# Fill Paragraph Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** M-q as `org-fill-paragraph`: paragraphs (also in items and greater blocks), comments and comment blocks, byte- and caret-exact against Emacs.

**Architecture:** `Fill.swift` ports `org-fill-element` and Emacs's `fill-region-as-paragraph` (fill.el): adaptive prefixes (`fill-context-prefix`, `fill-match-adaptive-prefix`, `org-adaptive-fill-function`, `org-adaptive-fill-paragraph-function`), `fill-delete-prefix`, `fill-delete-newlines`, `canonically-space-region`, `fill-move-to-break-point`, `fill-nobreak-p` with org's `paragraph-start` and its three no-break predicates, `fill-newline`. Elements come from the parser; quote, center and special blocks are parsed into their elements on demand, since the tree keeps blocks opaque.

**Tech Stack:** Swift 6.2 tools, Swift Testing, Emacs 31.1 / Org 9.8.7 oracle.

**Spec:** `docs/design.md`, "Goals" (`M-q` fill).

## Global Constraints

- `sentence-end-double-space` nil (the user's Doom setting), `colon-double-space` nil, `left-margin` 0, left justification, `adaptive-fill-mode` t.
- `fill-column` is an option: Emacs's 70 in the oracle's first pass, Doom's 80 in the second and as the app default.
- Src blocks are left alone: Emacs fills them through the language's mode and re-indents them on the way.

## Defaults chosen (user may change)

- Fill column 80 (Doom). Mac preset: ⌃⌘P.
- No CJK line breaking rules (kinsoku), no justification with C-u.

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### Task 1: Fill

- [ ] Port; oracle over 16 variants (items, comments, quotes, line breaks, timestamps, links, captions, markup at line start, extra spaces) at both fill columns, and over corpus paragraphs (src blocks excluded).
- [ ] Commit "Port fill paragraph".

### Task 2: App

- [ ] M-q / ⌃⌘P; Settings fill column.