Cadmus

Website and documentation · crates.io · API reference · Building with AI agents

A batteries-included web framework for Rust. Describe your data once, as a model, and Cadmus gives you:

• a database table for it, kept up to date with migrations;
• an admin site where people log in and add, edit, search and delete records;
• a REST API (JSON) so other programs can do the same, with interactive documentation;
• accounts and permissions: users, groups, two-factor login, login with Google and others;
• management commands such as migrate and createsuperuser;
• file uploads, to your disk or to cloud storage.

It is built on axum (the web server) and SeaORM (the database layer), and works with SQLite, PostgreSQL and MySQL.

Status: early (version 0.1). Everything described here works and is tested on all three databases, but details may still change between versions.

Contents

• Why Cadmus
• Your first project, step by step
• What is in a project
• Core ideas
  • Models
  • The admin site
  • The REST API
  • Migrations
  • Accounts and permissions
  • People log in, programs use keys
  • Settings
• Guides: relations, login methods, e-mail, two-factor authentication, login attempt limits, file uploads, API documentation, databases, errors and your own code, home page, deploying
• Building with AI agents
• Reference: commands, settings, migrations in detail
• Not done yet · Working on Cadmus · License

Why Cadmus

• Batteries included. Accounts, permissions, an admin site, an API with documentation, migrations and file uploads come with the framework, configured in one settings file. There is nothing to choose and wire together before you can start.
• Little code to write. There are no HTML templates for the admin and no handlers for the API: both are generated from the models. Your own code goes where the generated parts stop.
• Caught early. It is Rust, so a misspelt setting, field or model is reported when the project compiles, before anything runs.
• One program to deploy. The result is a single fast executable, with no interpreter or runtime to install on the server.

Your first project, step by step

You need Rust (a recent stable version, installed with rustup). Nothing else: the first project uses SQLite, a database kept in a single file.

1. Install the cadmus command, which creates projects and models:

cargo install cadmus-cli

2. Create a project:

cadmus new blog
cd blog

This writes a ready-to-run project (see What is in a project), including a .env file with a fresh secret key. For PostgreSQL or MySQL instead of SQLite, use cadmus new blog --database postgres (or mysql) and edit the address in .env.

3. Describe your data. A blog post with a title, a body, a published flag and a view count:

cadmus generate model Post title:string body:text published:bool views:int

This writes src/models/post.rs and registers it. The field types are string, text, int, bigint, float, bool, datetime, date, json, decimal (an exact number such as a price), uuid, file (an uploaded file), references (a link to another model, see Relations), many (links to any number of rows of another model, as in tags:many) and owner (rows belong to the account that adds them). Add ? to make a field optional, as in rating:float?.

4. Create the table:

cargo run -- makemigrations   # writes src/migrations/m0001_initial.rs, describing the table
cargo run -- migrate          # creates it in the database

The first run compiles the project, which takes a minute or two; later runs are quick.

5. Make an account for yourself:

cargo run -- createsuperuser --username admin

It asks for a password. A superuser can do everything, including managing other accounts.

6. Start the server:

cargo run -- serve

Then open:

Address	What you see
http://localhost:3000/admin	the admin site: log in, then add and edit posts
http://localhost:3000/api/docs	the API documentation, where you can try every request
http://localhost:3000/	a public status page (is the service up, does the database answer)

7. Change something. Give posts an optional summary: in src/models/post.rs, add the line pub summary: Option<String>, to the Model struct. Then:

cargo run -- makemigrations   # notices the new field, writes m0002_post_summary.rs
cargo run -- migrate          # adds the column; existing posts keep their data

That is the whole loop: change the models, make a migration, apply it.

What is in a project

blog/
├── Cargo.toml              Rust's project file: name and dependencies
├── .env                    secrets for this machine: database address, secret key (not in git)
├── .env.example            the same without the secrets, to share
└── src/
    ├── main.rs             starts the app: settings, migrations, models, your routes
    ├── settings.rs         how the site behaves: every setting in one place
    ├── models/
    │   ├── mod.rs          lists the models, with the admin options for each
    │   └── post.rs         one file per model
    ├── migrations/
    │   ├── mod.rs          the list of migrations, kept by makemigrations
    │   └── m0001_initial.rs
    └── routes.rs           your own pages and endpoints, next to the generated ones

main.rs is short:

#[tokio::main]
async fn main() -> Result<(), AdminError> {
    let app = App::from_settings(settings::settings()?)
        .await?
        .migrations(migrations::all());
    models::register(app).routes(routes::router()).run().await
}

run() reads the command line, so the same program is the server (serve) and every management command.

Core ideas

Models

A model describes one kind of record: its fields and their types. Cadmus uses SeaORM entities as models; cadmus generate model writes one for you:

#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
#[sea_orm(table_name = "post")]
pub struct Model {
    #[sea_orm(primary_key)]
    pub id: i32,
    pub title: String,
    #[sea_orm(column_type = "Text")]
    pub body: String,
    pub published: bool,
    pub views: i32,
    pub summary: Option<String>,   // Option = may be empty
}

Registering a model, in src/models/mod.rs, is one line, plus any options for the admin:

app.model::<post::Entity>(
    ModelOptions::new()
        .label("Posts")                                   // name in the menu
        .list_display(["id", "title", "published"])       // columns on the list page
        .search_fields(["title"])                         // what the search box looks in
        .list_filter(["published", "created_at"])         // filter dropdowns above the list
        .readonly_fields(["views"])                       // shown, but not editable
        .hidden_fields(["internal_note"])                 // never shown or sent anywhere
        .set_action("publish", "Mark as published", "published", "true"),
)

Every registered model gets its admin pages and its API endpoints at once.

The admin site

/admin is where people manage the data in a browser. It works on phones as well as desktops, has light and dark themes, and shows each account only what it may do.

• Dashboard: the models the account can see, with how many records each has and what the account may do with them.
• Lists: search, sorting by clicking a column heading, and pages of results. On phones each row becomes a card.
• Filters (list_filter): a dropdown per column above the list: Yes/No for true/false fields, names for links to other models, periods ("Past 7 days", "This month") for dates, the values present for other columns, and "(empty)" for optional ones. Filters combine with search, and sorting and paging keep them.
• Acting on several rows: tick rows (or all on the page), then pick an action. "Delete selected" asks first, and keeps rows that other rows still point to. set_action(name, label, column, value) adds an action that sets a column on every selected row; action(name, label, |ids| async move { ... }) runs your own code with the selected ids. Both need the change permission; at most 1000 rows at a time.
• Forms: buttons appear only for what the account may do, a record it cannot change opens read-only, and deleting asks for confirmation. Links to other models are dropdowns, and file fields have a file picker with a preview for images.
• Keyboard: / jumps to the search box, and every control can be reached with the keyboard.
• Your own look: site title, colour, logo, theme and more are settings. The pages load the Fira Sans typeface from Google Fonts; admin.web_fonts: false uses the system's typeface instead and contacts no other site.

The REST API

Everything in the admin can also be done by a program, over HTTP with JSON. For every model, under /api:

Request	What it does
GET /api/post	list posts: {"data": [...], "meta": {"total", "page", "per_page"}}
GET /api/post?q=rust&sort=-id&page=2&per_page=50	search, sort (- for highest first), page (at most 100 per page)
GET /api/post?published=true&views__gte=100	filter (see below)
POST /api/post	create one; answers 201 with the new record
GET /api/post/1	read one
PUT /api/post/1	replace one: every required field must be sent
PATCH /api/post/1	change only the fields sent
DELETE /api/post/1	delete one; answers 204

Filtering works on any visible column: ?published=true&author_id=3; comparisons with __gt, __gte, __lt and __lte (?views__gte=100, ?created_at__gte=2026-01-01); __isnull=true or false; and for dates __range=today, 7d, 30d, month or year (UTC). An unknown column, or a value the column cannot hold, is refused with 422. A column named page, per_page, q or sort cannot be filtered on.

Errors come back as JSON, {"error": {"code", "message", "field"}}, with a status such as 401 (not logged in), 403 (not allowed), 404 (not found), 409 (conflicts with other data, e.g. a duplicate), 422 (invalid field) or 429 (too many attempts). Fields that are unknown, hidden or read-only are refused rather than silently ignored.

Every request needs a login token or an API key; see People log in, programs use keys. The API follows the same permissions as the admin. Its interactive documentation is at /api/docs (more).

Migrations

The database's tables must match your models. Migrations are the steps that get them there, saved as files so every copy of the project (your laptop, a colleague's, the server) goes through the same steps:

cargo run -- makemigrations   # compares the models with the migrations so far, writes the difference
cargo run -- migrate          # applies the migrations this database has not had yet

A migration is a short Rust file you can read and edit:

pub fn migration() -> Migration {
    Migration::new("0002_post_changes")
        .rename_column("post", "body", "content")
        .add_column("post", Column::new("status", Type::String(None)).default("draft"))
        .drop_column("post", Column::new("views", Type::Integer))
}

• One file, every database: the same migration runs on SQLite, PostgreSQL and MySQL; migrate turns it into the right SQL for each.
• Safe: each migration runs as one transaction, so a failure leaves the database as it was (MySQL is the exception: it saves table changes as it goes).
• History: applied migrations are recorded in the cadmus_migration table, and showmigrations lists them.
• Undo: cargo run -- migrate 0001 rolls back everything after 0001.
• Renames: makemigrations asks whether a column was renamed or replaced, so data is not lost by accident. Mark the field #[sea_orm(renamed_from = "body")] to say so up front.

The details, including data changes and rollbacks, are under Migrations in detail.

Accounts and permissions

Each account has three switches:

Switch	Meaning
Active	Can log in. Untick to lock someone out without deleting the account.
Staff	Can use the admin and the API.
Superuser	Can do everything, including managing accounts.

Staff who are not superusers can only do what they were given: for each model, any of view, add, change and delete. Permissions are given to an account directly or to a group of accounts (such as "Editors"); an account has both. Whoever may change a model may also view it, and file uploads count as a model named files.

Superusers manage accounts and groups in the admin, under Users and Groups. The same rules apply in the admin and the API, and the admin hides links and buttons an account cannot use.

• Own rows only: give a model an owner field (cadmus generate model Note text:text owner:owner) and accounts that are not superusers see, change and delete only the rows they added; other rows answer "not found".
• Changes apply at once: permissions are checked on every request, so deactivating an account locks it out immediately, even if it is logged in.
• Nobody can remove their own access or delete their own account, so a superuser always remains. If you are locked out anyway, cargo run -- promote --username U makes an account superuser again.
• Accounts also have an e-mail address (unique; it can be used to log in), first and last name and phone, and record when they joined and last logged in. For fields of your own, add a model linked to cadmus::user::Entity (one profile row per account).
• Passwords are stored as Argon2id hashes, never in plain text.

People log in, programs use keys

There are two kinds of visitors, and each gets its own way in.

People log in with a username (or e-mail address) and password, or another login method such as Google, plus their two-factor code if they turned it on. In the admin this happens on the login page. An app that people use, such as a mobile app, does the same through the API:

curl -X POST http://localhost:3000/api/auth/token \
     -H "Content-Type: application/json" \
     -d '{"username": "admin", "password": "...", "totp": "123456"}'
# → {"access_token": "eyJ...", ...}

curl -H "Authorization: Bearer eyJ..." http://localhost:3000/api/post

The token (a JWT) lasts an hour (auth.token_lifetime), after which the person logs in again.

Programs running on their own have nobody to type a password or a phone code: a nightly import script, another company's server, a website's backend fetching posts to show. They use an API key instead: a long random string, made once and pasted into the program's configuration.

curl -H "Authorization: Bearer cadmus_..." https://example.com/api/post
curl -H "X-API-Key: cadmus_..." https://example.com/api/post     # the same

	Login token	API key
For	a person, in an app	a program running on its own
Made by	logging in with password (and two-factor code)	once, on the account's API keys page
Lasts	an hour	until revoked, or 30 days / 90 days / a year / never
If it leaks	change the password	revoke that one key; nothing else changes
Can be limited	no	read-only

How keys work:

• Making one: each account has an API keys page (the key icon under its name in the admin's menu), or run cargo run -- apikey --username U --name "import script". The key is shown once; only a fingerprint (SHA-256 hash) of it is stored.
• What it can do: act as its account, with the account's permissions, through the API only (never the admin pages). A read-only key can view but not add, change or delete.
• When it stops: when revoked, when it expires, or when the account is deactivated or deleted. The page shows when each key was last used.
• Safety: making a key needs a login in the last 15 minutes or the password, so someone who steals a logged-in browser session cannot quietly make one. Superusers see every account's keys on its user page and can revoke them.
• Not needed? If only people use your API, leave keys unused, or turn them off with auth.api_keys: false.

The admin itself keeps the login in an HttpOnly, SameSite=Strict cookie, and every form carries a CSRF token. The API never accepts that cookie, only a token or a key.

Settings

A project is configured in one file, src/settings.rs. It is plain Rust, so the compiler catches a misspelt setting, and your editor completes the names and shows what each one does. Anything left out keeps its default:

use cadmus::AdminError;
use cadmus::settings::*;

pub fn settings() -> Result<Settings, AdminError> {
    let debug = env_or("DEBUG", false)?;

    Ok(Settings {
        secret_key: env("SECRET_KEY")?,
        database: DatabaseSettings {
            url: env("DATABASE_URL")?,
            ..Default::default()
        },
        auth: AuthSettings {
            cookie_secure: !debug,     // the login cookie needs HTTPS, except on your machine
            totp_required: true,       // everyone must use two-factor login
            ..Default::default()
        },
        admin: AdminSettings {
            site_title: "Acme".into(),
            accent_color: "#0a7f5a".into(),
            ..Default::default()
        },
        ..Default::default()
    })
}

• Secrets stay out of the code. The database address, the secret key and passwords are read with env("NAME")?: from .env on your machine (loaded automatically), from the server's environment variables in production. env_or("NAME", default)? reads an optional value of any type (true/false, 1/0, yes/no for yes-or-no), and env_opt("NAME") an optional text. A missing or malformed variable stops start-up and names it.
• Checked at start-up: a mistake stops the server with the setting it is about, e.g. admin.accent_color: accent colour must be #rgb or #rrggbb, got `red` . cargo run -- check runs the same checks without starting the server.
• Values that differ per machine are ordinary code: if debug { ... }, or bind: env_or("APP_BIND", "127.0.0.1:3000".to_owned())?.

Every setting is listed under All settings.

Guides

Relations

A link from one model to another (a foreign key) is a references field. Generate the model being pointed to first:

cadmus generate model Author name:string email:string
cadmus generate model Post title:string author:references editor:references=author?

author:references adds an author_id column pointing at author. editor:references=author? adds an optional editor_id that also points at author. A model can point to itself (parent:references=category? on Category). Migrations create the database constraint that keeps the links valid.

In the admin, such a field is a dropdown of the related records on forms, and lists show the related record's name, linked to it, instead of its number.

• Which name: a record is named by its first text field (name, title, ...). Choose another with ModelOptions::new().display_field("email").
• Long lists: above 200 related records there is no dropdown; the form takes the id and says which record it currently points to.
• Permissions: names are shown only to accounts that may view the related model; others see and edit the plain number.
• Deleting: a record that others still point to cannot be deleted (409).
• Hand-written entities: any belongs_to relation in an entity is picked up the same way.
• What points here: a record's page lists the records that point to it (an author's posts), with links to see them all and to add one.

The API reads and writes the id itself (author_id).

Many-to-many: cadmus generate model Post title:string tags:many gives each post any number of tags, kept in a generated link table (post_tags). The admin shows a checkbox per tag, and the API a list of ids ("tags": [1, 3], filter with ?tags=3).

Checks on save: SeaORM's before_save and before_delete hooks in a model file run for every change from the admin and the API. Return cadmus::invalid("price", "must not be negative") to refuse one; the message is shown on the form, or sent with a 422.

Login methods

Each project chooses how people log in. The login page shows the chosen methods, in order:

// Password, or Facebook
auth: AuthSettings {
    methods: vec![
        AuthMethod::Password,
        AuthMethod::Facebook(OAuthClient::from_env("FACEBOOK")?),
    ],
    ..Default::default()
},

// Google only, and anyone at acme.com gets an account on first login
auth: AuthSettings {
    methods: vec![AuthMethod::Google(OAuthClient::from_env("GOOGLE")?)],
    signup: Signup::Domains(vec!["acme.com".into()]),
    signup_groups: vec!["Staff".into()],
    ..Default::default()
},

Method	What it needs
AuthMethod::Password	nothing; leave it out to turn passwords off everywhere, the API's token endpoint included
AuthMethod::MagicLink	e-mail; people type their address and get a login link
AuthMethod::Google(client)	an OAuth client from the Google Cloud console
AuthMethod::Microsoft { client, tenant }	an app registration in Microsoft Entra; tenant is common, organizations, consumers or your directory's ID
AuthMethod::GitHub(client)	an OAuth app in GitHub's developer settings
AuthMethod::Facebook(client)	an app at developers.facebook.com with Facebook Login
AuthMethod::Oidc(OidcProvider::new(name, label, issuer, client))	any OpenID Connect provider: Okta, Auth0, Keycloak, GitLab, ...

OAuthClient::from_env("GOOGLE") reads GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET from .env. Set server.public_url to the site's address (PUBLIC_URL in a generated project) and give each provider this redirect URI: <public_url>/admin/auth/<name>/callback, e.g. https://shop.example.com/admin/auth/google/callback.

Who gets in. A login through another site is matched to the account with the e-mail address that site vouches for, and the two are then linked, so later logins work even if the address changes. Addresses the site has not verified are never used. Nobody else gets in unless signup allows it: Signup::Domains(vec!["acme.com".into()]) or Signup::Open create an account at the first login, as staff with no permissions of their own, in the signup_groups. Each account's page lists its links, and a superuser can remove one.

• Accounts with two-factor login enter their code after coming back from the other site, and totp_required applies as for passwords. Inactive accounts cannot log in.
• To start a project without passwords, run createsuperuser --username you --email you@example.com: it asks for no password, and the account logs in through the provider.
• Microsoft's shared directories (common, organizations, consumers) let people choose any address, so their addresses only count if the app sends the optional xms_edov claim. With your own directory's ID as tenant, its addresses are trusted.
• GitHub uses the account's primary verified address. For an OpenID Connect provider that does not say whether addresses are verified, trust_email: true trusts them; only do that when users cannot pick their own address.
• These logins are for the admin. Programs use an API key.

E-mail

Login links, password resets and invitations are sent by e-mail. Until mail.url is set, messages are written to the server's log instead, so on your own machine you copy the link from the terminal:

mail: MailSettings {
    url: env_opt("MAIL_URL"),   // smtps://user:password@smtp.example.com
    from: Some("Acme <noreply@acme.com>".into()),
},

smtps:// (TLS, port 465) and smtp://...?tls=required (STARTTLS, port 587) work with any provider's SMTP service. Unencrypted smtp:// is accepted only to this machine, e.g. a test inbox such as Mailpit on smtp://localhost:1025. To send through an HTTP API instead, implement cadmus::Mailer (one send method) and pass it to App::mailer.

• Login links (AuthMethod::MagicLink): the login page asks for an address and mails a link that works once, within 15 minutes. Opening it shows a button rather than logging in straight away, because mail scanners open links to check them.
• Forgot your password? appears under the password field when passwords are on and server.public_url is set. The link works for an hour.
• Changing your own password: the lock button next to your name in the admin.
• Invitations: on the new-account form, "Send an invitation instead" e-mails a link, valid once for 7 days, where the person chooses their password. The account's page can send it again.
• The answer to "send me a link" is the same whether or not the address has an account, and mail is sent in the background, so nobody can find out who is registered. Requests are limited like login attempts.

Two-factor authentication

Two-factor login asks for a code from an app on your phone (Google Authenticator, 1Password, Aegis, ...) as well as the password, so a stolen password alone is not enough.

Each person turns it on for themselves: click your name in the admin menu, scan the QR code, and confirm with a code. From then on logging in needs the current code: in the login form, or as "totp" in an API token request.

• Each code works once, so an intercepted code cannot be reused.
• Recovery codes: turning it on shows ten codes, once. Each logs in a single time in place of a phone code, for when the phone is lost. The two-factor page shows how many are left and makes a new set. Only a fingerprint of each code is stored.
• Turning it off asks for a current code (or a recovery code). Turning it on needs the password too, if the login is more than 15 minutes old.
• Lost phone, no recovery codes: a superuser ticks "Turn it off" on the person's account page, or run cargo run -- totp --username U --disable.
• Making it compulsory: auth.totp_required: true. Nobody can then log in without it, so set up the first account from the terminal: cargo run -- totp --username U prints the QR code and the recovery codes.

Login attempt limits

To stop password guessing: after 5 failed attempts on one account within 5 minutes, further attempts on that account are refused (429 Too Many Requests, with a Retry-After header) until the 5 minutes are over. A successful login clears the count. One client address gets four times as many attempts across all accounts. Change the numbers with auth.login_max_attempts (0 turns the limit off) and auth.login_lockout.

• Behind a reverse proxy (nginx, a load balancer), every request seems to come from the proxy. Set server.client_ip_header to the header the proxy sets (e.g. X-Forwarded-For), but only if it always sets it; otherwise clients could pretend to be anyone.
• Counts are kept in memory, per running copy of the server: several copies each count separately, and a restart clears them.
• Someone who knows a username can keep that account locked by guessing. That is the usual trade-off of per-account limits; shorten auth.login_lockout if it becomes a problem.

File uploads

Set uploads.storage_url to turn uploads on. The address chooses where files are kept:

Address	Where	Cargo feature
file:///absolute/path	a folder on the server	built in
s3://bucket/prefix	Amazon S3 and compatible services	s3
az://container/prefix	Azure Blob Storage	azure
gs://bucket/prefix	Google Cloud Storage	gcs

Cloud credentials are read from the usual environment variables (AWS_ACCESS_KEY_ID, AWS_REGION, AWS_ENDPOINT, AZURE_STORAGE_ACCOUNT_NAME, ...).

On admin forms: a field generated as photo:file (or an integer column listed in ModelOptions::file_fields(["photo"])) holds a file. Its form field is a file picker that shows the current file, a preview for PNG, JPEG, GIF, WebP and AVIF images, and "Remove the file" when the field is optional. Lists show the file's name, linked to it. Anyone who may view the record may download its file. Files from a form that is then rejected are removed.

Through the API:

Request	What it does
POST /api/files (multipart form, field file)	uploads a file; answers 201 with its record, whose id goes in file fields
GET /api/files, GET /api/files/{id}	file details
GET /api/files/{id}/content	downloads the file
DELETE /api/files/{id}	deletes it

Large files can be sent in pieces, and the upload resumes after a dropped connection:

1. POST /api/uploads with {"filename", "size", "content_type"} gives an upload id.
2. PATCH /api/uploads/{id} with the header Upload-Offset: N and the next bytes, in order. A wrong offset gets 409 with the right one.
3. GET /api/uploads/{id} tells how much has arrived: that is where a client resumes.
4. The piece that completes the file answers 201 with the file's record.
5. DELETE /api/uploads/{id} cancels.

Uploads survive server restarts and can continue on another server. Stored names are chosen by the server; the original file name is kept only as a label. Files sent through an admin form must finish within server.request_timeout (30 seconds by default), so very large files should go through the API. Replacing or removing a file on a form leaves the old one stored (it is still listed at /api/files).

In your own code, Storage (put, get, delete, sink) and Uploads are available.

API documentation

Every project documents its own API:

Address	What it is
/api/docs	Swagger UI: browse the endpoints and try them out
/api/redoc	ReDoc: the same, as a reference page
/api/openapi.json	the OpenAPI 3.0 description, for generating client code

It is generated from the models: every endpoint, the fields returned, the fields that may be sent and which are required, the permission each needs, and file uploads when enabled. Hidden fields never appear, and read-only fields appear only in what is returned.

To try requests in Swagger UI, press Authorize and log in with a username and password, or paste an API key under apiKey.

Protecting it. The documentation is public by default; it shows model and field names, never data. To ask for a username and password first (the browser's own prompt), set both, with the password in .env:

docs: DocsSettings {
    username: Some("docs".into()),
    password: Some(env("DOCS_PASSWORD")?),
    ..Default::default()
},

These only open the documentation; they are not an account. enabled: false removes the documentation entirely.

• cargo run -- openapi > openapi.json writes the description without starting the server.
• Your own routes are not discovered; add them with app.docs(DocsConfig::new().extend(|doc| { doc["paths"]["/health"] = json!({...}); })).
• docs.title, docs.version and docs.description (Markdown) set the heading.
• The viewers load from a CDN (jsDelivr, pinned versions), so the two pages need internet access in the browser. To host them yourself, set docs.swagger_js_url, docs.swagger_css_url and docs.redoc_js_url.

Databases

The address in database.url chooses the database. Every driver is built in, so switching is a change to .env, not to the code:

Database	DATABASE_URL
SQLite	sqlite://db.sqlite3?mode=rwc (mode=rwc creates the file)
PostgreSQL	postgres://user:password@host:5432/name
MySQL and MariaDB	mysql://user:password@host:3306/name

Oracle and SQL Server are not supported: SeaORM, the database layer, has no open-source driver for them.

The API behaves the same on all three: true and false are JSON booleans, dates and times are ISO 8601 (2026-03-04T05:06:07), JSON fields come back as JSON, and ?q= search ignores case.

Smaller builds: a project that only uses one database can leave the other drivers out, to compile faster: cadmus = { ..., default-features = false, features = ["postgres"] } (the features are sqlite, postgres and mysql).

Errors and your own code

src/routes.rs holds your own axum routes, served next to the generated ones. Every failure in Cadmus is an AdminError, shown in the right form for where the request went:

Request to	An error looks like
/api/...	JSON: {"error": {"code", "message", "field"}}
/admin/...	a page in the admin's style (error.html, which you can override)
anything else	plain text, or whatever your handler returns

Unknown addresses, wrong methods (405) and crashes in a handler become proper error responses too. Internal details (SQL, file paths, crash messages) are logged, never sent to the visitor.

In your own handlers, return ApiResult<T> to get JSON errors. Database, storage and I/O errors convert with ?, and AdminError::custom makes an error with your own status and code:

async fn buy(State(db): State<DatabaseConnection>) -> ApiResult<Json<Receipt>> {
    let item = item::Entity::find_by_id(1).one(&db).await?
        .ok_or_else(|| AdminError::NotFound("item".into()))?;
    if item.left == 0 {
        return Err(AdminError::custom(StatusCode::CONFLICT, "out_of_stock", "sold out").into());
    }
    Ok(Json(Receipt { id: item.id }))
}

Log messages go to the terminal (standard error); log_level in the settings, or the LOG_LEVEL variable, sets how much. debug also shows every SQL statement.

Home page

/ is a public status page: the service's name, whether it is up, whether the database answers and how fast, and how long it has been running. It refreshes every 30 seconds and links nowhere, so it does not lead visitors to the admin.

• For monitoring: the same address with Accept: application/json returns {"status", "database": {"status", "latency_ms"}, "uptime_secs", "checked_at"}. Both answer 503 when the database is down, so a load balancer can use it as a health check.
• API addresses typed into a browser's address bar are sent to /. Programs, scripts and tools like curl reach the API as usual, and the documentation pages are not affected.
• Your own page: a / route in src/routes.rs replaces it automatically. To turn it off, set home.enabled: false (do that too if your routes set their own Router::fallback). home.title and home.tagline set what it says.

Deploying

A generated project is ready to run behind HTTPS as it is:

• Time limit: a request that takes longer than 30 seconds gets 503 and is stopped (server.request_timeout; None for no limit). Uploads and downloads are exempt.
• Request log: one line per request with method, address, status and duration (the query string is left out).
• Protective headers on every admin and API response: no embedding in other sites, no content-type guessing, no caching of pages that needed a login.
• Cross-origin access (CORS) is off. To let a browser app on another domain call the API, set server.cors_origins: vec!["https://app.example.com".into()] (or "*"). Such apps use a token or key; the login cookie is never accepted from another domain.
• Graceful shutdown on Ctrl-C.

Before going live:

1. Serve over HTTPS, and leave DEBUG unset in production: the generated settings only allow the login cookie over plain HTTP when DEBUG=true.
2. Behind a reverse proxy, set server.client_ip_header (see Login attempt limits), and server.bind to 0.0.0.0:3000 if the proxy runs on another machine or container.
3. Set DATABASE_URL and SECRET_KEY on the server, keep .env out of git, and use a different SECRET_KEY for each environment (cadmus secret prints a new one).
4. Run cargo run --release -- migrate as part of each deployment, before starting the new version.

Responses are not compressed, on purpose: admin pages contain a security token next to text the visitor controls (the search box), which is what the BREACH attack on compressed HTTPS needs.

Building with AI agents

Cadmus offers two MCP servers, so AI assistants can work with it:

• Hosted docs server, for any app that adds an MCP server by its address (ChatGPT, Claude, Gemini CLI, Cursor, VS Code). Nothing to install; the assistant can search and read the documentation. Add https://cadmus-mcp.cadmus-mcp.workers.dev/mcp.

• Local server, cadmus mcp, for coding agents on your computer. The agent can also create projects, add models and run migrations for you:

  claude mcp add cadmus -- cadmus mcp                 # Claude Code
  

  or, for clients with an mcpServers list (Claude Desktop, Cursor):

  { "mcpServers": { "cadmus": { "command": "cadmus", "args": ["mcp"] } } }
  

Every project made by cadmus new also has an AGENTS.md guide, and the website offers llms.txt. Details: Building with AI agents.

Reference

Management commands

Run as cargo run -- <command> (or ./target/release/<project> <command> for a built program).

Command	What it does
serve [--bind addr]	start the server
makemigrations [--name N] [--empty] [--check] [--no-input]	write a migration for the model changes into src/migrations
migrate [target] [--fake]	apply new migrations, or roll back to target (a name, a number such as 0002, or zero)
showmigrations	list migrations and whether this database has had each
sqlmigrate NAME [--backwards]	print the SQL a migration runs on this database
createsuperuser --username U [--email E] [--password-stdin]	create a superuser
changepassword --username U [--password-stdin]	change a password
promote --username U	make an existing account an active superuser
totp --username U [--disable]	turn two-factor login on (prints a QR code) or off
apikey --username U --name N [--days D] [--read-only]	make an API key (90 days by default; --days 0 for never)
openapi	print the API description as JSON
routes	list the generated addresses
check	check the configuration without starting the server

And the cadmus command:

Command	What it does
cadmus new NAME [--database sqlite|postgres|mysql] [--framework-path PATH]	create a project
cadmus generate model NAME field:type ...	add a model to the project in the current folder
cadmus delete model NAME [--yes]	remove a model: its file and its lines in src/models/mod.rs
cadmus secret	print a new secret key
cadmus mcp	serve the MCP protocol for AI agents

All settings

Section	Settings (defaults in brackets)
secret_key	signs login tokens; at least 32 bytes (cadmus secret prints one)
database	url, max_connections, min_connections, acquire_timeout
server	bind (127.0.0.1:3000), request_timeout (30 s; None for no limit), cors_origins, client_ip_header, public_url
auth	methods (password), signup, signup_groups, token_lifetime (1 h), totp_required, cookie_secure (true), login_max_attempts (5), login_lockout (5 min), api_keys (true)
admin	path (/admin), site_title, accent_color, logo_url, theme, custom_css_url, footer_text, page_size (25), nav_links, web_fonts, template_dir
api	path (/api)
docs	enabled, username + password, title, version, description, swagger_js_url, swagger_css_url, redoc_js_url
home	enabled, title, tagline
uploads	storage_url (off until set), max_file_bytes (1 GiB), max_chunk_bytes (8 MiB)
mail	url (SMTP; unset writes messages to the log), from
log_level	LogLevel::INFO; DEBUG adds SQL statements

Durations are written Duration::from_secs(600). Things a setting cannot hold (your own routes in the API documentation, your own account store) are set on the App after it is built, e.g. App::from_settings(settings()?).await?.docs(DocsConfig::new().extend(...)).

Migrations in detail

• Renames: a field marked #[sea_orm(renamed_from = "body")] is renamed. Otherwise, in a terminal, makemigrations asks whether a dropped and a new column (or table) of the same shape are a rename. With --no-input, or without a terminal, nothing counts as a rename.
• New required fields: rows already in the table need a value. Give the field a default (#[sea_orm(default_value = "draft")]), or type a value when asked; it is saved in the migration as add_column_filled.
• Editing a migration: allowed until it has been applied somewhere. Add data changes with .sql_reversible("UPDATE ...", "UPDATE ...") or with Rust code, .run(|db| Box::pin(async move { ... })). makemigrations --empty writes an empty one to start from.
• Rolling back: migrate 0001 undoes the migrations after 0001; migrate zero undoes all. A dropped column comes back empty (0, '', ...). SQL or code without a reverse cannot be rolled back; --fake forgets such a migration without running anything.
• SQLite cannot change or drop most columns in place, so for those steps the table is rebuilt: created anew, rows copied, the old one dropped. Links between tables are checked afterwards.
• In CI: makemigrations --check fails if a model changed without a migration, and migrate warns about such changes.
• Not handled: database enums and array columns, changing a primary key, and changing a column's type on PostgreSQL when the values cannot be converted (write that step with .sql(...)).
• Built-in tables (accounts, uploads) have migrations of their own, applied before yours.

Projects made before migrations existed: run makemigrations, then add mod migrations; to main.rs and .migrations(migrations::all()) to the App, as the command explains. The tables already exist, so migrate just records the first migration as applied. Until then, migrate keeps the old behaviour: it adds missing tables and columns, and never drops or renames anything. Databases from before migrations get their built-in tables brought up to date the first time migrate runs.

Projects made before src/settings.rs existed start with App::from_env(), which reads everything from environment variables. It still works. To move to settings, run cadmus new for a fresh src/settings.rs, copy it in, replace App::from_env() with App::from_settings(settings::settings()?), and rename ADMIN_JWT_SECRET to SECRET_KEY in .env.

Variable	Meaning	Default
DATABASE_URL	Required	—
ADMIN_JWT_SECRET	Required. Signing secret, at least 32 bytes	—
APP_BIND	Listen address	127.0.0.1:3000
REQUEST_TIMEOUT_SECS	Longest a request may take; 0 for no limit	30
CORS_ALLOWED_ORIGINS	Origins allowed to call the app from a browser	none
LOG_LEVEL	error, warn, info, debug (adds SQL statements) or trace	info
ADMIN_BASE_PATH, API_BASE_PATH	Address prefixes	/admin, /api
DB_MAX_CONNECTIONS, DB_MIN_CONNECTIONS, DB_ACQUIRE_TIMEOUT_SECS	Connection pool	driver defaults
ADMIN_JWT_TTL_SECS	Token lifetime	3600
ADMIN_TOTP_REQUIRED	Refuse accounts without two-factor login	false
ADMIN_LOGIN_MAX_ATTEMPTS	Login attempts per account per lockout period; 0 disables	5
ADMIN_LOGIN_LOCKOUT_SECS	Length of the lockout period	300
ADMIN_CLIENT_IP_HEADER	Header carrying the client address behind a proxy	connection address
ADMIN_COOKIE_SECURE	false only for local plain HTTP	true
STORAGE_URL	Enables uploads	off
DOCS_ENABLED	Serve the API documentation	true
DOCS_USERNAME, DOCS_PASSWORD	Ask for these before showing the documentation	open
DOCS_TITLE, DOCS_VERSION, DOCS_DESCRIPTION	Documentation heading	site title + "API", 0.1.0
DOCS_SWAGGER_JS_URL, DOCS_SWAGGER_CSS_URL, DOCS_REDOC_JS_URL	Where the documentation viewers load from	jsDelivr
UPLOAD_MAX_FILE_BYTES, UPLOAD_MAX_CHUNK_BYTES	Upload limits	1 GiB, 8 MiB
ADMIN_SITE_TITLE, ADMIN_ACCENT_COLOR, ADMIN_LOGO_URL, ADMIN_THEME, ADMIN_CUSTOM_CSS_URL, ADMIN_FOOTER_TEXT, ADMIN_PAGE_SIZE, ADMIN_NAV_LINKS, ADMIN_TEMPLATE_DIR, ADMIN_WEB_FONTS	Admin look	see UiSettings::from_env
HOME_PAGE_ENABLED	Serve the status page at /	true
HOME_TITLE, HOME_TAGLINE	What the status page says	site title, none

Your own account store: accounts live in the auth_user table (DbUserStore). To use accounts kept elsewhere, implement the UserStore trait. Every account is then a superuser unless you implement UserStore::access, API keys work only if you implement UserStore::api_key, and the Users and Groups pages are not shown.

Not done yet

• Accounts: no passkeys yet. API keys cannot be limited to some models (only read-only). Logins through other sites are for the admin, and an account is linked to another site by e-mail address only (there is no "connect" button). Per-record permissions are ownership only (one owner per row). Login attempt limits are per server process. Accounts and groups are managed in the admin only; there is no API for them.
• Admin: no page listing all uploaded files, and a replaced file is not deleted. No search-as-you-type for long lists of related records, and no editing of related records inside another record's form.
• Models: single-column primary keys only; binary fields are read-only. On SQLite, decimals are exact to about 15 digits.
• Uploads: completing a resumable upload copies the pieces once inside the storage (no direct-to-S3 multipart yet), and abandoned uploads are not cleaned up automatically.
• Server: no response compression (see Deploying), request ids or metrics; add them with your own tower layers.
• API documentation: your own routes are not discovered automatically, and the viewers load from a CDN rather than being bundled.
• Untested services: S3, Azure and Google Cloud Storage compile but have not been run against the real services.

Working on Cadmus

To try the latest unreleased version, install the command with cargo install --git https://github.com/arnabgupta-dev/cadmus cadmus-cli. To use a local copy of Cadmus in a project: cargo install --path cli, then cadmus new blog --framework-path /path/to/cadmus.

Running the tests:

cargo test                       # SQLite, in memory

# the same tests on PostgreSQL (each test gets its own schema)
docker run -d --rm -e POSTGRES_PASSWORD=test -p 5432:5432 postgres:17-alpine
TEST_DATABASE_URL=postgres://postgres:test@localhost:5432/postgres cargo test

# or on MySQL (each test gets its own database)
docker run -d --rm -e MYSQL_ROOT_PASSWORD=test -p 3306:3306 mysql:8.4
TEST_DATABASE_URL=mysql://root:test@localhost:3306/mysql cargo test

Feedback

Found a bug or have an idea? Open an issue:

• Report a bug
• Suggest something

License

MIT. Free to use and change, commercially or otherwise. Copies must keep the copyright notice; beyond that, a link back to this repository wherever you use it is appreciated.

The admin uses three icons from Lucide, under the ISC license; see THIRD-PARTY-NOTICES.md.