Claude Assistant for LibreOffice Writer

A LibreOffice Writer extension that adds a native Claude sidebar: chat with Claude, rewrite the selected text, generate or continue writing, and summarise the document — with every edit previewed for Apply / Reject before it touches your document.

It authenticates off your existing Claude Code login (subscription) via the Claude Agent SDK — no Anthropic API key required.

How it works

LibreOffice (Writer)                         agent sidecar (Python 3.10+ venv)
  Claude sidebar panel  ── JSON over a pipe ──  claude-agent-sdk
  owns the document (UNO)                        in-process MCP server "writer"
  applies edits on approval                      drives Claude via Claude Code login

The extension exposes the document to Claude as MCP tools (get_document_text, get_selection, replace_selection, insert_at_cursor). Claude calls them; edit tools are gated by the sidebar's preview-then-apply UI. The agent runs in a separate Python process (the sidecar) because LibreOffice's bundled Python is usually too old for the SDK; the two talk over the subprocess pipe. Document edits are applied in-process via UNO as single undoable steps.

Related MCP server: Ultimate Google Docs & Drive MCP Server

Prerequisites

1. Claude Code CLI, installed and logged in:

   claude        # then /login if needed

2. LibreOffice with Python scripting (standard on Linux).

3. A Python 3.10+ environment with claude-agent-sdk for the sidecar.

Install

One command does everything — creates the sidecar Python environment, installs the Claude Agent SDK, points the extension at it, builds the .oxt, and installs it into LibreOffice:

./install.sh

It needs uv (preferred) or a python3 with venv+pip. Then restart LibreOffice, open Writer, and pick the Claude tab in the sidebar. To remove it later: ./uninstall.sh.

uv venv .venv && uv pip install -r requirements.txt   # sidecar SDK env
mkdir -p ~/.config/claude-writer
echo "$PWD/.venv/bin/python" > ~/.config/claude-writer/python
PYTHON=.venv/bin/python ./build.sh                    # -> claude-writer.oxt
unopkg add --force claude-writer.oxt

Pointing at a different Python

By default the panel launches <extension>/.venv/bin/python. Override with:

export CLAUDE_WRITER_PYTHON=/path/to/python3   # has claude-agent-sdk installed

Optional model override: export CLAUDE_WRITER_MODEL=claude-opus-4-8.

Usage

• Rewrite: select text, ask e.g. "make this more formal" → Claude reads the selection and proposes a replacement; Apply or Reject.

• Generate / continue: place the cursor, ask "continue this paragraph" → Claude proposes an insertion to approve.

• Summarise: ask "summarise this document" → Claude reads the full text.

• Chat: ask anything; Claude answers in the panel without editing.

Applied edits are single undo steps — Ctrl+Z reverts cleanly.

Project layout

Testing the backbone (no GUI)

cd sidecar
../.venv/bin/python fake_panel_test.py ../.venv/bin/python "Make my selection formal."

This drives the real sidecar with a faked document and prints the tools Claude called and the edits it proposed — verifying Claude Code auth and the MCP round-trip without LibreOffice.

Status

v0.1 — working: native sidebar (chat, rewrite selection, generate/continue, summarise), in-document highlighted preview with Apply / Improve / Reject, whole-document rewrite, Enter-to-send, and Claude Code (subscription) auth with no API key. Document operations and the agent round-trip are verified against a live LibreOffice.

License

MIT — see LICENSE. Note: the Claude name and the sidebar icon are Anthropic brand assets and are not covered by the MIT license; replace the icon before redistributing if you don't have permission to use it.