default agent setting

[aappddeevv]

I have both worktrees that I created and new ones that I want to create with sidecar.

I'd like to have a default agent set for both scenarios.

Right now, for an existing worktree, it seems to default to claude, but I want it to default to opencode. I'm unable to get a default agent set. I saw something about .sidecar-agent in the code (if it exists in an existing worktree then it would be used for the agent specification) but that did not seem to be honored.

It always seems to swerve towards claude.

[marcus]

Hey! Starling here (AI assistant on the project). 👋

Thanks for the detailed report — the .sidecar-agent mechanism is the right thing to try for this, so it's worth figuring out why it's not sticking.

A couple of questions to help narrow it down:

1. What content did you put in .sidecar-agent? The expected format should be just the agent name (e.g. opencode on its own line). Worth double-checking there's no trailing whitespace or extra characters.
2. Where is the file located? It should be in the root of the worktree directory itself (not in .sidecar/, not in your home dir).
3. For new worktrees — the agent is selected in the creation modal. Is it defaulting back to claude even when you pick opencode in that modal, or is it only reverting on subsequent launches?

Flagging this for @marcus since the .sidecar-agent file not being honored sounds like it could be a bug regardless of format — if the file is there and correctly formatted, sidecar should respect it. ✦

[aappddeevv]

.sidecar-agent is in the top folder of the worktree, a worktree I created).

For new worktrees it seems to start opencode ok assuming opencode is not already running on that worktree which sometimes it hangs and sometimes it tries to start claude, which fails since I don't have claude. It is a bit inconsistent.

[aappddeevv]

It would nice to have .sidecar-agent honored. It would be very nice if I can specify the opencode command to run inside of the agent file in some way so I could, for example, provide my args to it or start it differently e.g. "ocx oc -p ws" to start it. Otherwise, I'll be fiddling with aliases and shell scripts all day.

[marcus]

Thanks for the follow-up!

Good to confirm the file location is right — worktree root is exactly where it should be. The inconsistency you're seeing (sometimes opencode starts fine, sometimes it hangs, sometimes it tries to launch claude) does sound like a bug rather than a config issue.

One thing I still don't have: what's the actual content of your .sidecar-agent file? Just want to rule out a format mismatch (expecting opencode as a bare string vs. something else).

On the custom command/args idea — being able to write something like opencode -p ws directly into .sidecar-agent instead of just the agent name is a great ergonomics improvement, especially for opencode-only setups where you're customizing invocation. I've flagged that suggestion for @marcus.

The "tries to start claude when you don't have it" failure mode is the most pressing thing to sort out — I'll make sure that's front and center in the bug report. ✦

[aappddeevv]

content is plain text: opencode

[marcus]

Thanks — that confirms it. opencode as plain text in the worktree root is exactly the right format, so the file is correct and this is a genuine bug: sidecar isn't reliably reading .sidecar-agent for existing worktrees.

Flagging for @marcus with the confirmed details: file location ✓, file content ✓, behaviour is still inconsistent (sometimes works on new worktrees, sometimes hangs, sometimes falls back to claude). The missing-claude failure mode is the most disruptive since you get a hard error instead of a graceful fallback.

We'll get this tracked. Thanks for the patience debugging it! ✦