SESI LANGUAGE SPECIFICATION
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Sesi Programming Language Roadmap

Version 1.0 - Foundation (Complete)

Status: Complete V1.0 implementation

Ready for: Exploration, learning, building prototypes

Not ready for: Production systems (until v2.0 with error handling)

Next milestone: V1.1

Core Language Features ✅

  • Variables and bindings (let) (const is deprecated)
  • Functions with parameters and types
  • Control flow (if/else, while, for, try/catch)
  • Operators (arithmetic, logical, comparison)
  • Arrays and objects
  • Type system with inference
  • Comments (// and /\ \/)
  • String concatenation
  • Error handling (try/catch blocks)

Integrated Reasoning Features ✅

  • Prompt blocks
  • Reasoning model calls (model())
  • Structured output (structured_output())
  • Tool calling (tool_call())
  • Stateful context management (memory)

Built-in Functions ✅

  • print, type, str, num, bool
  • len, push, pop, join, split
  • range, keys, values
  • read_file, write_file
  • spawn, exec (Concurrency & Systems)
  • time, random (Utilities)
  • Array and object operations

Tooling ✅

  • Lexer and parser
  • Tree-walking interpreter
  • CLI executable (sesi)
  • Examples (22 programs)
  • Documentation

Limitations

  • Interpreter is Single-threaded (use spawn() for concurrency)
  • No async/await
  • Blocking Reasoning calls
  • Limited error messages
  • No pattern matching
  • No generics or custom types

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Version 1.5 - Improvements (Complete)

Status: Complete V1.5 implementation

Ready for: File manipulation and process orchestration

Not ready for: Massive-scale production (until v2.0 bytecode)

Next milestone: V2.0

Improvements & Features ✅

  • Systems Builtins: spawn, exec, time, random
  • Concurrency: Async polling via file locks for completion and MAX_TOKENS
  • Image Generation primitive (image) and Config blocks (ratio, size)
  • File Management Builtins: list_dir, write_image
  • Documentation improvements (Extensive Markdown guides)
  • Bug fixes (tool_call argument passing resolved)
  • Simple error recovery (Parser synchronization)
  • Implicit statement termination for blocks ending in }
  • Temporal Context Injection for reasoning calls
  • Concurrency capabilities (File-based lock pattern)
  • API reference (BUILTINS.md)
  • Tutorial: Getting started (QUICKSTART.md)
  • Cookbook: Common patterns (WRITING_SCRIPTS.md)

Deferred to V2.0 ⏳

  • Better error messages with line numbers and stack traces
  • REPL (Read-Eval-Print Loop)
  • String escape sequences & Multiline strings
  • Comments preservation (for docs)
  • Type hints in function signatures
  • Performance optimizations
  • Tutorial: Writing scripts

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Version 2.0 - Advanced Concurrency & Logic (Q3-Q4 2026)

Focus: Advanced reasoning features and native concurrency

Async/Await Support

  • async/await syntax (language level)
  • Parallel reasoning calls (native)
  • Promise-like operations
  • Concurrent execution (Multi-process via spawn)

Advanced Features

  • Streaming responses
  • Extended thinking
  • Multi-step workflows
  • Tool composition and piping
  • Custom tool definitions
  • Function calling with automatic orchestration
  • Web search grounding

Memory System

  • Long-term memory with embeddings
  • Memory search by similarity
  • Context window management
  • Automatic summarization
  • Persistent storage (file-based)

Error Handling

  • finally blocks (try/catch completed in V1)
  • Custom error types
  • Error recovery strategies
  • Retry logic with exponential backoff
  • Timeout handling

Performance

  • [~] Bytecode compilation (VM + compiler foundation: expressions, loops, functions ✅ — closures, try/catch, imports pending)
  • Logic caching
  • Token counting and cost estimation
  • Lazy evaluation

New Built-ins

  • String functions (to_upper, to_lower, trim, slice, swap)
  • Array functions (map, filter, reduce, find, etc.)
  • Math functions (sqrt, sin, cos, floor, ceil, etc.)
  • Date/time functions
  • JSON parsing and serialization
  • HTTP client (get, post)

Module System

  • import/export statements
  • Standard library modules (std/math, std/time, etc.)
  • Third-party package management
  • Lib support

Tooling

  • Debugger with breakpoints
  • Profiler for performance analysis
  • AST visualization
  • Token stream visualization
  • Type checking tool
  • Linter and formatter (Native, no external dependencies)

Examples

  • Web scraper with reasoning analysis
  • Command line utility expansion
  • Chatbot with memory
  • Data pipeline with reasoning
  • API server (with async)

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Version 3.0 - Robust Logic Frameworks (2027)

Focus: Complete language tooling

Technical Frameworks

  • Advanced scripting definition models
  • Logic composition and chaining
  • Extended process collaboration
  • Communication protocols
  • Persistence layer

Knowledge Base

  • Vector database integration
  • Semantic search
  • Knowledge graph support
  • RAG (Retrieval-Augmented Generation)
  • Document indexing

Advanced Patterns

  • Sub-process execution workflows
  • Modular scripting decomposition
  • Retry safety check loops
  • Deep AST reflection
  • Human-in-the-loop prompts

Ecosystem

  • Package registry
  • Community extensions
  • Plugin system
  • API server template
  • Dashboard/UI toolkit

Examples

  • Automated code formatting process
  • Document processor (PDF, DOCX)
  • Code generation and testing
  • Data analysis pipeline
  • Multi-process reasoning debate

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Version 4.0+ - Vision (2027+)

Focus: Maturity, optimization, and specialization

Potential Features

  • Compilation to JavaScript/WASM
  • JIT compilation for hot paths
  • Distributed execution
  • Cross-model orchestration (Gemini, Claude, etc.)
  • Vision model integration
  • Audio processing
  • Real-time streaming
  • Genetic programming / AutoML
  • Formal verification
  • Type refinement system

New Language Constructs

  • Pattern matching
  • Generics and templates
  • Traits/interfaces
  • Macros
  • DSL support
  • Concurrent primitives (channels, mutexes)

Performance

  • LLVM backend option
  • WebAssembly compilation
  • GPU acceleration
  • Distributed computing

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Feature Priority Matrix

Feature Priority V1 V2 V3 V4+
Basic syntax 🔴 High ✅
Functions 🔴 High ✅
Reasoning calls 🔴 High ✅
Error handling 🔴 High ✅ ⏳
Async/await 🔴 High ⏳
Streaming 🟡 Medium ⏳
Process Logic 🟡 Medium ⏳
Knowledge base 🟡 Medium ⏳
Module system 🟡 Medium ⏳
Debugger 🟢 Low ⏳
Compilation 🟢 Low ⏳
GPU support 🟢 Low ⏳

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Release Timeline 

2026 Q2
└─ v5 - Polish & stabilize

2026 Q3-Q4
└─ v2.0 - Async & advanced APIs

2027 Q1-Q2
└─ v3.0 - Language Ecosystem

2027 Q3+
└─ v4.0+ - Mature compilation

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Community & Contribution

Planned Community Activities

  • Public GitHub repository
  • Discord/Slack community
  • Monthly community calls
  • RFCs (Request for Comments) for major features
  • Contribution guidelines
  • Code of conduct

How to Help (When Open Source)

  • Test programs and report bugs
  • Contribute documentation
  • Submit examples
  • Propose language features
  • Implement built-in functions
  • Build tools and extensions

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Backwards Compatibility

Stability Guarantee

  • v1.x → v1.y: Full backwards compatibility
  • v1.x → v2.0: Mostly compatible, deprecation warnings for breaking changes
  • v2.x → v3.0: New features, old syntax still works

Deprecation Policy

  1. Announce deprecation (1 version ahead)
  2. Show warnings in compiler
  3. Provide migration guide
  4. Remove in next major version

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Open Questions & Design Discussions

For the Community

  1. Should we support object-oriented programming (classes, inheritance)?
  2. Should we add pattern matching or keep it simple?
  3. Should memory be file-based by default or in-memory?
  4. How should we handle multi-model orchestration?
  5. Should processes be stateful or functional?

Technical Decisions

  • Type system: Gradual or strict?
  • Concurrency: Async/await or coroutines?
  • Module system: Centralized registry or decentralized?
  • Error handling: Exceptions or Result types?

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Performance Goals

Metric V1 V2 V3
Startup time <100ms <100ms <50ms
Simple expression eval <1µs <100ns <10ns
Function call overhead <10µs <1µs <100ns
Reasoning latency 2-5s (API) 2-5s 2-5s
Memory usage <50MB <50MB <100MB

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Inspiration & References

Language Design

  • Python: Simplicity, readability
  • Lua: Lightweight, embeddable
  • JavaScript: Functions as first-class values
  • Go: Clear error handling
  • Rust: Type safety, memory safety

Code Control

  • CLI utilities: Direct data piping
  • Shell scripting: Execution transparency
  • Modern SDKs: Model abstraction

Community

  • Rust community: Welcoming, inclusive
  • Python community: Documentation focus
  • Go community: Simplicity first

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Conclusion

Sesi is designed to evolve with reasoning needs. The roadmap balances:

  • Simplicity (v1: core features only)
  • Power (v2: advanced reasoning and extended functionality)
  • Maturity (v3: comprehensive libraries and frameworks)
  • Scale (v4+: production readiness and compilation)

The journey from v1 (interpreter) to v4+ (distributed compiler) maintains backward compatibility while adding power where needed.

Current focus: Ship v2.0 with native async/await and advanced reasoning patterns.

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See Also