Learning Brief — 2026-09-21

What we covered

• AI news: AI & Tech Developments
• PM news: From Lenny's Newsletter: 🎙️ How I AI: Meta’s Muse review + How Warp ships 2,000 PRs a month with AI factories
• PM learning: From Lenny's Newsletter: 🎙️ How I AI: Meta’s Muse review + How Warp ships 2,000 PRs a month with AI factories

Mental model

Make the next experiment small enough to learn quickly.

Summary

The Verge — AI: California tightens rules on AI data center energy and water use. California Gov. Gavin Newsom has signed seven bills designed to prevent AI data centers from passing utility costs onto residents, as reported earlier by the Los Angeles Times. The package of laws requires the California Public Utilities Commission to introduce a new rate classification for data cen TechCrunch — AI: OpenAI forms math advisory group as its AI resolves more than 100 open problems. The group won't be given leeway to slow down or redirect OpenAI's ongoing mathematical research. TechCrunch — AI: Discover what’s next: 5 days left to save up to $200 on your TechCrunch Disrupt 2026 ticket. Five days left to save up to $200 on your TechCrunch Disrupt 2026 pass + 50% off a second one. Join 10,000+ founders, investors, and operators at San Francisco’s Moscone West, October 13-15. Grab your ticket savings before prices go up on September 25 at 11:59 p.m. PT. TechCrunch — AI: Meta’s Muse is outpacing ChatGPT’s early mobile launch. Meta’s new AI agent Muse has racked up more downloads and daily active users in the U.S. and Canada than ChatGPT did over the same period after its mobile debut, according to new estimates from Appfigures. TechCrunch — AI: Meta’s AI agent has been blocked from using Amazon.com. Amazon has its own cohort of foundation models, along with one of the most popular inference platforms on the internet. As long as they're under no legal obligation to open the doors to Muse, why would they? TechCrunch — AI: With Tabby, a former accountant is using AI to make accountants obsolete. Tabby is designed to be a real-time bookkeeping interface, handling clients’ paperwork as it gives them up-to-the-minute data on their business’s profit and loss.

Today's PM news comes from Lenny's Newsletter. The story is 🎙️ How I AI: Meta’s Muse review + How Warp ships 2,000 PRs a month with AI factories. For a senior PM, the key takeaway is to watch how product decisions and strategy plays out in practice — not just the headline, but the reasoning behind it.

Today's PM learning comes from Lenny's Newsletter. The core idea is 🎙️ How I AI: Meta’s Muse review + How Warp ships 2,000 PRs a month with AI factories. What matters for a senior PM is translating the idea into a repeatable habit: define the user problem clearly, pick a metric that actually reflects value, identify the riskiest assumption, and make the next experiment small enough to learn quickly. Good PM content is rarely magic. It is usually disciplined prioritisation dressed up in nicer prose.