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14. Pack: slides.render

Status: Accepted Date: 2026-04-07 Domain: api-design

Context​

Rendering Markdown decks to PDF/PPTX/HTML normally requires Marp CLI, a headless Chromium, temp directories, and format-specific flags — multi-step shell knowledge that weak models cannot reliably drive (PRD §6.6).

Decision​

Ship slides.render as a built-in pack.

Input: { markdown: string, format: "pdf"|"pptx"|"html", theme?: string } Output: { artifact_url: string, format: string, page_count: integer } Errors: schema_mismatch, timeout, internal_error

The handler runs Marp inside a session container, captures the artifact, uploads it to the configured object store (see ADR 031 for the backend choice — Garage as the bundled Compose default, pluggable to any S3-compatible endpoint), and returns a signed URL. Theme defaults to default. Marp and Chromium are baked into the browser sidecar image.

Consequences​

Positive: any agent gets slide rendering as one typed call. Negative: Marp/Chromium added to base image (~120 MB).

§6.6 Capability Packs