Record what changes about each MCP server, and publish changelogs

[lbesecker195]

Closes #73.

The sync re-reads server.json every six hours and the prober re-asks each remote server what it exposes. Both overwrote what they found, so nothing remembered what changed. This keeps the difference and publishes it.

Pages

• /servers/:ns/:name/changelog — every recorded change, grouped by day
• /servers/:ns/:name/changelog/:kind — tools, prompts, resources or server-json alone
• /changelog — the latest 100 changes across the registry, each linking into its listing

Like every other silo, a page exists only once there's something on it: no history redirects to the listing; a kind the listing has none of redirects to its changelog. The listing header links changelog · N only when N > 0. All three are in the sitemap (changelogs-N.xml, and /changelog in pages.xml).

What is recorded

• server.json: taken from the sync's own changeset, restricted to fields the publisher controls (title, description, version, transport, URLs, package, env vars, license, status, icon), stored as old → new.
• tools / prompts / resources: set differences between two probes, kept in the server's own order.

What is deliberately not recorded

A changelog that reports our bookkeeping as the publisher's activity is worse than none:

Not recorded	Why
first sight	a baseline, not an event
declared tools → probed tools	our knowledge improving, not the server changing
prompt/resource lists from before 24 Sep	those probes never asked; "empty" meant "not asked"
any list at the 500-item cap	a server adding one item pushes another off our end — a removal that never happened
sync(reapply: true)	changes how we read upstream, not what was published
a probe whose write failed	the change is written only after the row it describes

A database check constraint enforces that every change is about exactly one subject — a listing now, a document URL once llms.txt/AGENTS.md land in the follow-up.

Cadence

Probes now recur every 7 days rather than 14, so a changelog is at most a week behind its server: ~3,000 endpoints a day against a scheduler that can ask ~28× that.

Tests: 207 passing on three seeds, including integration through a real probe batch and a real sync.

---

Pages affected:

• MCP server changelog -- latest tool, prompt, resource and version changes.
• MCP Harbor -- registry home and server search.
• MCP server directory -- every listing links its own changelog.

🤖 Generated with Claude Code