# Custom Instructions

If you repeatedly ask the agent the same thing ("use a dark theme", "keep the UI minimal"), set it once as a **custom instruction**. It's standing guidance the agent applies across everything you create, included in every session so you don't have to repeat yourself.

## What They Are

A custom instruction is a note about how you want the agent to work. It's not a one-off request like a prompt, but a default that applies across everything you build. The agent still does exactly what each prompt asks; your instructions just shape the choices it makes when a prompt doesn't specify something, like which style to default to or which conventions to follow.

## Setting Them Up

Open **Settings** -> **General**, and find **Custom Instructions** in the **Agent** section. Click it to open the dialog, type your guidance into the text box, then click **Save**. From then on, the agent takes it into account whenever it builds or edits an app.

## Good Uses

Custom instructions work best for stable preferences that apply broadly:

- **Tone and style.** "Keep copy concise and friendly", or "avoid technical jargon in anything the user sees."
- **Look and feel.** "Default to a clean, minimal layout", or "prefer light mode unless I ask otherwise."
- **Conventions.** "Use 24-hour time", or "label buttons with verbs."
- **Defaults you always want.** "Add a settings screen to every app", or "include a keyboard shortcut to quit."

If something is specific to one app, put it in a prompt instead. Custom instructions are for the things you'd otherwise repeat across many apps.

## Writing Good Ones

A few clear instructions work better than a long list. The agent weighs your guidance alongside every prompt, so the tighter and more concrete it is, the more reliably it lands.

- **Be specific.** "Use rounded corners and generous spacing" beats "make it look nice."
- **Keep it short.** A handful of preferences is easier to honor than a wall of rules.
- **Avoid contradictions.** Conflicting instructions force the agent to guess. Prune anything that no longer reflects how you want to work.
- **Revisit it.** As your taste settles, reopen the dialog and update it. It's not set in stone.

> [!TIP]
> If a preference matters for one app only, say it in your [prompt](/prompting/writing-effective-prompts) rather than as a custom instruction. Reserve custom instructions for what you want everywhere.

### Do custom instructions apply to apps I've already built?

They apply to work the agent does from the point you set them onward, including future edits to existing apps. They don't reach back and change apps retroactively on their own.

### What if a prompt conflicts with my custom instructions?

Your prompt wins for that request. Custom instructions are defaults; an explicit instruction in the moment takes priority over a standing one.