diff --git a/.chronus/changes/cleanup-autorest-diagnostics-2024-2-12-17-55-36.md b/.chronus/changes/cleanup-autorest-diagnostics-2024-2-12-17-55-36.md
new file mode 100644
index 0000000000..ec1e6ec1c4
--- /dev/null
+++ b/.chronus/changes/cleanup-autorest-diagnostics-2024-2-12-17-55-36.md
@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@azure-tools/typespec-autorest"
+---
+
+Cleanup autorest diagnostics
diff --git a/.chronus/changes/enable-no-enum-rule-2024-2-21-16-42-36.md b/.chronus/changes/enable-no-enum-rule-2024-2-21-16-42-36.md
new file mode 100644
index 0000000000..3768d3d751
--- /dev/null
+++ b/.chronus/changes/enable-no-enum-rule-2024-2-21-16-42-36.md
@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+Enable `no-enum` rule by default in `all` ruleset
diff --git a/.chronus/changes/enum_fixed-2024-2-21-15-54-49.md b/.chronus/changes/enum_fixed-2024-2-21-15-54-49.md
new file mode 100644
index 0000000000..df0c8ba8fc
--- /dev/null
+++ b/.chronus/changes/enum_fixed-2024-2-21-15-54-49.md
@@ -0,0 +1,7 @@
+---
+changeKind: breaking
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+enums are always fixed after we switch to use union to represent extensible enum
\ No newline at end of file
diff --git a/.chronus/changes/fix-no-enum-code-fix-include-name-2024-2-22-8-14-39.md b/.chronus/changes/fix-no-enum-code-fix-include-name-2024-2-22-8-14-39.md
new file mode 100644
index 0000000000..9dc60cae6e
--- /dev/null
+++ b/.chronus/changes/fix-no-enum-code-fix-include-name-2024-2-22-8-14-39.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+`no-enum` rule codefix now convert to named variant when the enum had not values (e.g. `enum E {a, b}`)
\ No newline at end of file
diff --git a/.chronus/changes/lintdiff-EnablePostRule-2024-2-21-19-18-34.md b/.chronus/changes/lintdiff-EnablePostRule-2024-2-21-19-18-34.md
new file mode 100644
index 0000000000..1b68e37a8f
--- /dev/null
+++ b/.chronus/changes/lintdiff-EnablePostRule-2024-2-21-19-18-34.md
@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@azure-tools/typespec-azure-resource-manager"
+---
+
+Ensure `arm-post-response-codes` rule is in the default ruleset.
diff --git a/.chronus/changes/remove-projected-name-property-naming-rule-2024-2-21-15-32-12.md b/.chronus/changes/remove-projected-name-property-naming-rule-2024-2-21-15-32-12.md
new file mode 100644
index 0000000000..5ffa4c3623
--- /dev/null
+++ b/.chronus/changes/remove-projected-name-property-naming-rule-2024-2-21-15-32-12.md
@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+Update `property-name-conflict` linter rule to stop looking and recommending `@projectedName` in favor of `@clientName`
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 1cf4891e0f..60a9b0a98d 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -1,4 +1,4 @@
-* @bterlson @daviwil @markcowl @allenjzhang @timotheeguerin
+* @bterlson @markcowl @allenjzhang @timotheeguerin
 
 /packages/typespec-client-generator-core @lmazuel @m-nash @iscai-msft @srnagar @joheredi
 
diff --git a/core b/core
index 68cd9fe906..4e6f137c65 160000
--- a/core
+++ b/core
@@ -1 +1 @@
-Subproject commit 68cd9fe90681d91a23af2e7cadb5c974657c853d
+Subproject commit 4e6f137c65ba502fce97a64d759a6fdd4230953f
diff --git a/docs/howtos/DataPlane Generation - DPG/04renaming.mdx b/docs/howtos/DataPlane Generation - DPG/04renaming.mdx
index c5611306a5..4a51d7a941 100644
--- a/docs/howtos/DataPlane Generation - DPG/04renaming.mdx	
+++ b/docs/howtos/DataPlane Generation - DPG/04renaming.mdx	
@@ -5,6 +5,11 @@ import TabItem from "@theme/TabItem";
 
 This page documents how to customize names for client generations in DPG. For an overview of the setup, please visit the setup page.
 
+:::note
+The TypeSpec compiler provides an `@encodedName` decorator that allows changing the name of the property for a given serialization format.
+However in Azure we recommend that you define the property name as the value sent on the wire and use the `@clientName` decorator to change the name of the generated property.
+:::
+
 ## Default behaviors
 
 By default, any language code generator will assume the TYPESPEC name is the client. For clarity, generators do not attempt to do any auto-magic rename.
diff --git a/docs/libraries/azure-core/reference/linter.md b/docs/libraries/azure-core/reference/linter.md
index 6fadc45891..ed61acf75c 100644
--- a/docs/libraries/azure-core/reference/linter.md
+++ b/docs/libraries/azure-core/reference/linter.md
@@ -52,7 +52,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-core/no-multiple-discriminator`                                                         | Classes should have at most one discriminator.                                                                                                       |
 | `@azure-tools/typespec-azure-core/no-rest-library-interfaces`                                                        | Resource interfaces from the TypeSpec.Rest.Resource library are incompatible with Azure.Core.                                                        |
 | `@azure-tools/typespec-azure-core/no-unknown`                                                                        | Azure services must not have properties of type `unknown`.                                                                                           |
-| `@azure-tools/typespec-azure-core/property-name-conflict`                                                            | Avoid naming conflicts.                                                                                                                              |
+| `@azure-tools/typespec-azure-core/property-name-conflict`                                                            | Avoid naming conflicts between a property and a model of the same name.                                                                              |
 | `@azure-tools/typespec-azure-core/bad-record-type`                                                                   | Identify bad record definitions.                                                                                                                     |
 | `@azure-tools/typespec-azure-core/documentation-required`                                                            | Require documentation over enums, models, and operations.                                                                                            |
 | `@azure-tools/typespec-azure-core/key-visibility-required`                                                           | Key properties need to have an explicit visibility setting.                                                                                          |
diff --git a/docs/libraries/azure-resource-manager/reference/linter.md b/docs/libraries/azure-resource-manager/reference/linter.md
index 95c7b46f20..ab0a186fc2 100644
--- a/docs/libraries/azure-resource-manager/reference/linter.md
+++ b/docs/libraries/azure-resource-manager/reference/linter.md
@@ -30,6 +30,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-resource-manager/arm-common-types-version`                                                                                          | Specify the ARM common-types version using @armCommonTypesVersion.                 |
 | [`@azure-tools/typespec-azure-resource-manager/arm-delete-operation-response-codes`](/libraries/azure-resource-manager/rules/delete-operation-response-codes.md) | Ensure delete operations have the appropriate status codes.                        |
 | [`@azure-tools/typespec-azure-resource-manager/arm-put-operation-response-codes`](/libraries/azure-resource-manager/rules/put-operation-response-codes.md)       | Ensure put operations have the appropriate status codes.                           |
+| [`@azure-tools/typespec-azure-resource-manager/arm-post-operation-response-codes`](/libraries/azure-resource-manager/rules/post-operation-response-codes.md)     | Ensure post operations have the appropriate status codes.                          |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-action-no-segment`                                                                                    | `@armResourceAction` should not be used with `@segment`.                           |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-duplicate-property`                                                                                   | Warn about duplicate properties in resources.                                      |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-invalid-envelope-property`                                                                            | Check for invalid resource envelope properties.                                    |
diff --git a/packages/typespec-autorest/src/lib.ts b/packages/typespec-autorest/src/lib.ts
index 92c647287d..3a4da17ca0 100644
--- a/packages/typespec-autorest/src/lib.ts
+++ b/packages/typespec-autorest/src/lib.ts
@@ -173,24 +173,6 @@ const EmitterOptionsSchema: JSONSchemaType<AutorestEmitterOptions> = {
 const libDef = {
   name: "@azure-tools/typespec-autorest",
   diagnostics: {
-    "security-service-namespace": {
-      severity: "error",
-      messages: {
-        default: "Cannot add security details to a namespace other than the service namespace.",
-      },
-    },
-    "resource-namespace": {
-      severity: "error",
-      messages: {
-        default: "Resource goes on namespace",
-      },
-    },
-    "missing-path-param": {
-      severity: "error",
-      messages: {
-        default: paramMessage`Path contains parameter ${"param"} but wasn't found in given parameters`,
-      },
-    },
     "duplicate-body-types": {
       severity: "error",
       messages: {
@@ -242,24 +224,6 @@ const libDef = {
         default: paramMessage`Invalid type '${"type"}' for a default value`,
       },
     },
-    "invalid-property-type-for-collection-format": {
-      severity: "error",
-      messages: {
-        default: "The collectionFormat can only be applied to model property with type 'string[]'.",
-      },
-    },
-    "invalid-collection-format": {
-      severity: "error",
-      messages: {
-        default: "The format should be one of 'csv','ssv','tsv','pipes' and 'multi'.",
-      },
-    },
-    "non-recommended-collection-format": {
-      severity: "warning",
-      messages: {
-        default: "The recommendation of collection format are 'csv' and 'multi'.",
-      },
-    },
     "invalid-multi-collection-format": {
       severity: "error",
       messages: {
diff --git a/packages/typespec-azure-core/README.md b/packages/typespec-azure-core/README.md
index 90385d630e..423b8016b0 100644
--- a/packages/typespec-azure-core/README.md
+++ b/packages/typespec-azure-core/README.md
@@ -56,7 +56,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-core/no-multiple-discriminator`                                                                                                 | Classes should have at most one discriminator.                                                                                                       |
 | `@azure-tools/typespec-azure-core/no-rest-library-interfaces`                                                                                                | Resource interfaces from the TypeSpec.Rest.Resource library are incompatible with Azure.Core.                                                        |
 | `@azure-tools/typespec-azure-core/no-unknown`                                                                                                                | Azure services must not have properties of type `unknown`.                                                                                           |
-| `@azure-tools/typespec-azure-core/property-name-conflict`                                                                                                    | Avoid naming conflicts.                                                                                                                              |
+| `@azure-tools/typespec-azure-core/property-name-conflict`                                                                                                    | Avoid naming conflicts between a property and a model of the same name.                                                                              |
 | `@azure-tools/typespec-azure-core/bad-record-type`                                                                                                           | Identify bad record definitions.                                                                                                                     |
 | `@azure-tools/typespec-azure-core/documentation-required`                                                                                                    | Require documentation over enums, models, and operations.                                                                                            |
 | `@azure-tools/typespec-azure-core/key-visibility-required`                                                                                                   | Key properties need to have an explicit visibility setting.                                                                                          |
diff --git a/packages/typespec-azure-core/src/linter.ts b/packages/typespec-azure-core/src/linter.ts
index e93fe4fe7e..898b4a2579 100644
--- a/packages/typespec-azure-core/src/linter.ts
+++ b/packages/typespec-azure-core/src/linter.ts
@@ -110,7 +110,7 @@ export const $linter = defineLinter({
           true,
         [`@azure-tools/typespec-azure-core/${useStandardNames.name}`]: true,
         [`@azure-tools/typespec-azure-core/${friendlyNameRule.name}`]: true,
-        [`@azure-tools/typespec-azure-core/${noEnumRule.name}`]: false,
+        [`@azure-tools/typespec-azure-core/${noEnumRule.name}`]: true,
       },
       extends: ["@typespec/http/all"],
     },
diff --git a/packages/typespec-azure-core/src/rules/no-enum.ts b/packages/typespec-azure-core/src/rules/no-enum.ts
index 6c04206d00..271e02c4eb 100644
--- a/packages/typespec-azure-core/src/rules/no-enum.ts
+++ b/packages/typespec-azure-core/src/rules/no-enum.ts
@@ -23,9 +23,11 @@ export const noEnumRule = createRule({
   create(context) {
     return {
       enum: (en: Enum) => {
-        if (getVersionsForEnum(context.program, en).length > 0) {
+        const [_, versions] = getVersionsForEnum(context.program, en);
+        if (versions !== undefined && versions.getVersions()[0].enumMember.enum === en) {
           return;
         }
+
         context.reportDiagnostic({
           format: { enumName: en.name },
           target: en,
@@ -48,7 +50,7 @@ function createEnumToExtensibleUnionCodeFix(en: Enum): CodeFix {
                 ? node.value.value
                 : `"${node.value.value}"`
             }`
-          : `"${node.id.sv}"`;
+          : `${node.id.sv}: "${node.id.sv}"`;
     }
   }
 
@@ -131,7 +133,7 @@ function getNodeAnnotations(node: Node): string {
   }
 
   for (let i = endOfTrivia; i < node.end; i++) {
-    if (source[i] === " ") {
+    if (source[i] === " " || source[i] === "\n") {
       endOfTrivia = i + 1;
     } else {
       break;
diff --git a/packages/typespec-azure-core/src/rules/property-naming.ts b/packages/typespec-azure-core/src/rules/property-naming.ts
index c8718f8743..563df24af2 100644
--- a/packages/typespec-azure-core/src/rules/property-naming.ts
+++ b/packages/typespec-azure-core/src/rules/property-naming.ts
@@ -1,34 +1,20 @@
-import { ModelProperty, createRule, getProjectedNames, paramMessage } from "@typespec/compiler";
+import { ModelProperty, createRule, paramMessage } from "@typespec/compiler";
 import { isExcludedCoreType } from "./utils.js";
 
 export const propertyNameRule = createRule({
   name: "property-name-conflict",
-  description: "Avoid naming conflicts.",
+  description: "Avoid naming conflicts between a property and a model of the same name.",
   severity: "warning",
   messages: {
-    default: paramMessage`Property '${"propertyName"}' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-    projectedName: paramMessage`Use of @projectedName on property '${"propertyName"}' results in '${"propertyName"}' having the same name as its enclosing type in C#. Please use a different @projectedName value.`,
+    default: paramMessage`Property '${"propertyName"}' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
   },
   create(context) {
     return {
       modelProperty: (property: ModelProperty) => {
         if (isExcludedCoreType(context.program, property)) return;
-        const projectedNames = getProjectedNames(context.program, property);
         const modelName = property.model?.name.toLocaleLowerCase();
         const propertyName = property.name.toLocaleLowerCase();
-        const csharpProjection = projectedNames?.get("csharp")?.toLocaleLowerCase();
-        const clientProjection = projectedNames?.get("client")?.toLocaleLowerCase();
-        if (
-          csharpProjection === modelName || // csharp projection conflicts with model name
-          (clientProjection === modelName && !csharpProjection) // client projection conflicts with model name and there is no csharp projection
-        ) {
-          context.reportDiagnostic({
-            messageId: "projectedName",
-            format: { propertyName: property.name },
-            target: property,
-          });
-        } else if (propertyName === modelName && !(csharpProjection || clientProjection)) {
-          // warning if the property name conflicts with the model name and there is no csharp or client projected name
+        if (propertyName === modelName) {
           context.reportDiagnostic({
             format: { propertyName: property.name },
             target: property,
diff --git a/packages/typespec-azure-core/src/rules/require-docs.ts b/packages/typespec-azure-core/src/rules/require-docs.ts
index 5560111d2d..c2c26e1f9d 100644
--- a/packages/typespec-azure-core/src/rules/require-docs.ts
+++ b/packages/typespec-azure-core/src/rules/require-docs.ts
@@ -12,7 +12,7 @@ export const requireDocumentation = createRule({
   description: "Require documentation over enums, models, and operations.",
   severity: "warning",
   messages: {
-    default: paramMessage`The ${"kind"} named '${"name"}' should have a documentation or description, please use decorator @doc to add it.`,
+    default: paramMessage`The ${"kind"} named '${"name"}' should have a documentation or description, use doc comment /** */ to provide it.`,
   },
   create(context) {
     return {
diff --git a/packages/typespec-azure-core/test/rules/no-enum.test.ts b/packages/typespec-azure-core/test/rules/no-enum.test.ts
index 784a630fc7..a0b5edd07c 100644
--- a/packages/typespec-azure-core/test/rules/no-enum.test.ts
+++ b/packages/typespec-azure-core/test/rules/no-enum.test.ts
@@ -31,6 +31,7 @@ describe("typespec-azure-core: no-enum rule", () => {
         },
       ]);
   });
+
   it("allows the version enum", async () => {
     await tester
       .expect(
@@ -46,6 +47,27 @@ describe("typespec-azure-core: no-enum rule", () => {
       .toBeValid();
   });
 
+  it("emit warning about other enums in versioned service", async () => {
+    await tester
+      .expect(
+        `       
+        @service
+        @versioned(Versions)
+        namespace Foo; 
+        enum Versions {
+          v1, v2
+        }
+
+        enum Bar { a,  b}
+        `
+      )
+      .toEmitDiagnostics([
+        {
+          code: "@azure-tools/typespec-azure-core/no-enum",
+        },
+      ]);
+  });
+
   describe("codefix", () => {
     it("codefix simple enum", async () => {
       await tester
@@ -60,7 +82,31 @@ describe("typespec-azure-core: no-enum rule", () => {
           union PetKind {
             string,
 
-            "cat", "dog",
+            cat: "cat", dog: "dog",
+          }
+        `);
+    });
+
+    it("keeps new lines", async () => {
+      await tester
+        .expect(
+          `        
+          enum PetKind {
+            /** cat doc */
+            cat,
+            /** dog doc */
+            dog
+          }
+          `
+        )
+        .applyCodeFix("enum-to-extensible-union").toEqual(`
+          union PetKind {
+            string,
+
+            /** cat doc */
+            cat: "cat",
+            /** dog doc */
+            dog: "dog",
           }
         `);
     });
@@ -115,14 +161,14 @@ describe("typespec-azure-core: no-enum rule", () => {
             /** cat */
             @doc("cat")
             #suppress "cat"
-            "cat", 
+            cat: "cat", 
             
             // dog
 
             /** dog */
             @doc("dog")
             #suppress "dog"
-            "dog",
+            dog: "dog",
 
             // end
           }
diff --git a/packages/typespec-azure-core/test/rules/prevent-property-name-conflict.test.ts b/packages/typespec-azure-core/test/rules/prevent-property-name-conflict.test.ts
deleted file mode 100644
index 42cf55ff9b..0000000000
--- a/packages/typespec-azure-core/test/rules/prevent-property-name-conflict.test.ts
+++ /dev/null
@@ -1,160 +0,0 @@
-import {
-  BasicTestRunner,
-  LinterRuleTester,
-  createLinterRuleTester,
-} from "@typespec/compiler/testing";
-import { beforeEach, describe, it } from "vitest";
-import { propertyNameRule } from "../../src/rules/property-naming.js";
-import { createAzureCoreTestRunner } from "../test-host.js";
-
-describe("typespec-azure-core: property name conflict", () => {
-  let runner: BasicTestRunner;
-  let tester: LinterRuleTester;
-
-  beforeEach(async () => {
-    runner = await createAzureCoreTestRunner();
-    tester = createLinterRuleTester(runner, propertyNameRule, "@azure-tools/typespec-azure-core");
-  });
-
-  it("emit warning if property name conflicts with model name", async () => {
-    await tester.expect(`model Foo {foo: string}`).toEmitDiagnostics({
-      code: "@azure-tools/typespec-azure-core/property-name-conflict",
-      message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-    });
-  });
-
-  it("is valid if conflict resolved through @projectedName('csharp', ...)", async () => {
-    await tester
-      .expect(
-        `model Foo { 
-      #suppress "deprecated" "for testing"
-      @projectedName("csharp", "bar") foo: string
-    }`
-      )
-      .toBeValid();
-  });
-
-  it("is valid if conflict resolved through @projectedName('client', ...)", async () => {
-    await tester
-      .expect(
-        `model Foo { 
-      #suppress "deprecated" "for testing"
-      @projectedName("client", "bar") foo: string
-    }`
-      )
-      .toBeValid();
-  });
-
-  it("emit warning if conflict not resolved through @projectedName", async () => {
-    await tester
-      .expect(
-        `model Foo { 
-        #suppress "deprecated" "for testing"
-        @projectedName("python", "bar") foo: string }`
-      )
-      .toEmitDiagnostics({
-        code: "@azure-tools/typespec-azure-core/property-name-conflict",
-        message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-      });
-  });
-
-  it("emit warning if @projectedName('client', ...) introduces conflict", async () => {
-    await tester
-      .expect(
-        `model Foo { 
-        #suppress "deprecated" "for testing"
-        @projectedName("client", "foo") bar: string;
-       }`
-      )
-      .toEmitDiagnostics({
-        code: "@azure-tools/typespec-azure-core/property-name-conflict",
-        message: `Use of @projectedName on property 'bar' results in 'bar' having the same name as its enclosing type in C#. Please use a different @projectedName value.`,
-      });
-  });
-
-  it("emit warning if @projectedName('csharp', ...) introduces conflict", async () => {
-    await tester
-      .expect(
-        `model Foo { 
-        #suppress "deprecated" "for testing"
-        @projectedName("csharp", "foo") bar: string;
-      }`
-      )
-      .toEmitDiagnostics({
-        code: "@azure-tools/typespec-azure-core/property-name-conflict",
-        message: `Use of @projectedName on property 'bar' results in 'bar' having the same name as its enclosing type in C#. Please use a different @projectedName value.`,
-      });
-  });
-
-  it("is valid if @projectedName('client', ...) causes conflict but @projectedName('csharp', ...) resolves it", async () => {
-    await tester
-      .expect(
-        `model Foo {
-          #suppress "deprecated" "for testing"
-          @projectedName("client", "foo") @projectedName("csharp", "baz") bar: string;
-        }`
-      )
-      .toBeValid();
-  });
-
-  it("emit warning if @friendlyName would resolve a conflict (friendlyName is ignored)", async () => {
-    await tester.expect(`model Foo { @friendlyName("bar") foo: string }`).toEmitDiagnostics({
-      code: "@azure-tools/typespec-azure-core/property-name-conflict",
-      message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-    });
-  });
-
-  it("is valid if @friendlyName introduces conflict (friendlyName is ignored)", async () => {
-    await tester.expect(`model Foo { @friendlyName("foo") bar: string }`).toBeValid();
-  });
-
-  it("emit warning if property name conflicts with model name when using `is`", async () => {
-    await tester
-      .expect(
-        `
-      model Base {
-        foo: string
-      }
-
-      model Foo is Base {}
-      `
-      )
-      .toEmitDiagnostics({
-        code: "@azure-tools/typespec-azure-core/property-name-conflict",
-        message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-      });
-  });
-
-  it("is valid if inherited property name conflicts with model name", async () => {
-    await tester
-      .expect(
-        `
-      model Base {
-        foo: string
-      }
-
-      model Foo extends Base {}
-      `
-      )
-      .toBeValid();
-  });
-
-  it("emit warning if spread property name conflicts with model name", async () => {
-    await tester
-      .expect(
-        `
-      model Base {
-        foo: string
-      }
-
-      model Foo {
-        ...Base;
-      }
-      `
-      )
-      .toEmitDiagnostics({
-        code: "@azure-tools/typespec-azure-core/property-name-conflict",
-        message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @projectedName decorator to rename the property for C#.`,
-      });
-  });
-});
diff --git a/packages/typespec-azure-core/test/rules/property-name-conflict.test.ts b/packages/typespec-azure-core/test/rules/property-name-conflict.test.ts
new file mode 100644
index 0000000000..bf6b6b15f2
--- /dev/null
+++ b/packages/typespec-azure-core/test/rules/property-name-conflict.test.ts
@@ -0,0 +1,159 @@
+import {
+  BasicTestRunner,
+  LinterRuleTester,
+  createLinterRuleTester,
+} from "@typespec/compiler/testing";
+import { beforeEach, it } from "vitest";
+import { propertyNameRule } from "../../src/rules/property-naming.js";
+import { createAzureCoreTestRunner } from "../test-host.js";
+
+let runner: BasicTestRunner;
+let tester: LinterRuleTester;
+
+beforeEach(async () => {
+  runner = await createAzureCoreTestRunner();
+  tester = createLinterRuleTester(runner, propertyNameRule, "@azure-tools/typespec-azure-core");
+});
+
+it("emit warning if property name conflicts with model name", async () => {
+  await tester.expect(`model Foo {foo: string}`).toEmitDiagnostics({
+    code: "@azure-tools/typespec-azure-core/property-name-conflict",
+    message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
+  });
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip(`is valid if conflict resolved through @clientName("newName", "csharp")`, async () => {
+  await tester
+    .expect(
+      `model Foo { 
+        @clientName("bar", "csharp") foo: string
+       }`
+    )
+    .toBeValid();
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip(`is valid if conflict resolved through @clientName("newName")`, async () => {
+  await tester
+    .expect(
+      `model Foo { 
+        @clientName("bar") foo: string
+      }`
+    )
+    .toBeValid();
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip("emit warning if conflict not resolved through @clientName", async () => {
+  await tester
+    .expect(
+      `model Foo { 
+        @clientName("bar", "python") foo: string 
+      }`
+    )
+    .toEmitDiagnostics({
+      code: "@azure-tools/typespec-azure-core/property-name-conflict",
+      message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
+    });
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip(`emit warning if @clientName("newName") introduces conflict`, async () => {
+  await tester
+    .expect(
+      `model Foo { 
+        @clientName("foo") bar: string;
+       }`
+    )
+    .toEmitDiagnostics({
+      code: "@azure-tools/typespec-azure-core/property-name-conflict",
+      message: `Use of @clientName on property 'bar' results in 'bar' having the same name as its enclosing type in C#. Please use a different @clientName("newName", "csharp") value.`,
+    });
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip(`emit warning if @clientName("newName", "csharp") introduces conflict`, async () => {
+  await tester
+    .expect(
+      `model Foo { 
+        @clientName("foo", "csharp") bar: string;
+      }`
+    )
+    .toEmitDiagnostics({
+      code: "@azure-tools/typespec-azure-core/property-name-conflict",
+      message: `Use of @clientName on property 'bar' results in 'bar' having the same name as its enclosing type in C#. Please use a different @clientName("newName", "csharp") value.`,
+    });
+});
+
+// TODO: reenable when rule is moved to tcgc and can resolve if clientName was set
+it.skip(`is valid if @clientName("newName") causes conflict but @clientName("newName", "csharp") resolves it`, async () => {
+  await tester
+    .expect(
+      `model Foo {
+          @clientName("foo") @"client", ("baz", "csharp") bar: string;
+        }`
+    )
+    .toBeValid();
+});
+
+it("emit warning if @friendlyName would resolve a conflict (friendlyName is ignored)", async () => {
+  await tester.expect(`model Foo { @friendlyName("bar") foo: string }`).toEmitDiagnostics({
+    code: "@azure-tools/typespec-azure-core/property-name-conflict",
+    message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
+  });
+});
+
+it("is valid if @friendlyName introduces conflict (friendlyName is ignored)", async () => {
+  await tester.expect(`model Foo { @friendlyName("foo") bar: string }`).toBeValid();
+});
+
+it("emit warning if property name conflicts with model name when using `is`", async () => {
+  await tester
+    .expect(
+      `
+      model Base {
+        foo: string
+      }
+
+      model Foo is Base {}
+      `
+    )
+    .toEmitDiagnostics({
+      code: "@azure-tools/typespec-azure-core/property-name-conflict",
+      message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
+    });
+});
+
+it("is valid if inherited property name conflicts with model name", async () => {
+  await tester
+    .expect(
+      `
+      model Base {
+        foo: string
+      }
+
+      model Foo extends Base {}
+      `
+    )
+    .toBeValid();
+});
+
+it("emit warning if spread property name conflicts with model name", async () => {
+  await tester
+    .expect(
+      `
+      model Base {
+        foo: string
+      }
+
+      model Foo {
+        ...Base;
+      }
+      `
+    )
+    .toEmitDiagnostics({
+      code: "@azure-tools/typespec-azure-core/property-name-conflict",
+      message: `Property 'foo' having the same name as its enclosing model will cause problems with C# code generation. Consider renaming the property directly or using the @clientName("newName", "csharp") decorator to rename the property for C#.`,
+    });
+});
diff --git a/packages/typespec-azure-core/test/rules/require-docs.test.ts b/packages/typespec-azure-core/test/rules/require-docs.test.ts
index bec13a34f7..6c9c3c48bc 100644
--- a/packages/typespec-azure-core/test/rules/require-docs.test.ts
+++ b/packages/typespec-azure-core/test/rules/require-docs.test.ts
@@ -36,7 +36,7 @@ describe("typespec-azure-core: documentation-required rule", () => {
     it("on model", async () =>
       await checkDocRequired(
         "┆model Foo {}",
-        "The Model named 'Foo' should have a documentation or description, please use decorator @doc to add it."
+        "The Model named 'Foo' should have a documentation or description, use doc comment /** */ to provide it."
       ));
 
     it("on model property", async () =>
@@ -44,25 +44,25 @@ describe("typespec-azure-core: documentation-required rule", () => {
         `@doc("Abc") model Foo {
           ┆x: string;
         }`,
-        "The ModelProperty named 'x' should have a documentation or description, please use decorator @doc to add it."
+        "The ModelProperty named 'x' should have a documentation or description, use doc comment /** */ to provide it."
       ));
 
     it("on operation", async () =>
       await checkDocRequired(
         `┆op read(): void;`,
-        "The Operation named 'read' should have a documentation or description, please use decorator @doc to add it."
+        "The Operation named 'read' should have a documentation or description, use doc comment /** */ to provide it."
       ));
 
     it("on property", async () =>
       await checkDocRequired(
         `@doc("op doc") op read(┆param1: string): void;`,
-        "The ModelProperty named 'param1' should have a documentation or description, please use decorator @doc to add it."
+        "The ModelProperty named 'param1' should have a documentation or description, use doc comment /** */ to provide it."
       ));
 
     it("on enum", async () => {
       await checkDocRequired(
         "┆enum Foo {}",
-        "The Enum named 'Foo' should have a documentation or description, please use decorator @doc to add it."
+        "The Enum named 'Foo' should have a documentation or description, use doc comment /** */ to provide it."
       );
     });
 
@@ -71,7 +71,7 @@ describe("typespec-azure-core: documentation-required rule", () => {
         `@doc(".") enum Foo {
           ┆Bar,
         }`,
-        "The EnumMember named 'Bar' should have a documentation or description, please use decorator @doc to add it."
+        "The EnumMember named 'Bar' should have a documentation or description, use doc comment /** */ to provide it."
       );
     });
   });
diff --git a/packages/typespec-azure-resource-manager/README.md b/packages/typespec-azure-resource-manager/README.md
index 8a1aa1b87b..0de0314c4d 100644
--- a/packages/typespec-azure-resource-manager/README.md
+++ b/packages/typespec-azure-resource-manager/README.md
@@ -34,6 +34,7 @@ Available ruleSets:
 | `@azure-tools/typespec-azure-resource-manager/arm-common-types-version`                                                                                                                                  | Specify the ARM common-types version using @armCommonTypesVersion.                 |
 | [`@azure-tools/typespec-azure-resource-manager/arm-delete-operation-response-codes`](https://azure.github.io/typespec-azure/docs/libraries/azure-resource-manager/rules/delete-operation-response-codes) | Ensure delete operations have the appropriate status codes.                        |
 | [`@azure-tools/typespec-azure-resource-manager/arm-put-operation-response-codes`](https://azure.github.io/typespec-azure/docs/libraries/azure-resource-manager/rules/put-operation-response-codes)       | Ensure put operations have the appropriate status codes.                           |
+| [`@azure-tools/typespec-azure-resource-manager/arm-post-operation-response-codes`](https://azure.github.io/typespec-azure/docs/libraries/azure-resource-manager/rules/post-operation-response-codes)     | Ensure post operations have the appropriate status codes.                          |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-action-no-segment`                                                                                                                            | `@armResourceAction` should not be used with `@segment`.                           |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-duplicate-property`                                                                                                                           | Warn about duplicate properties in resources.                                      |
 | `@azure-tools/typespec-azure-resource-manager/arm-resource-invalid-envelope-property`                                                                                                                    | Check for invalid resource envelope properties.                                    |
diff --git a/packages/typespec-azure-resource-manager/src/linter.ts b/packages/typespec-azure-resource-manager/src/linter.ts
index b1e7b3b821..f9ccdb9447 100644
--- a/packages/typespec-azure-resource-manager/src/linter.ts
+++ b/packages/typespec-azure-resource-manager/src/linter.ts
@@ -2,6 +2,7 @@ import { defineLinter } from "@typespec/compiler";
 import { armCommonTypesVersionRule } from "./rules/arm-common-types-version.js";
 import { armDeleteResponseCodesRule } from "./rules/arm-delete-response-codes.js";
 import { armNoRecordRule } from "./rules/arm-no-record.js";
+import { armPostResponseCodesRule } from "./rules/arm-post-response-codes.js";
 import { armPutResponseCodesRule } from "./rules/arm-put-response-codes.js";
 import { armResourceActionNoSegmentRule } from "./rules/arm-resource-action-no-segment.js";
 import { armResourceDuplicatePropertiesRule } from "./rules/arm-resource-duplicate-property.js";
@@ -32,6 +33,7 @@ const rules = [
   armCommonTypesVersionRule,
   armDeleteResponseCodesRule,
   armPutResponseCodesRule,
+  armPostResponseCodesRule,
   armResourceActionNoSegmentRule,
   armResourceDuplicatePropertiesRule,
   armResourceEnvelopeProperties,
diff --git a/packages/typespec-client-generator-core/src/types.ts b/packages/typespec-client-generator-core/src/types.ts
index 4f9b6aca8d..2b4e79de10 100644
--- a/packages/typespec-client-generator-core/src/types.ts
+++ b/packages/typespec-client-generator-core/src/types.ts
@@ -1,9 +1,4 @@
-import {
-  UnionEnum,
-  getLroMetadata,
-  getUnionAsEnum,
-  isFixed,
-} from "@azure-tools/typespec-azure-core";
+import { UnionEnum, getLroMetadata, getUnionAsEnum } from "@azure-tools/typespec-azure-core";
 import {
   BooleanLiteral,
   BytesKnownEncoding,
@@ -647,7 +642,7 @@ export function getSdkEnum(context: TCGCContext, type: Enum, operation?: Operati
       details: docWrapper.details,
       valueType: getSdkEnumValueType(context, type.members.values()),
       values: [],
-      isFixed: isFixed(context.program, type),
+      isFixed: true, // enums are always fixed after we switch to use union to represent extensible enum
       isFlags: false,
       usage: UsageFlags.None, // We will add usage as we loop through the operations
       access: undefined, // Dummy value until we update models map
diff --git a/packages/typespec-client-generator-core/test/types.test.ts b/packages/typespec-client-generator-core/test/types.test.ts
index adade352eb..4de3a6fe6e 100644
--- a/packages/typespec-client-generator-core/test/types.test.ts
+++ b/packages/typespec-client-generator-core/test/types.test.ts
@@ -805,7 +805,7 @@ describe("typespec-client-generator-core: types", () => {
       strictEqual(runner.context.experimental_sdkPackage.models.length, 1);
       strictEqual(runner.context.experimental_sdkPackage.enums.length, 1);
       const sdkType = runner.context.experimental_sdkPackage.enums[0];
-      strictEqual(sdkType.isFixed, false);
+      strictEqual(sdkType.isFixed, true);
       strictEqual(sdkType.name, "DaysOfWeekExtensibleEnum");
       strictEqual(sdkType.valueType.kind, "string");
       strictEqual(sdkType.usage & UsageFlags.Versioning, 0); // not a versioning enum
@@ -856,7 +856,7 @@ describe("typespec-client-generator-core: types", () => {
       strictEqual(runner.context.experimental_sdkPackage.models.length, 1);
       strictEqual(runner.context.experimental_sdkPackage.enums.length, 1);
       const sdkType = runner.context.experimental_sdkPackage.enums[0];
-      strictEqual(sdkType.isFixed, false);
+      strictEqual(sdkType.isFixed, true);
       strictEqual(sdkType.name, "Integers");
       strictEqual(sdkType.valueType.kind, "int32");
       const values = sdkType.values;
@@ -890,7 +890,7 @@ describe("typespec-client-generator-core: types", () => {
 
       const sdkType = runner.context.experimental_sdkPackage.enums[0];
       ok(sdkType);
-      strictEqual(sdkType.isFixed, false);
+      strictEqual(sdkType.isFixed, true);
       strictEqual(sdkType.name, "Floats");
       strictEqual(sdkType.valueType.kind, "float32");
       const values = sdkType.values;