# What happens when the borrow index stops updating, and how far linear adaptation can run

Mentorship Series #24 · 15 January 2026 · [@0xfirefist](https://x.com/0xFireFist) · Panoptic · Code4rena

Mentorship Series · [The Contest Academy](https://0xsimao.com/the-contest-academy) · 0xSimao

---

We continued the Panoptic [contest](https://code4rena.com/audits/2025-12-panoptic-next-core) on Code4rena.

**Lesson Summary:**

- When the user doesn't have enough balance, his index is not updated. What happens if the user deposits more afterwards?
- 100 USDC, user has only 50 balance. They burn this 50 balance, index is not updated. If he deposits 100 again, how much is he going to pay? Will he have to pay 50 shares of interest, because he paid 50 already, or will he have to pay 100 again, totalling 150?
- Is there a health check in the Pool?
- What if linearAdaptation is not zero but is very small?
- How big can linear adaptation get?
- If called every block, the linear adaptation should be small. What happens to the rate? Is there a maximum rate? max speed?

https://youtu.be/Jstc_1gJJ54

Session video: https://youtu.be/Jstc_1gJJ54

---

Newer: [Simulating full accrue sequences: index desync and epochs versus block.timestamp](https://0xsimao.com/the-contest-academy/mentorship-series-25) · Older: [Precision in the trapezoidal borrow-rate curve, and the Yearn post-mortem behind it](https://0xsimao.com/the-contest-academy/mentorship-series-23)