add(foundations): WebSub — push notification for feeds - #136
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WebSub was republished as a W3C Recommendation on 2 June 2026 (new XSS mitigations in Security Considerations), and the repo had no page for it despite covering feed discovery and feed hygiene. rel="hub" and rel="self" are both IANA-registered link relations and auditable from outside the site, so this is a website property rather than a build technique. Status: optional — it only applies if you publish a feed and have a hub to point at; the platform does not break without it. - new page src/content/spec/foundations/websub.md (order 130, after feed-discovery/110 and feed-hygiene/120) - relatedSlugs wired on feed-discovery, feed-hygiene and link-headers - changelog entry 2026-07-30-websub.md - OG images regenerated; SKILL.md page count 164 -> 165 + digest resigned Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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What changed
New spec page:
foundations/websub— the publisher's side of WebSub. Advertiserel="hub"andrel="self"on your feed, ping the hub on publish, and subscribers get pushed each update instead of polling for it.Also in this PR:
relatedSlugswired onfoundations/feed-discovery,foundations/feed-hygieneandagent-readiness/link-headers.2026-07-30-websub.md(added).public/og/spec/foundations/websub.pngplus the four count-driven images).SKILL.mdpage count 164 → 165 andagent-skills/index.jsondigest re-signed vianpm run sign:skill.Why now
Found by the daily standards scan sweeping the W3C TR index. WebSub was republished as a W3C Recommendation on 2 June 2026, adding cross-site-scripting mitigations to its Security Considerations (subscribers must serve the intent-verification response with a safe media type and
X-Content-Type-Options: nosniff). The repo covers feed discovery and feed hygiene but had no page on the push half of the story —grep -ri websub src/contentreturned nothing.Why it earns a page
Per the scan's "auditable website outcome, not build technique" rule:
rel="hub"andrel="self"are IANA-registered link relations served in yourLinkheaders or feed, so the capability is checkable from outside the site. The "Why it matters" is phrased for subscribers and agents, not for the developer — latency drops from polling interval / 2 to seconds, and the polling traffic that dominates most feed URLs disappears.Status
optional. It only applies if you publish a feed and have a hub to point at; the web platform contract does not break without it. Same bar asimage-sitemapsandidn-support.Note for the maintainer
This site does not ship a WebSub hub, so the page carries no worked-example callout. Reading it against "ship it before you spec it": WebSub is not a brand-new convention needing us to prove feasibility — it has been a W3C Recommendation since 2018 and descends from PubSubHubbub (2009) — and the repo already documents plenty of established standards the site itself doesn't implement (
well-known/webauthn,well-known/oauth-authorization-server,well-known/apple-app-site-association,accessibility/captions-and-transcripts). If you read that rule more strictly, say so and I'll close this in favour of a Slack flag.The page deliberately covers only the publisher's obligations, so the 2026 XSS mitigation — a subscriber obligation — is the "why now" rather than page content.
Sources
hubandselfregistrationsVerification
npm run buildpasses; 165 pages indexed./spec/foundations/,/checklist/and in/llms.txt./spec/<category>/<slug>/cross-links confirmed against the target files' actual directories and against the builtdist/output.🤖 Generated with Claude Code