fix(groq): pass through reasoning effort (#42166)

Co-authored-by: Aiden Cline <rekram1-node@users.noreply.github.com>

packages/core/test/provider-groq.test.ts

@@ -0,0 +1,28 @@
+import { createGroq } from "@ai-sdk/groq"
+import { expect, test } from "bun:test"
+
+test("Groq passes through unknown reasoning effort", async () => {
+  let body: Record<string, unknown> | undefined
+  const mockFetch = Object.assign(
+    async (_input: Parameters<typeof fetch>[0], init?: RequestInit) => {
+      body = JSON.parse(String(init?.body))
+      return Response.json({
+        id: "response-1",
+        created: 0,
+        model: "openai/gpt-oss-120b",
+        object: "chat.completion",
+        choices: [{ index: 0, message: { role: "assistant", content: "Hello" }, finish_reason: "stop" }],
+        usage: { prompt_tokens: 1, completion_tokens: 1, total_tokens: 2 },
+      })
+    },
+    { preconnect: fetch.preconnect },
+  )
+  const model = createGroq({ apiKey: "test", fetch: mockFetch })("openai/gpt-oss-120b")
+
+  await model.doGenerate({
+    prompt: [{ role: "user", content: [{ type: "text", text: "Hello" }] }],
+    providerOptions: { groq: { reasoningEffort: "custom" } },
+  })
+
+  expect(body?.reasoning_effort).toBe("custom")
+})