Old-vs-new text for one change

The section's text before and after this specific change, when available (see hasDiff on the change list above).

How many sides a change has depends on its kind, and each is a complete answer:

• amended -- both sides. This is the only kind where one side alone is not a partial answer but no answer.
• added -- after side only. There is no before side by definition, and the full text of a newly published section is precisely what the notification is for.
• removed -- before side only, the last text we held.

A missing side is not an error: hasBefore/hasAfter say which text is actually present, and diffAvailable (with unavailableReason when false) says whether there is a diff at all, so a caller can render a graceful 'diff unavailable' state for older changes or a snapshot that failed to capture, instead of treating null as a failure.

Cost: 4 credits per call (see /api-credits/pricing). This is the only metered route in the alerts family: every other board and watch endpoint, including the /changes list this reads from, is free.

You are charged only for a diff that answers the question its kind asks, and creditsConsumed always reports what was actually billed. Refunded in full (creditsConsumed: 0): an amended change missing either side, an amended change whose two sides resolve to identical text (a capture artifact on our side, not a change on the publisher's), and any change resolving no text at all. A one-sided added or removed diff is the complete answer and is charged normally.