Rspamd
Rspamd 4.3 fixes SPF evaluation order and rejects weak DKIM keys, with results that change.
Comparison · Comms
Slack vs Zulip
A side-by-side editorial comparison of Slack and Zulip — release velocity, themes, recent moves, and the top alternatives to consider.
Slack vs Zulip: at a glance
What is Slack?
Slack now hosts any A2A agent without Slack-specific code.
Slack's developer channel is almost all agent plumbing. On 10 November Slack became an A2A (Agent2Agent) client: a team hosts its own agent, publishes an Agent Card, and Slack calls it when people talk to it, with no request URL, event handling or Slack-specific logic. This follows Slackbot skills managed through Web API methods, a Slack CLI that points coding agents to the Slack MCP server, and a new requirement that Work Objects embeds allow the slack-mcps.com frame ancestor.
What is Zulip?
Zulip donates itself to a nonprofit foundation as its founder joins Anthropic.
Two consequential moves landed inside three weeks. Tim Abbott, Zulip's longtime leader, is stepping back to join Anthropic along with three senior Kandra Labs engineers, and the for-profit company is being donated to a newly formed independent Zulip Foundation. In parallel, Zulip Server 12.0 shipped — roughly 5,500 commits, end-to-end encryption for mobile push notifications, a major Docker upgrade, and configurable image previews — alongside routine 11.x security patches and a self-hosted AI search integration via Atolio.
Slack vs Zulip: editorial side-by-side
Slack
6.3COMMSCOLLAB
Slack now hosts any A2A agent without Slack-specific code.
◆ Current state
Slack's developer channel is almost all agent plumbing. On 10 November Slack became an A2A (Agent2Agent) client: a team hosts its own agent, publishes an Agent Card, and Slack calls it when people talk to it, with no request URL, event handling or Slack-specific logic. This follows Slackbot skills managed through Web API methods, a Slack CLI that points coding agents to the Slack MCP server, and a new requirement that Work Objects embeds allow the slack-mcps.com frame ancestor.
◆ Where it's heading
Slack is lowering the cost of putting outside agents in front of its users: first skills as code, then MCP pointers for coding agents, now a standard protocol in place of the Slack app model for agents. The platform is positioning itself as the place where agents built anywhere meet the people who use them.
◆ Prediction
Expect more A2A follow-ups, such as agents appearing in Slackbot or skills surfaces and richer Agent Card features, given how fast the agent releases have stacked up since October.
Zulip
5.0COLLABCOMMS
Zulip donates itself to a nonprofit foundation as its founder joins Anthropic.
◆ Current state
Two consequential moves landed inside three weeks. Tim Abbott, Zulip's longtime leader, is stepping back to join Anthropic along with three senior Kandra Labs engineers, and the for-profit company is being donated to a newly formed independent Zulip Foundation. In parallel, Zulip Server 12.0 shipped — roughly 5,500 commits, end-to-end encryption for mobile push notifications, a major Docker upgrade, and configurable image previews — alongside routine 11.x security patches and a self-hosted AI search integration via Atolio.
◆ Where it's heading
Governance is being separated from product velocity: the foundation owns long-term stewardship while the technical roadmap (E2E push, self-hostable AI integrations, hardened install path) keeps targeting security-conscious, self-hosted teams. Losing the founder to a frontier AI lab is the kind of transition that either accelerates community ownership or stalls momentum — the 12.0 commit volume suggests the team built up runway before the announcement.
◆ Prediction
Expect the Zulip Foundation to publish formal governance, a maintainer charter, and a funding model in the next quarter, and for the AI integration story (Atolio-style connectors rather than first-party AI) to harden into Zulip's positioning against Slack and Mattermost's first-party AI bets.
Slack alternatives
Other Comms products tracked by Sparkpulse, ranked by recent ship velocity. Tap any card for the full editorial trajectory or compare directly with Slack.
Twilio
Twilio's voice AI stops cutting callers off mid-sentence, using its own turn-taking model.
Salesmsg
Salesmsg adds call-back requests and a one-click Emergency Stop for all outbound texts.
Element
Element 1.12.35 follows the call picture-in-picture release with one desktop storage fix.
Krisp
Krisp moves call transcripts and live captions to cloud transcription in KrispCX 2.84.4.
Misskey
Misskey 2026.11 ships: a leaner start script, and Node.js 22 no longer boots.
Zulip alternatives
Other Comms products tracked by Sparkpulse, ranked by recent ship velocity. Tap any card for the full editorial trajectory or compare directly with Zulip.
Interact
Interact opens its intranet to outside AI assistants and uses Claude to attack its own platform.
Nextcloud
Nextcloud's November patches lean on preview speed and sharing fixes across three branches.
Mattermost
Mattermost v12.1 puts bots and burn-after-reading messages under the same access rules.
Asana
Asana lets Division admins run their own custom roles, on top Enterprise plans only.
Double
Double turns a recorded Chrome session into an agent that repeats the task.
SiYuan
SiYuan 3.8.11 alphas add freeform mind maps and plugin snapshots right after 3.8.10.
Recent activity from Slack and Zulip
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 4d agoSlackBring your A2A agents to Slack ⚡
- 8d agoSlackWork Objects embeds require the slack-mcps.com frame ancestor
- 10d agoSlackSlack CLI 4.13 tells coding agents about Slack MCP and Skills
- 10d agoSlackSlack Skills Plugin installs in Claude Code from its own marketplace
- 12d agoSlackUpdated low-usage submission criteria for Slack Marketplace apps
- 15d agoSlackSlack CLI 4.12.0, the fourth CLI release in October
- 6mo agoZulipAnnouncing the Zulip Foundation ⚡
- 6mo agoZulipZulip 12.0: Organized chat for distributed teams ⚡
- 7mo agoZulipZulip integrates with Atolio's self-hosted AI search platform
- 7mo agoZulipZulip Server 11.6 security release
- 7mo agoZulipWe released Zulip Server 11.6 today!
- 9mo agoZulipZulip Server 11.5 security release
Frequently asked questions
What is the difference between Slack and Zulip?
They serve adjacent needs but don't currently overlap on shipped themes. Slack is currently shipping more aggressively (velocity 6.3 vs 5.0), with 1 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is Slack better than Zulip?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Slack is currently shipping more aggressively (velocity 6.3 vs 5.0), with 1 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other Comms products to evaluate alongside.
What are the best alternatives to Slack?
Top Slack alternatives in Comms are ranked by recent ship velocity. Browse the "Slack alternatives" section above for the current picks, or visit /alternatives/slack for the full list with editorial commentary on each.
What are the best alternatives to Zulip?
Top Zulip alternatives in Comms are ranked by recent ship velocity. Browse the "Zulip alternatives" section above for the current picks, or visit /alternatives/zulip for the full list with editorial commentary on each.