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Audiobook generator and reader powered by Kokoro TTS.

Built around a Kokoro TTS chapter generator and a mobile-first TypeScript reader for long-form chapter audio, offline downloads, and Cloudflare delivery.

Live demo

Highlights

• Mobile-first playback: a persistent bottom dock keeps chapter movement, seek controls, play/pause, elapsed time, remaining time, and downloads within thumb reach.
• Passage-synced listening: generated timing data drives current-passage highlighting, seek restoration, saved progress, replay, and readable autoscroll behavior.
• Offline by design: upcoming chapters can be predownloaded automatically, cached audio supports range playback, and users can clear downloaded chapter assets from the app.
• Static where it matters: chapter pages are generated ahead of time with embedded timing data, pre-rendered reading markup, hashed app assets, and a lazily loaded chapter catalog.
• Deployment-aware: Cloudflare Workers serve the app shell while private R2 audio objects are streamed through validated, content-addressed routes.
• Behavioral coverage: Cucumber feature files describe listener workflows, and Playwright-backed steps exercise playback, navigation, offline downloads, and responsive layout.

Stack

• App: TypeScript, Bun, Zod v4, Lucide icons, scroll-into-view-if-needed, native media elements, IndexedDB, Cache API, and service worker registration.
• Build and delivery: Bun scripts, Workbox-generated service worker, Wrangler, Cloudflare Workers Static Assets, and Cloudflare R2.
• Audio generation: Python, uv, Kokoro TTS, Torch, SoundFile, ffmpeg, WebM/Opus primary audio, M4A/AAC fallback audio, and alignment manifests.
• Testing: Cucumber, Playwright, TypeScript compile checks, deploy artifact validation, and Python compile checks.

What the App Does

• Opens stable chapter routes such as /1/ and restores per-chapter progress.
• Lets listeners search, browse, and jump across a large chapter catalog without rendering every row at once.
• Keeps passage following in sync with native audio playback, seeking, skip back 15 seconds, and skip forward 30 seconds.
• Generates a compact catalog containing source URLs, MIME types, byte sizes, hashes, and audio version metadata.
• Serves hashed audio paths such as /1-0123456789abcdef.webm and /1-0123456789abcdef.m4a through a Worker that supports GET, HEAD, byte ranges, immutable cache headers, and clear failure responses.
• Validates generated chapter data and deployment output with Zod before the app or deploy scripts trust it.