A terminal that keeps agent sessions as data, not pixels

Cavrn is crystl's terminal engine. Where a normal terminal hands you scrollback (characters on a grid), Cavrn keeps a live, structured model of the session. Every user turn, assistant reply, tool call, and tool result is captured as a typed, timestamped record; a tool call is linked by id to the result it produced; a table an agent draws knows it's a table. It's the difference between a picture of the terminal and data about it.

Because the output is structured, things that used to be impossible become one call. A sibling agent reads your session with crystl screen --json or crystl history --json and gets typed records (turns, tool calls, results), not a screenshot. crystl's history navigator searches every past turn and tool call. A table an agent draws, box-drawing or markdown, is detected on the fly and copied as raw, CSV, or JSON. The phone app re-renders the same model cleanly instead of replaying escape codes. All of it reads from the one structured surface Cavrn keeps.

Cavrn is also built for how you actually run agents: several at once, most of them off-screen. It's painted on the GPU with Metal, but the sharper win is what it skips. An off-screen shard flooding output does almost no render work, and the visible one repaints only the rows that changed. Other terminals make one window fast; crystl keeps a dozen live agents light, so a big fan-out scrolls smoothly while your CPU stays free for the work. It's the default surface for new shards. Read the GPU rendering docs for that side of it.