(aws-ecs): cannot set `ephemeralStorageGiB` for Windows platform v1.0.0

[longtv2222]

Describe the bug

I’m encountering an issue when trying to set ephemeralStorageGiB on FargateTaskDefinition while using platformVersion 1.0.0 for FargateService.

cdk synth failed with following error:

«EphemeralStorageGibFeatureRequires» The ephemeralStorageGiB feature requires platform version 1.4.0 or later, got 1.0.0

This validation is correct for Linux container, but it is incorrect for Windows container, where you can set ephemeralStorageGiB Fargate platform version to v1.0

Docs: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/fargate-task-storage.html#fargate-task-storage-windows-pv

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Library Version

No response

Expected Behavior

Synth completed successfully

Current Behavior

Reproduction Steps

To reproduce the issue:

import * as ecs from 'aws-cdk-lib/aws-ecs';
import * as cdk from 'aws-cdk-lib/core';
import { Construct } from 'constructs';

export class TestStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const cluster = new ecs.Cluster(this, "Cluster");

    const taskDefinition = new ecs.FargateTaskDefinition(this, "TaskDefinition", {
      runtimePlatform: {
        operatingSystemFamily: ecs.OperatingSystemFamily.WINDOWS_SERVER_2022_CORE,
        cpuArchitecture: ecs.CpuArchitecture.X86_64,
      },
      ephemeralStorageGiB: 40,
      cpu: 1024,
      memoryLimitMiB: 1024,
    });
    taskDefinition.addContainer("Container", {
      image: ecs.ContainerImage.fromRegistry("mcr.microsoft.com/windows/server:ltsc2022"),
    });

    new ecs.FargateService(this, "Service", {
      cluster,
      taskDefinition,
      platformVersion: ecs.FargatePlatformVersion.VERSION1_0,
    });

    /**
     * Workaround for now
     */
    // const cfnTaskDef = taskDefinition.node.defaultChild as ecs.CfnTaskDefinition;
    // cfnTaskDef.addPropertyOverride('EphemeralStorage', {
    //   'SizeInGiB': 40,
    // });
  }
}

Possible Solution

The error was thrown here:

aws-cdk/packages/aws-cdk-lib/aws-ecs/lib/fargate/fargate-service.ts

Lines 181 to 183 in 9aceb58

	if (props.taskDefinition.ephemeralStorageGiB && isUnsupportedPlatformVersion) {
	throw new ValidationError(lit`EphemeralStorageGibFeatureRequires`, `The ephemeralStorageGiB feature requires platform version ${FargatePlatformVersion.VERSION1_4} or later, got ${props.platformVersion}.`, scope);
	}

We probably need to:

1. Make the runtimePlatform property in TaskDefinition public

   aws-cdk/packages/aws-cdk-lib/aws-ecs/lib/base/task-definition.ts

   Line 459 in 9aceb58

   private runtimePlatform?: RuntimePlatform;

2. Use OperatingSystemFamily.isWindows function, and exclude Windows so that the validation error doesn't get triggered anymore
   

   aws-cdk/packages/aws-cdk-lib/aws-ecs/lib/runtime-platform.ts

   Lines 103 to 105 in 9aceb58

   	public isWindows(): boolean {
   	return this._operatingSystemFamily?.toLowerCase().startsWith('windows');
   	}

Additional Information/Context

No response

AWS CDK Library version (aws-cdk-lib)

2.247.0

AWS CDK CLI version

2.1113.0

Node.js Version

v24.11.1

OS

Windows

Language

TypeScript

Language Version

5.9.3

Other information

No response