wtf is chagent?

chagent is a small command line tool for moving an in progress AI coding session from one assistant to another without losing the conversation. It can read and write session files from Claude Code, Pi, OpenCode, and Codex, so if you started a task in one of these tools you can continue the exact same conversation, including its history and tool calls, in a different one. Using it is a single command: you give chagent part of a session ID and the name of the tool you want to switch to, and it automatically searches across all four supported tools to find where that session actually lives, converts it, and prints the exact command needed to resume the converted session in the new tool. A companion command lists the sessions chagent can see on your machine. The compatibility table in the project's documentation is detailed about what carries over across every combination of tools: plain text, images, and attachments transfer cleanly everywhere, as do shell, edit, and write tool calls, other tool calls, subagent transcripts, conversation compaction, and model or token usage figures, though Codex drops the recorded cost figure and only shows plain text for what the assistant was thinking rather than any richer formatting. Tool calls that a target assistant does not recognize are still carried over as is, so the underlying model can see them in its history even though the interface may not render them nicely. The tool installs globally through the bun package manager and is aimed squarely at developers who regularly switch between multiple AI coding assistants and do not want to restart a task from scratch each time they do.