AWS Lex descriptive bot builder

I am trying to create an AWS Lex bot with the AI Descriptive bot builder. No matter what I do I get: Please ensure your botLocale has Descriptive bot builder enabled with a valid foundation model, then try your request again.

I have finally managed to add the following IAM policy which is not automatically added by AWS, as I thought that was the problem: "Action": [ "bedrock:InvokeModel" ]. But it did not change anything.

The anthropic.claude-3-sonnet-20240229-v1:0 is active in Bedrock models and "access granted".

The docs state to enable generativeAISettings - but that is not possible before the language is added. And when adding the language I get above error.

When I am adding language through the console and enabling the AI features I get:

Error updating generative AI configurations for English (US) Please ensure your botLocale has Descriptive bot builder enabled with a valid foundation model, then try your request again.

I have also tried through the CLI:

aws lexv2-models create-bot-locale \
  --bot-id ----------- \
  --bot-version DRAFT \
  --locale-id en_US \
  --nlu-intent-confidence-threshold 0.5 \
  --profile chatbot \
  --generative-ai-settings '{
  "buildtimeSettings": {
    "descriptiveBotBuilder": {
      "enabled": true,
      "bedrockModelSpecification": {
        "modelArn": "arn:aws:bedrock:eu-central-1::foundation-model/anthropic.claude-3-sonnet-20240229-v1:0 "
      }
    }
  },
  "runtimeSettings": {
    "nluImprovement": { 
      "enabled": true
    },
    "slotResolutionImprovement": {
      "enabled": true,
      "bedrockModelSpecification": {
        "modelArn": "arn:aws:bedrock:eu-central-1::foundation-model/anthropic.claude-3-sonnet-20240229-v1:0 "
      }
    }
  }
}'

Then I get: An error occurred (ValidationException) when calling the CreateBotLocale operation: Please ensure your botLocale has Slot resolution improvement enabled with a valid foundation model, then try your request again.

Can it be the actual model arns for different allowed models in slotResolutionImprovement and descriptiveBotBuilder? How do I know which models are allowed to use in each?

What am I missing?

Thanks

EDIT

If I create a language without AI enabled and then inspect with describe-bot-locale, I get:

{
    "botId": "---------",
    "botVersion": "DRAFT",
    "localeId": "en_US",
    "localeName": "English (US)",
    "nluIntentConfidenceThreshold": 0.5,
    "intentsCount": 1,
    "slotTypesCount": 0,
    "botLocaleStatus": "NotBuilt",
    "creationDateTime": "2025-08-17T10:49:55.144000+02:00",
    "lastUpdatedDateTime": "2025-08-17T10:51:21.295000+02:00",
    "generativeAISettings": {
        "runtimeSettings": {
            "slotResolutionImprovement": {
                "enabled": true,
                "bedrockModelSpecification": {
                    "modelArn": "arn:aws:bedrock:eu-central-1::foundation-model/anthropic.claude-3-haiku-20240307-v1:0"
                }
            }
        },
        "buildtimeSettings": {
            "descriptiveBotBuilder": {
                "enabled": false,
                "bedrockModelSpecification": {
                    "modelArn": "arn:aws:bedrock:eu-central-1::foundation-model/anthropic.claude-3-sonnet-20240229-v1:0"
                }
            },
            "sampleUtteranceGeneration": {
                "enabled": false,
                "bedrockModelSpecification": {
                    "modelArn": "arn:aws:bedrock:eu-central-1::foundation-model/anthropic.claude-3-sonnet-20240229-v1:0"
                }
            }
        }
    }
}

These ARNs are set by AWS but the error is still:

Please ensure your botLocale has Descriptive bot builder enabled with a valid foundation model, then try your request again.

Update 19/8 I have now been in contact with AWS support, and their support engineer has confirmed that he can replicate the error. So, AWS are now working on a fix.

Apparently, according to AWS support it was the AWS engineers updating the Bedrock models that caused the issue.

Right now it is possible to deploy via the descriptive bot builder in us-east-1 only. Then it is possible to export and import in another region.