# Sep 26, 2026

Source: https://docs.tightly.io/help/releases/2026-09-26
Reviewed: 2026-09-26

Stock buffers are now sized correctly for long lead times.

## What changed

- [Cover and safety stock](../engines/replenishment) are now sized correctly at every lead time, given an accurate forecast. Before, the buffer for a long-lead item was too thin for the service level you set: at 120 days, a line set to 95% was actually protected to about 76%, and the gap widened the longer the lead time ran.
- The buffer now also grows with how much a supplier's own delivery date moves, read from that [supplier's lead time](../supply/lead-time) on file rather than assumed the same for everyone.
- Because of this, [suggested orders](../supply/suggested-orders) on long-lead items may come back larger than before: the extra units are what holding the declared service level actually costs on those lines, not a change in what you asked for.
- The service level you actually get still depends on how accurate the forecast is and how much a supplier's lead time varies, not on the buffer formula alone. This fix corrects the formula; it does not promise a number the forecast has to earn too.

## Where to read more

- [The replenishment engine](../engines/replenishment)
- [Lead time](../supply/lead-time)
- [Suggested orders](../supply/suggested-orders)