hil: split hil_test.py into hil_lock/hil_flash, add pool_check, update rig probes (#3794)

test/hil: add board-pool health check, split hil_test into focused modules (#3794)

Add test/hil/hil_pool_check.py: per-board rig health scan — probe presence,
light-example flash (dfu_runtime; device_info + serial check for host-only
boards), uid re-enumeration, safe recovery (probe authorized-toggle, board
reset), verified board_test re-park, USB topology report, and a markdown
summary table. Missing firmware is built on the spot (tools/build.py, idf.py
for espressif, one get_deps retry); row statuses: ok, flash-failed, failed,
locked. Board locks are always respected, never bypassed.

Refactor hil_test.py into hil_lock.py (flock protocol, controller permits,
hold/release/status CLI; replaces board_lock.py) and hil_flash.py (flashers,
find_firmware, run_cmd). Update WCH probe uids and the board roster in
tinyusb.json; add the hil-pool-check skill.

2 files changed, 496 insertions, 0 deletions

diff --git a/docs/superpowers/plans/2026-07-28-hil-test-split.md b/docs/superpowers/plans/2026-07-28-hil-test-split.md
new file mode 100644
index 000000000..6b8528973
--- /dev/null
+++ b/docs/superpowers/plans/2026-07-28-hil-test-split.md
@@ -0,0 +1,355 @@
+# hil_test.py Split Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Split `test/hil/hil_test.py` (2370 ln) into a test-focused core plus `hil_lock.py` (board locks + controller permits + operator CLI, superseding `board_lock.py`) and `hil_flash.py` (run_cmd + flash backends + firmware/serial lookup), with no behavior change.
+
+**Architecture:** Pure code motion per `docs/superpowers/specs/2026-07-28-hil-test-refactor-design.md`. Import graph: `hil_test` → {`hil_lock`, `hil_flash`}; helpers import nothing local. Call sites use module-qualified names (`hil_lock.flash_permit(...)`), never wildcard mirroring.
+
+**Tech Stack:** Python 3.11+ (existing `TypedDict`/`NotRequired` usage), stdlib only in the helpers (fcntl, json, glob, multiprocessing objects passed in).
+
+## Global Constraints
+
+- Work in worktree `.claude/worktrees/hil-test-split` (branch `claude/hil-test-split`); never touch the primary checkout.
+- Behavior-preserving: `hil_test.py` CLI args, log lines, report format, lock/permit semantics, flash behavior all byte-identical. The ONLY user-visible change is the CLI filename `board_lock.py` → `hil_lock.py`.
+- Moved functions are moved **verbatim** — no reformatting, no comment editing, no "improvements". A diff of a moved function's body against its old self must be empty.
+- Commit messages: imperative, scoped, no Co-Authored-By/Claude-Session trailers.
+- Every commit leaves the tree working: `python3 -m py_compile` clean on all touched modules, and `python3 .claude/skills/hil/pool_check.py --scan-only` exits 0 (safe on the rig: scan-only takes no locks, flashes nothing).
+- Hardware steps (Task 4) run on the `ci` rig only, from this worktree, and rely on the tools' own board flocks — never pre-hold boards you are about to run `hil_test.py`/`pool_check.py` on.
+
+---
+
+### Task 1: Create hil_flash.py; repoint hil_test + pool_check flash call sites
+
+**Files:**
+- Create: `test/hil/hil_flash.py`
+- Modify: `test/hil/hil_test.py` (delete moved code; add import; qualify call sites)
+- Modify: `.claude/skills/hil/pool_check.py` (flash-related imports)
+- Modify: `test/hil/hil_ci.sh` (scp list)
+
+**Interfaces:**
+- Produces (used by Tasks 2-4): module `hil_flash` with `CMD_TIMEOUT`, `run_cmd(cmd, cwd=None, timeout=CMD_TIMEOUT)`, `cmd_stdout_text(out)`, `OPENCOD_ADI_PATH`, `TINYUSB_ROOT`, `flash_jlink/reset_jlink`, `flash_stlink/reset_stlink`, `flash_stflash/reset_stflash`, `flash_openocd/reset_openocd`, `flash_openocd_wch/reset_openocd_wch`, `flash_openocd_adi/reset_openocd_adi`, `flash_wlink_rs/reset_wlink_rs`, `flash_esptool/reset_esptool`, `flash_uniflash/reset_uniflash`, `flash_lm4flash/reset_lm4flash`, `find_firmware(variant, example)`, `get_serial_dev(id, vendor_str, product_str, ifnum)`, module globals `build_dir = 'cmake-build'`, `verbose = False`.
+
+- [ ] **Step 1: Create `test/hil/hil_flash.py`**
+
+Header (new code), then the moved blocks verbatim:
+
+```python
+#!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+# Firmware flashing for the TinyUSB HIL rig: run_cmd, one flash_*/reset_* pair per
+# flasher type (dispatched by config name via getattr), find_firmware, and the
+# fixture serial-port resolver get_serial_dev (here, not hil_test: flash_esptool
+# needs it and helpers must not import hil_test).
+# Callers set module globals `build_dir` and `verbose` (hil_test.main from argparse,
+# pool_check directly) exactly as they set hil_test's globals today.
+
+import glob
+import json
+import os
+import signal
+import subprocess
+import sys
+from pathlib import Path
+
+verbose = False
+build_dir = 'cmake-build'
+```
+
+Then MOVE (cut from `hil_test.py`, paste unchanged, in this order):
+1. `CMD_TIMEOUT = int(os.getenv('HIL_CMD_TIMEOUT', '180'))` (from the constants block; leave `POOL_TIMEOUT`/`SERIAL_*_TIMEOUT` in hil_test)
+2. `def cmd_stdout_text(out)`
+3. `OPENCOD_ADI_PATH = Path.home() / 'app' / 'openocd_adi'` and `TINYUSB_ROOT = Path(__file__).resolve().parents[2]`
+4. `def get_serial_dev(id, vendor_str, product_str, ifnum)`
+5. `def run_cmd(cmd, cwd=None, timeout=CMD_TIMEOUT)`
+6. All ten `flash_*`/`reset_*` pairs listed in Interfaces, in current file order
+7. `def find_firmware(variant, example)`
+
+- [ ] **Step 2: Delete the moved code from `hil_test.py` and qualify call sites**
+
+In `hil_test.py`: add `import hil_flash` under the existing imports; delete the moved definitions and the `build_dir = 'cmake-build'` global (line ~165) plus `global build_dir` in `main`. Repoint every use, all module-qualified:
+- `globals()[f'flash_{...}']` → `getattr(hil_flash, f'flash_{...}')` (1 site, in `test_example`)
+- `globals()[f'reset_{...}']` → `getattr(hil_flash, f'reset_{...}')` (3 sites: `test_host_device_info`, `test_host_cdc_msc_hid`, `test_host_msc_file_explorer`)
+- bare `run_cmd(` → `hil_flash.run_cmd(` ; `cmd_stdout_text(` → `hil_flash.cmd_stdout_text(` ; `find_firmware(` → `hil_flash.find_firmware(` ; `get_serial_dev(` → `hil_flash.get_serial_dev(` ; `TINYUSB_ROOT` → `hil_flash.TINYUSB_ROOT` (in `build_board`, `CONTROLLER_CACHE` stays hil_test-local)
+- In `main()`: `build_dir = args.build_dir` → `hil_flash.build_dir = args.build_dir`; where `verbose` is set, add `hil_flash.verbose = args.verbose` (hil_test keeps its own `verbose` for test-side prints)
+- `run_cmd`'s `elif verbose:` branch now reads `hil_flash.verbose` (it moved with the function — verify it references the module-local name, not hil_test's)
+
+Find every remaining call site mechanically:
+
+Run: `grep -nE 'run_cmd|cmd_stdout_text|find_firmware|get_serial_dev|flash_[a-z]|reset_[a-z]|TINYUSB_ROOT|OPENCOD' test/hil/hil_test.py | grep -v hil_flash`
+Expected: only hits inside comments/strings and the `reset_{flasher}` dispatch f-strings already qualified.
+
+- [ ] **Step 3: Repoint pool_check's flash imports**
+
+In `.claude/skills/hil/pool_check.py`: add `import hil_flash` next to `import hil_test`; replace `hil_test.find_firmware` → `hil_flash.find_firmware` (3 sites), `hil_test.cmd_stdout_text` → `hil_flash.cmd_stdout_text`, `hil_test.get_serial_dev` → `hil_flash.get_serial_dev`, `hil_test.TINYUSB_ROOT` → `hil_flash.TINYUSB_ROOT`, `hil_test.build_dir` → `hil_flash.build_dir` (2 sites incl. `main`'s assignment), `hil_test.verbose = args.verbose` → `hil_flash.verbose = args.verbose`, `getattr(hil_test, f'flash_...')`/`getattr(hil_test, f'reset_...')` → `getattr(hil_flash, ...)` (4 sites). Keep `import hil_test` and the pymtp shim for now (locks still live there; removed in Task 2).
+
+- [ ] **Step 4: Add hil_flash.py to the hil_ci.sh scp list**
+
+```bash
+scp -q "$ROOT_DIR/test/hil/hil_test.py" \
+       "$ROOT_DIR/test/hil/hil_flash.py" \
+       "$ROOT_DIR/test/hil/pymtp.py" \
+       "$CONFIG" \
+       "$REMOTE:$REMOTE_DIR/test/hil/"
+```
+
+- [ ] **Step 5: Verify**
+
+Run: `python3 -m py_compile test/hil/hil_flash.py test/hil/hil_test.py .claude/skills/hil/pool_check.py && python3 test/hil/hil_test.py --help >/dev/null && python3 .claude/skills/hil/pool_check.py --scan-only`
+Expected: compiles; help prints nothing to stderr; scan-only prints the table and exits 0.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add test/hil/hil_flash.py test/hil/hil_test.py test/hil/hil_ci.sh .claude/skills/hil/pool_check.py
+git commit -m "hil: extract flashing into hil_flash.py"
+```
+
+---
+
+### Task 2: Create hil_lock.py core (flock protocol + controller permits); repoint hil_test + pool_check
+
+**Files:**
+- Create: `test/hil/hil_lock.py`
+- Modify: `test/hil/hil_test.py`
+- Modify: `.claude/skills/hil/pool_check.py`
+- Modify: `test/hil/hil_ci.sh`
+
+**Interfaces:**
+- Produces: module `hil_lock` with `BOARD_LOCK_DIR`, `CI_REASON = 'hil_test.py'`, `lock_path(board)`, `flock_nb(board)`, `write_record(fh, reason)`, `clear_record(fh)`, `read_record(board)`, `acquire_board_lock(board, reason=CI_REASON)`, `FLASH_PARALLEL`, `USBTEST_PARALLEL`, `CONTROLLER_SLOTS`, `controller_of(uid)`, `controller_slot(pci)`, `controller_permit`, `flash_permit(uid)`, `usbtest_permit(uid)`, `init_scheduling(b_sems, f_sems, cmap, cmeta, hints, log_fn=None)`.
+
+- [ ] **Step 1: Create `test/hil/hil_lock.py` with the flock core**
+
+New code (the protocol, factored from today's three copies — `board_lock.py` `cmd_hold`/`read_info`, `hil_test.acquire_board_lock`, pool_check `lock_board`; behavior identical to `hil_test.acquire_board_lock` for the acquire path):
+
+```python
+#!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+"""Board locks + controller permits for the TinyUSB HIL rig.
+
+Board locks are kernel flocks in BOARD_LOCK_DIR arbitrating hardware access
+between dev sessions and CI's hil_test.py (never stop the actions-runner).
+Controller permits are in-process semaphores budgeting flashes and usbtest
+batteries per host controller; they have no CLI meaning. The CLI below
+(hold/release/status) manages board locks only; it supersedes board_lock.py.
+"""
+import argparse
+import fcntl
+import glob
+import json
+import os
+import re
+import select
+import signal
+import sys
+import time
+
+BOARD_LOCK_DIR = '/tmp/tinyusb-hil-locks'
+CI_REASON = 'hil_test.py'   # release-protected holder tag (release refuses to kill it)
+PROFILE = os.environ.get('HIL_PROFILE') == '1'
+
+
+def lock_path(board: str) -> str:
+    return os.path.join(BOARD_LOCK_DIR, f'{board}.lock')
+
+
+def flock_nb(board: str):
+    """Open-or-create the lock file WITHOUT truncating (a losing racer must not
+    wipe the winner's record) and take LOCK_EX|LOCK_NB. Returns the open handle;
+    raises OSError when the flock is held elsewhere (handle already closed)."""
+    fd = os.open(lock_path(board), os.O_RDWR | os.O_CREAT, 0o666)
+    fh = os.fdopen(fd, 'r+')
+    try:
+        fcntl.flock(fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except OSError:
+        fh.close()
+        raise
+    return fh
+
+
+def write_record(fh, reason: str) -> None:
+    """Best-effort holder record; the flock itself is already held."""
+    try:
+        fh.truncate(0)
+        fh.seek(0)
+        json.dump({'pid': os.getpid(), 'reason': reason,
+                   'since': time.strftime('%Y-%m-%dT%H:%M:%S%z')}, fh)
+        fh.flush()
+    except OSError:
+        pass
+
+
+def clear_record(fh) -> None:
+    """Clear our record before dropping the flock so records stay truthful."""
+    try:
+        fh.truncate(0)
+    except OSError:
+        pass
+
+
+def read_record(board: str):
+    try:
+        with open(lock_path(board)) as f:
+            return json.load(f)
+    except (OSError, ValueError):
+        return None
+```
+
+Then MOVE `acquire_board_lock` from `hil_test.py` verbatim, with exactly two mechanical edits: signature becomes `def acquire_board_lock(board_name, reason=CI_REASON):` and the record-write dict's `'reason': 'hil_test.py'` becomes `'reason': reason`. Do NOT rewrite its body in terms of `flock_nb` — on conflict it reads holder info from the still-open handle before closing, which `flock_nb` (closes on conflict) cannot provide; the fail-open warning text and RuntimeError message must survive character-for-character.
+
+- [ ] **Step 2: Move the controller-permit block into `hil_lock.py`**
+
+MOVE verbatim from `hil_test.py`: the scheduling comment block + `FLASH_PARALLEL`, `USBTEST_PARALLEL`, `CONTROLLER_SLOTS`, the five module globals (`usbtest_sems`, `flash_sems`, `controller_map`, `controller_meta`, `controller_hints`), `controller_of`, `controller_slot`, `controller_permit`, `flash_permit`, `usbtest_permit`. Two mechanical adaptations:
+- add at module scope `log = print` and a setter, replacing the two `log_line(...)` calls inside `controller_of`/`controller_permit` with `log(...)`:
+
+```python
+log = print  # hil_test.init_worker points this at log_line via init_scheduling
+
+
+def init_scheduling(b_sems, f_sems, cmap, cmeta, hints, log_fn=None):
+    """Install per-worker scheduling state (called from hil_test.init_worker)."""
+    global usbtest_sems, flash_sems, controller_map, controller_meta, controller_hints, log
+    usbtest_sems, flash_sems = b_sems, f_sems
+    controller_map, controller_meta, controller_hints = cmap, cmeta, hints
+    if log_fn is not None:
+        log = log_fn
+```
+
+- `PROFILE` inside `controller_permit` now resolves to hil_lock's own module constant (defined in Step 1).
+
+- [ ] **Step 3: Repoint `hil_test.py`**
+
+Add `import hil_lock`. Delete the moved lock + permit code and the five globals. `init_worker` keeps its exact signature and initargs; its body sets the hil_test globals it still owns (`print_lock`, `shuffle_seed`) and forwards the rest:
+
+```python
+def init_worker(lock, seed, b_mutexes, f_sems, cmap, cmeta, hints_by_uid):
+    global print_lock, shuffle_seed
+    print_lock = lock
+    shuffle_seed = seed
+    hil_lock.init_scheduling(b_mutexes, f_sems, cmap, cmeta, hints_by_uid, log_fn=log_line)
+```
+
+Qualify remaining uses: `acquire_board_lock(name)` → `hil_lock.acquire_board_lock(name)` (in `test_board`), `flash_permit(` → `hil_lock.flash_permit(`, `usbtest_permit(` → `hil_lock.usbtest_permit(`, and `main()`'s startup log line + Semaphore construction read `hil_lock.FLASH_PARALLEL`/`hil_lock.USBTEST_PARALLEL`/`hil_lock.CONTROLLER_SLOTS`. `controller_map` reads in the hint-persistence block of `main` use the Manager dict it already holds locally (`cmap`) — no hil_lock global access there; verify.
+
+- [ ] **Step 4: Repoint pool_check to hil_lock and drop its private copies + hil_test import**
+
+In `pool_check.py`: replace `lock_board`/`unlock_board` bodies with the shared core —
+
+```python
+import hil_lock
+
+def lock_board(name: str):
+    try:
+        fh = hil_lock.flock_nb(name)
+    except OSError:
+        info = hil_lock.read_record(name)
+        return json.dumps(info) if info else 'unknown holder'
+    hil_lock.write_record(fh, 'pool_check')
+    return fh
+
+
+def unlock_board(fh) -> None:
+    hil_lock.clear_record(fh)
+    fh.close()
+```
+
+(Behavior note: `lock_board` currently returns the raw record text; JSON-dumping the parsed record is equivalent for display. `hil_lock.BOARD_LOCK_DIR` replaces `hil_test.BOARD_LOCK_DIR`; `os.makedirs(...)` call stays, now on `hil_lock.BOARD_LOCK_DIR`.) Then delete `import hil_test` and the pymtp stub block (`try: import pymtp ... sys.modules['pymtp'] = ...`) — pool_check now imports only `hil_lock` + `hil_flash`.
+
+Run: `grep -n 'hil_test' .claude/skills/hil/pool_check.py`
+Expected: only the docstring mention of the protocol/history, no code references (update the docstring's "imports test/hil/hil_test.py" line to name hil_lock/hil_flash).
+
+- [ ] **Step 5: Add hil_lock.py to the hil_ci.sh scp list** (same block as Task 1 Step 4, one more line: `"$ROOT_DIR/test/hil/hil_lock.py" \`)
+
+- [ ] **Step 6: Verify**
+
+Run: `python3 -m py_compile test/hil/hil_lock.py test/hil/hil_test.py .claude/skills/hil/pool_check.py && python3 test/hil/hil_test.py --help >/dev/null && python3 .claude/skills/hil/pool_check.py --scan-only`
+Expected: clean compile, working scan table, exit 0.
+
+- [ ] **Step 7: Commit**
+
+```bash
+git add test/hil/hil_lock.py test/hil/hil_test.py test/hil/hil_ci.sh .claude/skills/hil/pool_check.py
+git commit -m "hil: extract board locks and controller permits into hil_lock.py"
+```
+
+---
+
+### Task 3: Absorb board_lock.py CLI into hil_lock.py; delete board_lock.py; rename in docs
+
+**Files:**
+- Modify: `test/hil/hil_lock.py` (append CLI)
+- Delete: `test/hil/board_lock.py`
+- Modify: `.claude/skills/hil/SKILL.md`, `.claude/agents/hil-operator.md`, `.claude/agents/target-debugger.md`, `.claude/skills/etm-trace/SKILL.md`, `.claude/skills/usb-kernel-recover/SKILL.md`, `.claude/skills/target-debug/SKILL.md`
+
+**Interfaces:**
+- Produces: `python3 test/hil/hil_lock.py hold|release|status` — identical subcommands, flags, output, and exit codes to today's `board_lock.py`.
+
+- [ ] **Step 1: Move the CLI from `board_lock.py` into `hil_lock.py`**
+
+MOVE verbatim to the end of `hil_lock.py`: `boards_from_config`, `is_locked`, `cmd_hold`, `cmd_release`, `cmd_status`, `main()`, and the `if __name__ == '__main__':` guard. Mechanical adaptations only:
+- `LOCK_DIR` → `BOARD_LOCK_DIR` (all sites), `lock_path` already exists (delete the duplicate), `read_info` → `read_record` (all sites; delete the duplicate definition)
+- `cmd_hold`'s holder loop body (the open/flock/json.dump block) becomes `fh = flock_nb(b)` + `write_record(fh, reason)` inside the existing try/except OSError
+- `_bow_out`'s per-handle truncate loop becomes `clear_record(h)` per handle
+- `cmd_release`'s probe uses `flock_nb(b)` in a try/except OSError (held → existing record/victim logic, with the literal `'hil_test.py'` comparison becoming `CI_REASON`); the free-path truncate becomes `clear_record(fh)`
+- `main()`'s module docstring reference for `--help` text: keep the usage lines, updating the tool name to `hil_lock.py`
+
+Then delete `test/hil/board_lock.py` (`git rm test/hil/board_lock.py`).
+
+- [ ] **Step 2: Rename `board_lock.py` → `hil_lock.py` in the six live docs**
+
+Run: `cd <worktree> && sed -i 's/board_lock\.py/hil_lock.py/g' .claude/skills/hil/SKILL.md .claude/agents/hil-operator.md .claude/agents/target-debugger.md .claude/skills/etm-trace/SKILL.md .claude/skills/usb-kernel-recover/SKILL.md .claude/skills/target-debug/SKILL.md`
+Then: `grep -rn 'board_lock' .claude/ test/ --include='*.md' --include='*.py' --include='*.sh'`
+Expected: zero hits outside `docs/superpowers/` history (which stays untouched).
+
+- [ ] **Step 3: Verify CLI behavior end-to-end**
+
+```bash
+python3 test/hil/hil_lock.py status                                        # expect: no locks (or current holders)
+python3 test/hil/hil_lock.py hold stm32f072disco --reason "split test" &
+sleep 1
+python3 test/hil/hil_lock.py status                                        # expect: stm32f072disco: {... 'reason': 'split test' ...}
+python3 test/hil/hil_lock.py hold stm32f072disco --reason "rival" || echo "conflict OK"   # expect: ERROR ... locked + conflict OK
+python3 test/hil/hil_lock.py release stm32f072disco                        # expect: released holder pid NNN
+python3 test/hil/hil_lock.py status                                        # expect: no locks
+```
+
+Also verify CI-holder protection: create a fake record `echo '{"pid": 1, "reason": "hil_test.py"}' > /tmp/tinyusb-hil-locks/faketest.lock` — since pid 1 holds no flock, `release faketest` must clear the stale record without printing the mid-test error; then `rm -f /tmp/tinyusb-hil-locks/faketest.lock`.
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add -A test/hil .claude
+git commit -m "hil: fold board_lock CLI into hil_lock.py, retire board_lock.py"
+```
+
+---
+
+### Task 4: Rig verification + pre-commit
+
+**Files:** none new (fixes only if verification fails)
+
+- [ ] **Step 1: pool_check flash path on one board**
+
+Run: `python3 .claude/skills/hil/pool_check.py -b stm32f407disco`
+Expected: `✅ dfu_runtime  ✅ cafe:...`, exit 0.
+
+- [ ] **Step 2: Capture a pre-refactor baseline report**
+
+Run: `cd /home/hathach/code/tinyusb && python3 test/hil/hil_test.py -b stm32f407disco -B examples test/hil/tinyusb.json && cp hil_report.md /tmp/claude-1000/-home-hathach-code-tinyusb/*/scratchpad/hil_report_master.md`
+(Primary checkout = pre-refactor code but same rig/config; its working tree already carries the new probe uids.)
+
+- [ ] **Step 3: Run the same board from the worktree and diff the report shape**
+
+Run: `cd .claude/worktrees/hil-test-split && python3 test/hil/hil_test.py -b stm32f407disco -B /home/hathach/code/tinyusb/examples test/hil/tinyusb.json && diff <(sed 's/[0-9.]*s//g;s/[0-9.]* [kMG]B\/s//g' hil_report.md) <(sed 's/[0-9.]*s//g;s/[0-9.]* [kMG]B\/s//g' /tmp/claude-1000/-home-hathach-code-tinyusb/*/scratchpad/hil_report_master.md)`
+Expected: empty diff after stripping timings/speeds. Note: `-B` accepts the absolute path so the worktree run reuses the primary checkout's built firmware; `find_firmware` resolves `TINYUSB_ROOT/<build_dir>` and an absolute `-B` overrides relative rooting — if it does not (Path join semantics), instead symlink `ln -s /home/hathach/code/tinyusb/examples/cmake-build-stm32f407disco examples/cmake-build-stm32f407disco` in the worktree and use `-B examples`.
+
+- [ ] **Step 4: pre-commit + final grep hygiene**
+
+Run: `pre-commit run --files test/hil/hil_test.py test/hil/hil_lock.py test/hil/hil_flash.py test/hil/hil_ci.sh .claude/skills/hil/pool_check.py $(git diff --name-only HEAD~3 -- '*.md')`
+Expected: all hooks pass.
+
+- [ ] **Step 5: Commit any verification fixes**
+
+```bash
+git add -A && git commit -m "hil: post-split verification fixes"   # only if Steps 1-4 required changes
+```
diff --git a/docs/superpowers/specs/2026-07-28-hil-test-refactor-design.md b/docs/superpowers/specs/2026-07-28-hil-test-refactor-design.md
new file mode 100644
index 000000000..3cd202d95
--- /dev/null
+++ b/docs/superpowers/specs/2026-07-28-hil-test-refactor-design.md
@@ -0,0 +1,141 @@
+# hil_test.py refactor: test core + infra helpers
+
+**Date:** 2026-07-28
+**Branch:** `claude/hil-test-split` (based on `claude/hil-pool-check`, which adds `pool_check.py`)
+
+## Motivation
+
+`test/hil/hil_test.py` is 2370 lines mixing five concerns: board-lock protocol, per-controller
+scheduling permits, flash/reset backends, the actual per-example tests, and orchestration/report/CLI.
+The lock protocol additionally exists in three copies (`hil_test.py`, `board_lock.py`,
+`.claude/skills/hil/pool_check.py`), which has already produced drift (pool_check's copy lacks
+hil_test's fail-open and error guards). Splitting the infrastructure out makes `hil_test.py`
+test-focused and gives external tools (pool_check) one canonical import for locks, permits, and
+flashing.
+
+## Goal / non-goals
+
+**Goal:** behavior-preserving code motion. `hil_test.py`'s CLI, arguments, output, report format,
+and runtime behavior stay byte-identical. One deliberate user-visible change: the operator lock CLI
+moves from `board_lock.py` to `hil_lock.py` (same subcommands, same behavior); `board_lock.py` is
+deleted.
+
+**Non-goals (explicit follow-ups, not this change):**
+- The 15 pool_check findings from the 2026-07-28 code review (exception isolation, park-on-failure,
+  espressif coverage, probe-recovery criterion, etc.).
+- pool_check adopting `flash_permit` controller budgeting (enabled by this split).
+- Any change to lock semantics, permit widths, flash behavior, or test logic.
+
+## Resulting layout (`test/hil/`)
+
+| File | ~Lines | Role |
+|---|---|---|
+| `hil_test.py` | 1600 | tests + orchestration + report + CLI (unchanged interface) |
+| `hil_lock.py` (new) | 420 | board-lock protocol + controller permits + operator CLI |
+| `hil_flash.py` (new) | 250 | `run_cmd` + flash/reset backends + `find_firmware` |
+| `board_lock.py` | deleted | superseded by `hil_lock.py` |
+
+Import graph: `hil_test` → {`hil_lock`, `hil_flash`}; the helpers import nothing local (no cycles).
+`pool_check.py` imports all three.
+
+## hil_lock.py
+
+Docstring states the scope: board locks + controller flash/battery permits; the CLI manages board
+locks only (permits are in-process semaphores with no CLI meaning).
+
+**Flock core** (protocol defined once; moved from `board_lock.py`/`hil_test.py`):
+- `BOARD_LOCK_DIR = '/tmp/tinyusb-hil-locks'`, `lock_path(board)`
+- `CI_REASON = 'hil_test.py'` — the release-protected holder tag (release refuses to kill it)
+- `flock_nb(board) -> fh` — `os.open(O_RDWR|O_CREAT, 0o666)` **without O_TRUNC** (a losing racer
+  must not wipe the winner's record), `fdopen('r+')`, `LOCK_EX|LOCK_NB`; raises `OSError` when held
+- `write_record(fh, reason)` — truncate+seek+`json.dump({pid, reason, since})`+flush
+- `clear_record(fh)` — truncate(0), swallow OSError (records stay truthful on release)
+- `read_record(board) -> dict | None` — today's `board_lock.read_info`
+- `acquire_board_lock(board, reason=CI_REASON) -> fh | None` — today's `hil_test.acquire_board_lock`
+  with a `reason` parameter: `HIL_NO_BOARD_LOCK=1` bypass, fail-open with warning on lock-dir
+  OSError, `RuntimeError` carrying holder info on conflict
+
+**Controller permits** (moved verbatim from `hil_test.py`):
+- `FLASH_PARALLEL`, `USBTEST_PARALLEL`, `CONTROLLER_SLOTS` (env-overridable as today)
+- `controller_of(uid)`, `controller_slot(pci)`, `controller_permit`, `flash_permit(uid)`,
+  `usbtest_permit(uid)`
+- Per-worker globals (`usbtest_sems`, `flash_sems`, `controller_map`, `controller_meta`,
+  `controller_hints`) set by a new `init_scheduling(sems, fsems, cmap, cmeta, hints)` hook that
+  `hil_test.init_worker` calls from the Pool initializer. `controller_permit`'s PROFILE logging
+  calls back through a module-level `log = print`-style hook that `hil_test` points at `log_line`
+  during `init_scheduling` (keeps helpers free of hil_test imports). The `PROFILE` env flag
+  (`HIL_PROFILE=1`) is read independently in `hil_lock` at import, same derivation as today.
+
+**Operator CLI** (moved verbatim from `board_lock.py`): `hold`/`release`/`status` subcommands with
+the daemon-holder machinery (double-fork, setsid, stdio detach, success pipe, SIGTERM bow-out),
+release policy (probe the flock; protect `CI_REASON` holders; SIGTERM other recorded pids),
+`is_locked` pid-liveness, `--all`/`--config` roster handling. The hold/release/status internals
+switch to the flock-core helpers above; observable behavior unchanged.
+
+## hil_flash.py
+
+Moved verbatim from `hil_test.py`:
+- `CMD_TIMEOUT` (env-overridable), `run_cmd(cmd, cwd, timeout)`, `cmd_stdout_text(out)`
+- `OPENCOD_ADI_PATH`, `TINYUSB_ROOT`
+- All backends: `flash_jlink`/`reset_jlink`, `flash_stlink`/`reset_stlink`,
+  `flash_stflash`/`reset_stflash`, `flash_openocd`/`reset_openocd`,
+  `flash_openocd_wch`/`reset_openocd_wch`, `flash_openocd_adi`/`reset_openocd_adi`,
+  `flash_wlink_rs`/`reset_wlink_rs`, `flash_esptool`/`reset_esptool`,
+  `flash_uniflash`/`reset_uniflash`, `flash_lm4flash`/`reset_lm4flash`
+- `find_firmware(variant, example)`
+- `get_serial_dev(id, vendor_str, product_str, ifnum)` — moves here (not hil_test) because
+  `flash_esptool` calls it; keeping it test-side would create a helper→hil_test import cycle.
+  Tests call `hil_flash.get_serial_dev`.
+- Module globals `build_dir = 'cmake-build'` and `verbose = False`, set by callers exactly as the
+  `hil_test` globals are today (`hil_test.main` sets them from argparse; pool_check sets them
+  directly). `run_cmd`'s verbose echo reads `hil_flash.verbose`.
+
+Dispatch in callers stays string-based: `getattr(hil_flash, f'flash_{flasher["name"].lower()}')`.
+
+## hil_test.py (what remains)
+
+Config TypedDicts (`Board`, `FlasherCfg`, …), device-node lookup except `get_serial_dev`
+(`get_disk_dev`, `get_hid_dev`, `get_alsa_capture_dev`, `open_serial_dev`, `serial_write_all`,
+`read_disk_file`, `open_mtp_dev`, `get_printer_dev`/`open_printer_dev`), enum-timeout globals +
+`wait_until`,
+`log_line`/print-lock, `compact_output`, all `test_*` functions, test lists, `test_example`,
+`build_board`, `test_board`, report rendering/accumulation, `main`. Call sites use explicit
+module-qualified names (`hil_lock.flash_permit(...)`, `hil_flash.run_cmd(...)`) so provenance is
+greppable; no `from … import *`-style mirroring.
+
+`init_worker` keeps its signature (Pool initargs unchanged) and forwards the scheduling state to
+`hil_lock.init_scheduling(...)`.
+
+## Consumer updates (same commit)
+
+- **`.claude/skills/hil/pool_check.py`** — drop its private `lock_board`/`unlock_board` in favor of
+  `hil_lock.flock_nb` + `write_record(fh, 'pool_check')` (+ `clear_record` on release; deliberately NOT `acquire_board_lock`, whose HIL_NO_BOARD_LOCK bypass and fail-open behavior pool_check must not inherit); import
+  flashers/`find_firmware`/`get_serial_dev`/`cmd_stdout_text`/`TINYUSB_ROOT`/`build_dir` from
+  `hil_flash`; `BOARD_LOCK_DIR` references move to `hil_lock`. pool_check then imports **only**
+  `hil_lock` + `hil_flash` (no `hil_test`), so its `pymtp` stub shim is deleted — that shim existed
+  solely because importing `hil_test` pulls in libmtp.
+- **`test/hil/hil_ci.sh`** — the scp list is currently `hil_test.py`, `pymtp.py`, `$CONFIG`; add
+  `hil_lock.py` and `hil_flash.py` (hil_test cannot even import without them). `board_lock.py` was
+  never in the list.
+- **Docs rename `board_lock.py` → `hil_lock.py`** (live docs only): `.claude/skills/hil/SKILL.md`,
+  `.claude/agents/hil-operator.md`, `.claude/agents/target-debugger.md`,
+  `.claude/skills/etm-trace/SKILL.md`, `.claude/skills/usb-kernel-recover/SKILL.md`,
+  `.claude/skills/target-debug/SKILL.md`. Historical `docs/superpowers/{plans,specs}` stay as
+  records.
+- **CI workflow** — untouched (invokes `hil_test.py` CLI only).
+
+## Verification
+
+1. `python3 -m py_compile` on all three modules + pool_check.
+2. `hil_lock.py hold/status/release` interplay: hold, conflicting hold, status listing, release,
+   protection of a `CI_REASON` record, stale-record cleanup.
+3. `pool_check.py --scan-only`, then a single flash board (e.g. `-b stm32f407disco`).
+4. Full `hil_test.py -b stm32f407disco -B examples tinyusb.json` on the rig; compare the report
+   row and log shape against a pre-refactor run.
+5. `pre-commit run` on all touched files.
+
+## Sequencing
+
+Lands on top of `claude/hil-pool-check`. After merge, fix the pool_check review findings as a
+separate change on the new module boundaries, and update agent-memory references to
+`board_lock.py`.