max_tokens parameter is no longer supported for gpt-5/chat completion

Description

If we call gpt-5 using a chat completion API (OpenAIChatLanguageModel), we'll hit AI_APICallError: Unsupported parameter: 'max_tokens' is not supported with this model. Use 'max_completion_tokens' instead.

This is because

ai/packages/openai/src/openai-chat-language-model.ts

Line 145 in 58fff3f

max_tokens: maxOutputTokens,

is still setting the deprecated max_tokens instead of max_completion_tokens.

Note that this can be solved by https://github.com/vercel/ai/pull/7848/files since we do override this param for reasoning models.

AI SDK Version

No response

+1

yeah we're hitting this too

+1

should be resolved for ai sdk 4 in openai provider 1.3.34

@lgrammel

@lgrammel this is still throwing error with latest version : ` "@ai-sdk/openai-compatible": "^2.0.13" when used with AI gateway providers.

Do I need to remove the maxOutputTokens? i thought the package automatically handles it and changes to max_completion_tokens for Open AI?

export function getAIGateway(
  apiKey: string,
  gatewayId: string,
) {
  const openAICompatible = createOpenAICompatible({
    name: `cf-openai`,
    baseURL: `${baseURL}/compat`
    apiKey: apiKey,
  });
  return openAICompatible(`openai/${model}`) as unknown as LanguageModel;
}

const model = getAIGateway(apiKey, gatewayId);

const result = streamText({
      model: model,
      messages: messagesArray,
      maxOutputTokens: MAX_TOKEN,
      temperature: TEMP,
    });

fix(openai-compat): add GPT-5 model compatibility

Identify issue type

Identified as Bug
Confidence: High

Rationale

The issue reports a concrete provider incompatibility that causes GPT-5 requests using the existing maxOutputTokens API to fail unexpectedly.

Evidence

Calling GPT-5 through OpenAIChatLanguageModel sends deprecated max_tokens, causing an AI_APICallError that requires max_completion_tokens.
The reporter identifies the provider code that sets the incompatible parameter.
Multiple users reproduced the failure; a maintainer stated it was addressed in OpenAI provider 1.3.34, while a later user reported similar behavior with @ai-sdk/openai-compatible and an AI gateway.

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max_tokens parameter is no longer supported for gpt-5/chat completion #7863

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max_tokens parameter is no longer supported for gpt-5/chat completion #7863

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bardia-pourvakil commented on Aug 8, 2025

thdxr commented on Aug 8, 2025

vjayarag commented on Aug 8, 2025

lgrammel commented on Aug 8, 2025

vickyRathee commented on Jan 16, 2026

lgrammel commented on Jul 22, 2026

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