presentations

Presentations

Two paths produce a PPTX, and picking the wrong one destroys work. Choose first, then follow that path's section, and finish with the validation section — it applies to both.

Which path

• An existing .pptx is in play — a template, a deck the user uploaded, a prior version of this deliverable, a downloaded starting point — edit it in place with the XML pipeline below. Always. The edit path is Python + the bundled helpers; it does not need Node.
• Nothing exists yet and there is no template — generate a new deck. Prefer pptxgenjs when Node and npm are actually usable; fall back to python-pptx when they are not. Detect before you write the generator (see below) — do not assume either runtime from the skill name alone.

Never rebuild an existing deck to apply a change. Regenerating a deck re-authors every slide: the master, theme, fonts, colors, logos, footers, and every slide you did not think to re-emit are gone, silently, and the user sees a deck that no longer looks like theirs. A one-line text fix is a one-line XML edit, not a rewrite. Equally, never recreate from scratch what a template already provides — if the user handed you a template, its design is the requirement.

New decks: detect the runtime first

Before writing a generator, decide Node vs Python carefully. Do not spend turns on npm install or a pptxgenjs script when node/npm are truly missing — that is how runs burn steps and then redo the deck in Python. Also do not treat every failed probe as "Node is gone for the turn."

1. Read this turn's operating notes (the environment / capability lines injected into the prompt). Gate the fallback on note state first:
   • Node is unavailable → skip Node entirely; use the python-pptx path (install may still need package-manager network policy).
   • Node is being installed → do work that does not need Node, then recheck later in the turn. Do not start the python-pptx path on the first failed probe while install is in progress. If Node still does not run after a later recheck, say so and only then take the python-pptx path (or a markdown outline with the user's knowledge) — do not silently switch generators mid-turn.
   • Node is available, or the notes are silent about Node → continue to step 2. Notes can lag a managed image or a host that lost its toolchain; they do not replace a real binary check, and a probe always overrides a stale "available" claim.
2. Probe the binaries once in a single exec (no package install yet), unless step 1 already sent you to python-pptx because Node is unavailable: