Show HN: Coasts – Containerized Hosts for Agents

>One thing I'm curious about: how do you handle state drift when agents are working on the same service across different worktrees? For example, if two agents are both making schema changes to a shared database service, do you have any coordination primitives, or is that left to the orchestration layer above? In my experience the runtime isolation is the easy part - the hard part is when agents need to share state (like a test database) without stepping on each other.

Great question! You can configure multiple coasts, so you could have a coast running with isolated dbs/state and also a shared version (you can either share the volume amongst the running coasts or move your db to run host-side as a singleton). So its sort of left to the orchestration layer: you put rules in your md file about when to use each. There's trade-offs to each scenario. I've been using isolated dbs for integration tests, but then for UI things I end up going with shared services.

>Re: For example, if two agents are both making schema changes to a shared database service

Obviously things can still go wrong here in the shared scenario, but it's worked fine for us and I haven't hit anything so far. It's just like having developers introducing schema changes across feature branches.

>Also, the per-service strategy config (none/hot/restart/rebuild) seems like the right abstraction. Most of the overhead in switching worktrees comes from unnecessary full restarts of services that don't actually care about the code change.

Totally, at first switching worktrees for our 1m+ loc repo was like 2 minutes. Then we introduced the hot/none strategies and got it down to like 8s. This is by far one of the best features we have.

Does it support native macOS containers?

[flagged]

We have been trying to solve the same problem (and a bunch of other ones) with https://specific.dev as well. We’ve tried to stay away from Docker as much as we can though because of the still pretty bad experience on Mac.

Our approach is having our CLI handle port assignments (and pass any connection details/ports along as env vars) and that way being able to spin up “isolated” copies of the local dev environment. Has the added benefit of us being able to deploy the same config straight to production and switch in production database connections strings and anything else needed.

Yes, exactly. Probably two different focuses between us, we are more focused on providing the full environment to build productively with coding agents, from local dev all the way to prod. The key thing for us is that the agent can write code, build infrastructure and test the entire system autonomously locally, and then deploying to production should be dead simple.

A bit of a different approach from the classic use case of docker-compose that is often orthogonal to the production infrastructure in some sense.

One thing I've used to great success though is taking an existing project or example docker-compose and simply asking the coding agent to translate it to Specific's IaC. Works a treat, especially as the coding agent can read all the code at the same time and connect it all together.

(also it looks like we were in the same batch!)