**Problem**: stock-morning-brief, Xiaohongshu publishing, document processing and other tasks all run on the main agent. When one fails, logs are mixed together, making it hard to locate the issue.

**Cause**: Single-node architecture with no isolation — any task's errors spill into the same log stream, with no clear ownership boundaries.

**Solution**: Split into sub-agents. stock-trader handles three stock-related cron jobs exclusively; doc-agent handles document processing — each with its own independent workspace and logs. The main agent only handles scheduling and interaction.

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**Principle**: One agent, one type of task. Separation of concerns isn't about elegance — it's about being able to quickly pinpoint issues when they happen, and fix one without breaking another.