How review scheduling works

Overview

Every review in Lexxio, whether it is a vocabulary flashcard or a conjugation drill, runs through one scheduler. When you grade a card, that grade updates two numbers held against it, and the next review date comes out of them.

The algorithm is FSRS. It is the same open-source scheduler Anki uses, and it replaced the older five-box system entirely: boxes are still shown in a few places, but they are a summary of the schedule now, not the thing driving it.

If you never open a setting, it works. Everything below is optional.

The two numbers behind a card

• Stability is roughly how long the memory will last before you are likely to forget. It grows every time you recall the card successfully, and grows faster when you found it easy.
• Difficulty is how hard this particular card is for you. A card you keep missing gets more difficult and its intervals stop stretching so quickly.

A new card has neither until you have reviewed it once.

The four grades

Again, Hard, Good and Easy, on keys 1 to 4. Each button shows the date it would move the card to before you press it, so you are never guessing what a grade does.

Grades are not scores. Answer honestly, including on cards you half-remembered, because a dishonest Good is what produces a deck that feels wrong three weeks later.

Your retention target

This is the one setting worth understanding. It is the probability that you will remember a card at the moment it comes back.

• Higher (say 95%) means shorter gaps, more reviews per day, and less forgetting.
• Lower (say 85%) means longer gaps, fewer reviews per day, and more forgetting.

The default is 90%. There is no correct answer; it is a trade between your time and your recall.

Learning steps

New cards do not jump straight into long intervals. They run through short steps first, written the same way Anki writes them, so 1m 10m means the card comes back a minute after you first see it, then ten minutes later, before it graduates into the real schedule. Relearning steps do the same job for a card you have just failed.

You can also set a maximum interval, so a card you have known for years still comes round occasionally.

Daily limits

Two caps, both yours to set: how many new cards a day, and how many reviews a day. Together they are what stops a heavy reading week from turning into an unmanageable Monday.

There is also a next-day-starts-at hour, defaulting to 4am, so a session that runs past midnight still counts as the same study day.

Leeches

A card that keeps lapsing past your leech threshold gets suspended and surfaced to you rather than quietly eating a slice of every session for the next year.

A leech is usually a sign that the card itself is wrong: two words that mean nearly the same thing, a gloss too vague to recall, a phrase you never actually met in context. Fix the card or drop it. Do not just resume it and hope.

Bury and suspend

• Bury pushes a card out of today's queue and brings it back tomorrow.
• Suspend takes it out of every queue until you bring it back.

Neither one costs the card its schedule. A suspended card resumes exactly where it was.

The optimizer

Once you have enough review history, Lexxio can fit the scheduler's parameters to your memory instead of the library defaults. This runs on your device, using your own review log as the training data. Nothing is uploaded.

It is worth running after a few weeks of real use, not on day one, and running it again every few months. Both tracks, vocabulary and conjugation, train together, because one scheduler serves both.

Grades are logged

Every review is written to a log. That log is what the optimizer trains on, and it is what travels with your deck when you export to Anki.

Note that a grade commits immediately when you press it. There is no undo in a session, so take the extra half-second on a card you are unsure about.