A curated, verified, cross-vendor directory of AI agent harnesses — the runtime scaffolding that turns a model into an agent.
◆ 74 harnesses profiled · 9-axis capability schema · last verified 2026-07-08
Google's fully open-source (Apache-2.0) terminal agent with a generous free tier, distinguished by built-in Google Search grounding, an extensions ecosystem bundling prompts/MCP servers/commands, GEMINI.md context files, checkpointing, and real-time voice mode.
OpenAI's open-source (Apache-2.0) Rust-rewritten terminal coding agent, distinguished by kernel-level OS sandboxing (Apple Seatbelt on macOS, Landlock/seccomp on Linux), a 272K-1M token context with GPT-5.x Codex models, MCP support, and cloud handoff to Codex web tasks.
Mario Zechner's radically minimal MIT/TypeScript harness (~68k stars): four tools (read/write/edit/bash), a ~300-word system prompt, deliberately no built-in MCP/subagents/permission-popups, with everything else added via TypeScript extensions, skills, and npm/git-shareable packages across interactive, print/JSON, RPC, and SDK modes.
Alibaba's Apache-2.0 terminal agent (originally a Gemini CLI fork) optimized for Qwen3-Coder models, distinguished by broad provider flexibility (OpenAI/Anthropic/Gemini/Qwen APIs plus Ollama/vLLM local models), skills/subagents primitives, headless mode, and TypeScript/Python/Java SDKs.
Kilo's open-source terminal agent (Kilo CLI 1.0, built on the MIT-licensed OpenCode foundation) distinguished by support for 500+ models with zero-markup BYOK pricing, an MCP marketplace, and cross-surface continuity where a task can move between Slack, VS Code/JetBrains, cloud, and terminal.
MIT-licensed open agent harness from HKU's Data Intelligence Lab (agent loop, tool registry, permission system, hooks, skills, plugins, MCP, React TUI, automatic context compression) built for clarity and Claude-style workflow compatibility, shipping with 'Ohmo', a built-in personal agent that runs on existing Claude Code/Codex subscriptions and works via Feishu/Slack/Telegram/Discord, autonomously branching, coding, testing, and opening PRs.
Mistral's minimal Apache-2.0 CLI coding agent (launched December 2025 alongside the open-weight Devstral 2 models, which score a vendor-reported 72.2% on SWE-bench Verified), distinguished by a deliberately lean self-hostable design — file read/write/patch, stateful shell, grep, and todo tools — with fully open, locally runnable model weights.
Moonshot AI's MIT-licensed TypeScript terminal agent (launched June 2026, replacing its earlier CLI) built around the token-efficient Kimi K2.7-Code 1T-parameter MoE model with 256K context, distinguished by built-in coder/explore/plan subagents running in isolated contexts and configurable OpenAI-compatible providers including local deployments.