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[BrowserWasm + Safari / Firefox] First attempt (in session) of Windows.Storage.Pickers.FileSavePicker.PickSaveFileAsync throws exception #21335

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Bug
#21434
Open
[BrowserWasm + Safari / Firefox] First attempt (in session) of Windows.Storage.Pickers.FileSavePicker.PickSaveFileAsync throws exception#21335
Bug
#21434
Assignees
MartinZikmund
Labels
difficulty/tbdCategorizes an issue for which the difficulty level needs to be defined.triage/untriagedIndicates an issue requires triaging or verification
@baskren

Description

@baskren
baskren
opened on Aug 22, 2025

Current behavior 🐛

The first attempt (in a session) to call Windows.Storage.Pickers.FileSavePicker.PickSaveFileAsync on app targeting BrowserWasm in Safari or FireFox causes the below exception. Repeating a second time is successful.

Console Log (with Stack Trace) 
[Log] Setting DOTNET_MODIFIABLE_ASSEMBLIES=debug (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_MONO_RUNTIME_MODE=Interpreter (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_MONO_PROFILED_AOT=False (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_LINKER_ENABLED=False (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_DEBUGGER_ENABLED=True (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_MONO_RUNTIME_CONFIGURATION=Release (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_MONO_RUNTIME_FEATURES= (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_APP_BASE=package_b60a15cbe8405dc287f88a94b6ab990b8bd2c1e9 (uno-bootstrap.js, line 238)
[Log] Setting UNO_BOOTSTRAP_WEBAPP_BASE_PATH=/ (uno-bootstrap.js, line 238)
[Log] dotnet Loaded 97.94 MB resources (dotnet.js, line 3)
This application was built with linking (tree shaking) disabled. 
Published applications will be significantly smaller if you install wasm-tools workload. 
See also https://aka.ms/dotnet-wasm-features
[Log] Loaded 97.67 MB resources from cache (dotnet.js, line 3)
[Log] (Index)responseBytesCommonServiceLocator.pxaxvyzjv1.wasm8981CommunityToolkit.Mvvm.4sdv9o2ycm.wasm108309HarfBuzzSharp.ebz6e2ijn2.wasm111893Microsoft.Bcl.AsyncInterfaces.30mhlu84h1.wasm5397Microsoft.CSharp.wjcmf9ahqt.wasm297237Microsoft.Extensions.Configuration.Abstractions.8ewlps0g9m.wasm18709Microsoft.Extensions.Configuration.Binder.yr6bnfroy5.wasm34069Microsoft.Extensions.Configuration.CommandLine.wlmqcj7yq5.wasm14101Microsoft.Extensions.Configuration.EnvironmentVariables.wbxytkwaq1.wasm10517Microsoft.Extensions.Configuration.FileExtensions.vpmbyydd3g.wasm17173Microsoft.Extensions.Configuration.Json.ua9xbwdl0u.wasm16149Microsoft.Extensions.Configuration.UserSecrets.93wpcdi3tn.wasm14613Microsoft.Extensions.Configuration.itm12vk377.wasm34581Microsoft.Extensions.DependencyInjection.Abstractions.apuz8nsfml.wasm55061Microsoft.Extensions.DependencyInjection.v66dtpac4v.wasm82709Microsoft.Extensions.Diagnostics.Abstractions.eim2lc13mh.wasm19733Microsoft.Extensions.Diagnostics.xg83zizj0a.wasm24853Microsoft.Extensions.FileProviders.Abstractions.1c7ksbormu.wasm11541Microsoft.Extensions.FileProviders.Physical.rpvltkbyzt.wasm34069Microsoft.Extensions.FileSystemGlobbing.i464dwxnbb.wasm35093Microsoft.Extensions.Hosting.3wvuphxxor.wasm61717Microsoft.Extensions.Hosting.Abstractions.kpoaap44tz.wasm40725Microsoft.Extensions.Logging.Abstractions.nwxyu3e2hm.wasm56597Microsoft.Extensions.Logging.Configuration.vnquychvwj.wasm18709Microsoft.Extensions.Logging.Console.bnool388rq.wasm64789Microsoft.Extensions.Logging.Debug.ejywa1axmv.wasm9493Microsoft.Extensions.Logging.EventLog.01wyqjbdp0.wasm15125Microsoft.Extensions.Logging.EventSource.h2ym9z2otd.wasm23829Microsoft.Extensions.Logging.ul0xzjnwdm.wasm41749Microsoft.Extensions.ObjectPool.29jllz6gfq.wasm12053Microsoft.Extensions.Options.ConfigurationExtensions.zrlhdwvckr.wasm12053Microsoft.Extensions.Options.l36scmr1xu.wasm55573Microsoft.Extensions.Primitives.358c2dzezi.wasm34581Microsoft.VisualBasic.Core.ccpi3o747q.wasm419605Microsoft.VisualBasic.pbpr2ghqk0.wasm6933Microsoft.Win32.Primitives.dqwofb9ps2.wasm4885Microsoft.Win32.Registry.AccessControl.7q5zewvdul.wasm11541Microsoft.Win32.Registry.rcu343ydbj.wasm22805Microsoft.Win32.SystemEvents.uhkqoxi4ko.wasm16661Newtonsoft.Json.qkbufwhni2.wasm700181SkiaSharp.9lgs1ggdq4.wasm478997SkiaSharp.Resources.81h9g0de09.wasm11541SkiaSharp.SceneGraph.ocjed5swwj.wasm7957SkiaSharp.Skottie.zfzt8l6vvp.wasm15637SkiaSharp.Views.Windows.6b4kbbym4h.wasm18709SkiaSharp.Views.Windows.n8e5vady4d.pdb19708System.AppContext.00rm2k4rqj.wasm4885System.Buffers.z32pttvtk4.wasm4885System.CodeDom.v2m9imp9c1.wasm174357System.Collections.Concurrent.rx21q3n11f.wasm79125System.Collections.Immutable.d8bqqugfwk.wasm245013System.Collections.NonGeneric.5ray22bvhs.wasm37653System.Collections.Specialized.i9b18l2jwg.wasm37653System.Collections.r2s7n2sx3x.wasm115989System.ComponentModel.Annotations.shw18la3r8.wasm91925System.ComponentModel.Composition.21hzic7k23.wasm284437System.ComponentModel.Composition.Registration.uzqfwvvc89.wasm40725System.ComponentModel.DataAnnotations.3tfviggf6l.wasm6421System.ComponentModel.EventBasedAsync.yssxj4mc04.wasm16149System.ComponentModel.Primitives.b2gyl5z8cy.wasm31509System.ComponentModel.TypeConverter.o2rbwek366.wasm304917System.ComponentModel.ijpzmqvdg2.wasm5909System.Configuration.ConfigurationManager.aaroqrzm4f.wasm432405System.Configuration.s48boytfg6.wasm8981System.Console.0c362v5xxq.wasm43285System.Core.aiaao2jpd5.wasm13077System.Data.Common.lcca6mlcc9.wasm1005845System.Data.DataSetExtensions.8vc4lkhdbq.wasm5397System.Data.Odbc.ya99chn8dj.wasm91413System.Data.OleDb.00k1l1tecd.wasm114453System.Data.SqlClient.kngaw24f5u.wasm161045System.Data.zn919kbv52.wasm14613System.Diagnostics.Contracts.q6kkw3vdcg.wasm5909System.Diagnostics.Debug.2ahnaecxp2.wasm5397System.Diagnostics.DiagnosticSource.g6jmcgi72c.wasm173845System.Diagnostics.EventLog.6ypc00ngj3.wasm42773System.Diagnostics.FileVersionInfo.vpthu2a2k9.wasm12053System.Diagnostics.PerformanceCounter.yxo4efak0a.wasm43285System.Diagnostics.Process.agxw6p2exh.wasm46357System.Diagnostics.StackTrace.r4u6i8kfog.wasm15637System.Diagnostics.TextWriterTraceListener.zuba91cmsq.wasm21269System.Diagnostics.Tools.t9yjdk35pr.wasm4885System.Diagnostics.TraceSource.90w5tp9zha.wasm48405System.Diagnostics.Tracing.uno27yk9k6.wasm5909System.DirectoryServices.AccountManagement.0wccnj1fi1.wasm59157System.DirectoryServices.Protocols.1gs8y2pt6s.wasm63253System.DirectoryServices.zv3q7ifd7s.wasm120085System.Drawing.Common.6bmqjur404.wasm474901System.Drawing.Primitives.nzdrnpuduj.wasm54037System.Drawing.egkesygmuw.wasm10005System.Dynamic.Runtime.efxlzpwato.wasm5909System.Formats.Asn1.xxh459yzyl.wasm85781System.Formats.Tar.qx19rhlhxw.wasm27925System.Globalization.Calendars.8s8o2vqz82.wasm5397System.Globalization.Extensions.c5jbxrm4w6.wasm4885System.Globalization.up27xu0uxp.wasm5397System.IO.6m5851g67n.wasm5397System.IO.Compression.Brotli.797644ybc0.wasm17685System.IO.Compression.FileSystem.phrc4jhttw.wasm4885System.IO.Compression.ZipFile.odllsikviu.wasm27413System.IO.Compression.em8v7c7339.wasm99605System.IO.FileSystem.AccessControl.9er38h0om3.wasm21781System.IO.FileSystem.DriveInfo.5n4il3qn29.wasm13589System.IO.FileSystem.Primitives.q19vnktpak.wasm4885System.IO.FileSystem.Watcher.m01xezp84e.wasm22805System.IO.FileSystem.canbiw5jz4.wasm5397System.IO.IsolatedStorage.ovh8t119yi.wasm24853System.IO.MemoryMappedFiles.wjnda4frws.wasm38165System.IO.Packaging.nm9ox7vpy6.wasm147733System.IO.Pipelines.7ro2a7frhf.wasm67861System.IO.Pipes.AccessControl.9pomna8szr.wasm13077System.IO.Pipes.tqouqgzazg.wasm32021System.IO.Ports.ll0lso2o3p.wasm26901System.IO.UnmanagedMemoryStream.2qs4v41wjf.wasm4885System.Json.jh0shol1ss.wasm28437System.Linq.Expressions.ejydgoj0oc.wasm565013System.Linq.Parallel.is9nca195d.wasm212757System.Linq.Queryable.8vjofh88qa.wasm65813System.Linq.zqotd0pp5c.wasm138517System.Management.tzqn4hxx4r.wasm63765System.Memory.mr8xev4a41.wasm45333System.Net.Http.Json.fsk5apfw1y.wasm45845System.Net.Http.jzkfjdda15.wasm276245System.Net.HttpListener.xweq5xme4y.wasm45845System.Net.Mail.exa7sc8li4.wasm93461System.Net.NameResolution.7nsh0ffju4.wasm14101System.Net.NetworkInformation.16618q39eu.wasm32021System.Net.Ping.73n1msm1kf.wasm17685System.Net.Primitives.cp7icbjoye.wasm94997System.Net.Quic.5ac51dyvls.wasm28437System.Net.Requests.74urp2owxv.wasm55573System.Net.Security.q4em7fcmos.wasm100629System.Net.ServicePoint.60vubhwq2d.wasm4885System.Net.Sockets.6qp5a9tfvh.wasm64277System.Net.WebClient.kwo41wq289.wasm44309System.Net.WebHeaderCollection.t1y05ppbtx.wasm22805System.Net.WebProxy.232idirb7b.wasm11541System.Net.WebSockets.7ns4dakcmj.wasm92437System.Net.WebSockets.Client.1rwz2j0ytm.wasm39189System.Net.hyl81vktsx.wasm6933System.Numerics.3xrgeyndxe.wasm4885System.Numerics.Vectors.3ulov9gswu.wasm5397System.ObjectModel.2onw4a3huo.wasm30997System.Private.CoreLib.gcclii65ud.wasm4641561System.Private.DataContractSerialization.viwejdyf0o.wasm841493System.Private.ServiceModel.pfgxos2p1e.wasm2675993System.Private.Uri.gccfg575xd.wasm92437System.Private.Windows.Core.hjjrl2ruqu.wasm844053System.Private.Xml.36oo928nq7.wasm3089177System.Private.Xml.Linq.hubb8bdrav.wasm143125System.Reflection.Context.40su3wgeax.wasm73493System.Reflection.DispatchProxy.ytnrm7l6ga.wasm27925System.Reflection.Emit.ILGeneration.n2z595t7zv.wasm5397System.Reflection.Emit.Lightweight.icwj787vcb.wasm5397System.Reflection.Emit.w74i2eyu03.wasm119573System.Reflection.Extensions.5iae6nghwr.wasm4885System.Reflection.Metadata.eu6g5dmyrp.wasm490773System.Reflection.Primitives.8h25o84kf1.wasm5397System.Reflection.TypeExtensions.ncossl2nra.wasm13589System.Reflection.fu4huwo1gu.wasm5909System.Resources.Reader.ckle7drwww.wasm4885System.Resources.ResourceManager.n9sh7wxvjn.wasm5397System.Resources.Writer.9kebxuk0er.wasm16149System.Runtime.Caching.50qknxx7sv.wasm80149System.Runtime.CompilerServices.Unsafe.j5tmcq1bfo.wasm4885System.Runtime.CompilerServices.VisualC.02zc66007n.wasm6933System.Runtime.Extensions.oiot8mv0g3.wasm7445System.Runtime.Handles.vvyys879d4.wasm4885System.Runtime.InteropServices.JavaScript.y6arj9x08o.wasm75029System.Runtime.InteropServices.RuntimeInformation.4gcavmlio6.wasm4885System.Runtime.InteropServices.zcf5xh4j89.wasm54037System.Runtime.Intrinsics.unx94uxfba.wasm6933System.Runtime.Loader.lio72255su.wasm5397System.Runtime.Numerics.drjgq7o7pq.wasm132885System.Runtime.Serialization.Formatters.7hfaupc75z.wasm55573System.Runtime.Serialization.Json.avkizgk9x1.wasm5397System.Runtime.Serialization.Primitives.k309oqfoa4.wasm13077System.Runtime.Serialization.Xml.0jwn7dp9nd.wasm6421System.Runtime.Serialization.z7sglijpt0.wasm6421System.Runtime.c61u9af934.wasm34069System.Security.80ju9y7l18.wasm7957System.Security.AccessControl.rl384mt7e7.wasm47893System.Security.Claims.845vwhbngt.wasm43285System.Security.Cryptography.05gw4icbhi.wasm506133System.Security.Cryptography.Algorithms.v13868m0ek.wasm6933System.Security.Cryptography.Cng.uqhggvgrxh.wasm5909System.Security.Cryptography.Csp.ujtlhftd9v.wasm5397System.Security.Cryptography.Encoding.9v1z3jix27.wasm5397System.Security.Cryptography.OpenSsl.zh8vki7uno.wasm4885System.Security.Cryptography.Pkcs.7ptau9y6e1.wasm254741System.Security.Cryptography.Primitives.x3mep84tc4.wasm5397System.Security.Cryptography.ProtectedData.w3p0d2n8rb.wasm27925System.Security.Cryptography.X509Certificates.j8t07tanc6.wasm6421System.Security.Cryptography.Xml.9l41mpjlyt.wasm190229System.Security.Permissions.fari7bzgj5.wasm106773System.Security.Principal.5bg4gnsg0x.wasm4885System.Security.Principal.Windows.m4byz8sabo.wasm27413System.Security.SecureString.fiastri9ki.wasm4885System.ServiceModel.Duplex.qu6egemkqj.wasm4885System.ServiceModel.Http.2m1r9rsrio.wasm5909System.ServiceModel.NetTcp.aznzgwpjl3.wasm5397System.ServiceModel.Primitives.8ns2yka105.wasm12565System.ServiceModel.Security.rgq7la03ko.wasm6933System.ServiceModel.Syndication.k3idt88b63.wasm111381System.ServiceModel.Web.tv3f98ejk8.wasm6421System.ServiceModel.ciohnwfst3.wasm14613System.ServiceProcess.ServiceController.t6ymsc7wpa.wasm24341System.ServiceProcess.j3o0lzzi7t.wasm5397System.Speech.xo62a7uq99.wasm299285System.Text.Encoding.CodePages.k9n474vgzf.wasm730389System.Text.Encoding.Extensions.esy6mc7t8y.wasm5397System.Text.Encoding.so36gwcdvm.wasm5397System.Text.Encodings.Web.g33dyw9sdz.wasm60181System.Text.Json.o0tkiahb9x.wasm606997System.Text.RegularExpressions.5x7wnnoptp.wasm358677System.Threading.AccessControl.1c8h2ny2vc.wasm23317System.Threading.Channels.sans7ybw3q.wasm46357System.Threading.Overlapped.w9h9po1nje.wasm5397System.Threading.Tasks.Dataflow.fhcbb6k32h.wasm175381System.Threading.Tasks.Extensions.hs7o6v5tiq.wasm5397System.Threading.Tasks.Parallel.k8t7rlfiat.wasm50965System.Threading.Tasks.tbqaq378z6.wasm6421System.Threading.Thread.76ednmbzmi.wasm5397System.Threading.ThreadPool.dggkxr83to.wasm5397System.Threading.Timer.j8kpz62luj.wasm4885System.Threading.myoimpdcs6.wasm34581System.Transactions.Local.7hdcq2g011.wasm165141System.Transactions.p83alyf85n.wasm5909System.ValueTuple.ygaqfhsa0b.wasm4885System.Web.HttpUtility.btaxuyjcvs.wasm19733System.Web.Services.Description.y8a2g098r1.wasm374549System.Web.xfk5e3d2ux.wasm4885System.Windows.Extensions.37gz19db5w.wasm18197System.Windows.dvpjq0fzc1.wasm5397System.Xml.Linq.3g0uzfg3q5.wasm5397System.Xml.ReaderWriter.nmw5lay0th.wasm11541System.Xml.Serialization.35x5v84a2s.wasm5909System.Xml.XDocument.dm2u9ur6u8.wasm5397System.Xml.XPath.XDocument.p77fb7ls9l.wasm5397System.Xml.XPath.gkgxk99utf.wasm5397System.Xml.XmlDocument.obea1y0o4e.wasm5397System.Xml.XmlSerializer.69wknkil2z.wasm7445System.Xml.ob3ozmrjnu.wasm13077System.n8l4zjq3i2.wasm39701Uno.Core.Extensions.Collections.pjq296lqp0.wasm76053Uno.Core.Extensions.Disposables.nq3oin13rl.wasm14613Uno.Core.Extensions.Equality.qvkla94k3e.wasm13589Uno.Core.Extensions.Logging.5g4osb9268.wasm19221Uno.Core.Extensions.Logging.Singleton.53pf8uyhx0.wasm9493Uno.Diagnostics.Eventing.0doxcndiyn.wasm16149Uno.Extensions.Core.829uzvwc1w.wasm57621Uno.Extensions.Core.UI.8n69o8t8k7.wasm25877Uno.Extensions.Logging.WebAssembly.Console.t3bgcl6fir.wasm19221Uno.Extensions.Markup.eb22xnzy78.wasm90901Uno.Fonts.Fluent.aj4vxe01pi.wasm3349Uno.Fonts.OpenSans.jsokrg0hj6.wasm4373Uno.Fonts.Roboto.e290i8pj3r.wasm4373Uno.Foundation.4ezs2ufkbp.pdb91776Uno.Foundation.Logging.svr9qhlkq1.wasm11029Uno.Foundation.Runtime.WebAssembly.flg41rv696.wasm57109Uno.Foundation.ideie3om9i.wasm198421Uno.Themes.WinUI.iox80c3nv0.wasm386325Uno.Toolkit.WinUI.4ka9boi1uh.wasm802581Uno.Toolkit.WinUI.Markup.dvnfomfm5j.wasm448277Uno.Toolkit.lrjbuf7ej1.wasm5909Uno.UI.Adapter.Microsoft.Extensions.Logging.bxkc1ewhqe.wasm7957Uno.UI.Composition.m8g98ncrtw.pdb179616Uno.UI.Composition.v7qp6kx48x.wasm505109Uno.UI.Dispatching.fgao22bh82.wasm34581Uno.UI.Dispatching.mtutzdpxvw.pdb21092Uno.UI.FluentTheme.5s7mgd5cd7.pdb40784Uno.UI.FluentTheme.tuwwfbvlhg.wasm218901Uno.UI.FluentTheme.v1.90y2caqyb7.wasm211733Uno.UI.FluentTheme.v1.iewqpvuuit.pdb37268Uno.UI.FluentTheme.v2.0g0unln3j3.wasm3432729Uno.UI.FluentTheme.v2.dhj62gtryn.pdb1716216Uno.UI.HotDesign.Abstractions.9lz69dsuoo.wasm24853Uno.UI.HotDesign.Client.Core.u91pqtj3mg.wasm1491221Uno.UI.HotDesign.Client.i3qr6xnssr.wasm1244437Uno.UI.HotDesign.CommunityToolkit.9c3l9v1tyb.wasm75029Uno.UI.HotDesign.Hierarchy.bwr8cnx2wl.wasm106261Uno.UI.HotDesign.Messaging.bglgidkp6m.wasm974613Uno.UI.HotDesign.PropertyGrid.ed1l6kmdi0.wasm906517Uno.UI.HotDesign.Toolbox.g924gq7j81.wasm88853Uno.UI.HotDesign.Xaml.Interactions.sr4wmukuoj.wasm74005Uno.UI.HotDesign.Xaml.Interactivity.f9cse167ud.wasm37141Uno.UI.HotDesign.Xaml.yp4f4c709x.wasm93461Uno.UI.HotDesign.pbekiuzlo1.wasm9493Uno.UI.Lottie.74u6m641dn.pdb62700Uno.UI.Lottie.csdsat23en.wasm125205Uno.UI.RemoteControl.Messaging.533hyafstr.wasm39189Uno.UI.RemoteControl.vsbl8rm4fv.pdb86340Uno.UI.RemoteControl.xclmqycn85.wasm429333Uno.UI.Runtime.Skia.WebAssembly.Browser.if4moey6rg.wasm202517Uno.UI.Runtime.Skia.b3u8sxa2m9.wasm6933Uno.UI.Toolkit.5zfxl5tbvc.wasm276245Uno.UI.Toolkit.9kwdux1774.pdb54076Uno.UI.ilhs9hb9er.pdb4147496Uno.UI.rqkayfu4hu.wasm11180313Uno.Wasm.MetadataUpdater.av5lwrhwgn.pdb17780Uno.Wasm.MetadataUpdater.ijppipo4qi.wasm20757Uno.Wasm.WebSockets.lf2f7pl205.wasm17173Uno.WinUI.Graphics2DSK.skccx6igvl.wasm6421Uno.WinUI.Markup.5d3yxpgcdg.wasm3240217Uno.Xaml.k16hob4n86.pdb80820Uno.Xaml.p5qut58g79.wasm196373Uno.p0l3l936cq.wasm11008281Uno.rc1i0xdzib.pdb1607392WindowsBase.pe1q66fox7.wasm5909dotnet.native.8jyu09lvfp.wasm26133798icudt_EFIGS.tptq2av103.dat550832mscorlib.ypkr78tz1c.wasm49429netstandard.ifx8vojh9u.wasm90389 (dotnet.js, line 3)
[Log] Loaded 0.28 MB resources from network (dotnet.js, line 3)
[Log] (Index)responseBytesUnoApp4.15czkeypps.pdb290980 (dotnet.js, line 3)
[Debug] Active service worker found, skipping register (uno-bootstrap.js, line 455)
[Debug] Making persistent: /local (Uno.Wasm.js, line 1850)
[Debug] Making persistent: /roaming (Uno.Wasm.js, line 1850)
[Debug] Making persistent: /shared (Uno.Wasm.js, line 1850)
[Error] WebGL: INVALID_ENUM: getParameter: invalid parameter name, WEBGL_debug_renderer_info not enabled
	getParameter
	_glGetString (dotnet.native.2vn64vi5fk.js:7946)
	<?>.wasm-function[23248]
	dotnet.native.wasm.wasm-function[GrGLGetDriverInfo(GrGLInterface const*)]
	<?>.wasm-function[29358]
	<?>.wasm-function[21606]
	<?>.wasm-function[21716]
	dotnet.native.wasm.wasm-function[GrDirectContext::MakeGL(sk_sp<GrGLInterface const>)]
	<?>.wasm-function[14683]
	dotnet.native.wasm.wasm-function[do_icall]
	dotnet.native.wasm.wasm-function[do_icall_wrapper]
	dotnet.native.wasm.wasm-function[mono_interp_exec_method]
	dotnet.native.wasm.wasm-function[interp_runtime_invoke]
	dotnet.native.wasm.wasm-function[mono_jit_runtime_invoke]
	dotnet.native.wasm.wasm-function[do_runtime_invoke]
	dotnet.native.wasm.wasm-function[mono_runtime_try_invoke]
	dotnet.native.wasm.wasm-function[mono_runtime_invoke]
	dotnet.native.wasm.wasm-function[mono_wasm_invoke_jsexport]
	ccall (dotnet.native.2vn64vi5fk.js:10469)
	gn (dotnet.runtime.5nhp1wfg9b.js:3:28865)
	(anonymous function) (dotnet.runtime.5nhp1wfg9b.js:3:37342)
	render (Uno.Runtime.Wasm.js:1140)
[Log] Button2Click Exception: System.IO.DirectoryNotFoundException: Could not find a part of the path '/cache/test.txt'. (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Interop.ThrowExceptionForIoErrno(ErrorInfo errorInfo, String path, Boolean isDirError) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Interop.CheckIo(Error error, String path, Boolean isDirError) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String path, OpenFlags flags, Int32 mode, Boolean failForSymlink, Boolean& wasSymlink, Func`4 createOpenException) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, UnixFileMode openPermissions, Int64& fileLength, UnixFileMode& filePermissions, Boolean failForSymlink, Boolean& wasSymlink, Func`4 createOpenException) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode, Func`4 createOpenException) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.Strategies.UnixFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.Strategies.FileStreamHelpers.ChooseStrategy(FileStream fileStream, String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, Int64 preallocationSize) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean useAsync) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.File.Create(String path, Int32 bufferSize) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.IO.File.Create(String path) (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Windows.Storage.StorageFolder.Local.CreateFileAsync(String desiredName, CreationCollisionOption options, CancellationToken cancellationToken) in C:\a\1\s\src\Uno.UWP\Storage\StorageFolder.Local.cs:line 110 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Windows.Foundation.AsyncOperation`1.<BuildTaskAsync>d__23[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in C:\a\1\s\src\Uno.Foundation\Internal\AsyncOperation.TResult.cs:line 83 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.WindowsRuntimeSystemExtensions.<AsTaskCore>d__11`1[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in C:\a\1\s\src\Uno.UWP\System.Runtime\WindowsRuntimeSystemExtensions.cs:line 66 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Windows.Storage.Pickers.FileSavePicker.DownloadPickerPickSaveFileAsync(CancellationToken token) in C:\a\1\s\src\Uno.UWP\Storage\Pickers\FileSavePicker.wasm.cs:line 107 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Windows.Storage.Pickers.FileSavePicker.PickSaveFileTaskAsync(CancellationToken token) in C:\a\1\s\src\Uno.UWP\Storage\Pickers\FileSavePicker.wasm.cs:line 49 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at Windows.Foundation.AsyncOperation`1.<BuildTaskAsync>d__23[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in C:\a\1\s\src\Uno.Foundation\Internal\AsyncOperation.TResult.cs:line 83 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at System.WindowsRuntimeSystemExtensions.<AsTaskCore>d__11`1[[Windows.Storage.StorageFile, Uno, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null]].MoveNext() in C:\a\1\s\src\Uno.UWP\System.Runtime\WindowsRuntimeSystemExtensions.cs:line 66 (dotnet.native.2vn64vi5fk.js, line 1685)
[Log]    at UnoApp4.MainPage.OnButton2Clicked(Object sender, RoutedEventArgs e) in /Users/ben/RiderProjects/UnoApp4/UnoApp4/MainPage.cs:line 58 (dotnet.native.2vn64vi5fk.js, line 1685)
[Debug] Making persistent: /cache (Uno.Wasm.js, line 1850)

Expected behavior 🎯

No exception thrown on first use of Windows.Storage.Pickers.FileSavePicker.PickSaveFileAsync` during an app session. Nor the required use of the below work-around.

How to reproduce it (as minimally and precisely as possible) 🔬

Demo project: https://github.com/baskren/BrowserWasmFileSavePickerFail

  1. Build / Launch demo project for BrowserWasm
  2. Open app url (typically localhost:5000) in Firefox or Safari
  3. Open the browsers console log
  4. Click on the [SAVE test.txt] button
  5. observe exception in console log
  6. Reload page in browser
  7. Click on [CREATE /cache]
  8. Click on the [SAVE test.txt] button
  9. Notice no exception in console log

Workaround 🛠️

Before calling Windows.Storage.Pickers.FileSavePicker.PickSaveFileAsync`, execute the below code:

        if (!Directory.Exists("/cache"))
            Directory.CreateDirectory("/cache");

Renderer 🎨

  • Skia
  • Native

Affected platforms 📱💻🖥️

WebAssembly

Uno.Sdk version (and other relevant versions) 📦

Uno.Sdk: 6.1.23

UnoFeatures:

        CSharpMarkup;
        Lottie;
        Toolkit;
        ThemeService;
        SkiaRenderer; (with and without)

IDE version 🧑‍💻

Jet Brains Rider

JetBrains Rider 2025.2.0.1
Build #RD-252.23892.537, built on August 20, 2025
Source revision: 0312543a927a3
Licensed to Ben Askren
Subscription is active until July 10, 2026.
Runtime version: 21.0.7+6-b1038.58 aarch64 (JCEF 122.1.9)
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.lwawt.macosx.LWCToolkit
macOS 15.6.1
.NET Core v8.0.11 ARM64 (Server GC)
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 4096M
Cores: 12
Metal Rendering is ON
Registry:
ide.lookup.shrink=true
ide.experimental.ui=true
llm.show.ai.promotion.window.on.start=false
Non-Bundled Plugins:
org.antlr.intellij.plugin (1.24)
com.intellij.resharper.HeapAllocationsViewer (2025.1.0)
com.intellij.copyright (252.23892.464)
com.redhat.devtools.lsp4ij (0.14.2)
lermitage.intellij.iconviewer (1.31.3)
com.github.camork.fileExpander (2.5)
com.wakatime.intellij.plugin (15.0.4)
com.cppcxy.Intellij-SumnekoLua (3.15.0.46-IDEA243)
com.jetbrains.rider.android (252.23892.537)
unoplatform (1.5.19)
Karma (252.25204.0)
me.rafaelldi.aspire (1.8.8)
com.intellij.resharper.azure (4.5.4)

Anything else we need to know? 💬

No response

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