GT, interactive or not, tables not displaying correctly header (if present) if used with tabset

Prework

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Description

Adding gt tables with interactive options in quarto and tabsets results in errors in the header sections.
The <div class> is not parsed correctly.

Reproducible example

---
title: "Gt interactive or not tables not correctly displaying if header in tabset"
format: html
engine: knitr
---

```{r}
#| label: libs-import
library(gt)
library(tidyverse)
library(quartabs)
```

```{r}
#| include: false
#| label: blank-allows-gt-to-work
gt::gt(mtcars) |>
  gt::opt_interactive()
```


```{r}
#| results: asis
#| label: display-tabs-nointeractive
mtcars |>
    nest_by(cyl) |>
    rowwise() |>
    mutate(
        cyl_gt = list(
            gt(data) |>
                tab_header(
                    title = "Title",
                    subtitle = "Subtitle"
                )
        )
    ) |>
    quartabs::render_tabset(cyl, cyl_gt)
```

```{r}
#| results: asis
#| label: display-tabs-interactive
mtcars |>
    nest_by(cyl) |>
    rowwise() |>
    mutate(
        cyl_gt = list(
            gt(data) |>
                opt_interactive() |>
                tab_header(
                    title = "Title",
                    subtitle = "Subtitle"
                )
        )
    ) |>
    quartabs::render_tabset(cyl, cyl_gt)
```

I'm using package quartabs for this. It's a wrapper for including figs and tables in tabset in quarto.
I've tried the classic hacks from here or here.

If there is no header defined by tab_header(), it's working.

With GT interactive tables, if I had a header with the function, I get at the beginning of each tab:

<div class="gt_heading gt_title gt_font_normal" style="text-size:bigger;">Title</div>
<div class="gt_heading gt_subtitle ">Subtitle</div>

instead of the header correctly displayed with the correct style.

In addition, if the GT tables are not interactive, the header is displayed but without the formatting (tab_style for example)

```{r}
#| include: false
#| label: blank-allows-gt-to-work
gt::gt(mtcars) |>
  gt::opt_interactive()
```

is recommended by the vignette of quartabs here to resolve javascript dependencies.

Looking at the HTML output, it seems I can see why I get with behaviour

<pre><code>&lt;div class="gt_heading gt_title gt_font_normal" style="text-size:bigger;"&gt;Title&lt;/div&gt;
&lt;div class="gt_heading gt_subtitle "&gt;Subtitle&lt;/div&gt;</code></pre>

The formatting of the HTML seems wrong.

Expected result

Each tab should have a GT table with correct header if filled.

• Not interactive: header with the style (color, alignment, ...)
• Interactive: the header in HTML should be correct

Working code without loop:

:::{.panel-tabset}

## 4

```{r}
#| results: asis
#| label: panel-4
gt(mtcars |>
    filter(cyl == 4)) |>
    opt_interactive()  |>
    tab_header(
        title = "Title",
        subtitle = "Subtitle"
        )
```

## 6

```{r}
#| results: asis
#| label: panel-6
gt(mtcars |>
    filter(cyl == 6)) |>
    opt_interactive() |>
    tab_header(
        title = "Title",
        subtitle = "Subtitle"
        )
```

## 8

```{r}
#| results: asis
#| label: panel-8
gt(mtcars |>
    filter(cyl == 8)) |>
    opt_interactive() |>
    tab_header(
        title = "Title",
        subtitle = "Subtitle"
        )

```

:::

Session info

R version 4.5.3 (2026-03-11)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 24.04.4 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-r0.3.26.so;  LAPACK version 3.12.0

locale:
 [1] LC_CTYPE=fr_FR.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=fr_FR.UTF-8        LC_COLLATE=fr_FR.UTF-8    
 [5] LC_MONETARY=fr_FR.UTF-8    LC_MESSAGES=fr_FR.UTF-8   
 [7] LC_PAPER=fr_FR.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=fr_FR.UTF-8 LC_IDENTIFICATION=C       

time zone: Europe/Paris
tzcode source: system (glibc)

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     

other attached packages:
 [1] quartabs_0.1.1  lubridate_1.9.5 forcats_1.0.1   stringr_1.6.0  
 [5] dplyr_1.2.1     purrr_1.2.2     readr_2.2.0     tidyr_1.3.2    
 [9] tibble_3.3.1    ggplot2_4.0.2   tidyverse_2.0.0 gt_1.3.0       

loaded via a namespace (and not attached):
 [1] sass_0.4.10        generics_0.1.4     bspm_0.5.7         xml2_1.5.2        
 [5] stringi_1.8.7      hms_1.1.4          digest_0.6.39      magrittr_2.0.5    
 [9] evaluate_1.0.5     grid_4.5.3         timechange_0.4.0   RColorBrewer_1.1-3
[13] fastmap_1.2.0      jsonlite_2.0.0     crosstalk_1.2.2    scales_1.4.0      
[17] cli_3.6.6          rlang_1.2.0        reactR_0.6.1       withr_3.0.2       
[21] yaml_2.3.12        otel_0.2.0         tools_4.5.3        tzdb_0.5.0        
[25] vctrs_0.7.3        R6_2.6.1           lifecycle_1.0.5    reactable_0.4.5   
[29] fs_2.0.1           htmlwidgets_1.6.4  pkgconfig_2.0.3    pillar_1.11.1     
[33] gtable_0.3.6       glue_1.8.0         xfun_0.57          tidyselect_1.2.1  
[37] knitr_1.51         dichromat_2.0-0.1  farver_2.1.2       htmltools_0.5.9   
[41] rmarkdown_2.31     compiler_4.5.3     S7_0.2.1