Azure · timotheeguerin · May 6, 2026 · May 6, 2026 · May 6, 2026 · May 12, 2026
@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@azure-tools/azure-http-specs"
+---
+
+Remove use of implicit optionality which was a noop in one operation
@@ -0,0 +1,41 @@
+---
+changeKind: breaking
+packages:
+  - "@azure-tools/typespec-azure-resource-manager"
+---
+
+Removed `implicitOptionality: true` from the `@patch` decorator on the following operation templates:
+
+- `ArmTagsPatchAsync`
+- `ArmResourcePatchAsync`
+- `ArmTagsPatchSync`
+- `ArmResourcePatchSync`
+- `ResourceUpdateSync.update` (in `ResourceUpdateSync` interface)
+
+Previously, these templates used `@patch(#{ implicitOptionality: true })` which caused all properties in the PATCH request body to be implicitly treated as optional, regardless of how they were declared in the model. This behavior is now removed — properties will retain their declared optionality.
+
+#### Migration
+
+If you use these ARM operation templates, the PATCH body will no longer implicitly make all properties optional. In most cases, ARM resources already use `ResourceUpdateModel<Resource, Properties>` which produces the correct optional property envelope — if so, **no changes are needed**.
+
+If you have a custom patch body that relied on implicit optionality, explicitly mark properties as optional:
+
+**Before** (implicit optionality made all properties optional automatically):
+
+```tsp
+model MyResourceProperties {
+  displayName: string;
+  config: MyConfig;
+}
+```
+
+**After** (explicitly declare optional properties for update):
+
+```tsp
+model MyResourceUpdateProperties {
+  displayName?: string;
+  config?: MyConfig;
+}
+```
+
+Or continue using `ResourceUpdateModel<Resource, Properties>` which already handles this transformation for standard ARM resource patterns.
@@ -0,0 +1,37 @@
+---
+changeKind: breaking
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+Removed `implicitOptionality: true` from the `@patch` decorator on the following operation templates:
+
+- `ResourceCreateOrUpdate`
+- `LongRunningResourceCreateOrUpdate`
+- `ResourceUpdate`
+
+Previously, these templates used `@patch(#{ implicitOptionality: true })` which caused all properties in the PATCH request body to be implicitly treated as optional, regardless of how they were declared in the model. This behavior is now removed — properties will retain their declared optionality.
+
+#### Migration
+
+If your service relies on all properties being optional in the PATCH body, you need to explicitly mark them as optional in your model:
+
+**Before** (implicit optionality made all properties optional automatically):
+
+```tsp
+model Widget {
+  name: string;
+  color: string;
+}
+```
+
+**After** (explicitly declare optional properties):
+
+```tsp
+model WidgetUpdate {
+  name?: string;
+  color?: string;
+}
+```
+
+Alternatively, you can use the `ResourceUpdateModel` template or `OptionalProperties` utility to derive an all-optional version of your model for PATCH operations. If you were already using `ResourceUpdateModel<Resource>` or manually defining optional properties in your update model, no changes are needed.
@@ -104,7 +104,7 @@ model UpdateWidgetColorRequest {
   ```
   """)
 @doc("Update widget color (preview only)")
-@patch(#{ implicitOptionality: true })
+@patch
 @route("/widgets/{id}/color")
 @added(ApiVersions.v2024_12_01_preview)
 op updateWidgetColor(

@@ -155,12 +155,10 @@ interface ResourceOperations<
    * @template Resource Resource type.
    * @template Traits Object describing the traits of the operation.
    */
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
   @Foundations.Private.ensureVerb("ResourceCreateOrUpdate", "PATCH")
   @createsOrUpdatesResource(Resource)
   @parameterVisibility(Lifecycle.Create, Lifecycle.Update)
-  @patch(#{ implicitOptionality: true }) // For legacy reasons
+  @patch
   ResourceCreateOrUpdate<
     Resource extends TypeSpec.Reflection.Model,
     Traits extends TypeSpec.Reflection.Model = {}
@@ -193,12 +191,10 @@ interface ResourceOperations<
    * @template Resource Resource type.
    * @template Traits Object describing the traits of the operation.
    */
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
   @Foundations.Private.ensureVerb("LongRunningResourceCreateOrUpdate", "PATCH")
   @createsOrUpdatesResource(Resource)
   @parameterVisibility(Lifecycle.Create, Lifecycle.Update)
-  @patch(#{ implicitOptionality: true }) // For legacy reasons
+  @patch
   LongRunningResourceCreateOrUpdate<
     Resource extends TypeSpec.Reflection.Model,
     Traits extends TypeSpec.Reflection.Model = {}
@@ -232,10 +228,9 @@ interface ResourceOperations<
    * @template Resource Resource type.
    * @template Traits Object describing the traits of the operation.
    */
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
   @Foundations.Private.ensureVerb("ResourceUpdate", "PATCH")
   @updatesResource(Resource)
-  @patch(#{ implicitOptionality: true }) // For legacy reasons
+  @patch
   ResourceUpdate<
     Resource extends TypeSpec.Reflection.Model,
     Traits extends TypeSpec.Reflection.Model = {}

@@ -232,7 +232,7 @@ op CreateOrReplaceAsync<
 @extensionResourceOperation(TargetResource, ExtensionResource, "update", OverrideResourceName)
 @enforceConstraint(TargetResource, Foundations.Resource)
 @enforceConstraint(ExtensionResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchAsync<
   TargetResource extends Foundations.SimpleResource,
   ExtensionResource extends Foundations.SimpleResource,
@@ -271,7 +271,7 @@ op CustomPatchAsync<
 @extensionResourceOperation(TargetResource, ExtensionResource, "update", OverrideResourceName)
 @enforceConstraint(TargetResource, Foundations.Resource)
 @enforceConstraint(ExtensionResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchSync<
   TargetResource extends Foundations.SimpleResource,
   ExtensionResource extends Foundations.SimpleResource,

@@ -326,8 +326,7 @@ interface ResourceUpdateSync<
    * @template Properties RP-specific property bag for the resource
    * @template BaseParameters The http parameters that are part of the request
    */
-  #suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-  @patch(#{ implicitOptionality: true })
+  @patch
   update is ArmCustomPatchSync<Resource, ResourceUpdateModel<Resource, Properties>, BaseParameters>;
 }
 

@@ -150,7 +150,7 @@ op CreateOrReplaceSync<
 @extensionResourceOperation(TargetResource, ExtensionResource, "update", OverrideResourceName)
 @enforceConstraint(TargetResource, Foundations.Resource)
 @enforceConstraint(ExtensionResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchAsync<
   TargetResource extends Foundations.SimpleResource,
   ExtensionResource extends Foundations.SimpleResource,
@@ -193,7 +193,7 @@ op CustomPatchAsync<
 @extensionResourceOperation(TargetResource, ExtensionResource, "update", OverrideResourceName)
 @enforceConstraint(TargetResource, Foundations.Resource)
 @enforceConstraint(ExtensionResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchSync<
   TargetResource extends Foundations.SimpleResource,
   ExtensionResource extends Foundations.SimpleResource,

@@ -107,7 +107,7 @@ interface ExtensionOperations<
   @armOperationRoute(OperationOptions)
   @doc("Update a {name}", Resource)
   @legacyExtensionResourceOperation(Resource, "update", OverrideResourceName)
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchAsync<
     Resource extends Foundations.SimpleResource,
     PatchModel extends {} | void = Azure.ResourceManager.Foundations.TagsUpdateModel<Resource>,
@@ -146,7 +146,7 @@ interface ExtensionOperations<
   @armOperationRoute(OperationOptions)
   @doc("Update a {name}", Resource)
   @legacyExtensionResourceOperation(Resource, "update", OverrideResourceName)
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchSync<
     Resource extends Foundations.SimpleResource,
     PatchModel extends {} | void = Azure.ResourceManager.Foundations.TagsUpdateModel<Resource>,

@@ -135,7 +135,7 @@ interface RoutedOperations<
   @armOperationRoute(OverrideRouteOptions)
   @legacyResourceOperation(Resource, "update", OverrideResourceName)
   @Private.armUpdateProviderNamespace
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchAsync<
     Resource extends Foundations.SimpleResource,
     PatchModel extends {} | void = Azure.ResourceManager.Foundations.TagsUpdateModel<Resource>,
@@ -175,7 +175,7 @@ interface RoutedOperations<
   @armOperationRoute(OverrideRouteOptions)
   @legacyResourceOperation(Resource, "update", OverrideResourceName)
   @Private.armUpdateProviderNamespace
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchSync<
     Resource extends Foundations.SimpleResource,
     PatchModel extends {} | void = Azure.ResourceManager.Foundations.TagsUpdateModel<Resource>,
@@ -464,7 +464,7 @@ model ProviderParameter<Resource extends {}> {
 @doc("Update a {name}", Resource)
 @armResourceUpdate(Resource)
 @Private.enforceConstraint(Resource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchAsync<
   Resource extends Foundations.SimpleResource,
   PatchModel extends TypeSpec.Reflection.Model | void = TagsUpdateModel<Resource>,
@@ -503,7 +503,7 @@ op CustomPatchAsync<
 @doc("Update a {name}", Resource)
 @armResourceUpdate(Resource)
 @Private.enforceConstraint(Resource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchSync<
   Resource extends Foundations.SimpleResource,
   PatchModel extends TypeSpec.Reflection.Model | void = TagsUpdateModel<Resource>,

@@ -132,7 +132,7 @@ op CreateOrReplaceAsync<
 @doc("Update a {name} PrivateEndpointConnection", ParentResource)
 @armResourceUpdate(Resource)
 @Private.enforceConstraint(ParentResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchAsync<
   ParentResource extends Foundations.SimpleResource,
   Resource extends PrivateEndpointConnectionResource,
@@ -175,7 +175,7 @@ op CustomPatchAsync<
 @doc("Update a {name} PrivateEndpointConnection", ParentResource)
 @armResourceUpdate(Resource)
 @Private.enforceConstraint(ParentResource, Foundations.Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 op CustomPatchSync<
   ParentResource extends Foundations.SimpleResource,
   Resource extends PrivateEndpointConnectionResource,

@@ -342,8 +342,7 @@ op ArmResourceCreateOrReplaceAsync<
  * @template Parameters Optional. Additional parameters after the path parameters
  * @template Provider Optional. The provider namespace model for the resource.
  */
-#suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-@patch(#{ implicitOptionality: true })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmTagsPatchAsync<
   Resource extends Foundations.SimpleResource,
@@ -377,8 +376,7 @@ op ArmTagsPatchAsync<
  * @template Parameters Optional. Additional parameters after the path parameters
  * @template Provider Optional. The provider namespace model for the resource.
  */
-#suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-@patch(#{ implicitOptionality: true })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmResourcePatchAsync<
   Resource extends Foundations.SimpleResource,
@@ -417,7 +415,7 @@ op ArmResourcePatchAsync<
 @autoRoute
 @doc("Update a {name}", Resource)
 @armResourceUpdate(Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmCustomPatchAsync<
   Resource extends Foundations.SimpleResource,
@@ -449,8 +447,7 @@ op ArmCustomPatchAsync<
  * @template Parameters Optional. Additional parameters after the path parameters
  * @template Provider Optional. The provider namespace model for the resource.
  */
-#suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-@patch(#{ implicitOptionality: true })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmTagsPatchSync<
   Resource extends Foundations.SimpleResource,
@@ -475,8 +472,7 @@ op ArmTagsPatchSync<
  * @template Parameters Optional. Additional parameters after the path parameters
  * @template Provider Optional. The provider namespace model for the resource.
  */
-#suppress "@typespec/http/deprecated-implicit-optionality" "Legacy"
-@patch(#{ implicitOptionality: true })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmResourcePatchSync<
   Resource extends Foundations.SimpleResource,
@@ -507,7 +503,7 @@ op ArmResourcePatchSync<
 @autoRoute
 @doc("Update a {name}", Resource)
 @armResourceUpdate(Resource)
-@patch(#{ implicitOptionality: false })
+@patch
 @Private.enforceConstraint(Resource, Foundations.Resource)
 op ArmCustomPatchSync<
   Resource extends Foundations.SimpleResource,

@@ -244,7 +244,7 @@ interface PrivateEndpoints<
   @doc("Update a {name} PrivateEndpointConnection", ParentResource)
   @builtInResourceOperation(ParentResource, Resource, "update", OverrideResourceName)
   @Private.enforceConstraint(ParentResource, Foundations.Resource)
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchAsync<
     ParentResource extends Foundations.SimpleResource,
     Resource extends PrivateEndpointConnectionResource = PrivateEndpointResource,
@@ -286,7 +286,7 @@ interface PrivateEndpoints<
   @doc("Update a {name PrivateEndpointConnection}", ParentResource)
   @builtInResourceOperation(ParentResource, Resource, "update", OverrideResourceName)
   @Private.enforceConstraint(ParentResource, Foundations.Resource)
-  @patch(#{ implicitOptionality: false })
+  @patch
   CustomPatchSync<
     ParentResource extends Foundations.SimpleResource,
     Resource extends PrivateEndpointConnectionResource = PrivateEndpointResource,