What does HRESULT 0x800401EB (MK_E_MUSTBOTHERUSER) mean?

 
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MK_E_CANTOPENFILE MK_E_NOINVERSE

MK_E_MUSTBOTHERUSER

User input required for operation to succeed

MK_E_MUSTBOTHERUSER has hexadecimal value 0x800401EB (unsigned 2147746283, signed -2147221013). AllStat records “User input required for operation to succeed”. The narrow interpretation is that Binding cannot continue without explicit user input. The failing stage is resolving a moniker that needs credentials, media selection, confirmation, or another interactive decision.

The high bit in 0x800401EB 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 491 (0x01EB). 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.

API stage

Understanding this result requires this subsystem context: A moniker is an object with class-specific parsing, comparison, composition, and binding behavior. Display-name text alone does not establish what operations a particular moniker implementation supports.

  • Associate this result with one exact operation in IMoniker methods, IBindCtx state, display-name parsing, composite monikers, the Running Object Table, deadlines, and object or storage binding.
  • Confirm that this result came from resolving a moniker that needs credentials, media selection, confirmation, or another interactive decision, 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.

Verification steps

  1. Capture it at the first native return before a wrapper maps it to a generic exception.
  2. Identify the exact object, method, and lifecycle phase involved in resolving a moniker that needs credentials, media selection, confirmation, or another interactive decision.
  3. Record the nonsecret reason interaction is required and whether UI is available.
  4. Avoid logging credentials or sensitive display-name components.
  5. Separate headless-service behavior from interactive desktop behavior.
  6. Reproduce it with one controlled input or state change, and verify that the correction changes the decisive evidence rather than merely hiding the result.

Interpretation limits

  • It can result when authentication or consent cannot be obtained silently under policy.
  • It can result when multiple targets match and the user must choose.
  • It can result when required removable media, document location, or link repair needs user guidance.

Incident record

A useful incident records the moniker class, display name with secrets removed, bind options and deadline, pmkToLeft, requested IID, ROT result, file identity, composite components, and object lifetime registrations in IBindCtx. 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.

Recovery conditions

Correction. for it, surface a bounded, contextual prompt or return control to an interactive caller; fail cleanly in unattended execution. Retry boundary. Automatic retry without new user input is wrong; resume only after the requested decision is supplied and validated. Before repeating the operation, release partial monikers and bound interfaces, unregister only owned Running Object Table entries, and abandon a bind context whose deadline or parameters no longer match the retry.

Practical scenario

A link points to an offline protected share and no cached credentials are allowed; the desktop host prompts once, while a background service records a noninteractive failure. This isolates it within COM moniker parsing, composition, binding, and storage resolution and provides a regression test for the stated correction.

Difference from related HRESULTs

MK_E_CONNECTMANUALLY can require programmatic setup; it explicitly says user involvement is necessary. Keep those outcomes separate in exception mappings, telemetry dimensions, user messages, and automated retry policy.

Developer and administrator guidance

Preserve the concrete moniker class, compose through IMoniker methods rather than string concatenation, set realistic bind deadlines, and request object versus storage interfaces deliberately. Regression coverage for it should include malformed and class-specific display names, absent left-hand context, expired deadlines, unsupported inverse or enumeration operations, unavailable ROT objects, file access, and storage-only targets.

Operational repair for it must target the evidence-backed owner: verify the named resource, file, server, or registration identified by the concrete moniker; do not infer a machine-wide COM fault from one provider-specific display name. Retain before-and-after traces for it so the change can be attributed and reversed.

References

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