ODP: [API Regression] Inconsistent driveId Casing Across Microsoft Graph API Endpoints

[abraunegg]

Summary

Since 14 June 2025 (possibly earlier), the Microsoft Graph API has started returning inconsistent casing for driveId values across multiple OneDrive Personal API endpoints.

This represents a behavioural regression from previously stable and predictable API responses where the driveId was always uppercase. The inconsistency now causes downstream failures for applications that treat driveId as a case-sensitive unique identifier.

Affected APIs

The issue is not isolated to GET /me/drive, but affects a wide set of endpoints, including but not limited to:

• GET /me/drive
• GET /me/drive/root
• GET /me/drive/root/children
• GET /drives/{driveId}/items/{itemId}
• GET /drives/{driveId}/items/{itemId}/delta
• parentReference.driveId
• item.id
• webUrl

Previously Expected Behaviour

{
  "id": "66D53BE8A5056ECA",
  "parentReference": {
    "driveId": "66D53BE8A5056ECA"
  },
  "webUrl": "https://my.microsoftpersonalcontent.com/personal/66D53BE8A5056ECA/Documents"
}

New and Inconsistent Behaviour

The same drive may now return mixed casing, even within a single response flow:

{
  "id": "d8ebbd13a0551216",                        // lowercase
  "parentReference": {
    "driveId": "d8ebbd13a0551216"                 // lowercase
  },
  "webUrl": "https://my.microsoftpersonalcontent.com/personal/D8EBBD13A0551216/Documents", // uppercase
  "item": {
    "id": "D8EBBD13A0551216!sea8cc6beffdb43d..."   // uppercase
  }
}

This inconsistent casing now appears across:

• Top-level id from /me/drive
• parentReference.driveId
• Embedded URLs
• Delta sync response IDs

Real-World Impact

• Sync clients and applications using driveId as a case-sensitive primary key are breaking or misbehaving
• Database lookups and ID comparisons fail due to casing mismatch
• Delta sync processes are impacted when driveId and item.id use differing case

Request for Resolution

1. Restore consistent casing (preferably uppercase) for all occurrences of driveId across the Microsoft Graph API.
2. Document whether driveId should be considered case-sensitive or not.
3. Ensure stability and predictability in identifier formats returned by the API.

Further Details

abraunegg/onedrive#3336