Lower Expr.(n_)unique to group_by on streaming engine (#22420)
Chunk huge munmap calls (#22414)
Add single-key variants of streaming group_by (#22409)
Improve accumulate_dataframes_vertical performance (#22399)
Use optimize rolling_quantile with varying window sizes (#22353)
Dedicated rolling_skew kernel (#22333)
Call large munmap's in background thread (#22329)
New streaming group_by implementation (#22285)
Patch jemalloc to not purge huge allocs eagerly if we have background threads (#22318)
Turn on parallel=prefiltered by default for new streaming (#22190)

✨ Enhancements

When reporting unexpected types in errors, module-qualify the typename (#22390)
Add Series backward_fill / forward_fill (#22360)
Add GPU support to sink_* APIs (#20940)
Changed mapping type from dict to Mapping (#19400) (#19436)
Make streaming dispatch public (#22347)
Add rolling_kurtosis (#22335)
Support Cast in IO plugin predicates (#22317)
Add .sort(nulls_last=True) to booleans, categoricals and enums (#22300)
Add rolling min/max for temporals (#22271)
Support literal:list agg (#22249)
Support running Polars SQL queries against any objects implementing the PyCapsule interface (#22235)
Support implode + agg (#22230)
Dispatch scans to new-streaming by default (#22153)

🐞 Bug fixes

Ensure write_excel correctly preserves null values in nested dtype data on export (#22379)
Panic when visualizing streaming physical plan with joins (#22404)
Fix incorrect filter after LazyFrame.rename().select() (#22380)
Fix select(len()) performance regression (#22363)
Handle pytz named timezone in lit (#21785)
Don't leak state during prefill CSE cache (#22341)
Maintain float32 type in partitioned group-by (#22340)
Resolve streaming panic on multiple merge_sorted (#22205)
Fix ndjson nested types (#22325)
Fix nested datetypes in ndjson (#22321)
Check matching lengths for pl.corr (#22305)
Move type coercion for pl.duration to planner (#22304)
Check dtype to avoid panic with mixed types in min/max_horizontal (#21857)
Coalesce correct column for new streaming full join (#22301)
Don't collect NaN from Parquet Statistics (#22294)
Set revmap for empty AnyValue to Series (#22293)
Add an __all__ entry to internal type definition module (#22254)
Datetime parser was incorrectly parsing 8-digit fractional seconds when format specified to expect 9 (#22180)
More robust str → date conversion when reading from spreadsheet (#22276)
Deprecate using is_in with 2 equal types and mark as elementwise (#22178)
Duplicate key column name in streaming group_by due to CSE (#22280)
Raise ColumnNotFoundError for missing columns in join_where (#22268)
Parquet filters for logical types and operations (#22253)
Ensure floating-point accuracy in hist (#22245)
Check matching key datatypes for new streaming joins (#22247)
Incorrect length BinaryArray/ListBuilder (#22227)

📖 Documentation

Update docs for schema arg in scan_csv to match read_csv (#22357)
Update pl.when documentation (#22345)
Add missing is_business_day to documentation reference (#22338)
Improve interpolation documentation to clarify behavior of null values (#22274)

🛠️ Other improvements

Install pytorch for 3.13 on Windows (#22356)
Make interpolate fix more robust (#22421)
Fix interpolate test (#22417)
Reduce hot table size in debug mode (#22400)
Replace intrinsic with non-intrinsic (#22401)
Make streaming dispatch public (#22347)
Update rustc to 'nightly-2025-04-19' (#22342)
Update mozilla-actions/sccache-action (#22319)
Purge old parquet and scan code (#22226)
Add an __all__ entry to internal type definition module (#22254)
Add online skew/kurtosis algorithm for future use in rolling kernels (#22261)
Add Polars Cloud 0.0.7 release notes (#22223)
Change format name from list to implode (#22240)
Make other parallel parquet modes filter afterwards (#22228)
Close async reader issues (#22224)
Add BinaryArrayBuilder (#22225)

Thank you to all our contributors for making this release possible! @DavideCanton, @JakubValtar, @Jesse-Bakker, @MarcoGorelli, @NeejWeej, @Shoeboxam, @adamreeve, @alexander-beedie, @axellpadilla, @cmdlineluser, @coastalwhite, @d-reynol, @dongchao-1, @florian-klein, @kdn36, @math-hiyoko, @mcrumiller, @mroeschke, @nameexhaustion, @orlp, @ritchie46, @stijnherfst and @yiteng-guo