Symptom

Doctor's subagent_capability warn message recommends gbrain config set agent.use_gateway_loop true as alternative to setting ANTHROPIC_API_KEY. The config CLI rejects it:

$ gbrain config set agent.use_gateway_loop true
[config] Unknown config key "agent.use_gateway_loop".

Diagnosis

Either:

• The key name has drifted from what doctor advertises
• The config CLI needs --force to accept new keys (then doctor should say so)
• The feature was renamed/removed but doctor message wasn't updated

Suggested fix

Either restore the config key OR update doctor's recommendation to match the current config surface.