Private beta
A coach that knows you, not the average athlete.
It reads your training, your recovery and what you tell it every morning, and explains what today should be. You can argue with it.
Resting heart rate · the last three mornings above your usual
Sleep · two short nights in the last seven
Easy eight, strides out
Your body has had a hard time recovering these last few days: resting heart rate up three mornings running, on top of two short nights. Easy eight today, and leave the strides out. Sunday is the priority, and I would rather you arrive there fresh.
The last three marks move with it, and Foil's engine reads the morning again.
An example morning. The band, the reading and the short nights are computed by Foil's own engine from the mornings drawn; the coach's words are examples written for each answer.
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.
Each bar is a phase. Its width is the typical length, its height the typical weekly volume as a share of the peak week.
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 templatesOr build your own
Copy a published approach and reshape its principles, structure and voice in conversation, or start from a blank scaffold. The draft is private until you publish it.
Create your ownGetting started
Your training, with context.
- 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.
- 02
Find your approach
Pinned to youThreshold MarathonVersion 1.1.010 principles · 7 phases
Read a published coaching template and see whether it fits your experience and goal, or copy one and reshape it into your own.
- 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.
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
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
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
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
Built and tested by Alex, the one athlete using Foil today.
The private beta
Foil is currently tested by its founder. Join the list to hear when places open, and 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 listWorks 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.
- Your watch or wearable
- intervals.icu
- Foil's own store, synced every day
- 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 dataBefore 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. The published marathon template assumes at least six months of consistent running; a template you build yourself sets its own bar. Other sports 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?
Yes. Sign in, copy a published approach or start from scratch, and reshape it in conversation. The draft stays private until you publish it and choose it for your own coaching.
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.