Claude Code Mini — Development skill for Claude Code

claude-code-mini

An async Python implementation of the Claude Code agent harness. ~1,890 lines, 14 commits, every subsystem readable in one sitting.

[](https://www.python.org/downloads/) [](#license) [](#tests--benchmarks)

Anthropic's leaked source revealed that **~98.4% of Claude Code is harness**, ~1.6% is model interaction. `claude-code-mini` is the smallest faithful reproduction of that ratio: agent loop, real filesystem tools, prompt/semantic/exact caching, multi-stage context compaction, allow/ask/deny permissions, Pre/PostToolUse hooks, slash commands, and subprocess subagents — all async, all in `src/claude_code_mini/`.

You can run it as a daily-driver REPL on your laptop. You can also `git log` your way through 14 commits and watch the architecture get built one feature at a time.

uv sync
cp .env.example .env  # add an API key, or skip if using Ollama
uv run ccm --tools real --yolo

claude-code-mini (provider=openai, model=gpt-4o-mini, tools=real)
[1] > what's the biggest python file under src and why?
The biggest file is src/claude_code_mini/harness.py at 244 lines; it owns
the 7-step request cascade (cache → context → LLM → permission → hook →
tool → format → cache writeback) plus the microcompact integration.
[2] > /cost
calls=4  in=8316  out=184  cached_read=1024  cost=$0.00136
[3] > /exit

---

Why this exists

Walking an interviewer through your own ~1.9 KLOC reproduction of the Claude Code architecture is a level of credibility no leetcode loop produces. Three audiences:

• AI/ML infra engineers who want a working reference for prompt caching, context compaction, permission engines, and hook protocols — without reading 512K LOC of TypeScript.
• Learners who want to read agent-harness internals end-to-end. Each of