vercel/ai · error

Model could not be resolved

Error message

Model could not be resolved

What it means

generateSpeech resolves the provided model via resolveSpeechModel; if the value cannot be resolved to a speech-capable model (e.g. a string id that no provider registry maps to a SpeechModelV*), a plain Error('Model could not be resolved') is thrown before any network request. It guards against calling the speech API with an unusable model value.

Source

Thrown at packages/ai/src/generate-speech/generate-speech.ts:121

   *
   * @default 2
   */
  maxRetries?: number;

  /**
   * Abort signal.
   */
  abortSignal?: AbortSignal;

  /**
   * Additional headers to include in the request.
   * Only applicable for HTTP-based providers.
   */
  headers?: Record<string, string>;
}): Promise<SpeechResult> {
  const resolvedModel = resolveSpeechModel(model);
  if (!resolvedModel) {
    throw new Error('Model could not be resolved');
  }

  const headersWithUserAgent = withUserAgentSuffix(
    headers ?? {},
    `ai/${VERSION}`,
  );

  const { retry } = prepareRetries({
    maxRetries: maxRetriesArg,
    abortSignal,
  });

  const result = await retry(() =>
    resolvedModel.doGenerate({
      text,
      voice,
      outputFormat,
      instructions,

View on GitHub (pinned to 69428b1f8b)

Solutions

1. Pass an explicit speech model instance, e.g. openai.speech('tts-1') or openai('tts-1') from the provider's speech factory
2. Check that the variable passed as `model` is actually a speech model, not another model type
3. If passing a string, ensure a default speech model/provider is configured for resolution
4. Log/inspect the model value just before the call to catch null/undefined

Example fix

// before
await generateSpeech({ model: 'tts-1', text });
// after
import { createOpenAI } from '@ai-sdk/openai';
const openai = createOpenAI();
await generateSpeech({ model: openai.speech('tts-1'), text });

import { isSpeechModel } from 'ai'; // or check provider shape
if (model == null || typeof model !== 'object' || !('modelId' in model)) {
  throw new Error('A speech model instance is required');
}

function isSpeechModel(m: unknown): m is SpeechModel {
  return m != null && typeof m === 'object' && 'doGenerate' in m && 'modelId' in m;
}

try {
  return await generateSpeech({ model, text });
} catch (e) {
  if (e instanceof Error && e.message === 'Model could not be resolved') {
    throw new Error('Pass a provider speech model, e.g. openai.speech("tts-1")');
  }
  throw e;
}

When it happens

Trigger: Passing null/undefined as `model`; passing a plain string model id with no default speech provider configured; passing a language/embedding/image model object instead of a SpeechModel; passing an object that fails resolveSpeechModel's shape checks.

Common situations: Reading the model id from env/config and forgetting to call provider(modelId); refactors after provider upgrades where the speech model factory moved; typos in provider instantiation like openai('tts-1') assigned to the wrong variable.

Related errors

• Deepgram speech model "${this.modelId}" requires a `voice` t
• Invalid argument for parameter model: model ${model.provider
• Unsupported output: ${_exhaustiveCheck}
• Invalid argument for parameter output: Invalid output type.
• No speech audio generated.

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/21f328fc86f46e13. Report an issue: GitHub.