App freezes when running in Rosetta simulator on Xcode 26 (works on device and ARM simulator)

Developer Tools & Services Xcode
Philipss OP
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Hello,

We are experiencing a recurring issue when running iOS apps in the Rosetta simulator on Xcode 26.

Environment:

  • Xcode: 26.0
  • macOS: 15.7.3
  • Simulator: Intel-based (Rosetta) simulators
  • Languages: Both Swift and Objective-C

Issue: When launching an app in a Rosetta simulator, the app frequently freezes or fails to run. In many cases, Xcode reports that the debugger has lost connection.

Xcode error message:

Lost connection to the debugger on “iPhone 12”.
Domain: IDEDebugSessionErrorDomain
Code: 22
Failure Reason: Message from debugger: lost connection

Console log:

assertion failed: GPR thread_set_state is unimplemented for NewThread
(ThreadContextRegisterState.cpp:920 host_gpr_state_from_guest_state)

Observed behavior:

  • Rebuilding after fully quitting the simulator sometimes resolves the issue temporarily.

  • Disabling Scheme > Run > Debug executable allows the app to run normally, but debugging (breakpoints, etc.) becomes unavailable.

  • The issue does not occur:

    • On real devices
    • On ARM-based simulators
    • When building with Xcode 16 using Rosetta

Has anyone encountered this issue with Xcode 26 and Rosetta simulators? Is this a known bug, and are there any recommended workarounds besides disabling the debugger or restarting the simulator?

Thank you in advance for any insights or guidance.

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App freezes when running in Rosetta simulator on Xcode 26 (works on device and ARM simulator)
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