The heartbeat prompt from agents.defaults.heartbeat.prompt was being
injected into the system prompt for ALL agents, causing non-default
agents to read the default agent's identity files and adopt its persona.
Now the heartbeat prompt is only included when the session's agent ID
matches the configured default agent. Other agents receive no heartbeat
section in their system prompt.
Co-Authored-By: Claude Opus 4.5 <[email protected]>