Configuration

Mira reads mira.config.json from the project root. Every key is optional. Unknown keys fail the build, so a typo never passes silently.

{
  "site": {
    "title": "My site",
    "description": "Notes on design and code.",
    "url": "https://example.com",
    "lang": "en"
  },
  "scheme": "dark",
  "transitions": {
    "default": "fade",
    "pairs": { "/posts/ -> /posts/*": "slide-up" }
  },
  "prefetch": { "eagerness": "moderate", "prerender": true },
  "theme": { "ink": "#f4f1ea" },
  "fonts": [
    { "family": "Inter", "src": "/fonts/Inter.woff2", "preload": true }
  ],
  "collections": {
    "posts": { "fields": { "title": "string", "date": "date" } }
  },
  "agents": { "twins": true, "robots": { "*": "allow" } },
  "headers": { "emit": true, "hsts": true },
  "hosts": { "vercel": {} },
  "redirects": { "/old/": "/new/" },
  "budgets": { "page_kb": 14 }
}

site

Key	Type	Default	Meaning
title	string	Mira site	Site name, used in titles, feeds, and llms.txt
description	string	none	Default page description
url	string	none	Absolute origin such as https://example.com; enables canonical URLs, the sitemap, and feeds
lang	string	en	The lang attribute of every page
image	string	none	Social card image under public/, such as /og.png
image_alt	string	none	Alt text for the social card
twitter	string	none	The site’s X handle, such as @example
theme_color	string	none	Browser UI color, such as #0b0b0d
same_as	list	[]	Profile URLs for the site’s structured data

scheme

dark, light, or system. Default dark. See Theming.

transitions

Key	Type	Default	Meaning
default	string	fade	Transition when nothing more specific applies
pairs	object	{}	"<from> -> <to>" keys mapped to transition names

See Page transitions.

prefetch

Key	Type	Default	Meaning
eagerness	string	moderate	conservative, moderate, or eager
prerender	boolean	true	Prerender on press

theme

An object of token overrides. Nested keys join with dashes into custom property names: { "radius": { "md": "10px" } } sets --radius-md. Values are strings or numbers. See Theming for the tokens you can set.

fonts

A list of faces with family, src, weight, style, and preload. See Fonts.

collections

Schemas keyed by collection name, each with fields and an optional strict (default true). See Content collections.

agents

Key	Type	Default	Meaning
twins	boolean	true	Write Markdown twins, llms.txt, and llms-full.txt
robots	object	{ "*": "allow" }	User agent to allow or disallow; wins over the switches below
search	string	allow	Search engine indexing
answers	string	allow	AI answer engines that fetch and cite pages
training	string	allow	Crawlers that collect pages for AI training
content	boolean	true	Publish collections and data files under /_mira/ for agents and MCP

headers

Key	Type	Default	Meaning
emit	boolean	true	Write _headers and vercel.json
hsts	boolean	true	Include Strict-Transport-Security

hosts

The hosts to write config for, each mapped to its options. Mira writes the host’s own config file on every build. See Deploying for what each one writes.

Key	Options
vercel, netlify, github, firebase, azure, docker, deno, s3	none: {}
cloudflare	project: the Pages project name
render	service: the service name

An unknown host fails the build and lists the known ones.

redirects

Old paths mapped to new paths or URLs, as permanent redirects. Each one is written in every host’s format, plus a redirect page at the old path. Sources start with /; targets are a path starting with / or an https:// URL. See Deploying.

budgets

Key	Type	Default	Meaning
page_kb	number	none	Largest gzipped page size in KB; larger pages fail the build