Move legacy API version override to Azure Core

.chronus/changes/autorest-client-api-version-override-2026-08-04-13-00-00.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-autorest"
+---
+
+Honor inherited Azure Core API-version overrides in emitted OpenAPI documents and warn when a document has inconsistent overrides.

.chronus/changes/feature-file-client-version-2026-08-04-13-00-00.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-azure-resource-manager"
+---
+
+Add a `version` option to `@featureFileOptions` for overriding the generated client API version.

.chronus/changes/go-client-api-version-override-2026-08-04-13-00-00.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-go"
+---
+
+Generate Go clients with the opaque API-version default configured for each client.

.chronus/changes/override-api-version-azure-core-2026-08-06-13-29-45.md

@@ -0,0 +1,15 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-azure-core"
+---
+
+Add the legacy `@Azure.Core.Legacy.overrideApiVersion` decorator for overriding inherited and
+optionally language-scoped API-version wire defaults on namespaces and interfaces.
+
+```typespec
+@Azure.Core.Legacy.overrideApiVersion("2021-11-01")
+interface Widgets {
+  get(): void;
+}
+```

.chronus/changes/override-client-api-version-tcgc-2026-08-04-13-00-00.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-client-generator-core"
+---
+
+Populate per-client API-version defaults from `Azure.Core.Legacy.overrideApiVersion` for downstream emitters.

.chronus/changes/typescript-client-api-version-override-2026-08-04-13-00-00.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@azure-tools/typespec-ts"
+---
+
+Generate TypeScript clients with the opaque API-version default configured for each client.

packages/typespec-autorest/src/lib.ts

@@ -464,6 +464,12 @@ export const $lib = createTypeSpecLibrary({
           "Cannot emit service.yaml because the project defines multiple services. Only the first service will be included.",
       },
     },
+    "inconsistent-client-api-version-override": {
+      severity: "warning",
+      messages: {
+        default: paramMessage`Operations emitted to the same OpenAPI document must specify one consistent \`@overrideApiVersion\` value. Found values: ${"values"}. The normal document version ${"fallback"} will be retained.`,
+      },
+    },
   },
   emitter: {
     options: EmitterOptionsSchema as JSONSchemaType<AutorestEmitterOptions>,

packages/typespec-autorest/src/openapi.ts

@@ -5,12 +5,13 @@ import {
   extractLroStates,
   getArmResourceIdentifierConfig,
   getAsEmbeddingVector,
+  getEffectiveApiVersionOverride,
   getLroMetadata,
   getUnionAsEnum,
   hasUniqueItems,
 } from "@azure-tools/typespec-azure-core";
 import {
-  type ArmFeatureOptions,
+  type ArmFeatureFileOptions,
   getArmCommonTypeOpenAPIRef,
   getArmIdentifiers,
   getArmKeyIdentifiers,
@@ -3035,6 +3036,7 @@ export function createDefaultDocumentProxy(
   const definitions = new Map<string, OpenAPI2Schema>();
   const parameters: Map<string, [ModelProperty, OpenAPI2Parameter]> = new Map();
   const operationIds = new DuplicateTracker<string, Operation>();
+  const operations: HttpOperation[] = [];
   let examples: Map<string, Record<string, LoadedExample>> = new Map();
   let operationIdsWithExamples: Set<string> = new Set();
   return {
@@ -3066,6 +3068,7 @@ export function createDefaultDocumentProxy(
     },
 
     createOrGetEndpoint(op: HttpOperation, context: AutorestEmitterContext): OpenAPI2Operation {
+      operations.push(op);
       const pathItem = initPathItem(program, op, root);
       if (!pathItem[op.verb]) {
         pathItem[op.verb] = { parameters: [] };
@@ -3109,6 +3112,7 @@ export function createDefaultDocumentProxy(
     },
     resolveDocuments(context: AutorestEmitterContext) {
       reportDuplicateOperationIds(program, operationIds);
+      applyClientApiVersionOverride(root, operations, context, service.type);
       root.definitions = {};
       for (const [name, schema] of definitions) {
         root.definitions[name] = schema;
@@ -3158,8 +3162,9 @@ export function createDefaultDocumentProxy(
 interface OpenAPI2DocumentItem {
   document: OpenAPI2Document;
   operationExamples: Map<string, LoadedExample[]>;
+  operations: HttpOperation[];
   tags: Set<string>;
-  options: ArmFeatureOptions;
+  options: ArmFeatureFileOptions;
 }
 
 function createFeatureDocumentProxy(
@@ -3221,6 +3226,7 @@ function createFeatureDocumentProxy(
     createOrGetEndpoint(op: HttpOperation, context: AutorestEmitterContext): OpenAPI2Operation {
       const options = getFeature(program, op.operation);
       const item = root.get(options.featureName.toLowerCase())!;
+      item.operations.push(op);
       const pathItem = initPathItem(program, op, item.document);
       if (!pathItem[op.verb]) {
         pathItem[op.verb] = { parameters: [] };
@@ -3281,6 +3287,13 @@ function createFeatureDocumentProxy(
         reportDuplicateOperationIds(program, tracker);
       }
       for (const [featureName, featureItem] of root.entries()) {
+        applyClientApiVersionOverride(
+          featureItem.document,
+          featureItem.operations,
+          context,
+          service.type,
+          featureItem.options.version,
+        );
         const exampleIds = operationFeatures.get(featureName) || new Set<string>();
         const featureExamples = [...exampleIds]
           .filter((id) => operationIdsWithExamples.has(id))
@@ -3377,17 +3390,57 @@ function reportDuplicateOperationIds(
 function initializeOpenAPIDocumentItem(
   program: Program,
   service: Service,
-  options: ArmFeatureOptions,
+  options: ArmFeatureFileOptions,
   version?: string,
 ): OpenAPI2DocumentItem {
   return {
     document: initializeOpenApi2Document(program, service, version),
     operationExamples: new Map<string, LoadedExample[]>(),
+    operations: [],
     tags: new Set<string>(),
     options,
   };
 }
 
+function applyClientApiVersionOverride(
+  document: OpenAPI2Document,
+  operations: HttpOperation[],
+  context: AutorestEmitterContext,
+  diagnosticTarget: Namespace,
+  explicitVersion?: string,
+): void {
+  if (explicitVersion !== undefined) {
+    document.info.version = explicitVersion;
+    return;
+  }
+  if (operations.length === 0) return;
+
+  const overrides = operations.map((operation) =>
+    getEffectiveApiVersionOverride(
+      context.program,
+      operation.operation,
+      "@azure-tools/typespec-autorest",
+    ),
+  );
+  if (overrides.every((value) => value === undefined)) return;
+
+  const first = overrides[0];
+  if (first !== undefined && overrides.every((value) => value === first)) {
+    document.info.version = first;
+    return;
+  }
+
+  const values = [...new Set(overrides.map((value) => value ?? "<none>"))];
+  reportDiagnostic(context.program, {
+    code: "inconsistent-client-api-version-override",
+    format: {
+      values: values.join(", "),
+      fallback: document.info.version,
+    },
+    target: diagnosticTarget,
+  });
+}
+
 function initializeOpenApi2Document(
   program: Program,
   service: Service,