Neat! I did the Emacs equivalent https://github.com/xenodium/video-trimmer
From my experience, you kinda get what you ask for. If you don't ask for anything specific, it'll write as it sees fit. The more you involve yourself in the loop, the more you can get it to write according to your expectation. Also helps to give it a style guide of sorts that follows your preferred style.
Resume is supported by agent-shell, but is dependent on agent's to implement the relevant ACP. Do you know if OpenCode's ACP implementation has listing and resuming session support?
Also, you'll need to enable resuming as per post (it's a new feature) https://xenodium.com/agent-shell-0-47-1-updates
I put off adopting popular agents for most of 2025 primarily because there was no agent-agnostic path to first-class Emacs integration. That changed with ACP (https://agentclientprotocol.com), thus I started working on agent-shell.
I'm happy with how the integration is shaping up, enabling me to have my cake and eat it too (Emacs + AI agents).
I wrote an agent-shell post recently with the latest changes https://xenodium.com/agent-shell-0-47-1-updates