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REGDB_E_BADTHREADINGMODEL
Threading model entry is not valid
Windows defines REGDB_E_BADTHREADINGMODEL as 2147746134 (0x80040156; signed value -2147221162). AllStat’s description is “Threading model entry is not valid”. The code marks a specific failure: The InprocServer32 ThreadingModel registration contains an unsupported value. The relevant operation is loading an in-process COM server into a caller apartment.
The high bit in 0x80040156 is set, so this is a failure rather than a success or informational result. Its facility field is 4 (FACILITY_ITF) and its low 16-bit code is 342 (0x0156). Those bit fields classify the value, but they do not identify the failing object by themselves; the native method, object identity, and first producer of this result remain essential.
Where it is raised
Understanding this result requires this subsystem context: COM registration is architecture-, scope-, and identity-sensitive. A key visible in Registry Editor is not proof that the failing process sees the same view or that the values form a coherent activation contract.
- Associate this result with one exact operation in CLSID/IID registry lookup, InprocServer32 or LocalServer32 metadata, interface proxy registration, package policy, and threading-model interpretation.
- Confirm that this result came from loading an in-process COM server into a caller apartment, rather than from cleanup or a wrapper that ran afterward.
- Preserve any IErrorInfo, underlying Win32 result, provider message, or callback failure that preceded it; the HRESULT alone should not erase a more specific cause.
Telemetry checklist
A useful incident records the CLSID or IID, registry view, process architecture, user or machine hive, server path, ThreadingModel text, package identity, access result, and deployment version. Also retain the application and component build, architecture, process and thread IDs, COM apartment, operation correlation ID, elapsed time, and the first state-changing event before the failure. When logging it, redact content and credentials while preserving types, lengths, hashes, opaque identities, and lifecycle generations needed to reproduce its contract.
- capture the literal ThreadingModel text and the class CLSID.
- compare the server implementation with the apartment model it actually supports.
- test registration in a clean machine image to detect upgrade residue.
Why it is specific
- It can result when ThreadingModel is misspelled or contains an unrecognized custom value.
- It can result when manual registration writes a display label instead of Apartment, Free, Both, or Neutral.
- It can result when a package or installer merges incompatible registration fragments from different builds.
Investigation order
- Capture it at the first native return before a wrapper maps it to a generic exception.
- Identify the exact object, method, and lifecycle phase involved in loading an in-process COM server into a caller apartment.
- Reproduce it with one controlled input or state change, and verify that the correction changes the decisive evidence rather than merely hiding the result.
Safe handling
Correction. for it, repair the registration through the component installer and align it with the server’s real threading implementation. Retry boundary. Do not reinterpret the bad value or default silently; retry only after registration is corrected and the server is loaded in a new process. Before repeating the operation, complete or roll back the installer transaction, re-read the exact user or machine registry view, and discard class factories obtained from superseded registration.
Practical scenario
An installer writes “MTA” instead of the documented “Free” value; changing the authored installer data, not the application, resolves activation. This isolates it within COM registration database lookup and activation metadata and provides a regression test for the stated correction.
Difference from related HRESULTs
RPC_E_CHANGED_MODE concerns a thread already initialized with another apartment model; it concerns invalid server registration. Keep those outcomes separate in exception mappings, telemetry dimensions, user messages, and automated retry policy.
Developer and administrator guidance
Treat registration as deployment data, record architecture and scope on every lookup, validate ThreadingModel text, and avoid runtime self-repair that guesses missing keys. Regression coverage for it should include 32-bit and 64-bit views, per-user and per-machine registration, missing and malformed values, packaged and unpackaged activation, access denial, and upgrade rollback.
Operational repair for it must target the evidence-backed owner: use the product’s supported installer or package deployment path and inspect the same registry view as the failing process; do not create CLSID or IID entries from a different machine. Retain before-and-after traces for it so the change can be attributed and reversed.
References
- Microsoft: generic COM error codes
- Microsoft: HRESULT values
- Microsoft: registering COM components
- Microsoft: InprocServer32
- Microsoft: COM registry keys
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