WPF (.NET 8) XAML cannot resolve namespaces, converters, ViewModels despite classes being public

I'm losing my mind over this project and honestly have no idea what else to try.

I'm working on a WPF app targeting .NET 8 and I'm getting a massive number of XAML errors like:

XDG0008: The name "XYZ" does not exist in the namespace

XDG0001: The resource "XYZ" could not be resolved

MC3037: Missing XmlNamespace, Assembly or ClrNamespace

XDG0006: Cannot find type in clr-namespace

plus random type incompatibility errors:

[Error (active) MC3037 Missing XmlNamespace, Assembly or ClrNamespace in Mapping instruction. Line 442 Position 61. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 442

Error XDG-0001 The resource "RoleMargin" could not be resolved. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 337

Error XDG-0001 The resource "InvBoolVis" could not be resolved. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 439

Error XDG-0001 The resource "InvBoolVis" could not be resolved. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 519

Error XDG-0001 The resource "CountVis" could not be resolved. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 259

Error XDG-0001 The resource "CountVis" could not be resolved. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 333

Error XDG-0001 The resource "BoolVis" has an incompatible type. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 47

Error XDG-0001 The resource "BoolVis" has an incompatible type. AMV.App C:\Users\barto\source\AMV_project\AMV\AMV.App\Views\MainWindow.xaml 204

Examples

The name "ZeroToVisibilityConverter" does not exist in the namespace "clr-namespace:AMV.Converters"
The name "MainViewModel" does not exist in the namespace "clr-namespace:AMV.ViewModels"
The name "Conversation" does not exist in the namespace "clr-namespace:AMV.Models"
The resource "BoolVis" has an incompatible type The resource "RoleMargin" could not be resolved

Also:

CS1631 Cannot yield a value in the body of a catch clause

Important details

ALL classes (converters, view models, models, etc.) are declared as public

Namespaces in code match the folder structure

I tried both:

xmlns:conv="clr-namespace:AMV.Converters"

and

xmlns:conv="clr-namespace:AMV.Converters;assembly=AMV"

Project builds partially, but XAML designer and runtime both complain

Resources are defined (or at least should be) in ResourceDictionaries

I also use merged dictionaries (MessageTemplates.xaml etc.)

What I already tried:

Cleaning solution (dotnet clean) Rebuilding everything Deleting bin and obj Restarting Visual Studio Checking namespace typos 10+ times Making sure classes are public Moving classes between projects Adding/removing assembly= in XAML namespaces Verifying Build Action (Page, Resource, etc.) Checking if files are included in .csproj Recreating some converters from scratch Swearing at it (did not help)

Suspicion

At this point I suspect one of these:

.NET 8 + WPF weirdness Broken project references Assembly name mismatch (AMV vs AMV.App?) XAML not seeing compiled code-behind ResourceDictionary not loading correctly Something fundamentally broken in project structure

Full project can be found here: https://github.com/skye7x/AMV-Ai

Question

What could cause XAML to not see ANY types from my own namespaces, even though:

classes exist are public namespaces are correct project builds (partially)

Is there something obvious I'm missing, or is this some deeper WPF/.NET issue?

At this point I genuinely don't know what to do with this project anymore.