Castamatic 13: On-Device Intelligence for Podcasts

Castamatic 13 is here, and it’s the biggest update since the app launched in 2015. This release introduces Magic Transcript and Magic Chapters — two features that use Apple Intelligence to generate transcripts and chapters entirely on your device. No cloud, no upload, no data leaving your phone. Ever.

Magic Transcript

Castamatic can now generate a full transcript for any downloaded episode, directly on your device using Apple’s Speech framework. Multi-language support is built in — the app detects the podcast’s language automatically.

Once generated, the transcript appears in a new Transcript Panel built into the player. It scrolls in real time as the episode plays, highlighting the current line. Tap any sentence to jump to that exact moment. The panel includes full transport controls — play/pause, skip, and chapter navigation — so you never lose your place.

Magic Chapters

This is the feature I’m most excited about. Most podcasts — especially long-form conversations and interviews — don’t include chapter markers. If you want to find a specific segment in a two-hour episode, you’re stuck scrubbing back and forth.

Castamatic 13 solves this. Magic Chapters generates chapter markers automatically using a multi-stage on-device AI pipeline:

1. A local sentence-embedding model running on the Neural Engine analyzes the transcript and detects topic changes by comparing semantic similarity across sliding windows.
2. Episode and podcast descriptions are used to identify key topics and reinforce boundary detection.
3. Apple’s Foundation Models framework generates concise, descriptive chapter titles.

The result: any downloaded episode can have navigable chapters in minutes. Apple Podcasts recently introduced server-generated chapters — Castamatic takes the opposite approach, running the entire pipeline on-device, privately and offline.

Publisher-First

When a podcast already includes published chapters or a transcript, Castamatic uses the publisher’s data. Magic generation is only offered when there’s nothing to work with.

Privacy by Design

Both features process audio locally using Apple Intelligence. No audio, transcript, or metadata is sent to any server. It works completely offline once an episode is downloaded.

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Castamatic 13 is available now on the App Store.

Happy listening!