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EPUB and KEPUB derivatives

Renderflow models EPUB and KEPUB as provider-neutral artifact formats. Pandoc generates reflowable EPUB 3 from documents. The exact native fixed-layout EPUB route packages a bounded ordered PNG or JPEG collection. KEPUB is a separate epub -> kepub graph edge backed by Kepubify for the established reflowable path; its provider and fallback remain visible in the execution plan and provenance.

Generate derivatives

Legacy configuration accepts both document outputs:

input: manuscript.md
variables:
  title: Example publication
  author: Example Author
  language: en
  identifier: urn:uuid:replace-me
  rights: Copyright holder and license statement
outputs:
  - type: epub
  - type: kepub

Document-source spec v2 callers can request format: epub or format: kepub. That KEPUB branch reuses the reflowable EPUB artifact and only runs Kepubify after EPUB generation. Final KEPUB files use the conventional .kepub.epub suffix. Ordered image collections use the separate exact EPUB target and execution.fixed_layout_epub policy described in the fixed-layout guide.

An EPUB output's optional template field names an OPF metadata fragment under the configured template directory and is passed to Pandoc as --epub-metadata. The title, subtitle, author/creator, language/lang, identifier, date, rights, and description variables are also mapped to internal EPUB metadata. Canonical source metadata remains preferable.

Inspect and validate

renderflow ebook inspect --input "dist/book.epub" --format json
renderflow ebook inspect --input "dist/book.epub" --fixed-layout --format json --epubcheck
renderflow ebook inspect --input "dist/book.epub" --run-manifest "dist/renderflow-run.json" --format json
renderflow ebook capabilities --format yaml

The fixed-layout generation capability is scoped to the exact bounded ordered PNG/JPEG collection route, selected through the virtual tool.renderflow-epub provider. The ebook capabilities summary and generated conformance matrix must be read with that route constraint: they do not claim arbitrary document-to-fixed-layout conversion, SVG input, or fixed-layout KEPUB. Pandoc's reflowable document path remains separate.

Native inspection validates the EPUB container and EPUB 3 package envelope and reports XHTML content, internal title/language/identifier/creator/rights metadata, navigation, page-list, layout declarations, accessibility metadata, and KEPUB markers. For the exact native fixed-layout route, the fixed-layout evidence is validated, invalid, or unsupported with typed diagnostics. Pass --run-manifest to check that the inspected bytes match the recorded output and provenance (verified, stale, or corrupt). Failed binding marks the inspection invalid. Evidence is versioned as renderflow.ebook-evidence/v1 and includes the immutable source SHA-256 digest.

When requested, the optional EPUBCheck v5 provider runs locally through Renderflow's bounded process service and embeds its result, including provider identity and the observed executable version when available. A missing EPUBCheck is recorded as unavailable and the requested CLI command exits nonzero. It is never represented as a pass. Native inspection and EPUBCheck conformance evidence are separate decisions.

Capability boundaries

The bundled Pandoc path generates reflowable EPUB 3. The bundled Kepubify path generates reflowable KEPUB from EPUB. The native ordered-image route generates fixed-layout EPUB packages with a pre-paginated declaration and explicit page order. It does not establish fixed-layout KEPUB support. Native inspection recognizes rendition:layout declarations and reports fixed-layout and mixed publications; the exact fixed-layout route additionally requires checked package/member relationships and page evidence.

The exact fixed-layout validator checks the declared page-list and accessibility relationships rather than inferring them from an EPUB ZIP extension. The presence of descriptions and metadata does not prove complete accessibility for visually rich pages. EPUB 3.3 conformance requires successful EPUBCheck evidence; native structural validity alone makes no such claim.

Retailer acceptance is deliberately outside this generic format capability. Every inspection reports requires_provider_profile; Lulu, Kobo, or another channel pack must evaluate its own current restrictions before calling an artifact upload-ready.

Provider decision

Kepubify is adopted as the focused KEPUB provider: it is standalone, cross-platform, local, and MIT-licensed. Calibre remains deferred as a broader fallback because its larger conversion surface and output variation need a separate adapter and conformance case. EPUBCheck is adopted as the authoritative external conformance provider alongside Renderflow's deterministic native structural inspection.

References