Arialine
AI diagrams that live in your Slack threads
About Arialine
Arialine is a Slack app that turns the conversations your team is already having into diagrams that stay current. Instead of opening a separate whiteboard tool, exporting an image, and watching it drift out of date the moment the next decision lands, you mention Arialine in a channel, describe a system in plain language, and it posts the diagram straight back into the thread as both an interactive HTML file and a PNG. The problem it solves is a familiar one for engineering teams: architecture, data flows and runbooks are discussed in Slack, but the diagrams that capture them live somewhere else, so they rot. Arialine keeps the picture and the discussion in the same place, so the diagram is a living record of what the team actually decided rather than a snapshot nobody maintains.
What makes Arialine distinct is that it treats a diagram as a versioned object with a decision history rather than a static drawing. Every accepted change saves a new version instead of overwriting the last one, and Arialine keeps the Slack message that triggered that change attached to the version, so the question "why is this arrow here?" always has an answer. It is built on Mermaid, so valid Mermaid you paste renders exactly as written with no AI in the loop, while a plain-language request routes through AI generation. It won first place in Slack's Agent Builder Challenge for organizations, and it leans into Slack-native surfaces: channels, Canvases, global shortcuts and the Slack AI MCP server, so Slack AI itself can call Arialine as a tool.
You install Arialine into your Slack workspace and invite it to a channel. To create a board, mention Arialine with a sentence describing the system, or finish a discussion with a request to turn the thread into a diagram; Arialine writes the Mermaid, renders it, and posts an interactive HTML file plus a PNG back to the thread. To evolve a board, you keep talking: mention Arialine in the diagram thread with something like "add a caching layer" and it rewrites the Mermaid, renders a new version, and posts a one-line version reply with Undo and Rewind controls. Any teammate can react to a message to propose it as a change, which Arialine surfaces as an Apply, Edit or Dismiss card. Markdown files dropped into a channel are converted into Slack Canvases, with every Mermaid code block rendered as an embedded diagram. There are six entry points in total, from prompts and message shortcuts to the global shortcuts menu, and each one produces the same anatomy: a root message with controls, a version thread, and a decision ledger.
- •Diagrams From Slack Conversations - Mention Arialine with a plain-language description, or point it at an existing discussion, and it writes the Mermaid and posts an interactive HTML file and PNG back into the thread where the work is happening
- •Versioning With a Decision Ledger - Every accepted change saves a new version rather than overwriting, and the Slack message that caused it stays attached, with Undo, Rewind and Branch to navigate the history
- •Mermaid Native - Valid Mermaid you paste renders exactly as written with no AI involved, so teams that already write Mermaid get instant rendering, and AI generation is reserved for plain-language requests
- •Proposal Cards And Reactions - Any member can react to a message to propose it as a change, and Arialine posts an Apply or Dismiss card, letting a review end in a committed diagram without leaving the thread
- •Markdown To Canvas - Drop a Markdown file into a channel and Arialine converts it to a Slack Canvas with headings, lists and tables, turning each Mermaid block into an embedded diagram image
- •Slack AI And MCP - Arialine exposes an MCP server so Slack AI can call it as a tool, for example summarizing a discussion and turning it into a diagram in one request
Arialine is built for engineering teams that run their work in Slack and keep losing their diagrams to drift. It fits engineers and tech leads doing architecture reviews, where a proposed edit should land as an apply-or-dismiss card and the committed version should remember why it changed. It fits incident response, where a postmortem diagram needs to capture the observed failure and the agreed fix with the messages that drove them. It fits onboarding, where a new hire needs a current picture of how a system fits together rather than a year-old export. Because the Free plan includes every feature with up to three boards and ten AI generations per workspace a day, small teams and individual developers can adopt it without a purchase, while teams that make diagramming a daily habit move to the single Team plan for unlimited boards and generations. Anyone who already writes Mermaid and wants it rendered and versioned inside Slack, rather than in a separate tool, is squarely in the target audience.
