Block built a Slack for AI agents — and gave each one its own passport

Block spent Tuesday introducing Buzz, a free, open-source workspace that looks a lot like Slack or Discord at first glance — channels, threads, direct messages, voice, code repos, the works. The twist is what sits underneath: Buzz runs on Nostr, the decentralized protocol Jack Dorsey has backed for years as a censorship-resistant answer to Twitter, and it treats AI agents as full members of the conversation rather than bolted-on bots. Plug in Claude Code, Codex, Block's own goose, or whatever harness a team prefers — Buzz doesn't care which model is doing the work.

What makes the identity system interesting is the layering. On Nostr, everyone is fundamentally just a public-private keypair, and Buzz gives agents their own keypair just like a human would have. But then it adds one more signed message on top, linking that agent's key back to its human owner. Bradley Axen, Block's head of AI capabilities, describes it as a cryptographic paper trail neither party could produce alone — proof that a given agent belongs to a given person, checkable by anyone else in the workspace. That paper trail is what lets a team gate a private channel to only agents owned by members. Block has pitched the scheme as an upstream Nostr extension, though it hasn't been adopted yet.

Axen's real complaint is about a conversation that currently vanishes. Teams post a task, then disappear for an hour to work with an agent one-on-one, and whatever gets decided in that stretch — the actual technical reasoning — never makes it back into the shared channel except as a pasted summary. That's the gap Buzz is trying to close by making agents visible participants instead of black boxes people report back from.

Running Buzz requires a Nostr relay, and Block is emphatic that teams can host their own with zero traffic touching Block's infrastructure — Axen likens it to a Discord server nobody company owns. Even so, Block spent its final pre-launch weeks building a hosted relay option anyway, betting most teams would rather not manage that themselves. That hosted tier is free for now, which Axen frames as a beta with no usage limits set yet, though he's already flagging that a small open-source project is cheap to host while an enterprise-grade Slack replacement is a different cost equation entirely.

Buzz isn't Block's first swing at agent tooling. The company open-sourced its goose agent framework back in January and it's since collected more than 50,000 GitHub stars; internally, a system called BuilderBot handles over 200,000 operations a day and merges roughly 1,500 pull requests a week, accounting for about 15 percent of Block's production code changes. Buzz, by contrast, has only pulled in just over 100 stars since its code went public earlier this year — a reminder that this is very early days for a tool asking teams to rethink where their agents actually talk.

All of this lands against the backdrop of Block cutting more than 40 percent of its staff in February, shrinking from over 10,000 employees to just under 6,000, with Dorsey pointing to AI as enabling what he called a new way of working. Buzz reads like the collaboration layer built for whatever comes after that shrinking — a workspace sized for a company doing more with fewer people in the room.