Siren Call is a Discord bot for pinging people with arithmetic. Instead of picking a role and hoping for the best, you write a tiny script that says exactly who should get pinged (@Teachers minus @John Doe, everyone who joined before Thursday, whoever's been talking in this channel), preview the result, and send.

It's built so you can plug in any language or interface you want. Out of the box it can do Sing and Lua, with Sing as the default.

Sing is a custom language made for pinging. It's Turing complete, has a bootstrapped compiler, and was fully vibecoded by yours truly.

PING @Teachers - @John Doe SAYING "Class is cancelled"

1. Run /ping. A Sing editor opens. Want Lua? /ping language:Lua. Got a one-liner? /ping script:....
2. Your script runs in a sandbox and comes back with a set of people and a message.
3. You get a private preview: who'd be pinged, and whether you're actually allowed to ping them.
4. Hit Send. The bot mentions exactly those people and nobody else.

Nothing goes out until you press Send. Previews expire after five minutes.

LET audience = (@Teachers OR @Café crew) - @John Doe

IF COUNT(audience) > 0 THEN
  PING audience SAYING "Class is cancelled"
ELSE
  PING NONE SAYING "Nobody to notify"
END

• @Name is a member or a role. Spaces and accents are fine, case doesn't matter, and the longest match wins (@John Doe won't grab @John). Quote anything weird: @"Teachers + Staff".
• @everyone is everyone who can see the channel. @here is whoever's online or on Do Not Disturb. CALLER is you.
• + / OR, -, AND, XOR, and NOT do what you'd expect on sets.
• LET, IF, FOR, WHILE, FUNC, lists, records, optional runtime types, and exact arbitrary-precision integers.
• MEMBERS is everyone in the channel, MESSAGES is the last ten messages. Loop over them.
• Keywords are case-insensitive. ping @teachers saying "hi" works.

Errors point at the exact spot and suggest fixes:

Line 1, column 6: Unknown recipient “Teahcers” in this channel.

PING @Teahcers SAYING "Hello"
     ^^^^^^^^^

Did you mean @"Teachers"?

Read more: language guide · spec · CLI and embedding · the compiler.

Sing is a real language, so it runs on its own too:

pnpm run sing examples/counter.sing               # 9007199254741004, exactly
pnpm run sing examples/functions.sing             # closures, records, TYPE aliases
pnpm run sing:compile examples/functions.sing --run
pnpm run sing:bootstrap

sing:compile runs the compiler, which is written in Sing and emits JavaScript. sing:bootstrap uses that compiler to compile itself three generations deep and checks the outputs are identical.

return {
  recipients = everyone() - (role("L1") + role("L2")) - joined_after("2026-09-18"),
  message = "Class is cancelled"
}

Bare names resolve to roles and members, so that's also everyone() - (L1 + L2) - .... caller is you. See examples/ for more.

A language is one interface:

interface SelectionLanguage {
  readonly id: string;
  compile(source: string, context: CompileContext): Promise<PingPlan>;
}

context is a plain snapshot of the channel (members, roles, recent messages). PingPlan is recipient IDs plus a message. Implement it under src/languages/<id>/, register it in src/languages/index.ts, add it to the /ping language option, and you're done. The host re-validates whatever you return, so an adapter can't hand back people who aren't in the channel. Adapters never touch Discord objects or the bot token. AGENTS.md has the full checklist.

You need Node.js 24.17+, pnpm 10.33 (corepack enable if you don't have it), and a Discord application from the Developer Portal.

pnpm install --frozen-lockfile
cp .env.example .env     # then fill in DISCORD_TOKEN, DISCORD_APPLICATION_ID, DISCORD_GUILD_ID
pnpm run register        # registers /ping in that one guild
pnpm run dev             # build + start

In your application's Bot tab, turn on:

• Server Members Intent: required, it's how the bot knows who's in the channel.
• Presence Intent: for @here.
• Message Content Intent: if you want scripts to see the text of recent messages. Without it they still see who posted, just with empty content.

Invite it with bot and applications.commands scopes and permissions 19456 (View Channels, Send Messages, Embed Links). It doesn't need Administrator, Manage Roles, or Mention Everyone:

https://discord.com/oauth2/authorize?client_id=YOUR_APPLICATION_ID&scope=bot%20applications.commands&permissions=19456

The bot uses a Gateway connection, so there's no web server, interactions endpoint, or public key to set up. Keep the process running; pnpm start runs the built output. Commands are registered per-guild and only /ping is touched, so it plays nice with other bots.

Who can ping whom. The bot checks your real channel permissions (overwrites included) and its own. If your selection covers everyone who can see the channel, you need Mention Everyone, no matter how you spelled the selection. Anything smaller is allowed. This is a full-audience rule, not anti-spam; everyone-minus-one still goes through.

What gets sent. Individual user mentions, batched at 2,000 characters / 100 mentions per message, with the message text repeated in each batch. Typing @everyone or a role in the message text doesn't expand the recipient list. If a batch fails, the bot tells you how far it got and doesn't retry.

Previews. One use, by the person who made it, in the channel it was made in, within five minutes. Sending rechecks permissions and drops anyone who left or lost access in the meantime; it never adds people. A new preview replaces your old one. Restarting the bot expires all of them.

Context. Scripts get the last ten messages in the channel (author, content, timestamp, bot flag). That's the same history anyone who can run /ping there can already scroll. Message content never affects who's eligible.

Sandboxing. Scripts are untrusted. Each one runs in a fresh worker with an empty environment (no token, no filesystem, no network), a kill timer, and a heap cap. Lua gets a stripped environment with no io, os, require, debug, or load; its only host callback turns a name into an ID. Sing interprets a closed syntax tree and never evaluates JavaScript. Limits are in src/selection.ts:

Workers are a resource boundary, not an OS sandbox. If you're going to run this for strangers, put it in a container.

Supported: text and announcement channels. Not supported: threads, voice chat, DMs, saved scripts.

pnpm run check      # lint, format, typecheck, tests
pnpm test
pnpm run preview examples/class.sing examples/context.json
pnpm run preview examples/class.lua examples/context.json lua

Tests run against dist/ because the Lua worker resolves its runtime relative to compiled output; Vitest builds first, so a bare vitest is fine. CI runs pnpm run check with no bot token. For a live smoke test, run /ping in your server with the default script, check the preview, send, and confirm it only mentions you.

MIT