diff --git a/HellionChat/HellionChat.csproj b/HellionChat/HellionChat.csproj
index d56f76c..9ba2e94 100644
--- a/HellionChat/HellionChat.csproj
+++ b/HellionChat/HellionChat.csproj
@@ -18,7 +18,11 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="MessagePack" Version="3.1.4" />
+        <!-- Closed ranges on packages with breaking-change history block a
+             surprise major bump when the lock file is regenerated. The
+             lock file pins the exact version per build; the upper bound
+             keeps the unlock path from drifting across major lines. -->
+        <PackageReference Include="MessagePack" Version="[3.1.4, 4.0.0)" />
         <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.7" />
         <!-- Override the transitively-referenced native SQLite build to one
              that ships SQLite >= 3.50.3 (CVE-2025-6965 memory corruption,
@@ -28,8 +32,8 @@
              without a major bump on the managed wrapper. -->
         <PackageReference Include="SQLitePCLRaw.lib.e_sqlite3" Version="3.50.3" />
         <PackageReference Include="morelinq" Version="4.4.0" />
-        <PackageReference Include="Pidgin" Version="3.5.1" />
-        <PackageReference Include="SixLabors.ImageSharp" Version="3.1.12" />
+        <PackageReference Include="Pidgin" Version="[3.5.1, 4.0.0)" />
+        <PackageReference Include="SixLabors.ImageSharp" Version="[3.1.12, 4.0.0)" />
     </ItemGroup>
 
     <ItemGroup>
diff --git a/HellionChat/packages.lock.json b/HellionChat/packages.lock.json
index 8f6f61c..d3d3517 100644
--- a/HellionChat/packages.lock.json
+++ b/HellionChat/packages.lock.json
@@ -16,7 +16,7 @@
       },
       "MessagePack": {
         "type": "Direct",
-        "requested": "[3.1.4, )",
+        "requested": "[3.1.4, 4.0.0)",
         "resolved": "3.1.4",
         "contentHash": "BH0wlHWmVoZpbAPyyt2Awbq30C+ZsS3eHSkYdnyUAbqVJ22fAJDzn2xTieBeoT5QlcBzp61vHcv878YJGfi3mg==",
         "dependencies": {
@@ -44,13 +44,13 @@
       },
       "Pidgin": {
         "type": "Direct",
-        "requested": "[3.5.1, )",
+        "requested": "[3.5.1, 4.0.0)",
         "resolved": "3.5.1",
         "contentHash": "zU7tkXlF3D6d2GLTjJDomAL3nnl4AwfZvSgSz8D4b+Ry21/clqedYlxBnEAkAU/bkGfEv6uRR7QCdWZUpKrB/g=="
       },
       "SixLabors.ImageSharp": {
         "type": "Direct",
-        "requested": "[3.1.12, )",
+        "requested": "[3.1.12, 4.0.0)",
         "resolved": "3.1.12",
         "contentHash": "iAg6zifihXEFS/t7fiHhZBGAdCp3FavsF4i2ZIDp0JfeYeDVzvmlbY1CNhhIKimaIzrzSi5M/NBFcWvZT2rB/A=="
       },