Rspamd
Rspamd 4.3 fixes SPF evaluation order and rejects weak DKIM keys, with results that change.
Comparison · Comms
Signal vs Slack
A side-by-side editorial comparison of Signal and Slack — release velocity, themes, recent moves, and the top alternatives to consider.
Signal vs Slack: at a glance
What is Signal?
Signal brings Secure Backups to every platform and starts automating key verification.
Signal Secure Backups improvements are now available on all platforms with iOS 8.30, a year after the feature's introduction. Android 8.20 and iOS 8.22 extended linked devices to Android phones, Android tablets and iPhones. Automatic key verification now complements safety numbers as a simpler way to confirm no unexpected party sits in a session.
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.
Signal vs Slack: editorial side-by-side
Signal
0.0COMMS
Signal brings Secure Backups to every platform and starts automating key verification.
◆ Current state
Signal Secure Backups improvements are now available on all platforms with iOS 8.30, a year after the feature's introduction. Android 8.20 and iOS 8.22 extended linked devices to Android phones, Android tablets and iPhones. Automatic key verification now complements safety numbers as a simpler way to confirm no unexpected party sits in a session.
◆ Where it's heading
The earlier alternation between protocol work and feature catch-up has narrowed into one theme: making multi-device life safe without asking users to do anything difficult. Backups, linked devices and automatic verification each remove a manual step or a reason to leave.
◆ Prediction
The entries are teasers and do not point to a specific next feature. Further multi-device polish looks most likely, since that is where the last three posts landed.
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.
Alternatives to Signal and Slack
Other Comms products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either Signal or 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.
See all Signal alternatives → · See all Slack alternatives →
Recent activity from Signal and Slack
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
- 1mo agoSignalBack to Backups: A Year in Review
- 3mo agoSignalIntroducing Automatic Key Verification
- 3mo agoSignalMore linked devices are on the table (and the Android tablet)
- 8mo agoSignalLabel yourself
- 9mo agoSignalPut a pin in it
- 0y agoSignalSignal Polls: Yes, no, maybe (yes!)
Frequently asked questions
What is the difference between Signal and Slack?
They serve adjacent needs but don't currently overlap on shipped themes. Slack is currently shipping more aggressively (velocity 6.3 vs 0.0), 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 Signal better than Slack?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Slack is currently shipping more aggressively (velocity 6.3 vs 0.0), 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 Signal?
Top Signal alternatives in Comms are ranked by recent ship velocity. Browse the "Signal alternatives" section above for the current picks, or visit /alternatives/signal for the full list with editorial commentary on each.
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.