Where to take it next

The mini-harness is a foundation, not a finish line. Natural extensions, each pointing back to a chapter:

• Real sandboxing. Replace the bare subprocess call with an actual sandbox (containers, or the OS mechanisms from Chapter 7). This is the single most important hardening step before running it on anything you care about.
• CodeAct mode. Add Chapter 14's code-action executor as an alternative to discrete tool calls, plus a Planner that writes a todo.md.
• MCP servers. Register external tools through the Chapter 10 MCP client to connect real systems.
• A real review pass. Wire Chapter 13's two-tier review (LLM plus a deterministic check) into review().
• Budgets and observability for production. Persist a session log (Chapter 12), expose max_budget_usd properly (Chapter 16), and run it headless in CI with a human gate.
• Deep research mode. Add Chapter 15's MasterAgent/SubAgent/ReviewAgent flow for sourced reports.