Show HN: A tiny shell agent in Rust

A tiny shell agent in Rust. Talks to any OpenAI-compatible API, runs commands with your approval, and stays out of the way.

cargo install --path .
export OPENAI_API_KEY=sk-...

nano-agent "what's in this repo?"

That's it. Run nano-agent

with no arguments for an interactive REPL.

nano-agent "fix the failing test"   # one-shot prompt
nano-agent                          # REPL
nano-agent -c                       # continue last session here
nano-agent -s                       # pick a recent session

Every command the agent wants to run is shown first:

$ cargo test
Approve? [y] Approve  [a] Approve All  [n] Deny:

In the REPL: :q

quits, :reset

starts over, end a line with \

for multiline.

Point it anywhere with an OpenAI-compatible API:

export OPENAI_BASE_URL=http://localhost:11434/v1   # e.g. Ollama
export OPENAI_MODEL=gemma4

Or keep providers in ~/.config/nano/config.json

(or ./nano_config.json

):

{
  "provider": "local",
  "custom_providers": {
    "local": {
      "provider_type": "openai",
      "base_url": "http://localhost:11434/v1",
      "api_key": "",
      "model": "gemma4"
    }
  }
}

See example_config.json for the full format.

MCP tools— add servers undermcp_servers

in the config; their tools are exposed to the model automatically.Planning mode— prefix a message with/mito

to talk to a separate local planning agent that prepares a detailed handoff before the main model acts (enablemito-mode

in the config).ACP— build with--features acp

to run nano as an ACP stdio agent (nano-agent --acp

) or to delegate subtasks to child agents configured underacp_agents

. A child'sworking_directory

is its sandbox boundary; without one, its tools are disabled.

Useful environment variables: OPENAI_API_KEY

, OPENAI_BASE_URL

, OPENAI_MODEL

, NANO_MAX_STEPS

, NANO_SANDBOX=0

(disable bwrap sandboxing).

cargo test
cargo test --features acp