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⏺ Read src/billing/invoice.ts (412 lines)
⏺ Grep "applyProration" — 14 matches in 6 files
⏺ Read src/billing/proration.ts (238 lines)
⏺ Edit src/billing/proration.ts
  - const cycleDays = 30;
  + const cycleDays = daysInCycle(period);
⏺ Bash bun test src/billing
  ✓ 128 pass, 0 fail (4.2s)
⏺ Edit src/billing/invoice.ts
⏺ Read src/webhooks/stripe.ts (601 lines)
⏺ Grep "invoice.finalized" — 3 matches
⏺ Edit src/webhooks/stripe.ts
⏺ Bash bun test
  ✓ 342 pass, 1 skip (11.8s)

## Summary

Fixed the proration bug where mid-cycle upgrades were
billed against a fixed 30-day cycle. Root cause: the
cycle length was hardcoded, so February upgrades
overcharged by up to 7%. Changes:

- proration.ts: derive cycle length from the period
- invoice.ts: pass the billing period through
- stripe.ts: re-fetch the invoice after finalization

(1,800 more lines)
⏺ Read src/billing/invoice.ts (412 lines)
⏺ Grep "applyProration" — 14 matches in 6 files
⏺ Read src/billing/proration.ts (238 lines)
⏺ Edit src/billing/proration.ts
  - const cycleDays = 30;
  + const cycleDays = daysInCycle(period);
⏺ Bash bun test src/billing
  ✓ 128 pass, 0 fail (4.2s)
⏺ Edit src/billing/invoice.ts
⏺ Read src/webhooks/stripe.ts (601 lines)
⏺ Grep "invoice.finalized" — 3 matches
⏺ Edit src/webhooks/stripe.ts
⏺ Bash bun test
  ✓ 342 pass, 1 skip (11.8s)

## Summary

Fixed the proration bug where mid-cycle upgrades were
billed against a fixed 30-day cycle. Root cause: the
cycle length was hardcoded, so February upgrades
overcharged by up to 7%. Changes:

- proration.ts: derive cycle length from the period
- invoice.ts: pass the billing period through
- stripe.ts: re-fetch the invoice after finalization

(1,800 more lines)