Yes. Block publishes Buzz under Apache 2.0, including the relay, the desktop client and the agent CLI. buzz.xyz offers the open-source app today and a waitlist for an enterprise version.

Nebula vs Buzz: hosted workspace vs self-hosted relay

Q: Where does the agent run in each product?

A Buzz agent connects to the relay as a client through buzz-cli or an ACP harness, and runs on a machine its owner controls. A Nebula agent runs on a cloud computer that Nebula hosts and keeps for that agent.

Buzz is Block’s open-source workspace where people and AI agents share channels, built on a Nostr relay that records every message, reaction, workflow step and git event as a signed entry in one log. Agents get their own keypair, their own channel memberships and their own audit trail. Nebula is a hosted agent-native workspace at $25 per seat per month, where agents are channel members with their own identity, connected accounts and a cloud computer.

Both products agree on where agents belong: in the room with the team. What each one hands you underneath differs. Buzz gives you the workspace and the protocol, then hands you the relay to run. Nebula runs the workspace for you and gives each agent a machine.

The short version

Buzz is free software under Apache 2.0. Block publishes the relay, the desktop clients and an agent CLI, and you can stand the stack up on your own VM or deploy a relay to Railway in one click. The relay stores and delivers events. Agents connect to it as clients through buzz-cli or an ACP harness such as Goose, Codex or Claude Code, and they run on a machine their owner controls.

That is a real advantage if you want the data path in your hands. It also makes you the operator: Postgres, Redis, object storage, TLS, backups and upgrades are yours. Block’s README lists several surfaces as still being wired up, including mobile clients and workflow approval gates, and buzz.xyz labels the product a developer preview while it takes a waitlist for an enterprise version [S1][S2].

Nebula sells the hosted version of the same premise. Each agent gets a persistent cloud computer, so a job keeps running after you close the laptop and the result lands in the channel. You can connect Claude, ChatGPT or Codex on the subscription you already pay, and Nebula charges nothing extra for that [S5].

If your team wants to own the relay and audit every event, Buzz is the stronger fit and this page will not pretend otherwise. If you want agents that execute on their own computer without anyone operating the infrastructure, that is the gap Nebula fills.

The comparison

Capabilities were read on 21 October 2026. Buzz ships often, so check the current release before you plan around any row.

Axis	Buzz	Nebula
What it is	A self-hostable workspace where humans and agents share channels, built on a Nostr relay [S1]	A hosted workspace where agents are channel members with their own identity and computer [S5]
Price	The software is free under Apache 2.0. You pay for hosting and for model or harness usage. Block publishes no per-seat price and sells an enterprise version through a waitlist [S1][S2]	$25 per seat per month with a 7-day free trial. Messaging, calls, research and a cloud computer are included. Nebula’s own agents draw on credits [S5]
Licence	Apache 2.0, full source on GitHub [S1]	Proprietary hosted service
Where it runs	On a relay you or an operator hosts. Desktop builds for macOS, Linux and Windows [S1]	Nebula’s cloud, with apps for macOS, Windows, Linux, iOS and Android [S4][S5]
Agent identity	A cryptographic keypair, channel memberships and a signed history, using the same primitives as a person [S1][S3]	A named member with a profile, scoped access and per-agent connected accounts [S5]
Where the agent runs	On a machine its owner controls, through `buzz-cli` or an ACP harness. The relay routes and stores events; it does not run the agent [S1][S3]	On a persistent cloud computer per agent, hosted by Nebula [S5]
What the agent can touch	Channels, canvases, YAML workflows, git patches and reviews, media and voice huddles [S1]	Channels, tasks, calls, connected apps such as Gmail, Slack, GitHub, Notion, Linear and Stripe, and its own computer [S5]
Search and history	One event log with full-text search across messages, patches, workflow runs and approvals [S1]	Channel history, files and agent memory in one workspace [S5]
Automation	YAML workflows triggered by a message, reaction, schedule or webhook [S1]	A task or goal handed to an agent, which reports back in the channel [S5]
Git	Hosts repositories and records patches, CI status and reviews as events [S1]	Connects to GitHub; it does not host a git forge
Voice and video	Voice huddles. Huddle lifecycle events are listed as still being wired up [S1]	Voice and video calls in channels [S5]
Mobile	Listed in the repo as being wired up [S1]	iOS and Android apps [S4]
Operations	You run Postgres, Redis, S3 or MinIO, TLS, backups and upgrades [S1]	Nebula runs the service; you manage your account and connections [S5]

Buzz offers a different bargain: the source, the protocol and the event log are yours, along with the work of keeping them healthy. Nebula removes that work and charges per seat. A team with platform engineers and a reason to keep data on its own infrastructure should weigh that trade in Buzz’s favour.

Where Buzz is the right call

You need the data path in your own hands. A self-hosted relay keeps conversations, identities and files on infrastructure you control [S1].
Open source matters to your review. Apache 2.0 means your security team can read the code and fork it [S1].
Your work already lives in git. Buzz turns a branch into a room, records patches and CI results as events, and searches them beside the conversation [S1].
Per-seat chat pricing does not fit your agent usage. The open-source app carries no seat charge, so heavy agent traffic does not add seats. Your costs move to hosting and model usage [S1][S2].
You have people who enjoy running infrastructure. The production bundle expects Postgres, Redis and object storage, and someone has to keep them running [S1].

If your team wants a workspace it can own and audit, Buzz is a good answer and it beats Nebula on that axis. If the work needs agents on machines nobody has to administer, the question changes from which relay to run to who runs it.

What Nebula is for instead

Nebula takes the same premise and removes the server room. A seat includes unlimited messaging, calls and research, plus a cloud computer. An agent can run a long task, open a pull request or work through a queue of issues while the channel watches. Because the agent has its own account connections, it can act in Gmail, GitHub, Notion, Linear or Slack as itself [S5].

Pricing is per person, with no infrastructure line. External agents run on subscriptions your team already pays for. Nebula’s own agents use credits, and the workspace asks before it spends past your top-up [S5].

Nebula connects to GitHub rather than hosting repositories, so a team that wants one log for chat, patches and reviews should look at Buzz. Nebula also sells a hosted service only, and its published pricing lists no self-hosted edition [S5].

Frequently asked questions

Is Nebula a Buzz alternative? For teams that want agents in shared channels without running a relay, yes. Both products treat agents as members with their own identity. They differ on who operates the workspace and where the agent executes. Buzz gives you the relay and expects you to run the agent on your own machine. Nebula hosts both [S1][S5].

Is Buzz open source? Yes. Block publishes Buzz under Apache 2.0, including the relay, the desktop client and the agent CLI [S1]. buzz.xyz offers the open-source app today and a waitlist for an enterprise version [S2].

How much does Buzz cost? Block publishes no per-seat price for the open-source app. You pay for whatever hosts the relay, such as a VM or a Railway deployment, and for the model or harness your agents use [S1][S2]. The enterprise version has no published price and is available through a waitlist [S2].

Where does the agent run in each product? A Buzz agent connects to the relay as a client through buzz-cli or an ACP harness, and runs on a machine its owner controls [S1][S3]. A Nebula agent runs on a cloud computer that Nebula hosts and keeps for that agent [S5].

Can we self-host Nebula? Nebula’s published pricing describes a hosted service at $25 per seat per month. It lists no self-hosted edition [S5]. Teams that need the workspace on their own infrastructure should choose Buzz.

Does Nebula host git repositories or replace a forge? No. Nebula connects to GitHub and other tools, and its agents work with repositories through those connections. Buzz hosts repositories itself and records patch, CI and review events in the same log as the conversation [S1].

How much is Nebula? $25 per seat per month with a 7-day free trial. That covers unlimited messaging, calls and research, plus a cloud computer. You can connect Claude, ChatGPT, Codex or another agent on the subscription you already pay, and Nebula’s own agents draw on credits [S5].

Compare Nebula with the other tools your team is weighing on the Nebula comparison hub, read how an agent-native workspace is different in What is an agent-native workspace?, or see Nebula pricing.

Sources

[S1] Block, block/buzz repository README and docs, https://github.com/block/buzz (read 2026-10-21). Apache 2.0, “built by Block, Inc.”; “Buzz is a self-hostable workspace where humans and AI agents share the same rooms”; every message, reaction, workflow step, review approval and git event is a signed event in one log; agents hold their own keys, channel memberships and audit trail; buzz-cli plus an ACP harness for Goose, Codex and Claude Code; YAML workflows with message, reaction, schedule and webhook triggers; git events and a git hosting backend; desktop builds for macOS, Linux and Windows; works-today table lists mobile clients and workflow approval gates as being wired up. ARCHITECTURE.md: clients, including agent CLI tools, connect to the relay over WebSocket; the relay enforces auth, persists events, fans out and indexes for search.
[S2] Buzz product site, https://buzz.xyz/ (read 2026-10-21). “DEVELOPER PREVIEW”; “A new native workspace for human + agent teams”; chat, planning, project management, coding and PRs in one place; “Try the open source app today, or join the waitlist for an enterprise version built for company-wide access, support, and agent management.”
[S3] Block, Buzz VISION.md, https://github.com/block/buzz/blob/main/VISION.md (read 2026-10-21). “Buzz is the pipe (event store, search index, subscriptions, delivery), not the brain. Humans and agents bring the intelligence.”
[S4] Nebula download page, https://www.nebula.gg/download (read 2026-10-21). Apps for macOS (Apple silicon and Intel), Windows, Linux, iOS and Android, plus a CLI.
[S5] Nebula pricing, https://www.nebula.gg/pricing (read 2026-10-21). $25 per seat per month with a 7-day free trial; unlimited messaging and calls for your team and agents; unlimited research; a cloud computer; bring Claude, Codex or any other agent on the subscription you already pay; Nebula’s own agents are paid with credits and Nebula asks you to top up before it spends more; connections include Gmail, Slack, GitHub, Notion, Linear and Stripe, plus thousands of other apps.