---
title: "Training"
description: "Why changes wait, what a train does, and why checking happens after it goes live."
source: https://hiy.ai/docs/training
---

# Training

**Train** is where everything you have added becomes something your twin can
actually answer from. Adding a source doesn't change what your visitors get.
A train does.

The Train stage tells you how many changes are waiting, lets you choose what
the next one includes, and starts it. The sidebar carries the same count, so
you find out there is something waiting without going looking for it.

With no material there is nothing to train, and the stage says so: it shows you
four ways to add your first material, on that page, instead of a train that
would build an empty index.

## Changes wait for a train

Adding, editing or removing a source no longer rebuilds your twin on the spot.
The change is stored and counted straight away, and it joins what your twin
knows at the next train.

Two reasons, and the first is the one that matters:

- **Nothing changes what your visitors get without you.** A twin you have
  shared keeps answering exactly as it did until you — or tonight's train —
  say otherwise.
- **A rebuild is all-or-nothing anyway.** Every train rewrites your whole
  index, so a day's worth of changes cost the same as one. Waiting is what
  makes them share the ride.

While a change is waiting, its row in [Sources](/docs/sources) carries a
**Waiting** chip, and asking your twin about it can still get an honest *I
don't know*. That is the change waiting, not your twin failing.

**Two things don't wait,** because waiting would mean knowing nothing at all.
Your twin's very first material is built immediately — a twin with no index
answers nothing, and "your twin knows nothing until tonight" isn't a product
working slowly. A [bulk import](/docs/sources) also trains once at the end by
itself, because "import this archive" is already a batch.

## It trains itself overnight

**Trains run by themselves, during the night where you are.** Whatever is
waiting at that point is gathered into one rebuild, and it is done by morning.
You don't have to come back to this page for it to happen.

hiy takes your timezone from your browser when you open the dashboard, and
follows you if you move — there is nothing to set and no schedule to pick.

**Train now** is there, on any twin with material, if you don't want to wait
for tonight. It starts
straight away and takes minutes rather than hours, and it is the right button
whenever the difference matters now: you have just removed something, or you
want to see the effect of a change before you tell anyone about it.

## Checking happens after it goes live

This is the part worth reading twice.

**The moment a train finishes, the new index is the one your twin answers
from** — for you in test chat and for every visitor, at the same time. Test is
a check you run afterwards. It is not a gate in front, and nothing waits for
your approval.

So the honest consequences:

- **There is no draft index.** A train that makes something worse is fixed by
  changing your material and training again, not by rolling back — the swap
  replaces the previous index rather than sitting beside it.
- **For a twin you have already shared, treat a train as publishing.** If you
  want to see a change before anyone else does, the moment to look is straight
  after the train, not before it.
- **Your [saved questions](/docs/saved-questions) re-run themselves.** Because
  a finished train is already answering visitors, hiy re-runs your whole saved
  set against the new index the moment training ends — automatically, on the
  server, whether or not this page is open. When it is done the Train stage
  says what it found: *"2 of 12 saved questions no longer match what you
  expected."* You are not charged for it: it is not a message off your
  allowance and not a train off your month.
- **What "no longer match" means, exactly.** Each saved question records one of
  two behaviours you expect — answered from your sources, or honestly declined
  — and the re-run records which one actually happened. A row that no longer
  matches did the other thing. It is not a comparison of wording: hiy never
  grades how an answer sounded.

A train that **fails** is the one case where nothing changes at all: the
previous index keeps answering the whole time, because the swap only happens at
the end of a build that worked. [Sources](/docs/sources) explains what you see
when one runs out of retries.

## Choosing what a train includes

**Choose what to train** opens the tick list: everything waiting, ticked, with
its word count. Untick anything you would rather your twin did not answer from.

- **Unticking holds it back, and holding back is sticky.** A held source stays
  in your list, reads **Held back**, and stays out of every train until you
  tick it back on. It is not waiting for anything.
- **Held material costs you nothing.** It doesn't count towards the words and
  sources your plan holds, which is what makes unticking a real way back under
  a limit rather than a gesture.
- **Ticking one back on queues it** like any other change, so the next train
  picks it up.
- **A source you deleted is listed but not tickable.** It is on its way out and
  there is no keep-it option here: unticking a removal would hold it back, and
  a held source is left out of the build too, so it leaves the index either way.
  It is shown because you should see it going.

**Ticking chooses what your index contains, not how much work runs.** Every
train rebuilds the whole thing — ticking six sources does not mean six sources'
worth of work, and the panel says so before you start one. That is also why a
train with nothing waiting is still offered: it is a rebuild of everything, and
sometimes that is exactly what you want.

## What the panel tells you before you start

**See what this changes** replaces the tick list with a quote, in this order:

- what this train is **adding** — sources and words, including anything coming
  back from held
- what your twin **will hold** afterwards — sources, words, and roughly how
  many chunks that is
- that this **rebuilds all of them**, per the line above
- how many sources are held back, and which train of your month this is

Every figure is counted from material you have already added — your word counts
are stored, and the rest is arithmetic over them. Words, sources and trains are
the units on every training screen.

## While a train is running

The Train stage shows **which phase** the rebuild is in — reading through your
material, working through it, then switching your twin over — and it says so in
words as well as marks, so it reads the same whether you are looking at it or
listening to it.

**It does not show a percentage, and that is deliberate.** A rebuild reports
where it has got to in stages, not as a measurement: the point where your
material has been read is the same point whether the next step takes four
seconds or four minutes. A number there would look precise and be wrong, so you
get the stage it is actually in instead.

Three things follow from training being a queued job rather than something this
page runs:

- **You can leave.** Closing the tab does not stop a train. It finishes on its
  own, and the new material is live when it does.
- **A train the night started is followable too.** Open the Train stage while
  one is running — whoever started it — and you see the same phases.
- **A train that fails changes nothing.** Your twin keeps answering from the
  material it already had, the stage says what went wrong, and the queue tries
  again. The [Sources](/docs/sources) guide covers what a failed rebuild looks
  like on the rows themselves.

## What a train counts against

Two separate limits, and they fail in different ways.

**Size** — how much your twin can hold at once, in words and sources. This is
the [plan](/docs/plans-and-billing) limit you meet by growing. Going over it
doesn't lose anything: the train is refused, the panel says what is over and by
how much, and you either hold something back to leave it out or talk to us
about more room.

**Trains a month** — how many rebuilds your plan includes. Every train counts
as one, whether you pressed the button or the night ran it: an automatic train
is a train. **A train that fails costs you nothing** — the count happens when a
rebuild publishes, so retries are free.

When a month's trains are used up:

- **Learning pauses, and hiy says so** rather than going quiet. The Train stage
  states the pause and the date it lifts.
- **Nothing is lost.** Changes keep queueing, and the first train of next month
  picks up everything that accumulated.
- **Removing is never paused.** A source you deleted is still being answered
  from until a train takes it out, so that train is never refused — by the
  button or by the overnight sweep, whatever your month looks like. Taking your
  own material down is not something you can run out of.

## Where to look

- [Sources](/docs/sources) — the chips on each row, and what a failed rebuild
  looks like.
- [Testing your twin](/docs/testing) — the check to run once a train lands.
- [Saved questions](/docs/saved-questions) — the set to re-run after one.