diff --git a/src/ZB.MOM.WW.ScadaBridge.InboundAPI/ParameterValidator.cs b/src/ZB.MOM.WW.ScadaBridge.InboundAPI/ParameterValidator.cs
index 8e343438..30e84fe7 100644
--- a/src/ZB.MOM.WW.ScadaBridge.InboundAPI/ParameterValidator.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.InboundAPI/ParameterValidator.cs
@@ -135,6 +135,20 @@ public static class ParameterValidator
     /// Validation has already passed, so this only shapes the value: scalars to
     /// their primitive type, objects to <see cref="Dictionary{TKey,TValue}"/>,
     /// arrays to <see cref="List{T}"/>.
+    ///
+    /// <para>
+    /// InboundAPI-#55: coercion is RECURSIVE. Nested object fields and list
+    /// elements are coerced to typed CLR values too (string/long/double/bool,
+    /// or nested Dictionary/List), so NO raw <see cref="JsonElement"/> survives
+    /// anywhere in the returned graph. Previously the <c>object</c> case used
+    /// <c>JsonSerializer.Deserialize&lt;Dictionary&lt;string, object?&gt;&gt;</c>,
+    /// which leaves every nested field value as a <see cref="JsonElement"/> — so
+    /// nested scalars reached the script as JsonElement-backed values rather than
+    /// the typed CLR values the top-level scalar path already produces. The
+    /// declared field schemas are walked here so nested coercion matches the
+    /// shape the validator already verified (an Object recurses into its declared
+    /// fields; an array coerces each element to its element type).
+    /// </para>
     /// </summary>
     private static object? Materialize(JsonElement element, InboundApiSchema schema)
     {
@@ -149,12 +163,50 @@ public static class ParameterValidator
             "integer" => element.GetInt64(),
             "number" => element.GetDouble(),
             "string" => element.GetString(),
-            "object" => JsonSerializer.Deserialize<Dictionary<string, object?>>(element.GetRawText()),
+            "object" => MaterializeObject(element, schema),
             "array" => MaterializeArray(element, schema.Items),
-            _ => JsonSerializer.Deserialize<object?>(element.GetRawText()),
+            // Undeclared / shape-only ("ref" placeholder or any non-extended type):
+            // coerce structurally so no raw JsonElement survives.
+            _ => MaterializeJsonValue(element),
         };
     }
 
+    /// <summary>
+    /// Materializes a JSON object to a <c>Dictionary&lt;string, object?&gt;</c> of
+    /// typed CLR values. Each declared field's value is recursively coerced via
+    /// <see cref="Materialize"/> against the field's schema, so nested scalars
+    /// arrive as their CLR primitive (string/long/double/bool) rather than as a
+    /// raw <see cref="JsonElement"/>. Any field present in the body but NOT declared
+    /// (only reachable on a shape-only <c>{"type":"object"}</c> node with no declared
+    /// fields, since the validator rejects undeclared fields where fields ARE
+    /// declared) is coerced structurally via <see cref="MaterializeJsonValue"/>.
+    /// </summary>
+    private static object? MaterializeObject(JsonElement element, InboundApiSchema schema)
+    {
+        // Shape-only object (no declared fields): coerce structurally so the whole
+        // graph is typed CLR with no JsonElement leakage.
+        if (schema.Fields.Count == 0)
+        {
+            return MaterializeJsonValue(element);
+        }
+
+        var fieldSchemas = new Dictionary<string, InboundApiSchema>(StringComparer.Ordinal);
+        foreach (var field in schema.Fields)
+        {
+            fieldSchemas[field.Name] = field.Schema;
+        }
+
+        var dict = new Dictionary<string, object?>();
+        foreach (var prop in element.EnumerateObject())
+        {
+            dict[prop.Name] = fieldSchemas.TryGetValue(prop.Name, out var fieldSchema)
+                ? Materialize(prop.Value, fieldSchema)
+                : MaterializeJsonValue(prop.Value);
+        }
+
+        return dict;
+    }
+
     /// <summary>
     /// Materializes a JSON array to a STRONGLY-TYPED list (List&lt;string&gt;,
     /// List&lt;long&gt;, List&lt;double&gt;, List&lt;bool&gt;) per the element schema,
@@ -197,11 +249,22 @@ public static class ParameterValidator
                     list.Add(e.ValueKind == JsonValueKind.Null ? string.Empty : e.GetString() ?? string.Empty);
                 return list;
             }
+            case "object":
+            case "array":
+            {
+                // Declared object/array element: recurse via Materialize so each
+                // element follows its declared (nested) schema — nested scalars
+                // become typed CLR values, never raw JsonElement (#55).
+                var list = new List<object?>(element.GetArrayLength());
+                foreach (var e in element.EnumerateArray()) list.Add(Materialize(e, items));
+                return list;
+            }
             default:
             {
-                // No declared (or non-scalar) element type: materialize each element
-                // to its CLR value so no raw JsonElement survives (raw JsonElement is
-                // not cleanly Akka-serializable and stalls the List-attribute encode).
+                // No declared (or non-extended) element type: materialize each
+                // element structurally so no raw JsonElement survives (raw
+                // JsonElement is not cleanly Akka-serializable and stalls the
+                // List-attribute encode).
                 var list = new List<object?>(element.GetArrayLength());
                 foreach (var e in element.EnumerateArray()) list.Add(MaterializeJsonValue(e));
                 return list;
diff --git a/tests/ZB.MOM.WW.ScadaBridge.InboundAPI.Tests/ParameterValidatorTests.cs b/tests/ZB.MOM.WW.ScadaBridge.InboundAPI.Tests/ParameterValidatorTests.cs
index de384994..5425a3ef 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.InboundAPI.Tests/ParameterValidatorTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.InboundAPI.Tests/ParameterValidatorTests.cs
@@ -350,6 +350,194 @@ public class ParameterValidatorTests
         Assert.True(result.IsValid);
     }
 
+    // ── Recursive materialization: nested values coerced to typed CLR (#55) ─────
+
+    /// <summary>
+    /// Recursively asserts that no value anywhere in a materialized parameter
+    /// graph is a raw <see cref="JsonElement"/> — every scalar must be a typed CLR
+    /// value (string/long/double/bool/null) and every container a
+    /// <c>Dictionary&lt;string, object?&gt;</c> / <c>List&lt;object?&gt;</c> (or a
+    /// typed scalar list) of likewise-coerced values.
+    /// </summary>
+    private static void AssertNoJsonElement(object? value)
+    {
+        Assert.IsNotType<JsonElement>(value);
+
+        switch (value)
+        {
+            case IDictionary<string, object?> dict:
+                foreach (var v in dict.Values)
+                {
+                    AssertNoJsonElement(v);
+                }
+
+                break;
+            case System.Collections.IEnumerable enumerable when value is not string:
+                foreach (var item in enumerable)
+                {
+                    AssertNoJsonElement(item);
+                }
+
+                break;
+        }
+    }
+
+    [Fact]
+    public void NestedObjectFieldScalar_IsTypedClr_NotJsonElement()
+    {
+        const string body = """
+        {"order":{
+            "id":7,
+            "customer":{"name":"Acme","vip":true},
+            "items":[]
+        }}
+        """;
+
+        var result = ParameterValidator.Validate(Body(body), NestedDef);
+        Assert.True(result.IsValid);
+
+        var order = Assert.IsType<Dictionary<string, object?>>(result.Parameters["order"]);
+        AssertNoJsonElement(order);
+
+        // The nested scalar fields are the CLR types the top-level path produces:
+        // integer→long, string→string, boolean→bool.
+        Assert.Equal((long)7, order["id"]);
+
+        var customer = Assert.IsType<Dictionary<string, object?>>(order["customer"]);
+        Assert.Equal("Acme", customer["name"]);
+        Assert.Equal(true, customer["vip"]);
+        Assert.IsType<bool>(customer["vip"]);
+        Assert.IsType<long>(order["id"]);
+    }
+
+    [Fact]
+    public void ListOfScalars_FullyCoerced_NoJsonElement()
+    {
+        const string def = """{"type":"object","properties":{"nums":{"type":"array","items":{"type":"integer"}}},"required":["nums"]}""";
+
+        var result = ParameterValidator.Validate(Body("{\"nums\":[1,2,3]}"), def);
+        Assert.True(result.IsValid);
+
+        // Declared scalar element → strongly-typed List<long>.
+        var nums = Assert.IsType<List<long>>(result.Parameters["nums"]);
+        Assert.Equal(new List<long> { 1, 2, 3 }, nums);
+        AssertNoJsonElement(nums);
+    }
+
+    [Fact]
+    public void ListOfObjects_ElementFieldsCoerced_NoJsonElement()
+    {
+        const string def = """
+        {"type":"object","properties":{
+            "items":{"type":"array","items":{
+                "type":"object",
+                "properties":{"sku":{"type":"string"},"quantity":{"type":"integer"},"price":{"type":"number"}},
+                "required":["sku","quantity"]
+            }}
+        },"required":["items"]}
+        """;
+
+        const string body = """{"items":[{"sku":"A1","quantity":3,"price":9.5},{"sku":"B2","quantity":1,"price":2.0}]}""";
+
+        var result = ParameterValidator.Validate(Body(body), def);
+        Assert.True(result.IsValid);
+
+        var items = Assert.IsType<List<object?>>(result.Parameters["items"]);
+        AssertNoJsonElement(items);
+
+        var first = Assert.IsType<Dictionary<string, object?>>(items[0]);
+        Assert.Equal("A1", first["sku"]);
+        Assert.Equal((long)3, first["quantity"]);
+        Assert.IsType<long>(first["quantity"]);
+        Assert.Equal(9.5, first["price"]);
+        Assert.IsType<double>(first["price"]);
+    }
+
+    [Fact]
+    public void DeeplyNested_ObjectInListInObject_FullyCoerced_NoJsonElement()
+    {
+        // order.items[*] is an object that itself carries a list of tag objects:
+        // object → array → object → scalar, the worst-case leak path.
+        const string def = """
+        {"type":"object","properties":{
+            "order":{"type":"object","properties":{
+                "id":{"type":"integer"},
+                "items":{"type":"array","items":{
+                    "type":"object","properties":{
+                        "sku":{"type":"string"},
+                        "tags":{"type":"array","items":{
+                            "type":"object","properties":{
+                                "key":{"type":"string"},
+                                "weight":{"type":"number"},
+                                "active":{"type":"boolean"}
+                            },"required":["key"]
+                        }}
+                    },"required":["sku"]
+                }}
+            },"required":["id","items"]}
+        },"required":["order"]}
+        """;
+
+        const string body = """
+        {"order":{
+            "id":7,
+            "items":[
+                {"sku":"A1","tags":[{"key":"hot","weight":1.5,"active":true},{"key":"cold","weight":0.25,"active":false}]}
+            ]
+        }}
+        """;
+
+        var result = ParameterValidator.Validate(Body(body), def);
+        Assert.True(result.IsValid);
+
+        // The whole graph must be free of JsonElement at every depth.
+        AssertNoJsonElement(result.Parameters["order"]);
+
+        var order = Assert.IsType<Dictionary<string, object?>>(result.Parameters["order"]);
+        Assert.Equal((long)7, order["id"]);
+
+        var items = Assert.IsType<List<object?>>(order["items"]);
+        var item0 = Assert.IsType<Dictionary<string, object?>>(items[0]);
+        Assert.Equal("A1", item0["sku"]);
+
+        var tags = Assert.IsType<List<object?>>(item0["tags"]);
+        var tag0 = Assert.IsType<Dictionary<string, object?>>(tags[0]);
+        Assert.Equal("hot", tag0["key"]);
+        Assert.Equal(1.5, tag0["weight"]);
+        Assert.IsType<double>(tag0["weight"]);
+        Assert.Equal(true, tag0["active"]);
+        Assert.IsType<bool>(tag0["active"]);
+
+        var tag1 = Assert.IsType<Dictionary<string, object?>>(tags[1]);
+        Assert.Equal(false, tag1["active"]);
+    }
+
+    [Fact]
+    public void ShapeOnlyNestedObject_StillFullyCoerced_NoJsonElement()
+    {
+        // A declared-but-shape-only object field ({"type":"object"} with no
+        // properties) is still coerced structurally — no JsonElement survives.
+        // Without a declared field schema there is no integer/float distinction,
+        // so (per the pre-existing structural-coercion path) numbers come back as
+        // double; the point of THIS test is the absence of JsonElement, not the
+        // integer-vs-double choice (the declared paths cover that).
+        const string def = """{"type":"object","properties":{"data":{"type":"object"}},"required":["data"]}""";
+
+        const string body = """{"data":{"name":"x","count":5,"ratio":1.5,"flag":true,"nested":{"inner":2}}}""";
+
+        var result = ParameterValidator.Validate(Body(body), def);
+        Assert.True(result.IsValid);
+
+        var data = Assert.IsType<Dictionary<string, object?>>(result.Parameters["data"]);
+        AssertNoJsonElement(data);
+        Assert.Equal("x", data["name"]);
+        Assert.Equal(5d, data["count"]);
+        Assert.Equal(1.5, data["ratio"]);
+        Assert.Equal(true, data["flag"]);
+        var nested = Assert.IsType<Dictionary<string, object?>>(data["nested"]);
+        Assert.Equal(2d, nested["inner"]);
+    }
+
     // ── Legacy flat-array backward-compat ──────────────────────────────────────
 
     [Fact]