Collaborative Calculation and Data Science

energyhub

colby

sagemath

github

google

cornellcollege

depaul

Per-region chat threads and collaborative bookmarks now work directly inside LaTeX documents. Drop a short comment on any line and CoCalc attaches a side-chat thread or a named bookmark to that exact location — no sidebar search, no copying line numbers.

![LaTeX chat markers and bookmarks in action](https://storage.googleapis.com/cocalc-extra/2026-04-24-latex-chat-bookmarks.png)

## Anchored chat threads

Type a LaTeX comment like `% chat: review-sec2` (block form on its own line, or inline after content) and a dedicated discussion thread opens for that location. The hash can be a short random ID or a mnemonic of your choice — anything matching `[A-Za-z0-9_-]{3,64}`.

- **Gutter icon** — every marker line gets a compact chat icon. It turns red when there are unread messages, gray otherwise. Click to open the thread.
- **Inline tail widget** — right after the comment, a pill shows `N unread` (red) or `N messages` (gray), plus a small `×` to delete the marker with a confirmation.
- **Read-only lock** — once a thread has a real message, its anchor line becomes atomic and bold so collaborators don't accidentally renumber or overwrite it. Deleting the root message unlocks the line.
- **Multi-file** — markers work across `\input{...}` sub-files. The thread header shows `<hash> (file:line)` with a Jump button; if the same hash appears in several places, a dropdown lets you pick the destination.
- **Cursor-follow insert** — a faint chat icon tracks your cursor in the gutter. Click it to insert a new `% chat:` marker on the current line.

Insert a marker from the menu via **Insert → Chat** or with **Ctrl-Shift-M** (**Shift-Cmd-M** on macOS). In split panes, the inserted marker targets the pane you are actually editing.

## Collaborative bookmarks

Bookmarks are a lighter cousin of chat anchors — free-form text markers for "remember this spot".

- Write `% bookmark: introduction refactor` on any line.
- The **Contents panel** (Output → Contents) lists bookmarks interleaved with your section hierarchy at a deeper indent, marked with a blue bookmark icon. Clicking jumps to the line.
- The gutter shows a gray bookmark icon on each bookmark line.
- Insert via **Insert → Bookmark** or **Ctrl-Shift-B** (**Shift-Cmd-B** on macOS). The default text is pre-selected so you can rename it immediately.

Bookmarks don't lock the line and don't create a chat thread — they're purely for navigation and for sharing interesting spots with collaborators.

## Why comments?

Because the markers are just LaTeX comments, they travel with the file. They survive copy/paste between projects, show up in git diffs, and are invisible to `pdflatex`. Open the same `.tex` file with two users and both see the same icons, threads, and bookmarks in real time.

The same per-region chat model already powers per-cell discussions in Jupyter notebooks; LaTeX now shares that infrastructure, and both benefit from the same fixes — including a small bug where the sender briefly saw their own message as unread.

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