Background:

I'm working in a go mono-repo with multiple services:

/root
  .git
  go.mod
  /protobuf
    /definitions...
  /serviceA
    /handlers
    /businessLogic
    /externalDeps
  /serviceB 
    /handlers
    /businessLogic
    /externalDeps
  /commonlibs
    /logger
    /server
...

Plan

Open opencode in the /root directory
Spin up a session for /root/serviceA to implement a gRPC service.
Spin up another session for /root/serviceB to implement the gRPC client integration.
Use a third session for /root to run an acceptance test, since both will be in the agent's "view".

Outcome

The two sessions begin building independently.
Both make edits and get to a go build/test step, run go build ./... from the /root directory
Both builds find the same problems, some in each area of the code being worked
Agents start competing to edit the same code until I stop one (or both)

Question/Suggestion

Is there a clean way to set up this pair of agents without them getting in a code fight?
Can I do something like the aider --subtree-only option, but still allow read-only access to the rest of the repo?
Is there a way to change where the build/test tooling is executed within the session?