fix(providers): respect responses developer-role compat (#60385)

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

@@ -1,6 +1,7 @@
 import type { Model } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
 import {
+  buildOpenAIResponsesParams,
   buildTransportAwareSimpleStreamFn,
   isTransportAwareApiSupported,
   parseTransportChunkUsage,
@@ -253,4 +254,54 @@ describe("openai transport stream", () => {
       },
     });
   });
+
+  it("uses system role instead of developer for responses providers that disable developer role", () => {
+    const params = buildOpenAIResponsesParams(
+      {
+        id: "grok-4.1-fast",
+        name: "Grok 4.1 Fast",
+        api: "openai-responses",
+        provider: "xai",
+        baseUrl: "https://api.x.ai/v1",
+        reasoning: true,
+        input: ["text"],
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+        contextWindow: 200000,
+        maxTokens: 8192,
+      } satisfies Model<"openai-responses">,
+      {
+        systemPrompt: "system",
+        messages: [],
+        tools: [],
+      } as never,
+      undefined,
+    ) as { input?: Array<{ role?: string }> };
+
+    expect(params.input?.[0]).toMatchObject({ role: "system" });
+  });
+
+  it("keeps developer role for native OpenAI reasoning responses models", () => {
+    const params = buildOpenAIResponsesParams(
+      {
+        id: "gpt-5",
+        name: "GPT-5",
+        api: "openai-responses",
+        provider: "openai",
+        baseUrl: "https://api.openai.com/v1",
+        reasoning: true,
+        input: ["text"],
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+        contextWindow: 200000,
+        maxTokens: 8192,
+      } satisfies Model<"openai-responses">,
+      {
+        systemPrompt: "system",
+        messages: [],
+        tools: [],
+      } as never,
+      undefined,
+    ) as { input?: Array<{ role?: string }> };
+
+    expect(params.input?.[0]).toMatchObject({ role: "developer" });
+  });
 });

src/agents/openai-transport-stream.ts

@@ -345,7 +345,7 @@ function convertResponsesMessages(
   model: Model<Api>,
   context: Context,
   allowedToolCallProviders: Set<string>,
-  options?: { includeSystemPrompt?: boolean },
+  options?: { includeSystemPrompt?: boolean; supportsDeveloperRole?: boolean },
 ) {
   const messages: unknown[] = [];
   const normalizeIdPart = (part: string) => {
@@ -383,7 +383,7 @@ function convertResponsesMessages(
   const includeSystemPrompt = options?.includeSystemPrompt ?? true;
   if (includeSystemPrompt && context.systemPrompt) {
     messages.push({
-      role: model.reasoning ? "developer" : "system",
+      role: model.reasoning && options?.supportsDeveloperRole !== false ? "developer" : "system",
       content: sanitizeTransportPayloadText(context.systemPrompt),
     });
   }
@@ -952,15 +952,17 @@ function getPromptCacheRetention(
   return baseUrl?.includes("api.openai.com") ? "24h" : undefined;
 }
 
-function buildOpenAIResponsesParams(
+export function buildOpenAIResponsesParams(
   model: Model<Api>,
   context: Context,
   options: OpenAIResponsesOptions | undefined,
 ) {
+  const compat = getCompat(model as OpenAIModeModel);
   const messages = convertResponsesMessages(
     model,
     context,
     new Set(["openai", "openai-codex", "opencode", "azure-openai-responses"]),
+    { supportsDeveloperRole: compat.supportsDeveloperRole },
   );
   const cacheRetention = resolveCacheRetention(options?.cacheRetention);
   const params: Record<string, unknown> = {