The correct identifier to use for Claude 3 Haiku, is anthropic.claude-3-haiku-20240307-v1:0.

Long story short, you need to copy/paste the Amazon ID from the table where Amazon lists all of its Supported foundation models in Amazon Bedrock.

Supported foundation models in Amazon Bedrock

Copy/Paste the string listed in the Amazon ID column and use a RegionEndpoint enum that corresponds to one listed in Regions Supported column.

Code

var bedrockService = new BedrockService(
    new AmazonBedrockRuntimeClient("My AWS Credentials Access ID","My AWS Credentials Secret Access Key", RegionEndpoint.USEast1),
    "anthropic.claude-3-haiku-20240307-v1:0");

await foreach (var response in bedrockService.GetStreamingResponseAsync("Is this working?", new(), CancellationToken.None))
{
    Console.Write(response.Text);
}

More Information

Here's a blog post I wrote to help explain more: https://codetraveler.io/2025/03/25/introducing-awssdk-extensions-bedrock-meai-2/