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Unreal Engine 5.8.4

Hotfix

Epic Games, released Oct 20

Unreal Engine 5.8.4 is a hotfix for 5.8.3 with many crash and stability fixes across the editor, rendering, media and platforms. Its biggest changes are Visual Studio 2026 .slnx solution support in the editor and a switch to the UIScene lifecycle by default for iOS clients.

Highlights

  • Editor recognizes the Visual Studio 2026 .slnx solution format and reuses the running Visual Studio instance
  • iOS client now uses the UIScene lifecycle by default
  • ASDTool can generate SODBs for compute shader and bundled PSOs from a cooked game
  • Fixes for several crashes in Landscape, Modeling Tools, Media, MetaHuman and Movie Render Pipeline
  • Fixed a Lumen indirect lighting regression where the atlas was cleared every frame while a SceneCapture2D rendered Materials

Changelog

New6

  • UnrealBuildTool: PVS Studio can now work with different preprocessors
  • EOSSDK updated to v1.19.2.1 (binaries only)
  • iOS client uses the UIScene lifecycle by default
  • Added iPhone17e, new iPhone18Pros and new iPadAir devices to the base profile
  • ASDTool can generate SODBs for compute shader and bundled PSOs from a cooked game
  • Added ASD testing tools for local compilation and registration

Improved4

  • Editor now recognizes the .slnx solution format used by Visual Studio 2026, and opens the .slnx when both .slnx and .sln exist
  • Interchange USD import handles more primvar baking datatypes
  • Better validation of TMV transcode job lists imported from JSON
  • Improved D3D12 enhanced barriers implementation for compliance and correctness

Fixed15

  • Editor no longer opens a new Visual Studio 2026 instance each time it opens a source file
  • Fixed Open Solution toolbar button and saving open Visual Studio documents before a Hot Reload compile
  • Fixed crash when closing the editor while the sequencer tab was open
  • Fixed Mac/Linux editor crash on scripted Live Link Face ingest
  • Fixed Horde path traversal when extracting artifact and workspace contents
  • Fixed UAT garbled commandlet output on non-Latin codepage systems and a UAT log output stall
  • Fixed Mover crashes involving trajectory prediction from a worker thread
  • Fixed several Landscape crashes and asserts, including loading an old landscape without edit layers and undo
  • Fixed crash building a static mesh with no UV channels when MikkTSpace tangents are enabled
  • Fixed crash playing tiled TMV files larger than 8K through ImgMedia and a D3D12 crash with NDI sources
  • Fixed MetaHuman RigLogic twist angle extraction on fingers and a DNAIndexMapping crash
  • Fixed Movie Render Pipeline crashes with Object ID passes and with sequences without audio
  • Fixed Lumen regression that cleared the atlas every frame when a SceneCapture2D rendered Materials
  • Fixed shader preprocessor scanning past end of file on unclosed string/char literals
  • Fixed ChaosVehicles not receiving input with Physics Prediction enabled and an AIController driving

Before you upgrade

  • Known issue UE–401568: [PCG Editor Mode] Paint Tool fails to be updated in real time. Workaround: performing any other action makes the meshes appear.
  • If both a .slnx and a .sln solution exist, the editor now opens the .slnx; if only a .sln is present, it still uses that.
  • iOS clients now use the UIScene lifecycle by default.