I have:
Bug description
The HTML code docs state that the highlighting variant is chosen from the code block background:
When available, Quarto will automatically select the appropriate style based upon the code chunk background color's darkness.
When I explicitly set a dark code background with brand, I still get the light highlighting variant.
It's possible that rather than a bug, the docs need clarifying. I.e. the situation that does work (I think), is when a light and dark theme/brand are invoked, the light/dark syntax highlighting variants are automatically switched.
Steps to reproduce
---
title: "Dark code background via brand"
format:
html:
syntax-highlighting: arrow
brand:
typography:
monospace-block:
background-color: "#252323"
---
```r
x <- mean(c(1, 2, 3))
```Actual behavior
The code block renders with the dark background (#252323) but the light arrow highlighting variant, so syntax tokens use dark-on-light colors (e.g. #003B4F, #AD0000) that are barely legible on the dark block.
Expected behavior
Per the docs, a dark code-block background should select the dark highlighting variant (arrow-dark), so syntax tokens are light-on-dark and legible — independent of the page/body background color.
Your environment
- IDE: command line / terminal (also reproduces with Positron's bundled Quarto)
- OS: macOS 26.5.1 (Apple Silicon)
Quarto check output
Quarto 1.9.38
[✓] Checking environment information...
Quarto cache location: /Users/charlottewickham/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
Pandoc version 3.8.3: OK
Dart Sass version 1.87.0: OK
Deno version 2.4.5: OK
Typst version 0.14.2: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
Version: 1.9.38
Path: /Applications/Positron.app/Contents/Resources/app/quarto/bin
[✓] Checking tools....................OK
TinyTeX: v2026.04
VeraPDF: 1.28.2
Chromium: (not installed)
Chrome Headless Shell: (not installed)
[✓] Checking LaTeX....................OK
Using: TinyTex
Path: /Users/charlottewickham/Library/TinyTeX/bin/universal-darwin
Version: 2026
[✓] Checking Chrome Headless....................OK
Using: Chrome found on system
Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome
Source: MacOS known location
[✓] Checking basic markdown render....OK
[✓] Checking R installation...........OK
Version: 4.5.1
Path: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources
knitr: 1.51
rmarkdown: 2.30
[✓] Checking Knitr engine render......OK
[✓] Checking Python 3 installation....OK
Version: 3.12.2
Path: /Users/charlottewickham/.pyenv/versions/3.12.2/bin/python3
Jupyter: 5.9.1
Kernels: python3
[✓] Checking Jupyter engine render....OK
[✓] Checking Julia installation...OK
I have:
Bug description
The HTML code docs state that the highlighting variant is chosen from the code block background:
When I explicitly set a dark code background with
brand, I still get the light highlighting variant.It's possible that rather than a bug, the docs need clarifying. I.e. the situation that does work (I think), is when a
lightanddarktheme/brand are invoked, the light/dark syntax highlighting variants are automatically switched.Steps to reproduce
Actual behavior
The code block renders with the dark background (
#252323) but the lightarrowhighlighting variant, so syntax tokens use dark-on-light colors (e.g.#003B4F,#AD0000) that are barely legible on the dark block.Expected behavior
Per the docs, a dark code-block background should select the dark highlighting variant (
arrow-dark), so syntax tokens are light-on-dark and legible — independent of the page/body background color.Your environment
Quarto check output
Quarto 1.9.38 [✓] Checking environment information... Quarto cache location: /Users/charlottewickham/Library/Caches/quarto [✓] Checking versions of quarto binary dependencies... Pandoc version 3.8.3: OK Dart Sass version 1.87.0: OK Deno version 2.4.5: OK Typst version 0.14.2: OK [✓] Checking versions of quarto dependencies......OK [✓] Checking Quarto installation......OK Version: 1.9.38 Path: /Applications/Positron.app/Contents/Resources/app/quarto/bin [✓] Checking tools....................OK TinyTeX: v2026.04 VeraPDF: 1.28.2 Chromium: (not installed) Chrome Headless Shell: (not installed) [✓] Checking LaTeX....................OK Using: TinyTex Path: /Users/charlottewickham/Library/TinyTeX/bin/universal-darwin Version: 2026 [✓] Checking Chrome Headless....................OK Using: Chrome found on system Path: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome Source: MacOS known location [✓] Checking basic markdown render....OK [✓] Checking R installation...........OK Version: 4.5.1 Path: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources knitr: 1.51 rmarkdown: 2.30 [✓] Checking Knitr engine render......OK [✓] Checking Python 3 installation....OK Version: 3.12.2 Path: /Users/charlottewickham/.pyenv/versions/3.12.2/bin/python3 Jupyter: 5.9.1 Kernels: python3 [✓] Checking Jupyter engine render....OK [✓] Checking Julia installation...OK