# `Sembr`: Semantic Line Break (SemBr) Paragraph Reflow

```{py:currentmodule} myform.Sembr
```

`Sembr` rewrites already-rendered paragraph text into one-sentence-per-line form
("semantic line breaks"): soft-wrapped lines are joined back into logical sentences, then
newlines are re-inserted at sentence boundaries. CommonMark renderers collapse single
newlines inside a paragraph, so the rendered output is unchanged -- this is purely a
source-legibility transform (sentence-granular diffs and edits).

Off by default; opt in via the `sembr` plugin option (`[plugin.myst] sembr = true` in
`.mdformat.toml` or `--sembr` on the CLI); `Postprocessor.postprocess_paragraph` is the
caller.

The splitter is deliberately conservative: a boundary requires sentence-final punctuation,
a following sentence opener, and must not sit inside a code span or inline math, after an
abbreviation, single-letter initial, or bare number, or where the new line would re-parse
as block syntax (ordered-list interrupts). A missed split costs nothing; a wrong split
could change the AST (mdformat's validation would then reject the whole reformat).

The patterns live in a `my.regex.RegexStore` (wikiparse's idiom): named, composable
definitions joined by subroutine invocation, the abbreviation list condensed into a
prefix-factored alternation tree, and compilation deferred to first use (lazy load), so
importing this module stays cheap.

```{eval-rst}
.. automodule:: myform.Sembr
   :members:
```