vercel/ai · error · NoObjectGeneratedError

No object generated: could not parse the response.

Error message

No object generated: could not parse the response.

What it means

NoObjectGeneratedError thrown by the object output parser when safeParseJSON fails on the model's complete text response — the response text is not valid JSON. The SDK throws with the raw text, response metadata, usage and finishReason attached for debugging.

Source

Thrown at packages/ai/src/generate-text/output.ts:133

    responseFormat: resolve(schema.jsonSchema).then(jsonSchema => ({
      type: 'json' as const,
      schema: jsonSchema,
      ...(name != null && { name }),
      ...(description != null && { description }),
    })),

    async parseCompleteOutput(
      { text }: { text: string },
      context: {
        response: LanguageModelResponseMetadata;
        usage: LanguageModelUsage;
        finishReason: FinishReason;
      },
    ) {
      const parseResult = await safeParseJSON({ text });

      if (!parseResult.success) {
        throw new NoObjectGeneratedError({
          message: 'No object generated: could not parse the response.',
          cause: parseResult.error,
          text,
          response: context.response,
          usage: context.usage,
          finishReason: context.finishReason,
        });
      }

      const validationResult = await safeValidateTypes({
        value: parseResult.value,
        schema,
      });

      if (!validationResult.success) {
        throw new NoObjectGeneratedError({
          message: 'No object generated: response did not match schema.',
          cause: validationResult.error,

View on GitHub (pinned to 69428b1f8b)

Solutions

1. Inspect err.text (attached to the error) to see exactly what the model returned.
2. Raise maxOutputTokens so the JSON is not truncated.
3. Add prompt instructions: 'Respond with raw JSON only, no markdown fences or commentary.'
4. Use a provider/mode that supports native structured output instead of text-based JSON extraction.
5. Retry the request; transient truncation can cause invalid JSON.

Example fix

// before
const result = await generateText({ model, experimental_output: Output.object({ schema }) });
// after
const result = await generateText({ model, maxOutputTokens: 2000, experimental_output: Output.object({ schema }), prompt: 'Return only raw JSON matching the schema.' });
try { const obj = result.output; } catch (e) { if (NoObjectGeneratedError.isInstance(e)) console.log(e.text); }

// validate the raw text is JSON before trusting result.output
function isParseableJson(text) {
  if (typeof text !== 'string' || text.length === 0) return false;
  try { JSON.parse(text); return true; } catch { return false; }
}
// usage: if (!isParseableJson(result.text)) retry();

import { NoObjectGeneratedError } from 'ai';
function isNoObjectGenerated(e): e is NoObjectGeneratedError {
  return NoObjectGeneratedError.isInstance(e);
}

try {
  const obj = result.output;
} catch (e) {
  if (NoObjectGeneratedError.isInstance(e)) {
    console.error('Raw model text:', e.text, 'finishReason:', e.finishReason);
    // retry with stricter prompt or repair e.text
  } else throw e;
}

When it happens

Trigger: Using generateText with an object output spec (experimental_output: Output.object) and the model's final text could not be JSON.parse'd (truncated stream, markdown-fenced JSON, prose wrapper, or empty response).

Common situations: Model wraps JSON in ```json fences; maxOutputTokens too low so JSON is truncated; model answers in prose instead of JSON; empty response due to content filter.

Understand the failure class

Background: "Invalid JSON response" and "Failed to parse response" errors: when an API answers 200 but the body isn't the JSON your library expected — this error's family across 28 libraries.

Related errors

• No object generated: could not parse the response.
• No object generated: response did not match schema.
• No object generated: response did not match schema.
• Harness 'claude-code' requires a JSON schema for structured
• Harness 'cline' requires a JSON schema for structured output

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/e08a722cd5c54f27. Report an issue: GitHub.