Text-only channel messages fail when R2 is not configured

[mwzhu]

What I expected to happen

Sending or fetching a text-only channel message should work even when Cloudflare R2 and the image proxy are not configured.

What actually happened

In a local/self-hosted setup without R2_S3_API / R2 credentials and without IMAGE_PROXY_URL / IMAGE_PROXY_SECRET, sending a plain text message returned:

• 400 Bad Request
• {"detail":"Invalid endpoint: "}

The message row was already inserted successfully, but the response path failed afterward.

Steps to reproduce

1. Run the app locally with:
   • IMAGE_PROXY_URL unset
   • IMAGE_PROXY_SECRET unset
   • R2_S3_API unset
   • R2_ACCESS_KEY_ID unset
   • R2_SECRET_ACCESS_KEY unset
2. Create or open a channel
3. Send a plain text message
4. Observe the request fail with 400 Bad Request

Suspected cause

_enrich_messages_with_file_urls_legacy() initializes the R2 client before checking whether the message actually contains any file blocks. For text-only messages, that eagerly creates a boto3 client with an empty endpoint, which raises Invalid endpoint: .

Environment

• OS: macOS
• Browser: Chrome
• Local/self-hosted core-oss
• Backend and frontend running locally