Summary
when i start a new session it hangs after a while, a dialog pops us saying “The application has hung and will now close. We apologize for the inconvenience.” , the wierd thing is that it worked in the beginning and works sometimes, im on win 10 and work with Claude code via the mcp.
Please select what you are reporting on:
Unreal Editor for Fortnite
What Type of Bug are you experiencing?
Stability
Steps to Reproduce
Heres a summary including steps from Claude:
[v42.00] Client “Hang detected on GameThread” kills UEFN edit sessions ~90-140s after InProgress — reproduces on an empty island
Summary
On v42.00 (++Fortnite+Release-42.00-CL-57316517), the Fortnite client raises
Hang detected on GameThread (thread hasn't sent a heartbeat for 45.00 seconds)
roughly 90-140 seconds after the match reaches InProgress in a UEFN edit session,
puts up the “application has hung and will now close” modal, and ends the session.
23 of 29 sessions failed this way over four days. It reproduces on a brand-new,
empty UEFN project with no content, so it is not project-specific.
Two important details:
- The game thread often recovers. In one case
RequestExitwas never issued,
the Valkyrie beacon stayed connected, and I played normally for 15 minutes with
the crash dialog still on screen. The stall is transient; the watchdog treats it
as fatal. - The modal blocks the game thread. The client log goes silent at the hang and
resumes only when the dialog is dismissed, so log silence is not thread death.
In ~2/3 of cases the server then shuts down (“no game clients connected”) within
35-45 seconds and the session is genuinely lost.
Repro
- Create a new UEFN project (blank island). No content, no Verse, experimental
toolsets/Python flags off. - Launch Session.
- Client joins, match reaches
InProgress. - 90-140 s later:
Hang detected on GameThread, modal appears.
Reproduced on a fresh project (ModuleVersion 1) as well as an existing one.
Client log
[2026.08.31-10.16.02:596] LogGameMode: Display: Match State Changed from WaitingToStart to InProgress
[2026.08.31-10.17.40:426] LogCore: Error: Hang detected on GameThread (thread hasn't sent a heartbeat for 45.00 seconds):
[2026.08.31-10.17.40:428] LogCore: Error: Hang detected on GameThread:
... FortniteClient-Win64-Shipping.exe!UnknownFunction [] (x26, unresolved)
[2026.08.31-10.18.24:439] LogBeacon: Online Beacon Failure: TransportError. beacon_client_connection_closed_remotely
[2026.08.31-10.18.24:497] LogValkyrieRequestManagerEditor: OnValkyrieBeaconNotifiedOfServerShutdown - game server was shutdown
CrashType=Hang. SecondsSinceStart across dumps: 174, 175, 185, 190, 192, 193,
200, 204, 207, 208, 213, 225, 272, 275.
The client is mid-GameFeaturePlugin activation when it stalls — failing runs
consistently reach ~2255-2276 transitioned successfully events before dying;
a surviving run reached 4164.
Crash GUIDs
UECC-Windows-AF92D4254D51A2400334C5BDC50D4C99
UECC-Windows-BB6F4D5049C7F94CF206B0872EFCFCB5
UECC-Windows-BEED6472479850984D5CAA803FF339BF
UECC-Windows-C3CD203D478D8F4F58ADBAA4CC01B9B7
UECC-Windows-C4412835496D2A8CD44E529A1891D756
UECC-Windows-CBEDE478453C4504CF0E79A6F4C982AA
UECC-Windows-D9238AC44B34F6EC559D76B24FAF5CE7
UECC-Windows-E51B5C4A4240EE27BBE629998FE60F5E
26 dumps total, all CrashType=Hang, 2026-08-28 to 2026-08-31.
Ruled out by direct testing
Each of these was tested individually and the hang still occurred:
- Project content — a brand-new empty island fails identically
- MetaHuman NPC and NPC Spawner (removed from level)
- Custom Verse
npc_behavior(yields correctly;Sleep()in all loops) - Imported animation assets
- Install location — SSD vs HDD (a clean 7-hour session ran from the HDD copy)
- CPU contention — other editors closed
- Parsec: service stopped, and its Virtual Display Adapter disabled in Device Manager
- Chrome Remote Desktop closed
- 3Dconnexion SpaceMouse software shut down
- RAM — 128 GB total, ~106 GB free, client peaked at 4 GB
- GPU driver — updated to 616.56 (cleared all
NGXLoadFromPath/DLSS errors; hang unchanged) - Deleting
%LOCALAPPDATA%\FortniteGame\Saved\Config(regenerates identically)
Game-feature load throughput is statistically identical between hung and clean
runs (peak transitions per 45 s window: hung 1159-2479, clean 1261-2386), so this
is not a slow-machine issue — the three fastest runs recorded all hung.
Environment
- Fortnite / UEFN
++Fortnite+Release-42.00-CL-57316517(installed 2026-08-26, unchanged since) - Windows 10 Home 19045
- AMD Ryzen 9 5950X, 128 GB RAM
- NVIDIA RTX 3090, driver 616.56 (32.0.16.1656)
- Install on NVMe SSD, Epic Games Launcher managed
Impact
Edit sessions are unusable for sustained work: ~2 in 3 attempts lose the session
within ~3 minutes of joining. Since the hang threshold isn’t configurable in the
shipped client, there is no client-side mitigation.
Suggestion
If the 45 s FThreadHeartbeat threshold is firing on a legitimately long
synchronous GameFeaturePlugin activation pass, consider amortizing that pass or
suspending the heartbeat around it — the thread demonstrably recovers when left
alone.
Expected Result
session loads fortnite splashscreen, dialog appears with ok button to close it, sometimes it hangs on splashscreen, sometimes it works anyway and is playable but dialog sits in background
Observed Result
session hangs so i cant testplay the level
Platform(s)
windows 10