Your hostile tone is unfortunate, especially since my post was actually friendly. I was just trying to point why it is very likely the OP won't give you what you're asking so you're not left confused if he ends up ghosting you.

Many people use the term harness to refer to the agent coding software (eg. Opencode, Claude Code...), i use this term more broadly to refer to the environment (set of skills, system prompts, constraints, memory, hooks etc...). What the OP is referring to is not just one giant skill. It's usually a comprehensive ecosystem of skills, bespoke tools to make certain agent tasks deterministic (eg localization), and so on.

I've seen someone post Github repos in this thread, these can be very useful especially if you use the same tech stack, but you won't reach the level of productivity reported by successful teams unless you invest substantial time to build your own harness. But the way to do so is to do it progressively : start with something simple to address the need you have on day 1 . And then, turn recurring prompts into skills, turn recurring coding patterns and coding style recommendations into guidelines, turn repetivive tasks for which the LLM tends to build a python script that it occasionally gets wrong into a deterministic tool documented in a skill etc...

And after a couple of days, weeks, and months, you'll have a very dependable harness giving you optimal productivity, without needing to invest weeks of work upfront or take the fun out of agent-assisted coding.

Hope this helps.