step3/docs/QUESTION_COMPLETION_CREDITS.md

Question-completion credits

This branch introduces credit earning only. It does not impose a question limit, redeem credits, sell products, activate passes, consume exam tokens, or reset QBank progress.

• A successfully stored first answer earns one credit regardless of whether it is correct.
• A repeated answer does not earn another credit.
• A skipped question does not earn credit.
• At most 20 credits can be earned in a rolling 24-hour window.
• Historical attempts are not backfilled.
• GET /api/credits returns the authenticated user's balance and current rolling-window capacity.
• The first-attempt response also includes the updated credit status.

The API is authoritative. Credit grants use the immutable attempt ID as their idempotency key, so retrying the same completed question cannot grant another credit. Credit accounts are included in account export and deletion.