Hermes 4 405B
Summary
Hermes 4 405B is an open-weight language model from Nousresearch, released on 26 Aug 2025. It accepts text and generates text, with a 131K-token context window and up to 118K output tokens per response. As of 4 Oct 2026, the lowest listed API price is $1 per million input tokens and $3 per million output tokens (OpenRouter), across 1 provider we track.
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...
Last verified 4 Oct 2026. Every figure on this page links to its source.
Specifications
| Developer | Nousresearch |
|---|---|
| Release date | 26 Aug 2025 [OpenRouter] |
| Status | Generally available |
| Weights | Open weights [Hugging Face] |
| License | llama3 [Hugging Face] |
| Parameters | 406B [Hugging Face] |
| Context window | 131K (131,072 tokens) [OpenRouter] |
| Max output | 118K tokens [OpenRouter] |
| Knowledge cutoff | 31 Aug 2024 [OpenRouter] |
| Input | Text [OpenRouter] |
| Output | Text [OpenRouter] |
| Reasoning mode | Yes [OpenRouter] |
| Tool calling | No [OpenRouter] |
| Structured output | No [OpenRouter] |
| Hugging Face | NousResearch/Hermes-4-405B [Hugging Face] |
Hermes 4 405B API pricing by provider
USD per million tokens. Sorted by input price.
| Provider | Input | Output | Cached input | Context | Source |
|---|---|---|---|---|---|
| OpenRouter nousresearch/hermes-4-405b | $1 | $3 | – | 131K | OpenRouter, 4 Oct 2026 |
Frequently asked questions
What is the context window of Hermes 4 405B?
Hermes 4 405B has a context window of 131,072 tokens (131K) and can generate up to 117,964 tokens in a single response, according to OpenRouter.
How much does the Hermes 4 405B API cost?
Hermes 4 405B is listed from $1 per million input tokens and $3 per million output tokens (OpenRouter). Prices last verified 4 Oct 2026.
Is Hermes 4 405B open source?
Hermes 4 405B is an open-weight model: its weights are published on Hugging Face as NousResearch/Hermes-4-405B under the llama3 license. Check the license terms before commercial use.
When was Hermes 4 405B released?
Nousresearch released Hermes 4 405B on 26 Aug 2025, according to OpenRouter.
Change history
No changes detected since we started tracking this model. We re-check every source daily.