diff --git a/src/utils/run-ability.ts b/src/utils/run-ability.ts
index f97d9c3ef..be6589f54 100644
--- a/src/utils/run-ability.ts
+++ b/src/utils/run-ability.ts
@@ -95,30 +95,37 @@ const buildFetchOptions = (
 	input: AbilityInput,
 	method: Method
 ) => {
-	const normalizedInput = input ?? null;
-
 	if ( method === 'GET' || method === 'DELETE' ) {
 		return {
 			path:
-				normalizedInput === null
+				input === undefined || input === null
 					? `/wp-abilities/v1/abilities/${ ability }/run`
 					: addQueryArgs(
 							`/wp-abilities/v1/abilities/${ ability }/run`,
 							{
-								input: normalizedInput,
+								input,
 							}
 					  ),
 			method,
 		};
 	}
 
-	return {
+	const options: {
+		path: string;
+		method: 'POST';
+		data?: {
+			input: AbilityInput;
+		};
+	} = {
 		path: `/wp-abilities/v1/abilities/${ ability }/run`,
 		method: 'POST' as const,
-		data: {
-			input: normalizedInput,
-		},
 	};
+
+	if ( input !== undefined ) {
+		options.data = { input };
+	}
+
+	return options;
 };
 
 export async function runAbility< T = unknown >(
@@ -131,7 +138,7 @@ export async function runAbility< T = unknown >(
 		if ( typeof abilitiesModule?.executeAbility === 'function' ) {
 			return ( await abilitiesModule.executeAbility(
 				ability,
-				input ?? null
+				input
 			) ) as T;
 		}
 
diff --git a/tests/unit/run-ability.test.ts b/tests/unit/run-ability.test.ts
new file mode 100644
index 000000000..77b82e947
--- /dev/null
+++ b/tests/unit/run-ability.test.ts
@@ -0,0 +1,82 @@
+/**
+ * WordPress dependencies
+ */
+import { executeAbility } from '@wordpress/abilities';
+import apiFetch from '@wordpress/api-fetch';
+
+/**
+ * Internal dependencies
+ */
+import { runAbility } from '../../src/utils/run-ability';
+
+jest.mock( '@wordpress/api-fetch', () => jest.fn() );
+jest.mock( '@wordpress/core-abilities', () => ( {
+	ready: Promise.resolve(),
+} ) );
+jest.mock( '@wordpress/abilities', () => ( {
+	executeAbility: jest.fn(),
+} ) );
+
+describe( 'runAbility', () => {
+	const mockedApiFetch = apiFetch as jest.Mock;
+	const mockedExecuteAbility = executeAbility as jest.Mock;
+
+	beforeEach( () => {
+		jest.clearAllMocks();
+		jest.spyOn( console, 'error' ).mockImplementation( () => undefined );
+		jest.spyOn( console, 'warn' ).mockImplementation( () => undefined );
+
+		mockedApiFetch.mockResolvedValue( 'fallback result' );
+		mockedExecuteAbility.mockResolvedValue( 'client result' );
+	} );
+
+	afterEach( () => {
+		jest.restoreAllMocks();
+	} );
+
+	it( 'passes omitted input to the client ability as undefined', async () => {
+		const result = await runAbility( 'core/users' );
+
+		expect( result ).toBe( 'client result' );
+		expect( mockedExecuteAbility ).toHaveBeenCalledWith(
+			'core/users',
+			undefined
+		);
+		expect( mockedApiFetch ).not.toHaveBeenCalled();
+	} );
+
+	it( 'omits REST input data when fallback runs without input', async () => {
+		mockedExecuteAbility.mockRejectedValueOnce(
+			Object.assign( new Error( 'Ability not found' ), {
+				code: 'ability_not_found',
+			} )
+		);
+
+		const result = await runAbility( 'core/users' );
+
+		expect( result ).toBe( 'fallback result' );
+		expect( mockedApiFetch ).toHaveBeenCalledWith( {
+			path: '/wp-abilities/v1/abilities/core/users/run',
+			method: 'POST',
+		} );
+	} );
+
+	it( 'keeps explicit empty-object input in REST fallback data', async () => {
+		mockedExecuteAbility.mockRejectedValueOnce(
+			Object.assign( new Error( 'Ability not found' ), {
+				code: 'ability_not_found',
+			} )
+		);
+
+		const result = await runAbility( 'core/users', {} );
+
+		expect( result ).toBe( 'fallback result' );
+		expect( mockedApiFetch ).toHaveBeenCalledWith( {
+			path: '/wp-abilities/v1/abilities/core/users/run',
+			method: 'POST',
+			data: {
+				input: {},
+			},
+		} );
+	} );
+} );