claude-code
Claude Code
Concept of the skill
What it is: Claude Code is Anthropic's terminal-first agent harness — a CLI and runtime that drives a frontier Claude model (Opus 4.8 as of mid-2026) through a real codebase with a native extensibility stack: skills, hooks, subagents, MCP, plan mode, background tasks, and slash commands.
Mental model: The harness is the body; the model is the brain. The model decides what to do; the harness decides what the model is allowed to do and how its actions are gated, rendered, parallelized, and persisted. Choosing Claude Code is choosing that body — its permission model, its extensibility layers, and its context budget — not just the underlying model.
Why it exists: A frontier model alone cannot safely operate a codebase. The harness supplies the missing scaffolding — typed tool surfaces the host can gate, lifecycle hooks for automation and security, isolated subagent context windows, on-demand skill loading, and a plan-before-act mode — so a long-horizon coding task can run autonomously without losing control or context.
What it is NOT: It is not the Anthropic API or SDK (that is application code you write), not the Claude model itself (the model is swappable inside the harness), and not a generic "agent framework" you assemble — it is one specific, opinionated harness with a fixed protocol.
Adjacent concepts: the Codex CLI (the GPT-running rival harness), OpenCode (the provider-agnostic open-source harness), the Claude API (the SDK surface for building your own harness), and generic autonomous-loop patterns (the topology underneath any harness).
One-line analogy: Picking a harness is like picking the cockpit, not the pilot — the same pilot flies differently depending on which instruments, autopilot, and safety interlocks the cockpit gives them.
Common misconception: That "Claude Code" and "Claude" are the same choice. They are two orthogonal decisions: which harness (Claude Code vs Codex vs OpenCode) and which model runs inside it. Conflating them leads to picking a harness for a model strength it does not own, or vice versa.