---
title: "GPT-5.1-Codex for Hermes Agent: Pricing, Setup, and What It's Good At"
description: "Everything you need to know about using GPT-5.1-Codex with Hermes Agent. Costs $1.25/M input, $10/M output. 400K context window. Here's when to use it and when to pick something else."
date: 2026-04-17
updatedDate: 2026-09-08
image: /images/models/provider-openai-hero.jpg
keywords: "gpt-5.1-codex hermes, gpt-5.1-codex pricing, gpt-5.1-codex review, openai hermes, gpt-5.1-codex api"
category: model-guide
modelData:
  provider: "OpenAI"
  provider_slug: "openai"
  full_id: "openai/gpt-5.1-codex"
  input_cost_per_1m: 1.25
  output_cost_per_1m: 10
  max_input_tokens: 400000
  max_output_tokens: 128000
  features: ["function_calling", "vision", "reasoning"]
  parameter_count: null
  architecture: null
  license: null
faq:
  - question: "What is the exact pricing for GPT-5.1-Codex?"
    answer: "Input tokens cost $1.25 per million and output tokens cost $10 per million."
  - question: "How large is the context window for Hermes memory?"
    answer: "The model supports up to 400,000 tokens in the context window with a 128,000 token output limit."
  - question: "Does it support image processing from platforms like Discord?"
    answer: "Yes, it has full vision support, allowing Hermes to interpret screenshots or files sent via any of the 15+ supported messaging channels."
---

Current as of April 2026. GPT-5.1-Codex is OpenAI's high-reasoning model optimized for complex tool execution, despite the coding-centric branding. For Hermes Agent, it provides a massive 400K context window and reliable function calling that excels in multi-step autonomous workflows across different messaging platforms.

## Specs

| | |
|---|---|
| **Provider** | OpenAI |
| **Input cost** | $1.25 / M tokens |
| **Output cost** | $10 / M tokens |
| **Context window** | 400K tokens |
| **Max output** | 128K tokens |
| **Parameters** | N/A |
| **Features** | function_calling, vision, reasoning |

## What it's good at

#### Reliable Tool Execution

The model handles complex MCP tool chains with high precision, rarely hallucinating parameters during long autonomous runs.

#### Massive 400K Context Window

It maintains persistent memory across weeks of Slack and Discord logs without needing to constantly prune the message history.

#### Advanced Reasoning Chains

The reasoning capabilities allow it to plan multi-platform operations, such as monitoring a webhook and executing shell commands on Modal, with minimal failure.

## Where it falls short

#### High Output Costs

At $10 per million output tokens, it is significantly more expensive than competitors for high-volume automated messaging.

#### Inherent Latency

The internal reasoning process adds noticeable delay, which can make real-time interactions on WhatsApp feel sluggish.

#### Verbose Responses

The model tends to over-explain its logic before calling a tool, which consumes unnecessary output tokens in a closed learning loop.

## Best use cases with Hermes Agent

- **Cross-Platform Orchestration** — It effectively manages workflows spanning Discord, SSH, and Docker while keeping track of complex state changes across 47 built-in tools.
- **Deep History Analysis** — The 400K window allows Hermes to ingest months of platform data to inform its autonomous decisions without losing the thread.

## Not ideal for

- **Simple Notification Bots** — Using a $10/1M output token model for basic Telegram alerts is a waste of budget when cheaper models exist.
- **Low-Latency Chat** — If your Hermes instance requires instant replies for human interaction, the reasoning overhead will frustrate users.

## Hermes Agent setup

Configure the provider as OpenAI and set the model ID to openai/gpt-5.1-codex. You must increase the request timeout in your Hermes config to at least 60 seconds to prevent drops during complex reasoning phases.

Hermes makes custom endpoints easy. Run:

```bash
hermes model
```

Choose **Custom endpoint** from the menu. Enter the base URL and model identifier when prompted:

- **Base URL:** `https://api.haimaker.ai/v1`
- **Model:** `openai/gpt-5.1-codex`

Hermes stores the selection and uses it for all subsequent agent runs across whatever platforms you have wired up (Telegram, Discord, Slack, etc.). Tune `HERMES_STREAM_READ_TIMEOUT` and related env vars if you're hitting slow providers.

## How it compares

- **vs Claude 3.5 Sonnet** — Sonnet is faster and cheaper at $3/$15, but GPT-5.1-Codex handles the 400K context window with much better recall for long-term memory.
- **vs GPT-4o** — GPT-4o is a better generalist for chat, but Codex is more rigid and reliable when executing strict MCP protocols and shell commands.

## Bottom line

GPT-5.1-Codex is the premium choice for Hermes users who need rock-solid tool reliability and massive context windows, provided they can stomach the high output costs and latency.

<a href="https://app.haimaker.ai/sign-up?utm_source=model_guide&utm_medium=cta&utm_campaign=hermes_gpt-5-1-codex" class="cta-button">TRY GPT-5.1-CODEX IN HERMES</a>

---

*For more, see our [Hermes local-LLM setup guide](https://hermes-agent.nousresearch.com/docs/guides/local-llm-on-mac).*