mgravell · Sep 14, 2026 · Sep 14, 2026 · Sep 14, 2026 · Oct 5, 2026 · Oct 15, 2026
diff --git a/src/NRedisStack/CountMinSketch/CmsCommandBuilder.cs b/src/NRedisStack/CountMinSketch/CmsCommandBuilder.cs
@@ -32,14 +32,31 @@ public static SerializedCommand Info(RedisKey key)
         return info;
     }
 
-    public static SerializedCommand InitByDim(RedisKey key, long width, long depth)
+    public static SerializedCommand InitByDim(RedisKey key, long width, long depth, int? cellSize = null)
     {
-        return new(CommandCategories.WriteAccumulating, CMS.INITBYDIM, key, width, depth);
+        List<object> args = [key, width, depth];
+        AddCellSize(args, cellSize);
+
+        return new(CommandCategories.WriteAccumulating, CMS.INITBYDIM, args);
     }
 
-    public static SerializedCommand InitByProb(RedisKey key, double error, double probability)
+    public static SerializedCommand InitByProb(RedisKey key, double error, double probability, int? cellSize = null)
     {
-        return new(CommandCategories.WriteAccumulating, CMS.INITBYPROB, key, error, probability);
+        List<object> args = [key, error, probability];
+        AddCellSize(args, cellSize);
+
+        return new(CommandCategories.WriteAccumulating, CMS.INITBYPROB, args);
+    }
+
+    private static void AddCellSize(List<object> args, int? cellSize)
+    {
+        if (cellSize is null) return;
+
+        if (cellSize is not (1 or 2 or 4 or 8))
+            throw new ArgumentOutOfRangeException(nameof(cellSize), cellSize, "Cell size must be 1, 2, 4, or 8.");
+
+        args.Add(CmsArgs.CELL_SIZE);
+        args.Add(cellSize.Value);
     }
 
     public static SerializedCommand Merge(RedisValue destination, long numKeys, RedisValue[] source,

diff --git a/src/NRedisStack/CountMinSketch/CmsCommands.cs b/src/NRedisStack/CountMinSketch/CmsCommands.cs
@@ -32,15 +32,15 @@ public CmsInformation Info(RedisKey key)
     }
 
     /// <inheritdoc/>
-    public bool InitByDim(RedisKey key, long width, long depth)
+    public bool InitByDim(RedisKey key, long width, long depth, int? cellSize = null)
     {
-        return _db.Execute(CmsCommandBuilder.InitByDim(key, width, depth)).OKtoBoolean();
+        return _db.Execute(CmsCommandBuilder.InitByDim(key, width, depth, cellSize)).OKtoBoolean();
     }
 
     /// <inheritdoc/>
-    public bool InitByProb(RedisKey key, double error, double probability)
+    public bool InitByProb(RedisKey key, double error, double probability, int? cellSize = null)
     {
-        return _db.Execute(CmsCommandBuilder.InitByProb(key, error, probability)).OKtoBoolean();
+        return _db.Execute(CmsCommandBuilder.InitByProb(key, error, probability, cellSize)).OKtoBoolean();
     }
 
     /// <inheritdoc/>

diff --git a/src/NRedisStack/CountMinSketch/CmsCommandsAsync.cs b/src/NRedisStack/CountMinSketch/CmsCommandsAsync.cs
@@ -32,15 +32,15 @@ public async Task<CmsInformation> InfoAsync(RedisKey key)
     }
 
     /// <inheritdoc/>
-    public async Task<bool> InitByDimAsync(RedisKey key, long width, long depth)
+    public async Task<bool> InitByDimAsync(RedisKey key, long width, long depth, int? cellSize = null)
     {
-        return (await _db.ExecuteAsync(CmsCommandBuilder.InitByDim(key, width, depth))).OKtoBoolean();
+        return (await _db.ExecuteAsync(CmsCommandBuilder.InitByDim(key, width, depth, cellSize))).OKtoBoolean();
     }
 
     /// <inheritdoc/>
-    public async Task<bool> InitByProbAsync(RedisKey key, double error, double probability)
+    public async Task<bool> InitByProbAsync(RedisKey key, double error, double probability, int? cellSize = null)
     {
-        return (await _db.ExecuteAsync(CmsCommandBuilder.InitByProb(key, error, probability))).OKtoBoolean();
+        return (await _db.ExecuteAsync(CmsCommandBuilder.InitByProb(key, error, probability, cellSize))).OKtoBoolean();
     }
 
     /// <inheritdoc/>

diff --git a/src/NRedisStack/CountMinSketch/ICmsCommands.cs b/src/NRedisStack/CountMinSketch/ICmsCommands.cs
@@ -40,19 +40,21 @@ public interface ICmsCommands
     /// <param name="width">Number of counters in each array. Reduces the error size.</param>
     /// <param name="depth">Number of counter-arrays. Reduces the probability for an error
     /// of a certain size (percentage of total count).</param>
+    /// <param name="cellSize">The number of bytes per cell (1, 2, 4, or 8). Defaults to 4 on the server.</param>
     /// <returns><see langword="true"/> if if executed correctly, Error otherwise.</returns>
     /// <remarks><seealso href="https://redis.io/commands/cms.initbydim"/></remarks>
-    bool InitByDim(RedisKey key, long width, long depth);
+    bool InitByDim(RedisKey key, long width, long depth, int? cellSize = null);
 
     /// <summary>
     /// Initializes a Count-Min Sketch to accommodate requested tolerances.
     /// </summary>
     /// <param name="key">The name of the sketch.</param>
     /// <param name="error">Estimate size of error.</param>
     /// <param name="probability">The desired probability for inflated count.</param>
+    /// <param name="cellSize">The number of bytes per cell (1, 2, 4, or 8). Defaults to 4 on the server.</param>
     /// <returns><see langword="true"/> if if executed correctly, Error otherwise.</returns>
     /// <remarks><seealso href="https://redis.io/commands/cms.initbyprob"/></remarks>
-    bool InitByProb(RedisKey key, double error, double probability);
+    bool InitByProb(RedisKey key, double error, double probability, int? cellSize = null);
 
     /// <summary>
     /// Merges several sketches into one sketch.

diff --git a/src/NRedisStack/CountMinSketch/ICmsCommandsAsync.cs b/src/NRedisStack/CountMinSketch/ICmsCommandsAsync.cs
@@ -40,19 +40,21 @@ public interface ICmsCommandsAsync
     /// <param name="width">Number of counters in each array. Reduces the error size.</param>
     /// <param name="depth">Number of counter-arrays. Reduces the probability for an error
     /// of a certain size (percentage of total count).</param>
+    /// <param name="cellSize">The number of bytes per cell (1, 2, 4, or 8). Defaults to 4 on the server.</param>
     /// <returns><see langword="true"/> if if executed correctly, Error otherwise.</returns>
     /// <remarks><seealso href="https://redis.io/commands/cms.initbydim"/></remarks>
-    Task<bool> InitByDimAsync(RedisKey key, long width, long depth);
+    Task<bool> InitByDimAsync(RedisKey key, long width, long depth, int? cellSize = null);
 
     /// <summary>
     /// Initializes a Count-Min Sketch to accommodate requested tolerances.
     /// </summary>
     /// <param name="key">The name of the sketch.</param>
     /// <param name="error">Estimate size of error.</param>
     /// <param name="probability">The desired probability for inflated count.</param>
+    /// <param name="cellSize">The number of bytes per cell (1, 2, 4, or 8). Defaults to 4 on the server.</param>
     /// <returns><see langword="true"/> if if executed correctly, Error otherwise.</returns>
     /// <remarks><seealso href="https://redis.io/commands/cms.initbyprob"/></remarks>
-    Task<bool> InitByProbAsync(RedisKey key, double error, double probability);
+    Task<bool> InitByProbAsync(RedisKey key, double error, double probability, int? cellSize = null);
 
     /// <summary>
     /// Merges several sketches into one sketch.

diff --git a/src/NRedisStack/CountMinSketch/Literals/CommandArgs.cs b/src/NRedisStack/CountMinSketch/Literals/CommandArgs.cs
@@ -3,4 +3,5 @@ namespace NRedisStack.CountMinSketch.Literals;
 internal class CmsArgs
 {
     public const string WEIGHTS = "WEIGHTS";
+    public const string CELL_SIZE = "CELL_SIZE";
 }
diff --git a/src/NRedisStack/PublicAPI/PublicAPI.Shipped.txt b/src/NRedisStack/PublicAPI/PublicAPI.Shipped.txt
@@ -47,17 +47,17 @@ NRedisStack.CmsCommands.CmsCommands(StackExchange.Redis.IDatabase! db) -> void
 NRedisStack.CmsCommands.IncrBy(StackExchange.Redis.RedisKey key, StackExchange.Redis.RedisValue item, long increment) -> long
 NRedisStack.CmsCommands.IncrBy(StackExchange.Redis.RedisKey key, System.Tuple<StackExchange.Redis.RedisValue, long>![]! itemIncrements) -> long[]!
 NRedisStack.CmsCommands.Info(StackExchange.Redis.RedisKey key) -> NRedisStack.CountMinSketch.DataTypes.CmsInformation!
-NRedisStack.CmsCommands.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth) -> bool
-NRedisStack.CmsCommands.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability) -> bool
+NRedisStack.CmsCommands.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth, int? cellSize = null) -> bool
+NRedisStack.CmsCommands.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability, int? cellSize = null) -> bool
 NRedisStack.CmsCommands.Merge(StackExchange.Redis.RedisValue destination, long numKeys, StackExchange.Redis.RedisValue[]! source, long[]? weight = null) -> bool
 NRedisStack.CmsCommands.Query(StackExchange.Redis.RedisKey key, params StackExchange.Redis.RedisValue[]! items) -> long[]!
 NRedisStack.CmsCommandsAsync
 NRedisStack.CmsCommandsAsync.CmsCommandsAsync(StackExchange.Redis.IDatabaseAsync! db) -> void
 NRedisStack.CmsCommandsAsync.IncrByAsync(StackExchange.Redis.RedisKey key, StackExchange.Redis.RedisValue item, long increment) -> System.Threading.Tasks.Task<long>!
 NRedisStack.CmsCommandsAsync.IncrByAsync(StackExchange.Redis.RedisKey key, System.Tuple<StackExchange.Redis.RedisValue, long>![]! itemIncrements) -> System.Threading.Tasks.Task<long[]!>!
 NRedisStack.CmsCommandsAsync.InfoAsync(StackExchange.Redis.RedisKey key) -> System.Threading.Tasks.Task<NRedisStack.CountMinSketch.DataTypes.CmsInformation!>!
-NRedisStack.CmsCommandsAsync.InitByDimAsync(StackExchange.Redis.RedisKey key, long width, long depth) -> System.Threading.Tasks.Task<bool>!
-NRedisStack.CmsCommandsAsync.InitByProbAsync(StackExchange.Redis.RedisKey key, double error, double probability) -> System.Threading.Tasks.Task<bool>!
+NRedisStack.CmsCommandsAsync.InitByDimAsync(StackExchange.Redis.RedisKey key, long width, long depth, int? cellSize = null) -> System.Threading.Tasks.Task<bool>!
+NRedisStack.CmsCommandsAsync.InitByProbAsync(StackExchange.Redis.RedisKey key, double error, double probability, int? cellSize = null) -> System.Threading.Tasks.Task<bool>!
 NRedisStack.CmsCommandsAsync.MergeAsync(StackExchange.Redis.RedisValue destination, long numKeys, StackExchange.Redis.RedisValue[]! source, long[]? weight = null) -> System.Threading.Tasks.Task<bool>!
 NRedisStack.CmsCommandsAsync.QueryAsync(StackExchange.Redis.RedisKey key, params StackExchange.Redis.RedisValue[]! items) -> System.Threading.Tasks.Task<long[]!>!
 NRedisStack.Core.DataTypes.MinMaxModifier
@@ -191,16 +191,16 @@ NRedisStack.ICmsCommands
 NRedisStack.ICmsCommands.IncrBy(StackExchange.Redis.RedisKey key, StackExchange.Redis.RedisValue item, long increment) -> long
 NRedisStack.ICmsCommands.IncrBy(StackExchange.Redis.RedisKey key, System.Tuple<StackExchange.Redis.RedisValue, long>![]! itemIncrements) -> long[]!
 NRedisStack.ICmsCommands.Info(StackExchange.Redis.RedisKey key) -> NRedisStack.CountMinSketch.DataTypes.CmsInformation!
-NRedisStack.ICmsCommands.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth) -> bool
-NRedisStack.ICmsCommands.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability) -> bool
+NRedisStack.ICmsCommands.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth, int? cellSize = null) -> bool
+NRedisStack.ICmsCommands.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability, int? cellSize = null) -> bool
 NRedisStack.ICmsCommands.Merge(StackExchange.Redis.RedisValue destination, long numKeys, StackExchange.Redis.RedisValue[]! source, long[]? weight = null) -> bool
 NRedisStack.ICmsCommands.Query(StackExchange.Redis.RedisKey key, params StackExchange.Redis.RedisValue[]! items) -> long[]!
 NRedisStack.ICmsCommandsAsync
 NRedisStack.ICmsCommandsAsync.IncrByAsync(StackExchange.Redis.RedisKey key, StackExchange.Redis.RedisValue item, long increment) -> System.Threading.Tasks.Task<long>!
 NRedisStack.ICmsCommandsAsync.IncrByAsync(StackExchange.Redis.RedisKey key, System.Tuple<StackExchange.Redis.RedisValue, long>![]! itemIncrements) -> System.Threading.Tasks.Task<long[]!>!
 NRedisStack.ICmsCommandsAsync.InfoAsync(StackExchange.Redis.RedisKey key) -> System.Threading.Tasks.Task<NRedisStack.CountMinSketch.DataTypes.CmsInformation!>!
-NRedisStack.ICmsCommandsAsync.InitByDimAsync(StackExchange.Redis.RedisKey key, long width, long depth) -> System.Threading.Tasks.Task<bool>!
-NRedisStack.ICmsCommandsAsync.InitByProbAsync(StackExchange.Redis.RedisKey key, double error, double probability) -> System.Threading.Tasks.Task<bool>!
+NRedisStack.ICmsCommandsAsync.InitByDimAsync(StackExchange.Redis.RedisKey key, long width, long depth, int? cellSize = null) -> System.Threading.Tasks.Task<bool>!
+NRedisStack.ICmsCommandsAsync.InitByProbAsync(StackExchange.Redis.RedisKey key, double error, double probability, int? cellSize = null) -> System.Threading.Tasks.Task<bool>!
 NRedisStack.ICmsCommandsAsync.MergeAsync(StackExchange.Redis.RedisValue destination, long numKeys, StackExchange.Redis.RedisValue[]! source, long[]? weight = null) -> System.Threading.Tasks.Task<bool>!
 NRedisStack.ICmsCommandsAsync.QueryAsync(StackExchange.Redis.RedisKey key, params StackExchange.Redis.RedisValue[]! items) -> System.Threading.Tasks.Task<long[]!>!
 NRedisStack.ICuckooCommands
@@ -1292,8 +1292,8 @@ static NRedisStack.BloomCommandBuilder.ScanDump(StackExchange.Redis.RedisKey key
 static NRedisStack.CmsCommandBuilder.IncrBy(StackExchange.Redis.RedisKey key, StackExchange.Redis.RedisValue item, long increment) -> NRedisStack.RedisStackCommands.SerializedCommand!
 static NRedisStack.CmsCommandBuilder.IncrBy(StackExchange.Redis.RedisKey key, System.Tuple<StackExchange.Redis.RedisValue, long>![]! itemIncrements) -> NRedisStack.RedisStackCommands.SerializedCommand!
 static NRedisStack.CmsCommandBuilder.Info(StackExchange.Redis.RedisKey key) -> NRedisStack.RedisStackCommands.SerializedCommand!
-static NRedisStack.CmsCommandBuilder.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth) -> NRedisStack.RedisStackCommands.SerializedCommand!
-static NRedisStack.CmsCommandBuilder.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability) -> NRedisStack.RedisStackCommands.SerializedCommand!
+static NRedisStack.CmsCommandBuilder.InitByDim(StackExchange.Redis.RedisKey key, long width, long depth, int? cellSize = null) -> NRedisStack.RedisStackCommands.SerializedCommand!
+static NRedisStack.CmsCommandBuilder.InitByProb(StackExchange.Redis.RedisKey key, double error, double probability, int? cellSize = null) -> NRedisStack.RedisStackCommands.SerializedCommand!
 static NRedisStack.CmsCommandBuilder.Merge(StackExchange.Redis.RedisValue destination, long numKeys, StackExchange.Redis.RedisValue[]! source, long[]? weight = null) -> NRedisStack.RedisStackCommands.SerializedCommand!
 static NRedisStack.CmsCommandBuilder.Query(StackExchange.Redis.RedisKey key, params StackExchange.Redis.RedisValue[]! items) -> NRedisStack.RedisStackCommands.SerializedCommand!
 static NRedisStack.Core.DataTypes.MinMaxModifierExtensions.ToMinMax(this StackExchange.Redis.Order order) -> NRedisStack.Core.DataTypes.MinMaxModifier

diff --git a/src/NRedisStack/ResponseParser.cs b/src/NRedisStack/ResponseParser.cs
@@ -516,7 +516,7 @@ public static CmsInformation
                 case "count":
                     count = (long)redisResults[i];
                     break;
-                case "cell size":
+                case "cell_size":
                     cellSize = (int)redisResults[i];
                     break;
             }

diff --git a/tests/NRedisStack.Tests/CountMinSketch/CmsTests.cs b/tests/NRedisStack.Tests/CountMinSketch/CmsTests.cs
@@ -39,6 +39,48 @@
         Assert.Equal(0, info.Count);
     }
 
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public void TestInitByDimCellSize(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        cms.InitByDim(key, 16, 4, cellSize: 1);
+        var info = cms.Info(key);
+
+        Assert.Equal(16, info.Width);
+        Assert.Equal(4, info.Depth);
+        Assert.Equal(0, info.Count);
+        Assert.Equal(1, info.CellSize);
+    }
+
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public async Task TestInitByDimCellSizeAsync(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        await cms.InitByDimAsync(key, 16, 4, cellSize: 8);
+        var info = await cms.InfoAsync(key);
+
+        Assert.Equal(16, info.Width);
+        Assert.Equal(4, info.Depth);
+        Assert.Equal(0, info.Count);
+        Assert.Equal(8, info.CellSize);
+    }
+
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public void TestInitByDimInvalidCellSize(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => cms.InitByDim(key, 16, 4, cellSize: 3));
+    }
+
     [Theory]
     [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
     public void TestInitByProb(string endpointId)
@@ -54,6 +96,22 @@
         Assert.Equal(0, info.Count);
     }
 
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public void TestInitByProbCellSize(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        cms.InitByProb(key, 0.01, 0.01, cellSize: 2);
+        var info = cms.Info(key);
+
+        Assert.Equal(200, info.Width);
+        Assert.Equal(7, info.Depth);
+        Assert.Equal(0, info.Count);
+        Assert.Equal(2, info.CellSize);
+    }
+
     [Theory]
     [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
     public async Task TestInitByProbAsync(string endpointId)
@@ -127,6 +185,38 @@
 
     }
 
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public void TestIncrByNegative(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        cms.InitByDim(key, 1000, 5);
+        cms.IncrBy(key, "foo", 10);
+        var resp = cms.IncrBy(key, "foo", -4);
+        Assert.Equal(6, resp);
+
+        var info = cms.Info(key);
+        Assert.Equal(6, info.Count);
+    }
+
+    [Theory]
+    [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
+    public async Task TestIncrByNegativeAsync(string endpointId)
+    {
+        var db = GetCleanDatabase(endpointId);
+        var cms = db.CMS();
+
+        await cms.InitByDimAsync(key, 1000, 5);
+        await cms.IncrByAsync(key, "foo", 10);
+        var resp = await cms.IncrByAsync(key, "foo", -4);
+        Assert.Equal(6, resp);
+
+        var info = await cms.InfoAsync(key);
+        Assert.Equal(6, info.Count);
+    }
+
     [Theory]
     [MemberData(nameof(EndpointsFixture.Env.AllEnvironments), MemberType = typeof(EndpointsFixture.Env))]
     public void TestIncrByMultipleArgs(string endpointId)