What does HRESULT 0x8802C005 (E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE) mean?

E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE

The scope of E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE is Windows cloud-file and sync-engine infrastructure: downloaded content length did not match the size promised by the service or metadata. Preserve 0x8802C005 beside the returning call before cleanup or retry creates a more generic secondary failure.

Read the boundary first

When E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE is returned, 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. During a E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE investigation, 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.

During a E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE investigation, a size mismatch can indicate truncated transfer, stale metadata, wrong range handling, content transformation, or the item changing during download. For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, integrity should be checked before replacing a valid local version.

For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, 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.

Keep neighboring conditions separate

When E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE is returned, REQUEST_BLOCKED is a policy result; UNEXPECTED_SIZE means data arrived but violated transfer metadata.

For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, do not pad, truncate, or publish the staging file to make lengths match.

Incident record for this HRESULT

Reproduce without destroying evidence

For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, the investigation should change one variable at a time and keep the original failing sample.

1. First: Discard the incomplete staging file.
2. Next: Repeat against the same immutable remote version.
3. Then: Validate range and compression handling.
4. Finally: Commit locally only after size and integrity checks.

Three useful controls

• Second supported path for the same stable item: For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, a changed result separates retained object, connection, path, host, or device state from the original input. Hold constant: For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, keep account, remote item version, and client build fixed.
• Reduced failing operation: If E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE follows the reduced step, the rejecting transition is localized. Hold constant: For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, retain expected and received byte counts and remove only unrelated work.
• Targeted corrective control: Use this as a diagnostic branch rather than a blanket workaround: discard the incomplete staging file. Hold constant: For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE, keep the original E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE sample available for the final regression test.

Definition of done

Closure for E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE requires the immutable-version download matches size and integrity across full and ranged transfers; then repeat the next lifecycle operation to detect stale state.

Technical references

The references below define the API family or storage/protocol behavior used to interpret E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE.

• For E_SYNCENGINE_SERVICE_RETURNED_UNEXPECTED_SIZE: 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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