fix: Harden Advanced Search: crash-safety, autosave, correct results & worker fixes (#2543)

## Summary

Hardens the **Advanced Search** engine (`Projects/UOContent/Engines/Advanced Search/`) — the GM entity finder that fans searches across background worker threads. A code review surfaced 14 defects (A–N), including a shard-crasher reachable from a single admin typo and a path that silently disables autosave for the rest of the shard's uptime. Each behavioral fix ships with a test.

Full `UOContent.Tests` suite: **530/530 green** (21 new AdvancedSearch tests).

## Fixes

### Crash / data-loss
- **A — Shard crash on a malformed Property Test.** `AdvancedSearchThreadWorker.Execute` had no `try/catch` and the worker `Thread` is foreground, so a parse throw (`Hits>abc`, `Layer=onehanded` — `Enum.Parse` was case-sensitive, `Hits>1@` — empty sub-expression indexing) terminated the process. Now: `ParseValue`/`CompareValues` use `TryParse`/`Enum.TryParse(ignoreCase)` and return no-match instead of throwing; the per-entity filter is wrapped in `try/catch` (logs + skips); empty expressions are guarded.
- **C — Overlapping searches corrupt state + brick autosave.** `_threadWorkers`/`_threadId` were `static` but `DoSearch` is an instance method; a second search (double-click / two admins) stomped shared worker state and could leave a drain waiting forever on the shared `AutoResetEvent`, so `AutoSave.SavesEnabled` was never restored. Now: an `Interlocked` re-entrancy guard rejects concurrent searches.
- **G — Autosave restore not guaranteed.** The restore lived only in the success callback. Now it's in a `finally` (plus an outer `catch` covering the synchronous setup and a `catch` on the drain body), so autosave + the guard are always released.

### Wrong results
- **D — `@`/`|` operator precedence.** `a@b|c` evaluated as `a && (b || c)` instead of `(a && b) || c`. OR now binds looser than AND (`AdvancedSearchUtilities.EvaluateBoolean`, unit-tested).
- **E — Descending sort, partial last page rendered blank** (the index decreased in descending mode and the `break` early-out killed the loop). Now a bounded `VisibleCount`-driven loop renders the last page in both directions.
- **F — Deleted entities** were not skipped (ghost rows). Now `DoEntitySearch` skips `entity.Deleted`.
- **N — Reference-type comparisons** threw (`Comparer<T>.Default.Compare` on non-`IComparable`) and compared references to a string. Now equality is by value and ordering is guarded to `IComparable` (no throw).

### Worker perf / hardening
- **H** busy-spin → `Thread.Yield()` in the drain; **I** `GetProperties()` cached per `Type`; **J** `HandleValidInternal` moved behind the cheap map/range/region filters; **K** worker threads are `IsBackground` + `Exit()` tolerates an already-terminated worker; **L** `_filter == null` guard; **M** consistent `Volatile` access on `_pause`/`_exit`.

### Documented
- **B** — the residual worker/event-loop read race is documented on `AdvancedSearchThreadWorker`: workers read live entity state concurrently with the loop, so value-type reads may be stale-but-safe and getter exceptions are swallowed; fully eliminating it would require snapshotting entity fields on the main thread (deferred).

## Notes
- New test-only seams (`TryBeginSearch`/`EndSearch`/`IsSearchInProgress`/`VisibleCount`/`TryParseValue`/`EvaluateBoolean`) are `internal` via the existing `InternalsVisibleTo("UOContent.Tests")`.
- Dead `public ParseValue<T>` removed.
- `ConcurrentDictionary` for the reflection cache is intentional — these workers are genuinely parallel.

Projects/Server.Tests/Tests/Buffers/RawInterpolatedStringHandlerTests.cs

@@ -4,6 +4,7 @@ using Xunit;
 
 namespace Server.Tests.Buffers;
 
+[Collection("Sequential Server Tests")]
 public class RawInterpolatedStringHandlerTests
 {
     [Fact]

Projects/UOContent.Tests/Tests/Engines/AdvancedSearch/AdvancedSearchPagingTests.cs

@@ -0,0 +1,17 @@
+using Server.Engines.AdvancedSearch;
+using Xunit;
+
+namespace UOContent.Tests;
+
+public class AdvancedSearchPagingTests
+{
+    [Theory]
+    [InlineData(20, 0, 18, 18)]  // full first page
+    [InlineData(20, 18, 18, 2)]  // partial last page -> 2 visible (bug rendered 0 in descending)
+    [InlineData(5, 0, 18, 5)]
+    [InlineData(0, 0, 18, 0)]
+    public void VisibleCount_IsCorrect(int total, int from, int max, int expected)
+    {
+        Assert.Equal(expected, AdvancedSearchGump.VisibleCount(total, from, max));
+    }
+}

Projects/UOContent.Tests/Tests/Engines/AdvancedSearch/AdvancedSearchTypesTests.cs

@@ -0,0 +1,27 @@
+using Server;
+using Server.Engines.AdvancedSearch;
+using Xunit;
+
+namespace UOContent.Tests;
+
+[Collection("Sequential UOContent Tests")]
+public class AdvancedSearchTypesTests
+{
+    [Fact]
+    public void CompareValues_Poison_ReferenceTypeParsedViaTypes()
+    {
+        PoisonKinds.Configure(); // idempotent; registers Lesser..Lethal now that Core.Expansion is set
+
+        // Poison is a reference type implementing ISpanParsable; it can't use the compile-time span
+        // path and routes through the shared Server.Types converter. Poison.Parse returns the
+        // registered singleton, so "= Lethal" is a reference-equality match — this is the case that
+        // previously compared a Poison against the raw string and always failed.
+        var prop = Poison.Lethal;
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(Poison), prop, "Lethal", "="));
+        Assert.False(AdvancedSearchUtilities.CompareValues(typeof(Poison), prop, "Lesser", "="));
+
+        var ex = Record.Exception(() =>
+            Assert.False(AdvancedSearchUtilities.CompareValues(typeof(Poison), prop, "notapoison", "=")));
+        Assert.Null(ex);
+    }
+}

Projects/UOContent.Tests/Tests/Engines/AdvancedSearch/AdvancedSearchUtilitiesTests.cs

@@ -0,0 +1,119 @@
+using System;
+using Server;
+using Server.Engines.AdvancedSearch;
+using Xunit;
+
+namespace UOContent.Tests;
+
+public class AdvancedSearchUtilitiesTests
+{
+    [Theory]
+    [InlineData("abc")]           // not a number -> was FormatException
+    [InlineData("99999999999")]   // overflows int -> was OverflowException
+    [InlineData("0xZZ")]          // bad hex -> was FormatException
+    public void CompareValues_BadNumeric_ReturnsFalse_DoesNotThrow(string value)
+    {
+        var ex = Record.Exception(() =>
+        {
+            var result = AdvancedSearchUtilities.CompareValues(typeof(int), 5, value, ">");
+            Assert.False(result);
+        });
+        Assert.Null(ex);
+    }
+
+    [Theory]
+    [InlineData("Bogus")]         // not a member -> was ArgumentException
+    [InlineData("onehandedxyz")]  // not a member, even case-insensitively -> was ArgumentException
+    public void CompareValues_BadEnum_ReturnsFalse_DoesNotThrow(string value)
+    {
+        var ex = Record.Exception(() =>
+        {
+            var result = AdvancedSearchUtilities.CompareValues(typeof(Layer), (byte)Layer.OneHanded, value, "=");
+            Assert.False(result);
+        });
+        Assert.Null(ex);
+    }
+
+    [Fact]
+    public void CompareValues_ValidEnum_IgnoresCase()
+    {
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(Layer), (byte)Layer.OneHanded, "onehanded", "="));
+    }
+
+    [Theory]
+    // leaf value is "T"/"F"; evalLeaf returns leaf=="T"
+    [InlineData("T", true)]
+    [InlineData("F", false)]
+    [InlineData("F@F|T", true)]   // (F&&F)||T = T   (buggy code gave F&&(F||T)=F)
+    [InlineData("T|F@F", true)]   // T||(F&&F) = T   (buggy code gave (T||F)&&F=F)
+    [InlineData("T@F", false)]
+    [InlineData("T@T", true)]
+    [InlineData("F|F", false)]
+    public void EvaluateBoolean_Precedence(string expr, bool expected)
+    {
+        // State is unused here; the leaf evaluator just checks the span equals "T".
+        var result = AdvancedSearchUtilities.EvaluateBoolean(expr, 0, static (_, leaf) => leaf.SequenceEqual("T"));
+        Assert.Equal(expected, result);
+    }
+
+    [Fact]
+    public void CompareValues_ReferenceType_EqualityByString_NoThrow()
+    {
+        // A reference-typed property (e.g. RootParent name-ish) compared with "=" should not throw,
+        // and ordering operators must return false rather than throwing.
+        var ex = Record.Exception(() =>
+        {
+            Assert.False(AdvancedSearchUtilities.CompareValues(typeof(object), new object(), "whatever", ">"));
+        });
+        Assert.Null(ex);
+    }
+
+    [Fact]
+    public void CompareValues_TimeSpan_ParsesViaSpanParsable()
+    {
+        // TimeSpan is not IConvertible, so the old Convert.ChangeType fallback threw and silently
+        // returned no-match. ISpanParsable<TimeSpan> parses it correctly.
+        var prop = TimeSpan.FromMinutes(5);
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(TimeSpan), prop, "00:05:00", "="));
+        Assert.False(AdvancedSearchUtilities.CompareValues(typeof(TimeSpan), prop, "00:10:00", "="));
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(TimeSpan), prop, "00:01:00", ">"));
+    }
+
+    [Fact]
+    public void CompareValues_TimeSpan_BadInput_ReturnsFalse_NoThrow()
+    {
+        var ex = Record.Exception(() =>
+            Assert.False(AdvancedSearchUtilities.CompareValues(typeof(TimeSpan), TimeSpan.Zero, "notaspan", "=")));
+        Assert.Null(ex);
+    }
+
+    [Fact]
+    public void CompareValues_Guid_ValueTypeParsedViaTypes()
+    {
+        // Guid is a value type not named by the hot paths; it's parsed via Types (IParsable) and
+        // compared by value.
+        var g = Guid.Parse("00000000-0000-0000-0000-000000000001");
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(Guid), g, "00000000-0000-0000-0000-000000000001", "="));
+        Assert.False(AdvancedSearchUtilities.CompareValues(typeof(Guid), g, "00000000-0000-0000-0000-000000000002", "="));
+    }
+
+    // A reference type with a legacy RunUO-style static Parse(string) and NO IParsable<> interface —
+    // the Faction/Town shape. Types must still discover its Parse by reflection.
+    private sealed class LegacyParseType
+    {
+        public string Value { get; private init; }
+        public static LegacyParseType Parse(string s) => new() { Value = s };
+        public override bool Equals(object obj) => obj is LegacyParseType o && o.Value == Value;
+        public override int GetHashCode() => Value?.GetHashCode() ?? 0;
+    }
+
+    [Fact]
+    public void CompareValues_LegacyParseString_ParsedViaTypes()
+    {
+        // Pre-IParsable types (only a static Parse(string)) must still be searchable: Types binds the
+        // legacy Parse by reflection, so we compare against a real parsed instance, not the raw text.
+        var prop = LegacyParseType.Parse("alpha");
+        Assert.True(AdvancedSearchUtilities.CompareValues(typeof(LegacyParseType), prop, "alpha", "="));
+        Assert.False(AdvancedSearchUtilities.CompareValues(typeof(LegacyParseType), prop, "beta", "="));
+    }
+}

Projects/UOContent.Tests/Tests/Engines/AdvancedSearch/AdvancedSearchWorkerTests.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Concurrent;
+using Server;
+using Server.Engines.AdvancedSearch;
+using Server.Items;
+using Server.Tests;
+using Xunit;
+
+namespace UOContent.Tests;
+
+[Collection("Sequential UOContent Tests")]
+public class AdvancedSearchWorkerTests
+{
+    // An item whose property test path will throw when evaluated.
+    private sealed class ThrowingItem : Item
+    {
+        public ThrowingItem() : base(0x1) { }
+        public ThrowingItem(Serial s) : base(s) { }
+        public string Boom => throw new InvalidOperationException("boom");
+    }
+
+    [Fact]
+    public void Worker_FilterThrows_DoesNotEscape_ReturnsNoMatch()
+    {
+        var worker = new AdvancedSearchThreadWorker();
+        var results = new ConcurrentQueue<AdvancedSearchResult>();
+        var ignore = new ConcurrentQueue<IEntity>();
+        var filter = new AdvancedSearchFilter
+        {
+            FilterPropertyTest = true,
+            PropertyTest = "Boom=1", // reflection GetValue -> throws
+        };
+
+        var item = new ThrowingItem();
+
+        try
+        {
+            worker.Wake(new WorldLocation(Point3D.Zero, Map.Felucca), filter, results, ignore);
+            worker.Push(item);
+            worker.Sleep(); // drains; must not crash the test process
+
+            Assert.Empty(results);
+        }
+        finally
+        {
+            item.Delete();
+            worker.Exit();
+        }
+    }
+
+    [Fact]
+    public void Worker_DeletedEntity_IsSkipped()
+    {
+        var worker = new AdvancedSearchThreadWorker();
+        var results = new ConcurrentQueue<AdvancedSearchResult>();
+        var ignore = new ConcurrentQueue<IEntity>();
+        var filter = new AdvancedSearchFilter(); // no filters -> everything matches
+
+        var item = new Item(0x1);
+        item.Delete();
+
+        try
+        {
+            worker.Wake(new WorldLocation(Point3D.Zero, Map.Felucca), filter, results, ignore);
+            worker.Push(item);
+            worker.Sleep();
+
+            Assert.Empty(results);
+        }
+        finally
+        {
+            worker.Exit();
+        }
+    }
+
+    [Fact]
+    public void DoSearch_IsGuarded_AgainstReentry()
+    {
+        // White-box: flip the guard, assert a second entry is rejected, then clear.
+        // _searchInProgress is process-global static state; release it in finally so a
+        // failed assert here can't leak the guard into other tests.
+        Assert.False(AdvancedSearchGump.IsSearchInProgress);
+        Assert.True(AdvancedSearchGump.TryBeginSearch()); // acquires
+        try
+        {
+            Assert.False(AdvancedSearchGump.TryBeginSearch()); // rejected
+        }
+        finally
+        {
+            AdvancedSearchGump.EndSearch(); // releases
+        }
+
+        Assert.False(AdvancedSearchGump.IsSearchInProgress);
+    }
+}

Projects/UOContent.Tests/Tests/Utilities/TryParseTests.cs

@@ -1,3 +1,4 @@
+using System;
 using Xunit;
 
 namespace Server.Tests.Utility;
@@ -18,4 +19,29 @@ public class TryParseTests
             Assert.Equal(parsedAs, constructed);
         }
     }
+
+    [Theory]
+    // Parsed directly into the target type (INumber<T>.TryParse), not via ulong + Convert.ChangeType.
+    [InlineData(typeof(int), "42", true, 42)]
+    [InlineData(typeof(int), "-5", true, -5)]              // signed values parse directly now
+    [InlineData(typeof(int), "0xFF", true, 255)]          // hex
+    [InlineData(typeof(int), "notanumber", false, null)]
+    [InlineData(typeof(byte), "255", true, (byte)255)]
+    [InlineData(typeof(byte), "256", false, null)]        // out of the byte range
+    [InlineData(typeof(uint), "4294967295", true, 4294967295u)]
+    [InlineData(typeof(long), "-9000000000", true, -9000000000L)]
+    public void TestTryParseNumeric(Type type, string value, bool success, object expected)
+    {
+        var error = Server.Types.TryParse(type, value, out var constructed);
+
+        if (success)
+        {
+            Assert.Null(error);
+            Assert.Equal(expected, constructed);
+        }
+        else
+        {
+            Assert.NotNull(error);
+        }
+    }
 }

Projects/UOContent/Engines/Advanced Search/AdvancedSearchGump.cs

@@ -8,6 +8,7 @@ using Server.Commands;
 using Server.Commands.Generic;
 using Server.Engines.Spawners;
 using Server.Gumps;
+using Server.Logging;
 using Server.Network;
 using Server.Saves;
 
@@ -28,11 +29,19 @@ public enum AdvancedSearchGumpOptions : long
 
 public class AdvancedSearchGump : Gump
 {
+    private static readonly ILogger _logger = LogFactory.GetLogger(typeof(AdvancedSearchGump));
+
     private const int MaxEntries = 18;
 
     private static int _threadId;
     private static AdvancedSearchThreadWorker[] _threadWorkers;
 
+    private static int _searchInProgress;
+
+    internal static bool IsSearchInProgress => Volatile.Read(ref _searchInProgress) == 1;
+    internal static bool TryBeginSearch() => Interlocked.CompareExchange(ref _searchInProgress, 1, 0) == 0;
+    internal static void EndSearch() => Volatile.Write(ref _searchInProgress, 0);
+
     private static void Configure()
     {
         EventSink.Shutdown += Shutdown;
@@ -124,6 +133,10 @@ public class AdvancedSearchGump : Gump
 
     public AdvancedSearchGump() : base(50, 50) => Build();
 
+    // Entries on the current page — bounds the paging loop so a partial last page can't read past the end.
+    internal static int VisibleCount(int total, int displayFrom, int maxEntries) =>
+        Math.Clamp(total - displayFrom, 0, maxEntries);
+
     private void Build()
     {
         const int height = 500;
@@ -319,15 +332,13 @@ public class AdvancedSearchGump : Gump
 
             var allDisplayedSelected = true;
 
-            for (var i = 0; i < MaxEntries; i++)
-            {
-                var offset = SortDescending ? MaxEntries - 1 - i : i;
-                var index = offset + DisplayFrom;
+            // Bound to this page's real entries so a partial last page still renders in descending mode.
+            var visibleCount = VisibleCount(SearchResults.Length, DisplayFrom, MaxEntries);
 
-                if (index >= SearchResults.Length)
-                {
-                    break;
-                }
+            for (var i = 0; i < visibleCount; i++)
+            {
+                var offset = SortDescending ? visibleCount - 1 - i : i;
+                var index = offset + DisplayFrom;
 
                 var entry = SearchResults[index];
 
@@ -739,78 +750,103 @@ public class AdvancedSearchGump : Gump
             return;
         }
 
+        if (!TryBeginSearch())
+        {
+            from.SendMessage("A search is already running. Please wait for it to finish.");
+            return;
+        }
+
+        _threadId = 0;
+
         var autoSave = AutoSave.SavesEnabled;
-        if (autoSave)
+        AutoSave.SavesEnabled = false;
+
+        try
         {
-            AutoSave.SavesEnabled = false;
-        }
+            _threadWorkers ??= new AdvancedSearchThreadWorker[Math.Max(Environment.ProcessorCount - 1, 1)];
 
-        _threadWorkers ??= new AdvancedSearchThreadWorker[Math.Max(Environment.ProcessorCount - 1, 1)];
+            var ignoreQueue = new ConcurrentQueue<IEntity>();
+            var results = new ConcurrentQueue<AdvancedSearchResult>();
+            var worldLocation = new WorldLocation(from.Location, from.Map);
 
-        var ignoreQueue = new ConcurrentQueue<IEntity>();
-        var results = new ConcurrentQueue<AdvancedSearchResult>();
-        var worldLocation = new WorldLocation(from.Location, from.Map);
-
-        for (var i = 0; i < _threadWorkers.Length; i++)
-        {
-            (_threadWorkers[i] ??= new AdvancedSearchThreadWorker()).Wake(worldLocation, Filter, results, ignoreQueue);
-        }
-
-        var type = Filter.FilterType ? Filter.Type : null;
-
-        // Push the entities
-        foreach (var item in World.Items.Values)
-        {
-            if (type == null || type.IsInstanceOfType(item))
-            {
-                PushToWorkers(item);
-            }
-        }
-
-        foreach (var m in World.Mobiles.Values)
-        {
-            if (type == null || type.IsInstanceOfType(m))
-            {
-                PushToWorkers(m);
-            }
-        }
-
-        ThreadPool.QueueUserWorkItem(state =>
-        {
-            // Block until everything is processed
             for (var i = 0; i < _threadWorkers.Length; i++)
             {
-                _threadWorkers[i].Sleep();
+                (_threadWorkers[i] ??= new AdvancedSearchThreadWorker()).Wake(worldLocation, Filter, results, ignoreQueue);
             }
 
-            var ignoredEntities = new HashSet<IEntity>(ignoreQueue);
+            var type = Filter.FilterType ? Filter.Type : null;
 
-            // Force the GC to collect the ignored entities
-            ignoreQueue.Clear();
-
-            var resultsList = new List<AdvancedSearchResult>(results.Count);
-            foreach (var result in results)
+            // Push the entities. Workers read entity state concurrently with the main loop —
+            // see AdvancedSearchThreadWorker for the accepted, bounded race.
+            foreach (var item in World.Items.Values)
             {
-                if (!ignoredEntities.Contains(result.Entity))
+                if (type == null || type.IsInstanceOfType(item))
                 {
-                    resultsList.Add(result);
+                    PushToWorkers(item);
                 }
             }
 
-            SearchResults = resultsList.ToArray();
-
-            // Force the GC to collect the results
-            resultsList.Clear();
-            resultsList.TrimExcess();
-
-            // Send the gump on the main thread
-            Core.LoopContext.Post(
-                autoSaveState =>
+            foreach (var m in World.Mobiles.Values)
+            {
+                if (type == null || type.IsInstanceOfType(m))
                 {
-                    AutoSave.SavesEnabled = (bool)autoSaveState!;
-                    Resend(from);
-                }, state);
-        }, autoSave);
+                    PushToWorkers(m);
+                }
+            }
+
+            ThreadPool.QueueUserWorkItem(state =>
+            {
+                try
+                {
+                    // Block until everything is processed
+                    for (var i = 0; i < _threadWorkers.Length; i++)
+                    {
+                        _threadWorkers[i].Sleep();
+                    }
+
+                    var ignoredEntities = new HashSet<IEntity>(ignoreQueue);
+
+                    // Force the GC to collect the ignored entities
+                    ignoreQueue.Clear();
+
+                    var resultsList = new List<AdvancedSearchResult>(results.Count);
+                    foreach (var result in results)
+                    {
+                        if (!ignoredEntities.Contains(result.Entity))
+                        {
+                            resultsList.Add(result);
+                        }
+                    }
+
+                    SearchResults = resultsList.ToArray();
+
+                    // Force the GC to collect the results
+                    resultsList.Clear();
+                    resultsList.TrimExcess();
+
+                    // Send the gump on the main thread
+                    Core.LoopContext.Post(() => Resend(from));
+                }
+                catch (Exception ex)
+                {
+                    // A drain-phase throw here would terminate the process; the finally still
+                    // restores autosave and releases the guard.
+                    _logger.Warning(ex, "AdvancedSearch: search drain failed");
+                }
+                finally
+                {
+                    AutoSave.SavesEnabled = (bool)state!;
+                    EndSearch();
+                }
+            }, autoSave);
+        }
+        catch
+        {
+            // Setup failed before the work item took ownership of the release.
+            AutoSave.SavesEnabled = autoSave;
+            EndSearch();
+            throw;
+        }
     }
 
     private void SetSortSwitches(int radioSwitch)

Projects/UOContent/Engines/Advanced Search/AdvancedSearchThreadWorker.cs

@@ -3,13 +3,26 @@ using System.Collections.Concurrent;
 using System.Reflection;
 using System.Threading;
 using Server.Items;
+using Server.Logging;
 using Server.Mobiles;
 using Server.Multis;
 
 namespace Server.Engines.AdvancedSearch;
 
+/// <summary>
+/// Filters entities on a background thread while the main loop keeps mutating them — an
+/// intentional, bounded race. Reads of live <see cref="Item"/>/<see cref="Mobile"/> state are
+/// unsynchronized, so a torn <see cref="Point3D"/> read may report stale coordinates, and any
+/// getter that throws mid-read is caught per-entity in <see cref="DoEntitySearch"/> and skipped.
+/// Results are best-effort and may omit a concurrently modified entity, but never fault or corrupt
+/// server state. Eliminating the race would require snapshotting each read field onto the main
+/// thread before handing entities off; that is deferred.
+/// </summary>
 public class AdvancedSearchThreadWorker
 {
+    private static readonly ILogger _logger = LogFactory.GetLogger(typeof(AdvancedSearchThreadWorker));
+    private static readonly ConcurrentDictionary<Type, PropertyInfo[]> _propCache = new();
+
     private readonly Thread _thread;
     private readonly AutoResetEvent _startEvent; // Main thread tells the thread to start working
     private readonly AutoResetEvent _stopEvent; // Main thread waits for the worker finish draining
@@ -26,7 +39,10 @@ public class AdvancedSearchThreadWorker
         _startEvent = new AutoResetEvent(false);
         _stopEvent = new AutoResetEvent(false);
         _entities = new ConcurrentQueue<IEntity>();
-        _thread = new Thread(Execute);
+        _thread = new Thread(Execute)
+        {
+            IsBackground = true
+        };
         _thread.Start(this);
     }
 
@@ -52,10 +68,16 @@ public class AdvancedSearchThreadWorker
 
     public void Exit()
     {
-        _exit = true;
+        Volatile.Write(ref _exit, true);
 
         Wake(WorldLocation.Zero, null, null, null);
-        Sleep();
+
+        // Tolerate a worker that has already terminated (e.g. Core.Closing raced us) so
+        // shutdown can't deadlock waiting on a stopEvent that will never be set.
+        if (_thread.IsAlive)
+        {
+            Sleep();
+        }
     }
 
     public void Push(IEntity entity)
@@ -88,12 +110,17 @@ public class AdvancedSearchThreadWorker
                     worker._filter = null;
                     break;
                 }
+                else
+                {
+                    // Transiently empty but not yet paused: yield rather than busy-spin.
+                    Thread.Yield();
+                }
             }
 
             worker._stopEvent.Set(); // Allow the main thread to continue now that we are finished
-            worker._pause = false;
+            Volatile.Write(ref worker._pause, false);
 
-            if (Core.Closing || worker._exit)
+            if (Core.Closing || Volatile.Read(ref worker._exit))
             {
                 return;
             }
@@ -102,9 +129,28 @@ public class AdvancedSearchThreadWorker
 
     private AdvancedSearchResult DoEntitySearch(IEntity entity)
     {
-        if (_filter.HideValidInternalMap)
+        if (entity == null || entity.Deleted)
         {
-            HandleValidInternal(entity);
+            return null;
+        }
+
+        try
+        {
+            return DoEntitySearchCore(entity);
+        }
+        catch (Exception ex)
+        {
+            _logger.Warning(ex, "AdvancedSearch: filter threw for {Entity}; skipping", entity);
+            return null;
+        }
+    }
+
+    private AdvancedSearchResult DoEntitySearchCore(IEntity entity)
+    {
+        if (_filter == null)
+        {
+            // Exit() clears the filter; a straggler entity dequeued after teardown bails here.
+            return null;
         }
 
         // Check for valid map
@@ -138,6 +184,12 @@ public class AdvancedSearchThreadWorker
             return null;
         }
 
+        // After the cheap filters, so non-qualifying entities skip the house/keyring enumeration.
+        if (_filter.HideValidInternalMap)
+        {
+            HandleValidInternal(entity);
+        }
+
         if (entity is Mobile mobile)
         {
             return DoMobileSearch(mobile);
@@ -296,27 +348,17 @@ public class AdvancedSearchThreadWorker
         }
     }
 
-    private static bool EvaluateRecursive(IEntity entity, ReadOnlySpan<char> span)
-    {
-        var atIndex = span.IndexOf('@');
-        var orIndex = span.IndexOf('|');
-
-        if (atIndex == -1 && orIndex == -1)
-        {
-            return EvaluateSingleExpression(entity, span);
-        }
-
-        var result = atIndex != -1;
-        var splitIndex = result ? atIndex : orIndex;
-
-        var left = EvaluateRecursive(entity, span.Slice(0, splitIndex));
-        var right = EvaluateRecursive(entity, span.Slice(splitIndex + 1));
-
-        return result ? left && right : left || right;
-    }
+    private static bool EvaluateRecursive(IEntity entity, ReadOnlySpan<char> span) =>
+        AdvancedSearchUtilities.EvaluateBoolean(span, entity, static (e, leaf) => EvaluateSingleExpression(e, leaf));
 
     private static bool EvaluateSingleExpression(IEntity entity, ReadOnlySpan<char> expression)
     {
+        expression = expression.Trim();
+        if (expression.Length == 0)
+        {
+            return false;
+        }
+
         var negate = false;
         if (expression[0] == '~')
         {
@@ -338,7 +380,7 @@ public class AdvancedSearchThreadWorker
             return false;
         }
 
-        var properties = entity.GetType().GetProperties();
+        var properties = _propCache.GetOrAdd(entity.GetType(), static t => t.GetProperties());
         PropertyInfo property = null;
         for (var i = 0; i < properties.Length; ++i)
         {

Projects/UOContent/Engines/Advanced Search/AdvancedSearchUtilities.cs

@@ -43,77 +43,80 @@ public static class AdvancedSearchUtilities
 
         if (propertyType == typeof(long))
         {
-            var parsedValue = ParseValue<long>(valuePart);
-            return CompareNumeric((long)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<long>(valuePart, out var parsedValue) &&
+                   CompareNumeric((long)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(ulong))
         {
-            var parsedValue = ParseValue<ulong>(valuePart);
-            return CompareNumeric((ulong)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<ulong>(valuePart, out var parsedValue) &&
+                   CompareNumeric((ulong)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(int))
         {
-            var parsedValue = ParseValue<int>(valuePart);
-            return CompareNumeric((int)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<int>(valuePart, out var parsedValue) &&
+                   CompareNumeric((int)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(uint))
         {
-            var parsedValue = ParseValue<uint>(valuePart);
-            return CompareNumeric((uint)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<uint>(valuePart, out var parsedValue) &&
+                   CompareNumeric((uint)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(short))
         {
-            var parsedValue = ParseValue<short>(valuePart);
-            return CompareNumeric((short)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<short>(valuePart, out var parsedValue) &&
+                   CompareNumeric((short)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(ushort))
         {
-            var parsedValue = ParseValue<ushort>(valuePart);
-            return CompareNumeric((ushort)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<ushort>(valuePart, out var parsedValue) &&
+                   CompareNumeric((ushort)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(sbyte))
         {
-            var parsedValue = ParseValue<sbyte>(valuePart);
-            return CompareNumeric((sbyte)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<sbyte>(valuePart, out var parsedValue) &&
+                   CompareNumeric((sbyte)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(byte))
         {
-            var parsedValue = ParseValue<byte>(valuePart);
-            return CompareNumeric((byte)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<byte>(valuePart, out var parsedValue) &&
+                   CompareNumeric((byte)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(float))
         {
-            var parsedValue = ParseValue<float>(valuePart);
-            return Compare((float)propertyValue!, parsedValue, valuePart, operatorSpan);
+            return TryParseValue<float>(valuePart, out var parsedValue) &&
+                   Compare((float)propertyValue!, parsedValue, valuePart, operatorSpan);
         }
         if (propertyType == typeof(double))
         {
-            var parsedValue = ParseValue<double>(valuePart);
-            return Compare((double)propertyValue!, parsedValue, valuePart, operatorSpan);
+            return TryParseValue<double>(valuePart, out var parsedValue) &&
+                   Compare((double)propertyValue!, parsedValue, valuePart, operatorSpan);
         }
         if (propertyType == typeof(string))
         {
-            var parsedValue = ParseValue<string>(valuePart);
-            return Compare((string)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<string>(valuePart, out var parsedValue) &&
+                   Compare((string)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(TimeSpan))
         {
-            var parsedValue = ParseValue<TimeSpan>(valuePart);
-            return Compare((TimeSpan)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<TimeSpan>(valuePart, out var parsedValue) &&
+                   Compare((TimeSpan)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(DateTime))
         {
-            var parsedValue = ParseValue<DateTime>(valuePart);
-            return Compare((DateTime)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<DateTime>(valuePart, out var parsedValue) &&
+                   Compare((DateTime)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType == typeof(bool))
         {
-            var parsedValue = ParseValue<bool>(valuePart);
-            return Compare((bool)propertyValue!, parsedValue, operatorSpan);
+            return TryParseValue<bool>(valuePart, out var parsedValue) &&
+                   Compare((bool)propertyValue!, parsedValue, operatorSpan);
         }
         if (propertyType.IsEnum)
         {
-            var valueEnum = Enum.Parse(propertyType, valuePart, false);
+            if (!Enum.TryParse(propertyType, valuePart.ToString(), true, out var valueEnum) || valueEnum == null)
+            {
+                return false;
+            }
 
             return GetEnumSize(propertyType) switch
             {
@@ -121,15 +124,17 @@ public static class AdvancedSearchUtilities
                 2 => CompareNumeric((short)propertyValue!, (short)valueEnum, operatorSpan),
                 4 => CompareNumeric((int)propertyValue!, (int)valueEnum, operatorSpan),
                 8 => CompareNumeric((long)propertyValue!, (long)valueEnum, operatorSpan),
+                _ => false
             };
         }
-        if (!propertyType.IsValueType)
-        {
-            var parsedValue = ParseValue<object>(valuePart);
-            return CompareReference(propertyValue!, parsedValue, operatorSpan);
-        }
-
-        return false;
+        // Anything the hot typed paths above didn't handle — reference types (Poison, Map, entity
+        // properties resolved by serial), IParsable value types (Guid, decimal, ...), and legacy
+        // RunUO types with a static Parse(string) (Faction, Town, ...). Delegate to the shared,
+        // thread-safe Types converter so the target is parsed into the property's real type, then
+        // compare by value. A string is allocated here, but this is the uncommon path; the common
+        // types never reach it. Types returns a non-null message when it can't parse -> no match.
+        return Types.TryParse(propertyType, valuePart.ToString(), out var parsed) == null &&
+               CompareReference(propertyValue!, parsed, operatorSpan);
     }
 
     public static bool CompareNumeric<T>(T propertyValue, T parsedValue, ReadOnlySpan<char> operatorSpan) where T : INumber<T> =>
@@ -236,19 +241,40 @@ public static class AdvancedSearchUtilities
             _           => false
         };
 
-    public static bool CompareReference<T>(T propertyValue, T parsedValue, ReadOnlySpan<char> operatorSpan) =>
-        operatorSpan switch
+    public static bool CompareReference<T>(T propertyValue, T parsedValue, ReadOnlySpan<char> operatorSpan)
+    {
+        switch (operatorSpan)
         {
-            "=" or "==" => propertyValue.Equals(parsedValue),
-            "!" or "!=" => !propertyValue.Equals(parsedValue),
-            ">"         => Comparer<T>.Default.Compare(propertyValue, parsedValue) > 0,
-            "<"         => Comparer<T>.Default.Compare(propertyValue, parsedValue) < 0,
-            ">="        => Comparer<T>.Default.Compare(propertyValue, parsedValue) >= 0,
-            "<="        => Comparer<T>.Default.Compare(propertyValue, parsedValue) <= 0,
-            _           => false
-        };
+            case "=":
+            case "==": return Equals(propertyValue, parsedValue);
+            case "!":
+            case "!=": return !Equals(propertyValue, parsedValue);
+        }
 
-    public static T ParseValue<T>(ReadOnlySpan<char> valuePart)
+        if (propertyValue is IComparable cmp && parsedValue != null)
+        {
+            try
+            {
+                var c = cmp.CompareTo(parsedValue);
+                return operatorSpan switch
+                {
+                    ">"  => c > 0,
+                    "<"  => c < 0,
+                    ">=" => c >= 0,
+                    "<=" => c <= 0,
+                    _    => false
+                };
+            }
+            catch
+            {
+                return false;
+            }
+        }
+
+        return false;
+    }
+
+    internal static bool TryParseValue<T>(ReadOnlySpan<char> valuePart, out T value)
     {
         // Special handling for boolean and hexadecimal values
         if (typeof(T) == typeof(bool))
@@ -256,74 +282,149 @@ public static class AdvancedSearchUtilities
             var val = valuePart.ToString().ToLower();
             if (val is "true" or "1" or "enabled" or "on")
             {
-                return (T)(object)true;
+                value = (T)(object)true;
+                return true;
             }
 
             if (val is "false" or "0" or "disabled" or "off")
             {
-                return (T)(object)false;
+                value = (T)(object)false;
+                return true;
             }
+
+            value = default;
+            return false;
         }
 
         if (typeof(T) == typeof(long))
         {
-            return ParseNumericValue<long, T>(valuePart);
+            return TryParseNumericValue<long, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(ulong))
         {
-            return ParseNumericValue<ulong, T>(valuePart);
+            return TryParseNumericValue<ulong, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(int))
         {
-            return ParseNumericValue<int, T>(valuePart);
+            return TryParseNumericValue<int, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(uint))
         {
-            return ParseNumericValue<uint, T>(valuePart);
+            return TryParseNumericValue<uint, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(short))
         {
-            return ParseNumericValue<short, T>(valuePart);
+            return TryParseNumericValue<short, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(ushort))
         {
-            return ParseNumericValue<ushort, T>(valuePart);
+            return TryParseNumericValue<ushort, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(sbyte))
         {
-            return ParseNumericValue<sbyte, T>(valuePart);
+            return TryParseNumericValue<sbyte, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(byte))
         {
-            return ParseNumericValue<byte, T>(valuePart);
+            return TryParseNumericValue<byte, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(float))
         {
-            return ParseNumericValue<float, T>(valuePart);
+            return TryParseNumericValue<float, T>(valuePart, out value);
         }
 
         if (typeof(T) == typeof(double))
         {
-            return ParseNumericValue<double, T>(valuePart);
+            return TryParseNumericValue<double, T>(valuePart, out value);
         }
 
-        // Default parsing for other types
-        return (T)Convert.ChangeType(valuePart.ToString(), typeof(T));
+        // string needs no parsing — the span itself is the value.
+        if (typeof(T) == typeof(string))
+        {
+            value = (T)(object)valuePart.ToString();
+            return true;
+        }
+
+        // Remaining supported types (TimeSpan, DateTime) parse straight from the span via
+        // ISpanParsable<T> — no allocation, no reflection, and unlike Convert.ChangeType it handles
+        // TimeSpan, which is not IConvertible and previously failed silently.
+        if (typeof(T) == typeof(TimeSpan))
+        {
+            return TryParseSpanParsable<TimeSpan, T>(valuePart, out value);
+        }
+
+        if (typeof(T) == typeof(DateTime))
+        {
+            return TryParseSpanParsable<DateTime, T>(valuePart, out value);
+        }
+
+        value = default;
+        return false;
+    }
+
+    // Parses U (a value type exposing ISpanParsable<U>) from the span and reinterprets it as T. The
+    // two type params mirror TryParseNumericValue: the caller dispatches on typeof(T), so U == T at
+    // every call site and the (T)(object) cast is always valid.
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static bool TryParseSpanParsable<U, T>(ReadOnlySpan<char> valuePart, out T value) where U : ISpanParsable<U>
+    {
+        if (U.TryParse(valuePart, null, out var parsed))
+        {
+            value = (T)(object)parsed;
+            return true;
+        }
+
+        value = default;
+        return false;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static R ParseNumericValue<T, R>(ReadOnlySpan<char> valuePart) where T : INumber<T> =>
-        valuePart.StartsWith("0x")
-            ? (R)(object)T.Parse(valuePart[2..], NumberStyles.HexNumber, null)
-            : (R)(object)T.Parse(valuePart, null);
+    private static bool TryParseNumericValue<T, R>(ReadOnlySpan<char> valuePart, out R value) where T : INumber<T>
+    {
+        var ok = valuePart.StartsWith("0x")
+            ? T.TryParse(valuePart[2..], NumberStyles.HexNumber, null, out var parsed)
+            : T.TryParse(valuePart, null, out parsed);
+
+        if (ok)
+        {
+            value = (R)(object)parsed;
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+
+    // Evaluates one trimmed leaf atom against caller-supplied state. A custom delegate is required
+    // because ReadOnlySpan<char> cannot be a Func<> type argument; passing state avoids a per-call
+    // capturing closure, so the recursion allocates neither a string nor a closure.
+    internal delegate bool LeafEvaluator<in TState>(TState state, ReadOnlySpan<char> leaf);
+
+    // OR ('|') binds looser than AND ('@'); split on the outermost OR first, then AND.
+    internal static bool EvaluateBoolean<TState>(ReadOnlySpan<char> expr, TState state, LeafEvaluator<TState> evalLeaf)
+    {
+        var orIndex = expr.IndexOf('|');
+        if (orIndex != -1)
+        {
+            return EvaluateBoolean(expr[..orIndex], state, evalLeaf) || EvaluateBoolean(expr[(orIndex + 1)..], state, evalLeaf);
+        }
+
+        var andIndex = expr.IndexOf('@');
+        if (andIndex != -1)
+        {
+            return EvaluateBoolean(expr[..andIndex], state, evalLeaf) && EvaluateBoolean(expr[(andIndex + 1)..], state, evalLeaf);
+        }
+
+        return evalLeaf(state, expr.Trim());
+    }
 
     private static int GetEnumSize(Type enumType) =>
         Type.GetTypeCode(Enum.GetUnderlyingType(enumType)) switch

Projects/UOContent/Engines/Factions/Core/Faction.cs

@@ -16,7 +16,7 @@ using Server.Targeting;
 namespace Server.Factions;
 
 [CustomEnum(["Minax", "Council of Mages", "True Britannians", "Shadowlords"])]
-public abstract class Faction : IComparable<Faction>
+public abstract class Faction : IComparable<Faction>, ISpanParsable<Faction>
 {
     public const int StabilityFactor = 300;     // 300% greater (3 times) than smallest faction
     public const int StabilityActivation = 200; // Stability code goes into effect when largest faction has > 200 people
@@ -1313,7 +1313,27 @@ public abstract class Faction : IComparable<Faction>
         return null;
     }
 
-    public static Faction Parse(string name)
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Faction Parse(string s) => Parse(s, null);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Faction Parse(string s, IFormatProvider provider) => Parse(s.AsSpan(), provider);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse(string s, IFormatProvider provider, out Faction result) =>
+        TryParse(s.AsSpan(), provider, out result);
+
+    public static Faction Parse(ReadOnlySpan<char> s, IFormatProvider provider)
+    {
+        if (TryParse(s, provider, out var result))
+        {
+            return result;
+        }
+
+        throw new FormatException($"The input string '{s}' was not in a correct format.");
+    }
+
+    public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider provider, out Faction result)
     {
         var factions = Factions;
 
@@ -1321,13 +1341,15 @@ public abstract class Faction : IComparable<Faction>
         {
             var faction = factions[i];
 
-            if (faction.Definition.FriendlyName.InsensitiveEquals(name))
+            if (s.InsensitiveEquals(faction.Definition.FriendlyName))
             {
-                return faction;
+                result = faction;
+                return true;
             }
         }
 
-        return null;
+        result = null;
+        return false;
     }
 
     public static bool InSkillLoss(Mobile mob) => m_SkillLoss.ContainsKey(mob);

Projects/UOContent/Engines/Factions/Core/Town.cs

@@ -1,11 +1,12 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using Server.Targeting;
 
 namespace Server.Factions;
 
 [CustomEnum(["Britain", "Magincia", "Minoc", "Moonglow", "Skara Brae", "Trinsic", "Vesper", "Yew"])]
-public abstract class Town : IComparable<Town>
+public abstract class Town : IComparable<Town>, ISpanParsable<Town>
 {
     public const int SilverCaptureBonus = 10000;
 
@@ -482,7 +483,27 @@ public abstract class Town : IComparable<Town>
         return null;
     }
 
-    public static Town Parse(string name)
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Town Parse(string s) => Parse(s, null);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Town Parse(string s, IFormatProvider provider) => Parse(s.AsSpan(), provider);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse(string s, IFormatProvider provider, out Town result) =>
+        TryParse(s.AsSpan(), provider, out result);
+
+    public static Town Parse(ReadOnlySpan<char> s, IFormatProvider provider)
+    {
+        if (TryParse(s, provider, out var result))
+        {
+            return result;
+        }
+
+        throw new FormatException($"The input string '{s}' was not in a correct format.");
+    }
+
+    public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider provider, out Town result)
     {
         var towns = Towns;
 
@@ -490,13 +511,15 @@ public abstract class Town : IComparable<Town>
         {
             var town = towns[i];
 
-            if (town.Definition.FriendlyName.InsensitiveEquals(name))
+            if (s.InsensitiveEquals(town.Definition.FriendlyName))
             {
-                return town;
+                result = town;
+                return true;
             }
         }
 
-        return null;
+        result = null;
+        return false;
     }
 
     [Usage("GrantTownSilver <amount>")]

Projects/UOContent/Utilities/Types.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Reflection;
@@ -10,7 +11,8 @@ namespace Server
     {
         public static readonly Type[] ParseStringParamTypes = { typeof(string), typeof(IFormatProvider) };
         public static readonly Type[] ParseStringNumericParamTypes = { typeof(string), typeof(NumberStyles) };
-        private static object[] _parseParams = { null, null };
+        // Legacy RunUO signature: a static Parse(string) that predates IParsable<T> (e.g. Faction, Town).
+        public static readonly Type[] ParseStringSingleParamTypes = { typeof(string) };
 
         public static readonly Type OfByte = typeof(byte);
         public static readonly Type OfSByte = typeof(sbyte);
@@ -75,7 +77,9 @@ namespace Server
             OfULong
         };
 
-        private static Dictionary<Type, bool> _isParsable;
+        // Thread-safe: parse metadata is read from parallel callers (e.g. the Advanced Search workers),
+        // not just the single-threaded command path.
+        private static readonly ConcurrentDictionary<Type, bool> _isParsable = new();
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsType(Type type, Type check) => check.IsAssignableFrom(type);
@@ -89,25 +93,19 @@ namespace Server
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsText(Type t) => IsType(t, OfText);
 
-        public static bool IsParsable(Type t)
-        {
-            _isParsable ??= new();
-            if (_isParsable.TryGetValue(t, out var isParsable))
+        public static bool IsParsable(Type t) =>
+            _isParsable.GetOrAdd(t, static type =>
             {
-                return isParsable;
-            }
-
-            foreach (var x in t.GetInterfaces())
-            {
-                if (x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IParsable<>))
+                foreach (var x in type.GetInterfaces())
                 {
-                    isParsable = true;
-                    break;
+                    if (x.IsGenericType && x.GetGenericTypeDefinition() == typeof(IParsable<>))
+                    {
+                        return true;
+                    }
                 }
-            }
 
-            return _isParsable[t] = isParsable;
-        }
+                return false;
+            });
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsDecimal(Type t) => Array.IndexOf(DecimalTypes, t) >= 0;
@@ -118,18 +116,81 @@ namespace Server
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static bool IsEntity(Type t) => OfEntity.IsAssignableFrom(t);
 
-        private static Dictionary<Type, MethodInfo> _parseMethods;
+        private static readonly ConcurrentDictionary<Type, MethodInfo> _parseMethods = new();
+
+        // A static string Parse method: the modern IParsable<T> Parse(string, IFormatProvider), or a
+        // legacy RunUO Parse(string). Cached per type; null if the type has neither. (Span-based Parse
+        // can't be reflection-invoked — a ReadOnlySpan can't be boxed into the args array — so the
+        // string overloads are what we bind to.)
+        public static MethodInfo GetParseMethod(Type t) =>
+            _parseMethods.GetOrAdd(
+                t,
+                static type => type.GetMethod("Parse", ParseStringParamTypes)
+                               ?? type.GetMethod("Parse", ParseStringSingleParamTypes)
+            );
 
         public static object Parse(Type t, string value)
         {
-            _parseMethods ??= new();
-            if (!_parseMethods.TryGetValue(t, out var method))
+            var method = GetParseMethod(t);
+            if (method == null)
             {
-                _parseMethods[t] = method = t.GetMethod("Parse", ParseStringParamTypes);
+                return null;
             }
 
-            _parseParams[0] = value;
-            return method?.Invoke(null, _parseParams);
+            // Fresh args array per call — a shared static array would race across concurrent callers.
+            // Arg shape depends on which overload we bound to (IParsable 2-arg vs legacy 1-arg).
+            var args = method.GetParameters().Length == 2 ? new object[] { value, null } : new object[] { value };
+            return method.Invoke(null, args);
+        }
+
+        // Parses directly into the concrete numeric type via INumber<T>.TryParse (the Type-dispatched
+        // equivalent of a generic TryParse<T>). Returns the boxed value; false if the text doesn't fit
+        // the type's range/format so the caller can fall through.
+        private static bool TryParseNumeric(Type type, ReadOnlySpan<char> span, NumberStyles style, out object result)
+        {
+            if (type == OfInt && int.TryParse(span, style, null, out var i))
+            {
+                result = i;
+                return true;
+            }
+            if (type == OfUInt && uint.TryParse(span, style, null, out var ui))
+            {
+                result = ui;
+                return true;
+            }
+            if (type == OfLong && long.TryParse(span, style, null, out var l))
+            {
+                result = l;
+                return true;
+            }
+            if (type == OfULong && ulong.TryParse(span, style, null, out var ul))
+            {
+                result = ul;
+                return true;
+            }
+            if (type == OfShort && short.TryParse(span, style, null, out var s))
+            {
+                result = s;
+                return true;
+            }
+            if (type == OfUShort && ushort.TryParse(span, style, null, out var us))
+            {
+                result = us;
+                return true;
+            }
+            if (type == OfByte && byte.TryParse(span, style, null, out var b))
+            {
+                result = b;
+                return true;
+            }
+            if (type == OfSByte && sbyte.TryParse(span, style, null, out var sb))
+            {
+                result = sb;
+                return true;
+            }
+
+            result = null;
+            return false;
         }
 
         // Do not use this in "Parse" methods, it may cause a stack overflow
@@ -201,35 +262,38 @@ namespace Server
 
             if (IsNumeric(type))
             {
-                try
+                var span = value.AsSpan();
+                var style = NumberStyles.Integer;
+                if (span.StartsWithOrdinal("0x"))
                 {
-                    var isHex = value.StartsWithOrdinal("0x");
-                    var index = isHex ? 2 : 0;
-                    if (ulong.TryParse(value.AsSpan(index), isHex ? NumberStyles.HexNumber : NumberStyles.Integer, null, out var num))
-                    {
-                        if (isEntity)
-                        {
-                            constructed = World.FindEntity((Serial)num);
-                        }
-                        else if (isSerial)
-                        {
-                            constructed = (Serial)num;
-                        }
-                        else
-                        {
-                            constructed = Convert.ChangeType(num, type);
-                        }
+                    span = span[2..];
+                    style = NumberStyles.HexNumber;
+                }
 
+                if (isEntity || isSerial)
+                {
+                    // Serial/entity properties were mutated to int above; a Serial is a uint, so parse
+                    // the full 32-bit range as ulong and resolve.
+                    if (ulong.TryParse(span, style, null, out var num))
+                    {
+                        constructed = isEntity ? World.FindEntity((Serial)num) : (Serial)num;
                         return null;
                     }
                 }
-                catch
+                else if (TryParseNumeric(type, span, style, out constructed))
                 {
-                    return "That is not properly formatted.";
+                    // Parse the string directly into the target type via INumber<T>.TryParse — no
+                    // Convert.ChangeType, and (unlike parse-as-ulong) signed and per-type ranges are honored.
+                    return null;
                 }
+
+                // On parse failure, fall through to the Parse-method / Convert.ChangeType fallbacks below.
             }
 
-            if (IsParsable(type))
+            // IParsable<T> (Parse(string, IFormatProvider)) or a legacy RunUO Parse(string). Gating on
+            // the discovered method rather than the IParsable interface keeps pre-IParsable types
+            // (Faction, Town, ...) parseable for backwards compatibility.
+            if (GetParseMethod(type) != null)
             {
                 try
                 {

dev-docs/runuo-migration-docs/01-foundation-changes.md

@@ -282,6 +282,65 @@ public MyItem(Serial serial) : base(serial) { }
 // ModernUO — DELETE THIS CONSTRUCTOR. The source generator creates it.
 ```
 
+## 15. Static `Parse(string)` → `IParsable<T>` / `ISpanParsable<T>`
+
+RunUO predates `IParsable<T>`/`ISpanParsable<T>` (C# 11 / .NET 7 static-abstract interface
+members), so RunUO types that convert from a string expose a bare `public static T Parse(string value)`.
+**ModernUO expects any such type to implement `IParsable<T>` (string) and, where practical,
+`ISpanParsable<T>` (span; it extends `IParsable<T>`, so implement span and you get both).**
+
+This matters because the engine's string→value converter, `Server.Types.TryParse` — used by `[set`,
+`[props`, spawner property assignment, the conditional-command compiler (`[where`), and Advanced
+Search — binds to the `Parse(string, IFormatProvider)` signature. A type with **only** a legacy
+`Parse(string)` is discovered by `Types` through a reflection fallback, but that fallback is a safety
+net, not the intended path: a bare `Parse(string)` is easy to miss, doesn't participate in the
+span-based fast paths, and (if it returns `null` instead of throwing) makes `[set` silently assign
+`null` on bad input. Convert it.
+
+The `Parse` overloads throw `FormatException` on failure; `TryParse` returns `false`. Delegate the
+string overloads to a span core (see `Race`, `Poison`, `Point3D` for the established pattern):
+
+```csharp
+// RunUO
+public abstract class Faction : IComparable<Faction>
+{
+    public static Faction Parse(string name)  // returns null on no-match — wrong contract, not IParsable
+    {
+        // ... linear search by name ...
+        return null;
+    }
+}
+
+// ModernUO
+public abstract class Faction : IComparable<Faction>, ISpanParsable<Faction>
+{
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Faction Parse(string s) => Parse(s, null);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Faction Parse(string s, IFormatProvider provider) => Parse(s.AsSpan(), provider);
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse(string s, IFormatProvider provider, out Faction result) =>
+        TryParse(s.AsSpan(), provider, out result);
+
+    public static Faction Parse(ReadOnlySpan<char> s, IFormatProvider provider) =>
+        TryParse(s, provider, out var result)
+            ? result
+            : throw new FormatException($"The input string '{s}' was not in a correct format.");
+
+    public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider provider, out Faction result)
+    {
+        // ... linear search by name using s.InsensitiveEquals(...) ...
+        result = null;
+        return false;
+    }
+}
+```
+
+To find un-migrated types: search for `public static [A-Za-z0-9_<>]+ Parse\(string ` and check whether
+the declaring type lists `IParsable<T>`/`ISpanParsable<T>`.
+
 ## Quick Checklist
 
 When migrating any RunUO script, apply these changes in order:
@@ -300,6 +359,7 @@ When migrating any RunUO script, apply these changes in order:
 12. [ ] Modernize property syntax
 13. [ ] Remove `Serial` constructor (handled by serialization generator)
 14. [ ] Update usings
+15. [ ] Convert bare static `Parse(string)` to `IParsable<T>`/`ISpanParsable<T>`
 
 ## See Also