Making three years of a Telegram group chat queryable

A three-year group chat is a knowledge base nobody can read. Somewhere in it is how long the tax office actually took, which form replaced the old one, which accountant people quietly stopped recommending. Telegram's search finds a word you already know. It cannot answer a question. The fix is boring in outline: get the history out, turn it into documents, hand them to something that reads — NotebookLM, in my case. I built that pipeline for real chats. The parsing has traps, and I list them below, but the design problem is elsewhere: packing, and making the second run idempotent. Two clients, two shapes Export exists in exactly two places. Telegram Desktop has had it since 2018 and offers JSON or HTML. The native Telegram for macOS app — the Mac-only client, not Desktop — added Export Chat History… in 12.10 (24 August 2026) and writes HTML only; the Mac App Store build was still on 12.9, without the menu item, at the end of August. Telegram Web and the phone apps have nothing. So you have to read both formats: JSON — one result.json with the chat's name at the root and a messages array: {id, date, from, text, text_entities} per message. HTML — paginated. messages.html , messages2.html , messages3.html , one page per file, each a few MB. text is not a string In the JSON export, a plain message has text: "hello" . A message with a link, a bold run or a code span has an array of runs : "text" : [ "see " , { "type" : "bold" , "text" : "section 4" }, " first" ] String(msg.text) on that gives "[object Object]" in the middle of your document, and it does it silently. Join the runs instead: // Telegram writes a formatted message as // text: ["plain ", {type: "bold", text: "…"}, …] — String() gives "[object Object]". function contentValueToString ( v : unknown ): string { if ( v === undefined || v === null ) return '' ; if ( Array . isArray ( v )) { return v . map (( x ) => x !== null && typeof x === ' object ' && ' text ' in x && typeof ( x as { text : unknown }). text ===