Name	Name	Last commit message	Last commit date
parent directory ..
docs	docs
README.md	README.md
agent.py	agent.py
config.py	config.py
context.py	context.py
demo.py	demo.py
make_demo.py	make_demo.py
nano_claude.py	nano_claude.py
providers.py	providers.py
requirements.txt	requirements.txt
tools.py	tools.py

Nano Claude Code: A Minimal Python Reimplementation

The newest source of Claude Code · Issue

🔥🔥🔥 News (Pacific Time)

01:47 PM, Apr 01, 2026: Support VLLM inference (~2000 lines of Python Code)
11:30 AM, Apr 01, 2026: Support more closed-source models and open-source models: Claude, GPT, Gemini, Kimi, Qwen, Zhipu, DeepSeek, and local open-source models via Ollama or any OpenAI-compatible endpoint. (~1700 lines of Python Code)
09:50 AM, Apr 01, 2026: Support more closed-source models: Claude, GPT, Gemini. (~1300 lines of Python Code)
08:23 AM, Apr 01, 2026: Release the initial version of Nano Claude Code (~900 lines of Python Code)

Nano Claude Code

A minimal Python implementation of Claude Code in ~900 lines (Initial version), supporting Claude, GPT, Gemini, Kimi, Qwen, Zhipu, DeepSeek, and local open-source models via Ollama or any OpenAI-compatible endpoint.

Content

Features
Supported Models
- Closed-Source (API)
- Open-Source (Local via Ollama)
Installation
Usage: Closed-Source API Models
Usage: Open-Source Models (Local)
Model Name Format
CLI Reference
Slash Commands (REPL)
Configuring API Keys
Permission System
Built-in Tools
CLAUDE.md Support
Session Management
Project Structure
FAQ

Features

Feature	Details
Multi-provider	Anthropic · OpenAI · Gemini · Kimi · Qwen · Zhipu · DeepSeek · Ollama · LM Studio · Custom endpoint
Interactive REPL	readline history, Tab-complete slash commands
Agent loop	Streaming API + automatic tool-use loop
8 built-in tools	Read · Write · Edit · Bash · Glob · Grep · WebFetch · WebSearch
Permission system	`auto` / `accept-all` / `manual` modes
14 slash commands	`/model` · `/config` · `/save` · `/cost` · …
Context injection	Auto-loads `CLAUDE.md`, git status, cwd
Session persistence	Save / load conversations to `~/.nano_claude/sessions/`
Extended Thinking	Toggle on/off (Claude models only)
Cost tracking	Token usage + estimated USD cost
Non-interactive mode	`--print` flag for scripting / CI

Supported Models

Closed-Source (API)

Provider	Model	Context	Strengths	API Key Env
Anthropic	`claude-opus-4-6`	200k	Most capable, best for complex reasoning	`ANTHROPIC_API_KEY`
Anthropic	`claude-sonnet-4-6`	200k	Balanced speed & quality	`ANTHROPIC_API_KEY`
Anthropic	`claude-haiku-4-5-20251001`	200k	Fast, cost-efficient	`ANTHROPIC_API_KEY`
OpenAI	`gpt-4o`	128k	Strong multimodal & coding	`OPENAI_API_KEY`
OpenAI	`gpt-4o-mini`	128k	Fast, cheap	`OPENAI_API_KEY`
OpenAI	`o3-mini`	200k	Strong reasoning	`OPENAI_API_KEY`
OpenAI	`o1`	200k	Advanced reasoning	`OPENAI_API_KEY`
Google	`gemini-2.5-pro-preview-03-25`	1M	Long context, multimodal	`GEMINI_API_KEY`
Google	`gemini-2.0-flash`	1M	Fast, large context	`GEMINI_API_KEY`
Google	`gemini-1.5-pro`	2M	Largest context window	`GEMINI_API_KEY`
Moonshot (Kimi)	`moonshot-v1-8k`	8k	Chinese & English	`MOONSHOT_API_KEY`
Moonshot (Kimi)	`moonshot-v1-32k`	32k	Chinese & English	`MOONSHOT_API_KEY`
Moonshot (Kimi)	`moonshot-v1-128k`	128k	Long context	`MOONSHOT_API_KEY`
Alibaba (Qwen)	`qwen-max`	32k	Best Qwen quality	`DASHSCOPE_API_KEY`
Alibaba (Qwen)	`qwen-plus`	128k	Balanced	`DASHSCOPE_API_KEY`
Alibaba (Qwen)	`qwen-turbo`	1M	Fast, cheap	`DASHSCOPE_API_KEY`
Alibaba (Qwen)	`qwq-32b`	32k	Strong reasoning	`DASHSCOPE_API_KEY`
Zhipu (GLM)	`glm-4-plus`	128k	Best GLM quality	`ZHIPU_API_KEY`
Zhipu (GLM)	`glm-4`	128k	General purpose	`ZHIPU_API_KEY`
Zhipu (GLM)	`glm-4-flash`	128k	Free tier available	`ZHIPU_API_KEY`
DeepSeek	`deepseek-chat`	64k	Strong coding	`DEEPSEEK_API_KEY`
DeepSeek	`deepseek-reasoner`	64k	Chain-of-thought reasoning	`DEEPSEEK_API_KEY`

Open-Source (Local via Ollama)

Model	Size	Strengths	Pull Command
`llama3.3`	70B	General purpose, strong reasoning	`ollama pull llama3.3`
`llama3.2`	3B / 11B	Lightweight	`ollama pull llama3.2`
`qwen2.5-coder`	7B / 32B	Best for coding tasks	`ollama pull qwen2.5-coder`
`qwen2.5`	7B / 72B	Chinese & English	`ollama pull qwen2.5`
`deepseek-r1`	7B–70B	Reasoning, math	`ollama pull deepseek-r1`
`deepseek-coder-v2`	16B	Coding	`ollama pull deepseek-coder-v2`
`mistral`	7B	Fast, efficient	`ollama pull mistral`
`mixtral`	8x7B	Strong MoE model	`ollama pull mixtral`
`phi4`	14B	Microsoft, strong reasoning	`ollama pull phi4`
`gemma3`	4B / 12B / 27B	Google open model	`ollama pull gemma3`
`codellama`	7B / 34B	Code generation	`ollama pull codellama`

Note: Tool calling requires a model that supports function calling. Recommended local models: qwen2.5-coder, llama3.3, mistral, phi4.

Installation

git clone <repo-url>
cd nano_claude_code

pip install -r requirements.txt
# or manually:
pip install anthropic openai httpx rich

Usage: Closed-Source API Models

Anthropic Claude

Get your API key at console.anthropic.com.

export ANTHROPIC_API_KEY=sk-ant-api03-...

# Default model (claude-opus-4-6)
python nano_claude.py

# Choose a specific model
python nano_claude.py --model claude-sonnet-4-6
python nano_claude.py --model claude-haiku-4-5-20251001

# Enable Extended Thinking
python nano_claude.py --model claude-opus-4-6 --thinking --verbose

OpenAI GPT

Get your API key at platform.openai.com.

export OPENAI_API_KEY=sk-...

python nano_claude.py --model gpt-4o
python nano_claude.py --model gpt-4o-mini
python nano_claude.py --model o3-mini

Google Gemini

Get your API key at aistudio.google.com.

export GEMINI_API_KEY=AIza...

python nano_claude.py --model gemini/gemini-2.0-flash
python nano_claude.py --model gemini/gemini-1.5-pro
python nano_claude.py --model gemini/gemini-2.5-pro-preview-03-25

Kimi (Moonshot AI)

Get your API key at platform.moonshot.cn.

export MOONSHOT_API_KEY=sk-...

python nano_claude.py --model kimi/moonshot-v1-32k
python nano_claude.py --model kimi/moonshot-v1-128k

Qwen (Alibaba DashScope)

Get your API key at dashscope.aliyun.com.

export DASHSCOPE_API_KEY=sk-...

python nano_claude.py --model qwen/qwen-max
python nano_claude.py --model qwen/qwq-32b
python nano_claude.py --model qwen/qwen2.5-coder-32b-instruct

Zhipu GLM

Get your API key at open.bigmodel.cn.

export ZHIPU_API_KEY=...

python nano_claude.py --model zhipu/glm-4-plus
python nano_claude.py --model zhipu/glm-4-flash   # free tier

DeepSeek

Get your API key at platform.deepseek.com.

export DEEPSEEK_API_KEY=sk-...

python nano_claude.py --model deepseek/deepseek-chat
python nano_claude.py --model deepseek/deepseek-reasoner

Usage: Open-Source Models (Local)

Option A — Ollama (Recommended)

Ollama runs models locally with zero configuration. No API key required.

Step 1: Install Ollama

# macOS / Linux
curl -fsSL https://ollama.com/install.sh | sh

# Or download from https://ollama.com/download

Step 2: Pull a model

# Best for coding (recommended)
ollama pull qwen2.5-coder          # 4.7 GB (7B)
ollama pull qwen2.5-coder:32b      # 19 GB (32B)

# General purpose
ollama pull llama3.3               # 42 GB (70B)
ollama pull llama3.2               # 2.0 GB (3B)

# Reasoning
ollama pull deepseek-r1            # 4.7 GB (7B)
ollama pull deepseek-r1:32b        # 19 GB (32B)

# Other
ollama pull phi4                   # 9.1 GB (14B)
ollama pull mistral                # 4.1 GB (7B)

Step 3: Start Ollama server (runs automatically on macOS; on Linux run manually)

ollama serve     # starts on http://localhost:11434

Step 4: Run nano claude

python nano_claude.py --model ollama/qwen2.5-coder
python nano_claude.py --model ollama/llama3.3
python nano_claude.py --model ollama/deepseek-r1

List your locally available models:

ollama list

Then use any model from the list:

python nano_claude.py --model ollama/<model-name>

Option B — LM Studio

LM Studio provides a GUI to download and run models, with a built-in OpenAI-compatible server.

Step 1: Download LM Studio and install it.

Step 2: Search and download a model inside LM Studio (GGUF format).

Step 3: Go to Local Server tab → click Start Server (default port: 1234).

Step 4:

python nano_claude.py --model lmstudio/<model-name>
# e.g.:
python nano_claude.py --model lmstudio/phi-4-GGUF
python nano_claude.py --model lmstudio/qwen2.5-coder-7b

The model name should match what LM Studio shows in the server status bar.

Option C — vLLM / Self-Hosted OpenAI-Compatible Server

For self-hosted inference servers (vLLM, TGI, llama.cpp server, etc.) that expose an OpenAI-compatible API:

Quick Start for option C: Step 1: Start vllm:

CUDA_VISIBLE_DEVICES=7 python -m vllm.entrypoints.openai.api_server \
     --model Qwen/Qwen2.5-Coder-7B-Instruct \
     --host 0.0.0.0 \
     --port 8000 \
     --enable-auto-tool-choice \
     --tool-call-parser hermes

Step 2: Start nano claude：

  export CUSTOM_BASE_URL=http://localhost:8000/v1
  export CUSTOM_API_KEY=none
  python nano_claude.py --model custom/Qwen/Qwen2.5-Coder-7B-Instruct

# Example: vLLM serving Qwen2.5-Coder-32B
python -m vllm.entrypoints.openai.api_server \
    --model Qwen/Qwen2.5-Coder-32B-Instruct \
    --port 8000

# Then run nano claude pointing to your server:
python nano_claude.py

Inside the REPL:

/config custom_base_url=http://localhost:8000/v1
/config custom_api_key=token-abc123    # skip if no auth
/model custom/Qwen2.5-Coder-32B-Instruct

Or set via environment:

export CUSTOM_BASE_URL=http://localhost:8000/v1
export CUSTOM_API_KEY=token-abc123

python nano_claude.py --model custom/Qwen2.5-Coder-32B-Instruct

For a remote GPU server:

/config custom_base_url=http://192.168.1.100:8000/v1
/model custom/your-model-name

Model Name Format

Three equivalent formats are supported:

# 1. Auto-detect by prefix (works for well-known models)
python nano_claude.py --model gpt-4o
python nano_claude.py --model gemini-2.0-flash
python nano_claude.py --model deepseek-chat

# 2. Explicit provider prefix with slash
python nano_claude.py --model ollama/qwen2.5-coder
python nano_claude.py --model kimi/moonshot-v1-128k

# 3. Explicit provider prefix with colon (also works)
python nano_claude.py --model kimi:moonshot-v1-32k
python nano_claude.py --model qwen:qwen-max

Auto-detection rules:

Model prefix	Detected provider
`claude-`	anthropic
`gpt-`, `o1`, `o3`	openai
`gemini-`	gemini
`moonshot-`, `kimi-`	kimi
`qwen`, `qwq-`	qwen
`glm-`	zhipu
`deepseek-`	deepseek
`llama`, `mistral`, `phi`, `gemma`, `mixtral`, `codellama`	ollama

CLI Reference

python nano_claude.py [OPTIONS] [PROMPT]

Options:
  -p, --print          Non-interactive: run prompt and exit
  -m, --model MODEL    Override model (e.g. gpt-4o, ollama/llama3.3)
  --accept-all         Auto-approve all operations (no permission prompts)
  --verbose            Show thinking blocks and per-turn token counts
  --thinking           Enable Extended Thinking (Claude only)
  --version            Print version and exit
  -h, --help           Show help

Examples:

# Interactive REPL with default model
python nano_claude.py

# Switch model at startup
python nano_claude.py --model gpt-4o
python nano_claude.py -m ollama/deepseek-r1:32b

# Non-interactive / scripting
python nano_claude.py --print "Write a Python fibonacci function"
python nano_claude.py -p "Explain the Rust borrow checker in 3 sentences" -m gemini/gemini-2.0-flash

# CI / automation (no permission prompts)
python nano_claude.py --accept-all --print "Initialize a Python project with pyproject.toml"

# Debug mode (see tokens + thinking)
python nano_claude.py --thinking --verbose

Slash Commands (REPL)

Type / and press Tab to autocomplete.

Command	Description
`/help`	Show all commands
`/clear`	Clear conversation history
`/model`	Show current model + list all available models
`/model <name>`	Switch model (takes effect immediately)
`/config`	Show all current config values
`/config key=value`	Set a config value (persisted to disk)
`/save`	Save session (auto-named by timestamp)
`/save <filename>`	Save session to named file
`/load`	List all saved sessions
`/load <filename>`	Load a saved session
`/history`	Print full conversation history
`/context`	Show message count and token estimate
`/cost`	Show token usage and estimated USD cost
`/verbose`	Toggle verbose mode (tokens + thinking)
`/thinking`	Toggle Extended Thinking (Claude only)
`/permissions`	Show current permission mode
`/permissions <mode>`	Set permission mode: `auto` / `accept-all` / `manual`
`/cwd`	Show current working directory
`/cwd <path>`	Change working directory
`/exit` / `/quit`	Exit

Switching models inside a session:

[myproject] ❯ /model
  Current model: claude-opus-4-6  (provider: anthropic)

  Available models by provider:
    anthropic     claude-opus-4-6, claude-sonnet-4-6, ...
    openai        gpt-4o, gpt-4o-mini, o3-mini, ...
    ollama        llama3.3, llama3.2, phi4, mistral, ...
    ...

[myproject] ❯ /model gpt-4o
  Model set to gpt-4o  (provider: openai)

[myproject] ❯ /model ollama/qwen2.5-coder
  Model set to ollama/qwen2.5-coder  (provider: ollama)

Configuring API Keys

Method 1: Environment Variables (recommended)

# Add to ~/.bashrc or ~/.zshrc
export ANTHROPIC_API_KEY=sk-ant-...
export OPENAI_API_KEY=sk-...
export GEMINI_API_KEY=AIza...
export MOONSHOT_API_KEY=sk-...       # Kimi
export DASHSCOPE_API_KEY=sk-...      # Qwen
export ZHIPU_API_KEY=...             # Zhipu GLM
export DEEPSEEK_API_KEY=sk-...       # DeepSeek

Method 2: Set Inside the REPL (persisted)

/config anthropic_api_key=sk-ant-...
/config openai_api_key=sk-...
/config gemini_api_key=AIza...
/config kimi_api_key=sk-...
/config qwen_api_key=sk-...
/config zhipu_api_key=...
/config deepseek_api_key=sk-...

Keys are saved to ~/.nano_claude/config.json and loaded automatically on next launch.

Method 3: Edit the Config File Directly

// ~/.nano_claude/config.json
{
  "model": "qwen/qwen-max",
  "max_tokens": 8192,
  "permission_mode": "auto",
  "verbose": false,
  "thinking": false,
  "qwen_api_key": "sk-...",
  "kimi_api_key": "sk-...",
  "deepseek_api_key": "sk-..."
}

Permission System

Mode	Behavior
`auto` (default)	Read-only operations always allowed. Prompts before Bash commands and file writes.
`accept-all`	Never prompts. All operations proceed automatically.
`manual`	Prompts before every single operation, including reads.

When prompted:

  Allow: Run: git commit -am "fix bug"  [y/N/a(ccept-all)]

y — approve this one action
n or Enter — deny
a — approve and switch to accept-all for the rest of the session

Commands always auto-approved in auto mode: ls, cat, head, tail, wc, pwd, echo, git status, git log, git diff, git show, find, grep, rg, python, node, pip show, npm list, and other read-only shell commands.

Built-in Tools

Tool	Description	Key Parameters
`Read`	Read file with line numbers	`file_path`, `limit`, `offset`
`Write`	Create or overwrite file	`file_path`, `content`
`Edit`	Exact string replacement in file	`file_path`, `old_string`, `new_string`, `replace_all`
`Bash`	Execute shell command	`command`, `timeout` (default 30s)
`Glob`	Find files by glob pattern	`pattern` (e.g. `*/.py`), `path`
`Grep`	Regex search in files (uses ripgrep if available)	`pattern`, `path`, `glob`, `output_mode`
`WebFetch`	Fetch and extract text from URL	`url`, `prompt`
`WebSearch`	Search the web via DuckDuckGo	`query`

CLAUDE.md Support

Place a CLAUDE.md file in your project to give the model persistent context about your codebase. Nano Claude automatically finds and injects it into the system prompt.

~/.claude/CLAUDE.md          # Global — applies to all projects
/your/project/CLAUDE.md      # Project-level — found by walking up from cwd

Example CLAUDE.md:

# Project: FastAPI Backend

## Stack
- Python 3.12, FastAPI, PostgreSQL, SQLAlchemy 2.0, Alembic
- Tests: pytest, coverage target 90%

## Conventions
- Format with black, lint with ruff
- Full type annotations required
- New endpoints must have corresponding tests

## Important Notes
- Never hard-code credentials — use environment variables
- Do not modify existing Alembic migration files
- The `staging` branch deploys automatically to staging on push

Session Management

# Inside REPL:
/save                          # auto-name: session_20260401_143022.json
/save debug_auth_bug           # named save

/load                          # list all saved sessions
/load debug_auth_bug           # resume a session
/load session_20260401_143022.json

Sessions are stored as JSON in ~/.nano_claude/sessions/.

Project Structure

nano_claude_code/
├── nano_claude.py   # Entry point: REPL + slash commands + output rendering  (~580 lines)
├── agent.py         # Agent loop: neutral message format + tool dispatch      (~160 lines)
├── providers.py     # Multi-provider: adapters + message format conversion    (~480 lines)
├── tools.py         # 8 tool implementations + JSON schemas                  (~360 lines)
├── context.py       # System prompt builder: CLAUDE.md + git + cwd           (~100 lines)
├── config.py        # Config load/save/defaults                               (~70 lines)
├── demo.py          # Demo script (requires API key)
├── make_demo.py     # Generates demo.gif and screenshot.png
├── demo.gif         # Animated demo
├── screenshot.png   # Static screenshot
└── requirements.txt

FAQ

Q: Tool calls don't work with my local Ollama model.

Not all models support function calling. Use one of the recommended tool-calling models: qwen2.5-coder, llama3.3, mistral, or phi4.

ollama pull qwen2.5-coder
python nano_claude.py --model ollama/qwen2.5-coder

Q: How do I connect to a remote GPU server running vLLM?

/config custom_base_url=http://your-server-ip:8000/v1
/config custom_api_key=your-token
/model custom/your-model-name

Q: How do I check my API cost?

/cost

  Input tokens:  3,421
  Output tokens:   892
  Est. cost:     $0.0648 USD

Q: Can I use multiple API keys in the same session?

Yes. Set all the keys you need upfront (via env vars or /config). Then switch models freely — each call uses the key for the active provider.

Q: How do I make a model available across all projects?

Add keys to ~/.bashrc or ~/.zshrc. Set the default model in ~/.nano_claude/config.json:

{ "model": "claude-sonnet-4-6" }

Q: Qwen / Zhipu returns garbled text.

Ensure your DASHSCOPE_API_KEY / ZHIPU_API_KEY is correct and the account has sufficient quota. Both providers use UTF-8 and handle Chinese well.

Q: Can I pipe input to nano claude?

echo "Explain this file" | python nano_claude.py --print --accept-all
cat error.log | python nano_claude.py -p "What is causing this error?"

Q: How do I run it as a CLI tool from anywhere?

# Add an alias to ~/.bashrc or ~/.zshrc
alias nc='python /path/to/nano_claude_code/nano_claude.py'

# Or install as a script
pip install -e .   # if setup.py exists

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README.md

Nano Claude Code: A Minimal Python Reimplementation

🔥🔥🔥 News (Pacific Time)

Nano Claude Code

Content

Features

Supported Models

Closed-Source (API)

Open-Source (Local via Ollama)

Installation

Usage: Closed-Source API Models

Anthropic Claude

OpenAI GPT

Google Gemini

Kimi (Moonshot AI)

Qwen (Alibaba DashScope)

Zhipu GLM

DeepSeek

Usage: Open-Source Models (Local)

Option A — Ollama (Recommended)

Option B — LM Studio

Option C — vLLM / Self-Hosted OpenAI-Compatible Server

Model Name Format

CLI Reference

Slash Commands (REPL)

Configuring API Keys

Method 1: Environment Variables (recommended)

Method 2: Set Inside the REPL (persisted)

Method 3: Edit the Config File Directly

Permission System

Built-in Tools

CLAUDE.md Support

Session Management

Project Structure

FAQ

FilesExpand file tree

nano-claude-code

Directory actions

More options

Directory actions

More options

Latest commit

History

nano-claude-code

Folders and files

parent directory

README.md

Nano Claude Code: A Minimal Python Reimplementation

🔥🔥🔥 News (Pacific Time)

Nano Claude Code

Content

Features

Supported Models

Closed-Source (API)

Open-Source (Local via Ollama)

Installation

Usage: Closed-Source API Models

Anthropic Claude

OpenAI GPT

Google Gemini

Kimi (Moonshot AI)

Qwen (Alibaba DashScope)

Zhipu GLM

DeepSeek

Usage: Open-Source Models (Local)

Option A — Ollama (Recommended)

Option B — LM Studio

Option C — vLLM / Self-Hosted OpenAI-Compatible Server

Model Name Format

CLI Reference

Slash Commands (REPL)

Configuring API Keys

Method 1: Environment Variables (recommended)

Method 2: Set Inside the REPL (persisted)

Method 3: Edit the Config File Directly

Permission System

Built-in Tools

CLAUDE.md Support

Session Management

Project Structure

FAQ