Files list API does not support listing files from managed agent API

[kzwang]

When using Managed Agent API, we need to pass scope_id and managed-agents-2026-04-01 beta header

In https://github.com/anthropics/anthropic-sdk-java/blob/main/anthropic-java-core/src/main/kotlin/com/anthropic/services/blocking/beta/FileServiceImpl.kt#L102, it always add the default beta headers without managed-agents-2026-04-01, so it cannot list those files, and we don't have a way to override the header

[TomerAberbach]

We'll look into whether the default headers there should be different, but I believe setting the betas field of FileListParams should allow you to overwrite the default beta headers.

Does that work for you for now?