Dataset Refresh REST API returns 415 "Model-based dataset" error

Since 2026-08-14, calling the Refresh Dataset REST API (POST /v1.0/myorg/groups/{workspaceId}/datasets/{datasetId}/refreshes) on any dataset in my tenant fails with:

HTTP 415 UnsupportedMediaType

{"error":{"code":"InvalidRequest","message":"Invalid dataset. This API can only be called on a Model-based dataset"}}

This happens even on datasets that refreshed successfully via this exact API for weeks before that date, without any changes to the dataset itself. Manual "Refresh now" via the Power BI portal UI still works fine on the same datasets — only the REST API call fails.

What I've already ruled out:

Not a client bug — reproduced identically with curl using the same bearer token, bypassing my application entirely.

Not just a POST/trigger issue — a plain GET /datasets/{id}/refreshes (listing refresh history) fails with the same error.

GET /datasets/{id} succeeds fine and returns "isRefreshable": false, even for a standard Import-mode, on-premises-gateway-connected dataset (targetStorageMode: Abf) that worked correctly before.

Not a capacity issue — my Fabric trial capacity shows Active/healthy.

Checked Service Health and Known Issues in the Admin Portal — nothing matching.

Possible trigger: the issue started the same day I added (then a few hours later removed) two unused Azure AD Application permissions (Tenant.Read.All, Tenant.ReadWrite.All) on my app registration for an unrelated experiment. It's been 3+ days since removing them and forcing a fresh sign-in, and the issue persists.

Has anyone else seen this, or does anyone know what could cause isRefreshable to flip to false tenant-wide like this? Happy to share more details (workspace/dataset IDs, full error bodies) if useful.