0008 — Dual output modes: .mp4 video and editable .pptx deck

• Status: Accepted (2026-09)
• Drivers: teachers want a video to share AND a deck to present live; the artwork/narration work is identical for both

Decision

create selects its pipeline tail by output extension (src/slide_stream/export_pptx.py, cli.py):

• .mp4 (default): the full video pipeline — TTS audio, avatar, fragments, ffmpeg assembly.
• .pptx: same per-slide pipeline up through artwork + final narration text, then stops. export_pptx writes native slides (title, bullets, artwork fitted right, bullets left) with the narration in the speaker notes — no TTS, no avatar, no ffmpeg.

PPTX stays input-only for draft/parse; this ADR covers output only.

Consequences

• One narration code path (LLM / --script / --verbatim-notes) feeds both outputs, so wording never diverges between the video and the deck.
• Strict-mode narration failures abort a pptx export the same as a video.
• The exporter is deliberately dumb: layout is fixed (artwork right, bullets left) and theme comes from PowerPoint defaults; fancy deck design is out of scope — the pptx is a starting point the teacher edits.