I've been doing something pretty similar, except instead of having a persistent opencode server, I've been using this workflow that runs opencode inside of the Forgejo action runners:
Still tinkering with it, but the gist is that I can invoke Opencode with /oc inside of an Forgejo issue, then it will come back with a PR for me to review.
I did this with github actions + opencode. It has mainly two components called daydream and nightwatch. Daydream runs on a daily schedule looking at the VISION.MD file in the project and also look at the project and suggest new ideas, security , maintenance tasks (you can set a ratio of maintenance vs new ideas) and create a new issue. Then nightwatch runs daily at night and picks up oldest issue and suggest a PR. I'm in total control of merging, can ask for changes which agent again will execute immediately.
This has been helpful to revive few old projects and keep momentum on active projects. I've been closing more PRs than merging but I think that's fine. I quickly ran out of free github action hours so I had to self host actions. However basic self-host actions setup may not be secure enough because VM is not destroyed after each action like github own action jobs environment.
https://codeberg.org/dragonfyre13/forgejo-opencode
Still tinkering with it, but the gist is that I can invoke Opencode with /oc inside of an Forgejo issue, then it will come back with a PR for me to review.