2026-05-22 15:15:03 +00:00
7 changed files with 538 additions and 353 deletions
@@ -95,6 +95,15 @@ public sealed class ManifestFile

    [JsonPropertyName("size")]
    public long? Size { get; set; }
+
+    /// <summary>
+    /// "both" (default), "client", or "server". The launcher skips files
+    /// marked "server"; the server-tool skips files marked "client".
+    /// Null/missing/unknown = treated as "both" so manifests pre-dating
+    /// this field stay fully compatible.
+    /// </summary>
+    [JsonPropertyName("side")]
+    public string? Side { get; set; }
 }

 public sealed class PackVersionRecord
@@ -66,6 +66,7 @@ public sealed class ManifestSyncService
        var missing = new System.Collections.Generic.List<ManifestFile>();
        foreach (var file in manifest.Files)
        {
+            if (IsServerOnly(file)) continue;   // never expected on disk client-side
            var dest = Path.Combine(installDir, file.Path);
            if (!File.Exists(dest)) missing.Add(file);
        }
@@ -113,6 +114,19 @@ public sealed class ManifestSyncService
            $"Pack: {manifest.Name ?? "modpack"} v{manifest.Version ?? "?"} (local: {local?.Version ?? "none"})"
        ));

+        // Drop server-only files before computing wanted/download sets. Doing
+        // it once here means the rest of the sync (prune + download) doesn't
+        // need to know about sides. Unknown/missing/'both' = include on client.
+        var serverOnlyCount = manifest.Files.Count(f => IsServerOnly(f));
+        if (serverOnlyCount > 0)
+        {
+            manifest.Files = manifest.Files.Where(f => !IsServerOnly(f)).ToList();
+            progress.Report(new ProgressReport(
+                ProgressKind.Log,
+                $"Skipping {serverOnlyCount} server-only file(s) declared in manifest."
+            ));
+        }
+
        var wantedPaths = new HashSet<string>(
            manifest.Files.Select(f => NormalizePath(f.Path)),
            StringComparer.OrdinalIgnoreCase
@@ -249,4 +263,12 @@ public sealed class ManifestSyncService
    }

    private static string NormalizePath(string p) => p.Replace('\\', '/').TrimStart('/');
+
+    /// <summary>
+    /// True if this manifest file is tagged as server-only and therefore
+    /// should not be installed on the client. Unknown/null/'both' = false
+    /// (always include) so manifests pre-dating the field still install.
+    /// </summary>
+    private static bool IsServerOnly(ManifestFile f)
+        => string.Equals(f.Side, "server", StringComparison.OrdinalIgnoreCase);
 }
@@ -1,13 +1,13 @@
 {
  "$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":  "0.9.3",
+  "version": "0.10.0",
  "minecraft": "1.21.1",
  "loader": {
    "type": "neoforge",
    "version": "21.1.228"
  },
-    "lockedAt":  "2026-05-04T14:22:58.7131203+01:00",
+  "lockedAt": "2026-05-04T13:22:58.7131203+00:00",
  "mods": [
    {
      "source": "modrinth",
@@ -17,7 +17,8 @@
      "path": "mods/create-1.21.1-6.0.10.jar",
      "url": "https://cdn.modrinth.com/data/LNytGWDc/versions/UjX6dr61/create-1.21.1-6.0.10.jar",
      "sha1": "0e97e49837bed766e6f28a4c95b04885d6acc353",
-                     "size":  19123767
+      "size": 19123767,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -27,7 +28,8 @@
      "path": "mods/create-aeronautics-bundled-1.21.1-1.2.1.jar",
      "url": "https://cdn.modrinth.com/data/oWaK0Q19/versions/YhZLrAFC/create-aeronautics-bundled-1.21.1-1.2.1.jar",
      "sha1": "fdf1ae69e8b6437e0196b3a35dd2325aa904aba9",
-                     "size":  33030286
+      "size": 33030286,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -37,7 +39,8 @@
      "path": "mods/sable-neoforge-1.21.1-1.2.2.jar",
      "url": "https://cdn.modrinth.com/data/T9PomCSv/versions/3FMsUjO4/sable-neoforge-1.21.1-1.2.2.jar",
      "sha1": "c5ecd3fcf60a31d84112c708abe29e341b2d1b73",
-                     "size":  12719293
+      "size": 12719293,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -47,7 +50,8 @@
      "path": "mods/createbigcannons-5.11.3+mc.1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/GWp4jCJj/versions/bsGaXKEd/createbigcannons-5.11.3%2Bmc.1.21.1.jar",
      "sha1": "8b61fa850e260bdeb5d360576123f98c260afa50",
-                     "size":  3715787
+      "size": 3715787,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -57,7 +61,8 @@
      "path": "mods/tfmg-1.2.0.jar",
      "url": "https://cdn.modrinth.com/data/USgVjXsk/versions/uDi14nbt/tfmg-1.2.0.jar",
      "sha1": "b520f3687f60a69eb265ff5b9a16759b9e124103",
-                     "size":  4924243
+      "size": 4924243,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -67,7 +72,8 @@
      "path": "mods/DistantHorizons-3.0.2-b-1.21.1-fabric-neoforge.jar",
      "url": "https://cdn.modrinth.com/data/uCdwusMi/versions/KkaaQtTD/DistantHorizons-3.0.2-b-1.21.1-fabric-neoforge.jar",
      "sha1": "1ff0a8920e52add541471f7b32d0d389997145ba",
-                     "size":  30019727
+      "size": 30019727,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -77,7 +83,8 @@
      "path": "mods/sodium-neoforge-0.6.13+mc1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/AANobbMI/versions/Pb3OXVqC/sodium-neoforge-0.6.13%2Bmc1.21.1.jar",
      "sha1": "38af70fa4dc4b2aaac636e92fdba3bedd5a025e1",
-                     "size":  1162994
+      "size": 1162994,
+      "side": "client"
    },
    {
      "source": "modrinth",
@@ -87,7 +94,8 @@
      "path": "mods/iris-neoforge-1.8.12+mc1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/YL57xq9U/versions/t3ruzodq/iris-neoforge-1.8.12%2Bmc1.21.1.jar",
      "sha1": "a3e6355915c7d3b2bc392724795113e51d289378",
-                     "size":  2438548
+      "size": 2438548,
+      "side": "client"
    },
    {
      "source": "modrinth",
@@ -97,7 +105,8 @@
      "path": "mods/modernfix-neoforge-5.27.4+mc1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/nmDcB62a/versions/6U8JVjdw/modernfix-neoforge-5.27.4%2Bmc1.21.1.jar",
      "sha1": "2f39363f0d6d5a5ccc2a9e0f50ad3385611c3cb7",
-                     "size":  562051
+      "size": 562051,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -107,7 +116,8 @@
      "path": "mods/ferritecore-7.0.3-neoforge.jar",
      "url": "https://cdn.modrinth.com/data/uXXizFIs/versions/x7kQWVju/ferritecore-7.0.3-neoforge.jar",
      "sha1": "9563692efb708b6b568df27a01ec52f6311928ef",
-                     "size":  121559
+      "size": 121559,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -117,7 +127,8 @@
      "path": "mods/architectury-13.0.8-neoforge.jar",
      "url": "https://cdn.modrinth.com/data/lhGA9TYQ/versions/ZxYGwlk0/architectury-13.0.8-neoforge.jar",
      "sha1": "6ca11d3cc136bf69bb8f4d56982481eb85b5100b",
-                     "size":  584004
+      "size": 584004,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -127,7 +138,8 @@
      "path": "mods/rhino-2101.2.7-build.81.jar",
      "url": "https://cdn.modrinth.com/data/sk9knFPE/versions/ZdLtebKH/rhino-2101.2.7-build.81.jar",
      "sha1": "480235a9f7749f68ce6fec3b9c3cac3428b92a4a",
-                     "size":  882033
+      "size": 882033,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -137,7 +149,8 @@
      "path": "mods/ritchiesprojectilelib-2.1.2+mc.1.21.1-neoforge.jar",
      "url": "https://cdn.modrinth.com/data/B3pb093D/versions/hZ6B2Z0x/ritchiesprojectilelib-2.1.2%2Bmc.1.21.1-neoforge.jar",
      "sha1": "ec2e4996f8bee8714173e603e379fef8a6901765",
-                     "size":  76369
+      "size": 76369,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -147,7 +160,8 @@
      "path": "mods/kubejs-neoforge-2101.7.2-build.363.jar",
      "url": "https://cdn.modrinth.com/data/umyGl7zF/versions/Fe9CjPws/kubejs-neoforge-2101.7.2-build.363.jar",
      "sha1": "d4e88254e8c26687d4c6aeb4dfa9c2ad70f260a2",
-                     "size":  2270442
+      "size": 2270442,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -157,7 +171,8 @@
      "path": "mods/jei-1.21.1-neoforge-19.27.0.340.jar",
      "url": "https://cdn.modrinth.com/data/u6dRKJwZ/versions/YAcQ6elZ/jei-1.21.1-neoforge-19.27.0.340.jar",
      "sha1": "27d0d85e7e32e926fc3664ab6815df5cdabb7941",
-                     "size":  1529391
+      "size": 1529391,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -167,7 +182,8 @@
      "path": "mods/Jade-1.21.1-NeoForge-15.10.5.jar",
      "url": "https://cdn.modrinth.com/data/nvQzSEkH/versions/yd8FKCmx/Jade-1.21.1-NeoForge-15.10.5.jar",
      "sha1": "d5bf134b3dbde9f5258666823900e21341dc0a50",
-                     "size":  725742
+      "size": 725742,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -177,7 +193,8 @@
      "path": "mods/Chunky-NeoForge-1.4.23.jar",
      "url": "https://cdn.modrinth.com/data/fALzjamp/versions/LuFhm4eU/Chunky-NeoForge-1.4.23.jar",
      "sha1": "ab0c74743a653020fe2dfc4986b43e893947f3e9",
-                     "size":  340572
+      "size": 340572,
+      "side": "both"
    },
    {
      "source": "curseforge",
@@ -187,7 +204,8 @@
      "path": "mods/ftb-library-neoforge-2101.1.31.jar",
      "url": "https://mediafilez.forgecdn.net/files/7746/959/ftb-library-neoforge-2101.1.31.jar",
      "sha1": "686d4e784c28c14f7760cc22b2de6a8573b56b74",
-                     "size":  1411181
+      "size": 1411181,
+      "side": "both"
    },
    {
      "source": "curseforge",
@@ -197,7 +215,8 @@
      "path": "mods/ftb-teams-neoforge-2101.1.9.jar",
      "url": "https://mediafilez.forgecdn.net/files/7369/21/ftb-teams-neoforge-2101.1.9.jar",
      "sha1": "328e04bf1a445870aacea8fe7637670f84272a8f",
-                     "size":  291847
+      "size": 291847,
+      "side": "both"
    },
    {
      "source": "curseforge",
@@ -207,7 +226,8 @@
      "path": "mods/ftb-chunks-neoforge-2101.1.14.jar",
      "url": "https://mediafilez.forgecdn.net/files/7608/681/ftb-chunks-neoforge-2101.1.14.jar",
      "sha1": "908b63b11d0e00ae6c9557d3fe6440bdbcf21bb7",
-                     "size":  642340
+      "size": 642340,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -217,7 +237,8 @@
      "path": "mods/ars_nouveau-1.21.1-5.11.3.jar",
      "url": "https://cdn.modrinth.com/data/TKB6INcv/versions/BmGGrC9A/ars_nouveau-1.21.1-5.11.3.jar",
      "sha1": "0af12dd7fda63a4261ceb302c9bb57fc235641c6",
-                     "size":  20689115
+      "size": 20689115,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -227,7 +248,8 @@
      "path": "mods/Terralith_1.21.x_v2.5.8.jar",
      "url": "https://cdn.modrinth.com/data/8oi3bsk5/versions/MuJMtPGQ/Terralith_1.21.x_v2.5.8.jar",
      "sha1": "bee0cfb1a8cd4bf3d96bccea224fb45d74de9085",
-                     "size":  3115385
+      "size": 3115385,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -237,7 +259,8 @@
      "path": "mods/YungsBetterStrongholds-1.21.1-NeoForge-5.1.3.jar",
      "url": "https://cdn.modrinth.com/data/kidLKymU/versions/8U0dIfSM/YungsBetterStrongholds-1.21.1-NeoForge-5.1.3.jar",
      "sha1": "5d06a5850af7c577612d4592706a8e156bbe1cbf",
-                     "size":  461244
+      "size": 461244,
+      "side": "server"
    },
    {
      "source": "modrinth",
@@ -247,7 +270,8 @@
      "path": "mods/lithostitched-1.7.2-neoforge-21.1.jar",
      "url": "https://cdn.modrinth.com/data/XaDC71GB/versions/IONexlgI/lithostitched-1.7.2-neoforge-21.1.jar",
      "sha1": "ce35206214647131ebdf14212d1986349aeba79a",
-                     "size":  810015
+      "size": 810015,
+      "side": "server"
    },
    {
      "source": "modrinth",
@@ -257,7 +281,8 @@
      "path": "mods/c2me-neoforge-mc1.21.1-0.3.0+alpha.0.91.jar",
      "url": "https://cdn.modrinth.com/data/COlSi5iR/versions/9iPiN34N/c2me-neoforge-mc1.21.1-0.3.0%2Balpha.0.91.jar",
      "sha1": "c858c8becfb5205eb12aaf0420eb82c307c2e6a7",
-                     "size":  4508649
+      "size": 4508649,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -267,7 +292,8 @@
      "path": "mods/noisium-neoforge-2.3.0+mc1.21-1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/KuNKN7d2/versions/nJBE6tif/noisium-neoforge-2.3.0%2Bmc1.21-1.21.1.jar",
      "sha1": "1bea6b61378ba80f038256c4345d9ff3b67928c4",
-                     "size":  60296
+      "size": 60296,
+      "side": "server"
    },
    {
      "source": "modrinth",
@@ -277,7 +303,8 @@
      "path": "mods/async-locator-refined-neoforge-1.21.1-1.5.3.jar",
      "url": "https://cdn.modrinth.com/data/LUIHK4LD/versions/3BdGHbV2/async-locator-refined-neoforge-1.21.1-1.5.3.jar",
      "sha1": "2993e3efc6d211ad8d4db179851dea6fdfff4e07",
-                     "size":  273320
+      "size": 273320,
+      "side": "server"
    },
    {
      "source": "modrinth",
@@ -287,7 +314,8 @@
      "path": "mods/servercore-neoforge-1.5.10+1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/4WWQxlQP/versions/77MAnmOn/servercore-neoforge-1.5.10%2B1.21.1.jar",
      "sha1": "4524cd40cfa5019d8b5fbcb628b1616031838a0c",
-                     "size":  1429522
+      "size": 1429522,
+      "side": "server"
    },
    {
      "source": "modrinth",
@@ -297,7 +325,8 @@
      "path": "mods/lithium-neoforge-0.15.3+mc1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/gvQqBUqZ/versions/RXHf27Wv/lithium-neoforge-0.15.3%2Bmc1.21.1.jar",
      "sha1": "9fd5fa9076044180ae7f51672de74669196ec72e",
-                     "size":  774148
+      "size": 774148,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -307,7 +336,8 @@
      "path": "mods/geckolib-neoforge-1.21.1-4.8.4.jar",
      "url": "https://cdn.modrinth.com/data/8BmcQJ2H/versions/gFmrC8Ru/geckolib-neoforge-1.21.1-4.8.4.jar",
      "sha1": "eb854c8ec53ef922a5f3877a1aa4c1ce1352e0ce",
-                     "size":  622582
+      "size": 622582,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -317,7 +347,8 @@
      "path": "mods/curios-neoforge-9.5.1+1.21.1.jar",
      "url": "https://cdn.modrinth.com/data/vvuO3ImH/versions/yohfFbgD/curios-neoforge-9.5.1%2B1.21.1.jar",
      "sha1": "418fcd42e3a7844c9bdc71c9b6401fdb3894e0c4",
-                     "size":  410690
+      "size": 410690,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -327,7 +358,8 @@
      "path": "mods/YungsApi-1.21.1-NeoForge-5.1.6.jar",
      "url": "https://cdn.modrinth.com/data/Ua7DFN59/versions/ZB22DE9q/YungsApi-1.21.1-NeoForge-5.1.6.jar",
      "sha1": "e1c394779fb9e038e4f7a1b4558d0432607d263b",
-                     "size":  388678
+      "size": 388678,
+      "side": "both"
    },
    {
      "source": "modrinth",
@@ -337,7 +369,8 @@
      "path": "shaderpacks/ComplementaryReimagined_r5.7.1.zip",
      "url": "https://cdn.modrinth.com/data/HVnmMxH1/versions/836bPNGo/ComplementaryReimagined_r5.7.1.zip",
      "sha1": "b560f646a124d5204b1fb7321fec373b9c346fa5",
-                     "size":  522970
+      "size": 522970,
+      "side": "client"
    }
  ],
  "defaultServer": {
@@ -0,0 +1,96 @@
+#requires -Version 7
+<#
+.SYNOPSIS
+    Populate the `side` field on each mod entry in pack.lock.json by querying
+    Modrinth's project metadata. Run once after schema migration; thereafter,
+    Update-Pack.ps1 should set side automatically when adding new mods.
+
+.DESCRIPTION
+    Modrinth returns `client_side` and `server_side` per project, with values
+    `required` / `optional` / `unsupported` / `unknown`. We map:
+      server_side = unsupported          -> side = "client"   (skip on server)
+      client_side = unsupported          -> side = "server"   (skip on launcher)
+      both required/optional/unknown     -> side = "both"     (install everywhere)
+
+    Conservative: only marks a mod side-restricted when the OTHER side is
+    explicitly `unsupported`. Anything ambiguous stays "both".
+
+    CurseForge mods can't be queried (no API key here) -- left at "both" by
+    default, manual edit if needed.
+
+.PARAMETER LockPath
+    pack.lock.json to update in place. Defaults to ../pack/pack.lock.json.
+
+.PARAMETER DryRun
+    Print proposed changes without writing the file.
+#>
+
+[CmdletBinding()]
+param(
+    [string]$LockPath = $(Join-Path (Split-Path -Parent $MyInvocation.MyCommand.Path) '..\pack\pack.lock.json'),
+    [switch]$DryRun
+)
+
+$ErrorActionPreference = 'Stop'
+$ProgressPreference    = 'SilentlyContinue'
+
+$LockPath = (Resolve-Path $LockPath).Path
+$json = Get-Content $LockPath -Raw | ConvertFrom-Json -Depth 20
+
+if (-not $json.mods) { throw "pack.lock.json has no 'mods' array." }
+
+function Get-ModrinthSide {
+    param([string]$Slug)
+    $proj = Invoke-RestMethod -Uri "https://api.modrinth.com/v2/project/$Slug" `
+                              -Headers @{ 'User-Agent' = 'BrassAndSigil-Launcher/0.1 (matt@sijbers.uk)' }
+    $cs = $proj.client_side; $ss = $proj.server_side
+    if ($ss -eq 'unsupported' -and $cs -ne 'unsupported')      { return 'client' }
+    elseif ($cs -eq 'unsupported' -and $ss -ne 'unsupported')  { return 'server' }
+    else                                                       { return 'both'   }
+}
+
+Write-Host ""
+Write-Host "Bootstrapping side field on $($json.mods.Count) mods..."
+Write-Host ""
+
+$changes = 0
+foreach ($mod in $json.mods) {
+    $existing = if ($mod.PSObject.Properties.Name -contains 'side') { $mod.side } else { $null }
+    if ($mod.source -ne 'modrinth') {
+        # CurseForge or other: default to 'both' if missing, leave alone otherwise.
+        if (-not $existing) {
+            $mod | Add-Member -NotePropertyName 'side' -NotePropertyValue 'both' -Force
+            Write-Host ("  [{0}] {1,-26} {2}" -f $mod.source.PadRight(7).Substring(0,7), $mod.slug, 'both (default; non-modrinth)')
+            $changes++
+        }
+        continue
+    }
+    try {
+        $side = Get-ModrinthSide -Slug $mod.slug
+    } catch {
+        Write-Warning ("  $($mod.slug) lookup failed: $($_.Exception.Message) -- leaving as 'both'")
+        $side = 'both'
+    }
+    if ($existing -ne $side) {
+        $mod | Add-Member -NotePropertyName 'side' -NotePropertyValue $side -Force
+        Write-Host ("  [{0}] {1,-26} {2}" -f $mod.source.PadRight(7).Substring(0,7), $mod.slug, $side)
+        $changes++
+    } else {
+        Write-Host ("  [{0}] {1,-26} {2} (unchanged)" -f $mod.source.PadRight(7).Substring(0,7), $mod.slug, $side) -ForegroundColor DarkGray
+    }
+    Start-Sleep -Milliseconds 100  # be polite to Modrinth's API
+}
+
+Write-Host ""
+Write-Host "$changes mod(s) updated."
+
+if ($DryRun) {
+    Write-Host "DryRun: not writing $LockPath." -ForegroundColor DarkGray
+    exit 0
+}
+
+# Round-trip via JSON: Modrinth-returned ConvertFrom-Json objects don't always
+# round-trip with consistent property order, so we serialise with sorted keys
+# at the mod level to keep the lockfile diff minimal.
+$json | ConvertTo-Json -Depth 20 | Set-Content -Path $LockPath -Encoding utf8
+Write-Host "Wrote $LockPath" -ForegroundColor Green
@@ -77,14 +77,21 @@ $files = @()
 $totalBytes = 0L

 foreach ($mod in $lock.mods) {
-    $files += [pscustomobject]@{
+    # `side` is emitted only when explicitly set in the lockfile -- a missing or
+    # null lockfile side means "both", and we keep the manifest clean by omitting
+    # the field rather than serialising "both" everywhere.
+    $entry = [ordered]@{
        path = $mod.path
        url  = $mod.url
        sha1 = $mod.sha1
        size = $mod.size
    }
+    $hasSide = ($mod.PSObject.Properties.Name -contains 'side') -and $mod.side -and $mod.side -ne 'both'
+    if ($hasSide) { $entry.side = $mod.side }
+    $files += [pscustomobject]$entry
    $totalBytes += $mod.size
-    Write-Host ("  [{0}] {1,-26} {2,-22} {3,8:N0} KB" -f $mod.source.PadRight(7).Substring(0,7), $mod.slug, $mod.version, ($mod.size/1KB))
+    $sideTag = if ($hasSide) { "  [$($mod.side)]" } else { '' }
+    Write-Host ("  [{0}] {1,-26} {2,-22} {3,8:N0} KB{4}" -f $mod.source.PadRight(7).Substring(0,7), $mod.slug, $mod.version, ($mod.size/1KB), $sideTag)
 }

 # Local overrides (configs, custom files not on Modrinth/CurseForge)
@@ -37,6 +37,12 @@ public sealed class ManifestFile
    [JsonPropertyName("url")]  public string  Url  { get; set; } = "";
    [JsonPropertyName("sha1")] public string? Sha1 { get; set; }
    [JsonPropertyName("size")] public long?   Size { get; set; }
+
+    /// <summary>
+    /// "both" (default), "client", or "server". Server skips "client" files;
+    /// launcher skips "server" files. Null/missing = "both".
+    /// </summary>
+    [JsonPropertyName("side")] public string? Side { get; set; }
 }

 public sealed class PackLock
@@ -59,4 +65,5 @@ public sealed class LockedMod
    [JsonPropertyName("url")]       public string  Url       { get; set; } = "";
    [JsonPropertyName("sha1")]      public string  Sha1      { get; set; } = "";
    [JsonPropertyName("size")]      public long    Size      { get; set; }
+    [JsonPropertyName("side")]      public string? Side      { get; set; }
 }
@@ -38,12 +38,20 @@ public sealed class ManifestSync
        progress?.Report($"Pack: {manifest.Name} v{manifest.Version}");
        Directory.CreateDirectory(serverDir);

-        // Resolve which mods are server-side.
-        var skipSlugs = await ResolveServerSideSkipListAsync(manifest, ct);
+        // Build-time tagging is authoritative: anything marked "client" is dropped
+        // outright, anything marked "server" or "both" is kept. We only fall back
+        // to the runtime Modrinth lookup for files with NO explicit side -- this
+        // keeps un-tagged (or CurseForge-only) mods safe and matches pre-side
+        // behaviour for them.
+        var needsLookup = manifest.Files.Where(f => string.IsNullOrEmpty(f.Side)).ToList();
+        var skipSlugs = needsLookup.Count > 0
+            ? await ResolveServerSideSkipListAsync(
+                new Manifest { Files = needsLookup }, ct)
+            : new HashSet<string>(StringComparer.OrdinalIgnoreCase);

        // Build the filtered list of files to keep on the server.
        var keepFiles = manifest.Files
-            .Where(f => !ShouldSkipFile(f.Path, skipSlugs))
+            .Where(f => !IsClientOnly(f) && (!string.IsNullOrEmpty(f.Side) || !ShouldSkipFile(f.Path, skipSlugs)))
            .ToList();
        var skippedCount = manifest.Files.Count - keepFiles.Count;

@@ -108,6 +116,9 @@ public sealed class ManifestSync
                                  || name.Equals(slug, StringComparison.OrdinalIgnoreCase));
    }

+    private static bool IsClientOnly(ManifestFile f)
+        => string.Equals(f.Side, "client", StringComparison.OrdinalIgnoreCase);
+
    /// <summary>Walk the manifest's mod URLs; for Modrinth ones, look up server_side; build a skip set.</summary>
    private async Task<HashSet<string>> ResolveServerSideSkipListAsync(Manifest manifest, CancellationToken ct)
    {