Composure

Discord bots that live on the edge.

Slash commands, buttons, modals and rich Components V2 layouts, written once in Rust and served from Cloudflare Workers or any server. No gateway, no idle process, no bill while nobody is talking to your bot.

Guide · API docs · Examples · Discord · Crates

---

use composure::{app, command, types::User};

/// Give someone a cookie
#[command]
fn cookie(
    #[option("Who gets it")] user: &User,
    #[option("How many", min = 1, max = 12)] count: Option<u8>,
) -> String {
    format!("{} gets {} 🍪", user.display_name(), count.unwrap_or(1))
}

#[app(handlers(cookie))]
pub struct Bot;

The function is the command. Its parameters become Discord Options (with min/max enforced by Discord and checked against u8 at compile time), its doc comment the description, its return value the reply. Hand Bot to an Adapter to serve it, and to composure_sync to register it.

Why Composure?

Composure handles Interactions only: commands, buttons, selects and modals that Discord delivers to your bot as signed HTTP requests.

• Serverless. No WebSocket to keep alive, no process to babysit. Deploy to Cloudflare Workers and pay per request, or run it on any box with tokio.
• Written once. One function per command: the definition Discord stores and the handler that answers come from the same code, so they can never drift apart.
• Typed end to end. Options arrive as &str, u8, &User, Role or your own enums. Duplicate commands, too many Options, out-of-range bounds and bad custom_id prefixes fail to compile, not in production.
• Markup for messages. Build Components V2 messages and modals with JSX-like rsx!, with click handlers right next to the buttons they belong to.
• State in the custom_id. Button and modal state is encoded into the custom_id for you, so a counter needs no database.
• Small and fast. A few microseconds and a few dozen allocations per Interaction; the full example bot is about 307 KB of gzipped WASM. The core has no async runtime and no HTTP stack.
• REST and more. A REST client for every Discord endpoint, deferred responses with background work, follow-ups, file uploads, Webhook Events, tracing, and a command sync CLI with CI drift checks.

	Gateway bot	Composure
Connection	A WebSocket, always open	None: Discord calls you
Hosting	A server running 24/7	Cloudflare Workers, a container, any server
Scales to zero	No	Yes
Commands defined	Often twice (registration + handler)	Once, as a function
Reads every message	Possible (with intents)	No: Interactions and Webhook Events only

If your bot needs to watch every message or presence update, use a gateway library. If it only answers people, Composure needs no gateway connection, and on Workers no server at all.

A tour

Rich messages with rsx! and #[view]

use composure::{rsx, view, command::View};

/// A card that counts its likes. The count lives in the button's custom_id.
#[view]
pub fn Card(title: String, likes: u32) -> View {
    rsx! {
        <Container>
            "## " {title.as_str()}
            <Text>"-# " {likes} " likes"</Text>
            <Row>
                <Button primary on:click:like=move |_| Card { likes: likes + 1, title }>
                    "Like"
                </Button>
                <Button url="https://discord.com/developers/docs">"Docs"</Button>
            </Row>
        </Container>
    }
}

Clicking Like re-renders the message with new Props. Every Discord component has a tag, and every tag's attributes are documented.

This is the beginning of the README. Read the rest at the original. Read the full README ↗