[Lohith248]

Summary

Empty selected state arrays crash joint_discontinuity and idle_fraction, or produce false stationary/frozen evidence in the trajectory and integrity checks. All five checks now return only their sample count and no intervals for these inputs.

- empty selected vector -> reduction error or fabricated state measurements
+ empty selected vector -> sample count only, no intervals

ROS JointState permits empty state arrays. Unlike #666's zero-message case, these channels contain messages but no components in the selected field. The patch adds one parametrized regression using real MCAP messages and updates the public docstrings.

Evidence

• Before: all five cases of tests/test_checks_nan_failopen.py::test_empty_position_vectors_withhold_motion_measurements fail against unmodified main at 6cf6e98.
  After: all five pass. A separate real-MCAP comparison confirms identical results for genuinely stationary positions across all five checks.
• uv run --locked pytest tests/test_checks_nan_failopen.py tests/test_checks.py -q: 107 passed.
• uv run --locked pytest -q -n 4 -rs: 2,557 passed, 8 skipped on Python 3.14.8. Skips require opt-in network access, MediaPipe/model assets, Docker, or a live bucket.
• uv run --python 3.11 --locked pytest tests/test_checks_nan_failopen.py -q: 9 passed on Python 3.11.17 in a separate environment.
• uv run --locked ruff check --fix, uv run --locked ruff format, and uv run --locked ty check: passed.

Validation used WSL Ubuntu 22.04, GCC 11.4.0, and verified FFmpeg/ffprobe 8.1 binaries on PATH.

Merge Danger

Door: two-way.

Reverting restores the previous check behavior without a data migration.

Blast Radius: checks.

Only selected arrays with no components take the new return paths. Public signatures, dependencies, schemas, and transform bytes are unchanged. Applications own their check versions; no transform behavior-version bump is needed.

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[github-actions]

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[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no actionable issues were found.

Summary

The PR makes five state checks withhold motion and integrity measurements when the selected arrays contain no components.

• State checks return counts when selected vectors are empty.

_{Reviews (1) · Last reviewed commit: "fix(checks): withhold state measurements..." · Reviewed by Greptile}

[kstonekuan]

LGTM, merging. Thanks for the fix.