What would make an existing OpenUI/Open WebUI user switch to this?
I've currently host both Open WebUI and Opencode on a server setup and there's multiple things that Open WebUI has implemented very nicely over time but it was also prior to the emergence of coding agents / harnesses. As such, its strengths is more on the `/chat/completions` era and RAG and its own functions and ecosystem setup before tool calls were a thing.
If this stuff works for you already, I think that's fine. That's not a bad thing, and if anything, they've made attempts to improve esp. with the recent backend upgrades and projects like `open-terminal`.
However, Opencode has been built for the coding agent setup since its early days and Odysseus gives me more confidence to run sessions much better knowing that it runs on an Opencode core.
Stuff like MCP support and a clearer lifecycle for example are things I've never really seen implemented well on open-webui (they've improved and support this now, but I'm biased and am salty of the era from its early days of MCP support when they insisted you place a bridge (mcpo) in between just to make it do MCP.). In contrast, opencode does this very well since what they built that works on the terminal also applies to the desktop app and the ACP support for IDEs that use it to connect to the opencode harness.
At the minimum, I expect Opencode to work wonderfully against the frontier models, and all models they host on their Zen and Go service, so that adds some confidence as well on complex workflows.
In contrast, I still find model management a pain in the ass on open-webui (has always relied on LiteLLM or a third-party inference gateway) just to wrangle the models. Hell, they still tag the Responses API "experimental" today, a format that's been around since over last year.
Does that transfer to Odysseus? Maybe, maybe not. Seems it's based on it but a quick check on code says they merely adapted it so maybe it's the latter. I haven't tried it at depth and idk how well Pewds has implemented it, but if it improves on that angle and gets maintainers that accepts contributions from the community, I feel like it'll do nicely.