Attachment download fails for blob/preview URLs

[j6e]

Hi,

I'm currently using this tool to automate some workflows and I'm having trouble downloading attachment files. I the tools keeps erroring, and the url works otherwise in the browser...

I used claude to help me submit the following bug report.

Description

The download-attachments command fails when trying to download attachments that use the blob/preview URL format.

Environment

bc4 version: latest
Basecamp account type: Basecamp 4

Steps to Reproduce

Find a card with an image attachment
Run: bc4 card download-attachments <card-id>

Error

✗ Error

some attachments failed to download

Downloading attachment 1/1: image.png
  ✗ Failed: could not extract upload ID from URL: https://preview.3.basecamp.com/4446664/blobs/{CENSORED}/previews/full?dppx=1.100000023841858

Failed: 1 attachments

Expected Behavior

Attachment should download successfully.

Analysis

The URL parser expects /uploads/{numeric-id} format but the attachment URL uses /blobs/{uuid} format instead.

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Failed attempt to solve

I've tried to solve the issue using Claude too, but I couldn't make it work... This is the explanation it gave me, take it with a grain of salt:

Important discovery: Basecamp's newer blob-based attachments use storage URLs (storage.3.basecamp.com) that require browser-based session authentication. OAuth tokens (which bc4 uses) cannot download these files through the API. This appears to be a Basecamp API limitation, not a bug in bc4.

[brigleb]

Yes, this seems to be an issue in the implementation of the API, Claude has basically told me the same thing. I'll see if I can check in with the Basecamp team somehow. It's an odd quirk for sure.

[brigleb]

For now I'm putting out a bugfix release that just lists the URLs of the images it can't get, since that might be useful in context of automations - at least more useful than nothing! Meanwhile I'll see if I can reach out to the team with a feature request.

[brigleb]

So I did reach out to the team and all I can say is they are considering this request. For now, I'm afraid we're stuck!