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Documentation Index

Fetch the complete documentation index at: https://docs.withsutro.com/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

SLang is the programming language for defining Sutro backends. The purpose of SLang is to provide a simple but powerful language to cleanly and intuitively define entire backends, including entities, logic, and security, without being slowed down by boilerplate, complex syntax, or hard-to-follow logical expressions. The result is a language that makes backend definition easy, avoids the majority of common mistakes, and is intuitive to pick up for humans and AI alike.

Why a new language?

Read about why backend engineering needs a new software language.

Zero-infra philosophy

Read about the “Zero-infra” philosophy behind Sutro.

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Core concepts

SLang is designed around a small set of constructs that map directly to modern backend architecture:
  1. Entities: Persisted database records and relationships.
  2. Schemas: Reusable non-persisted structured types.
  3. Actions: Typed business logic functions.
  4. Triggers: HTTP endpoints, queues, cron jobs, and events that invoke actions.
  5. Security: Subjects, identity fields, groups, roles, and permissions.
  6. Modules: Built-in and local imports for capabilities such as AI and HTTP calls.

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Agent skill

If you’re using an AI coding agent like Claude Code, you can install the official SLang skill to give your agent full knowledge of SLang syntax and semantics: 
npx skills add https://github.com/SutroOrg/sutro-skills --skill slang

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Learn more

Data models

Define entities, fields, and relationships.

Logic & Actions

Write business logic using simple control flow.

Security

Implement robust permissions and auth.

API & Triggers

Expose your logic via HTTP and Queues.

Files & Storage

Upload, persist, and pass documents through backend logic.

Modules

Use built-in AI and HTTP modules or import local helpers.