[wangyinz]

Reusing the Prieto MTPowerSpectrumEngine with a slightly different window length raised ValueError and could make broadband_snr_QC discard otherwise valid data. Resize the operator and rebuild its length-specific tapers, retaining a sufficiently large explicit FFT size or selecting an automatic size when necessary. Failed numerical construction preserves the previous cached state.

Regression coverage checks all three input types, repeated length changes against freshly constructed engines, FFT sizing, invalid inputs, and broadband SNR using the existing waveform fixture. Native tests verify that the C++ TimeSeries overload pads/truncates while its vector overload remains strict.

Validation: 24 targeted tests passed with the real Prieto numerical backend. Black 25.1.0 and static syntax checks passed. GitHub Actions rebuilt the current native code and passed the complete test suite on Python 3.10 and 3.13, including the native-length behavior and broadband SNR regressions. CMake, Docker, formatting, static, and dependency checks also passed.

Fixes #1044.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.28%. Comparing base (ecfed17) to head (db34f1b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1055      +/-   ##
==========================================
+ Coverage   75.19%   75.28%   +0.08%     
==========================================
  Files         185      185              
  Lines       38176    38185       +9     
  Branches     2587     2587              
==========================================
+ Hits        28706    28746      +40     
+ Misses       8544     8516      -28     
+ Partials      926      923       -3     

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[pavlis]

This looks like a pretty straightforward fix. The new tests it adds indicate it solves the problem.