[Docmost - Unstable] File uploads failing with "Error processing file upload"

[hakunamatata]

I am testing the new unstable release of Docmost and encountering a consistent 400 Bad Request error when attempting to use the file attachment feature in the editor. The upload fails immediately, regardless of file size (tested with files as small as 30kb).

Environment:

Host: Cloudron 9.1.3
App: Docmost 0.70.3

Steps to Reproduce:

1. Install the unstable Docmost app.
2. Open any document and attempt to insert an attachment or image.
3. Select a small file (e.g., 30kb).
4. The UI throws an upload error, "Error processing file upload."

App Logs:
The logs show a clear BadRequestException indicating the storage backend is either unconfigured or inaccessible:

2026-03-22T16:08:56Z {"level":"error","time":"2026-03-22T16:08:56.462Z","pid":92,"hostname":"914b186f-aa30-4c30-929d-c63219d35ecf","req":{"method":"POST","url":"/api/files/upload","ip":"X.X.X.X","userAgent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.3.1 Safari/605.1.15"},"context":"AttachmentController","err":{"type":"BadRequestException","message":"Error uploading file to drive","stack":"BadRequestException: Error uploading file to drive\n    at AttachmentService.uploadToDrive (/app/code/apps/server/dist/core/attachment/services/attachment.service.js:176:19)\n    at async AttachmentService.uploadFile (/app/code/apps/server/dist/core/attachment/services/attachment.service.js:68:9)\n    at async AttachmentController.uploadFile (/app/code/apps/server/dist/core/attachment/attachment.controller.js:89:34)","response":{"type":"Object","message":"Error uploading file to drive","stack":"","error":"Bad Request","statusCode":400},"status":400,"options":{},"name":"BadRequestException"},"msg":"Error uploading file to drive"}
2026-03-22T16:08:56Z {"level":"error","time":"2026-03-22T16:08:56.462Z","pid":92,"hostname":"914b186f-aa30-4c30-929d-c63219d35ecf","req":{"method":"POST","url":"/api/files/upload","ip":"X.X.X.X","userAgent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.3.1 Safari/605.1.15"},"context":"AttachmentService","msg":"Error uploading file to drive:"}

Expected Behavior:
The app should successfully accept the file and store it in the designated local storage path within /app/data/.