Claude Tag now writes 65% of Anthropic's engineering PRs, and the team's playbook is changing fast

Claude Code team at Anthropic says agents now write 65% of its product engineering PRs. The new bottleneck is taste.

The engineers building Claude Code just told a room full of software engineers what they do all day, and writing code was barely on the list.

At the AI Engineer World's Fair this month, Cat Wu and Thariq Shihipar from Anthropic's Claude Code team sat down with Simon Willison to describe how their day-to-day engineering workflow has changed. Claude Tag, Anthropic's new Slack-based collaborative coding agent, now lands 65% of the product engineering pull requests for the Claude Code team 1. Claude Tag launched roughly a week before the talk 1.

But the percentage is the least interesting part. What matters is how the team is rethinking the fundamentals of engineering practice, from when a full rewrite is worth doing to what skills separate good engineers from redundant ones.

Rewrites, reconsidered

Thariq's position: "rewrites are now good" 1.

His reasoning: a codebase is effectively a specification, and often the only copy of that specification that exists, because no single person understands every branch of it. The rewrite itself, he argued, forces the team to ensure it has a strong test suite 1.

Taste is the new constraint

Cat Wu described the shift in engineering skill sets as a swing away from execution and toward judgment. Two years ago, a product manager would spend six months aligning cross-functional teams, writing specs, and nailing down implementation details before the first line of code. Now, she said, the gap between idea and working software has compressed to as little as a week 1.

If execution is no longer the bottleneck, product taste and business judgment become the skills that differentiate engineers. "It's an increase in value on product taste and business sense, and a bit lower on execution in most product domains," Cat told the audience 1.

She drew a clear boundary. For infrastructure engineering, meticulous attention to detail still matters. The shift she describes applies to product engineering, where the cost of iteration has collapsed 1.

The instruction manual is shrinking, too

While the engineer's scope expands, the agent's system prompt is contracting. The team recently trimmed the Claude Code system prompt by 80% 1. Including worked examples in system prompts no longer improves results with current-generation models, and lists of negative instructions can actively degrade output quality 1.

The models have improved enough that elaborate scaffolding gets in the way. Anyone building agent workflows should take note: the prompt-engineering playbook from twelve months ago may now be working against you.

What Claude Tag does differently

Claude Tag lives inside Slack and operates differently from Claude Code's terminal interface. It is multiplayer by default, so multiple teammates can collaborate with the agent in a single channel. It is proactive rather than reactive: you can ask it to monitor bug reports and automatically open pull requests without tagging it in each time. And it carries persistent team memory, so preferences expressed once in conversation carry forward across sessions 1.

The team describes Claude Tag as the evolution of Claude Code, not a separate tool 1.

The companies optimizing for the wrong skill

Anthropic is the company building Claude. When the team creating the coding agent says 65% of its own product engineering pull requests are agent-written and tells its engineers to invest in product judgment over execution speed, the takeaway is not about productivity. It is about what an engineer becomes when the coding is handled.

The companies still optimizing for how fast engineers write code are optimizing for a bottleneck that the company automating that bottleneck has already removed from its own process. Cat's advice to the room was to build business sense and product taste 1. Infrastructure teams still need execution rigor. For everyone else, the job description is being rewritten in real time.