Hermes 4 405B
About this model
Hermes 4 405B is an AI model from Nous Research, made available through the API on August 26, 2025. It can read up to 131,072 tokens in one request, roughly 246 pages of text, and write up to 117,964 tokens in a single answer.
Through the API it costs $1 per million input tokens and $3 per million output tokens. Its pricing sits in the middle of the market.
It supports extended reasoning: it can "think" step by step before answering, which helps on maths, code and complex questions. Its weights are openly published (NousResearch/Hermes-4-405B), so it can also be downloaded and run on your own hardware.
Quality scores
Rankings →Not rated yet. Independent test results usually appear a few weeks after a model is released.
Where to use it
Companies that serve this model through an API: 1. Prices per million tokens, cheapest first.
Availability and prices come from OpenRouter’s public API and are refreshed daily. Uptime is the share of successful requests over the last 24 hours. Some providers run a compressed version of open models (fp8, int4), which is cheaper but can be slightly less accurate.
Use it in your code
Call Hermes 4 405B through OpenRouter’s OpenAI-compatible API: create a key on openrouter.ai, then run one of these examples.
curl https://openrouter.ai/api/v1/chat/completions \
-H "Authorization: Bearer $OPENROUTER_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model": "nousresearch/hermes-4-405b", "messages": [{"role": "user", "content": "Hello! What can you do?"}]}'import os
from openai import OpenAI
client = OpenAI(base_url="https://openrouter.ai/api/v1", api_key=os.environ["OPENROUTER_API_KEY"])
reply = client.chat.completions.create(
model="nousresearch/hermes-4-405b",
messages=[{"role": "user", "content": "Hello! What can you do?"}],
)
print(reply.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({ baseURL: "https://openrouter.ai/api/v1", apiKey: process.env.OPENROUTER_API_KEY });
const reply = await client.chat.completions.create({
model: "nousresearch/hermes-4-405b",
messages: [{ role: "user", content: "Hello! What can you do?" }],
});
console.log(reply.choices[0].message.content);The same code works with every model on this site: only the model ID changes. Many labs also offer their own API and SDK.
What it costs in practice
- 1,000 chat replies$1.40
- Summarise a 100-page document$0.053
- An app with 10,000 requests a day for a month$660
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Frequently asked questions
- How much does Hermes 4 405B cost?
- Hermes 4 405B costs $1 per million input tokens and $3 per million output tokens through the API. For example, 1,000 chat replies of about 500 tokens in and 300 out cost around $1.40.
- What is the context window of Hermes 4 405B?
- Hermes 4 405B can read up to 131,072 tokens in one request, about 246 pages of text. It can write up to 117,964 tokens in a single answer.
- Is Hermes 4 405B open source?
- Yes. Its weights are published (NousResearch/Hermes-4-405B), so you can download it and run it on your own hardware, or use it through one of 1 API providers.
- Who makes Hermes 4 405B?
- Hermes 4 405B is made by Nous Research. It became available through the API on August 26, 2025.
- Can Hermes 4 405B read images?
- No. Hermes 4 405B only accepts text as input.
- What are the alternatives to Hermes 4 405B?
- Models with a similar price from other companies include Inkling, Grok Build 0.1 and Relace Search. You can compare them side by side on this page.