Current as of April 2026. GPT-5.2-Codex is OpenAI’s top-tier reasoning model designed for complex tool orchestration and massive context retention. It is the gold standard for Hermes Agent users who need reliable autonomous behavior across high-stakes multi-platform workflows.
Specs
| Provider | OpenAI |
| Input cost | $1.75 / M tokens |
| Output cost | $14 / M tokens |
| Context window | 400K tokens |
| Max output | 128K tokens |
| Parameters | N/A |
| Features | function_calling, vision, reasoning, web_search |
What it’s good at
Massive Context Retention
The 400K context window allows Hermes to maintain a massive persistent memory, keeping track of conversations across 15+ platforms without losing historical context.
Superior Tool Reliability
It handles the 47 built-in Hermes tools and complex MCP protocols with surgical precision, rarely hallucinating function arguments even in deep reasoning loops.
Advanced Multi-Platform Reasoning
The model excels at synthesizing information from disparate sources, like monitoring a Slack channel and executing shell commands based on specific triggers.
Where it falls short
Prohibitive Output Costs
At $14 per million output tokens, running this model for high-frequency messaging tasks on Telegram or Discord will get expensive very quickly.
Reasoning Latency
The deep reasoning features can introduce a 5-10 second delay before the agent takes action, which might feel slow for real-time chat interactions.
Best use cases with Hermes Agent
- Cross-Platform Enterprise Automation — It can accurately monitor Slack, query internal databases via MCP, and generate complex reports for Discord without human intervention.
- Persistent Identity Management — The 400K context window and closed learning loop enable the agent to maintain a consistent persona and memory over months of operation.
Not ideal for
- Simple Notification Bots — Using a reasoning-heavy model for simple message relaying is a waste of money given the $1.75/$14 token pricing.
- High-Volume Chat Apps — The latency and cost make it impractical for a WhatsApp bot handling thousands of simple user queries daily.
Hermes Agent setup
Configure the OpenAI provider with your API key and set the model ID to openai/gpt-5.2-codex; ensure your account tier supports high-concurrency reasoning tokens.
Hermes makes custom endpoints easy. Run:
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-5.2-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 for basic tool use, but GPT-5.2-Codex’s 400K context window crushes Sonnet’s 200K limit for long-term memory.
- vs GPT-4o — GPT-4o is better for low-latency chat, but GPT-5.2-Codex is significantly more reliable when Hermes needs to sequence multiple MCP tool calls.
Bottom line
This is the model you choose when your Hermes Agent needs to be a reliable autonomous employee rather than just a chat bot.
For more, see our Hermes local-LLM setup guide.