Module reflow 

The text-reflow engine — re-break a range of lines to textwidth.

Design: docs/dev/architecture/text-reflow.md §4. Sequencing: docs/dev/operations/slice-plans/text-reflow.md (this is RF.1).

A pure function of (lines, textwidth, comment leader, indent). No I/O, no syntax tree, no config lookup — the host resolves the options and hands the values down, exactly as it does for the indent unit.

Why it lives in lattice-grammar

Heuristic #6: it carves out no dependency surface, so it earns no crate. The operator that drives it (crate::builtins) reads crate::GrammarEnv, which already carries comment_syntax (N.1.6) and indent (IN.0); the host’s insert path (RF.3) calls the same module and already depends on this crate.

lattice-format was the other candidate and is the wrong one: that crate is process spawning, timeouts and diff-derived edits — a different mechanism that happens to share the word “format”.

What it is not

Not a reformatter. It moves line breaks and normalises interior whitespace within a paragraph, and touches nothing else — no reindentation of code, no reordering, no syntax awareness.

Structs

AutoWrapBreak

Where auto-wrap should break the line being typed on, and what the carried remainder needs in front of it.

Paragraph

One paragraph found inside a reflow range.

Prefix

The fixed prefix every line of a paragraph carries: indentation plus any comment leader, e.g. " /// " or "# " or just " ".

ReflowConfig

Everything the engine needs that it cannot derive from the text.

Functions

auto_wrap_break

Decide whether the line the cursor sits on should break, and where (§9).

display_width

Display width of s in terminal columns.

fill

Reflow one already-identified paragraph into output lines.

line_is_comment

Whether line reads as a comment, by its leading marker alone.

paragraphs

Split lines into paragraphs (§4.1).

reflow_range

Reflow a whole range: paragraphs found, fillable ones filled, everything else carried through.