About

A fast, format-aware semantic line break formatter. Reformats prose so each sentence occupies its own line, producing minimal and meaningful git diffs when collaborating on documents.

Why?

When multiple authors collaborate on a paper using Git, traditional line wrapping at a fixed column width causes problems. A single word change can trigger a diff that spans an entire paragraph. By breaking at sentence boundaries instead, each edit affects only the sentence that changed.

This convention, often called semantic line breaks, enjoys longstanding support from technical writers. Existing tools fall short: latexindent.pl only handles LaTeX, SemBr requires Python and neural networks, and most lack multi-format awareness. snapper solves this as a standalone Rust binary with no runtime dependencies, handling Org-mode, LaTeX, Markdown, and plaintext.

Design

snapper runs a three-stage pipeline:

Parse: Classify input into prose regions and structure regions
Split: Detect sentence boundaries in prose regions
Emit: Output each sentence on its own line

Math environments, tables, front matter, drawers, and non-source comments pass through unchanged. Fenced and delimited source blocks are Region::Code: fence/open/close lines stay structure, non-comment code stays verbatim, and comment lines reflow at sentence boundaries when the language has a [code.<lang>] entry in .snapperrc.toml (snapper init seeds common languages). Pass --format-code to also pipe each block body through an optional per-language formatter argv (missing binary, non-zero exit, and timeouts degrade to the reflowed body). Sentence detection relies on Unicode UAX #29 segmentation with abbreviation-aware post-processing that avoids false breaks at titles (Dr., Prof.), references (Fig., Eq.), and Latin terms (e.g., i.e., et al.). Org emphasis (*bold*, /italic/, _underline_, +strike+) is kept atomic so splits cannot open a pseudo-headline mid-span.

Installation

Pre-built binary (fastest):

cargo binstall snapper-fmt

Shell one-liner (Linux/macOS):

curl -LsSf https://github.com/TurtleTech-ehf/snapper/releases/latest/download/snapper-fmt-installer.sh | sh

Homebrew:

brew install TurtleTech-ehf/tap/snapper-fmt

pip:

pip install snapper-fmt

Compile from source:

cargo install snapper-fmt

Nix:

nix build github:TurtleTech-ehf/snapper

The crate is snapper-fmt on all registries. Each install ships two CLI names for the same program: snapper and snapper-fmt.

Name collision: openSUSE snapper is a different project (Btrfs/LVM snapshots) that also installs a snapper binary. On systems where that tool already owns /usr/bin/snapper, call this formatter as snapper-fmt, or put the TurtleTech install path ahead of the system path.

Usage

Format a file (output to stdout):

snapper paper.org

Format in place:

snapper --in-place paper.org

Pipe through stdin (for editor integration):

cat draft.org | snapper --format org

Check formatting without modifying (for CI):

snapper --check paper.org paper.tex notes.md

Limit line width (wrap long sentences at word boundaries):

snapper --max-width 80 paper.org

Preview changes as a unified diff before committing:

snapper --diff paper.org

Compare two versions at the sentence level (whitespace reflow produces zero diff):

snapper sdiff paper_v1.org paper_v2.org

Watch files and auto-reformat on save:

snapper watch '*.org' 'sections/*.tex'

Initialize a project (generates config, pre-commit, gitattributes):

snapper init

MCP server (AI assistants)

The MCP server is an optional source-build feature; published release binaries do not include it. Install snapper with MCP support, then start the stdio server:

cargo install snapper-fmt --features mcp
snapper mcp

Tools: format_text, detect_format, check_formatting, split_sentences. Configuration guide (org source in-tree): docs/orgmode/howto/mcp-integration.org; HTML docs: https://snapper.turtletech.us/docs/howto/mcp-integration/ .

Supported formats

Format	Extensions	Structure / code handling
Org-mode	`.org`	Drawers, tables, keywords; `#+BEGIN_SRC` comment reflow
LaTeX	`.tex`, `.latex`	Preamble, math; minted and lstlisting comment reflow
Markdown	`.md`, `.markdown`	Front matter, HTML; fenced blocks comment reflow when configured
RST	`.rst`	Directives, literals; `.. code-block::` comment reflow
Plaintext	everything else	(none; all text treated as prose)

Pre-commit hook

- repo: https://github.com/TurtleTech-ehf/snapper
  rev: v0.9.0
  hooks:
    - id: snapper

Emacs (Apheleia)

(with-eval-after-load 'apheleia
  (push '(snapper . ("snapper" "--format" "org")) apheleia-formatters)
  (push '(org-mode . snapper) apheleia-mode-alist))

VS Code

Install TurtleTech.snapper from the VS Code Marketplace. The extension uses the built-in LSP server for format-on-save, range formatting, diagnostics, and code actions.

Neovim

With lazy.nvim (rocks support):

{
  "TurtleTech-ehf/snapper",
  ft = { "org", "tex", "markdown", "rst" },
  config = function()
    vim.opt.runtimepath:append(
      vim.fn.stdpath("data") .. "/lazy/snapper/editors/nvim"
    )
    require("snapper").setup()
  end,
}

Or with rocks.nvim:

:Rocks install snapper.nvim

Vim

Plug 'TurtleTech-ehf/snapper', { 'rtp': 'editors/vim' }

This provides formatprg support for automatic formatting with the gq operator.

Obsidian

Development preview; not listed in Community Plugins. The WebAssembly plugin source lives in editors/obsidian and is available for development builds only.

Microsoft Word

Development preview; not published in AppSource. The WebAssembly add-in source and sideloading instructions live in editors/word.

Git smudge/clean filter

Auto-format on commit, transparent to collaborators:

git config filter.snapper.clean "snapper --format org"
git config filter.snapper.smudge cat

Then add to .gitattributes:

*.org filter=snapper

Vale integration

snapper ships a vale style package for editor hints. Add to your .vale.ini:

StylesPath = /path/to/snapper/vale
[*.org]
BasedOnStyles = snapper

For precise CI checks, use snapper --check directly.

Project config

Drop a .snapperrc.toml in your project root:

extra_abbreviations = ["GROMACS", "LAMMPS", "DFT"]
ignore = ["*.bib", "*.cls"]
format = "org"
max_width = 0

snapper walks up from the current directory to find it.

Documentation

Build the docs site with:

pixi run docbld

Development

Key dependencies

Clap 4 (derive): CLI argument parsing
unicode-segmentation: UAX #29 sentence boundaries
regex: Abbreviation and format pattern matching
textwrap: Optional line width limiting
thiserror: Typed error handling

Conventions

We use cocogitto via cog to handle commit conventions.

Readme

Construct the readme via:

./scripts/org_to_md.sh readme_src.org README.md

License

MIT.

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Release history Release notifications | RSS feed

0.10.0

Aug 10, 2026

0.9.1

Aug 4, 2026

This release

0.9.0

Aug 4, 2026

0.8.1

Jul 20, 2026

0.8.0

Jul 20, 2026

0.7.9

Jul 8, 2026

0.7.8

Jun 27, 2026

0.7.7

Apr 11, 2026

0.7.6

Apr 9, 2026

0.7.5

Apr 9, 2026

0.7.4

Apr 9, 2026

0.7.3

Apr 8, 2026

0.7.2

Apr 8, 2026

0.6.0

Apr 4, 2026

0.4.0

Mar 29, 2026

0.3.2

Mar 28, 2026

snapper-fmt 0.9.0

Table of Contents

About

Why?

Design

Installation

Usage

MCP server (AI assistants)

Supported formats

Pre-commit hook

Emacs (Apheleia)

VS Code

Neovim

Vim

Obsidian

Microsoft Word

Git smudge/clean filter

Vale integration

Project config

Documentation

Development

Key dependencies

Conventions

Readme

License

Project links

Key dates

1 maintainer

Credits

GitHub Statistics

License

Requires

Tags

Classifiers

Download files

Source Distribution

Built Distributions

File details

File metadata

File hashes

Provenance

File details

File metadata

File hashes

Provenance

File details

File metadata

File hashes

Provenance

File details

File metadata

File hashes

Provenance

File details

File metadata

File hashes

Provenance

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Provenance

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