This is the release note of v4.3.0.

Highlights

This has various bug fixes and improvements to the documentation and more.

Breaking Changes

[fix] lgbm 4.6.0 compatibility (optuna/optuna-integration#207, thanks @ffineis!)

Accept custom objective in LightGBMTuner (optuna/optuna-integration#203, thanks @sawa3030!)
Improve time complexity of IntersectionSearchSpace (#5982, thanks @GittyHarsha!)
Add _prev_waiting_trial_number in InMemoryStorage to improve the efficiency of _pop_waiting_trial_id (#5993, thanks @sawa3030!)
Add arguments of versions to convert_positional_args (#6009, thanks @fusawa-yugo!)
Add wait_server_ready method in GrpcStorageProxy (#6010, thanks @hitsgub!)
Remove warning messages for Matplotlib-based plot_contour and plot_rank (#6011)
Fix type checking in optuna._callbacks.py (#6030)
Enhance SBXCrossover (#6008, thanks @hrntsm!)

Convert storage into InMemoryStorage before copying to the local (optuna/optuna-integration#213)
Fix contour plot of matplotlib (#5892, thanks @fusawa-yugo!)
Fix threading lock logic (#5922)
Use _LazyImport for grpcio package (#5954)
Prevent Lock Blocking by Adding Timeout to JournalStorage (#5971, thanks @sawa3030!)
Fix a minor bug in GPSampler for objective that returns inf (#5995)
Fix a bug that a gRPC server doesn't work with JournalStorage (#6004, thanks @fusawa-yugo!)
Fix _pop_waiting_trial_id for finished trial (#6012)
Resolve the issue where BruteForceSampler fails to suggest all combinations (#5893)

Follow recent changes in optuna/optuna's document sphinx config (optuna/optuna-integration#197)
Fix links to external modules (optuna/optuna-integration#198)
Update CONTRIBUTING.md (optuna/optuna-integration#200, thanks @sawa3030!)
Update comment in .readthedocs.yml (#5976)
Add comments on the reproducibility of HyperBandPruner (#6018)

[hotfix] Add the version constraint on dask (optuna/optuna-examples#296)
[hotfix] Add the version constraint on dask for dask-ml (optuna/optuna-examples#297)
Extends execution span of hiplot and sklearn (optuna/optuna-examples#298, thanks @fusawa-yugo!)
Apply black to fix CI (optuna/optuna-examples#300)
Bump up to 3.12 for CI (optuna/optuna-examples#301)
[hotfix] Add the version constraint on lightgbm (optuna/optuna-examples#302)
Fix Skorch Example (optuna/optuna-examples#303, thanks @ParagEkbote!)
Add version constraint for tensorflow-related CI (optuna/optuna-examples#304)
Temporarily skip Python 3.9 in fastai example (optuna/optuna-examples#308)
Run the skorch example in the CI (optuna/optuna-examples#309)
Fix fastai Example (optuna/optuna-examples#312)

Add BaseGASampler (#5864)
Fix comments in pyproject.toml (#5972)
Remove FirstTrialOnlyRandomSampler (#5973, thanks @mehakmander11!)
Remove _check_and_set_param_distribution (#5975, thanks @siddydutta!)
Remove testing/distributions.py (#5977, thanks @mehakmander11!)
Remove _StudyInfo's param_distribution in _cached_storage.py (#5978, thanks @tarunprabhu11!)
Introduce UpdateFinishedTrialError to raise an error when attempting to modify a finished trial (#6001, thanks @sawa3030!)
Deprecate consider_prior in TPESampler (#6005, thanks @sawa3030!)
Improve Code Readability by Following PEP8 Standards (#6006, thanks @sawa3030!)
Made error message for create_study's direction easier to understand optuna.study (#6021, thanks @sinano1107!)

Hotfix ci (optuna/optuna-integration#199)
Add flake8 in CI (optuna/optuna-integration#201, thanks @sawa3030!)
Remove test cases that uses UnsupportedDistribution (optuna/optuna-integration#208)
Fix a mypy error when using numpy>=2.2.4 (optuna/optuna-integration#212)
Fix a bug of lightgbm tuner for Python 3.8 users (optuna/optuna-integration#214)
Add a version constraint on xgboost (optuna/optuna-integration#217)
Run (optuna/optuna-integration#218)
Ensure gRPC server readiness before proceeding to prevent test failures (#5938, thanks @sawa3030!)
Apply black to fix CI (#5952)
Add workflow_dispatch trigger to all the CI (#6019)
Fix CI (#6026)

This release was made possible by the authors and the people who participated in the reviews and discussions.