Scheduling issues. FSRS Bug in 25.08b5? Or a misunderstanding?

[hnvy]

Hi all,

I tried to look for an answer on the forum, but was not able to find something like this

I optimise the algorithm weekly, and my desired retention is set to 94%:

• Reschedule cards on change is OFF
• Check health when optimizing⁩ (slow) occasionally ON

Anki version 25.08b5 (d4862e99)⁩

Unsure if these things are related to the new release, or if I misunderstood something.

New interval is shorter than the old interval

Example 1

Here is a card that has not been touched by manual rescheduling (notice how my review on 2025-08-15 resulted in a shorter interval):

Parameter	⁨Value
Stability	27 days
Reviews	8
Retrievability	100%
Difficulty	89%

Example 2

Parameter	Value
Stability	⁨1.33⁩ months (⁨41⁩ days)
Difficulty	90%
Retrievability	97%

[mbrubeck]

What is your “desired retention” setting, and did you change it since these cards were last reviewed?

Based on the stability and intervals you showed, it looks like maybe you currently have a high (over 90%) desired retention, which is making your intervals shorter.

[Danika_Dakika]

Between those early-July reviews and now, you’ve upgraded Anki (possibly multiple times), switched from FSRS-5 to FSRS-6, and optimized your parameters a half-dozen times (weekly re-optimization is more often than necessary, and probably why your D values are jumping around so much in your review history). FSRS relies on your parameters, your DR, and the card’s memory state when scheduling – not on the card’s prior interval.

I don’t think you can expect that your new interval will always be longer than the last interval when you’re so frequently changing the things that FSRS relies on.

[pipep]

Hello hnvy,
I’m in the same situation as you. I update Anki whenever there’s an update, and I optimize the parameters once a month. I also have many cards where, in the last review, the interval became shorter and the difficulty increased. As Danika_Dakika said, I think this is normal and mainly due to the transition from FSRS-5 to FSRS-6. Let’s keep observing how these cards behave over the next few months.