# Host SITL

Host SITL is Kaptan's deterministic closed-loop simulation tier. Gazebo sends
simulated IMU and declared noisy local position/velocity observations over a
private loopback protocol. The Rust process runs the ESKF, safety supervisor,
trajectory, controller, and allocator, then returns four virtual motor
fractions to Gazebo.

It is a pre-bench software gate, not a physical-flight validation.

## Run the closed loop

```sh
cd firmware
docker compose -f tools/sitl/compose.yaml up -d --build
tools/sitl/kaptan-sim ready
tools/sitl/kaptan-sim move 5 3 1 --wait
tools/sitl/kaptan-sim land 0 0 --wait
docker compose -f tools/sitl/compose.yaml down
```

For the reproducible command-path gate, use:

```sh
cd firmware
tools/sitl/e2e-smoke.sh
```

The smoke scenario verifies ascent, translation, descent, landing, flat-plane
proximity, and zero applied motor fractions after landing. Its reference world
contains only a visual landing pad; the pad has no collision geometry and
never contributes a controller or truth observation.

Open <https://app.gazebosim.org/visualization>, connect to
`ws://localhost:9002`, and leave authorization blank to view the world.

## Quad-X profile

SITL starts through the same central `ConfigManager` composition used by the
host protocol tests. Create and validate a private host profile file with:

```sh
kaptan-sitl config write-default kaptan-sitl.cbor
kaptan-sitl config validate kaptan-sitl.cbor
kaptan-sitl serve --config kaptan-sitl.cbor
```

The file selects the restart-only profile used to build the estimator,
controller, allocator envelope, safety supervisor, and optional log filter at
process start. It is not the raw GCS upload blob. `kaptan-sitl serve` retains
the central manager for that boot but does not yet open a MAVLink config/log
endpoint; see [Configuration](configuration.md) for the exact upload groundwork
and safety boundary.

## Limits

This model does not validate terrain, vision, flow/range sensing, wind,
vibration, battery/ESC behavior, sensor latency/jitter, actuator faults, or
physical touchdown sensing. Add those only as a reviewed sensor/contact model,
not as a display-only shortcut.