\b does not fire between a digit and '_' because '_' is \w in RE2.
The pattern \bpsu?\s*([0-9]+)\b never matched PSU1_POWER_IN style
sensors, so parsePSUSDR (and PSUSlotsFromSDR / samplePSUPower) returned
empty results for MSI servers — causing all power graphs to fall back
to DCMI which reports ~half actual draw.
Added an explicit underscore-terminated pattern first in the list and
tests covering the MSI format.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
