Breaking Changes

• Drop IE11 support (#4549, thanks @JoviDeCroock)
• Move defaultProps into preact/compat (#4657, thanks @JoviDeCroock)
• Remove automatic px suffix (#4665, thanks @JoviDeCroock)
• Remove contains with a simple parentNode check (#4666, thanks @JoviDeCroock)
• Remove component.base (#4549, thanks @JoviDeCroock)
• Remove SuspenseList (#4668, thanks @JoviDeCroock)
• Remove static dom bail (#4670, thanks @JoviDeCroock)
• Breaking changes to outputs & pkg.json (#4652, thanks @rschristian)
• Drop support for TS versions < 5.1 (#4788, thanks @rschristian)
• Remove all export maps in nested pkg.json files (#4784, thanks @rschristian)
• Remove deprecated 'ForwardFn' type from compat (#4777, thanks @rschristian)

Features

• Comment denoted hydration (#4636, thanks @JoviDeCroock)
• Forward ref by default (#4658, thanks @JoviDeCroock)
• Add captureOwnerStack (#4875, thanks @colinaaa)
• Add context argument to compat/Children map api (#3855, thanks @ParSal123)
• Export helper functions from preact/debug (#4830, thanks @colinaaa)
• Export test-utils from compat (#4783, thanks @rawrmonstar)

Types

• Require initial value in useRef (#4683, thanks @rschristian)
• Types w/ module augmentation (#4884, thanks @rschristian)
• Fix outdated public RefCallback type (#4801, thanks @developit)
• Export IntrinsicHTMLElements interface (#4885, thanks @edoardocavazza)
• Avoid breaking change for ARIA element types (#4882, thanks @rschristian)
• Move most interfaces out of the JSX namespace (#4878, thanks @rschristian)
• Make HTMLAttribute type declarations consistent (#4876, thanks @rschristian)
• Restrict aria roles by element type (#4607, thanks @rschristian)
• Add types for '/compat/server' & '/compat/scheduler' (#4835, thanks @rschristian)

Fixes

• Ensure memoized components re-render after errors (#4880, thanks @JoviDeCroock)
• Provide solution to long standing memleak (#4853, thanks @JoviDeCroock)
• Ensure we properly re-render bailing errored children (#4857, thanks @JoviDeCroock)
• Support alternative contentDocument (#4851, thanks @JoviDeCroock)
• Fix memory leak in VNode owner tracking (#4850, thanks @developit)
• Ensure 'compat/test-utils' exports match & are valid (#4834, thanks @rschristian)
• Fix signal attribute values not working with precompile transform (#4799, thanks @marvinhagemeister)
• Fix escape style object value in precompile transform (#4794, thanks @marvinhagemeister)
• Fix _listeners mangle to reduce collisions (#4463, thanks @rschristian)

Performance

• Do not re-insert memoized vnodes that keep their relative order after swap (#4888, thanks @vasylenkoval)
• Call tolowercase only when needed (#4881, thanks @JoviDeCroock)
• Reduce some repeated logic (#4814, thanks @43081j)
• Golf down suspense (#4855, thanks @JoviDeCroock)
• Add flags for component type (#4867, thanks @JoviDeCroock)

Refactors

• DOM event name casing (#4843, thanks @rschristian)
• Improve accuracy of non-dimensional regex (#4772, thanks @rschristian)
• Skip dom check for inferring lower-cased event names (#4720, thanks @rschristian)
• Prune portal logic (#4667, thanks @JoviDeCroock)
• Switch to Object.is for hook args (#4663, thanks @rschristian)
• Remove rerendercount (#4877, thanks @JoviDeCroock)

Testing & Development

• Bump testing/transpilation/formatting deps (#4858, thanks @JoviDeCroock)
• Upgrade oxlint to 1.8.0, fix errors (#4848, thanks @camc314)
• Add simple test for unstable_batchedUpdate to improve coverage (#4842, thanks @rschristian)
• Correct PR reporter filter for forks (#4828, thanks @rschristian)
• Remove sinon (#4820, thanks @43081j)
• Migrate compat tests to vitest spies (#4819, thanks @43081j)
• Migrate debug tests to vitest spies (#4817, thanks @43081j)
• Migrate hooks tests to vitest spies (#4816, thanks @43081j)
• Migrate lifecycle tests to use vitest spies (#4815, thanks @43081j)
• Migrate events/refs tests to vitest spies (#4813, thanks @43081j)
• Migrate more browser tests to use vitest spies (#4812, thanks @43081j)
• Migrate context tests to vitest spies (#4810, thanks @43081j)
• Migrate createContext test to use vitest spies (#4811, thanks @43081j)
• Migrate components tests to vitest spies (#4809, thanks @43081j)
• Use v8 coverage (#4807, thanks @43081j)
• Switch to playwright for browser tests (#4808, thanks @43081j)
• Migrate from mocha to vitest (#4806, thanks @43081j)
• Add test ensuring effects are cleaned up (#4792, thanks @JoviDeCroock)
• Avoid caching so file-saves work first try (#4786, thanks @JoviDeCroock)
• Bump browserslist (#4785, thanks @rschristian)
• Specify target browsers (#4773, thanks @rschristian)
• Remove extraneous pkg.json key (#4789, thanks @rschristian)
• Drop unused/broken test (#4653, thanks @rschristian)