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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
| Capture | Diagnostic value |
|---|---|
| Exact Unicode name and code points for it. | This identifies the exact object or resource generation involved and helps test the Windows cloud-file and sync-engine infrastructure boundary. |
| Normalized form for it. | This places the failure on the lifecycle or transaction timeline and helps test the Windows cloud-file and sync-engine infrastructure boundary. |
| Remote naming policy for it. | This separates caller input from environment and service state and helps test the Windows cloud-file and sync-engine infrastructure boundary. |
| Parent path and collision key for it. | This provides a stable comparison across retries or another machine and helps test the Windows cloud-file and sync-engine infrastructure boundary. |
Subsystem meaning
During a this result investigation, a Windows sync engine coordinates local NTFS objects, provider metadata, remote identifiers, quota and naming rules, placeholder hydration, network authentication, and asynchronous upload or download state. The same Explorer action can cross several of those boundaries, so diagnosis must retain the first failing stage rather than treating every code as a generic connectivity problem.
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.
The first owner to inspect is 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
When it is returned, use a disposable control object, repository copy, file, or device association where the subsystem permits it.
- 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
During a this result investigation, 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 input, fresh object or connection | If the result disappears, retained lifecycle or ownership state is implicated. | While diagnosing this result, keep the original data, account, device, or timeline parameters unchanged. |
| Same object, reduced operation | If the result follows one specific transition, statement, file, or ceremony step, the failure is localized. | While diagnosing it, remove only unrelated work and keep the first failing boundary visible. |
| Same stable item ID, second supported path | A change separates local file-system/provider state from remote service state. | While diagnosing it, 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
The references below define the API family or storage/protocol behavior used to interpret it.
- Microsoft: Build a Cloud Files sync engine
- Microsoft: Cloud Filter API reference
- Microsoft: Determine cloud placeholder state
- Microsoft: Restrictions and limitations in OneDrive and SharePoint
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