ilo

ilo

A programming language AI agents write, not humans. Named from Toki Pona for "tool".

Experimental pre 1.0 language, expect breaking changes. See STABILITY.md for what's stable vs in-flight. Open-sourced February 2026.

Python                                    ilo
─────                                     ───
def total(price, quantity, rate):          tot p:n q:n r:n>n;s=*p q;t=*s r;+s t
    sub = price * quantity
    tax = sub * rate
    return sub + tax

4 lines, 30 tokens, 90 chars              1 line, 10 tokens, 20 chars

0.33× the tokens. 0.22× the characters. Same semantics. Type-verified before execution.

Why

AI agents pay three costs per program: generation tokens, error feedback, retries. ilo cuts all three:

• Shorter programs - prefix notation eliminates parentheses; positional args eliminate boilerplate
• Verified first - type errors caught before execution; agents get ILO-T004 not a stack trace
• Compact errors - one token, not a paragraph; agents correct faster, fewer retries

Install

curl -fsSL https://ilo-lang.ai/install.sh | sh

iwr -useb https://ilo-lang.ai/install.ps1 | iex

npm i -g ilo-lang

# or run without installing
npx ilo-lang 'dbl x:n>n;*x 2' 5

cargo install ilo

npx skills add ilo-lang/ilo

All install methods →

Quick start

# Inline
ilo 'dbl x:n>n;*x 2' 5                    # → 10

# From file
ilo program.ilo functionName arg1 arg2

# Verb form (cargo / go / zero style; bare positional still works)
ilo run program.ilo arg1 arg2             # run
ilo check program.ilo                     # verify only - exit 0 if clean
ilo build program.ilo -o ./bin            # AOT compile

Tutorial: Write your first program →

Editor support

Syntax highlighting, snippets, and -- comment handling for .ilo files ships in extensions/vscode/. Install into Cursor with cd extensions/vscode && npm run install:cursor. VS Code marketplace publish is tracked separately.

Versioning

CalVer. Releases are YY.M (e.g. 26.5), patches within a month are YY.M.P (e.g. 26.5.1). The version string carries recency: an agent loading ilo spec --json ai knows which spec applies from the version alone, no changelog lookup needed. Token-conservative (manifesto principle 1) vs semver's 0.12.1.

Branches