vercel/ai · error · UnsupportedFunctionalityError

'tool choice type: ${_exhaustiveCheck}' functionality not su

Error message

'tool choice type: ${_exhaustiveCheck}' functionality not supported.

What it means

Error "'tool choice type: ${_exhaustiveCheck}' functionality not supported." thrown in vercel/ai.

Source

Thrown at packages/groq/src/groq-prepare-tools.ts:126

  switch (type) {
    case 'auto':
    case 'none':
    case 'required':
      return { tools: groqTools, toolChoice: type, toolWarnings };
    case 'tool':
      return {
        tools: groqTools,
        toolChoice: {
          type: 'function',
          function: {
            name: toolChoice.toolName,
          },
        },
        toolWarnings,
      };
    default: {
      const _exhaustiveCheck: never = type;
      throw new UnsupportedFunctionalityError({
        functionality: `tool choice type: ${_exhaustiveCheck}`,
      });
    }
  }
}

View on GitHub (pinned to 69428b1f8b)

When it happens

Trigger: Thrown at packages/groq/src/groq-prepare-tools.ts:126 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/5b38fc060e661b30. Report an issue: GitHub.