How to supply a custom gradient background to `sidebar()`?

Hi friends! First of all I'm obsessed with this package we don't deserve you all but of course I'm gonna ask to do weird outlier things LOL - not sure if this is a bug or by design.....

overriding a boostrap variable with a hex code works just fine:

page_sidebar(
   sidebar = "",
   theme = bs_add_variables(
      bs_theme(),
      "bslib-sidebar-bg" = "#e66465"
   )
)

But if I want to use a linear gradient I get a sass error?

page_sidebar(
   sidebar = "",
   theme = bs_add_variables(
      bs_theme(),
      "bslib-sidebar-bg" = "linear-gradient(#e66465, #9198e5)"
   )
)

Error in compile_data(sass_input, options) : 
  Error: argument `$color` of `red($color)` must be a color
        on line 60:10 of ../../../home/maya.gans/R/x86_64-pc-linux-gnu-library/4.3/bslib/sass-utils/color-contrast.scss, in function `red`
        from line 60:10 of ../../../home/maya.gans/R/x86_64-pc-linux-gnu-library/4.3/bslib/sass-utils/color-contrast.scss, in function `luminance`
        from line 49:8 of ../../../home/maya.gans/R/x86_64-pc-linux-gnu-library/4.3/bslib/sass-utils/color-contrast.scss, in function `contrast-ratio`
        from line 31:22 of ../../../home/maya.gans/R/x86_64-pc-linux-gnu-library/4.3/bslib/sass-utils/color-contrast.scss, in function `color-contrast`
        from line 12:20 of ../../../home/maya.gans/R/x86_64-pc-linux-gnu-library/4.3/bslib/components/_variables.scss
        from line 15:9 of stdin
>>     "r": red($color),

   ---------^

I know that linear-gradient can only be used on the background property, maybe $bslib-sidebar-bg is used for a different property?

I also tried the code below which looks like is just another way of assigning bslib-background-bg but now the sidebar is just white and I don't get any error?

page_sidebar(
   sidebar = sidebar(
      bg = "linear-gradient(#e66465, #9198e5)", 
      fg = 'white'
   )
)

Any tips?

Start with the supplied page_sidebar() reproductions and trace the Sass error through sass-utils/color-contrast.scss and components/_variables.scss. Check how bslib-sidebar-bg and sidebar(bg=...) are consumed, then verify that a linear-gradient value compiles and renders as the sidebar background without breaking color-contrast handling.