| Previous | Next |
| UCEERR_INVALIDPACKETHEADER | UCEERR_ILLEGALPACKET |
UCEERR_UNKNOWNPACKET
UCEERR_UNKNOWNPACKET is a Windows User Composition Engine (UCE) HRESULT. It indicates that the rendering channel received a packet type that the active composition engine does not recognize.
What to check for UCEERR_UNKNOWNPACKET
- Check component and runtime version compatibility across the application and installed .NET or Windows updates.
- Look for custom interop, injected graphics components, or corrupted composition-channel traffic.
- Record the full exception stack and Windows build before attempting a retry.
Microsoft guidance for WPF render-thread failures
Diagnostic interpretation of UCEERR_UNKNOWNPACKET
UCEERR_UNKNOWNPACKET has the HRESULT value 0x88980401. AllStat records the condition as “UCEERR_UNKNOWNPACKET”. For UCEERR_UNKNOWNPACKET, in practice, interpret that wording at the boundary owned by the Windows component or COM interface that returned the HRESULT, rather than treating the value as a generic Windows message.
Evidence to capture for UCEERR_UNKNOWNPACKET
- Record the exact COM method or Windows API, its input object, the calling thread, and the full 0x88980401 value before a wrapper converts it to an exception or Boolean result.
- Capture any IErrorInfo text, activity identifier, event-log entry, and subsystem trace that mentions UCEERR_UNKNOWNPACKET or the uceerr / unknownpacket operation.
- Reproduce UCEERR_UNKNOWNPACKET with the smallest valid input and note whether the result changes with identity, architecture, service state, or target object.
Retry and recovery for UCEERR_UNKNOWNPACKET
Retry UCEERR_UNKNOWNPACKET only when the owning API documents a transient state or after the condition described as “UCEERR_UNKNOWNPACKET” has changed. For UCEERR_UNKNOWNPACKET, configuration, policy, format, and authorization failures normally require correction first; an immediate loop can hide the original call site and add secondary errors.
Looking for a different code? Search another status or error code.