Adopt
Claude Code is Anthropic's agentic coding tool - and currently the most complete harness ecosystem. It runs as terminal CLI, IDE extension (VS Code/JetBrains), desktop app and on the web, with CI integrations for GitHub Actions and GitLab.
Key Features
- Layered extension system: subagents with isolated context windows, deterministic hooks on lifecycle events (usable as programmable security policy), reusable skills, plugins and MCP client support.
- Versioned project memory via CLAUDE.md files - project knowledge lives in the repository, not in the tool.
- Headless mode (
claude -p) as first-class citizen for CI and automation (PR review, issue triage, scheduled jobs). - Application-layer permission model: allow/ask/deny rules per tool, optional OS sandbox.
- The engine is available as Claude Agent SDK for building custom agents.
Assessment
Proprietary; usage requires a Claude subscription or API pay-per-token.
Related: OpenAI Codex, OpenCode, Harness Engineering