Language, runtime, and services for backend workflows and AI agents

Hot Dev is an open source language, runtime, and set of services for event handlers, schedules, AI agents, MCP tools, and long-running tasks. It includes execution tracing, a local development runtime, and deployment through hot deploy.

This repository contains the Hot compiler, VM, standard library, hot CLI, API, web app, scheduler, event worker, task worker, and LSP server. Public Hot packages are under hot/pkg, including hot-std and provider/tool integrations.

Hot Dev Cloud hosts Hot deployments. Its deployment infrastructure and private operational tooling are outside this repository.

• Website: hot.dev
• Download: hot.dev/download
• Documentation: hot.dev/docs
• License: Apache-2.0

This example shows how Hot wires webhooks, events, schedules, and MCP tools with the same meta mechanism:

::myapp ns
::http ::hot::http
::uri ::hot::uri

// Receive a webhook, then fan out through an event.
on-signup
meta {
    webhook: {service: "leads", path: "/signup"},
}
fn (request) {
    send("lead:new", request.body)
    {ok: true}
}

// React to the event: score the lead and route it.
qualify-lead
meta {on-event: "lead:new"}
fn (event) {
    score score-lead(event.data)
    if(gte(score, 0.7),
        send("lead:qualified", event.data),
        send("lead:nurture", event.data))
}

// Run on a schedule.
weekly-summary
meta {schedule: "every monday at 9am"}
fn (event) {
    post-pipeline-summary()
}

// Expose a function as an MCP tool.
get-forecast
meta {
    mcp: {
        service: "weather",
        description: "Get the weather forecast for a location",
    },
}
fn (location: Str): Vec {
    loc ::uri/encode(location)
    response ::http/get(`https://wttr.in/${loc}?format=j1`)
    response.body.weather
}

Install the latest released CLI:

curl -fsSL https://get.hot.dev/install.sh | sh

Or build from source:

cargo build --release --bin hot

hot init
hot dev --open    # start the local dev stack and open the dashboard

Common commands:

hot run file.hot          # Run one Hot file
hot check                 # Type/check project source
hot test                  # Run Hot tests
hot deploy                # Build and deploy to Hot Dev Cloud
hot ai add                # Add AGENTS.md + bundled Hot skills for AI tools

hot ai add installs the bundled Hot language and AI agent skill snapshots.

• hot-demos: runnable Hot projects, including AI agent examples.
• hot-skills: Hot language skills for AI coding tools.
• setup-hot: GitHub Action for installing Hot in CI.
• hot-js: JavaScript/TypeScript SDK for Hot.
• hot-python: Python SDK for Hot.
• hot-vsx: VS Code and Cursor extension for Hot.

crates/
  hot/                    # Core language, runtime, storage, and internals
  hot_cli/                # CLI binary
  hot_api/                # API service
  hot_app/                # App/Dashboard
  hot_worker/             # Event worker
  hot_task_worker/        # Long-running task and container worker
  hot_scheduler/          # Scheduled function runner
  hot_lsp/                # LSP server
  hot_docs/               # Documentation and package rendering
  hotbox/                 # Helper binary for containerized file access
hot/
  pkg/                    # Public Hot packages
  test/                   # Hot language/package tests
resources/                # Docs, app assets, migrations, init templates
scripts/                  # Build, package, docs, and integration helpers
docker/                   # Public release build/package Dockerfiles

crates/ is the Rust workspace (compiler, runtime, and services). The top-level hot/ tree holds Hot source: the publishable packages in hot/pkg and the Hot language and package tests.

Prerequisites:

• Rust (version pinned in rust-toolchain.toml)
• Docker (optional for most development; required for ::hot::box container tasks and release packaging)

Common checks:

cargo fmt --check
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
cargo test --workspace --all-targets --locked
cargo run --locked --bin hot -- check --ctx hot/ci.ctx.hot
cargo run --locked --bin hot -- test -c hot.test.hot --ctx hot/ci.ctx.hot

Run the local development stack:

cargo run --locked --bin hot -- dev

Install optional git hooks:

./scripts/setup-git-hooks.sh

Releases are tagged from resources/version.txt; automation lives in .github/workflows/release.yml.

See CONTRIBUTING.md for how to build, test, and submit changes. To report a security issue, follow the process in SECURITY.md rather than opening a public issue.

Copyright 2025-2026 Hot Dev, LLC.

Hot is licensed under the Apache License, Version 2.0. See LICENSE and NOTICE. Brand usage for the Hot Dev name and artwork is covered separately in BRAND.md.