Hermes needs both config.yaml and .env. First configure the provider, endpoint, and default model, then put your SU8 API key into the environment variable file.

config.yaml

model:
  default: gpt-5.5
  provider: custom:su8
  max_tokens: 128000
custom_providers:
  - name: SU8
    key_env: SU8_API_KEY
    base_url: https://www.su8.codes/v1
    api_mode: codex_responses
    models:
      gpt-5.5:
        context_length: 256000

.env

Replace <your SU8 API Key> with your own key.

SU8_API_KEY=<your SU8 API Key>

After configuration, fully restart Hermes, then run a simple request to verify it.