Adaptive mastery-streak nudges for learner retention

The brief

The mastery streak is Khan Academy's quiet superpower — a daily learning loop that millions of students use to stay on track. It is also fragile. A student has a busy week, the streak resets, and the system has just penalized exactly the kind of week that needed gentler scaffolding, not more pressure.

The bet: an adaptive nudge layer that personalizes lesson length and mix to each learner's recent energy curve would protect the psychological benefits of the streak without punishing the messy weeks that life actually involves.

What we built

A real-time personalization service that scores each learner's "energy curve" — recent session length, accuracy, breaks, time-of-day patterns — and recommends a daily plan calibrated to what they will probably complete, not what an idealized version of them would. The service returns a plan in under 60 milliseconds, well inside the page-load budget, and is updated continuously as the learner progresses.

The Khanmigo integration was small but important: when a learner is visibly struggling on a recommended item, Khanmigo proactively offers support instead of waiting for the learner to ask. The threshold for "struggling" is itself learned from the learner's own history.

We launched against a tightly-bounded A/B with strict guardrails: no suggested plan can be shorter than what the learner has demonstrated the ability to complete; no streak can be silently extended. The system recommends, the learner decides.

Outcome

14-day retention for opted-in cohorts lifted 19% versus the control. ~1.2 million learners are now enrolled. The personalization service is live in 12 languages.

The most quietly important outcome: cohorts with previously-broken streaks recovered them at a meaningfully higher rate after the launch — the system is doing what it was designed to do, which is to help learners come back after the hard week instead of giving up.

"We did not want to gamify the kid into doing more — we wanted the system to meet them where they were."