mini-swe-agent 2.0.0a2

Nano SWE Agent - A simple AI software engineering agent

The minimal AI software engineering agent

📣 New tutorial on building minimal AI agents
📣 Gemini 3 Pro reaches 74% on SWE-bench verified with mini-swe-agent!
📣 New blogpost: Randomly switching between GPT-5 and Sonnet 4 boosts performance

[!WARNING] This is mini-swe-agent v2. Read the migration guide. For the previous version, check out the v1 branch.

In 2024, we built SWE-bench & SWE-agent and helped kickstart the coding agent revolution.

We now ask: What if our agent was 100x smaller, and still worked nearly as well?

The mini agent is for

• Researchers who want to benchmark, fine-tune or RL without assumptions, bloat, or surprises
• Developers who like to own, understand, and modify their tools
• Engineers who want something trivial to sandbox & to deploy anywhere

Here's some details:

• Minimal: Just some 100 lines of python for the agent class (and a bit more for the environment, model, and run script) — no fancy dependencies!
• Performant: Scores >74% on the SWE-bench verified benchmark benchmark; starts much faster than Claude Code
• Deployable: In addition to local envs, you can use docker, podman, singularity, apptainer, and more
• Built by the Princeton & Stanford team behind SWE-bench, SWE-agent, and more (see below)
• Widely adopted: In use by Meta, NVIDIA, Essential AI, Anyscale, and others
• Tested:

More motivation (for research)

SWE-agent jump-started the development of AI agents in 2024. Back then, we placed a lot of emphasis on tools and special interfaces for the agent. However, one year later, as LMs have become more capable, a lot of this is not needed at all to build a useful agent! In fact, the mini agent

• Does not have any tools other than bash — it doesn't even need to use the tool-calling interface of the LMs. This means that you can run it with literally any model. When running in sandboxed environments you also don't need to take care of installing a single package — all it needs is bash.
• Has a completely linear history — every step of the agent just appends to the messages and that's it. So there's no difference between the trajectory and the messages that you pass on to the LM. Great for debugging & fine-tuning.
• Executes actions with subprocess.run — every action is completely independent (as opposed to keeping a stateful shell session running). This makes it trivial to execute the actions in sandboxes (literally just switch out subprocess.run with docker exec) and to scale up effortlessly. Seriously, this is a big deal, trust me.

This makes it perfect as a baseline system and for a system that puts the language model (rather than the agent scaffold) in the middle of our attention. You can see the result on the SWE-bench (bash only) leaderboard, that evaluates the performance of different LMs with mini.

More motivation (as a tool)

Some agents are overfitted research artifacts. Others are UI-heavy frontend monsters.

The mini agent wants to be a hackable tool, not a black box.

• Simple enough to understand at a glance
• Convenient enough to use in daily workflows
• Flexible to extend

Unlike other agents (including our own swe-agent), it is radically simpler, because it:

• Does not have any tools other than bash — it doesn't even need to use the tool-calling interface of the LMs. Instead of implementing custom tools for every specific thing the agent might want to do, the focus is fully on the LM utilizing the shell to its full potential. Want it to do something specific like opening a PR? Just tell the LM to figure it out rather than spending time to implement it in the agent.
• Executes actions with subprocess.run — every action is completely independent (as opposed to keeping a stateful shell session running). This is a big deal for the stability of the agent, trust me.
• Has a completely linear history — every step of the agent just appends to the messages that are passed to the LM in the next step and that's it. This is great for debugging and understanding what the LM is prompted with.

Should I use SWE-agent or mini-SWE-agent?

You should use mini-swe-agent if

• You want a quick command line tool that works locally
• You want an agent with a very simple control flow
• You want even faster, simpler & more stable sandboxing & benchmark evaluations
• You are doing FT or RL and don't want to overfit to a specific agent scaffold

You should use swe-agent if

• You need specific tools or want to experiment with different tools
• You want to experiment with different history processors
• You want very powerful yaml configuration without touching code

What you get with both

• Excellent performance on SWE-Bench
• A trajectory browser

CLI (mini)	Batch inference
Trajectory browser	Python bindings
	agent = DefaultAgent( LitellmModel(model_name=...), LocalEnvironment(), ) agent.run("Write a sudoku game")

Let's get started!

Option 1: If you just want to try out the CLI (package installed in anonymous virtual environment)

pip install uv && uvx mini-swe-agent
# or
pip install pipx && pipx ensurepath && pipx run mini-swe-agent

Option 2: Install CLI & python bindings in current environment

pip install mini-swe-agent
mini  # run the CLI

Option 3: Install from source (developer setup)

git clone https://github.com/SWE-agent/mini-swe-agent.git
cd mini-swe-agent && pip install -e .
mini  # run the CLI

Read more in our documentation:

• Quick start guide
• Using the mini CLI
• Global configuration
• Yaml configuration files
• Power up with the cookbook
• FAQ
• Contribute!

Attribution

If you found this work helpful, please consider citing the SWE-agent paper in your work:

@inproceedings{yang2024sweagent,
  title={{SWE}-agent: Agent-Computer Interfaces Enable Automated Software Engineering},
  author={John Yang and Carlos E Jimenez and Alexander Wettig and Kilian Lieret and Shunyu Yao and Karthik R Narasimhan and Ofir Press},
  booktitle={The Thirty-eighth Annual Conference on Neural Information Processing Systems},
  year={2024},
  url={https://arxiv.org/abs/2405.15793}
}

Our other projects: