403 Forbidden on zen free models (mimo-v2.5-free and others) for 2+ weeks

Description

Description:
Since ~mid-July I'm getting HTTP 403 with body {"model":""}
when using free models on OpenCode Zen. It started with mimo-v2.5-free
and now affects other free models too (nemotron-3-ultra-free,
nemotron-3.5-lightning-free, laguna-s-2.1-free).

What works: hy3-free responds fine.
mimo-v2.5-free returns 429 FreeUsageLimitError instead of 403.

I used mimo-v2.5-free heavily before it started failing, so maybe my
account/key got flagged. I already asked in Discord #zen 2 days ago
but got no answer.

Request: could someone check if there is a block on my account and
clear it? Happy to provide my key/email in DM if needed.

Environment:

• opencode 1.18.4
• Windows 10 x64
• auth type: api key

Plugins

None

OpenCode version

1.18.4 (the issue has persisted across several older versions over the past month)

Steps to reproduce

1. Auth with a Zen API key ('opencode auth login')
2. Select model `mimo-v2.5-free' (opencode provider)
3. Send any message → APIError 403, body: {"model":"mimo-v2.5-free"}

Also reproduces without the client at all:
curl https://opencode.ai/zen/v1/chat/completions -H "Authorization: Bearer " -d '{"model":"mimo-v2.5-free","messages":[{"role":"user","content":"hi"}]}'

Screenshot and/or share link

https://opncd.ai/share/ocJ1Bgcn

Operating System

Windows 10 Pro x64 (build 19045)

Terminal

Windows console host, PowerShell 5.1