The Future of
Programming

Coding made easy. Build complex systems with basic commands and model interactions.

Sesi is a dedicated systems language designed for resilient stateful applications. No more boilerplate, just pure creativity and logic. Harness first-class reasoning primitives and distributed coordination natively.

Download Sesi v1.2.2 View Docs

build_site.sesi

let page_title = "Sesi"
let tagline = "Coding made easy. Build complex systems with basic commands and model interactions."

print "Generating Sesi landing page..."

# First-class reasoning primitive invoked natively
let html = model("gemini-3.1-pro-preview") 
    {"temperature": 0.2, "max_tokens": 8192} 
    {"Create a stunning landing page for Sesi."}

write_file("index.html", html)
print "Website successfully built!"
exec("start index.html")

Language Capabilities

{}

Concise Syntax

Write less, do more. Sesi's syntax is stripped of boilerplate, allowing you to express complex logic and model interactions in plain text .sesi files.

🧠

First-Class Reasoning

LLM calls aren't SDK afterthoughts. They are native language primitives. Invoke models directly within your control flow just like standard functions.

⚡

Distributed Coordination

Built for the modern network. Sesi natively handles distributed execution, allowing seamless coordination across multiple nodes without external message brokers.

💾

Resilient State

Develop resilient stateful applications out of the box. Sesi automatically manages execution state, ensuring your long-running processes survive interruptions.

🌳

Tree-Walking Interpreter

Powered by a robust tree-walking interpreter, Sesi evaluates Abstract Syntax Trees directly, providing predictable execution and straightforward debugging.

⚙️

Systems Language

A true systems language for the AI era. Sesi provides low-level control over execution environments while maintaining high-level abstractions for reasoning.

Execution Model

How Sesi Runs

Sesi operates on a unique execution model tailored for AI-driven logic. Unlike traditional compiled languages, Sesi utilizes a highly optimized tree-walking interpreter that evaluates .sesi files line-by-line. This allows for dynamic state injection and real-time reasoning adjustments.

Phase	Description
Lexing & Parsing	Converts plain text `.sesi` files into an AST.
State Hydration	Loads resilient state from previous execution halts.
Tree-Walking	Interpreter traverses the AST, executing basic commands.
Reasoning Yield	Execution pauses natively when awaiting model inference.

interpreter.ts

ai-runtime.ts

// Sesi Internal Tree-Walking Interpreter
private async evaluateExpression(expr: Expression): Promise<RuntimeValue> {
    switch (expr.type) {
        case 'ModelCallExpression':
            // First-class reasoning primitive
            return await this.evaluateModelCall(expr);
        
        case 'Assignment':
            return await this.evaluateAssignment(expr);
            
        case 'StructuredOutputExpression':
            // Natively handles AI structured outputs
            return await this.evaluateStructuredOutput(expr);
    }
}

// AI Runtime - Integration with Gemini API
export class AIRuntime {
    async callModel(request: AIRequest): Promise<AIResponse> {
        const client = this.client;
        
        // Handle image generation models dynamically
        if (request.model.includes('image')) {
            const configObj: any = { responseModalities: ["IMAGE"] };
            if (request.temperature !== undefined) configObj.temperature = request.temperature;
            
            const result = await client.models.generateContent({
                model: request.model,
                contents: fullPrompt,
                config: configObj,
            });
            return result;
        }
    }
}

Quickstart

bash

# 1. Install the Sesi toolchain
git clone https://github.com/Misterscan/Sesi.git
cd Sesi
npm install

# Unlock the `sesi` command
npm install -g

# 2. Create a new Sesi file
touch hello.sesi

# 3. Write your first program
echo "print 'Hello, Sesi!'" > hello.sesi

# 4. Run the tree-walking interpreter
sesi hello.sesi

> Hello, Sesi!

Zero to Hero in Minutes

Getting started with Sesi is incredibly straightforward. Because Sesi is a standalone programming language, there are no complex dependencies, no heavy SDKs to configure, and no boilerplate to write.

Your .sesi files contain everything needed to orchestrate complex, resilient stateful applications. Just write your logic, invoke your models, and let the interpreter handle the rest natively.

Read the Official Docs

The Future of Programming