Gateway should clearly reload config or warn that model changes require restart

[leonardorojo]

Summary

Changing ~/.hermes/config.yaml — including model.default, provider, or api_mode — does not affect a running Gateway until hermes-gateway is restarted.

In my setup, this was not obvious, and the Gateway continued using the previous configuration until restart.

Steps to reproduce

1. Start hermes-gateway.
2. Edit ~/.hermes/config.yaml and change model.default or api_mode.
3. Do not restart the Gateway.
4. Observe that the running Gateway continues using the old configuration.

Expected behavior

One of the following should happen:

• The Gateway hot-reloads the relevant configuration, or
• The Gateway clearly logs or warns that a restart is required for config changes to take effect.

Actual behavior

The running Gateway keeps using the previous configuration until it is restarted.

Environment

• OS: Linux Mint
• Gateway execution mode: systemd --user
• Config file: ~/.hermes/config.yaml

Notes

This behavior can be confusing because changing the config file appears to succeed, but the running Gateway silently continues with the old settings until a manual restart is performed.

[teknium1]

Closing as implemented on main via automated hermes-sweeper review.

• website/docs/user-guide/configuring-models.md:159 now states that model configuration changes apply to the next new Gateway session; existing live sessions intentionally retain their model to preserve prompt caching.
• The same guidance documents hermes gateway restart as the explicit way to force all Gateway sessions to adopt the new configuration.
• Current Gateway runtime resolution reads the active configuration for agent setup (gateway/run.py:17894), while /restart is documented as a graceful, draining Gateway restart (website/docs/reference/slash-commands.md:246).
• The timeline-linked PR feat(cli): warn users to restart gateway after config changes #13217 proposed a generic restart warning; the current behavior and model-specific guidance supersede the original report.

This shipped in commit 3c27efbb914ae43f0f8f3c6299dc7079b91bea6b and is included in v2026.4.30.