diff --git a/Hooks/ModCardHandOutlinePatchHelper.cs b/Hooks/ModCardHandOutlinePatchHelper.cs
new file mode 100644
index 0000000..2287430
--- /dev/null
+++ b/Hooks/ModCardHandOutlinePatchHelper.cs
@@ -0,0 +1,53 @@
+using Godot;
+using HarmonyLib;
+using MegaCrit.Sts2.Core.Combat;
+using MegaCrit.Sts2.Core.Models;
+using MegaCrit.Sts2.Core.Nodes.Cards.Holders;
+
+namespace BaseLib.Hooks;
+
+internal static class ModCardHandOutlinePatchHelper
+{
+    internal static bool TryGetRule(NHandCardHolder holder, out CardModel model, out ModCardHandOutlineRule rule)
+    {
+        model = null!;
+        rule = default;
+
+        if (!holder.IsNodeReady() || holder.CardNode?.Model is not { } m)
+            return false;
+
+        var evaluated = ModCardHandOutlineRegistry.EvaluateBest(m);
+        if (evaluated is not { } r)
+            return false;
+
+        model = m;
+        rule = r;
+        return true;
+    }
+
+    internal static void ApplyHighlight(NHandCardHolder holder, CardModel model, ModCardHandOutlineRule rule)
+    {
+        if (CombatManager.Instance is not { IsInProgress: true })
+            return;
+
+        var vanillaShow = model.CanPlay() || model.ShouldGlowRed || model.ShouldGlowGold;
+        var force = rule.VisibleWhenUnplayable && !vanillaShow;
+        if (!vanillaShow && !force)
+            return;
+
+        var highlight = holder.CardNode!.CardHighlight;
+        if (force)
+            highlight.AnimShow();
+
+        highlight.Modulate = rule.Color;
+    }
+
+    internal static void ApplyFlash(NHandCardHolder holder, ModCardHandOutlineRule rule)
+    {
+        if (AccessTools.Field(typeof(NHandCardHolder), "_flash")?.GetValue(holder) is not Control flash ||
+            !GodotObject.IsInstanceValid(flash))
+            return;
+
+        flash.Modulate = rule.Color;
+    }
+}
\ No newline at end of file
diff --git a/Hooks/ModCardHandOutlineRegistry.cs b/Hooks/ModCardHandOutlineRegistry.cs
new file mode 100644
index 0000000..01a02e0
--- /dev/null
+++ b/Hooks/ModCardHandOutlineRegistry.cs
@@ -0,0 +1,194 @@
+using System.Collections.Concurrent;
+using Godot;
+using MegaCrit.Sts2.Core.Models;
+using MegaCrit.Sts2.Core.Nodes.Cards.Holders;
+
+namespace BaseLib.Hooks;
+
+/// <summary>
+///     Per–card-type custom outline colors for the in-hand <see cref="MegaCrit.Sts2.Core.Nodes.Cards.NCardHighlight" />.
+///     Applied after vanilla <see cref="NHandCardHolder.UpdateCard" /> via Harmony. Foreign providers (e.g. RitsuLib)
+///     merge via <see cref="RegisterForeign" />.
+/// </summary>
+public static class ModCardHandOutlineRegistry
+{
+    private static readonly Func<CardModel, bool> ForeignPredicateAlreadySatisfied = static _ => true;
+
+    private static int _sequence;
+    private static int _foreignOrder;
+
+    private static readonly ConcurrentDictionary<Type, List<RegisteredRule>> RulesByCardType = new();
+    private static readonly Lock ForeignLock = new();
+    private static readonly List<ForeignProvider> ForeignProviders = [];
+
+    /// <summary>
+    ///     Registers a rule for <typeparamref name="TCard" />.
+    /// </summary>
+    public static void Register<TCard>(ModCardHandOutlineRule rule) where TCard : CardModel
+    {
+        Register(typeof(TCard), rule);
+    }
+
+    /// <summary>
+    ///     Registers a rule for <paramref name="cardType" /> (concrete <see cref="CardModel" /> subtype).
+    /// </summary>
+    public static void Register(Type cardType, ModCardHandOutlineRule rule)
+    {
+        ArgumentNullException.ThrowIfNull(cardType);
+        ArgumentNullException.ThrowIfNull(rule.When);
+
+        if (cardType.IsAbstract || !typeof(CardModel).IsAssignableFrom(cardType))
+            throw new ArgumentException(
+                $"Type '{cardType.FullName}' must be a concrete subtype of {typeof(CardModel).FullName}.",
+                nameof(cardType));
+
+        var seq = Interlocked.Increment(ref _sequence);
+        var wrapped = new RegisteredRule(rule, seq);
+
+        RulesByCardType.AddOrUpdate(
+            cardType,
+            _ => [wrapped],
+            (_, existing) =>
+            {
+                var copy = new List<RegisteredRule>(existing) { wrapped };
+                return copy;
+            });
+    }
+
+    /// <summary>
+    ///     Merges outline evaluation from another assembly (e.g. RitsuLib). The delegate must return
+    ///     <see langword="null" /> when no rule applies, otherwise paint fields only — the foreign registry has already
+    ///     evaluated <c>When</c>. Uses <see cref="ValueTuple" /> so the boundary stays a nullable struct (no heap boxing).
+    /// </summary>
+    public static void RegisterForeign(string modId, string sourceId,
+        Func<CardModel, (Color Color, int Priority, bool VisibleWhenUnplayable)?> evaluateBestFromForeign)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(modId);
+        ArgumentException.ThrowIfNullOrWhiteSpace(sourceId);
+        ArgumentNullException.ThrowIfNull(evaluateBestFromForeign);
+
+        var order = Interlocked.Increment(ref _foreignOrder);
+        lock (ForeignLock)
+        {
+            ForeignProviders.Add(new ForeignProvider(evaluateBestFromForeign, order));
+        }
+    }
+
+    /// <summary>
+    ///     Clears all rules and foreign providers (tests / tooling).
+    /// </summary>
+    public static void ClearForTests()
+    {
+        RulesByCardType.Clear();
+        lock (ForeignLock)
+        {
+            ForeignProviders.Clear();
+        }
+    }
+
+    /// <summary>
+    ///     Applies the best matching registered outline for this holder.
+    /// </summary>
+    /// <returns><see langword="true" /> if a rule was applied.</returns>
+    public static bool TryRefreshOutlineForHolder(NHandCardHolder? holder)
+    {
+        if (holder == null || !holder.IsNodeReady() || holder.CardNode?.Model is not { } model)
+            return false;
+
+        var rule = EvaluateBest(model);
+        if (!rule.HasValue)
+            return false;
+
+        ModCardHandOutlinePatchHelper.ApplyHighlight(holder, model, rule.Value);
+        return true;
+    }
+
+    internal static ModCardHandOutlineRule? EvaluateBest(CardModel model)
+    {
+        var local = EvaluateLocalBest(model);
+        ForeignCandidate? foreignBest = null;
+
+        List<ForeignProvider> snapshot;
+        lock (ForeignLock)
+        {
+            snapshot = [..ForeignProviders];
+        }
+
+        foreach (var provider in snapshot)
+        {
+            (Color Color, int Priority, bool VisibleWhenUnplayable)? foreignPaint;
+            try
+            {
+                foreignPaint = provider.Evaluate(model);
+            }
+            catch
+            {
+                continue;
+            }
+
+            if (foreignPaint is not { } paint)
+                continue;
+
+            var candidate = new ModCardHandOutlineRule(ForeignPredicateAlreadySatisfied, paint.Color, paint.Priority,
+                paint.VisibleWhenUnplayable);
+
+            if (foreignBest is null ||
+                RuleWins(candidate, provider.Order, foreignBest.Value.Rule, foreignBest.Value.Order))
+                foreignBest = new ForeignCandidate(candidate, provider.Order);
+        }
+
+        switch (local)
+        {
+            case null when foreignBest is null:
+                return null;
+            case null:
+                return foreignBest.Value.Rule;
+        }
+
+        if (foreignBest is null)
+            return local.Value.Rule;
+
+        return RuleWins(foreignBest.Value.Rule, foreignBest.Value.Order, local.Value.Rule, local.Value.Sequence)
+            ? foreignBest.Value.Rule
+            : local.Value.Rule;
+    }
+
+    private static RegisteredRule? EvaluateLocalBest(CardModel model)
+    {
+        RegisteredRule? best = null;
+
+        for (var t = model.GetType();
+             t != null && typeof(CardModel).IsAssignableFrom(t);
+             t = t.BaseType)
+        {
+            if (!RulesByCardType.TryGetValue(t, out var list))
+                continue;
+
+            foreach (var entry in list.Where(entry => entry.Rule.When(model)).Where(entry => best is null
+                         || entry.Rule.Priority > best.Value.Rule.Priority
+                         || (entry.Rule.Priority == best.Value.Rule.Priority &&
+                             entry.Sequence > best.Value.Sequence)))
+                best = entry;
+        }
+
+        return best;
+    }
+
+    private static bool RuleWins(ModCardHandOutlineRule challenger, int challengerOrder,
+        ModCardHandOutlineRule incumbent,
+        int incumbentOrder)
+    {
+        if (challenger.Priority != incumbent.Priority)
+            return challenger.Priority > incumbent.Priority;
+
+        return challengerOrder > incumbentOrder;
+    }
+
+    private readonly record struct RegisteredRule(ModCardHandOutlineRule Rule, int Sequence);
+
+    private readonly record struct ForeignProvider(
+        Func<CardModel, (Color Color, int Priority, bool VisibleWhenUnplayable)?> Evaluate,
+        int Order);
+
+    private readonly record struct ForeignCandidate(ModCardHandOutlineRule Rule, int Order);
+}
\ No newline at end of file
diff --git a/Hooks/ModCardHandOutlineRule.cs b/Hooks/ModCardHandOutlineRule.cs
new file mode 100644
index 0000000..0595ef4
--- /dev/null
+++ b/Hooks/ModCardHandOutlineRule.cs
@@ -0,0 +1,24 @@
+using Godot;
+using MegaCrit.Sts2.Core.Models;
+
+namespace BaseLib.Hooks;
+
+/// <summary>
+///     Custom hand-card outline tint for <see cref="MegaCrit.Sts2.Core.Nodes.Cards.NCardHighlight" /> after vanilla
+///     playable / gold / red. Register with <see cref="ModCardHandOutlineRegistry" />.
+/// </summary>
+/// <param name="When">When this returns true for the card instance, the outline color may apply.</param>
+/// <param name="Color">Godot modulate color (alpha is respected; vanilla highlights use ~0.98).</param>
+/// <param name="Priority">
+///     When several rules match, the highest <paramref name="Priority" /> wins; ties favor the most recently registered
+///     rule.
+/// </param>
+/// <param name="VisibleWhenUnplayable">
+///     If true, the highlight is forced visible with this color even when the card is not playable and vanilla would not
+///     show gold/red (still only while combat is in progress).
+/// </param>
+public readonly record struct ModCardHandOutlineRule(
+    Func<CardModel, bool> When,
+    Color Color,
+    int Priority = 0,
+    bool VisibleWhenUnplayable = false);
\ No newline at end of file
diff --git a/Patches/Cards/NHandCardHolderHandOutlinePatches.cs b/Patches/Cards/NHandCardHolderHandOutlinePatches.cs
new file mode 100644
index 0000000..c13dc30
--- /dev/null
+++ b/Patches/Cards/NHandCardHolderHandOutlinePatches.cs
@@ -0,0 +1,31 @@
+using BaseLib.Hooks;
+using HarmonyLib;
+using MegaCrit.Sts2.Core.Nodes.Cards.Holders;
+
+namespace BaseLib.Patches.Cards;
+
+[HarmonyPatch(typeof(NHandCardHolder), nameof(NHandCardHolder.UpdateCard))]
+internal static class NHandCardHolderUpdateCardHandOutlinePatch
+{
+    [HarmonyPostfix]
+    public static void Postfix(NHandCardHolder __instance)
+    {
+        if (!ModCardHandOutlinePatchHelper.TryGetRule(__instance, out var model, out var rule))
+            return;
+
+        ModCardHandOutlinePatchHelper.ApplyHighlight(__instance, model, rule);
+    }
+}
+
+[HarmonyPatch(typeof(NHandCardHolder), nameof(NHandCardHolder.Flash))]
+internal static class NHandCardHolderFlashHandOutlinePatch
+{
+    [HarmonyPostfix]
+    public static void Postfix(NHandCardHolder __instance)
+    {
+        if (!ModCardHandOutlinePatchHelper.TryGetRule(__instance, out _, out var rule))
+            return;
+
+        ModCardHandOutlinePatchHelper.ApplyFlash(__instance, rule);
+    }
+}
\ No newline at end of file