Thanks.
I notice that I am using Quarto Version 1.9.38 on Ubuntu 26.04 and I am running a newer version of R but I rather doubt this is the problem or we should be seeing more postings about your problem.
!! Breaking news!!
Quarto 1.10 has just been released
This is my set-up.
> sessionInfo()
R version 4.6.1 (2026-06-24)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 26.04 LTS
RStudio Desktop Pro, 2026.06.0 Build 242.pro13
The RStudio Desktop Pro is a mistake. I thought I was updating to the standard desktop version.
Using my set-up I can produce your Mermaid chart in
- html
- docx
- odt
For a moment, I was having a problem running your chart plus another {mermaid} chart but a simple restart of R solved that problem.
So, at the moment, I have no idea what is happening. You might want to update R and Quarto just "because". A quick internet search is not turning up much but a possible work-around seems to be Mermaid not rendering in Quarto document in RStudio IDE visual editor - #3 by cderv.
Just for general interest here is my sessionInfo().
R version 4.6.1 (2026-06-24)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 26.04 LTS
Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3
LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.32.so; LAPACK version 3.12.0
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
time zone: America/Toronto
tzcode source: system (glibc)
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_4.6.1 lobstr_1.2.1 cli_3.6.6 tools_4.6.1 rstudioapi_0.19.0 pacman_0.5.1
[7] rlang_1.3.0 pak_0.11.1