# Drift Report

## Current Status

As of the current upstream baseline, no byte-level drift is allowed between
files listed in `tools/source-manifest.txt` and the matching files under
`../linuxcnc/`.

The enforced upstream baseline is:

```text
60597ee0718873d2449058c824262a275e5e4bad
```

`tools/verify_vendor_sync.sh` enforces this by comparing every manifest file
against upstream during native validation.

## Allowed Standalone Boundaries

The following differences are intentional runtime boundaries, not LinuxCNC
semantic rewrites:

| Boundary | Standalone treatment |
| --- | --- |
| RTAPI | Minimal compatibility shim in `runtime/core/shims/rtapi.h`. |
| HAL lookup | Standalone HAL adapter for `_hal[...]` named parameter reads. |
| INI lookup | Standalone INI adapter around vendored LinuxCNC INI parser behavior. |
| Canonical output | Canonical calls are captured as test events instead of driving hardware. |
| Python/remap | Python/remap hooks are stubbed at the runtime edge. |
| Dynamic interpreter path | `interp_base.cc` probe uses standalone `EMC2_HOME` compile-time path boundary. |
| Realtime scheduler | TP probes seed deterministic status/config data instead of running LinuxCNC realtime process topology. |
| Kinematics component lifecycle | `trivkins.c` and `5axiskins.c` are initialized through LinuxCNC module entry points while HAL component init/ready/exit, HAL pin allocation, and RTAPI module metadata are handled by standalone shims. |
| Browser storage | OPFS remains outside the native core and is not yet connected. |

## Enforced Non-Drift Rules

- Do not edit `../linuxcnc/`.
- Do not patch vendored files without adding a patch under `patches/` and
  documenting the reason.
- Do not add standalone `Interp::convert_g()`.
- Do not add `.c` or `.cc` manifest files without a source compile probe.
- Do not sync from a different upstream commit without updating
  `tools/upstream-baseline.txt` and `docs/scope-and-baseline.md`.

## Known Gaps

- No browser/WASM parity tests yet.
- No JS SDK validation yet.
- No OPFS persistence validation yet.
- Identity/trivial kinematics and LinuxCNC `5axiskins` now have native
  source-probe coverage; TRT `xyzac`/`xyzbc`, serial, delta, SCARA, and other
  machine-specific kinematics are not yet extracted.
- Full machine baselines beyond the current identity/trivial and `5axiskins`
  probes are not established.
- Fixture expectations are currently checked against the standalone vendored
  source path, not by running a native LinuxCNC binary for every fixture.

## Current Drift Conclusion

Within the native extracted-core scope, the port currently has no permitted
byte-level drift from vendored LinuxCNC source files. All current behavior
coverage is guarded by upstream baseline validation, vendor sync validation,
source compile probes, native harnesses, and fixture checks.