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catacomb/docs/superpowers/specs/2026-06-27-android-engine-feasibility-findings.md
Luna 11b6679b29 docs(android-spike): Q3 POT/Proof-of-Origin findings + verdict (RISKY) 
The pivotal gate does NOT block: POT is required on mobile, but WebView-based
BotGuard token generation (proven in YTDLnis) is the durable path and collapses
the JS-runtime + POT problems into one, killing the Deno/Node sidecar.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-27 02:33:23 -07:00

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Android Engine Feasibility — Findings

Companion to 2026-06-27-android-engine-feasibility-research.md. Each section ends with a verdict: proven / risky / unsolved.

Q1 — yt-dlp on Android

Verdict: RISKY. yt-dlp runs on-device in shipping apps (Seal, YTDLnis, SealPlus) — proven. But Catacomb's specific need is the asterisk: curl_cffi TLS impersonation is documented broken on Android (yt-dlp issues #15505 Jan 2026 and #14106 aarch64 Linux), and impersonation is the exact reason Catacomb pins nightly yt-dlp. The yt-dlp binary update story is good — youtubedl-android (yausername) exposes UpdateChannel.NIGHTLY to pull fresh builds post-install, no app-store release, across all four ABIs. Chaquopy is ruled out: no runtime update path.

  • Recommended mechanism: youtubedl-android (only approach with runtime nightly updates + production proof).
  • Risk carried forward: the anti-bot layer (impersonation + the Deno-based bgutil POT loopback, which has no Android port) needs a rethink — feeds Q2/Q3.
  • Full evidence + sources: q1-yt-dlp-android-report.md.

Q2 — JS runtime (deno's job)

Verdict: RISKY. An external JS runtime is now a hard dependency — yt-dlp deprecated its built-in Python jsinterp for YouTube in 2025.11.12 because YouTube's n-sig/PO-token JS exceeds what it can handle, so "no Deno on Android" cannot be sidestepped by the pure-Python path. A concrete on-device path exists: cross-compile QuickJS-ng via NDK (arm64-v8a, NDK 26+) and pass --js-runtimes quickjs:/path/to/qjs; or use HLahwani/yt-dlp-android (May 2026), a purpose-built lib already embedding QuickJS via JNI across all four ABIs (~1.6 MB AAR). It's "risky" because this is the live breakage frontier — Seal users have hit 403/missing-format bugs since Jan 2026 on the deprecated path.

  • Recommended approach: QuickJS-ng (--js-runtimes quickjs:...), or adopt HLahwani/yt-dlp-android which bundles it.
  • Note vs Q1: this newer lib may supersede youtubedl-android as the mechanism since it solves Q1+Q2 together — weigh in synthesis.
  • Full evidence + sources: q2-js-runtime-android-report.md.

Q3 — POT / Proof-of-Origin

Verdict: RISKY (the go/no-go gate — and it does NOT block). POT is required on the mobile surface; you can't reliably skip it for a general archiver. The shortcut clients are closing: android_vr dropped to 360p (SABR A/B, Mar 2026) and tv was removed from yt-dlp defaults after YouTube enforced LOGIN_REQUIRED. But there is a production-proven path that is strictly better than Catacomb's desktop design: YTDLnis (since v1.8.3, Mar 2025) runs YouTube's BotGuard JS challenge inside the Android WebView and passes the resulting web GVS PO token to yt-dlp as an extractor arg. This collapses Q2 and Q3 into one mechanism — the WebView is the JS runtime — and eliminates the Deno/Node sidecar entirely.

  • Recommended anti-bot approach: WebView-based BotGuard/POT generation (à la YTDLnis), no sidecar.
  • Caveats: tokens are video-bound + ~12h-lived (a WebView attestation call per download); native android-client DroidGuard tokens remain unsolved (no open tooling outside genuine Play Services). Fragile cat-and-mouse — must track YouTube changes.
  • Flagged-for-device: actual token minting + a real download need a device/ WebView/Google session; not reproducible headlessly here.
  • Full evidence + sources: q3-pot-android-report.md.

Q4 — Rust core via JNI

pending

Synthesis — go / no-go

pending