/pipes/keyvalue_pipe_spec.ts
@@ -100,6 +100,38 @@ describe('KeyValuePipe', () => {
       expect(pipe.transform(value)).toEqual(null);
     });
 
+    it('should preserve a literal key union instead of widening it to string', () => {
+      const pipe = new KeyValuePipe(defaultKeyValueDiffers);
+      const input: Record<'a' | 'b', number> = {a: 1, b: 2};
+      const result = pipe.transform(input);
+
+      // Compile-time check: if `key` had widened back to plain `string`, this
+      // assignment would fail to compile — that's the actual bug from #43883.
+      const key: 'a' | 'b' = result[0].key;
+
+      expect(key).toBe('a');
+      expect(result).toEqual([
+        {key: 'a', value: 1},
+        {key: 'b', value: 2},
+      ]);
+    });
+
+    it('should still collapse a numerically-keyed object to string keys', () => {
+      const pipe = new KeyValuePipe(defaultKeyValueDiffers);
+      const input: Record<1 | 2, string> = {1: 'one', 2: 'two'};
+      const result = pipe.transform(input);
+
+      // Numeric keys become strings at runtime (Object.keys() always returns
+      // strings), so `key` should stay `string`, not narrow to `1 | 2`.
+      const key: string = result[0].key;
+
+      expect(key).toBe('1');
+      expect(result).toEqual([
+        {key: '1', value: 'one'},
+        {key: '2', value: 'two'},
+      ]);
+    });
+
     it('should accept an object with optional keys', () => {
       interface MyInterface {
         one: string;