Highlights of the release

• Support for JDK 26 #24430
• Multiple coverage improvement to make it on par with Scala 2 support including // $COVERAGE-OFF$ and // $COVERAGE-ON$ markers.
• New @uncheckedOverride annotation for definitions that may override. #24545
• Trap Ctrl-C in the REPL: if no command is running clear the prompt, if some command is running ask for confirmation before exiting. #24127
• Numerous linting and presentation compiler improvements and fixes.
• New '-Yfuture-lazy-vals' options that allows to compile with new lazy val implementation compatible with all JDK 9+ #637

Other changes and fixes

Access modifiers

• Check protected parent constructor accesses only occurs in child constructors #25511
• Fix protected constructor access #25523

Annotations

• Improve ref check of constructors #24342
• Also copy param annots at mixin #24916
• Named arg may be deprecatedName #21588
• Fix: emit deprecation warnings when a symbol is annotated by a deprecated annotation #23906
• Fix [#20063]: Java leading annotation parsing #25503
• Accommodate adapted Scala 2 annotation value #17516
• Regression test for [#3403] #25521
• Fix: do not allow @targetName on primary constructor too #24682
• Add @uncheckedOverride annotation for definitions that may override #24545

Backend

• Chore: add regression test for [#4528] #24663
• Cast inline call results to result type, not method type #25111
• Regression tests for [#25] #25536
• Enforce JVM UTF-8 string limits in the backend #25300
• Do not simplify isInstanceOf if unrelated types might be subtypes at run-time #25535
• Adjust purity of trait with lazy member #23788
• Use Objects.equals in translating == #25314
• Fix generic signatures for mixin forwarders conflicting type parameter names #24567
• No mixin forwarder when ancestor is sealed #23482
• Simplify JVM interface list emission, remove a mini-phase #25203
• Chore: optimize lazy val with power of two #22428
• Fix infinite loop with bad section ends in TastyHeaderUnpickler #25676
• Fix TastyPrinter's JAR-walking logic to include subdirectories #25678

Classpath

• Skip module-info.class files during REPL tab-completion #24838
• Fix for [#22461] Empty ClassPath attribute in one or more classpath jars causes crash #22462

Coverage

• Make coverage more similar to the one in Scala 2 #23722
• Fix [#25555]: Preserve singleton precision during scoverage lifting #25556
• Fixes [#25482]: Ensure package transformation properly handles language imports in InstrumentCoverage #25546
• Bugfix: Fix issues with Scala JS and coverage #24769
• Make coverage support incremental compilation #24773
• Add support for local coverage on and off with // $COVERAGE-OFF$ and // $COVERAGE-ON$ #24486
• Improvement: Try to optimize coverage phase #24925
• Scoverage: do not instrument erased values #25298

Default parameters

• Fix named arguments evaluation order with by-name parameters #25161

Documentation

• Docs: Enforce links checks in the generated docs #25425
• Improve the contributing guide #25384
• Extend copyright into 2026 #24927
• Update README: This is Scala 3 #25424
• Explain implicit vs default args #25311
• Fix some scaladoc in compiler #24166
• Docs: fix task name for scaladoc/testOnly #23678
• Replace internal tab char in comment in Synthesizer.scala #23691

Enums

• Fix Java enum forwarders to pull from companion on initialization #24361
• Make enum apply ascriptions inferred types #25562

Exports

• Fix: look at the underlying of a TermRef for a getter #24565

Extension Methods

• Accept using right associative parameters #24766
• Add ctor proxies before exports #24884
• Fix pkg obj prefix of opaque tp ext meth #21527
• Better handling of illegal trees in extension #25368
• Fix LiftToAnchors for higher-kinded type applications #23672
• Prevent crash when extension not found #18830

GADTs

• Also trust TypeTest when there is a Bind #24568

Implicits

• Only check seen for LazyRef for TypeSizeAccumulator #20459
• Chore: add regression test for [#8581] #24666
• Fix "Regression in zio/zio-schema for typer/implicit resolution" #24156
• Fix implicit scope liftToAnchors for parameter lower bounds #23679

Inference

• Tweak type for tryParameterless #24716

Initialization

• Refine parameter adaptation logic for arrays #23591

Infrastructure

• Tweak tests to not fail under jdk 25 #25148
• Bump actions/upload-artifact from 6 to 7 #25423
• Bump actions/download-artifact from 7 to 8 #25420
• Bump VirtusLab/scala-cli-setup from 1.12.2 to 1.12.3 #25422
• Bump coursier/cache-action from 7 to 8 #25220
• Bump actions/upload-artifact from 5 to 6 #24758
• Bump actions/download-artifact from 6 to 7 #24759
• Bump actions/checkout from 5 to 6 #24517
• Bump actions/upload-artifact from 4 to 5 #24268
• Bump actions/download-artifact from 5 to 6 #24271
• Bump actions/download-artifact from 4 to 5 #23711
• Bump actions/checkout from 4 to 5 #23710
• Chore: bump sbt to 1.11.5 #23805
• Chore(deps): bump actions/setup-java from 4 to 5 #23812
• Chore: Use numberOfWorkers instead #24338
• Improvement: Additional way of defining ENABLE_BSP_ALL_PROJECTS #24122
• Formatting: Format presentation-compiler with scalafmt #24977
• Ensure mistakes in CI inputs are caught early #25677

Inline

• Chore: add regression test for [#22575] #25337
• Ensure the inline match scrutinee type conforms to the recalculated type #24988
• Make containsOuterRefsAnywhere follow aliases #25214
• Find annotation args in inline expansion #24895
• Chore: add regression test for [#10343] #24668
• Improve the test for creating protected method accessors for inlines #25865
• Do not update Symbol defTrees when retyping after Inlining #23870
• Prevent opaque types leaking from transparent inline methods #23792
• Chore: add regression test for [#8194] #24655
• Also substitute symbols in case bindings symbols #24849
• Inlines: decide sealing against original target, while using widened type as cast destination #25448
• Fix inline match on blocks with multiple statements #20125

JDK

• Skip over JEP 445 compact compilation units #23247
• Handle MissingType during Erasure phase #24817
• Don't generate bridge methods for inaccessible Java package-private methods #25166
• Fix isJvmAccessible to handle nested protected Java classes #24625
• Upgrade ASM to 9.9 for JDK 26 support #24430
• Fix java record varargs field accessor #24172
• Do not overwrite the supertype of non-trait super in Erasure #26081

Linting

• Fix false unused import warning for given CanEqual in pattern matching #25231
• Move second CheckUnused after pattern matcher #25114
• Extension check handles hiBound of opaque type #25172
• Unused lint ignores args to ctor of enclosing class #24768
• Parameter name can be masked in import #24635
• CheckUnused examines type of Apply #24465
• Check for synthetic case methods in unused lint #24239
• Lint avoids revisiting Inlined.call #24277
• Register no elements for lint after inlining #24279
• Ignore warnings when compiletime.testing is imported #24036
• Unused lint does not rewrite suppressed warnings #24055
• Drill through type lambda for tree symbol #23699
• Invent given pattern name in for comprehension #23121
• Check inline expansion for exclusion #23019
• Unused var message mentions unread or unset #23719
• Warn unused masking imports, remove obsolete unused options #23757
• Distrust tree pos for patvar lint #25043
• Match apply in PolyFunction for override #25505
• Value discard checks inline call for exemption #25554
• Lint enum case in outer context #24652
• Preserve select of exported member in newExpr #24570
• Always traverse Inlined.call in linter #24043
• Lint function arrow intended context function #23847
• Use enclosing enclosingInlineds for empty call #24281
• Exclude synthetic opaque proxy from lint #24264
• Regression test locals #25433
• Augment regression test #24327

Match Types

• Fix regression: Prioritize tree type over proto type when typing Binds #24175

Metaprogramming

• Warn about encoded pkg obj names #22707
• Bugfix: Fix possible SuspendException thrown when using macros #24174

Nullability

• Patch to allow interop with XMLBuilder and -Yexplicit-nulls #25221
• Add jspecify NonNull annotation to NotNullAnnots list #24487
• Add quick fix to add .nn #23598

Opaque Types

• Preserve insertion order when balancing And/OrType #25361
• Treat synthetic casts as pure #25126
• Make opaque types decomposable #24068

Overloading

• Pretype args before skipping clause of overloaded application #23012
• Fix varargs overload resolution with wildcard types #24669
• Fix wildcardArgOK for mixed wildcard/concrete type args #25001
• Regression test [#16004] #24086
• Tweak tryParameterless to use readapt #24078
• Fix override checking for Java methods with covariant array #24408
• Prefer non-extension to extension #24943
• Fix class super-call invokespecial owner #25437

Parser

• Accept primitive.class in annotations #25363
• End of new expr never shrinks #25253
• Permit new with trivial end #24331
• Improve message for nested package missing braces #23816
• Check seen for TypeParamRef in TypeSizeAccumulator #25264
• Observe outdent also for type cases and type blocks in quotes #25519
• Fix: import resolution for Java #25537
• Error tree on outdent is zero extent #23796
• Don't automatically insert OUTDENT before COMMA #25501
• Fix: allow postfix setters under language.postfixOps #23775
• Additional regression tests #25506
• Context bound always has a span #25809
• Don't pop outermost region when skipping #25738

Pattern Matching

• Emit unchecked warnings for trait patterns #24962
• Fix false exhaustivity warning for seq match #23968
• Call inhabited for AppliedType recursively #23964
• Fix Ycheck crash from singleton tuple selects after specialization #25331
• Fix false unreachable case warning #23800
• Use upper bound of abstract types in exhaustivity checking #23909
• Extend caching in the space engine beyond local context #23483
• Prevent from getting children in case of non-sealed private #25359
• Use MatchCaseUnreachable #24829
• Preserve singleton types for final val aliases to Java enum constants #24980
• Try expanding case class to the product of its fields #25454
• Never widen constant type on selector type in matches #25197

Pickling

• Fix [#24456]: Cleanup the info of a Bind symbol in posttyper #24490
• Fix [#24207]: Cleanup the type of UnApply trees in posttyper #24259
• Chore: add a regression test for [#15786] #24658
• Don't absolutize sources outside of the sourceroot in TASTy #25429

Positions

• Preserve span of this during statification of trait constructors #25354
• Compute the right span for abstract error messages #23853
• Use a better span for an anonymous class #24640

Presentation Compiler

• Improvement: Use method type if it's available #25641
• Bugfix: Don't add square braces in context bounds #25798
• Bugfix: Fix issue with empty name throwing exceptions #25752
• Bugfix: Fix wrong type in InferredType code action #25469
• Bugfix: Fix issues in presentation compiler when using Scala JS #25450
• Improvement: Add fallbacks in non critical places for presentation compiler #25483
• Fix & feat: improvements in selection ranges #25290
• Feat(pc): add closing labels inlay hints #25178
• Bugfix: remove stale top-level symbols between runs #25317
• Bugfix: Fix various minor presentation compiler issues #25256
• Fix: ignore implicit apply for signature help #25294
• Fix incorrect XRay hint #24738
• Presentation compiler: propagate isDebug timeout check to all tests #25068
• Handle inlined tree in implicit parameter inlay hints #24762
• Create extension method in infer method action #24721
• Fix opaque types displayed as Nothing & Any in hover and signature help #24921
• Fix negative activeParameter in signature help #24945
• Closes [#7532]: Parameter hints not working for functions #23854
• Improvement: Allow passing -explain to the presentation compiler #24740
• Exclude XRayModeHint for synthetics #24722
• Add unsafe RawPresentationCompiler implementation #24133
• Bugfix: Make sure that we can query tree.source #24123
• Improvement: additional completions for using clause #23647
• Inlining interpolated variables #25144
• Bugfix: inline value false-positive shadowing with lambda params #25140
• Fix issue with pc breaking in requiredMethod on newly overloaded valueOf #23708
• Pc: completions - do not add [] for ... derives TC@@ #23811
• Porting XRayModeHints #23891
• Improve symbol order in completions provided by the presentation compiler #23888
• Bugfix: Fix issues with Scala JS and the presentation compiler #25550
• Bugfix: Show hover on derives clause #25804
• Improvement: improve perfomance of the presentation compiler #25769
• Coursier dependency imports should have lexicographic ordering #21592
• feature: Improve the logical sources provider (#26079)
• feature: Add logical package parsing for sourcepath (#25446)

Quotes

• Fix crashing for context bound type variables in quoted patterns #25286
• Fix [#25208]: handle AndType(TermRef, TypeRef) in TreeUnpickler path trees #25209
• Remove redundant mapOver in fixThisTypeModuleClassReferences #25440
• Make typeArgs in QuotesImpl work for AnnotatedTypes #24018
• Improve LambdaTypes handling in Quotes reflect memberType #25786
• Backport "Don't lookahead from interpolation" to 3.3 LTS (#25834)

Reflection

• Fix Select.copy in reflect API losing DerivedName for default getters #25269
• Do not expose ClassInfo in memberType in reflect API #24922
• Quotes reflect: Allow to return DefDef from a val symbol tree #22603

Reporting

• Force conditional warnings when configured #25552
• Use deprecatedOverriding message #25439
• Fix [#24711]: Use dot notation for Java nested types in error messages #24919
• Enhance WInferUnion to not warn propagated explicit union types #25280
• Fixes [#24233]: Remove misleading JDK compatibility hint for TASTy errors #25171
• More descriptive "not found" message when type/term exists with the expected term/type name #24959
• Mention named givens in double def explainer #23833
• Do not discard amended format when f-interpolator warns #23697
• Use dollar-free param names in stub implementations #25646
• Error mentions bad _1 selector #25616
• Add ErrorMessageID to -Winfer-union warnings (#25073) #25249
• Addendum when apply error involves default arg #21133
• Warn on Scala 2 auto-apply if loosely nullary #24811
• Forward reference error includes line numbers #22534
• Use other tree for actual symbol of Assign #22869
• Add "did you mean to use parentheses/a block" when finding a complex expression on the RHS of an infix operator #25099
• Fix printing references to nested objects #25086
• Add error note for type mismatch involving blocks without last expression #25181
• Don't suggest invisible members of root imports #24999
• Improve multi-line code message rendering #24723
• Warn if type argument was inferred as union type #24258
• Improve printing of strings #22945
• Better error message: reassignment to val #24184
• Add addendum to private val parameter variance error message #23876
• Regression tests #24876

REPL

• Make REPL type echo-ing use partially qualified names where made possible by imports #24850
• Remove pipes from multi-line REPL prompts #24307
• Fix "Colon as operator part at beginning of line in REPL" #24942
• Trap Ctrl-C in the REPL: if no command is running clear the prompt, if some command is running ask for confirmation before exiting #24127

Rewrites

• Deduplicate patches before applying them to sources #24215

Runner

• Fix for [#22443]: prevent stty from being called when not running in a terminal #22444

Scaladoc

• Do not hide when a class or a trait extends Any #25403
• Ability to hide snippets from the documentation #25411
• Use <sup> tags for exponents in Scaladoc comments #25645
• Fix duplicate member entries in Scaladoc generation #24712
• Scaladoc Overload Method Link Fix #25156
• Init MacroClassLoader in scaladoc #25141
• Scaladoc: Take title from sidebar.yml into account #18997
• [scaladoc] Allow to additional scalacOptions in Markdown code snippets #24755
• Fetch the right kind for synthesised definitions #25405
• Add the transparent flag to java.lang.Object #25394
• Parse HTML properly in Scaladoc #25681

SemanticDB

• Add context parameters to SemanticDB synthetics #23381
• Better refinement symbols in semanticDB #18604
• Encapsulate SemanticDB package, unify symbol and document printing #25084

Testing

• Fix line and path separators in test #23534
• Fix: update checkfile for i23905 #24064

Testing framework

• Reject check file match with stack trace #22389
• Cleanup compiler test. remove unnecessary isJavaAtLeast conditions #24589
• Bugfix: Don't run coverage tests in testCompilation without --coverage flag #24932
• Cleaner, quieter test rig tests #24073
• Skip tests with no sources such as .scala-build dir #25173
• Report info logs in checked test output if enabled with -Ylog #25391
• Bugfix: Fix flaky test in ScalaJSCompletionsSuite #25539
• Add regression test for [#23195] #24853
• Test hover on backticked identifiers with whitespace #25142

Transform

• Check extension method at typer #24199
• Always encode <init> in derived name #23478
• Fix "Scala 3.8.3 compiling covariant overrides with separate compilation causes AbstractMethodError at runtime" #25659
• Make Phase.run protected #25366

Tuples

• Fix inconsistent typeSize calculation for TupleN vs recursive pair encodings #24743
• Fix: make vals created in desugaring of n-ary lambdas non-synthetic #23896
• Normalize tuple types when typing patterns #25335
• Fix [#24997]: Avoid unnecessary CHECKCAST in untupled function parameters #25085

Typeclass Derivation

• Fix [#23043]: spurious package conflict from non-class directories #25441
• Also checkRefinement for Singleton mirror #24080

Typer

• Use TypeComparer.constValue in TypeEval #24718
• Fix crash in Selectable unapply with custom applyDynamic #24343
• Prevent crash in SAM conversion with mismatched arity #23877
• Detect InsertedApply on Apply to break synthetic apply loops, not just Select #25463
• Typer: remove by-name lifting and replace default-getter args with fresh syms #25502
• Refine isEffectivelyFinal to avoid no-owner crash #23675
• Do not generate access proxies for locally defined protected defs #25056
• Use dealiasKeepRefiningAnnots in AvoidMap #25609
• Fix [#24573]: Add stricter checks for platform SAM compatibility #24624
• Make isExactlyNothing and isExactlyAny work for And/OrTypes #24016
• Handle assertion error in TyperState #23665
• Fix: correctly require a ClassTag when building a multidimensional Array #23902
• Fix crash when processing path dependent context functions using HKTs #25530
• Regression test #24820
• Chore: add regression test for [#13889] #24657
• Handle assertion error in TyperState #23665

XML

• Use toVector for XML literal sequences #23221

Union types

• Dealias in isSimpleThrowable check #24744