Renyi

Renyi is the scripting language of AI agents: the agent writes it, you review it at a glance, and the program can only do what it declares.

Renyi is the scripting language of AI agents: the language an agent writes and a person reviews at a glance. A Renyi program declares what it may do (needs filesystem.read("data"), network.http("api.example")), the compiler refuses what is not declared, and the runtime admits only that, for the program's dependencies too. Every run can be recorded, replayed and narrated; the project map and the semantic diff are commands; every error carries a fix. The syntax is regular English with one spelling per concept, so that a reviewer reads a program in one pass: effects in the type system, no exceptions, no null, no anonymous functions, and documentation that is part of the grammar. It is a general-purpose language whose first users are people who run automation with Claude Code or Codex and will not run an agent's Python blind.

public function active_adult_emails(path: Path)
  returns List of Email
  or fails with FileError or JsonError
  needs filesystem.read
  purpose: Read users from a JSON file and return the e-mails of active users who are at least 18.

  let text be filesystem.read_text(path) otherwise fail
  let users: List of User be json.parse(text) otherwise fail
  let emails be
    for each user in users
    where user.is_active and user.age is at least 18
    sorted by user.name
    collect user.email
  return emails
end

Install

On Linux and macOS:

curl -fsSL https://raw.githubusercontent.com/renyi-lang/renyi/main/install.sh | sh

On Windows, in PowerShell:

irm https://raw.githubusercontent.com/renyi-lang/renyi/main/install.ps1 | iex

Both download the release for the machine, verify its checksum and put renyi in place; with a Rust toolchain, cargo install renyi builds the same binary. Then:

renyi check program.ry      # every diagnostic with its fix
renyi format program.ry     # the one canonical layout
renyi test program.ry       # every example: line and test block
renyi run program.ry        # main, under the grant it declares

Read

• The cheat sheet: the whole language on one page.
• The reference: every construct with its grammar, its meaning, its static rules with their diagnostic codes and its run-time behaviour; the grammar it quotes.
• The examples: thirty programs, from a greeting to an HTTP service, each in canonical layout.
• The starter pack for agents: a skill file, the MCP configuration and five workflows that do real work, with their tests and recordings.
• Extending Renyi with Rust: a declaration file, a table of natives and a binary of three lines; what the boundary does for them.
• Calling Python from Renyi: a declaration file bound to a Python module by the manifest, one worker per run, what crosses and what fails.
• The positioning: the niche, the four points the language leads with and the comparison with the alternatives; the design decisions, with their reasons, and the other design documents: the syntax sketch, the readability test, the standard library, the agent tooling, the runtime guarantees and the system design.
• The repository: the Rust toolchain, the compiler written in Renyi, the conformance suite and the release procedure. Apache-2.0.