`mermaid-format: svg` renders raw HTML instead of image in PDF and Typst output

[MSameerAbbas]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

mermaid-format: svg does not work for format: pdf or format: typst. Instead of using Chromium to render the mermaid diagram to an SVG image file, the diagram is rendered as inline HTML/SVG via deno-dom and the raw HTML — including <script> tags — is passed into the .tex / .typ file, causing compilation to fail.

mermaid-format: png works correctly — Chromium renders the diagram to a PNG image which is properly embedded.

Steps to reproduce

---
title: "Mermaid Test"
format:
  pdf:
    mermaid-format: svg
---

```{mermaid}
flowchart LR
    A[Start] --> B{Decision}
    B -->|Yes| C[Action 1]
    B -->|No| D[Action 2]
    C --> E[End]
    D --> E
```

quarto render mermaid_test.qmd --to pdf

Also fails with format: typst and mermaid-format: svg.

Note: Replacing mermaid-format: svg with mermaid-format: png renders successfully. rsvg-convert is installed and available on PATH (rsvg-convert version 2.40.20).

Actual behavior

LaTeX (format: pdf):

! LaTeX Error: Missing \begin{document}.

l.109 <
     script  src="mermaid_test_files/libs/quarto-diagram/mermaid-postprocess...

The .tex file contains raw HTML <script> tags and inline SVG elements instead of \includegraphics{} referencing a rendered SVG/PDF image.

Typst (format: typst):

error: unclosed label
    ┌─ mermaid_test.typ:281:0
    │
281 │ <script  src="mermaid_test_files/libs/quarto-diagram/mermaid-postprocess-shim.js"></script>
    │ ^^^^^^^

Debug output (--log-level DEBUG) with mermaid-format: svg shows:

1. [CHROMIUM] Found Chromium on OS known location / Path: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe — detected but never launched for SVG rendering.
2. Mermaid rendered via deno-dom-native (JS/HTML path) producing inline SVG.
3. Pandoc logs hundreds of [INFO] Not rendering RawInline (Format "html") — raw HTML passed to LaTeX/Typst writer.

In contrast, with mermaid-format: png:

Chromium is properly invoked, the diagram is rendered as a PNG image, and the trace shows [trace] Parsed [Para [Image ("",[],[("width","6.27in"),("height","1.81in"),... — a proper image element. PDF compiles successfully.

Expected behavior

With mermaid-format: svg, Quarto should:

1. Use Chromium to render the mermaid diagram to an SVG image file
2. Convert the SVG to PDF via rsvg-convert or inkscape (as documented)
3. Embed the image via \includegraphics{} (LaTeX) or image() (Typst)

Per the Quarto diagrams docs, valid values for mermaid-format include js, png, and svg.

Your environment

• IDE: Cursor
• OS: Windows 11
• Quarto installed via Chocolatey
• rsvg-convert version 2.40.20 available on PATH

Quarto check output

❯ quarto check
Quarto 1.8.27
[>] Checking environment information...
      Quarto cache location: C:\Users\msameer.abbas\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.3.1: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.8.27
      Path: C:\ProgramData\chocolatey\lib\quarto\tools\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: v2026.02
      Chromium: 869685

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\msameer.abbas\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2025

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe
      Source: Windows Registry

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....(None)

      Unable to locate an installed version of Python 3.
      Install Python 3 from https://www.python.org/downloads/

[>] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/