Fix water HTI MBAR bond-angle scaling

[njzjz-bot]

Summary:

• use reverse lambda scaling for bond_angle_off MBAR reduced potentials
• preserve forward scaling for angle_on and deep_on states
• add a focused regression test

Tests:

• PYTHONPATH=.. python -m unittest test_hti_water_gen_lammps_input.TestHtiWaterMbar -v
• python -m ruff check --select I,F --ignore F841 dpti/hti_water.py tests/test_hti_water_gen_lammps_input.py

Fixes #126

Coding agent: Codex
Codex version: codex-cli 0.149.0
Model: gpt-5.6-sol
Reasoning effort: xhigh

Summary by CodeRabbit

• Bug Fixes

  • Corrected water hydration calculations for the bond-angle removal step.
  • Ensured this step uses the appropriate reverse lambda scaling.

• Tests

  • Added regression coverage to verify correct scaling behavior for the bond-angle removal workflow.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a62c3001-f8be-43e0-9fc5-b0b3e090868b

📥 Commits

Reviewing files that changed from the base of the PR and between 78091bd and d23b7f7.

📒 Files selected for processing (2)

• dpti/hti_water.py
• tests/test_hti_water_gen_lammps_input.py

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

---

📝 Walkthrough

Walkthrough

The MBAR reduced-potential construction for water HTI now uses step-specific lambda scaling. The bond_angle_off path uses inverse-lambda scaling. A NumPy regression test verifies the corrected formula.

Changes

Water HTI MBAR correction

Layer / File(s)	Summary
Step-aware MBAR potential construction and regression coverage dpti/hti_water.py, tests/test_hti_water_gen_lammps_input.py	The new helper applies lambda scaling for angle_on and deep_on, inverse-lambda scaling for bond_angle_off, and rejects unknown steps. _post_tasks_mbar uses the helper. The test checks the bond_angle_off reduced potentials against expected values.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to d23b7

The PR corrects water MBAR bond-angle scaling while preserving existing scaling for other states and adds a focused regression test; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: yi-fanli

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the water HTI MBAR bond-angle scaling fix.
Linked Issues check	✅ Passed	The changes correct MBAR branch selection, apply reverse lambda scaling for bond_angle_off, and add a focused regression test for issue [#126].
Out of Scope Changes check	✅ Passed	The changes remain within the linked issue scope and include only the implementation fix and its regression test.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (78091bd) to head (d23b7f7).

Files with missing lines	Patch %	Lines
dpti/hti_water.py	0.00%	7 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##           devel    #154   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files         25      25           
  Lines       6665    6668    +3     
=====================================
- Misses      6665    6668    +3     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.