Hermes

Hermes is an open-source terminal agent from Nous Research. It registers named custom providers, and discovers the available models from each one automatically.

Setup

One command, no config files:

npx @opperai/cli launch hermes

The CLI uses an isolated HERMES_HOME=~/.opper/hermes-home/, so your real ~/.hermes/ is untouched.

To wire Opper into your existing Hermes setup, add your API key and register Opper as a named custom provider, then point the model block at it:

echo 'OPPER_API_KEY=your-api-key' >> ~/.hermes/.env

# ~/.hermes/config.yaml
model:
  provider: opper
  default: anthropic/claude-opus-4-7

custom_providers:
  - name: opper
    base_url: https://api.opper.ai/v3/compat
    key_env: OPPER_API_KEY

Choosing a model

Switch mid-session:

/model custom:opper:anthropic/claude-opus-4-7
/model custom:opper:gemini/gemini-3.5-flash

Hermes discovers the available models from Opper automatically — the model picker lists the full catalog without any per-model configuration.

Troubleshooting

The picker lists nothing

Hermes calls GET /v3/compat/models to populate it. An empty list usually means your model-access rules have narrowed the catalog to nothing for this key.

401 Unauthorized

key_env names the variable Hermes reads, so OPPER_API_KEY has to exist in ~/.hermes/.env or in the environment.

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Setup

Choosing a model

Troubleshooting

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