Bug: Perplexity Reasoning cant Parse JSON Object

[1elasmarjad]

Description

When I use the perplexity/sonar-reasoning-pro model or any Perplexity reasoning model via the Vercel API Gateway and try to generate an object:

the response content from Perplexity seems to not be properly handled, and as such the object fails to be parsed.

Here's the error:

Error message: Unexpected token '<', "<think>
Le"... is not valid JSON

cause: [SyntaxError: Unexpected token '<', "<think>
Le"... is not valid JSON],

Here's the output text (most of the thinking was omitted):

'<think>\n' +
    'Let me analyze the task carefully. I need to:\n' +
    '\n' +
    "1. Go to company websites' careers/jobs pages\n" +
'</think>\n' +
    '\n' +
    `{"valid": false, "reasons": ["omitted"]}`,

Here's how I'm trying to generate the object:

import { generateText, Output } from "ai";
import { z } from "zod";

 const result = await generateText({
      model: "perplexity/sonar-reasoning-pro",
      system: config.systemPrompt,
      prompt: `Evaluate this company: "${companyName}."`,
      output: Output.object({
        schema: z.object({
          valid: z
            .boolean(),
          reasons: z
            .array(z.string())
            .nullable(),
        }),
      }),
    });

console.log(result.output);

AI SDK Version

• ai: 6.0.5

Code of Conduct

• I agree to follow this project's Code of Conduct

[aayush-kapoor]

you will need to use the middleware we have to extract the reasoning tags:

import { wrapLanguageModel, generateText, Output, gateway, extractReasoningMiddleware } from 'ai';
import { z } from 'zod';
import { run } from '../lib/run';

run(async () => {
  const result = await generateText({
    model: wrapLanguageModel({
      model: gateway('perplexity/sonar-reasoning-pro'),
      middleware: extractReasoningMiddleware({ tagName: 'think' }), // middleware function
    }),
    system: 'You are a helpful assistant that evaluates companies.',
    prompt: `Evaluate this company: "Vercel"`,
    output: Output.object({
      schema: z.object({
        valid: z.boolean(),
        reasons: z.array(z.string()).nullable(),
      }),
    }),
  });

  console.log(result.output);
});

i was able to reproduce the issue and resolve it by doing this

[aayush-kapoor]

markign this as closed but feel free to reopen if still encountered