Readable syntax
Use direct forms such as let, show, fn, and for … in with minimal punctuation.
Complete Toolchain
Batteries included for modern engineering
Practical tooling for scripts, automation, services, data, and optional model-assisted workflows.
Decentralized Packages
Install third-party packages from GitHub repository references and declare project dependencies in sesi.json.
Script-first CLI
Run .sesi files directly, evaluate snippets, inspect tokens and ASTs, or perform dry-run checks.
Syntax and Symbol Checks
Validate syntax, compilation, and symbols without execution using sesi -c file.sesi.
Parallel Workflows
Use multi_req for parallel function execution and spawn for explicit process work when permitted.
Runtime Profiling
Collect runtime measurements with sesi --profile file.sesi and built-in profiling helpers.
Standalone Releases
Use packaged Sesi executables on Linux, macOS, and Windows when you do not want a separate Node.js installation.
Language runtime
A small language with a complete core.
Sesi covers everyday programming directly: values, functions, conditions, loops, collections, modules, errors, and top-level execution.
Read the language guideOptional types
Let inference handle simple values or annotate parameters, variables, and return types where contracts should be explicit.
Collections and transforms
Work with arrays and objects using indexing, iteration, and built-ins such as map, filter, reduce, and find.
Pipelines
Pass a value into the next function with Sesi's pipe operator, keeping multi-step transformations readable from left to right.
Explicit modules
Use allow to import selected exports or bind a module behind a namespace.
Error recovery
Handle operations that may fail with try / catch, including file, network, parsing, and permission errors.
Standard capabilities
Useful systems work without assembling a framework.
The runtime includes practical capabilities for files, data, networking, media, and automation. Host-sensitive operations remain subject to Sesi's security controls.
Files
Filesystem and archives
Read, write, append, copy, move, list, and safely trash files inside allowed paths. Work with supported archive formats under sandbox rules.
read_file · write_file · list_dirNetwork
HTTP clients and services
Request remote resources from scripts and build native HTTP or WebSocket services when the execution mode permits server access.
web_get · std/api · WebSocketData
Embedded document storage
Create JSON document collections with CRUD operations and optional password-based encryption at rest.
allow "std/db" in with {db_open}Visual
SVG, pixels, and images
Generate code-native graphics, manipulate pixel data, inspect images, and write image output through built-in drawing and media helpers.
std/draw · image helpersAudio
Audio and music
Synthesize audio, work with sample data, use music-theory helpers, and connect media workflows to native tools when allowed.
std/audio · std/theoryAutomation
Browser and native bridges
Automate browsers or bridge into Python and JavaScript for trusted local workflows. These host-integrated capabilities are blocked in safe mode.
std/browser · python · jsSecurity is part of the runtime contract. Path checks and safe-mode restrictions apply before sensitive host operations run.
Developer workflow
Inspect every stage from source to runtime.
The CLI exposes parsing, compilation, validation, profiling, and execution controls directly—useful for learning the language and diagnosing real programs.
CommandPurpose
sesi file.sesiRun a source file.sesi -e "…"Evaluate a small inline program.sesi -c file.sesiCheck syntax, compilation, and symbols without executing.sesi --tokensInspect the lexer token stream.sesi --astView the parsed abstract syntax tree.sesi -bdPrint bytecode disassembly.sesi --profileCollect runtime performance measurements.sesi --timeoutRun with a caller-selected execution deadline.One connected toolchain
Use the interface that fits the work.
Move between the CLI, Sesi Studio, editor support, standalone releases, and the browser syntax demo without changing the language.
CLI
Run scripts, inspect compilation stages, manage packages, and control execution.
Sesi Studio
A dedicated browser-based IDE with editor, terminal, timeline, themes, and extensions.
VS Code support
Use the packaged syntax extension for Sesi source files in an existing editor workflow.
Standalone binaries
Run packaged releases on macOS, Windows, and Linux without a separate Node.js installation.
Optional reasoning
Model calls are a capability, not the language's identity.
Write ordinary deterministic Sesi programs first. When a task benefits from interpretation or generation, add prompt, model, structured-output, memory, or tool primitives where they are needed.
Explore optional reasoningPackages
Git-centric dependencies.
Install an owner/repository reference into sesi_modules and record it in sesi.json.
$ sesi install owner/repo#refStart building
Install the runtime or explore the syntax first.
The full CLI is for real programs; the browser demo is a lightweight way to get familiar with core Sesi forms.