The harness is super important, what tools are available and the system prompts vary from harness to harness.

Anthropic seems to have a modest lead on their harness and models, so it’s a best-of-both-worlds scenario.

> I'm not sure what Microsoft is doing behind the scenes

It’s probably the exact same model, but the tools and the prompts around it are worse, so you get worse results.

Claude in Claude code has been shown to perform persistently worse in evals than claude + a minimal harness.

kilburn 4 hours ago | parent | prev | next [-]

The harness was absolutely not an issue in my case.

The new pricing model where I got banned from using Opus entirely and half a day of work (with weaker models) consumed the 10$ plan was.

I'm now using a Claude Max subscription and I can get close to the daily limits but I'm fairly happy with the overall plan consumption.

Vinnl 5 hours ago | parent | prev [-]

So if you use Claude via Copilot in Zed... You use Zed's harness, I think? What does Copilot do, at that point?

acpdev 5 hours ago | parent | next [-]

ACP is just a standard that bridges harnesses easily into IDEs, Text Editors, or whatever consumes it (I wrote a TUI that consumes them)

The registry for all the agents (tool harnesses) is here https://github.com/agentclientprotocol/registry if you ever are curious to what Zed or IntelliJ are really hooking into

	▲	Vinnl 2 hours ago \| parent [-]
		Ah OK, so the ACP connector ensures tool calls work with Zed, and communicates the available tools and their results to the harness, and then the harness mainly provides a system prompt and the API calls?

pantulis 5 hours ago | parent | prev [-]

It’s providing the inference of Anthropic models