According to the blog post announcing snapshot 25w18a, there is supposed to be a new font (a copy of Unifont CSUR) at resource location minecraft:include/unifont_pua. However, that resource seems to be missing from the 25w18a client jar, and attempting to use it in a resource pack yields no changes.

Steps to reproduce

1. Create a resource pack with the following pack.mcmeta:
   

   {
       "pack": {
           "description": "Enables the Unifont CSUR font that comes with Minecraft since snapshot 25w18a but isn't enabled by default.",
           "pack_format": 59
       }
   }

2. Place the following file at assets/minecraft/font/uniform.json in the resource pack:
   

   {
       "providers": [
           {
               "type": "reference",
               "id": "minecraft:include/space"
           },
           {
               "type": "reference",
               "id": "minecraft:include/unifont"
           },
           {
               "type": "reference",
               "id": "minecraft:include/unifont_pua"
           }
       ]
   }

3. Enable the resource pack

4. Copy the following Tengwar sample text to your clipboard:
   

               ⸬                   ⸬

5. Open the chat input and paste

Expected result

The pasted tengwar are rendered in Unifont CSUR.

Actual result

The pasted text is displayed as tofu (rectangle shapes indicating missing characters).