Ported new osu! PP & difficulty rework (2026.702.1 / osu-tools) — available for reference / review

Hello @MaxOhn,

I've (gemini) ported the latest osu! difficulty and performance rework (matching osu-tools / ppy.osu.Game.Rulesets.Osu version 2026.702.1) into a fork here: https://github.com/Raregendary/rosu-pp-gemini

I wanted to open this issue to let you know in case you'd like to inspect it, use it as a reference, or adapt parts of it.

What was done:

• New evaluators: Ported SnapAimEvaluator, FlowAimEvaluator, AgilityEvaluator, and ReadingEvaluator.
• Skills rewritten:
  • Aim: Updated with the new peak strain system and evaluator integration.
  • Speed: Updated with harmonic scale weighting and per-object difficulty tracking.
  • Reading: Added reading skill and attributes.
• Performance calculator: Integrated reading PP, cognition value, speed deviation, and estimated slider breaks.
• Formula & Star Rating updates: Updated the new star rating calculation and difficulty rating formulas.

Verification & Testing:

• All 217+ existing unit/gradual tests pass.
• Verified PP and difficulty outputs against C# PerformanceCalculator (osu-tools) across various real maps and mod combinations (both stable and lazer rulesets), matching within ±0.05 tolerance.
• Note on benchmarks: I have only verified numerical correctness and test passes; I haven't run comprehensive performance/allocation benchmarks yet.

Transparency Note:

This implementation was done with the assistance of an AI agent (Gemini 3.8) referencing the official C# osu! ruleset source. Since I wasn't sure what your policy is on AI-assisted contributions, I didn't want to open a direct PR without asking first.

Feel free to check out the branch, cherry-pick anything helpful or not :)

I have manually tested this and verified for osu standard with nm/hr/hd/cl modes, nothing else was tested by me.

The things we do so we don't have to use the c# library but have it natively in rust xD

Start by comparing the fork at https://github.com/Raregendary/rosu-pp-gemini with osu-tools / ppy.osu.Game.Rulesets.Osu version 2026.702.1, focusing on the listed evaluators, skills, performance calculator, and formula changes. Review the existing 217+ unit and gradual tests, then compare outputs against the C# PerformanceCalculator; completion would require deciding which ported parts to adapt and validating the stated tolerance across supported maps and mods.