[TheMeinerLP]

Proposed changes

Before Quelea goes onto the live proxies (Proxy-1, Proxy-2), we want to hear about failures without reading proxy logs
on mc01 or pod logs. Today an error only shows up in logs and as an error span in Tempo, and nobody is notified. On
2026-10-28 the team proxy failed TLS for an hour, and only a manual Tempo search found it.

We already run a self-hosted Sentry that Titan, Cygnus and Sturnus report to, and this proposal reuses it for Quelea.
The backend reports its errors, and the velocity plugin reports its unexpected failures. Expected answers such as a
missing party or a conflict stay out of it, and no personal data is sent: no IP addresses, no player names or UUIDs,
no request headers. Without a configured DSN, reporting is off.

What the proposal decides:

• Errors only. Performance data and traces stay in Tempo, as principle 4 already says, so there is no Sentry tracing.
• The velocity plugin reports a lasting event-stream outage once, not on every retry, and does not report a network
  hiccup that the retry already recovered.
• Principle 4 in openspec/config.yaml is amended to name Sentry as the one place where errors, and only errors, are
  additionally reported.

The code follows in a separate pull request, feat(observability): report errors to sentry, once this proposal is
merged. The Kubernetes secret and the CloudNet template are wired by separate changes.

Types of changes

Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

This pull request contains only the OpenSpec proposal under openspec/changes/add-error-tracking/ and the amended
principle 4 in openspec/config.yaml. No code. Tasks are unchecked; they are ticked in a follow-up pull request.
Design decisions with rejected alternatives are in design.md (D1 to D5).