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Private beta · Starting with marathon running

A coach that knows you, not the average athlete.

Foil brings together your training, recovery and what you tell it to help you decide what today should look like. It remembers your context and explains its recommendations.

By joining, you agree to receive beta invitations by email. You can withdraw at any time. No training data is connected. Privacy and deletion

Explore coaching templates

Built and tested by Alex, the one athlete using Foil today.

Resting heart rate · four weeksyour usual band
52 bpm +5 on your usual mean of 47
06:45

Easy eight today. I would leave out the strides: your resting heart rate has been up for three mornings, and Sunday is the priority.

Keep the purpose of the week in view.

The legs feel normal. Does that change your mind?
06:51
06:51

That is useful context. I would still leave them out today: feeling normal does not explain the trend. Keep the easy run, and tell me how it feels afterwards.

Recommendation · keep it easy

Illustrative conversation and example data.

Choose how you are coached

An approach you can understand. A plan that is yours.

A coaching template sets the principles your coach works from. Your goals, training history and available time give those principles context.

The first approach, drawnThreshold Marathon 1.0.0
Base, 4 weeks; Build, 3 weeks; Absorb, 1 week; Peak, 3 weeks; Taper, 11 days; then the race.

Each bar is a phase. Its width is the typical length, its height the typical weekly volume as a share of the peak week.

Three of its rules, as rangesChange in weekly volume, against the week before
Volume grows
up 0 to 10% a week, typically 7%
A hold week
down 10 to 30% every 3 to 4 weeks, typically 18%
The taper
down 41 to 60% over 8 to 14 days, typically 50%

Drawn from the template document itself, so it changes when the template does. Your own block depends on your race date and training history.

Explore the first approach

Threshold Marathon is built for runners who already train consistently. See who it suits, how a training block develops, and the rules behind the coaching.

Explore coaching templates

Or start with your own priorities

Planned

We are working toward building an approach in conversation, starting with your goal, history and constraints. Explore a preview of that experience.

Preview creating your own

Getting started

Your training, with context.

  1. 01

    Bring your training

    Four weeks, as they arrived
    run
    other sport
    rest

    Connect intervals.icu so Foil can read your activities. Sleep and recovery data add context when available; a recovery wearable is optional.

  2. 02

    Find your approach

    Pinned to you
    Threshold MarathonVersion 1.0.0

    10 principles · 7 phases

    Read the coaching template and see whether it fits your experience and goal. The first beta uses a marathon approach for established runners.

  3. 03

    Make the next decision

    Behind one recommendation
    Window
    60-night baseline
    Basis
    your own trailing mean
    Confidence
    medium
    Would change my mind
    back under 49 tomorrow and this clears

    Read your morning recommendation, ask why, and tell the coach what your watch cannot. What you did and what you said become part of the next conversation.

Example weeks and an example recommendation. The template's name, version and counts are real.

What makes it yours

Keep the goal in view. Make today make sense.

Your history matters.

A reading means more alongside your own recent training and recovery. Foil shows the signal and its comparison, without reducing your morning to a score.

The conversation carries on.

What you said about a session stays in the record. You can pick up where you left off, with your goals and previous decisions in view.

Every call has a reason.

Understand what the coach wants to keep, what it proposes changing, and why. A good morning can mean carrying on with the plan.

You have a say.

Your watch does not know how a session felt. Add that context, question a recommendation, and make the decision. Foil records what you chose.

This morning
Resting HR52 bpm +5 on your 3-day mean of 47above your usual
HRV (rMSSD)68 ms inside your usual band of 61–79usual for you
Show what else I looked at
Window
60-night baseline
Basis
your own trailing mean
Confidence
medium
Would change my mind
back under 49 tomorrow and this clears

Example readings on an example baseline, in the product's own components.

The decision is the useful part

When the plan still fits

Ten minutes easy, two six kilometre blocks at race pace with four minutes float between them, ten minutes easy.

4:15/km inside a 35 min set

The recent training and your feedback support today's session.

Keep the session as planned.

A good recovery reading is context, not a reason to add extra work.

When something needs attention

Ten minutes easy, one six kilometre block at race pace, four minutes float, a second six kilometre block dropped, ten minutes easy.

4:15/km inside a 35 min set · Second block dropped.

A recovery signal has shifted across several mornings.

Consider a lighter version.

See the signal, the proposed change and the reason before deciding.

When the watch is missing context

Slept badly and the legs are heavy. What would you do with today?
06:48

The data did not arrive, or the session felt different from the numbers.

Start with what you can tell the coach.

Foil makes missing readings visible and asks for your perspective.

Illustrative coaching situations, not athlete results.

Why I built Foil

I lost about two years to injuries. Not to one stupid session: to a lot of reasonable ones.

Each run made sense on its own. What I wanted was a coach that could put the weeks together, remember what I had told it, and help me make a better decision that morning.

Alex, founder and first athlete

The private beta

Foil is currently tested by its founder. Join the list to hear when places open for marathon runners, or tell us which sport you want to see next.

There is nothing to buy today. A monthly subscription is planned, with pricing shared before you decide to join.

Join the beta list

Works with your training setup

Connect through intervals.icu

Foil reads activities and available recovery data from your intervals.icu account. Check that the activities and readings you want to use are arriving there first.

Overnight sleep, HRV and resting heart rate are optional. Without them, the coach works from your training and what you tell it.

The first coaching template covers running. Cycling, swimming and combined sport coaching are planned.

Where your data goes
  1. Your watch or wearable
  2. intervals.icu
  3. Foil's own store, synced every day
  4. Your coach, reading from the store

Your data, explained

Training and conversations are stored in Foil's database. Relevant context is sent to Anthropic to generate coaching replies. Foil does not sell your data or use it to train models.

How Foil uses your data

Before you join

How is this different from ChatGPT with my training connected?

Foil keeps a training record and works from an explicit coaching template. A deterministic engine checks the numbers; the model explains the findings in your context. Those checks help ground a reply, but they do not guarantee that every coaching recommendation is right.

Who is the first beta for?

Runners with an established training habit who are preparing for a marathon. The first template assumes at least six months of consistent running. Other sports and approaches are planned.

What happens after I join the list?

Your email is saved for beta invitations. You can optionally tell us your sport and goal. Joining the list does not create a coaching account or connect any training data.

What will I need to get started?

An intervals.icu account receiving your activities. When invited, you will connect it and establish your athlete profile and coaching approach. The coach uses the history available and tells you when it does not have enough data for a comparison.

Can I create my own coaching template?

That is planned. You can explore a preview now, including how your available days and preferences could shape the approach. The preview does not create a template or a training plan.

Does the coach decide for me?

No. It explains a recommendation and you decide what to do. You can question its reasoning and tell it how you feel. It can be wrong, and missing data is shown rather than filled in.

Does Foil review and rebuild the whole week?

The beta centres on daily recommendations and conversation. A weekly planning review is planned. Daily coaching can suggest reducing a session or keeping it as planned; it does not add training because of one good morning.

Make room for a coach that knows you.

Join the beta list. We will email when a place opens, with what to expect and any cost before you decide.