iii

What is iii?

Software engineering is an exercise in assembling categories of services. Each service has its own internals, its own lifecycle, its own integration story, and its own failure modes. The cost of every new service addition is quadratic. Every new service has potential integration points with every other service.

iii eliminates this integration effort by reducing every new addition to zero. Installing 4 workers or 20 workers is exactly the same. Each worker is simply able to interact with every other worker the moment it is registered with iii. The result is an infrastructure that behaves like a single application and composes effortlessly no matter how much it grows or changes over time.

iii supports any language, and any runtime. It makes a new engineer productive on day one because their mental model never changes from one capability to the next. Likewise AI Agents can reliably reason about an entire system in a single context window because there is one set of primitives to learn and one always-accurate source of truth for what exists. As agents do more of the work of building and operating software, small primitives compound: easier to onboard, cheaper to prompt, faster to extend, simpler to maintain.

Three Primitives

iii's design collapses distributed software into three concepts: Worker, Trigger, Function. Something hosts work, something causes it, something does it.

Workers are processes that register with the iii engine and then register triggers and functions. A TypeScript API service is a worker. A Python data pipeline is a worker. A Rust microservice is a worker. Any functionality can be transformed into a worker with a few lines of code.

Triggers are anything that causes a function to run. A trigger can be a direct call to a function, an HTTP endpoint, a cron schedule, a queue subscription, a state change, a stream event, or anything else. Triggers are declarative: the Worker defines "this function runs when this thing happens," and iii handles routing, serialization, and delivery.

Functions are units of work with a stable identifier (e.g., content::classify, orders::validate). It receives input, does work, and optionally returns output. Functions exist in workers.

By mapping everything a service can do to these three primitives iii creates a development process that is both effortlessly composable, and completely observable.

Quick Start

iii project init myapp    # scaffold a project
cd myapp
iii                       # start the engine

Need to install iii first? Full walkthrough at the Quickstart guide.

SDKs

Language	Package	Install
Node.js	`iii-sdk`	`pnpm add iii-sdk` or `npm install iii-sdk`
Python	`iii-sdk`	`pip install iii-sdk`
Rust	`iii-sdk`	Add to `Cargo.toml`

Agent Skills

Give your AI coding agent full context on iii:

npx skillkit add iii-hq/iii/skills

Skills covering every iii primitive — HTTP endpoints, queues, cron, state, streams, custom triggers, and more. Works with Claude Code, Cursor, Gemini CLI, Codex, and 30+ other agents. See skills/ for the full list.

Console

The iii-console is a developer and operations console for inspecting workers, functions, triggers, queues, traces, logs, and real-time state. See the Console docs for setup and usage.

Repository Structure

Directory	What it is	README
`engine/`	iii Engine (Rust) - core runtime, modules, and protocol	engine/README.md
`sdk/`	SDKs for Node.js, Python, and Rust	sdk/README.md
`console/`	Developer console (React + Rust)	console/README.md
`skills/`	Agent skills for AI coding agents	skills/README.md
`website/`	iii website	website/
`docs/`	Documentation site (Mintlify/MDX)	docs/README.md

See STRUCTURE.md for the full monorepo layout, dependency chain, and CI/CD details.

Examples

See the Quickstart guide for step-by-step tutorials.

Resources

License

The iii is licensed as such:

Directory	License
`engine/`	Elastic License 2.0
`sdk/`	Apache License 2.0
`console/`	Apache License 2.0
`docs/`	Apache License 2.0
`website/`	Apache License 2.0

The engine runtime is licensed under the Elastic License 2.0 (ELv2). All SDKs, CLI, console, documentation, and the website are licensed under the Apache License 2.0.

See CONTRIBUTING.md for additional details.

Motia

Motia