Load the build and HIL mechanics from agentrc's arduino skill

.claude/skills/build/SKILL.md

@@ -6,7 +6,9 @@ description: The Adafruit TinyUSB Arduino build contract. Use when a change must
 # Build contract
 
 `scripts/check_build.py` is the entry point for verifying a change; agents and workflows call it rather than composing
-`arduino-cli compile` lines.
+`arduino-cli compile` lines. It is this library's profile for agentrc's `arduino` skill (`arduino_build.py`), loaded
+from the agentrc commit `test/hil/agentrc.json` pins: run `python3 .claude/skills/hil-contract/scripts/agentrc_pin.py
+fetch` once per pin. That skill's page has the mechanics this library shares with Adafruit SPIFlash.
 
 ```bash
 B=.claude/skills/build/scripts/check_build.py
@@ -65,8 +67,11 @@ quotes `firstError` (and `error`). Each `warnings` entry is quoted in `notes`.
   dir for `flash_args`. Example eligibility mirrors ci-arduino `build_platform.py`: `.<platform>.test.skip`,
   a `.skip.txt` line equal to the platform, and `.<platform>.test.only` when any `.*.test.only` exists; a rig board
   takes its CI platform's files (`filters`). A board whose core is not installed is exit 2 naming
-  `arduino-cli core install`; a missing library dependency fails that sketch, the README's `arduino-cli lib install`
-  line installs them. Local cores need not be CI's versions; the record names what built.
+  `arduino-cli core install`. Local cores need not be CI's versions; the record names what built.
+- **Dependencies** (`arduino` skill): `library.properties` `depends=` plus `EXTRA_DEPENDENCIES` (CI's `ARDUINO_LIBS`
+  beyond it), and theirs, transitively, must be installed before a build: a missing one is exit 2 naming the
+  `arduino-cli lib install` line. A compile that takes any other library, outside the core, fails its sketch; the
+  JSON's `dependencies` and each row's `libraries` say what was used.
 - **Every compile** is `arduino-cli compile --clean --format json --warnings all --fqbn <F> --library <this checkout>
   --build-path <dir>`, so the core and every library rebuild from scratch and this library comes from this checkout
   whatever else is installed (the primary checkout under `~/Arduino/libraries`, a core's bundled copy). The build
@@ -90,10 +95,11 @@ quotes `firstError` (and `error`). Each `warnings` entry is quoted in `notes`.
   not checked, since the SAMD ELF's first starts at 0x0. For an esptool board it is the core's `flash_args`: a line of
   options, then each image at its offset, every file in the build dir, ascending, not overlapping, inside the span.
   A device sketch needs its VID:PID: a `-D` define, on ESP32 the variant's `pins_arduino.h` (the S3's 303a:1001),
-  else the library's fallback. It also refuses a foreign header that differs. It records HEAD, the FQBN, the platform
-  (id, version, install dir, and commit and dirty state when the core is a git checkout), the arduino-cli version, the
-  roster's and harness's sha256, the board's role, ESP `chip` and `fixture` (path and sha256), and per sketch its
-  images with sha256, load spans, VID:PID, foreign headers and, for esptool, `segments` (the build's `flash_args`
+  else the library's fallback. It also refuses a foreign header that differs. It records (schema 2, the `arduino`
+  skill's The HIL build record) HEAD, the FQBN, the platform (id, version, install dir, and commit and dirty state
+  when the core is a git checkout), the arduino-cli version, the resolved dependencies with their contents' sha256,
+  the roster's sha256, the contract files' and the agentrc engines' sha256, the board's role, ESP `chip` and `fixture` (path and sha256), and per sketch its
+  images with sha256, load spans, VID:PID, foreign headers, used libraries and, for esptool, `segments` (the build's `flash_args`
   hashed beside them); paths are checkout-relative so the record stages to a rig unchanged.
 - **Experimental records** (`--experimental`, with `--record`) are for debug and instrumentation: a dirty tree and
   `--build-property` are allowed, untracked files under `src/`, `examples/` or `test/hil/` are refused (put

.claude/skills/hil-contract/SKILL.md

@@ -5,8 +5,9 @@ description: The Adafruit TinyUSB Arduino HIL contract, under agentrc's `hil` ru
 
 # HIL contract
 
-Read agentrc's `hil` skill first; this page supplies its contract sections. Manual runs only: no CI job runs this
-battery. Scripts, all in `scripts/`:
+Read agentrc's `hil` skill first; this page supplies its contract sections. The mechanics are agentrc's `arduino`
+skill (`arduino_hil.py`, `arduino_remote.py`), shared with Adafruit SPIFlash; the battery, the host step and the roster
+checks are this library's (`hil_test.py`). Manual runs only: no CI job runs this battery. Scripts, all in `scripts/`:
 
 - `hil_test.py`: the harness on the host with the boards.
 - `hil_remote.py`: drives the harness on ci.lan from the dev PC that built the firmware.
@@ -34,10 +35,11 @@ A roster entry:
 
 - `name`: the board's `check_build.py` rig name, which is also its lock name. The names are tinyusb's farm names,
   so this harness and tinyusb's exclude each other on a shared board.
-- `uid`: the DUT's USB serial under Arduino firmware (Limits, commissioning); for a host board or a `usb_port`
+- `uid`: the DUT's USB serial under Arduino firmware (Limits, commissioning); for a host board or a `no_serial`
   board, the board's tinyusb farm id, unused here.
-- `usb_port`: the sysfs bus port the DUT enumerates at, for firmware with an empty serial string (ESP32 under
-  Arduino, Limits); the harness then tells the DUT by port, not serial. Required for esptool boards.
+- `usb_port`: the sysfs bus port the DUT enumerates at; the DUT must be there. Required for esptool boards.
+- `no_serial`: `true` for firmware with an empty serial string (ESP32 under Arduino, Limits): the harness then tells
+  the DUT by `usb_port` alone, as the serial-less device there.
 - `flasher`: `name` `openocd`, `jlink` or `esptool`, `uid` the probe serial (esptool: its USB-UART bridge's), `args`,
   for openocd `vid_pid` and `verify`.
 - `debug.openocd`: the openocd config the GDB session uses; with `debug.tool` `openocd-esp32`, exactly
@@ -274,11 +276,13 @@ human.
   reached the device (usbmon, 2026-11-02). The open is not bounded by the test deadline; allow for it in any host-side
   timing claim.
 - **Commissioning.** `hil_test.py commission -b <board> ROSTER` finds the DUT's serial under Arduino firmware
-  (exactly one device re-enumerating across a flash and a probe reset), or for a `usb_port` board its port. It runs
+  (exactly one device re-enumerating across a flash and a probe reset, at the roster's `usb_port` when it has one), or
+  for a `no_serial` board its port, then checks the restoration sketch with `cdc_echo`. It runs
   from a checkout on the board's host and is not staged by `hil_remote.py`; host boards have nothing to commission.
   The ci.lan boards' uids come from tinyusb's roster; the battery confirmed the Pico's and the Fruit Jam's.
 - **ESP32 identity:** under Arduino the ESP32-S3 and ESP32-P4 enumerate with an empty serial string (the library's ESP32
-  `TinyUSB_Port_GetSerialNumber` returns none), so the roster pins each by `usb_port` (S3 11-1.3, P4 11-1.1 on ci.lan):
+  `TinyUSB_Port_GetSerialNumber` returns none), so the roster marks each `no_serial` and pins it by `usb_port` (S3
+  11-1.3, P4 11-1.1 on ci.lan):
   the DUT candidate is the device there with no cached sysfs `serial`, since while esptool runs the S3's ROM
   USB-Serial/JTAG appears at the same port as `303a:1001` with its MAC as serial; a failed serial read would also leave
   none, so the test run on the candidate is the evidence. The S3 enumerates as `303a:1001`, its core variant's

.claude/skills/hil-contract/scripts/agentrc_pin.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-"""The agentrc commit the HIL harness loads its shared scripts from (agentrc `hil` skill, Shared mechanisms).
+"""The agentrc commit the build and HIL contracts load their shared scripts from (agentrc `arduino` and `hil` skills).
 
   agentrc_pin.py fetch    fetch the pinned commit into the user cache (never touches another agentrc checkout)
   agentrc_pin.py check    exit 0 when the cached checkout is the pin and clean, else 1 naming why
@@ -21,6 +21,9 @@
 ROOT = Path(__file__).resolve().parents[4]
 PIN_FILE = ROOT / 'test' / 'hil' / 'agentrc.json'
 FETCH_HINT = 'python3 .claude/skills/hil-contract/scripts/agentrc_pin.py fetch'
+# the agentrc engines the contracts run; their FILES closures are what a staged rig tree carries and a record binds
+ENGINES = ('skills/arduino/scripts/arduino_build.py', 'skills/arduino/scripts/arduino_hil.py',
+           'skills/arduino/scripts/arduino_remote.py')
 
 
 class PinError(Exception):
@@ -108,7 +111,8 @@ def closure(root, scripts):
     out = set()
     for rel in scripts:
         out.add(rel)
-        out.update(files_of(root, rel))
+        if (Path(root) / rel).is_file():
+            out.update(files_of(root, rel))
     missing = sorted(r for r in out if not (Path(root) / r).is_file())
     if missing:
         raise PinError(f'agentrc at {root} lacks {missing}')
@@ -126,6 +130,29 @@ def loader(root):
     return sys.modules[spec.name].load(spec.name, spec.origin)
 
 
+def staged():
+    """A rig tree hil_remote.py staged: no .git, its agentrc files under agentrc/."""
+    return not (ROOT / '.git').exists() and (ROOT / 'agentrc').is_dir()
+
+
+def root():
+    """The agentrc this process loads from: the staged copy on a rig, else the pinned checkout."""
+    return ROOT / 'agentrc' if staged() else checkout()
+
+
+def load(rel):
+    """agentrc's `rel`, loaded through its hil_load once the engines' closure is all present."""
+    r = root()
+    closure(r, ENGINES)
+    return loader(r).load_file(rel)
+
+
+def identity():
+    """{commit, root, files}: the pin, where it is loaded from, and the engines' closure (agentrc-relative)."""
+    r = root()
+    return {'commit': pin()[1], 'root': r, 'files': closure(r, ENGINES)}
+
+
 def main(argv):
     cmd = argv[0] if argv else ''
     try: