Auto-Announcing Posts to Bluesky and Mastodon (and Closing the Loop)

The standard answer for discussion on a static site is: pick a third-party comments service, embed it, and accept the dependency. I didn’t want to do that — not because it’s wrong, but because the conversation was already going to happen on Bluesky and Mastodon anyway. I just wanted to link it back.

So I built a script that does it automatically.

What it does

When a new post merges to main and deploys, a GitHub Actions workflow fires. It runs scripts/announce.mjs, which:

1. Checks git diff for newly added .mdx files in src/content/blog/ and src/content/projects/
2. Parses the frontmatter to get the title, excerpt, and image
3. Posts to Bluesky and Mastodon — with the cover image attached if one exists
4. Takes the social post URLs from the API responses
5. Writes those URLs back into the file’s frontmatter as blueskyUrl and mastodonUrl
6. Commits and pushes the updated file

On the post page, I check for those frontmatter fields and render discussion icon links at the bottom. If neither URL exists — old posts, drafts — the footer just doesn’t show up.

The loop problem

The commit-and-push at the end of the script triggers the Deploy workflow, which would trigger Announce again. Infinite loop.

The fix is a single condition on the Announce workflow:

if: |
  github.event.workflow_run.conclusion == 'success' &&
  github.event.workflow_run.actor.login != 'github-actions[bot]'

If the push came from the bot, skip. One pass only.

Why not a comments system

There are solid options for this — giscus uses GitHub Discussions, utterances uses issues, Disqus is Disqus. They work. But they add a third-party embed to every page, and the discussion ends up in a widget that most readers never interact with through the site anyway.

The social feed is where the conversation was already going to happen. This just makes that explicit — and links it back from the post so it’s easy to find.

One edge to know about

The script fetches the cover image from the live site before uploading it to each platform. That means there’s a small window after deploy where the image might not be up yet. In practice the image has always been available by the time the announce step runs, but it’s a soft dependency worth knowing about.