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E_SYNCENGINE_FILE_IDENTIFIER_UNKNOWN
E_SYNCENGINE_FILE_IDENTIFIER_UNKNOWN belongs to Windows cloud-file and sync-engine infrastructure. It marks the engine cannot resolve the file’s expected local-to-remote identifier mapping. The useful starting point is the exact API, object and state transition that returned 0x8802C002, because a shell or application message can hide that boundary.
Where this result is raised
Names and paths are not stable identities across rename, move and conflict resolution. A missing mapping can reflect stale metadata, a deleted remote item, or a local placeholder whose provider identity was lost.
Evidence worth collecting
- Local file ID and placeholder identity.
- Remote item ID.
- Rename/move history.
- Provider metadata and tombstone state.
A controlled diagnostic sequence
- First: Query placeholder/provider identity.
- Next: Reconcile by stable IDs, not only path.
- Then: Check remote deletion or replacement.
- Finally: Avoid assigning a new ID before conflict analysis.
How to interpret comparison tests
| 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. |
What this code does not justify
FILE_NOT_UPLOADED can lack a committed remote version; IDENTIFIER_UNKNOWN means the mapping expected by the engine cannot be resolved.
Do not match by filename alone and attach the item to an unrelated remote object.
Verification after correction
Treat it as corrected only when rename, move, delete and recreate tests maintain correct identity or produce an explicit conflict; retain the original negative case so fallback cannot be mistaken for repair.
Technical references
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