How Auto Train Builds a Plan Around Your Life and Adapts as You Ride

Most training plans hand you a fixed calendar and quietly assume your life will cooperate. Real weeks do not work that way. You travel, you get sick, a meeting eats your Tuesday, and a plan that cannot bend just breaks. Auto Train is our answer: a cycling plan built around the hours you actually have, that adapts to the training you actually do.

Auto Train is a Cave Crew feature. You give it a goal and your constraints, it generates a periodized plan sized to your available time, and then, as you ride, it keeps that plan honest against your real fitness. It always proposes, and never imposes. Here is how it works, and how we tested it before putting it in your hands.

You set the goal, it sizes the plan to your time

When you create a plan you tell Auto Train five things: your event and its date, your discipline, the weekly hours you can realistically train, your current fitness, and your intent, whether you are chasing a peak, building general fitness, returning from time off, or maintaining. Everything else is derived from those answers.

The most important of those is your available hours. A plan that assumes 12 hours a week is useless to someone with 6, and a plan that caps a 12 hour athlete at 6 wastes half their week. So Auto Train treats your stated hours as the thing to fill, not a ceiling to stay under.

Why your hours come first, not a number

Training load is usually summarized as TSS, a single stress score for a ride. TSS is useful, but it is blind to how that stress is distributed. A 3 hour endurance ride and a short, sharp interval session can carry a similar score while taxing completely different systems. One builds your aerobic base and durability, the other sharpens your top end. Treating a single stress number as the target quietly starves the long, easy riding that builds the biggest engine.

So Auto Train starts with your hours and lets the stress score fall out as a readout, rather than the other way around. It fills your week with roughly 2 quality sessions plus aerobic endurance, including one longer weekend ride for durability. When you have more time available, that extra time becomes more endurance, not more hard days. This is the model our design was rebuilt around after a review with a sports physiologist and a cycling coach.

It eases you in, then fills your week

Opening a plan at full volume is how people get hurt or buried. The danger is rarely the total number of hours, it is the size of the jump to get there. Auto Train seeds your starting volume from your current fitness and available time, then ramps you toward your full hours over the first few weeks.

How quickly you ramp in depends on your fitness. A well trained rider can open near their full hours in week one, someone coming back from a layoff opens lower and climbs safely. Either way, everyone reaches their stated hours at the peak of the plan. Your fitness sets how fast you ramp in, not where you end up.

It adapts to the training you actually do

Once your plan is live, Auto Train watches your real training. It reads your fitness as a rolling average of your recent training load, your fatigue as the load of the past week, and your form as the balance between them. This is the same fitness and fatigue framework used across endurance sport, and it is what lets the system reason about whether you are fresh, buried, or building.

Every ride you log counts, indoors here or synced from the services you already use. Auto Train credits each ride against your planned sessions by when you did it and how much work it carried, and it is generous: doing more than planned is never treated as a miss. When your real training drifts from the plan, it rebuilds the weeks ahead from your true current fitness rather than stubbornly holding the original calendar.

It is also deliberately calm. A single missed session is treated as noise, because one off day is noise. It takes a real pattern, several missed sessions, a block of underperformance, or a sustained partial shortfall week after week, before Auto Train proposes a change. And your FTP is sacred: the system will suggest raising it when your riding earns it, and will nudge you to retest if something looks off, but it will never quietly lower your number.

You stay in the loop

Auto Train proposes, you decide. When it has a suggested change, it shows you a clear before and after with the reasoning, and you can skip it, defer it, or apply it. If you want a lighter or bolder version of a change, a simple dial lets you tune it, and that preference sticks as a lasting property of your plan that every future adjustment respects. Whatever you choose stays inside the safety limits below.

There is also a way to check in on the thing the data cannot see: how training actually feels. Four honest options, from really easy to really hard, nudge your plan up or down by feel, with your judgment given the benefit of the doubt. Because Auto Train owns the structure of an adaptive plan, direct edits to future weeks are limited on purpose, since rebuilding those weeks would wipe them. Instead you add extra rides on your calendar, where they still count toward your fitness, and you can drag a session to a different day and have that choice stick.

The guardrails

Every plan Auto Train builds or adapts stays inside a fixed safety envelope. Weekly volume never jumps more than about 10 percent, and it climbs gentler for masters and newer riders. A fatigue floor keeps your form from digging too deep on a hard week. The plan holds to roughly 2 quality sessions a week, so extra time never turns into extra intensity. Regular recovery weeks, a taper across your final 2 weeks into the event, and a hard ceiling on total load round it out. The tuning dial and every adaptation move within these rails, never past them.

How we know it works

Here is the honest challenge with any coaching system: the real proof is athletes finishing plans and arriving fit and fresh, and that data takes seasons to gather. We did not want to ship on faith while we wait for it. So we built the proof we could. We simulate.

At its core Auto Train is a deterministic engine, which means the same inputs always produce the same plan, and that makes it testable at scale. We generate over 1,000 plans across every combination of discipline, experience, intent, weekly hours, and length, and check each one for structural soundness: contiguous weeks, sane loads, recovery on cadence, a proper taper at the end, and clearly different plans for clearly different riders. We run the adaptation logic through dozens of real situations crossed with different athlete profiles: nailing the plan, missing a week, a vacation, an illness, a fitness change, a slow slide of partial weeks, and we confirm it stays consistent, never rewrites the past, never lowers your FTP on its own, and settles instead of oscillating.

The centerpiece is a full season simulator. Virtual athletes emit real ride data week by week, and that data flows through the exact same production code you use: the same crediting, the same fitness math, the same decisions, the same applied changes, for an entire season. Each simulated season is then scored by a completely separate model of fitness and fatigue, so the thing grading the outcome is not the thing being tested. We run a fleet of these, including riders who only record heart rate, who complete about 80 percent of their sessions, who get sick mid block, and who run hot. Across the fleet, every athlete builds fitness and arrives fresh, with comfortable safety headroom.

We also test the tests. Using mutation testing we deliberately break each safety rule, one at a time, and confirm a test catches it, which is how you know your safety net has no holes. We found and fixed 2 that did. A separate adversarial review put dozens of independent checks across every layer and surfaced real issues we fixed before release. All told, the system is covered by more than 4,000 automated tests that run on every change.

Honest about what is proven

We are confident that Auto Train is safe and behaves the way it is designed to, end to end. What no simulation can fully settle is whether it is the single best coach for every real human over a real season, because that genuinely requires real humans over real seasons. That is exactly the gap the simulator stands in for today, and exactly what a careful rollout will fill. Our bar for talking about any of this is simple: every number we cite has to be literally true. Auto Train shows its work rather than claiming to be magic.

Getting started

Auto Train is available to Cave Crew members. Create a plan, tell it your event, your honest weekly hours, and your current fitness, and it will build your calendar. Then just ride. Log your sessions here or sync them from wherever you train, and let Auto Train keep the plan pointed at your goal while you get on with the work.