pi: /btw side-chat

Developer Thiago Perrotta implemented a '/btw' side-chat extension for the pi coding agent, allowing tangential questions to be answered without polluting the main agent thread. The extension reads a frozen snapshot of the main conversation, calls the model directly in a custom UI overlay, and never appends to the session, preserving the main thread's state. Perrotta reimplemented the feature against the current API of earendil-works/pi, cross-checking with the bundled summarize.ts example, and added it to his dotfiles repository.

♠ Previously https://perrotta.dev/2026/07/pi-auto-retry-stalled-requests/ . Problem statement : mid-task, I want to ask the LLM agent a quick tangential question — “will this change cause downtime?” — without polluting the main agent thread. Claude Code has /btw 1 for exactly this. The upstream extension imports the pre-fork @mariozechner/ package names, which are now deprecated. As such, I use earendil-works/pi https://github.com/earendil-works/pi . Rather than trust a diff I hadn’t read, I reimplemented it against the current API, and cross-checked against the bundled examples/extensions/summarize.ts the canonical example for calling the model from an extension : python import { complete } from "@earendil-works/pi-ai/compat"; import type { ExtensionAPI, SessionEntry } from "@earendil-works/pi-coding-agent"; import { convertToLlm, getMarkdownTheme } from "@earendil-works/pi-coding-agent"; // ...inside the /btw command handler, once at entry: const branch = ctx.sessionManager.getBranch ; const mainMessages = branch .filter entry : entry is SessionEntry & { type: "message" } = entry.type === "message" .map entry = entry.message ; const mainLlmMessages = convertToLlm mainMessages ; // frozen snapshot const systemPrompt = ctx.getSystemPrompt ; // ...per question, the side-chat calls the model directly: const response = await complete ctx.model , { systemPrompt, messages: ...mainLlmMessages, ...btwLlmMessages }, { apiKey: auth.apiKey, headers: auth.headers, env: auth.env, signal }, ; The key move is what’s missing : the handler never calls pi.sendMessage or appends anything. It reads the branch once, talks to the model in an ctx.ui.custom https://github.com/earendil-works/pi/blob/main/packages/coding-agent/docs/extensions.md custom-ui overlay, and returns. The main session is untouched, so the next real prompt doesn’t pay for any of it. Added to ~/.pi/agent/extensions/btw.ts https://github.com/thiagowfx/.dotfiles/blob/1f42eb6f6632f946c23d1278e7e3f18da78d5de8/pi/.pi/agent/extensions/btw.ts . 🤖 Drafted with /bloggify .— § — Reply via email mailto:serendipity@perrotta.dev?subject=Reply to: pi: /btw side-chat