diff --git a/pack/pack.lock.json b/pack/pack.lock.json
index 52c05c2..865ac13 100644
--- a/pack/pack.lock.json
+++ b/pack/pack.lock.json
@@ -1,7 +1,7 @@
 {
   "$schema": "Brass-and-Sigil pack.lock.json - generated, do not edit by hand unless you know what you are doing",
   "name": "Brass and Sigil",
-  "version": "0.22.2",
+  "version": "0.22.3",
   "minecraft": "1.21.1",
   "loader": {
     "type": "neoforge",
diff --git a/scripts/Build-Pack.ps1 b/scripts/Build-Pack.ps1
index 50965cd..e21feee 100644
--- a/scripts/Build-Pack.ps1
+++ b/scripts/Build-Pack.ps1
@@ -107,14 +107,27 @@ if ($LocalPackSource -and (Test-Path $LocalPackSource)) {
         Get-ChildItem -Path $rootDir -Recurse -File | ForEach-Object {
             $rel = $_.FullName.Substring($sourceFull.Length).TrimStart('\','/') -replace '\\','/'
             $sha1 = (Get-FileHash -Algorithm SHA1 -Path $_.FullName).Hash.ToLowerInvariant()
-            $files += [pscustomobject]@{
+
+            # Tweak jars (built by Build-Tweaks.ps1 into pack/overrides/mods/)
+            # are pure data-only NeoForge mods -- worldgen modifiers, recipe
+            # overrides, etc. They typically depend on server-only libraries
+            # (Lithostitched, etc.) and have no client-side rendering. Default
+            # them to side="server" so the client doesn't try to load them
+            # without their server-only deps -> the loader otherwise refuses to
+            # start with "Mod X requires Y or above" errors. If a future tweak
+            # is genuinely client-relevant, override by editing this rule.
+            $entry = [ordered]@{
                 path = $rel
                 url  = "$base/$rel"
                 sha1 = $sha1
                 size = $_.Length
             }
+            if ($root -eq 'mods') { $entry.side = 'server' }
+
+            $files += [pscustomobject]$entry
             $totalBytes += $_.Length
-            Write-Host ("  [local]   {0}" -f $rel)
+            $sideTag = if ($entry.side) { "  [$($entry.side)]" } else { '' }
+            Write-Host ("  [local]   {0}{1}" -f $rel, $sideTag)
         }
     }
 }