Authoring OPF with an LLM

Write a complete JSON document with name and slides. Put visible words in slide fields, not presentation metadata. Use *.opf.json filenames and stable, unique slide id values when a deck will be revised repeatedly.

{
  "name": "Launch decision",
  "slides": [{
    "id": "recommendation",
    "title": "Launch to the pilot group first",
    "composition": { "mode": "row", "weights": [2, 1] },
    "blocks": [
      { "items": ["Validate onboarding", "Measure activation", "Fix the largest drop-off"] },
      { "metric": { "value": 200, "label": "Pilot customers" } }
    ],
    "notes": "Confirm the rollout owner and checkpoint date."
  }]
}

Choose one content structure per slide:

• Root payloads for a simple slide: text, items, image, chart, table, code, metric, quote, or timeline.
• blocks for a sequence that should reflow. Set composition only when an arrangement matters. Omit it to let the engine choose.
• Promoted regions such as left, center+right, top, and bottom for spatially meaningful content. Regions must not overlap. Do not mix regions with root payloads or blocks.

Use catalog IDs from the installed package or supply inline records in catalogs. A gallery route is a stable identifier, but an extended gallery layout may need the inline record included in the copied document. Do not invent an unresolvable layout or assume a network lookup will happen.

Tables use { "columns": ["Category", "Value"], "rows": [["A", 10]] }. Charts put a type and the same tabular structure inside chart.data. Images use a source string or { "src": "...", "alt": "..." }; use the top-level assets registry and asset:<id> references for reuse. The local renderer does not fetch remote sources.

Revision loop#

1. Validate with validatePresentation. Fix errors at their returned JSON paths. Check warnings for unknown catalog IDs.
2. Render with onDiagnostic and inspect text-overflow / small-cell paths. Shorten text, reduce the number of blocks, change composition, or explicitly split the slide. Revalidate after edits.
3. Use composition.overflow: "error" for a strict text-layout gate. It does not certify chart readability, font availability, or exact PowerPoint rendering.
4. Inspect the actual preview and exported PPTX. Geometry is shared; font substitution and specialized objects can still differ.
5. Apply focused JSON Patch edits through the editor session and retain undo history. Resolve stable slide IDs to current array indices before constructing patches; indices can change when slides are inserted or moved.

Preserve factual content, sources, notes, and asset descriptions during layout repair. A fit diagnostic is a request to revise the slide; it is not permission to silently drop the end of a paragraph.

See dynamic composition, content payloads, and design precedence.

Use nested blocks to keep related content together. Put composition on the group to arrange its children, for example a column of evidence inside a row of sections. Read composeSlide().groups for group bounds and items[].path for precise leaf edits. Groups inherit readability constraints; splitting content into more levels does not make text smaller.

Use paginatePresentation(deck) when a draft exceeds readable space. Review the returned ordinary OPF slides and source mappings before export. Pagination preserves source text exactly; it does not summarize or rewrite it. An atomic item that cannot fit produces a diagnostic for a targeted edit.