Summarize a document with extractive and abstractive modes and short/medium/long length presets, rendered in a split pane with input/summary word counts, a compression-ratio badge and bar, and a reading-time-saved estimate. On the Transformers.js path abstractive is served by DistilBART and extractive by a real on-device sentence-extraction algorithm drawing sentences verbatim from the source; Chrome summary styles are offered only when the Chrome Summarizer API actually serves the block. Resolves Chrome Built-in AI when available and falls back automatically behind an explicit download gate, with a truthful provider badge. No model bytes download until an explicit in-block action.