cdk diff: ignores cloudformation parameters

[ChristerGustavsson]

Describe the bug

Running cdk diff on a stack with parameters passed to lambda functions as environment variables always assume it's using the default parameter values. This makes it show a diff when a previous deploy has set parameters to value different from the default value.

Regression Issue

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

Last Known Working CDK Version

No response

Expected Behavior

I expected to be able to send parameters used for diffs. Either with passing them again, or using a similar flag to cdk deploy with --previous-parameters

Current Behavior

Currently the parameters gets their default values and show diffs, if they have been updated by a deploy with values not equal to the default

Reproduction Steps

For example with a simple stack that uses a parameter, sent as environment to a lambda function

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

export default class StackWithParameters extends cdk.Stack {
  constructor(scope: Construct) {
    super(scope, 'StackWithParameters')

    const logLevel = new cdk.CfnParameter(this, 'LogLevel', {
      type: 'String',
      description: 'The log level to use for lambda functions, defaults to "INFO"',
      default: 'INFO',
    })

    new lambda.Function(this, 'Function', {
      code: lambda.Code.fromInline('foo'),
      handler: 'index.handler',
      runtime: lambda.Runtime.NODEJS_LATEST,
      environment: {
        LOG_LEVEL: logLevel.valueAsString,
      },
    })
  }
}

When deployed with parameter set to "DEBUG":

npx cdk deploy -e StackWithParameters --parameters "StackWithParameters:LogLevel=DEBUG"

It will always show a diff on the lambda environment variables:

npx cdk diff -e StackWithParameters --parameters "StackWithParameters:LogLevel=DEBUG"

Possible Solution

Add --parameters, or --previous-parameters to the cdk diff command

Additional Information/Context

No response

CDK CLI Version

2.1139.0 (build d51353e)

Framework Version

2.266.0

Node.js Version

v24.14.1

OS

macOs 26.6.2 (25G83)

Language

TypeScript

Language Version

TypeScript (6.0.3)

Other information

No response