# Koru

> Zig-superset systems language with event continuations, mandatory branch handling, phantom typing, and purity tracking. Pre-alpha — 'only ever been compiled on a single computer.' AI-First framing intentionally tongue-in-cheek.

**Camp:** Unclassified
**Author:** Author anonymous (korulang)
**Implementation language:** Koru (metacircular, bootstrapped through Zig)
**Compilation target:** Zig (then native via Zig's backends)
**Licence:** Unknown
**First seen:** December 2025
**Maturity:** early implementation
**Site:** https://www.korulang.org/
**Repo:** https://github.com/korulang/koru

## Key idea

Koru is a Zig-superset systems language. Every .kz file is valid Zig;
Koru constructs are marked by a ~ leader. The distinctive design move
is event continuations with mandatory branch handling — events
declare their inputs and possible output branches in advance, and
invoking an event requires explicitly handling each branch. Phantom
typing tracks compile-time resources; purity is tracked; the compiler
is metacircular (Koru compiles to Zig). The "AI-First" claim is
architectural (event boundaries aid AI reasoning) rather than
machinery-based — no SKILL.md, AGENTS.md, MCP server, or structured-
JSON diagnostics ship. The compiler itself was authored using
Claude Opus 4.1–4.5 and Sonnet 4.5.

## What it is.

Koru is a pre-alpha Zig-superset systems programming language. Every `.kz` file is valid Zig; Koru constructs are marked by a `~` leader. The distinctive design move is event continuations with mandatory branch handling — events declare their inputs and possible output branches in advance, and invoking an event requires explicitly handling each branch. Phantom typing tracks compile-time resources; purity is tracked through the type system; the compiler is metacircular (Koru compiles to Zig). The author is anonymous behind the `korulang` GitHub org and Twitter account; the project's site lists Claude Opus 4.1–4.5 and Sonnet 4.5 as the models that authored the compiler itself.

The site's tagline is intentionally tongue-in-cheek: "The Hyper-Performant AI-First Postmodern Zero-Cost Fractal Metacircular Phantom-Typed Auto-Disposing Monadic Event Continuation Language with Semantic Space Lifting and Event Taps." Underneath the buzzword cascade, the README is candid about state: *"Pre-Alpha — Koru is pre-alpha. It has only ever been compiled on a single computer. Use and testing at your own risk."* No `SKILL.md`, `AGENTS.md`, MCP server, or structured-JSON diagnostics ship. The closest planned agent-facing surface is the Compiler Control Protocol (CCP), described as "soon" — a Koru-internal proposal, not the Model Context Protocol.

## Why it's here.

The catalogue includes Koru as a marker of the position where "AI-First" became a tagline trope. The architectural claim (event boundaries provide bounded contexts that aid AI reasoning) is a real design move; the buzzword-cascade tagline is real satire; and the catalogue's unclassified bucket exists for projects whose camp placement isn't yet evidenced by shipped agent-authoring machinery. Companion to Valea and Spec: a real project with substantive design, candidly aware of its pre-alpha state, where the "AI-First" claim is a language-architecture argument rather than a tooling commitment. The pre-alpha disclosure quoted above is the editorial centre of gravity — the rest of the entry exists to give it context.

## Design DNA

- **[Valea](https://agentlanguages.dev/languages/valea.md)** *(Unclassified)* — Companion in the unclassified bucket. Both stake an 'AI-native systems programming language' position with substantive design proposals but limited public evidence and no agent-authoring machinery shipped. Valea is a Rust MVP announced on Hacker News with JSON diagnostics planned; Koru is a Zig-superset metacircular compiler with event continuations and an explicitly tongue-in-cheek marketing voice.
- **[Spec](https://agentlanguages.dev/languages/spec.md)** *(Unclassified)* — Adjacent unclassified entry on the 'architecture as AI-friendliness' axis. Spec proposes a two-domain IR for multi-agent collaboration; Koru proposes architectural primitives (event boundaries, mandatory branch handling) that aid AI reasoning at the language level. Both make architectural claims about AI-friendliness without shipping agent-authoring tooling.

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HTML version: https://agentlanguages.dev/languages/koru/
Catalogue index: https://agentlanguages.dev/llms.txt
Catalogue homepage: https://agentlanguages.dev/index.md