Hermes 3 405B Instruct
VerifiedOpen-weight instruct model tuned for complex reasoning and tool use.
About Hermes 3 405B Instruct
Hermes 3 405B Instruct was created by fine-tuning a large base model to improve adherence to detailed user instructions. Nous Research focused on enhancing multi-turn dialogue and structured output generation while keeping the weights openly available.
Its 131072-token context window allows processing of lengthy documents and extended conversations without truncation. The open-weight release enables local deployment, customization, and integration into research pipelines.
Typical applications include building custom agents, performing step-by-step reasoning tasks, and generating code or technical documentation. Users often combine it with external tools to extend its capabilities beyond pure text generation.
Capabilities
How Hermes 3 405B Instruct compares
Hermes 3 405B Instruct (striped bar) vs other language models on intelligence, speed and price.
Price
USD per 1M output tokens · Lower is better · Hermes 3 405B Instruct ranks #87 of 141
Sources: Artificial Analysis (intelligence, speed) · OpenRouter (price).
Best for
Long Document Analysis
The 131072 token context enables effective reasoning across very long inputs such as full books, lengthy reports, or extended conversation histories.
Agent and Tool Workflows
Strong tool use and function calling support the creation of reliable multi-step agents that interact with external APIs and data sources.
Complex Coding Projects
Advanced code generation combined with multi-step problem solving makes the model suitable for building large applications or debugging intricate codebases.
Strengths & limitations
Strengths
- +Strong complex instruction adherence
- +Effective agentic and tool-calling behavior
- +Good context retention over long inputs
- +Flexible for role-playing and custom fine-tuning
Limitations
- –Text modality only
- –High inference compute cost
- –Can still hallucinate on factual tasks
Cost calculator
Estimate what Hermes 3 405B Instruct would cost for your usage.
Based on Hermes 3 405B Instruct's $1.00/1M input · $1.00/1M output. Estimate only — actual cost varies by provider and caching.
Quick start
OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. Only the model slug changes between models.
import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://openrouter.ai/api/v1",
apiKey: process.env.OPENROUTER_API_KEY,
});
const completion = await client.chat.completions.create({
model: "nousresearch/hermes-3-llama-3.1-405b",
messages: [{ role: "user", content: "Hello!" }],
});
console.log(completion.choices[0].message.content);Model slug: nousresearch/hermes-3-llama-3.1-405b
Editor's verdict
Hermes 3 405B Instruct is Nous Research's open-weight language models with a 131K-token context window.
At $1.00 per 1M output tokens, it is mid-priced for its class.
As an open-weight model you can self-host it or call it through a hosted API.
Best suited to strong complex instruction adherence and effective agentic and tool-calling behavior.
Frequently asked questions
The model provides a context window of 131072 tokens.
User reviews
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