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E_SYNCENGINE_UNSUPPORTED_FILE_NAME
Within Windows cloud-file and sync-engine infrastructure, E_SYNCENGINE_UNSUPPORTED_FILE_NAME reports that the file name violates local or remote naming rules. Diagnosis of this result should follow the original owner and generation rather than treating the visible symptom as the cause.
Facts that change the diagnosis
- Exact Unicode name and code points.
- Normalized form.
- Remote naming policy.
- Parent path and collision key.
Subsystem meaning
A name can be valid on NTFS yet rejected by a remote service because of reserved characters, trailing characters, reserved device names, normalization, or service-specific policy.
Inspect the local sync root, placeholder state, file-system operation, provider request, network exchange, account policy, or remote storage operation that produced the HRESULT.
Isolation workflow
- First: Validate before creating the upload request.
- Next: Display the exact rejected component.
- Then: Test normalization and case collisions.
- Finally: Rename through a conflict-safe workflow.
Avoid the tempting broad fix
UNSUPPORTED_FOLDER_NAME applies to a directory component; the remediation can differ because renaming a folder changes descendants.
Do not log only a visually rendered name or strip characters silently.
Expected branches
| Control | Interpretation | Hold constant |
|---|---|---|
| Same stable item ID, second supported path | A change separates local file-system/provider state from remote service state. | Keep account, remote version and client build fixed. |
Regression proof
Verify it with the original scenario, one boundary case, and one deliberate failure; success means the validator matches service behavior for reserved, normalized, boundary-length and ordinary names.
Technical references
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