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RO_E_UNSUPPORTED_FROM_MTA
Single-threaded runtime class cannot be activated from the MTA
RO_E_UNSUPPORTED_FROM_MTA is HRESULT 2147483677 (0x8000001D) from winerror.h. The documented description is “Activating a single-threaded class from MTA is not supported.” The relevant context is the Windows Runtime metadata, object lifetime, asynchronous operation, activation, and apartment model.
The hexadecimal value and symbolic name of this result should remain attached to the originating API and operation instance.
Where it is encountered
- C++/WinRT, WRL, .NET projections, or native WinRT ABI calls.
- Runtime-class activation, WinMD reflection, asynchronous objects, observable state, or view lifecycle.
- Cross-thread and cross-apartment handoff between UI, ASTA, STA, MTA, broker, and background work.
The immediate focus is activation of a class whose threading metadata requires an STA while the calling thread is initialized as multithreaded.
What to verify
Verify that the runtime class threading model and current COM apartment were read from metadata and thread initialization, not inferred from symptoms. That condition determines whether the same object can continue, a new object is required, or policy must change.
Correct handling and recovery
Perform activation on an STA with a message pump, use an agile alternative, or redesign the worker boundary. Do not reinitialize an already configured MTA thread as STA.
Practical scenario
A service worker in the MTA activates a UI-oriented runtime class. The service moves activation to a dedicated STA and exchanges immutable data with the worker.
Difference from nearby HRESULTs
It rejects class activation from the MTA; RPC_E_WRONG_THREAD usually concerns later interface use on a different thread.
Developer and administrator guidance
References
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