Turns out it wasn't Opencode Go, Cloudflare was intermittently blocking Hermes's User-Agent apparently. Config change fixed it. (Would not run into this without Hermes but Hermes did fix it using the local model.)
I have been setting up local models and settled on Swift Qwen 3.8 27B 4-bit. Got it running since earlier today in a setup I can start trying with coding agents, starting Monday probably. Today it already proved useful when Opencode Go started failing on me (while using Hermes).