$ find your agent harness

Anthropic's terminal-native agentic coding tool and the category-defining harness, distinguished by its layered extensibility model (CLAUDE.md memory, Agent Skills, subagents, hooks, plugins, MCP) plus permission modes, checkpoints, and optional sandboxing, available from CLI/IDE/desktop/web with an Agent SDK for building on top.

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.

The veteran model-agnostic IDE extension (VS Code + JetBrains, strong local-model support) that pivoted to 'Continuous AI' — a cn CLI running markdown-defined async agents as GitHub PR status checks — before being acquired by Cursor in 2026, with the original team shipping a final v2.0.0 (telemetry and auth removed).

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.

GitHub's terminal agent (GA February 2026) that brings the Copilot coding agent to the CLI, distinguished by deep GitHub.com integration (built-in GitHub MCP server, in-terminal Issues/PRs/Gists tabs), an Autopilot autonomous mode, custom .agent.md agents, multi-vendor model choice, and AI-credit-based billing.

Anthropic's production agent library exposing the same harness that powers Claude Code (tool loop, file/bash/web tools, subagents, hooks, skills, MCP, permission checkpoints) in Python and TypeScript; the MIT-licensed SDK wraps the bundled Claude Code runtime and, as of 2026, underpins Anthropic Managed Agents with separate metered billing from June 15, 2026.

Augment Code's terminal agent distinguished by its real-time Context Engine (semantic indexing of 1M+ files across repos, dependencies, docs, and git history), Unix-pipe-friendly print/quiet headless modes for CI/Lambda, custom slash commands, and credit-based plans from $20 (Indie) to enterprise.

Cursor's terminal/headless version of its IDE agent (shipped January 2026), distinguished by cloud handoff to isolated cloud VMs, sandboxed command execution with granular network/filesystem controls, hooks, async subagents, and shared MCP/rules/skills config with the Cursor editor.

Factory AI's agent-native development platform whose Droid CLI held top Terminal-Bench rankings (77.3% with GPT-5.3-Codex, Feb 2026), distinguished by deploying agents across CLI, IDEs, Slack, and Linear with broad multi-vendor model support including Chinese open-weight models; raised $150M at $1.5B in April 2026.

xAI's terminal coding agent (beta, launched June 5, 2026) distinguished by 8 parallel worktree-isolated subagents, a plan-first approval workflow, Arena Mode for competing outputs, an ACP-to-MCP bridge for MCP servers, OpenCode integration, and aggressive pricing via SuperGrok ($30/mo) and X Premium+ subscriptions.

GitHub's fully autonomous background worker: assign it a GitHub Issue and it works in a GitHub Actions-powered sandbox and delivers a draft PR, with MCP server support, custom .agent.md agents, agentic code review that hands fixes back to the agent, and (since Feb 2026) the ability to assign the same issue to Claude, Codex and Copilot simultaneously and pick the best PR; available on Pro through Enterprise with AI-credit billing from June 2026.

Launched GA June 30 2026, these are pipeline-native reasoning agents for the software-delivery stage (between code and production) rather than code authoring: every pipeline step can run as an agent governed by existing enterprise deployment controls, with an LLM Gateway enforcing policy on prompts, distinct auditable AI identities, per-agent/per-pipeline model switching, and a marketplace of Harness-managed and community agents.