nav_insert not creating fillable tabs

nav_panels inserted progmatically using nav_insert() are not fillable.

'Page 1' has class tab-pane html-fill-item html-fill container bslib-gap-spacing, whilst the new 'Page 2' just has class tab-pane.

library(bslib)

ui <- page_navbar(
    id = 'nav',
    nav_panel('Page 1',
              card("Content 1")))

server <- function(input, output, session) {
    nav_insert(id = "nav",
               nav = nav_panel('Page 2',
                               card("Content 2")))
}

shinyApp(ui, server)

Session Info

version R version 4.3.2 (2023-10-31 ucrt)
os Windows 10 x64 (build 19045)
system x86_64, mingw32
ui RStudio
language (EN)
collate English_United Kingdom.utf8
ctype English_United Kingdom.utf8
tz Europe/London
date 2023-12-21
rstudio 2023.09.1+494 Desert Sunflower (desktop)
pandoc NA

─ Packages ───────────────────────────────────────────────────────────────────────
package * version date (UTC) lib source
bslib * 0.6.1 2023-11-28 [1] CRAN (R 4.3.2)
cachem 1.0.8 2023-05-01 [1] CRAN (R 4.3.1)
callr 3.7.3 2022-11-02 [1] CRAN (R 4.3.1)
cli 3.6.1 2023-03-23 [1] CRAN (R 4.2.3)
colorspace 2.1-0 2023-01-23 [1] CRAN (R 4.3.1)
crayon 1.5.2 2022-09-29 [1] CRAN (R 4.2.3)
devtools 2.4.5 2022-10-11 [1] CRAN (R 4.2.2)
digest 0.6.33 2023-07-07 [1] CRAN (R 4.3.1)
dplyr 1.1.3 2023-09-03 [1] CRAN (R 4.3.1)
ellipsis 0.3.2 2021-04-29 [1] CRAN (R 4.1.3)
fansi 1.0.5 2023-10-08 [1] CRAN (R 4.3.1)
fastmap 1.1.1 2023-02-24 [1] CRAN (R 4.3.1)
fs 1.6.3 2023-07-20 [1] CRAN (R 4.3.1)
generics 0.1.3 2022-07-05 [1] CRAN (R 4.1.3)
ggplot2 3.4.4 2023-10-12 [1] CRAN (R 4.3.1)
glue 1.6.2 2022-02-24 [1] CRAN (R 4.1.3)
gtable 0.3.4 2023-08-21 [1] CRAN (R 4.3.1)
htmltools 0.5.7 2023-11-03 [1] CRAN (R 4.3.2)
htmlwidgets 1.6.2 2023-03-17 [1] CRAN (R 4.3.1)
httpuv 1.6.11 2023-05-11 [1] CRAN (R 4.3.1)
jquerylib 0.1.4 2021-04-26 [1] CRAN (R 4.1.3)
jsonlite 1.8.7 2023-06-29 [1] CRAN (R 4.2.3)
later 1.3.0 2021-08-18 [1] CRAN (R 4.1.3)
lifecycle 1.0.3 2022-10-07 [1] CRAN (R 4.2.3)
magrittr 2.0.3 2022-03-30 [1] CRAN (R 4.1.3)
memoise 2.0.1 2021-11-26 [1] CRAN (R 4.2.3)
mime 0.12 2021-09-28 [1] CRAN (R 4.1.1)
miniUI 0.1.1.1 2018-05-18 [1] CRAN (R 4.1.3)
munsell 0.5.0 2018-06-12 [1] CRAN (R 4.1.3)
pillar 1.9.0 2023-03-22 [1] CRAN (R 4.2.3)
pkgbuild 1.4.2 2023-06-26 [1] CRAN (R 4.3.1)
pkgconfig 2.0.3 2019-09-22 [1] CRAN (R 4.1.3)
pkgload 1.3.3 2023-09-22 [1] CRAN (R 4.3.1)
prettyunits 1.2.0 2023-09-24 [1] CRAN (R 4.3.1)
processx 3.8.2 2023-06-30 [1] CRAN (R 4.3.1)
profvis 0.3.8 2023-05-02 [1] CRAN (R 4.3.1)
promises 1.2.1 2023-08-10 [1] CRAN (R 4.3.1)
ps 1.7.5 2023-04-18 [1] CRAN (R 4.3.1)
purrr 1.0.2 2023-08-10 [1] CRAN (R 4.3.1)
R6 2.5.1 2021-08-19 [1] CRAN (R 4.1.3)
Rcpp 1.0.11 2023-07-06 [1] CRAN (R 4.3.1)
remotes 2.4.2.1 2023-07-18 [1] CRAN (R 4.3.1)
rlang 1.1.1 2023-04-28 [1] CRAN (R 4.2.3)
rstudioapi 0.15.0 2023-07-07 [1] CRAN (R 4.2.3)
sass 0.4.7 2023-07-15 [1] CRAN (R 4.3.1)
scales 1.2.1 2022-08-20 [1] CRAN (R 4.2.3)
sessioninfo 1.2.2 2021-12-06 [1] CRAN (R 4.1.3)
shiny * 1.7.5.1 2023-10-14 [1] CRAN (R 4.3.1)
stringi 1.7.12 2023-01-11 [1] CRAN (R 4.3.0)
stringr 1.5.0 2022-12-02 [1] CRAN (R 4.2.3)
tibble 3.2.1 2023-03-20 [1] CRAN (R 4.2.3)
tidyselect 1.2.0 2022-10-10 [1] CRAN (R 4.2.3)
urlchecker 1.0.1 2021-11-30 [1] CRAN (R 4.1.3)
usethis 2.2.2 2023-07-06 [1] CRAN (R 4.3.1)
utf8 1.2.3 2023-01-31 [1] CRAN (R 4.3.1)
vctrs 0.6.3 2023-06-14 [1] CRAN (R 4.2.3)
withr 2.5.1 2023-09-26 [1] CRAN (R 4.3.1)
xtable 1.8-4 2019-04-21 [1] CRAN (R 4.1.3)

Start with the nav_insert() and nav_panel() entry points shown in the issue, then inspect how the inserted Page 2 markup differs from the initial Page 1 markup. Confirm that dynamically inserted panels receive the same fillable classes as the initial panel and verify the reproduced example afterward.