Hermes 4 405B API

Hermes 4 is a large-scale reasoning model built on Meta-Llama-3.1-405B with hybrid reasoning mode. It can choose to deliberate internally with <think>...</think> traces or respond directly, offering flexibility between speed and depth. Supports structured outputs, JSON mode, function calling, and tool use.
Context
131K tokens
Input
$1.3 / 1M
Output
$3.9 / 1M
Released
Oct 2, 2025

How to use Hermes 4 405B API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to nousresearch/hermes-4-405b.
import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "nousresearch/hermes-4-405b",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "nousresearch/hermes-4-405b",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/chat/completions \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"nousresearch/hermes-4-405b","messages":[{"role":"user","content":"Hello!"}]}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.

Hermes 4 405B API Pricing

TypePrice
Input
$1.3 / 1M tokens
Output
$3.9 / 1M tokens

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