Do I have to quit Hevy or Strong?

No. IronStack reads a file you export; it never signs in there or changes anything. Run both for a couple of weeks. If you go back, your app is exactly as you left it. One honest limit: IronStack exports your log as a documented JSON file, not a Hevy or Strong CSV, so workouts you log here will not load into them on their own. If an unbroken Hevy history matters to you, log in both while you try it.

What comes over from Hevy?

Workouts and routines (routines come in as saved workouts), with supersets paired the way Hevy paired them, warm-ups as prep sets and drop sets tagged as what they were, and your custom exercise names kept exactly. The preview shows what it found, and any names it wants you to check, before anything is saved. In Hevy: Settings, Export & Import Data.

Apple's own app for beta testing. I add your Apple ID email, Apple sends you an invite, and TestFlight installs IronStack like an App Store app. Updates arrive through it until 1.0 lands in the store.

Logging in IronStack is free. Every app has a free way in, plus paid plans. Stack AI runs on a monthly allowance, because every Stack AI question runs on a server I pay for. Pricing coming soon: it lands on this page before it lands in the store.

Does it need an account?

Not to log. Everything you log is a file on your phone. Social is the one part that needs you to be someone, and it uses Sign in with Apple without asking for your name or email. Skip Social and there is nothing to sign up for.

What leaves my phone?

Nothing goes to Anthropic until you turn Stack AI on, and then only what you send it, when you ask. The cards you choose to share with your spotters, if you use Social. Nothing else unless you switch it on. The privacy page says exactly what, where, and for how long.

Can I bring my history?

Yes. Hevy and Strong exports bring history and routines; JuggernautAI and any spreadsheet you kept bring history, with a preview to match the columns. Imported workouts count in your records, Insights and "last time", are labelled as imported, and never go on a card. Bringing the same file twice adds nothing.

Both. Pick one for the app, and switch any single exercise the other way, because the dumbbells at a hotel gym do not care where you live. The keypad shows the other unit under every number, and one tap types in it.

A weekly streak on Insights and badges that take years to finish: Road Warrior for training on the road, Dawn patrol, a thousand feet of carries, In their corner for supporting others. Earned, never shamed. Miss a week and nothing scolds you.

Is Stack AI a doctor?

No. It is an AI, and it can be wrong. It answers from your own sets, never names a weight above a ceiling it can show you, and points any question about pain or injury to a qualified person. Nothing it suggests changes your log until you tap.

Apple Watch, Android, iPad?

Apple Watch, yes. The watch app comes with the iPhone app (watchOS 26 and up), and it is a remote for the workout on your phone: start on either one, and both show the same set. The watch shows the set you are on and the clock, a swipe apart: tap the weight, reps or RPE and turn the Crown to change it, tap Log set to log, and tap the clock to pause the rest. A timed set runs its timer there too, and after the last set you finish from your wrist. The whole workout lands in Health as one, with heart rate. Keep your phone nearby, in a bag or on the bench; if the watch loses it, the clock keeps running and what you logged is sent when it reconnects. Coming soon: the watch runs the whole workout even when your phone is out of range. No Android and no iPad layout yet.

Training with a real person who also uses IronStack. Your coach invites you with a link or a code; nothing is shared until you say yes, and you choose what they see: every set always, your notes unless you turn them off, and sleep, bodyweight and MealStack fueling only if you switch them on. Their plans arrive as suggestions. Either of you can end it, and their copy goes with it. Coach mode is open to everyone in the beta; if you train with a coach, say so when you sign up.

Is Stack AI my coach?

No. Coach means a person. Stack AI is the AI: it picks weights from your own sets under a ceiling, writes down a program you already have, and builds a workout or a program when you ask. On a coach's plan, a new program is only ever a suggestion for your coach.

How old do I have to be?

Eighteen, the same as MealStack. IronStack, Stack AI and Social are for adults.

No. IronStack is a closed app. Your data is open: one tap exports everything in the Mission Built Schema, and it imports back. The IronStack name and marks stay with Mission Built.

Coming soon, planned for January.

An iPhone app by Mission Built

IronStack.

Private beta iPhone + Apple Watch

Log fast. See progress. A coach in your corner. A lifting log that brings your history, talks you through rest, and stays out of your way.

Join the beta → Coming from Hevy or Strong? ↓

Logging in IronStack is free · Keep the app you use now · Your whole log exports any time

Runs on

iPhone+ Apple Watch · iOS 26 and up

From any app

Bring itsupersets, prep sets

Account to log

NoneSocial is optional

Logging

One tapLogging in IronStack is free.

Coming from Hevy or Strong

Bring your history. Keep your app. Try it for two weeks.

Bring it

All of it comes over.

Export from Hevy (Settings, Export & Import Data) or Strong (Settings, Export Data) and open the file in IronStack, or bring any spreadsheet you kept. Workouts, routines as saved workouts, supersets paired the way you paired them, prep sets and drop sets tagged as what they were. Names it knows are matched; names it does not are kept exactly as you had them. A preview shows what it found before anything is saved.

Keep your app

Nothing here needs you to quit.

The import reads a file you exported. It never signs in to Hevy or Strong, never touches your account, and bringing the same file twice adds nothing. Run both for a couple of weeks and keep whichever earns it.

Tap, type or say it

You never have to talk to it.

Last time's weight and reps are already in every set, so most sets are one tap to confirm. Or type 225x8 in the one field. Voice is there for the days your hands are covered in chalk, and only while you hold the button.

JuggernautAI history comes over the same way. What it will not do yet: Android or exercise videos. If you need those, keep the other app for them.

What it does differently

Six things a logging app should have done already.

Every screen here is the real app on my phone, with my own training behind it. Social is the app's sample feed, because my spotters' workouts are theirs to share, not mine.

IronStack Today before the start: Shaw Elite week 3, day 1 of 4, Heavy lower with Change, Comp Deadlift first up at 225 for 8, and one Start workout button.

Logging · Chalk on your hands

Tap it, type it, or say it.

Last time's numbers are already in the set: tap to confirm. Changed something? Type 225x8 @7 in the one field. Or hold the talk button and say "two twenty five for eight at seven"; "same again" and "switch to hack squat" work too. Speech is turned into text on the phone, offline, and only while you hold the button. Logged the wrong set? Swipe left on it and Unlog puts it back to planned. Rack taken? Swipe left on the exercise and Swap it, for today or for every time.

Other apps: Tap the numbers in, set by set, with a keypad.

The IronStack rest clock at 0:02: the top of the screen solid oxblood, with the squares row under it.

The clock · Chalk on your hands

A rest clock you can read from the platform.

The set is logged and rest starts itself, at the length the program asked for. With earbuds in, a recorded voice calls "Thirty seconds", "Five seconds" and "Get to work", and your music dips under it and comes back. Voice, buzz or off, and it minds the silent switch. On screen the last ten seconds go oxblood and the last three fill the top and beat. On the Lock Screen, "same again" logs another set like the last without unlocking the phone. A timed set, a plank or a carry, gets a timer: tap to start, and at zero it holds the time until you log. It never logs for you.

Other apps: A timer that buzzes, and a phone to unlock to log the next set.

IronStack Plan: one search for programs, workouts and exercises, Your program Shaw Elite with Heavy lower next and Start Heavy lower, then Other programs and Workouts that need no program.

Plan · Capture cannot fail

Bring the plan you already have.

Programs, workouts and exercises, on one tab: a program holds its workouts, a workout holds its exercises, and one search finds all three. Bring your history over from Hevy, Strong, JuggernautAI or any spreadsheet you kept, send Stack AI a photo or PDF of your program and it writes it down, or save today's workout to do again. Workouts hold your targets, 3 × 8 · 135 lb, and next time last workout's numbers are already in every set. Logging becomes confirming.

Other apps: Routines and custom exercises capped on the free tier.

IronStack Insights on my own log: 7 workouts in 4 weeks, 30 percent down on the 4 before, a weekly streak with the longest at 40 weeks, 2 records in 90 days, and 13.8 million pounds all time across 650 workouts.

Insights · You against you

Every number is you against you.

Workouts this month against last, your estimated max over twelve weeks, records by name, a progress line on every exercise, and how you lift on the days you feel good against the flat ones. Measured against your own log and nobody else's. When the data is thin, it says so instead of guessing.

Other apps: Graphs, only the last three months of them on Hevy's free tier. Working out what they mean is your job.

IronStack Social before you sign in: a sample Bench day card with a heaviest triple and two new badges, supported by spotters.

Social · Lift each other up

A quiet way to share with the people you train with.

Invite a training partner by text. Share a workout as a card: time, sets, the best thing you did. No strangers, and no comments, on purpose: the one thing to give is support, and you see who gave it. If your crew lives in the comments, this is not trying to replace that. Social is optional, and nothing else here needs it.

Other apps: Followers, strangers, likes and comments.

Stack AI in IronStack, turned on and waiting for a question: it reads what you have logged and answers, nothing it suggests changes your workout until you tap it, every weight comes from your own sets, and under the box the line Stack AI is an AI and can be wrong.

Stack AI · You against you

An AI with a ceiling.

Turn it on, then ask what to open at, what covers a taken rack, or how today went. Send it a photo or PDF of the program your coach wrote and it writes it down for you to check. Every weight it names comes from your own sets, under a ceiling it can show you, with the set the ceiling came from. Nothing it suggests changes your workout until you tap it. Not a doctor, and it says so.

Other apps: A chatbot that invents a number, or no number at all.

More of the app

IronStack on Apple Watch: an EMOM clock at 0:39 in round 1 of 10, heart rate 128, the set up now (Box squat 275 × 3), and Restart round and End. — Apple WatchRest, EMOM and the timer for planks and carries, on one screen you can read mid-set. A tap on your wrist at 30 seconds, two at 5, a long one at the end, and the voice in your earbuds when you want it. It never logs a set for you.

IronStack Home: the Mission Built header, Today with Heavy lower and a Load it button, Your people, and Progress. — HomeToday first: what is on the docket, loaded in one tap. Then your people, who lifted you, your progress, and Stack AI.

IronStack Comp Deadlift: Powerlifting, Hamstrings, then Add to a workout with Today's workout first, the four days of Shaw Elite, and A new workout. — An exerciseAdd any exercise to today's workout or to a day of your program, in one tap.

IronStack Progress: every exercise with its sparkline and the change. — ProgressEvery exercise you have done, with its line and the change.

IronStack Log a set for Comp Deadlift: Loaded, Barbell 45 lb, the bar drawn with its plates, 45 bar + 90 per side, 225 lb for 8, and an RPE row above Log. — The set sheetThe load card fits the lift: a barbell drawn the way it is loaded, 45 bar and 90 per side, plates a tap each, RPE in one row.

IronStack Today on a Strongman circuit, Shaw Elite W3 D4: Circuit, Round 1 of 4, with Ungroup, and Log Clean and Press first, 70 for 5 from the plan with Log lit, last time 100 for 5 at RPE 7.5. — A circuitExercises done together, on one rail with the round. Log one and the next is up; Ungroup in one tap.

IronStack Settings: Remind me to train, training days Wednesday and Friday, and a workout time of 6:55 PM. — Training daysYour training days and workout time. Today plans from them, and MealStack can follow.

IronStack Workouts: each workout with its program day, time, working sets and top sets, and a record called out by name. — WorkoutsEvery workout, searchable, records called out by name.

Why it exists

A set that happened gets written down.

The first IronStack lived on my laptop, and it was good at telling me what a week meant. Then one day I named an exercise it had never heard of, and it would not take the set. A log that can refuse a set you did is not a log.

So I rebuilt it around one rule, and put it on my phone, because the rack is where the set happens and my hands are covered in chalk. I wanted a log that takes whatever you did, reads the clock to you, and treats the people you train with as partners rather than an audience. Four ideas hold up everything it does.

01Capture cannot failA set you did is a fact. A name the app does not know is kept exactly as you said it, never refused.
02Chalk on your handsTap, type or say the set. Big targets. A clock you can read from the platform and hear in your earbuds.
03You against youEvery number is measured against your own log. No leaderboards, no strangers, no one else's PR.
04Lift each other upOnly the people you invite. Cards carry no comments, and a name you type is checked before it goes. The one thing you can give is support.

How you use it

Open it, log the first set, get on with it.

01
Bring your history, or just start.
Coming from Hevy, Strong, JuggernautAI or a spreadsheet? Export, open the file, and the preview says what it found before anything lands: workouts, saved workouts, and names to check. Or skip it and log your first set. That starts the workout.
02
Log it. Time it.
Tap the number that is already there, type it, or say it. Rest starts itself. Bodyweight comes from Apple Health if you let it, and you can always type over it. Tap the weight to change it; the keypad converts pounds and kilos on the spot.
03
Stacked.
Finish and the workout closes on what mattered: time, working sets, records by name, a badge if you earned one. Share the card with your spotters, or don't. Next time, today's lifts are waiting with what you hit.

And the rest

An exercise is not always a lift: the collection covers barbell, machines and bodybuilding, conditioning (twenty minutes on the air bike is a workout too), Pilates, barre and yoga, and strongman, browsable by muscle group, with search that finds "low impact" or "hotel" as well as a name. Every exercise has a load card that fits it: a loaded bar with plate math, a fixed bar, a stack, bodyweight or a band. Plate math switches itself off for cables, machines, dumbbells, kettlebells and bands. Home or Away on Today for workouts on the road, flipped by hand or automatically when you are far from home, and shared with MealStack if it is on the phone. A Home Screen widget, and badges that grow with you over years, not just the first week. Apple Health fills in your weigh-in, and can take each workout as strength training. Your whole log exports in one file, in a documented format, any time.

Side by side

Next to the app you use now.

Written against Hevy's and Strong's free tiers as of September 2026, and Hevy Coach as of October 2026. If a line is wrong, tell me and it changes.

Other appsIronStack

Logging a setTap the numbers in, or check off last time's.The same, plus type 225x8 in one field, or say it.

RestA timer that buzzes.Starts itself, calls "Thirty seconds", "Five seconds" and "Get to work" in your earbuds, and fills the screen at the end.

A new exerciseMake a custom one first; the free tier allows seven.Say or type any name. It is kept exactly as you said it. Match it later, or never.

What is freeEvery workout, but four routines and three months of graphs.Logging in IronStack is free. Every app has a free way in, plus paid plans. Pricing coming soon.

SocialFollowers, strangers, likes and comments.Only partners you invite. Support, no comments, on purpose.

CoachingHevy Coach, a separate app for trainers; clients log in Hevy.Coach mode, inside IronStack: the plan comes in as a suggestion, workouts go out, every change from the plan is marked. Open to everyone in the beta.

Best atAndroid and exercise videos.No Android. Demos are testing on 4 lifts now, with every lift by January. Keep the other app if you like; nothing here needs you to quit it.

The fine print, in plain words

Your data, and one thing I have not picked.

The code

Closed app. Open data.

IronStack is a closed-source app from Mission Built. What is open is your data: everything you log exports in one file in the Mission Built Schema, a documented, versioned format, and imports back in. The IronStack name and the marks stay with Mission Built.

Price

Pricing coming soon.

Logging in IronStack is free. Every app has a free way in, plus paid plans. Every Stack AI question runs on a server I pay for, so Stack AI is where the paid plans come in. The prices land on this page before they land in the store.

Your data

On your phone. Yours to take.

Your log is files on your phone, and one tap exports all of it in the Mission Built Schema, a documented, versioned format. Stack AI is off until you turn it on, and Stack AI and Social send only what they need to work. One screen deletes everything, everywhere, and tells you what it deleted. The privacy page says exactly what, where and for how long.

Not a doctor. Not your programmer.

I am not a coach or a clinician, and nothing on this page or in the app is advice about how you should train. IronStack is how I log my own. Stack AI is an AI and can be wrong: it gives a starting weight under a ceiling it can show you, a cue from your own notes, or an alternative when the rack is taken. It writes down the program you send it and never makes one up, and any question about pain or injury gets pointed to a qualified person.

Join the beta

Private beta, on iPhone.

On TestFlight now, with outside testers

Newest build: IronStack 0.1.1 · Build 77

IronStack logs every workout I do, and a small group of outside testers is on it with me. New testers come in small batches, added by hand from the email on your Apple ID, and I would especially like people coming from Hevy or Strong, and training partners who want to try Social together.

You get an email from TestFlight, Apple's own app for trying apps before they reach the App Store: install TestFlight, tap the link, and IronStack installs like any other app. Keep Hevy or Strong on your phone the whole time. The address is used for the invite and nothing else.

Training with someone? Sign up together and put their name in the note, and I will add you in the same batch.

Beta

By invite, from the form. Small batches, added by hand.

Now

App Store

The public door, published by Mission Built.

After the beta

Questions

The ones I get asked.

Do I have to quit Hevy or Strong?: No. IronStack reads a file you export; it never signs in there or changes anything. Run both for a couple of weeks. If you go back, your app is exactly as you left it. One honest limit: IronStack exports your log as a documented JSON file, not a Hevy or Strong CSV, so workouts you log here will not load into them on their own. If an unbroken Hevy history matters to you, log in both while you try it.
What comes over from Hevy?: Workouts and routines (routines come in as saved workouts), with supersets paired the way Hevy paired them, warm-ups as prep sets and drop sets tagged as what they were, and your custom exercise names kept exactly. The preview shows what it found, and any names it wants you to check, before anything is saved. In Hevy: Settings, Export & Import Data.
What is TestFlight?: Apple's own app for beta testing. I add your Apple ID email, Apple sends you an invite, and TestFlight installs IronStack like an App Store app. Updates arrive through it until 1.0 lands in the store.
Is it free?: Logging in IronStack is free. Every app has a free way in, plus paid plans. Stack AI runs on a monthly allowance, because every Stack AI question runs on a server I pay for. Pricing coming soon: it lands on this page before it lands in the store.
Does it need an account?: Not to log. Everything you log is a file on your phone. Social is the one part that needs you to be someone, and it uses Sign in with Apple without asking for your name or email. Skip Social and there is nothing to sign up for.
What leaves my phone?: Nothing goes to Anthropic until you turn Stack AI on, and then only what you send it, when you ask. The cards you choose to share with your spotters, if you use Social. Nothing else unless you switch it on. The privacy page says exactly what, where, and for how long.
Can I bring my history?: Yes. Hevy and Strong exports bring history and routines; JuggernautAI and any spreadsheet you kept bring history, with a preview to match the columns. Imported workouts count in your records, Insights and "last time", are labelled as imported, and never go on a card. Bringing the same file twice adds nothing.
Pounds or kilos?: Both. Pick one for the app, and switch any single exercise the other way, because the dumbbells at a hotel gym do not care where you live. The keypad shows the other unit under every number, and one tap types in it.
Streaks and badges?: A weekly streak on Insights and badges that take years to finish: Road Warrior for training on the road, Dawn patrol, a thousand feet of carries, In their corner for supporting others. Earned, never shamed. Miss a week and nothing scolds you.
Is Stack AI a doctor?: No. It is an AI, and it can be wrong. It answers from your own sets, never names a weight above a ceiling it can show you, and points any question about pain or injury to a qualified person. Nothing it suggests changes your log until you tap.
Apple Watch, Android, iPad?: Apple Watch, yes. The watch app comes with the iPhone app (watchOS 26 and up), and it is a remote for the workout on your phone: start on either one, and both show the same set. The watch shows the set you are on and the clock, a swipe apart: tap the weight, reps or RPE and turn the Crown to change it, tap Log set to log, and tap the clock to pause the rest. A timed set runs its timer there too, and after the last set you finish from your wrist. The whole workout lands in Health as one, with heart rate. Keep your phone nearby, in a bag or on the bench; if the watch loses it, the clock keeps running and what you logged is sent when it reconnects. Coming soon: the watch runs the whole workout even when your phone is out of range. No Android and no iPad layout yet.
What is Coach mode?: Training with a real person who also uses IronStack. Your coach invites you with a link or a code; nothing is shared until you say yes, and you choose what they see: every set always, your notes unless you turn them off, and sleep, bodyweight and MealStack fueling only if you switch them on. Their plans arrive as suggestions. Either of you can end it, and their copy goes with it. Coach mode is open to everyone in the beta; if you train with a coach, say so when you sign up. What Coach mode shares →
Is Stack AI my coach?: No. Coach means a person. Stack AI is the AI: it picks weights from your own sets under a ceiling, writes down a program you already have, and builds a workout or a program when you ask. On a coach's plan, a new program is only ever a suggestion for your coach.
How old do I have to be?: Eighteen, the same as MealStack. IronStack, Stack AI and Social are for adults.
Is the code open?: No. IronStack is a closed app. Your data is open: one tap exports everything in the Mission Built Schema, and it imports back. The IronStack name and marks stay with Mission Built.
When is 1.0?: Coming soon, planned for January.

At the table

For the data nerds: your log is files.

The phone is where the set gets written down. What you do with the record after that is up to you: it leaves the app as plain files, in a published format, whenever you ask, and any tool you like can read them.

The log

An append-only file per day, one event per set, that the app writes and nothing rewrites. Corrections are new lines, never edits. Export the raw log in Settings hands it over as it is, one line per event.

The export

Export all my data writes one file in the Mission Built Schema: every workout and set, your programs, saved workouts and exercises, and your units. Map coordinates only if you switch them on. Anything that reads JSON reads it, and Bring in data takes it back on a new phone.

Any tool

A spreadsheet, a script, a notebook, a database, or the dashboards you already run. I index mine into Elasticsearch and read it in Kibana: how heavy a week was, whether I am ramping, what I have been neglecting. That is a choice, not a requirement; the file works the same in whatever you use.

For testers

The fine print.

Also from Mission Built

The other half of the book.

Log it · Time it · Lift each other up

Stacked.