diff --git a/src/Predictalytics.Application.Tests/Services/MarketRepositoryTests.cs b/src/Predictalytics.Application.Tests/Services/MarketRepositoryTests.cs
index 5fc434c..783ec2a 100644
--- a/src/Predictalytics.Application.Tests/Services/MarketRepositoryTests.cs
+++ b/src/Predictalytics.Application.Tests/Services/MarketRepositoryTests.cs
@@ -90,4 +90,67 @@ public class MarketRepositoryTests
             Assert.Equal("Elections", market.Subcategory);
         }
     }
+
+    /// <summary>
+    /// Regression (2026-08-04): only Slug and Title were capped on the event upsert,
+    /// so a Polymarket event with an over-long Description made MySQL reject the whole
+    /// batch with "Data too long for column 'Description'" — aborting the entire market
+    /// sync, not just that one event. Every length-constrained Event field must be capped.
+    ///
+    /// SQLite ignores varchar limits, so asserting "no exception" would prove nothing:
+    /// the assertions check the stored lengths instead.
+    /// </summary>
+    [Theory]
+    [InlineData(true)]  // event already exists → update branch
+    [InlineData(false)] // new event → insert branch
+    public async Task AddOrUpdateEventsAsync_CapsAllLengthConstrainedFields(bool eventAlreadyExists)
+    {
+        using var connection = new SqliteConnection("DataSource=:memory:");
+        connection.Open();
+        var options = new DbContextOptionsBuilder<AppDbContext>()
+            .UseSqlite(connection)
+            .Options;
+
+        using (var setup = new AppDbContext(options))
+        {
+            setup.Database.EnsureCreated();
+            if (eventAlreadyExists)
+            {
+                setup.Set<Event>().Add(new Event
+                {
+                    Id = 1, Platform = PlatformType.Polymarket, PlatformEventId = 99L,
+                    Slug = "existing", Title = "Existing", Description = "short"
+                });
+                setup.SaveChanges();
+            }
+        }
+
+        using (var ctx = new AppDbContext(options))
+        {
+            var repo = new MarketRepository(ctx);
+            await repo.AddOrUpdateEventsAsync(new[]
+            {
+                new Event
+                {
+                    Platform = PlatformType.Polymarket,
+                    PlatformEventId = 99L,
+                    Slug = new string('s', 900),
+                    Title = new string('t', 1500),
+                    Description = new string('d', 6000),
+                    ImageUrl = "https://x/" + new string('i', 2000),
+                    Tags = new string('g', 2000)
+                }
+            });
+        }
+
+        using (var assertCtx = new AppDbContext(options))
+        {
+            var stored = await assertCtx.Set<Event>().SingleAsync(e => e.PlatformEventId == 99L);
+            Assert.Equal(512, stored.Slug.Length);
+            Assert.Equal(1024, stored.Title.Length);
+            Assert.Equal(4096, stored.Description!.Length);
+            Assert.Equal(1024, stored.ImageUrl!.Length);
+            Assert.Equal(1024, stored.Tags.Length);
+        }
+    }
 }
diff --git a/src/Predictalytics.Infrastructure/Data/Repositories/MarketRepository.cs b/src/Predictalytics.Infrastructure/Data/Repositories/MarketRepository.cs
index bd46b22..e130545 100644
--- a/src/Predictalytics.Infrastructure/Data/Repositories/MarketRepository.cs
+++ b/src/Predictalytics.Infrastructure/Data/Repositories/MarketRepository.cs
@@ -136,8 +136,7 @@ public class MarketRepository : IMarketRepository
 
                 foreach (var ev in currentBatch)
                 {
-                    if (ev.Slug != null && ev.Slug.Length > 512) ev.Slug = ev.Slug[..512];
-                    if (ev.Title != null && ev.Title.Length > 1024) ev.Title = ev.Title[..1024];
+                    TruncateEventStrings(ev);
 
                     if (existingEventsMap.TryGetValue(ev.PlatformEventId, out var existing))
                     {
@@ -231,6 +230,22 @@ public class MarketRepository : IMarketRepository
         }
     }
 
+    /// <summary>
+    /// Caps every length-constrained Event string to its column width.
+    /// Must cover ALL such fields: MySQL rejects the whole batch with
+    /// "Data too long for column ..." if a single one overflows, so one long
+    /// description aborts the entire market sync — not just that one event.
+    /// Keep in sync with the HasMaxLength calls in AppDbContext.
+    /// </summary>
+    private void TruncateEventStrings(Event ev)
+    {
+        ev.Slug = StringHelper.Truncate(ev.Slug, 512) ?? "";
+        ev.Title = StringHelper.Truncate(ev.Title, 1024) ?? "";
+        ev.Description = StringHelper.Truncate(ev.Description, 4096);
+        ev.ImageUrl = StringHelper.Truncate(ev.ImageUrl, 1024);
+        ev.Tags = StringHelper.Truncate(ev.Tags, 1024) ?? "";
+    }
+
     private void TruncateMarketStrings(Market market)
     {
         market.Question = StringHelper.Truncate(market.Question, 1024) ?? "";