You can get a lot done with agentic programming without going "all in" on a gastown-like system, but I think there is a minimum viable setup:
1. an adversarial agent harness that uses one agent to create a plan and implement it, and another to review the plan and code-review each step.
2. an agentic validation suite -- a more flexible take on e2e testing.
3. some custom skills that explain how to use both of those flows.
With this in place you can formulate ideas in a chat session, produce planning artifacts, then use the adversarial system to implement the plans and the validation layer to get everything working e2e for human review.
There are a lot of tools you can use for these things but I chose to just build the tooling in the repo as I go.
Claude already creates multiple agents for some projects just to keep context windows smaller. I don't think it'll be long before they offer a testing agent along with their planning agent.