Nous: Hermes 4 405B✓ Catalog verified
Hermes 4 is a large-scale reasoning model built on Meta-Llama-3.1-405B and released by Nous Research. It introduces a hybrid reasoning mode, where the model can choose to deliberate internally with <think>...</think> traces or respond directly, offering flexibility between speed and depth. Users can control the reasoning behaviour with the `reasoning` `enabled` boolean. Learn more in our docs The model is instruction-tuned with an expanded post-training corpus (~60B tokens) emphasizing reasoning traces, improving performance in math, code, STEM, and logical reasoning, while retaining broad assistant utility. It also supports structured outputs, including JSON mode, schema adherence, function calling, and tool use. Hermes 4 is trained for steerability, lower refusal rates, and alignment toward neutral, user-directed behavior.
Overview
Hermes 4 is a large-scale reasoning model built on Meta-Llama-3.1-405B and released by Nous Research. It introduces a hybrid reasoning mode, where the model can choose to deliberate internally with <think>...</think> traces or respond directly, offering flexibility between speed and depth. Users can control the reasoning behaviour with the `reasoning` `enabled` boolean. Learn more in our docs The model is instruction-tuned with an expanded post-training corpus (~60B tokens) emphasizing reasoning traces, improving performance in math, code, STEM, and logical reasoning, while retaining broad assistant utility. It also supports structured outputs, including JSON mode, schema adherence, function calling, and tool use. Hermes 4 is trained for steerability, lower refusal rates, and alignment toward neutral, user-directed behavior.
Access: available through the official Nousresearch API. Context window: 131K.
Specifications
| API identifier | nousresearch/hermes-4-405b |
| Provider | Nousresearch |
| Model type | Text LLM |
| Context window | 131K catalog |
| Input modalities | text |
| Output modalities | text |
| Released | Aug 26, 2025 |
| Moderated | No |
| Architecture modality | text->text |
Pricing
Live pricing components for nousresearch/hermes-4-405b as published in the catalog.
| Pricing component | Raw unit price | Normalized | Unit |
|---|---|---|---|
| Prompt tokens | $0.000001 | $1.00 / 1M | Per input token |
| Completion tokens | $0.000003 | $3.00 / 1M | Per output token |
| Request fee | N/A | N/A | Per request |
| Image fee | N/A | N/A | Per image unit |
| Web search fee | N/A | N/A | Per search request |
Cost calculator
Estimate monthly spend from your own token volumes.
Estimated Total Cost
$1.1Calculated from current list pricing in the ModelsAtlas catalog.Capabilities
| Capability | Status | What it means |
|---|---|---|
| Visual Understanding | Not advertised | Image and document analysis support |
| Audio Processing | Not advertised | Speech and voice aligned flows |
| Tool Calling | Not advertised | Supports tools / function calling |
| Self-Hosting | Not advertised | Deploy outside managed APIs |
Capability signals
Directional signals derived from model metadata and capability tags — not official benchmark submissions.
Quick start
Call Nous: Hermes 4 405B through an OpenAI-compatible client.
from openai import OpenAI
client = OpenAI(
base_url="https://openrouter.ai/api/v1",
api_key="YOUR_API_KEY"
)
response = client.chat.completions.create(
model="nousresearch/hermes-4-405b",
messages=[{"role": "user", "content": "Explain quantum physics."}]
)
print(response.choices[0].message.content)Alternatives
Closest models by context window from a different provider.
| Model | Provider | Context | Input /1M | Actions |
|---|---|---|---|---|
| AionLabs: Aion-1.0 | Aion Labs | 131K | $4.00 | View → |
| AionLabs: Aion-1.0-Mini | Aion Labs | 131K | $0.70 | View → |
Sources & attribution
Pricing and metadata are maintained in the ModelsAtlas catalog.
Frequently asked questions
How much does Nous: Hermes 4 405B cost?
$1.00 per 1M input tokens and $3.00 per 1M output tokens on the official Nousresearch API.
What is the context window of Nous: Hermes 4 405B?
Nous: Hermes 4 405B supports up to 131K tokens of context.
Does Nous: Hermes 4 405B support tool / function calling?
Nous: Hermes 4 405B does not advertise first-class tool/function calling. Check vendor docs for the latest capabilities.
How do I access Nous: Hermes 4 405B?
Use the official Nousresearch API with the model id `nousresearch/hermes-4-405b`. See the Quick start section above for code examples.