diff --git a/.gitignore b/.gitignore
index 9722c8c..e30d1d4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 # C2ME runtime worldgen class cache (regenerated at runtime; see .packwizignore)
 cache/
+
+# Immersive Paintings player-upload cache (regenerated at runtime; see .packwizignore)
+immersive_paintings_cache/
diff --git a/.packwizignore b/.packwizignore
index 1a8374c..83d50ea 100644
--- a/.packwizignore
+++ b/.packwizignore
@@ -40,6 +40,9 @@ tools/
 # C2ME runtime worldgen cache (regenerated at runtime)
 cache/
 
+# Immersive Paintings player-upload cache (regenerated at runtime)
+immersive_paintings_cache/
+
 # Scratch artifacts from the map-migration tooling - never ship these
 sp-world/
 xaero-migration-kit/
diff --git a/index.toml b/index.toml
index 897a583..fcc1258 100644
--- a/index.toml
+++ b/index.toml
@@ -1087,3 +1087,8 @@ metafile = true
 file = "shaderpacks/makeup-ultra-fast-shaders.pw.toml"
 hash = "b65333a4878eecf3d220c101ae02be6e8707380156a7a02100164a865fb3a167"
 metafile = true
+
+[[files]]
+file = "usernamecache.pw.toml"
+hash = "8b15bf90bf87fd17378d8413ff0e2d3f4d0d2ffc5d6b0fa87e654ec99621b2fc"
+metafile = true
diff --git a/pack.toml b/pack.toml
index b881738..6d81c57 100644
--- a/pack.toml
+++ b/pack.toml
@@ -6,7 +6,7 @@ pack-format = "packwiz:1.1.0"
 [index]
 file = "index.toml"
 hash-format = "sha256"
-hash = "f9852076c38404288e9f09588cdae45b6e3a51fb8333099953566abbe06c791a"
+hash = "65215ee765ac7e8321c232dd2624f7453aed4900384a18b004410d77158f7b6d"
 
 [versions]
 minecraft = "1.21.1"
diff --git a/packfiles/usernamecache-offline.json b/packfiles/usernamecache-offline.json
new file mode 100644
index 0000000..02e9c9d
--- /dev/null
+++ b/packfiles/usernamecache-offline.json
@@ -0,0 +1,7 @@
+{
+  "032f0cc0-2762-33bc-9731-e6cf550f6527": "Onion4Dinner",
+  "0d000554-ad3a-3719-83db-3a7fd258cd88": "ItsMeC",
+  "673b1e52-3895-3d9d-ae01-daca53835e89": "xX_ShyG0D_Xx",
+  "a03ea28c-ab84-339d-ac8b-dee0a152be15": "Conqueeftador",
+  "c22c84e2-a8d1-3acb-bb56-32047ed1aa83": "Stirwick"
+}
diff --git a/tools/sync-usernamecache.py b/tools/sync-usernamecache.py
new file mode 100644
index 0000000..7d803e0
--- /dev/null
+++ b/tools/sync-usernamecache.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+"""Refresh the pack's client-side usernamecache.json from the live server cache.
+
+The pack ships <game>/usernamecache.json to clients (via usernamecache.pw.toml)
+so Jade can resolve offline-mode owner names client-side (it falls back to
+NeoForge's UsernameCache after the Mojang lookup fails). This merges the
+server's live cache into packfiles/usernamecache-offline.json and updates the
+download hash in usernamecache.pw.toml.
+
+Run after new players have logged in, then refresh/commit/push:
+
+    python3 tools/sync-usernamecache.py
+    packwiz refresh
+    git add packfiles/usernamecache-offline.json usernamecache.pw.toml index.toml pack.toml
+    git commit -m "chore(pack): refresh client usernamecache"
+    git push
+"""
+import hashlib
+import json
+import pathlib
+import re
+import sys
+
+ROOT = pathlib.Path(__file__).resolve().parent.parent
+LIVE = ROOT / "usernamecache.json"
+SHIPPED = ROOT / "packfiles" / "usernamecache-offline.json"
+META = ROOT / "usernamecache.pw.toml"
+
+
+def load(path):
+    try:
+        return json.loads(path.read_text(encoding="utf-8"))
+    except FileNotFoundError:
+        return {}
+
+
+def main():
+    live = load(LIVE)
+    shipped = load(SHIPPED)
+    merged = {**shipped, **live}  # the live server cache wins
+    if not merged:
+        print("no entries found; is the server's usernamecache.json missing?", file=sys.stderr)
+        return 1
+
+    text = json.dumps(merged, indent=2, sort_keys=True) + "\n"
+    changed = not SHIPPED.exists() or SHIPPED.read_text(encoding="utf-8") != text
+    SHIPPED.parent.mkdir(parents=True, exist_ok=True)
+    SHIPPED.write_text(text, encoding="utf-8")
+
+    digest = hashlib.sha256(text.encode("utf-8")).hexdigest()
+    meta = META.read_text(encoding="utf-8")
+    new_meta = re.sub(r'(?m)^(hash = ")[0-9a-f]+(")$', lambda m: m.group(1) + digest + m.group(2), meta)
+    if new_meta != meta:
+        META.write_text(new_meta, encoding="utf-8")
+
+    print(f"{len(merged)} entries ({len(live)} live, {len(shipped)} shipped), "
+          f"{'updated' if changed else 'unchanged'} -> packfiles/usernamecache-offline.json")
+    print(f"sha256 {digest}")
+    print("next: packwiz refresh && git add packfiles/usernamecache-offline.json "
+          "usernamecache.pw.toml index.toml pack.toml && commit && push")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/usernamecache.pw.toml b/usernamecache.pw.toml
new file mode 100644
index 0000000..7f03973
--- /dev/null
+++ b/usernamecache.pw.toml
@@ -0,0 +1,8 @@
+name = "usernamecache (offline owner names for Jade)"
+filename = "usernamecache.json"
+side = "client"
+
+[download]
+url = "https://git.ljones.me/logan/onion-mc/raw/branch/main/packfiles/usernamecache-offline.json"
+hash-format = "sha256"
+hash = "da4e9e31233718bcf421127b5d89517dcb0db7287e21653532edfffcb9b75de2"