fix(providers): keep native modelstudio streaming usage compat

src/agents/openai-completions-compat.ts

@@ -4,6 +4,7 @@ type OpenAICompletionsCompatDefaultsInput = {
   provider?: string;
   endpointClass: ProviderEndpointClass;
   knownProviderFamily: string;
+  supportsNativeStreamingUsageCompat?: boolean;
   usesExplicitProxyLikeEndpoint?: boolean;
 };
 
@@ -22,7 +23,12 @@ function isDefaultRouteProvider(provider: string | undefined, ...ids: string[])
 export function resolveOpenAICompletionsCompatDefaults(
   input: OpenAICompletionsCompatDefaultsInput,
 ): OpenAICompletionsCompatDefaults {
-  const { endpointClass, knownProviderFamily, usesExplicitProxyLikeEndpoint = false } = input;
+  const {
+    endpointClass,
+    knownProviderFamily,
+    supportsNativeStreamingUsageCompat = false,
+    usesExplicitProxyLikeEndpoint = false,
+  } = input;
   const isDefaultRoute = endpointClass === "default";
   const usesConfiguredNonOpenAIEndpoint =
     endpointClass !== "default" && endpointClass !== "openai-public";
@@ -54,7 +60,8 @@ export function resolveOpenAICompletionsCompatDefaults(
       knownProviderFamily !== "mistral" &&
       endpointClass !== "xai-native" &&
       !usesExplicitProxyLikeEndpoint,
-    supportsUsageInStreaming: !isNonStandard && !usesConfiguredNonOpenAIEndpoint,
+    supportsUsageInStreaming:
+      !isNonStandard && (!usesConfiguredNonOpenAIEndpoint || supportsNativeStreamingUsageCompat),
     supportsStrictMode: !isZai && !usesConfiguredNonOpenAIEndpoint,
   };
 }
@@ -62,7 +69,10 @@ export function resolveOpenAICompletionsCompatDefaults(
 export function resolveOpenAICompletionsCompatDefaultsFromCapabilities(
   input: Pick<
     ProviderRequestCapabilities,
-    "endpointClass" | "knownProviderFamily" | "usesExplicitProxyLikeEndpoint"
+    | "endpointClass"
+    | "knownProviderFamily"
+    | "supportsNativeStreamingUsageCompat"
+    | "usesExplicitProxyLikeEndpoint"
   > & {
     provider?: string;
   },

src/agents/openai-transport-stream.test.ts

@@ -356,13 +356,13 @@ describe("openai transport stream", () => {
     expect(params.messages?.[0]).toMatchObject({ role: "system" });
   });
 
-  it("uses system role for ModelStudio-hosted completions providers", () => {
+  it("uses system role and streaming usage compat for native ModelStudio completions providers", () => {
     const params = buildOpenAICompletionsParams(
       {
         id: "qwen3.6-plus",
         name: "Qwen 3.6 Plus",
         api: "openai-completions",
-        provider: "custom-qwen",
+        provider: "modelstudio",
         baseUrl: "https://dashscope-intl.aliyuncs.com/compatible-mode/v1",
         reasoning: true,
         input: ["text"],
@@ -376,9 +376,13 @@ describe("openai transport stream", () => {
         tools: [],
       } as never,
       undefined,
-    ) as { messages?: Array<{ role?: string }> };
+    ) as {
+      messages?: Array<{ role?: string }>;
+      stream_options?: { include_usage?: boolean };
+    };
 
     expect(params.messages?.[0]).toMatchObject({ role: "system" });
+    expect(params.stream_options).toMatchObject({ include_usage: true });
   });
 
   it("disables developer-role-only compat defaults for configured custom proxy completions providers", () => {