iNAV MCP Server

CI License: MIT Python MCP PyPI

An MCP server that lets Claude configure, diagnose, and troubleshoot an iNAV flight controller over USB — built primarily for flying wings (elevon FPV wings like the TBS Chupito and Mojito), and also for conventional fixed-wing planes.

It talks to the FC through a single serial connection, using the iNAV CLI for configuration writes and a small built-in MSP codec for live/binary reads. Every write is dry-run by default, auto-backs-up first, refuses while the board is armed, and reads back to verify.

_{Recorded against a live iNAV 6.1.0 flight controller over USB.}

⚠️ Safety: Always remove props from the aircraft before any motor test. This tool never switches the FC into MSP-RX mode and never arms the aircraft.

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Requirements

• Python 3.10+
• An iNAV flight controller (developed against iNAV 8.x/9.x) connected over USB
• The serial port the FC enumerates as (e.g. COM3 on Windows, /dev/ttyACM0 on Linux)

Install

From PyPI (once the first release is published):

pip install inav-mcp

From source (for development, or to run the latest unreleased code):

# from the repo root
python -m venv .venv
.venv/Scripts/python -m pip install -e .          # Windows
# source .venv/bin/activate && pip install -e .    # Linux/macOS

For development (tests):

.venv/Scripts/python -m pip install -e ".[dev]"

Try it without a flight controller

You don't need any hardware to confirm the project works — the test suite runs fully offline (no FC required):

.venv/Scripts/python -m pytest        # Windows
# .venv/bin/pytest                     # Linux/macOS

All 186 tests should pass. To actually use the server, though, you need a flight controller flashed with iNAV firmware (developed against iNAV 8.x/9.x) connected over USB — without one, the connection tools have nothing to talk to.

Register with Claude

Add the server to your Claude (Code or Desktop) MCP config (~/.claude/settings.json or the Claude Desktop config). Replace the paths below with wherever you cloned this repo — the command points at the Python inside your .venv, and cwd is the repo root.

Windows:

{
  "mcpServers": {
    "inav": {
      "command": "C:\\path\\to\\inav-mcp\\.venv\\Scripts\\python.exe",
      "args": ["-m", "inav_mcp.server"],
      "cwd": "C:\\path\\to\\inav-mcp"
    }
  }
}

Linux / macOS:

{
  "mcpServers": {
    "inav": {
      "command": "/path/to/inav-mcp/.venv/bin/python",
      "args": ["-m", "inav_mcp.server"],
      "cwd": "/path/to/inav-mcp"
    }
  }
}

The server speaks MCP over stdio. You can also run it directly with the installed entry point inav-mcp.

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Typical workflows

The server ships prompts that walk Claude through the common jobs — just pick one:

• new_fixed_wing_setup — gather hardware details → define_aircraft → review → apply.
• troubleshoot_no_arm — decode arming-prevention flags → guided fixes.
• configure_modes — identify switches from live RC → suggest a layout → assign modes.

Or drive it conversationally, e.g.:

"Connect to my FC on COM3 and tell me why it won't arm."

"Set up a 4S flying wing on DSHOT600, then show me the commands before applying."

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Tools (35)

Connection & identity

Tool	What it does
list_serial_ports()	List available serial ports.
find_fc(baud=115200, probe_all=False)	Auto-detect which port has an FC by probing for MSP identity — no guessing the port.
connect(port, baud=115200)	Open the FC connection, return board identity.
disconnect()	Close the connection.
board_info()	FC variant, firmware version, target, API version, sensors.

Hardware setup

Tool	What it does
define_aircraft(name, wing_type, esc_protocol, cells, …)	Offline planner — stores a profile and generates the CLI config plan.
get_aircraft_profile()	The current declared profile + plan.
apply_aircraft_setup(confirm=False)	Apply the plan (gated: not armed, auto-backup, read-back verify). On iNAV, applying is inherently save+reboot.
check_config()	diff all + lint against the declared profile + ARM check.

Flight modes & switches

Tool	What it does
suggest_mode_layout(skill_level, num_switches, has_gps=False)	Recommend a fixed-wing switch/mode layout (offline).
set_flight_mode(mode_name, aux_channel, range_low, range_high, confirm=False)	Assign one mode to an aux range.
assign_switch(switch_channel, switch_positions, mode_per_position, confirm=False)	Map a whole 2/3/6-pos switch in one call.
clear_flight_mode(mode_name, confirm=False)	Remove a mode's switch assignments.

Diagnostics

Tool	What it does
diagnose()	Full sweep: arming, sensors, RC, battery, GPS → prioritized fixes.
why_wont_it_arm()	Decode arming-prevention flags into plain reasons + fixes.
read_rc_channels()	Live RC channel values — flip a switch, see which channel moves.
read_sensors()	Live attitude, per-sensor health, battery.
get_status()	MSP status + CLI status/tasks.
list_flight_modes()	All modes and their current switch assignments.
check_failsafe()	Read failsafe_* settings, explain the RC-loss procedure, flag risky setups (e.g. RTH without GPS).

Bench tests & calibration

Tool	What it does
test_motor(motor, throttle_us=1100, duration_s=2.0, props_removed=False, confirm=False)	Spin ONE motor briefly. Hard-gated: props_removed=True + confirm=True, refuses while armed, always auto-stops. (No test_servo — iNAV has no live servo override; verify surfaces with the TX sticks + read_rc_channels().)
calibrate_accelerometer(confirm=False)	Zero-level the accelerometer (board flat + still). Fixes most "not level" arming blocks.
calibrate_magnetometer(confirm=False)	Calibrate the compass (rotate the craft ~30s).

Navigation & tuning

Tool	What it does
read_gps()	Live GPS fix/sats/position + nav-readiness assessment (read-only).
configure_gps(provider="UBLOX", sbas=None, confirm=False)	Enable the GPS feature and set provider/SBAS.
set_nav(rth_altitude_m=None, rth_climb_first=None, rth_allow_landing=None, loiter_radius_m=None, confirm=False)	Set fixed-wing RTH altitude / climb-first / landing / loiter radius.
read_tuning()	Read fixed-wing PID gains, rates, and filter cutoffs.
set_pid(axis, p=None, i=None, d=None, ff=None, confirm=False)	Set fixed-wing P/I/D/FF gains for one axis.

Config management

Tool	What it does
backup_config(label=None)	Save diff all to a timestamped file under ./backups/.
list_backups()	List saved backups (path, time, size, label), newest first.
restore_config(path, confirm=False)	Replay a saved backup via CLI.
set_failsafe(procedure=None, throttle_us=None, confirm=False)	Set the RC-loss procedure / throttle (atomic write; FC validates the procedure token).
cli(command, confirm_for_writes=False, props_removed=False)	Raw CLI escape hatch (ONE command, one reboot). Writes need confirm_for_writes; a live motor test needs props_removed=True and is never saved.
cli_batch(commands, confirm_for_writes=False)	Run MANY CLI commands in one session → one reboot. Read-only batch exits without saving; a write batch backs up + saves once (rolls back if any command is rejected). Motor/save/exit commands refused.
save_and_reboot(confirm=False)	save to EEPROM and reboot (marks the connection stale).

Resources

• inav://modes-reference — iNAV mode glossary with fixed-wing relevance.
• inav://current-profile — the declared aircraft profile + generated plan.
• inav://last-backup — the most recent diff all backup.

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Safety model

1. Props-off gate — test_motor() and any live motor command via cli(...) require props_removed=True (the generic write-confirm cannot bypass it), refuse while the board is armed, and are never saved. test_motor() also clamps throttle/duration and always commands the motor back to stop.
2. Armed guard — all writes (and motor tests / calibrations) refuse if the FC reports armed.
3. Auto-backup before every write; the backup path is returned.
4. Dry-run by default — writes return the exact commands; confirm=True applies.
5. Read-back verify — after applying, settings are re-read and mismatches flagged.
6. save = reboot — save_and_reboot warns and marks the connection stale.
7. No receiver-mode changes — the FC is never switched to MSP-RX.

Reboot model — why batching matters

On iNAV, leaving the CLI always reboots the FC — both save (persist to EEPROM) and exit (discard changes) trigger a reboot, after which the USB VCP re-enumerates and we reconnect (~6–8 s, surfaced as reboot_seconds). So every CLI round-trip costs one reboot, including read-only ones (get, diff, dump, version). There is no way to read over the CLI without that reboot — the only lever is to do fewer CLI sessions.

What this server does to keep reboot churn down:

• Reads prefer MSP, which never reboots. get_status, read_rc_channels, read_sensors, read_gps, list_flight_modes, why_wont_it_arm, diagnose, and the armed-guard all read structured data over MSP — zero reboots. Only data that's CLI-only (diff all, get failsafe, PID/rate/filter gets) pays a reboot.
• Writes are atomic and batch internally. Each write tool (apply_aircraft_setup, set_flight_mode, assign_switch, set_pid, set_failsafe, restore_config, …) opens one CLI session: backup → apply all commands → save → reboot once. Multiple settings = one reboot.
• cli_batch() for ad-hoc runs. Instead of calling cli() in a loop (one reboot per command — the cadence that can knock a board into DFU), pass a list to cli_batch(): one session, one reboot. Read-only batches exit without saving; write batches back up and save once (rolling back if any command is rejected).
• Resilient reconnect. After a reboot the reconnect waits a short settle, then polls with backoff; if the original COM port doesn't return it scans for a re-enumerated one, and if the board came back in DFU/bootloader mode it says so and tells you to power-cycle (USB unplug/replug) rather than hanging.

How it works

• Single serial handle shared between MSP and CLI modes (connection.py), tracked by a mode state machine. Never two handles on one port.
• CLI-first writes — the CLI is stable across firmware versions; MSP command IDs can drift. A thin MSP v1/v2 codec (msp.py) handles only the live binary reads (status, RC, attitude, analog, GPS, sensor health, mode ranges, box maps).
• Box IDs are resolved at runtime via MSP_BOXNAMES + MSP_BOXIDS — never hardcoded.
• Arming flags are decoded from knowledge/arming_flags.json, calibrated to iNAV 8.x/9.x bit positions. The table declares its calibrated major versions, and connect() / board_info() / why_wont_it_arm() / diagnose() warn when the connected firmware is outside that range (bit positions shift between majors, so flag names may be mislabelled even though the raw flag value is correct).

Development

.venv/Scripts/python -m pytest          # 186 tests, all offline (no FC needed)

The suite covers the MSP codec round-trips, CLI response parsing, the diagnostic rule engine, offline profile/command generation, mode-range read-modify-write logic (against a mock connection), and resource/prompt registration.

Project layout:

inav_mcp/
  server.py          # FastMCP app: all tools, resources, prompts
  connection.py      # single serial handle, MSP + CLI mode switching
  msp.py             # MSP v1/v2 codec + parsers
  cli.py             # CLI response parsing, write-command detection
  modes.py           # box maps, mode-range read/write, layout planner
  profiles.py        # AircraftProfile + offline CLI command generator
  troubleshoot.py    # diagnose() rule engine + arming-flag decode
  safety.py          # armed guard, backup paths
  state.py           # connection + profile singletons
  knowledge/         # arming_flags / modes_reference / esc_protocols / fc_targets (JSON)
tests/               # offline pytest suite
tools/               # gen_readme_tools.py — regenerates the tool reference below
examples/            # flying_wing_quickstart.md — end-to-end walkthrough

Release history is in CHANGELOG.md.

Full tool reference

Complete, signature-accurate list — regenerate after changing tools with python -m tools.gen_readme_tools (a test fails if this drifts):

35 tools — auto-generated by tools/gen_readme_tools.py; do not edit by hand.

Tool	Description
apply_aircraft_setup(confirm=False)	Apply the declared aircraft profile to the FC, then save and reboot.
assign_switch(switch_channel, switch_positions, mode_per_position, confirm=False)	Map a multi-position switch's detents to flight modes in one call.
backup_config(label=None)	Save the current FC config to a timestamped backup file.
board_info()	Read flight-controller identity over MSP.
calibrate_accelerometer(confirm=False)	Calibrate the accelerometer (zero-level). Fixes most 'not level' / 'accel not
calibrate_magnetometer(confirm=False)	Calibrate the compass (magnetometer). Only useful if a compass is installed.
check_config()	Compare the FC's actual configuration against the declared aircraft profile.
check_failsafe()	Read and explain the failsafe configuration (what happens on RC loss).
clear_flight_mode(mode_name, confirm=False)	Remove all switch assignments for a flight mode (disables its slots via CLI 'aux').
cli(command, confirm_for_writes=False, props_removed=False)	Raw CLI escape hatch — run any iNAV CLI command directly.
cli_batch(commands, confirm_for_writes=False)	Run MANY CLI commands in ONE CLI session — a single reboot for the whole batch.
configure_gps(provider='UBLOX', sbas=None, confirm=False)	Enable the GPS feature and set the receiver provider / SBAS (atomic CLI write).
connect(port, baud=115200)	Open the serial connection to the FC and return board identity.
define_aircraft(name, wing_type, esc_protocol, cells, fc_target=None, motor_kv=None, motor_poles=14, servo_count=None, notes=None)	Define the aircraft hardware profile and generate a configuration plan.
diagnose()	Full diagnostic sweep — the flagship troubleshooter.
disconnect()	Close the serial connection to the FC.
find_fc(baud=115200, probe_all=False)	Auto-detect which serial port has a flight controller, so you don't guess.
get_aircraft_profile()	Return the currently declared aircraft profile.
get_status()	Read FC status via both MSP and CLI.
list_backups()	List saved config backups under ./backups/, newest first. No FC needed.
list_flight_modes()	List all available flight modes and their current switch assignments.
list_serial_ports()	List all available serial ports.
read_gps()	Live GPS status: fix type, satellites, position, speed, HDOP + nav-readiness.
read_rc_channels()	Read live RC channel values via MSP.
read_sensors()	Read live sensor values: attitude, per-sensor health, and analog (battery).
read_tuning()	Read fixed-wing PID gains, rates, and key filter cutoffs (via CLI).
restore_config(path, confirm=False)	Restore FC config by replaying a backup file's CLI commands, then save+reboot.
save_and_reboot(confirm=False)	Save the running config to EEPROM and reboot the FC.
set_failsafe(procedure=None, throttle_us=None, delay_s=None, off_delay_s=None, confirm=False)	Set the core failsafe behaviour (atomic CLI write: backup → apply → save+reboot).
set_flight_mode(mode_name, aux_channel, range_low, range_high, confirm=False)	Assign a flight mode to an aux channel range (read-modify-write via CLI 'aux').
set_nav(rth_altitude_m=None, rth_climb_first=None, rth_allow_landing=None, loiter_radius_m=None, confirm=False)	Set core fixed-wing navigation / RTH parameters (atomic CLI write).
set_pid(axis, p=None, i=None, d=None, ff=None, confirm=False)	Set fixed-wing PID gains for ONE axis (atomic CLI write).
suggest_mode_layout(skill_level='beginner', num_switches=2, has_gps=False)	Recommend a fixed-wing flight-mode/switch layout. Pure knowledge — no FC needed.
test_motor(motor, throttle_us=1100, duration_s=2.0, props_removed=False, confirm=False)	Spin ONE motor briefly for a bench test (direction / wiring / response).
why_wont_it_arm()	Decode the FC's arming-prevention flags into plain English.

License

MIT. This project ships its own MSP codec and does not import GPL libraries (uNAVlib / YAMSPy) at runtime, keeping it permissively licensed.