mermaid diagram not displaying the text in preview

[shettydev]

I simply opened the markdown preview with a mermaid diagram, and it doesn't seem to render it correctly (not in the correct diagram format) nor is it even displaying any text

Reproduction steps

1. Open a markdown file, with a mermaid diagram
2. Press ctrl + shift + v or the "Preview Markdown" button
3. Checkout the mermaid diagram flow in the preview

Current vs. Expected behavior

Current behavior:

---

Expected behavior:

Zed version and system specs

Zed: v0.225.9+stable.181.cbc2b428b9003b31077f91f06f8912880b1dbcf4 (Zed)
OS: Linux X11 ubuntu 24.04
Memory: 47 GiB
Architecture: x86_64
GPU: NVIDIA GeForce RTX 3060 || NVIDIA || 535.288.01

Attach Zed log file

Zed.log

Relevant Zed settings

settings.json

Relevant Keymap

keymap.json

(for AI issues) Model provider details

No response

If you are using WSL on Windows, what flavor of Linux are you using?

None

[OmChillure]

I faced this same problem

Root cause:

The mermaid-rs-renderer crate emits font-family as an XML attribute with double-quoted font names (e.g. "Inter", "ui-sans-serif", ...). The existing fix in the fix-font-family-xml-escaping branch applies escape_xml() which converts " to ". When usvg parses the SVG, it decodes " back to " and then tries to look up the entire string "Inter", "ui-sans-serif", ... as a single font name which doesn't exist. This is why the diagram structure renders but all text is invisible.

Confirmed via Zed logs:

WARN [usvg::text] No match for '"Inter", "ui-sans-serif", "system-ui", "-apple-system", "Segoe UI", sans-serif' font-family.

Correct fix I think would be

The font names need their surrounding quotes stripped before being embedded in the SVG attribute (e.g. "Inter" - Inter)
so usvg can resolve each font individually from the comma-separated list. The fix should be applied in mermaid-rs-renderer/src/render.rs at every call site where theme.font_family is interpolated into a element.

I can fix this my adding a PR on mermaid-rs-render or team will handle this ?

Thank you

[smitbarmase]

I think you should get this bug report to upstream: https://github.com/1jehuang/mermaid-rs-renderer

[OmChillure]

Sure, thanks

[shettydev]

@smitbarmase thank you 🙏 for reopening this issue.

The underlying font-family handling bug is in ‎mermaid-rs-renderer, but this issue is specifically about Zed’s Markdown preview behavior.

Even if the upstream fix lands later, Zed currently ships with a version of ‎mermaid-rs-renderer that makes all Mermaid text invisible, which breaks diagrams for Zed users