Chapter Briefs Skill for Codex

Chapter Briefs (H2 writing cards) [NO PROSE]

Purpose: turn each H2 chapter that contains H3 subsections into a chapter-level writing card so the writer can:

• add a chapter lead paragraph block (coherence)
• keep a consistent comparison axis across the chapter
• avoid “8 small islands” where every H3 restarts from scratch

This artifact is internal intent, not reader-facing prose.

Why this matters for writing quality:

• Chapter briefs prevent the "paragraph island" failure mode: without a throughline, each H3 restarts and repeats openers.
• Treat throughline and lead_paragraph_plan as decision constraints, not copyable sentences.

Inputs

• outline/outline.yml
• outline/subsection_briefs.jsonl
• Optional: GOAL.md

Outputs

• outline/chapter_briefs.jsonl

Output format (outline/chapter_briefs.jsonl)

JSONL (one object per H2 chapter that has H3 subsections).

Required fields:

• section_id, section_title
• subsections (list of {sub_id,title} in outline order)
• synthesis_mode (one of: clusters, timeline, tradeoff_matrix, case_study, tension_resolution)
• synthesis_preview (1–2 bullets; how the chapter will synthesize across H3 without template-y “Taken together…”)
• throughline (3–6 bullets)
• key_contrasts (2–6 bullets; pull from each H3 contrast_hook when available)
• lead_paragraph_plan (2–3 bullets; plan only, not prose)
• Each bullet should be chapter-specific and mention concrete handles (axes / contrast hooks / evaluation lens).
• Avoid generic glue like "Para 1: introduce the chapter" without naming what is being compared.
• bridge_terms (5–12 tokens; union of H3 bridge terms)

How C5 uses this (chapter lead contract)

The writer uses outline/chapter_briefs.jsonl to draft sections/S<sec_id>_lead.md (body-only; no headings).

Contract (paper-like, no new facts):

• Preview the chapter’s comparison axes (2–3) and how the H3s connect; do not restate the table of contents.
• Reuse key_contrasts / bridge_terms as *handles* (not templates) so the chapter reads coherent without repeating "Taken together" everywhere.
• Keep it grounded (>=2 citations later in C5; do not invent new papers here).

Workflow

• (Optional) Read GOAL.md to pin scope/audience, and inject that constraint into the chapter throughline.
• Read outline/outline.yml and list H2 chapters that have H3 subsections.
• Read outline/subsection_briefs.jsonl and group briefs by section_id.
• For each chapter, produce:
• a throughline: what the whole chapter is trying to compare/explain
• key contrasts: 2–6 contrasts that span multiple H3s
• a synthesis_mode: enforce synthesis diversity across chapters (avoid repeating the same closing paragraph shape)
• a lead paragraph plan: 2–3 paragraph objectives (what the chapter lead must do)
• a bridge_terms set to keep terminology stable across H3s
• Write outline/chapter_briefs.jsonl.

Quality checklist

• [ ] One record per H2-with-H3 chapter.
• [ ] No placeholders (TODO/…/(placeholder)/template instructions).
• [ ] throughline and key_contrasts are chapter-specific (not copy/paste generic).
• [ ] lead_paragraph_plan bullets explicitly preview 2–3 comparison axes and how the H3 subsections partition them (no generic chapter-intro boilerplate).

Script

Quick Start

• uv run python .codex/skills/chapter-briefs/scripts/run.py --help
• uv run python .codex/skills/chapter-briefs/scripts/run.py --workspace <workspace>

All Options

• --workspace <dir>
• --unit-id <U###>
• --inputs <semicolon-separated>
• --outputs <semicolon-separated>
• --checkpoint <C#>

Examples

• Default IO:
• uv run python .codex/skills/chapter-briefs/scripts/run.py --workspace <workspace>
• Explicit IO:
• uv run python .codex/skills/chapter-briefs/scripts/run.py --workspace <workspace> --inputs "outline/outline.yml;outline/subsection_briefs.jsonl;GOAL.md" --outputs "outline/chapter_briefs.jsonl"

Refinement marker (recommended; prevents churn)

When you are satisfied with chapter briefs, create:

• outline/chapter_briefs.refined.ok

This is an explicit "I reviewed/refined this" signal:

• prevents scripts from regenerating and undoing your work
• (in strict runs) can be used as a completion signal to avoid silently accepting a bootstrap scaffold

Notes

• This helper is a bootstrap; refine manually if needed.