2026-09-16: superseded in part by hil-farm.md — both design rounds folded this move into the HIL farm extraction (rtt.py becomes the farm skill's console layer); the loader/pin design below is kept only as reference.
Deferred from the 2026-09-15 migration of the rtt skill to agentrc. The skill (text, board notes, CLI and tests) now lives in agentrc; tools/rtt.py stays here as a byte-identical copy because the HIL harness imports its classes.
test/hil/helper/hil_util.py loads tools/rtt.py by path at import time and re-exports JlinkRtt, OpenocdRtt, RttError, strip_banner, RTT_BANNER_RE; hil_test.py opens JlinkRtt as the console of a board with "logger": "rtt" (only ea4088_quickstart in tinyusb.json).tools/ci_select.py imports hil_util on GitHub-hosted ubuntu-latest runners (build.yml path-selection jobs), so the file must be present there today.hil_ci.sh stages tools/rtt.py next to test/hil; build.yml's path filter and the pre-commit hil-test pattern name the file; test_hil_rtt.py asserts the staging line and keeps the harness-side contracts only.skills/rtt/scripts/rtt.py is identical; tests/test_rtt.py there holds the class and CLI tests. Two copies drift unless one goes.hil_util: load the module lazily, inside the console factory and strip_banner, from HIL_RTT_PY (default ~/.claude/skills/rtt/scripts/rtt.py), registered in sys.modules so RttError still pickles across the fork pool; the ImportError names the resolved path, the variable and the install command. ci_select then never touches it.tools/rtt.py; drop the hil_ci.sh staging line, the build.yml path filter entry, the pre-commit pattern and the staging assertion.test_hil_rtt.py: loader tests against a stub module (default path, override, missing-install diagnostic, console-factory wiring); nothing that needs the real implementation, so pre-commit stays agentrc-free.tusb from a persistent clone (install.py install --skill), after telling hifiphile, whose local HIL runs then need it. Then a real hil_test.py run on ea4088_quickstart on each rig before this lands.A tinyusb revision stops pinning its console implementation: what runs on a rig is whatever ~/.claude/skills/rtt holds that day, so a harness regression cannot be bisected in this repository alone. Vendoring a pinned copy synced from agentrc is the alternative if that matters more than one source of truth.