JoshHeaps.Net/Services/Implementations/ChessEngineFactory.cs

@@ -19,6 +19,16 @@ public sealed class ChessEngineOptions
     public const string SectionName = "ChessEngine";
 
     public ChessEngineKind Engine { get; set; } = ChessEngineKind.Stockfish;
+
+    /// <summary>
+    /// Absolute path to the learned-weights file. Leave null to default to
+    /// <c>{ContentRoot}/chess-data/learned-weights.txt</c> (fine for local dev). In
+    /// production set this to a stable, service-writable location OUTSIDE the deploy
+    /// directory (e.g. <c>/var/lib/joshheaps/chess-data/learned-weights.txt</c>) so the
+    /// trained weights survive deploys and avoid deploy-user vs service-user permission
+    /// clashes. Override via the <c>ChessEngine__WeightsPath</c> environment variable.
+    /// </summary>
+    public string? WeightsPath { get; set; }
 }
 
 /// <summary>Creates the configured <see cref="IChessEngine"/> per game.</summary>

JoshHeaps.Net/Services/Implementations/LearnedWeightsStore.cs

@@ -1,5 +1,6 @@
 using JoshHeaps.Net.Models;
 using JoshHeaps.Net.Services.Interfaces;
+using Microsoft.Extensions.Options;
 
 namespace JoshHeaps.Net.Services.Implementations;
 
@@ -16,12 +17,31 @@ public sealed class LearnedWeightsStore : ILearnedWeightsStore
 
     public string WeightsFilePath { get; }
 
-    public LearnedWeightsStore(IHostEnvironment env)
+    public LearnedWeightsStore(IHostEnvironment env, IOptions<ChessEngineOptions> options, ILogger<LearnedWeightsStore> logger)
+    {
+        // Prefer the configured path (production points this outside the deploy dir); fall
+        // back to the content root for local dev.
+        var configured = options.Value.WeightsPath;
+        WeightsFilePath = string.IsNullOrWhiteSpace(configured)
+            ? Path.Combine(env.ContentRootPath, "chess-data", "learned-weights.txt")
+            : configured;
+
+        // A missing/unwritable/misconfigured path must not take down the whole app — the
+        // learned engine just plays from a neutral table and can't persist training.
+        try
         {
-        WeightsFilePath = Path.Combine(env.ContentRootPath, "chess-data", "learned-weights.txt");
             Directory.CreateDirectory(Path.GetDirectoryName(WeightsFilePath)!);
             CustomChessEngine.NativeMethods.learned_load(WeightsFilePath);
         }
+        catch (Exception ex)
+        {
+            logger.LogError(ex,
+                "Could not initialize the learned-weights store at {Path}. The learned engine will " +
+                "play from a neutral table and training will not persist. In production set " +
+                "ChessEngine:WeightsPath (env ChessEngine__WeightsPath) to a service-writable directory.",
+                WeightsFilePath);
+        }
+    }
 
     public nint CreateTrainer() => CustomChessEngine.NativeMethods.trainer_create();