POST /openai/v1/uploads returns HTTP 500 since 2026-09-28 (Foundry resource, japaneast), while /files works

Problem

Since 2026-09-28, every call to POST /openai/v1/uploads on our Azure AI Foundry resource fails with HTTP 500 (server_error). Retries over several days have not helped.

Environment

• Resource type: Azure AI Foundry resource
• Region: japaneast
• API: v1 (no api-version), API key authentication

What works and what fails (same resource and key, tested on 2026-10-03)

• GET /openai/v1/files: 200
• POST /openai/v1/files (purpose=assistants): 200
• POST /openai/v1/files (purpose=user_data): 201
• POST /openai/v1/vector_stores: 200
• POST /openai/v1/uploads: 500

The failure appears to be specific to the Uploads API.

Minimal repro

curl "https://<resource-name>.openai.azure.com/openai/v1/uploads" -H "api-key: $AZURE_OPENAI_KEY" -H "Content-Type: application/json" -d '{"purpose":"assistants","filename":"t.txt","bytes":5,"mime_type":"text/plain"}'

Response (HTTP 500):

{"error":{"message":"The server had an error processing your request. Sorry about that! ...","type":"server_error","param":null,"code":null}}

Request IDs

• c60e0f87-322a-4d29-991f-286ffe37783d (the minimal repro above)
• ae73dab4-55ef-4d76-bd5c-7819ae170694 (from our production traffic)

Notes

• The error message asks users to contact [email protected], but that address rejects external senders (550 5.7.133), so we could not report the issue there.
• We can work around it by switching to POST /files, but we would like to know the status of the Uploads API.

Questions

1. Is this a known issue with the Uploads API on Foundry resources (or in japaneast)?
2. Is there an expected time to resolution?