heddle check --only diagrams
diagrams Check
Diagrams. require, on by default), every ```mermaid block captioned, rendered in the current brand theme and safe to inline; no SVG pasted into a new post in place of one; and, on the built pages, every diagram shipped as a captioned figure with an accessible name, never as a code block, with its labels inside their boxes. Origins (the source site): - 8 October 2026. Agent-drafted posts carried mermaid-cli's default theme as <img>, in a fallback font.
When Heddle is set up on your site, this check runs on every build alongside 25 others, so a page that fails it is fixed before a buyer or a search engine sees it.
Why it exists
Diagrams. Every post carries a diagram or an image in its body (site.json diagrams.require, on by default), every ```mermaid block captioned, rendered in the current brand theme and safe to inline; no SVG pasted into a new post in place of one; and, on the built pages, every diagram shipped as a captioned figure with an accessible name, never as a code block, with its labels inside their boxes.
Origins (the source site):
- 8 October 2026. Agent-drafted posts carried mermaid-cli's default theme as
<img>, in a fallback font. Since then a diagram is a mermaid block with a%% caption:line, rendered in the site's theme, and a new post that embeds an SVG fails (scripts/render-diagrams.mjs --check). - 3 October 2026.
Every diagram on the Field Guide had clipped labels in production, because text-wrap. Pretty on <p> reached into mermaid's HTML labels. The markup was identical in the broken and working states; only a browser could see it. So the built pages are opened in Chromium and every label's box is measured against its shape.
The browser half needs Chromium. Without one it says so as a warning. An unmeasured page is reported as unmeasured, never as passed.
From lib/checks/diagrams.mjs in the Heddle repository at ddb1b16.
Questions
What does the diagrams check look for?
Mermaid diagrams captioned, rendered in the brand theme and safe; no pasted SVG in new posts; built figures captioned, named, and their labels not clipped.
Does the diagrams check need an AI model?
No. It reads the built pages or the sources directly, so it runs offline and costs nothing per run.
How do I run it?
Build the site, then run node bin/heddle.mjs check <site> --only diagrams from the Heddle repository.
Work with us
Let the agents bring you the leads.
Tell us about your business and who buys from you. On a short call we'll show you the searches your buyers make where you don't show up yet, and what the agents would do about them in their first month.
On the call, for your site
- The searches your buyers makeMeasured, with how many people make each one
- Where you show up, and where you don'tOn Google and in ChatGPT's answers
- The agents' first monthThe pages, fixes and links they would start with