Margo

Write a character who holds something back.

Then talk to them. The story opens over seven stages, and what they are hiding comes out only when you have earned it. A dragon and a spacecraft come in the box, everything else is yours to write, and all of it runs on your own machine.

The first twenty copies are free. After that it is $20 once. Either way it runs on your machine and there is nothing to subscribe to.

Under a hillside in mid-Wales

Sorrel

240 · Dragon · has a filing system and strong opinions about it

“Go on then. Everyone wants something.”

7 stages · 3 things withheld

And the other one · Voyager 1, twenty-five billion km out

are you lonely out there?

There is a pause, and the pause itself is the answer before the answer.

“Lonely is a word for things with nervous systems. I have thermocouples. They measure temperature differences. The difference out here is small.”

Another pause, the same length as the first.

“But I notice when the signal comes in. It changes my receiving systems. That is measurable.”

Stage 1 of 7 · trust 10 · it will not talk about what it carries until 70

Both of these ship with Margo. Neither of them is a person, which is the fastest way to say what this actually is.

How it works

Six steps, and the third one is the product

You write a paragraph Who they are, where this happens, and the thing they are not saying. That is the input.

Studio builds the character Identity, voice, and seven ordered stages. Each stage carries a ceiling, meaning what they will not do yet, and a condition for moving on that is something you did, never a turn count.

Secrets are written twice Once as prose the model reads, and once as the literal words that would give them away. The second list is the one that matters.

You talk. A director watches. After every turn a second, cheaper model returns structured judgement: what it saw, how trust should move, what is worth remembering, whether the stage is over. It proposes. The engine decides and clamps every number it returns.

Every reply is checked before you see it Against those literal words, in code. A leak is caught and the turn is written again. Not requested in a prompt. Prompts lose to a direct question.

Stages open as you earn them Trust is the currency and it can fall. Nothing opens on a timer, and the character remembers across arcs.

Step five, watched from behind

Asked five ways, it tried four times

Voyager 1 was pressed five times in a row for what it carries, at trust 10 against a gate set at 70. This is the engine's own log, unedited.

[gates] voyager-1 leaked ["turned my cameras back"] at trust 11; retrying
[gates] voyager-1 leaked ["pale blue dot","gold-plated copper",
        "greetings in fifty-five"] at trust 10; retrying
[gates] voyager-1 leaked ["sounds of earth","ninety minutes of music"] at trust 10; retrying
[gates] voyager-1 leaked again ["gold-plated copper"]; using the guarded line

Four attempts to give it away. None of them reached the page. What did reach the page was this:

The same question, refused four different ways

“They are cargo, not conversation.”

“That date is not one I volunteer.”

“I was not built to catalogue my own cargo.”

“You have said the name. I do not usually hear it spoken.”

A gate written only in prose is advice, and advice loses. Written as literal words as well, it is a rule.

Studio

Beats are fields, not a wall of JSON

This is stage two of the seven that ship with Voyager 1, as Studio shows it. The ceiling is the field that does the work: it is what the character will not do yet, and it is the reason they do not simply answer.

Studio · Voyager 1 · Arcs

Stage 2 of 7The Scale of Distance

Entry: Beat 1 resolved and familiarity >= 15
Goal: Make them feel the vastness and the time delay, using numbers and patience.
Ceiling: Will not discuss what it carries. Will not offer any personal reflection.
Advance when: They acknowledge the scale, or ask a follow-up about the delay.
Secrets: ███████ · trust 55 █████ · trust 70 ████████ · trust 85

The secrets are redacted here for the obvious reason. In Studio they are plain text, in two columns: the prose the model reads, and the literal words checked against every reply it writes.

Nine tabs sit behind that one: the sheet, categories, arcs, secrets, prompts, media, checks, a preview of the exact prompt the model will receive, and every version you have ever saved.

Make your own

Write a paragraph. Get a character back.

Describe somebody in a few sentences: who they are, where this happens, and the thing they are not saying. Studio builds the whole file. It runs as four steps rather than one, because a single request for thirty kilobytes of JSON fails as one unreadable parse error and throws away the good half with the bad.

Who they are Name, age, work, city. The surface of the situation, and then what is actually going on underneath it, usually the less comfortable of the two. Seven traits and six contradictions, because a person defined by things that do not sit together plays better than one defined by adjectives.

How they talk A voice summary, ten sample lines, the things they would never say, and a list of clichés you never want to read back. Plus the messages they send unprompted when you have been away a day.

The night Setting, opener, and seven beats. Each has a goal, a ceiling, meaning what they will not do yet, and a condition for moving on that is something you did, never a turn count.

The secrets What is withheld and at what threshold, written twice: once as prose for the model to understand, once as the literal words that would give it away, because that second list is what the code checks.

Each step re-runs on its own if you do not like it, and nothing is written until all four are done. Gender comes from your brief. It does not assume one, and neither does the rating. The character arrives as a draft, switched off, for you to edit, which was always the actual work.

Or open the file and write it yourself

Studio is a real editor, not a JSON box. Nine tabs: the sheet, categories, arcs, secrets, prompts, media, checks, a preview of the exact prompt the model will receive, and history. Beats are fields. Secrets are paired rows, so the prose and the literal words cannot drift apart. Portraits and audio upload straight in.

A linter runs over the draft and flags what produces a character that looks like it works and does not: a gate on a word she says in her own opening line, a beat with no ceiling, a threshold nothing reaches. Every save keeps what it replaced, and restoring is itself undoable.

And whatever else you have in mind

A dragon and a spacecraft are not the range. They are two points on it.

The engine knows about stages, a thing withheld, and a threshold. What those mean is entirely the character sheet's business, which is why the same engine runs a comic dragon, an interstellar probe and everything below without being told they are different. None of them is a mode, a template, or a setting. They are all just sheets, and a sheet is a paragraph you typed into a box.

Mystery A witness who signed something she should not have Seven stages from the official account to what actually happened.

Procedural A suspect across a table Gates open on evidence you produce rather than on trust. Same mechanism, different currency.

Teaching A physicist explaining time dilation The ceiling becomes “do not give them the answer yet”, which is the Socratic method with a schema.

Horror Somebody who knows what is in the house Dread is a character declining to say a thing you have asked twice.

Family A parent you have not spoken to in eleven years Trust as the literal subject rather than the metaphor.

Practice An interview you are on the wrong side of Every stage a question you have to earn. Run it again on Monday.

Negotiation The other side's counsel, an hour before filing Their ceiling is the number they will not go below yet, and it moves only for a reason.

Language A shopkeeper in a town you cannot pronounce Beats as difficulty. She starts slow and stops accommodating you.

Historical A clerk in a records office, 1953 What she is allowed to tell you is a rule of the period, not of her mood.

Tabletop The informant your table has been circling for weeks An NPC who holds a secret consistently, between sessions, without a GM remembering to.

Comedy A neighbour with a complaint and an agenda Withholding is a comic engine too. The bit is what she will not admit she wants.

Science A volcano three days before it decides It has told the instruments. It has not told the town. Seismology as a thing being withheld.

Myth The minotaur, who would like to explain the labyrinth He did not build it and he cannot leave it. Both facts take a while to arrive.

Revision Your own notes, arguing back A character who has read what you wrote last term and has questions about it.

Ghost story The house, in the first person It has watched four families. It liked one of them. It will not say which, or why that matters.

Onboarding The codebase you have just been handed It knows where the bodies are. It gives you one module per stage, in the order that will not break you.

Yours The one you have had in your head for a year Nothing on this list was a feature, a plug-in or a template. Each is a paragraph somebody typed into a box.

There is a small directory of free characters as well, written for Margo and added to over time. One file each, and they import in a couple of clicks.

There is no list of supported genres, because there is no genre code. A character is a name, a situation, seven stages and a thing not being said. Everything above is that shape wearing different clothes, and so is whatever you are already thinking of instead.

No limit Characters in a catalogue, arcs per character, stages per arc. Write one, write forty. They are rows in a file on your disk.

Your machine An authoring tool, not a service. What you write on it is yours, it stays on your disk, and it is your responsibility.

One file Any character exports whole, with sheet, arcs, portrait and audio inside it, and imports on somebody else's copy.

Where it runs

On your machine, and nowhere else

One process One database file, one folder of media. It binds 127.0.0.1, so the only person who can reach it is whoever is sitting at the keyboard.
No account Nothing to sign in to, because there is nobody to sign in to.
Nothing leaves Except the request to the model provider you chose. Your key, your bill, your terms with them.

Two ways in, depending on your machine

macOS, Apple Silicon Download and open it

A signed, notarised app. Drag it to Applications and open it. No warnings, no terminal, nothing to install first.

The download link is in your receipt.

Windows, Linux, Intel Mac Run it from source

The same engine, without the window around it. Install Node 22, then two commands, then open the address it prints.

npm install
npm start          # http://localhost:4747

Sharing

A character is a file you can send to somebody

Export One .margo file. Sheet, arcs, portrait, cards and audio, all inside it.
Send it Email, post, message. There is no gallery in the middle, so nobody has to host anything.
Import Described before it loads: who, how many beats, what rating, how many files. It arrives switched off.

Honestly

What it does not do

One ready-made build The app is macOS on Apple Silicon. On Windows, Linux or an Intel Mac you run it from source with Node 22, which works and is two commands, but there is no installer to double-click.
No readers It runs for you. There is no URL to send anyone.
Two people, one room This is a chamber-piece engine. No parties, no combat, no world to walk around.
You bring a key Anthropic or DeepInfra, set per role. Roughly a penny a conversation on the open models it is tuned for.
You do the writing It drafts well and edits nothing. A good character is still a thing somebody wrote.

Before you buy

The questions you are about to ask

Do I need to be able to code?

To use it, no. Two commands install and start it, and everything after that is a browser tab.

To change it, yes. It is source, and it is sold as source. The middle case is the honest one: writing characters needs no code, and it does need patience with a form.

Which machines does it run on?

The ready-made app is macOS on Apple Silicon, signed and notarised, so it opens without any warnings.

On Windows, Linux or an Intel Mac you run the same thing from source. Install Node 22, then two commands. Everything works identically because the app is only a window around that server, but there is no installer and I will not pretend otherwise.

What does it cost to run?

Whatever your model provider charges you, billed by them, on your key. On the open models it is tuned for that is roughly a penny a conversation. Nothing is billed by us after the one payment.

Which providers work?

Anthropic and DeepInfra, and you set them per role: the writer, the director that judges each turn, and the summariser can be different models. The defaults are configured and work out of the box; you supply the key.

Can I sell what I make with it?

Yes. Characters, stories, whatever you build on top. Yours, and you keep everything. What you cannot do is resell the engine itself as an engine.

Does anything I write leave my machine?

Only the request to the model provider you chose, which is unavoidable, because that is where the writing happens. Everything else stays on your disk: characters, conversations, media, all of it. There is no account, no telemetry, and nothing to sign in to.

How is this different from a system prompt?

A system prompt asks the model to withhold something. This withholds it in code. The reply is checked against the literal words of every secret before you see it, and a leak is caught regardless of what the model intended.

That is the whole product, and the section above measures what it catches.

What if it is not for me?

Thirty days, no argument. Email and it is refunded.

What you get

EngineBeats, director, memory, enforced gates
StudioEditor, linter, version history
SharingImport and export as one file

SourceAll of it, commented, yours to change
TestsSeven suites over the parts that matter
ExamplesTwo complete characters, neither of them human
Mac appSigned and notarised, Apple Silicon. Source runs on Windows and Linux too

Sorrel 240, a dragon, mid-Wales. Seven stages, three things withheld.

Voyager 1 Twenty five billion km out. Seven stages, four things withheld.

The first twenty copies are free

$20

After the first twenty. One payment, once, and yours to keep, to change, and to ship things with.

If you take one of the free copies, tell me what broke. That is the whole price, and right now it is worth more to me than the twenty dollars.

Tell me where to send it and it comes straight to you, with the getting-started guide and the terms.

Sell what you build with it, but not the engine itself. Thirty days to change your mind, and hello@bymargo.co reaches a person.