«model_not_found» error: «The model … does not exist or you do not have access to it»

gpt-4 OpenAI

Shutdown date: 23 October 2026

Official replacement: gpt-5.6-sol

Price per million tokens (input / output): $30 / $60 → $4 / $20

What changes in your code

• Change the name in model. If it lives in an environment variable or in an n8n, Make or Zapier setting, change it there.
• The new models reason by default (medium): slower and more tokens. To answer like the old one, set reasoning_effort: "none" in Chat Completions or reasoning: { effort: "none" } in the Responses API.
• If you send temperature, top_p or logprobs, keep reasoning at none: at any other level the API rejects them (per the GPT-5.4 and GPT-6 guides).
• max_tokens is deprecated: use max_completion_tokens (or max_output_tokens in Responses). With reasoning on, that limit is spent on reasoning too: leave room.
• Function calling in Chat Completions only works with reasoning_effort: "none". To reason and call tools together, move to the Responses API.
• The new models don’t support the old /v1/completions endpoint or fine-tuning (each model’s page says so).

from openai import OpenAI
client = OpenAI()  # reads OPENAI_API_KEY from the environment

resp = client.chat.completions.create(
    model="gpt-5.6-sol",              # was: "gpt-4"
    reasoning_effort="none",    # answers like the old one, no reasoning
    max_completion_tokens=500,  # was: max_tokens=500
    messages=[{"role": "user", "content": "Hello"}],
)
print(resp.choices[0].message.content)

import OpenAI from "openai";
const client = new OpenAI(); // reads OPENAI_API_KEY from the environment

const resp = await client.chat.completions.create({
  model: "gpt-5.6-sol",             // was: "gpt-4"
  reasoning_effort: "none",   // answers like the old one, no reasoning
  max_completion_tokens: 500, // was: max_tokens: 500
  messages: [{ role: "user", content: "Hello" }],
});
console.log(resp.choices[0].message.content);

Sources: OpenAI · Deprecations · Upgrading to GPT-5.6 · Using GPT-6 · Chat Completions API

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