datavorous/sagent ? reverse-engineered prompt

Build me a Python 3.12+ project called sagent that gives me a smart coding agent I can use from both the command line and as a library. I want it to feel like a real assistant for working in a repo, with a simple interactive CLI, session resume, streaming output, JSON mode for piping into other tools, and a clean API I can import in my own code.

It should support more than one AI provider, let me switch models or providers during a session without restarting, and keep track of usage so I can set a spending limit. I also want built in tools for reading files, searching code, and web lookup, plus support for async tool calls and spawning sub agents that can talk to each other.

Please make it polished, with sensible defaults, good error handling, and a few working examples and docs so I can try it right away. If you need to check current provider docs or SDK details, look them up online.