ltx

A local browser editor for LaTeX papers that you and Claude Code can edit at the same time.

Site: https://danieldager.github.io/ltx/

Why

When Claude Code edits a .tex file while you have it open in an editor, one of you loses work: the editor reloads over your typing, or your save overwrites the edit. ltx treats the file on disk as the shared document. Your keystrokes stay local and are saved as small patches; edits that arrive from outside are merged into the open buffer within about a second, around whatever you have typed. You keep working in the browser, Claude keeps working in the terminal, and the PDF rebuilds in the background.

Features

• Source buffer (CodeMirror 6) set in an economics-paper look: Latin Modern type, one paragraph per line, section numbers, citation and reference chips, KaTeX math and HTML tables when you switch the LaTeX view off.
• Surgical saves: opening and saving a file without changes writes zero bytes; changing one word changes one line.
• Live merging of external edits; if you both touch the same characters, the file on disk wins and your replaced text is shown so you can re-insert it.
• Background PDF with tectonic, shown beside the source; errors are explained in plain words and the last good PDF stays on screen.
• Selection, comments and suggestions are written to .ltxed/ next to your paper, where Claude Code reads them. Lines that change on disk flash briefly, so you see what Claude just edited.
• Outline with word counts per section, a comments list with an open-comment badge, find and replace (Cmd+F), and Cmd+J to show the cursor's place in the PDF (double-click the PDF to go back).
• A « ? » button in the toolbar explains every button, key and colour.
• Multi-file papers (\input, \include), appendix numbering across files.
• Everything runs on 127.0.0.1; there is no account, cloud or telemetry.

Install

Needs Python 3.11+, uv and tectonic:

brew install tectonic
uv tool install git+https://github.com/danieldager/ltx

Without installing: uvx --from git+https://github.com/danieldager/ltx ltx --help.

Use

ltx new paper/            # create paper/main.tex and references.bib from a template
ltx open paper/main.tex   # start the server and open the browser (a second open reuses it)
ltx stop paper/           # stop the server for that folder

ltx open prints the URL and logs to paper/.ltxed/server.log. Add .ltxed/ to your .gitignore.

Use with Claude Code

Install the skill once:

ltx setup-claude              # writes ~/.claude/skills/ltx/SKILL.md (idempotent)
ltx setup-claude --uninstall

With a paper open in ltx, talk to Claude Code in the terminal as usual. The skill makes Claude read the files ltx keeps in .ltxed/:

File	Written by	Use
selection.json	ltx, on every selection change	"rewrite this paragraph", "shorten the selected table caption"
comments.json	ltx (you), Claude (status and reply)	select text, add a comment, then say "do the comments"
suggestions.json	Claude	edits Claude proposes; you accept, reject or discuss each in the editor
compile_errors.json	ltx, after each build	"fix the build"

Claude edits the .tex files directly with surgical Edit calls, one paragraph per line, and checks compile_errors.json after each change.

To have Claude pick up comments as you write them, ask it to monitor. In Claude Code this uses the Monitor tool with this command:

ltx watch paper/main.tex

ltx watch prints one line per newly opened comment (<id> <file>:<line> <instruction>) and nothing otherwise, so each line wakes Claude, which applies the comment, sets its status and reply, and goes back to waiting. Add --skip-existing to ignore comments that are already open.

Develop

git clone https://github.com/danieldager/ltx && cd ltx
uv sync
uv run pytest tests -q      # headless Chromium via Playwright; needs tectonic
cd web && npm install && npm run build   # rebuilds src/ltx/static/

The built frontend in src/ltx/static/ is committed, so installing from git needs no Node. SPEC.md has the design and the frozen protocol; HANDOFF.md has build notes.

Status and limits

A personal tool, tested on macOS only (the tests assume Meta+ shortcuts and a Homebrew tectonic). Known limits:

• No CRLF or BOM handling; files must be UTF-8 with LF line endings.
• Characters outside the Basic Multilingual Plane can desync offsets.
• Undefined reference and citation warnings are not linked to a file.
• Section numbering across \input files is computed by the editor and can differ from LaTeX.
• On launch the server builds and overwrites <name>.pdf next to the source.

License

MIT, see LICENSE. Bundled third-party files (Latin Modern fonts under the GUST Font License, KaTeX under MIT, pdf.js under Apache 2.0, CodeMirror under MIT) are listed there.