Deprecate passing time_unit=None to Datetime constructor (#14708)
Rename Expr.meta.write_json/Expr.from_json to Expr.meta.serialize/Expr.deserialize (#14490)
Deprecate default value for ignore_nulls for ewm methods (#14663)
Deprecate DataFrame/LazyFrame.approx_n_unique (#14594)

🚀 Performance improvements

2-3x speedup in creating literals/Series of type Date (#14716)
fix accidental quadratic utf8 validation in parquet (#14705)
Add __slots__ to most Polars classes (#13236)
fast path for COUNT(*) queries (#14574)
Elide the total order wrapper for non-(float/option) types (#14648)
add utf8-validation fast paths for utf8view (#14644)
don't reassign chunks back to df owner (#14633)
If there are many small chunks in write_parquet(), convert to a single chunk (#14484) (#14487)
Polars thread pool was not used properly in various functions (#14583)

✨ Enhancements

Change default for maximum number of Series items printed to 10 to match DataFrame (#14703)
Change default number of rows printed in Notebooks for DataFrame/Series to 10 (#14536)
Infer values columns in DataFrame.pivot when values is None (#14477)
fast path for COUNT(*) queries (#14574)
let rolling accept index_column of type UInt32 or UInt64 (#14669)
Treat float -0.0 == 0.0 and -NaN == NaN in group-by, joins and unique (#14617)
Improve consistency of dtype inference from Python types (#14600)
Properly cache object-stores (#14598)

🐞 Bug fixes

Fix parallel strategy for LazyFrame not being applied (#14696)
Block slice pushdown past non-literal projections or when the projection doesn't contain any columns from the input (#14684)
Fix number of rows printed in DataFrame/Series repr (edge cases) (#14548)
Fix contention panics in file gc threads (#14690)
Fix feature combination (#14688)
Only push predicates depending on the subset columns past unique() (#14668)
Properly handle a single empty RecordBatch in from_arrow (#14683)
More accurate type hints for binary file-like inputs (#14674)
Reading RLE_DICTIONARY-encoded parquet incorrectly coalesced NULL to empty string in some cases (#14670)
use correct flooring division/modulo operator in literal optimizer and const_lhs <> series ops (#14671)
Enable is_in for string in categorical/enum (#14576)
Fixes a read_database issue loading specific datetime types from SQL Server backends (#14627)
Polars thread pool was not used properly in various functions (#14583)

📖 Documentation

Improve some DataType docstrings (#14719)
Fix bad link due to boldness in pl.count (#14691)
Improve docstrings for ewm_* and rolling_* methods (#14667)
Improve examples for Series.binary.encode and Series.binary.decode. (#14579)
Add examples for Series.kurtosis (#14681)
Fix docstring for LazyGroupBy.len (#14661)
Separate "writing a plugin" from "registering an expression" in user guide, add some extra links, don't use deprecated _register_plugin (#14621)
Fix code block path for group by example in getting started guide (#14612)
Add missing 'string' column in reading-writing Rust example to match Python example (#14597)

📦 Build system

Limit CMake threads to fix crash compiling libz-ng-sys on macOS (#14715)

🛠️ Other improvements

Limit CMake threads to fix crash compiling libz-ng-sys on macOS (#14715)
Fix make requirements when conda environment is active (#14693)
update rustc (#14678)
redundant imports all crates (#14662)
Avoid unnecessary cast in Series constructor (#14650)
Add test on selecting Enum columns (#14628)
Use uv for make requirements (#14618)
Rename coverage file (#14607)
Add a lint-only Makefile option (#14602)
No longer use SeriesView in Series.to_numpy (#14588)

Thank you to all our contributors for making this release possible! @Kylea650, @MarcoGorelli, @Object905, @alexander-beedie, @bsubei, @c-peters, @eLVas, @itamarst, @mbuhidar, @mcrumiller, @nameexhaustion, @orlp, @rijkvp, @ritchie46 and @stinodego