Different scheduling intervals with FSRS 5 and the FSRS helper addon

[mdraves]

I’m using the anki 24.10 RC, and I’ve noticed that FSRS 5 and the FSRS helper addon often calculate different due dates for cards. The FSRS helper addon tends to schedule cards earlier than the normal anki FSRS 5 scheduler.

I tested by rescheduling the cards I reviewed today, and about 80% of them had their interval changed (all shortened by a few days, with the exception of 1 very new card which increased).

Here’s a sample:

The main reason I am even using the addon to reschedule is because I am using anki on both desktop and ankidroid on mobile, and I turned on the “reschedule cards reviewed on other devices” option because I thought it would make cards I reviewed in ankidroid get rescheduled according to FSRS 5.

But I noticed this issue after I did reviews on one computer, and opened anki on another computer later. Many cards were rescheduled with shorter intervals, which meant I suddenly had some cards that were “overdue”.

Is this expected behavior? Is the normal FSRS 5 scheduler or the FSRS-helper addon more “accurate”?

Should I stop using the FSRS-helper addon with FSRS-5? Rescheduling with the helper seems to increase my daily load by about 15%, which is kind of a drag if it’s not actually improving retention.

P.S. I did find this old topic that is related, but I am not sure if the issue has the same root cause, since Sherlock did update the addon in response to the report: Due date and interval changed after rescheduling with FSRS Helper Addon

[sorata]

It’s in the range of fuzz (±5%) so you probably shouldn’t worry about it.

Fuzz: A random delay added to make reviewing more random and natural in Anki. We now also do native load balancing along with it which tried to equalise the daily load you have with Anki.

[L.M.Sherlock]

Anki 24.10 RC introduced “smart fuzz (load balancer)”. FSRS has its own load balancer. So they would be inconsistent.