Symfony 6.4.0-BETA1 has just been released.
Here is the list of the most important changes since 6.3:

feature #51847 [AssetMapper] Allowing for files to be written to some non-local location (@weaverryan)
feature #52079 [HttpKernel] Add parameters kernel.runtime_mode and kernel.runtime_mode.*, all set from env var APP_RUNTIME_MODE (@nicolas-grekas)
feature #51348 [FrameworkBundle][Validator] Allow implementing validation groups provider outside DTOs (Yonel Ceruto)
feature #51577 [Notifier][Novu] Implement overrides (@wouter-toppy)
feature #51211 [Workflow] List place and transition listeners in profiler (@lyrixx)
feature #51220 [Workflow] Add a TraceableWorkflow (@lyrixx)
feature #52120 [AssetMapper] Split ImportmapManager into 2 (@weaverryan)
feature #51849 [AssetMapper] Warn of missing or incompat dependencies (@weaverryan)
feature #52032 [FrameworkBundle][Routing][Translation][Workflow] Move some compiler passes from FrameworkBundle to components (@fancyweb)
feature #52166 [HtmlSanitizer] Add support for sanitizing unlimited length of HTML document (@lyrixx)
feature #48095 [Messenger] [Sqs] Add AddFifoStamp middleware (@tyx)
feature #52160 [DoctrineBridge] Change argument $lastUsed of DoctrineTokenProvider::updateToken() to accept DateTimeInterface (@nicolas-grekas)
feature #52140 [Translation] Add argument $buildDir to DataCollectorTranslator::warmUp() (@nicolas-grekas)
feature #52047 [HttpFoundation][Runtime] Add $flush parameter to Response::send() (@fancyweb)
feature #51470 [FrameworkBundle][Serializer] Deprecate annotations (@alexandre-daubois)
feature #51483 [FrameworkBundle][Routing] Deprecate annotations (@alexandre-daubois)
feature #47416 [Console][FrameworkBundle][HttpKernel][WebProfilerBundle] Enable profiling commands (@HeahDude)
feature #50391 [FrameworkBundle][HttpKernel] Introduce $buildDir argument to WarmableInterface::warmup to warm read-only artefacts in build_dir (@Okhoshi)
feature #52087 [Scheduler] Add FailureEvent (@alli83)
feature #51828 [AssetMapper] Put importmap in polyfill so it can be hosted locally easily (@weaverryan)
feature #52024 [AssetMapper] Add a „package specifier“ to importmap in case import name != package+path (@weaverryan)
feature #50734 [ErrorHandler] Improve fileLinkFormat handling (@nlemoine)
feature #52002 [HttpFoundation] Cookies Having Independent Partitioned State (CHIPS) (@fabricecw)
feature #51805 [Scheduler] pre_run and post_run events (@alli83)
feature #51926 [Mime] Forbid messages that are generators to be used more than once (@fabpot)
feature #50946 [Routing][SecurityBundle] Add LogoutRouteLoader (@MatTheCat)
feature #52038 [Console] Dispatch ConsoleTerminateEvent when exiting on signal (@HeahDude)
feature #49893 [Serializer] Add XmlEncoder::CDATA_WRAPPING context option (@AndoniLarz)
feature #50877 [Finder] Add early directory prunning filter support (@mvorisek)
feature #51829 [AssetMapper] Automatically preload CSS files if WebLink available (@weaverryan)
feature #51011 [FrameworkBundle] Add parameters deprecations to the output of debug:container command (@HeahDude)
feature #51888 [WebProfiler] Profiler improvements / extract Font from stylesheet (@smnandre)
feature #51058 [FrameworkBundle] Add –exclude option to the cache:pool:clear command (@MatTheCat)
feature #51845 [AssetMapper] Add outdated command (Maelan LE BORGNE)
feature #51976 [Workflow] Revert deprecation about Registry (@lyrixx)
feature #50537 [Console] Add placeholders to ProgressBar for exact times (@maxbeckers)
feature #51717 [Notifier] [Telegram] Extend options for location, document, audio, video, venue, photo, animation, sticker & contact (@igrizzli)
feature #49044 [Messenger] Mention the transport which failed during the setup command (@thePanz)
feature #51786 [AssetMapper] Always downloading vendor files (@weaverryan)
feature #51832 [DependencyInjection] Add #[AutowireIterator] attribute and improve #[AutowireLocator] (@nicolas-grekas, @kbond)
feature #50934 [Form] Add duplicate_preferred_choices option to ChoiceType (@arnaud-deabreu)
feature #51650 [AssetMapper] Add audit command (@Jean-Beru)
feature #51800 [DoctrineBridge] Pass Request to EntityValueResolver’s expression (@HypeMC)
feature #51848 [Messenger] Resend failed retries back to failure transport (@ro0NL)
feature #51811 Add „dev“ keyword to symfony/symfony package (@nicolas-grekas)
feature #51276 [Notifier] Transport possible to have null (@StaffNowa)
feature #50662 [FrameworkBundle] Add HttpClientAssertionsTrait which provide shortcuts to assert HTTP calls was triggered (@welcoMattic)
feature #50392 Move UriSigner from HttpKernel to HttpFoundation package (@alexander-schranz)
feature #51804 [Security] Make impersonation_path() argument mandatory and add impersonation_url() (@alexandre-daubois)
feature #50127 [TwigBridge] Add FormLayoutTestCase class (@ker0x)
feature #50030 Add new twig bridge function to generate impersonation path (@PhilETaylor)
feature #50109 [FrameworkBundle] Add –show-aliases option to debug:router command (@fancyweb)
feature #50141 Allow sending scheduled messages through the slack API (@Insanfly)
feature #50321 [TwigBridge] Add AppVariable::getEnabledLocales() (@jmsche)
feature #51676 [RateLimiter] Add SlidingWindowLimiter::reserve() (@Jeroeny)
feature #51538 [HttpFoundation] Support root-level Generator in StreamedJsonResponse (@Jeroeny)
feature #51653 [Messenger] Add WrappedExceptionsInterface for nested exceptions (@Jeroeny)
feature #51690 [Mime] Add TemplatedEmail::locale() to set the locale for the email rendering (@alexander-schranz)
feature #51525 [Messenger][Scheduler] Add AsCronTask & AsPeriodicTask attributes (@valtzu)
feature #51795 [Scheduler] Make debug:scheduler output more useful (@fabpot)
feature #51793 [FrameworkBundle] Change BrowserKitAssertionsTrait::getClient() to be protected (@fabpot)
feature #44629 [FrameworkBundle] Allow BrowserKit relative URL redirect assert (@julienfalque)
feature #51756 [Messenger] RejectRedeliveredMessageException should not be retried (@nikophil)
feature #51779 [Serializer] Make ProblemNormalizer give details about Messenger’s ValidationFailedException (@MatTheCat)
feature #51772 [WebProfilerBundle] Support ! negation operator in url filter (@SzymonKaminski)
feature #51729 [AssetMapper] Allow simple, relative paths in importmap.php (@weaverryan)
feature #51697 [PropertyInfo] Make isWriteable() more consistent with isReadable() when checking snake_case properties (@jbtronics)
feature #51543 [AssetMapper] Add support for CSS files in the importmap (@weaverryan)
feature #51593 [Messenger] Add the –all option to the messenger:failed:remove command (@alexandre-daubois)
feature #51542 [Scheduler] Trigger unique messages at runtime (@Jeroeny)
feature #51415 [Clock] Add DatePoint: an immutable DateTime implementation with stricter error handling and return types (@nicolas-grekas)
feature #51553 [Scheduler] Allow modifying the schedule at runtime and recalculate heap (@Jeroeny)
feature #51712 Deprecate Kernel::stripComments() (@alamirault)
feature #51687 [Messenger] Add support for multiple Redis Sentinel hosts (@digilist)
feature #51153 [Translation] Add –as-tree option to translation:pull command (@syffer)
feature #51601 [Mime] Allow to add some headers as a strings (@Oipnet)
feature #51684 [Translation] Give current locale to LocaleSwitcher::runWithLocale()’s callback (@alexander-schranz)
feature #51651 [Scheduler] Fix stateful scheduler (@valtzu)
feature #51638 [FrameworkBundle] [Test] add token attributes in KernelBrowser::loginUser() (@Valmonzo)
feature #51558 [HttpClient] Enable using EventSourceHttpClient::connect() for both GET and POST (@wivaku)
feature #51476 [Serializer] Allow Context to target classes (@mtarld)
feature #50438 [Validator] Add is_valid function to Expression constraint (@verdet23, @DEVizzent)
feature #51585 [Security] Add badge resolution to profiler (@Jean-Beru)
feature #51523 [AssetMapper] Allow specifying packages to update with importmap:update (@jmsche)
feature #50705 [Mailer][Webhook] Add Sendgrid webhook support (@WoutervanderLoopNL)
feature #51450 [Mailer] [Smtp] Add DSN param peer_fingerprint for fingerprint verification (@xdavidwu)
feature #51484 [Workflow] deprecate GuardEvent::getContext method (@hhamon)
feature #51351 [AssetMapper] Add command to download missing downloaded packages (@jmsche)
feature #51454 [Validator] Un-deprecate passing an annotation reader to AnnotationLoader (@derrabus)
feature #51434 [Security] [Throttling] Hide username and client ip in logs (@Spomky)
feature #51425 [FrameworkBundle][Validator] Deprecate annotation occurrences (@alexandre-daubois)
feature #51392 [DependencyInjection] add #[AutowireLocator] attribute (@kbond)
feature #51365 [Clock] Add $modifier argument to the now() helper (@nicolas-grekas)
feature #51327 [FrameworkBundle] Add AbstractController::renderBlock() and renderBlockView() (@nicolas-grekas)
feature #51357 [FrameworkBundle] Deprecate not setting some options (uid, validation) (@Jean-Beru)
feature #51325 [FrameworkBundle] Deprecate not setting some options (@Jean-Beru)
feature #51412 [Clock] Throw DateMalformedStringException/DateInvalidTimeZoneException when appropriate (@nicolas-grekas)
feature #51368 [DomCrawler] Added argument $default to method Crawler::attr() (@Rastishka)
feature #51315 [Notifier][Webhook] Add Vonage support (@smnandre)
feature #51349 [Notifier] Add GoIP bridge (@ahmedghanem00)
feature #51332 [SecurityBundle] Deprecate the require_previous_session config option (@alamirault)
feature #51284 [FrameworkBundle][HttpKernel][MonologBridge] Revisit wiring of debug loggers (@nicolas-grekas)
feature #50306 [DomCrawler][FrameworkBundle] Add assertAnySelectorText* (@SVillette)
feature #51263 [Scheduler] Add –all to debug:schedule (@fabpot)
feature #50939 [SecurityBundle] Add $badges argument to Security::login (@MatTheCat)
feature #50951 [FrameworkBundle] Support APP_BUILD_DIR (@ro0NL)
feature #51264 [RemoteEvent][Webhook] Add Brevo support (@blaugueux)
feature #50502 [RemoteEvent][Webhook] Add Mailjet support (@blaugueux)
feature #51250 Remove remaining experimental classes (@fabpot)
feature #51249 [RemoteEvent] Mark component as non experimental (@fabpot)
feature #51248 [Webhook] Mark component as non experimental (@fabpot)
feature #51247 [AssetMapper] Mark component as non experimental (@fabpot)
feature #51246 [Scheduler] Mark component as non experimental (@fabpot)
feature #51245 [Scheduler] Only use toString if defined for message (@fabpot)
feature #51244 [Scheduler] Add –date to schedule:debug (@fabpot)
feature #51210 [Workflow] Add PHP attributes to register listeners and guards (@lyrixx)
feature #48485 [Process] Introducing a new PhpSubprocess handler (@Toflar)
feature #51215 [FrameworkBundle] Enable json_decode_detailed_errors in dev by default (@ostrolucky)
feature #51004 [HttpKernel] Support backed enums in #[MapQueryParameter] (@andersmateusz)
feature #51230 [Scheduler] add ScheduledStamp to RedispatchMessage (@kbond)
feature #51218 [Workflow] Support multiline descriptions in PlantUML (@valtzu)
feature #51073 [Intl] Add support for ISO 3166-1 numeric codes (@benr77)
feature #51191 [Mime] Update mimetypes (@fabpot)
feature #47422 [Process] Support using Process::findExecutable() independently of open_basedir (@BlackbitDevs)
feature #48907 [Validator] Validate time without seconds (@xepozz)
feature #51204 [Workflow] Add a profiler (@lyrixx)
feature #47715 [Form] Removing self-closing slash from <input> (@ThomasLandauer)
feature #50212 [FrameworkBundle][Serializer] Add TranslatableNormalizer (@Jean-Beru)
feature #50767 [HttpKernel] RequestPayloadValueResolver Add support for custom http status code (@zim32)
feature #51172 [Serializer] Add support for seld/jsonlint (@ostrolucky)
feature #49231 [Translation] Phrase translation provider (@wickedOne)
feature #50974 [Workflow] Add support for storing the marking in a property (@lyrixx)
feature #51092 [Scheduler] make ScheduledStamp „send-able“ (@kbond)
feature #51197 [PsrHttpMessageBridge] Support php-http/discovery for auto-detecting PSR-17 factories (@derrabus)
feature #48841 [BrowserKit] Add argument $serverParameters to click() and clickLink() (@syl20b)
feature #49594 [Serializer] Groups annotation/attribute on class (@Brajk19)
feature #50879 [Notifier] support local development for sns by adding sslmode option (@Ferror)
feature #51152 [Scheduler] Add AbstractTriggerDecorator (@kbond)
feature #49814 [Console][Messenger] add RunCommandMessage and RunCommandMessageHandler (@kbond)
feature #50978 [Messenger] Allow accessing all options on a handler descriptor (@ruudk)
feature #50911 [HttpKernel] Enhance exception if possible (@lyrixx)
feature #50136 [Notifier] [SpotHit] Support smslong and smslongnbr API parameters (@camillebaronnet)
feature #50907 [Validator] Update Type constraint, add number, finite-float and finite-number validations (@guillaume-a)
feature #51130 [VarDumper] Dump uninitialized properties (@nicolas-grekas)
feature #51144 [Templating] deprecate the component (@kbond)
feature #51014 [Mailer] Add Scaleway bridge (@MrMicky-FR)
feature #51167 [PsrHttpMessageBridge] Remove ArgumentValueResolverInterface from PsrServerRequestResolver (@derrabus)
feature #51100 [PsrHttpMessageBridge] Import the bridge into the monorepo (@fabpot, @dunglas, @KorvinSzanto, @xabbuh, @aimeos, @ahundiak, @Danielss89, @rougin, @csunolgomez, Jérôme Parmentier, @mtibben, @Nyholm, @ajgarlag, @uphlewis, @samnela, @grachevko, @nicolas-grekas, @tinyroy, @danizord, Daniel Degasperi, @rbaarsma, @Ekman, @4rthem, @derrabus, @mleczakm, @iluuu1994, @Tobion, @chalasr, @lemon-juice, @franmomu, @cidosx, @erikn69, @AurelienPillevesse)
feature #49815 [HttpClient][Messenger] add PingWebhookMessage and PingWebhookMessageHandler (@kbond)
feature #49813 [Messenger][Process] add RunProcessMessage and RunProcessMessageHandler (@kbond)
feature #51148 [FrameworkBundle] Simplify marking store configuration (@nicolas-grekas)
feature #51128 [SecurityBundle] Allow an array of pattern in firewall configuration (@lyrixx, @chalasr)
feature #119 Implement ValueResolverInterface (@derrabus)
feature #117 Leverage Request::getPayload() to populate the parsed body of PSR-7 requests (@AurelienPillevesse)
feature #50931 [Form] Support Translatable Enum (@Seb33300)
feature #49358 [Routing] Deprecate annotations in favor of attributes (@derrabus)
feature #50982 [Validator] Deprecate annotations in favor of attributes (@derrabus)
feature #50983 [Serializer] Deprecate annotations in favor of attributes (@derrabus)
feature #51043 [Form] Deprecate FormEvent::setData() for events that do not allow it (@HeahDude)
feature #50888 [FrameworkBundle] Deprecate doctrine/annotations integration (@derrabus)
feature #50997 [Messenger] Deprecate StopWorkerOnSignalsListener (@HypeMC)
feature #50290 [Security] Make PersistentToken immutable and tell TokenProviderInterface::updateToken() implementations should accept DateTimeInterface (@nicolas-grekas)
feature #50883 [TwigBundle] Allow omitting the autoescape_service_method option when autoescape_service is set to an invokable service id (@nicolas-grekas)
feature #50718 [DependencyInjection] Improve reporting named autowiring aliases (@nicolas-grekas)
feature #50295 [PropertyAccess] Auto-cast from/to DateTime/Immutable when appropriate (@nicolas-grekas)
feature #50420 [Console] add support for catching Throwable errors (@lyrixx)
feature #50148 [Mailer] Add X-Infobip-Track header to be able to disable tracking (@ndousson)
feature #50200 [Mailer] Adds assertEmailSubjectContains and assertEmailSubjectNotContains methods (@johanadivare)
feature #50302 [Mailer] New Brevo mailer bridge (formerly Sendinblue) (@PEtanguy)
feature #50296 [Notifier] Add Brevo bridge (formerly Sendinblue) (@PEtanguy)
feature #50842 Add missing return types to magic methods (@wouterj)
feature #50868 [SecurityBundle] Deprecate Security::* consts and other cleanups (@nicolas-grekas)
feature #50770 [TwigBridge] Allow to change element for form_help block (@seb-jean)
feature #50814 [HttpClient] Allow custom working directory in TestHttpServer (@ro0NL)
feature #46426 [Form] deprecate using the date and time types with date objects with not-matching timezones (@xabbuh)
feature #50791 [DependencyInjection] Add defined prefix for env var processor (@GaryPEGEOT)
feature #50754 [HttpKernel] when configuring the container add services_{env} with php extension (@helyakin)
feature #50425 [Validator] Allow single constraint to be passed to the constraints option of the When constraint (@alexandre-daubois)
feature #50396 [Validator] Allow single integer for the versions option of the Uuid constraint (@alexandre-daubois)
feature #50621 [FrameworkBundle][Workflow] Add metadata dumping support for GraphvizDumper (@Louis-Proffit)
feature #50170 [Notifier] Added redlink notifier (@plotkabytes)
feature #50615 [DependencyInjection] Deprecate ContainerAwareInterface, ContainerAwareTrait and ContainerAwareLoader (@alexandre-daubois)
feature #50084 [Routing] Add FQCN and FQCN::method aliases when applicable (@fancyweb)
feature #50691 [Console] Aligned multiline text in vertical table (@jaytaph)
feature #50131 [Notifier] add Ntfy bridge (@mikaelkael)
feature #50663 [Console] Add SignalMap to map signal value to its name (@lyrixx)
feature #50414 [Notifier] Add Novu bridge (@wouter-toppy)
feature #50240 [HttpClient] Add max_retries option to RetryableHttpClient (@danielburger1337)
feature #50572 [Scheduler] Allow setting cron expression next run date timezone (@danielburger1337)
feature #50579 [DoctrineBridge] Deprecate using the old DBAL logger system (@derrabus)
feature #50335 [HttpKernel] Add optional $className param to ControllerEvent::getAttributes() (@HypeMC)
feature #113 Bump psr/http-message version (@erikn69)
feature #114 Drop support for Symfony 4 (@derrabus)
feature #100 Allow Symfony 6 (@chalasr)
feature #89 PSR HTTP message converters for controllers (@derrabus)
feature #75 Remove deprecated code (@fabpot)
feature #66 Add support for streamed Symfony request (@Ekman)
feature #50 Add support for streamed response (@danizord)
feature #62 bump to PHP 7.1 (@nicolas-grekas)
feature #43 Create PSR-7 messages using PSR-17 factories (@ajgarlag)
feature #45 Fixed broken build (@Nyholm)
feature #1 Initial support (@dunglas)

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