ironharness

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harness — «упряжь»: we harness LLM agents to hardware.

An agent harness for I/O and firmware. Two modules:

• io-core — a safe I/O layer for agents: transports (serial, Modbus TCP, MQTT, file sandbox), a Modbus simulator, ESP32 flashing tools (esptool: offline image inspection, flash/erase on a live board), a JSONL journal of every operation, a replayer, limits (rate limit, deadlines), effect verification (expect_read), and an MCP server (19 tools).
• ironbench — a benchmark for firmware agents: golden tasks in simulators (Wokwi ESP32/MicroPython, plus Renode), an agent loop over any LLM API, pass@k reports.

Quick start

uvx ironharness-mcp                  # run the MCP server (no install)

From source:

uv sync                              # dependencies (+ the project itself, editable)
uv sync --extra flash                # + esptool (GPLv2+, kept out of the MIT core)
uv run pytest                        # tests (no hardware: loop:// and simulators)
uv run ruff check .                  # linter
uv run ironharness-mcp               # MCP server (stdio; or: python -m io_core.mcp_server)

Agent tools (MCP)

echo · serial_open/write/read/read_line · modbus_open/read/write · mqtt_open/publish/subscribe/read · esp_image_info/flash/erase · file_write/read/list/delete

Every operation is journaled to JSONL ($IRONHARNESS_HOME/journal.jsonl, default ~/.ironharness/); file operations are confined by the sandbox ($IRONHARNESS_SANDBOX, default ~/.ironharness/sandbox).

Connecting an external agent

Any MCP-compatible agent (Claude Code, Codex, Cursor, OpenCode…) gets all io-core tools with one config entry — the agent brings its own loop, ironharness provides the hands: transports, sandbox, journal, verification.

{
  "mcpServers": {
    "ironharness": {
      "command": "uvx",
      "args": ["ironharness-mcp"]
    }
  }
}

For unreliable-line testing there is io_core.faults.FaultyTransport — scripted failures (disconnect, delay, bit corruption, byte loss) over any transport — and io_core.mqtt_sim.MqttSimBroker, a minimal MQTT broker for offline runs.

ironbench — a benchmark for firmware agents

uv run ironbench list                              # catalog of golden tasks
uv run ironbench run --all                         # reference runs (needs WOKWI_CLI_TOKEN)
uv run ironbench solve --task blink --attempts 3   # an LLM agent solves a task
uv run ironbench report                            # pass@k: report.json + report.html

Tasks run on ESP32/MicroPython in Wokwi (headless wokwi-cli), Renode, the MicroPython unix port (free local runs), and a plant target (a closed-loop «object + controller» simulation scored on step-response metrics: p-regulator, pid-antiwindup, system-id). Every task has a class (io/data/protocol/fsm/control/ resilience) and a level 1–5; ironbench report shows a model's profile across classes, not a single number. LLM config — environment variables: LLM_BASE_URL (default: local LM Studio), LLM_MODEL, LLM_API_KEY, LLM_TIMEOUT.

Safety / intended use

• This is a bench tool for developing and testing agents, not production middleware. It is designed to be run locally against simulators and your own dev hardware.
• MQTT transport is plaintext TCP — no TLS, no authentication. Do not point it at production brokers or untrusted networks.
• esp_flash/esp_erase modify real hardware and are gated behind IRONHARNESS_ALLOW_REAL_FLASH=1 (opt-in). erasing flash is irreversible (ESP32 recovers by reflashing, but data is gone). esptool is an optional dependency: pip install 'ironharness[flash]'.
• Transports are not restricted to specific hosts/ports by design — the operator (you) decides what the agent may reach; every operation is journaled for audit.

Status

MVP under active development. Example benchmark results live in reports/ — recorded runs (JSON + HTML, open in a browser).