Premake configuration - include directories in a multi project work directory

Question

I have a work directory which holds a client project called 'Client', a library project called 'MainLib', under which there is a 'vendor' directory under which there is another project called 'SecondaryLib'.

For 'Client' premake5.lua I have this configuration:

project "Client"
kind "ConsoleApp"
language "C++"
cppdialect "C++20"
staticruntime "off"

targetdir ("%{wks.location}/bin/" .. outputdir .. "/%{prj.name}")
objdir ("%{wks.location}/obj/" .. outputdir .. "/%{prj.name}")

files
{
    "src/**.h",
    "src/**.cpp"
}

includedirs
{
    "%{wks.location}/MainLib/src",
    "%{wks.location}/MainLib/vendor",
}

links
{
    "MainLib"
}

filter "system:windows"
    systemversion "latest"

filter "configurations:Debug"
    defines "KN_DEBUG"
    runtime "Debug"
    symbols "on"

filter "configurations:Release"
    defines "KN_RELEASE"
    runtime "Release"
    optimize "on"

filter "configurations:Dist"
    defines "KN_DIST"
    runtime "Release"
    optimize "on"

For the MainLib premake5.lua:

project "MainLib"
kind "StaticLib"
language "C++"
cppdialect "C++20"
staticruntime "off"

targetdir ("%{wks.location}/bin/" .. outputdir .. "/%{prj.name}")
objdir ("%{wks.location}/obj/" .. outputdir .. "/%{prj.name}")

files
{
    "src/**.h",
    "src/**.cpp"
}

defines
{
    "_CRT_SECURE_NO_WARNINGS"
}

includedirs
{
    "src",
    "vendor/SecondaryLib/src/include",
}

links
{
    "SecondaryLib"
}

filter "system:windows"
    systemversion "latest"

    defines
    {
     "KN_PLATFORM_WINDOWS",
    }

filter "configurations:Debug"
    defines "KN_DEBUG"
    runtime "Debug"
    symbols "on"

filter "configurations:Release"
    defines "KN_RELEASE"
    runtime "Release"
    optimize "on"

filter "configurations:Dist"
    defines "KN_DIST"
    runtime "Release"
    optimize "on"

And for the SecondaryLib:

project "SecondaryLib"
kind "StaticLib"
language "C"

targetdir ("bin/" .. outputdir .. "/%{prj.name}")
objdir ("obj/" .. outputdir .. "/%{prj.name}")

files
{
    "include/inc.h",
    "src/test.h"
}

filter "system:windows"
    systemversion "latest"
    staticruntime "On"

    files
    {
        "src/test.h"    
    }

    defines 
    { 
        "_GLFW_WIN32",
        "_CRT_SECURE_NO_WARNINGS"
    }

filter "configurations:Debug"
    runtime "Debug"
    symbols "on"

filter "configurations:Release"
    runtime "Release"
    optimize "on"

I can compile the 'MainLib' separately just fine, but when I try to compile the 'Client', it will output an error: *C1083 Cannot open include file: 'inc.h': No such file or directory Client E:\VS Projects\Solution\MainLib\src\MainLib.h *

inc.h being a file in the '/MainLib/vendor/SecondaryLib/src/include'-folder.

Now I could solve this by adding the same includedirs to 'Client' as 'MainLib', but I think that should not be required for a client application. I literally have another premake project with what seems to be identical settings, and it works exactly as I want.

What am I missing?

The settings were copied from a premake5 workspace where this was working.