Reasonix

Reasonix is an open-source, MIT-licensed AI coding agent built specifically for DeepSeek's prefix-cache architecture, available as a CLI/TUI, desktop app, local browser UI, and VS Code extension. It is developed in public on GitHub under the esengine/DeepSeek-Reasonix repository, written in Go, and distributed as a single CGO-free static binary that runs on macOS, Linux, Windows, and WSL. The project homepage reports 29,800+ GitHub stars and 98 contributors as of the latest data.

What It Is

Reasonix is a terminal-first AI coding agent that wraps DeepSeek models in a cache-aware agentic loop. Unlike generic agent frameworks that rebuild the full prompt each turn, Reasonix keeps the conversation history append-only and byte-identical so DeepSeek's prefix cache can replay prior context at a fraction of the cost. The project describes this as achieving 90%+ cache hit rates on long sessions, with input-token costs collapsing to approximately one-fifth of a cold-start equivalent. It supports any OpenAI-compatible endpoint via config, not just DeepSeek, making it a general-purpose but DeepSeek-optimized harness.

Cache-First Architecture

The core design decision in Reasonix is deterministic, append-only context serialization. Every request replays the exact same byte-for-byte prefix so the model only computes what is new. The project documents that:

• Startup injects a small, stable environment summary
• Stale tool output is snipped/pruned before summary compaction
• Automatic compaction starts at 80% of model context by default (configurable 65–85%)
• Volatile state like timestamps is never injected into the stable prefix

This architecture means sessions get cheaper per turn rather than more expensive, which is the opposite of most agent loops.

Multi-Surface Deployment

Reasonix runs the same local engine across four surfaces:

• CLI/TUI — interactive full-screen terminal interface with Plan, Ask, Auto, and YOLO modes; installable via npm i -g reasonix or Homebrew
• Desktop app — native app for macOS, Linux, and Windows with visual session management, MCP status, checkpoints, tool approvals, and IM bot connections (Feishu, Lark, WeChat)
• Browser UI — reasonix serve starts a local web frontend at 127.0.0.1:8787 with optional token or password auth for remote sharing
• VS Code extension — connects to reasonix acp (Agent Client Protocol) and does not bundle the CLI; available on Visual Studio Marketplace and Open VSX Registry

MCP and Plugin System

Reasonix is a first-class MCP (Model Context Protocol) client. Plugins are declared in reasonix.toml and support stdio, SSE, and Streamable HTTP transports. External server tools are merged into a single registry under a prefix (mcp__<server>__<tool>). MCP prompts become slash commands and MCP resources are referenceable via @server:uri. The project also reads .mcp.json files using the Claude Code mcpServers schema, making it compatible with existing MCP configurations.

Subagents, Skills, and Plan Mode

Beyond single-turn coding tasks, Reasonix ships with built-in subagents for explore, research, review, and security-review workflows. Markdown skill scripts with isolated tools extend the agent's capabilities. Plan mode (/plan) asks the model to plan before acting, with permissions and the workspace sandbox still governing every tool call. The sandbox enforces file-write boundaries using OS-level backends (Seatbelt on macOS, bubblewrap on Linux) and resolves symlinks to prevent path-traversal escapes.

Update: Desktop v1.19.5

The current official release is v1.19.5, published on 2026-08-03, covering the desktop app, CLI, npm package, and Homebrew tap. The 1.x line is a Go rewrite of the earlier 0.x TypeScript codebase; the 0.x line (npm i -g reasonix@0.53.2) is deprecated and no longer maintained. The repository's default branch is main-v2, and the project reports 2,871 merged PRs. Windows installers are code-signed through SignPath.io with a certificate provided by the SignPath Foundation.