Compare
RFC123 vs. Slack Canvases
Slack Canvases are documents that live inside Slack – in a channel, a DM, or the workspace at large. They’re great when discussion is already happening there and you need a shared scratchpad fast. RFC123 is for the next step: when the decision matters enough that you’ll want to find it again in a year.
Where Slack Canvases is better
- Zero context switch. The doc lives in the channel where the conversation is already happening. RFC123 takes you to a new tab.
- Lowest possible friction. Promote a thread to a canvas in one click. RFC123 makes you pick a repo and write Markdown.
- Workspace-wide access. Anyone in your Slack can read and comment – no extra account, no permissions to grant.
- Slack-native interactions. @-mentions, reactions, emoji, file uploads, threads – all the affordances people already use, with no relearning.
- Mobile parity. You’re already on Slack mobile. RFC123 is desktop-first.
- Lightweight by design. Right for ephemeral thinking before anything is “official”.
Where RFC123 is better
- Durable record. A canvas’s home is a Slack channel. An RFC’s home is your code repo – still there when the channel is archived and the workspace is migrated.
- Versioning. Track how the proposal evolved across drafts. Canvases have a single timeline.
- Line-anchored comments that stay anchored.Comments in a long canvas tend to scroll out of context. RFC123 lines threads up next to the lines they’re about.
- Cross-repo review queue. A digest of RFCs awaiting your review across every repo you can access – opt-in to Slack, scoped to your reviews, not “anywhere you were mentioned”.
- Permission model that follows the code.Access mirrors the repo, not “who happens to be in the workspace today”.
- Agents can read it without being in Slack.MCP server exposes RFCs to Claude, ChatGPT, or any agent – with skills for pressure-testing, synthesis, and comparing to the codebase.
Side-by-side
| Feature | Slack Canvases | RFC123 |
|---|---|---|
| Time to first draft | Seconds, in-thread | A minute – pick repo, write Markdown |
| Versioning / diff | Single timeline | Git history: commits, authors, diffs |
| Comment anchoring | Block reactions / threads | Line-level threads on rendered Markdown |
| Lives where conversation is | Yes (channel / DM) | Separate, with optional Slack briefing |
| Discoverable in 12 months | Channel-dependent | Yes – PR in your repo |
| Permissions | Slack workspace / channel | GitHub repo |
| Mobile | Strong | Limited |
| Agent / MCP access | Limited | Yes – read-only, with skills |
| Markdown export | Possible | Native – RFCs are Markdown files in your repo |
| Lock-in | Slack workspace | None – RFCs are PRs in your repo |
So which one should you pick?
Pick Slack Canvases if
- You’re in the very early stages and the doc is a thinking space, not a decision.
- Your team is small enough that everyone reads everything.
- The right home for the doc is the channel where it’s being discussed.
Pick RFC123 if
- The decision is worth finding again next quarter.
- Multiple repos or teams need to weigh in on the same proposal.
- You want diffable history of how the proposal changed.