¬ just serendipity 🍀 (not just serendipity)

Problem statement: split a running Pi conversation / session into a second independent one whilst keeping the original.

Pi has three similarly named albeit distinct operations:

/fork
/clone
pi --fork <path|id>

/fork opens a selector for an earlier user message, copies the active path up to the message’s parent into a new session, and puts the selected prompt back in the editor. This is for changing an earlier request.

/clone copies the current active root-to-leaf path into a new session and switches the current Pi process to it. The old session file remains unchanged; retrieve it with /resume, or note its ID first and open it directly:

/session
/clone

% pi --session 019feb2b

The CLI spelling does something subtly different:

% pi --help | grep -A5 -- '--session <path'
  --session <path|id>            Use specific session file or partial UUID
  --session-id <id>              Use exact project session ID, creating it if missing
  --fork <path|id>               Fork specific session file or partial UUID into a new session
  --session-dir <dir>            Directory for session storage and lookup
  --no-session                   Don't save session (ephemeral)
  --name, -n <name>              Set session display name

pi --fork copies the complete source session file, including all branches, then opens the copy in a new Pi process. The running source process is untouched:

# current Pi
/session

# second terminal, same project
% pi --fork 019feb2b

It’s easier to do so if we add the session ID to the Pi status bar. Pi loads extensions from ~/.pi/agent/extensions/, so I have this one:

// ~/.pi/agent/extensions/session-id.ts
import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";

export function updateSessionIdStatus(ctx: ExtensionContext): void {
  const sessionId = ctx.sessionManager.getSessionId();
  ctx.ui.setStatus("session-id", ctx.ui.theme.fg("dim", `sid:${sessionId}`));
}

export default function (pi: ExtensionAPI) {
  pi.on("session_start", async (_event, ctx) => updateSessionIdStatus(ctx));
}

For a linear session, pi --fork and /clone produce equivalent conversation context. Once a session has branches, /clone extracts only the active branch; pi --fork preserves the full tree.

Pi sessions are JSONL trees, so none of these operations mutate the source history. For splitting one live conversation into two live processes, use pi --fork <id>.