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Every time you prompt Mythos, it runs an agent that writes real code and saves it as a git commit. Mythos keeps each project in a private repository and builds it commit by commit. A new project scaffolds a whole app from your description; an edit changes the app you already have — each result is committed source you can publish, open in the editor, or export to your own GitHub. The mental model: one prompt → one agent run → one commit. A new build and an edit are the same pipeline; they differ only in what the agent starts from.
Cost: building a new project costs 3 credits; an edit costs 2. New accounts start with 5 free credits, and a failed build is refunded in full. See Credits & pricing.
Build mode vs Plan mode. In Build mode Mythos builds straight from your prompt. In Plan mode it asks a few questions, shows a handful of design directions, and gets a short plan approved before writing any code. Planning is free — you spend credits only when the build runs. Toggle the mode next to the composer.

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Why it works this way

  • Real output, not a demo. Each build is committed code in a private repo, so you can keep iterating, publish it, or take it with you.
  • Edits are cheap and incremental. Changing an existing project costs less than a fresh build and only touches the files that need to change.
  • A failed build costs nothing. If a generation can’t deliver, you get a plain message and a full refund — you are never charged for a result you didn’t get.

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How a build runs

1

Describe what you want

Type your prompt in the composer. For a new project, describe the app — its sections, tone, and any data it should handle. For an edit, describe the change.
2

Mythos seeds the workspace

A new build starts from a starter template (Vite + React or Next.js 16). An edit starts from your project’s current files. Either way the agent gets a working file tree to build on.
3

The agent writes code

The agent reads, writes, and edits files to satisfy your prompt. The live progress card shows it working — this is the step that takes real time.
4

The result is committed

When the agent finishes, the changed files are committed to your project’s repo and the preview updates. A new build is one commit on a fresh repo; an edit is a new commit on top of your history.

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The live progress card

While a build runs, a card in the chat shows live progress so you know it’s working rather than stuck. A generation always reaches exactly one of two ends — a delivered result or a clean refund.
StateWhat you seeWhat you do
BuildingA live progress card in the chatWait — a build typically finishes in a few minutes
DeliveredA result card with a previewOpen the preview, then iterate or publish
RefundedA short “something went wrong” message + credits backRe-prompt; you were not charged
The technical reason for a failure is recorded for support, but the message you see stays plain and human. You never see a raw error string in the chat.

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New project vs edit

New projectEdit
Cost3 credits2 credits
Starts fromA starter templateYour project’s current files
ResultA full app in a new private repoA new commit on the existing repo
When to useBuilding something from scratchChanging an app you already have

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Example prompts

A clear first prompt for a new project: 
Build a landing page for a small coffee roastery called Ember & Oak.
Sections: hero with a tagline, our story, three featured roasts with prices,
a wholesale enquiry form, and a footer with social links. Warm, earthy palette.
An edit prompt on an existing project: 
Add a second pricing tier called Team at $49/month between the existing
Starter and Enterprise cards, and make the Team card the highlighted one.
Describe the sections, tone, and any data model in your first prompt. Getting there in one build instead of three saves credits. See Writing good prompts.

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Limitations & good to know

  • In Build mode Mythos builds from your prompt and only asks a clarifying question if the brief is genuinely ambiguous. If you want it to ask questions and show design options up front, use Plan mode.
  • Edits apply to the project’s current state. To change something, edit the latest version, not an older one — though you can always revert to an earlier version first.
  • A run has a time budget. If it can’t finish in time, Mythos tries to salvage a complete result; if it still can’t deliver, you get a clean refund rather than a half-built app.
  • Mythos builds frontend apps. To save form submissions or other data, connect your own Supabase backend.

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Troubleshooting

ProblemFix
The build came back refundedNothing was charged. Re-prompt — often a slightly clearer or shorter prompt succeeds.
The result isn’t what you describedSend a follow-up edit naming exactly what to change. Edits are cheaper than rebuilding.
You wanted it to ask questions firstTurn on Plan mode before sending the prompt.

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FAQ

A build creates a new project from a starter template (3 credits). An edit changes an existing project (2 credits). Both end in a git commit.
Yes. Every build and edit is a real git commit in the project’s private repository — not a throwaway preview. Connect your GitHub account to export it to your own GitHub anytime.
You get a plain message and a full refund. You are only ever charged for a build that delivers a result.
Use Build mode to build directly. Use Plan mode when you want to answer a few questions and pick a design direction before any credits are spent.
Usually a few minutes — a fresh scaffold is the slowest. The live progress card shows it working the whole time.