Optimize full Android app native AI footprint before production release

[ucguy4u]

Problem

PR #225 restored green CI after the Flutter/Dart maintenance pass and re-enabled enforced APK size gates for the lean Android variants. However, the full Android app APK remains too large for production release readiness.

Latest CI size report from PR #225:

Variant	Artifact	Size	Gate	Status
mobile-streaming	app-arm64-v8a-release.apk	30.82 MiB	35 MiB	Passing
tv	app-arm64-v8a-release.apk	27.60 MiB	35 MiB	Passing
mobile-full	app-arm64-v8a-release.apk	439.92 MiB	report-only	Too large

The full app APK is dominated by native libraries:

mobile-full / app-arm64-v8a-release.apk breakdown
native libraries: 427.10 MiB
dex: 16.69 MiB
assets: 6.51 MiB
resources: 0.88 MiB

PR #225 intentionally made the full-app size check report-only so CI can stay green while lean variants remain protected. This issue tracks the follow-up work needed before treating the full app as production-release ready.

Context

Related PR: #225

PR #225 already completed:

• Upgraded CI to Flutter 3.41.4 / Dart 3.11.1.
• Fixed app analyzer/codegen blockers.
• Added CI-only Android release signing.
• Normalized arm64 APK output for size validation.
• Added build_runner clean before CI codegen.
• Added pdfx stub for lean variants.
• Excluded LiteRT native .so files from streaming/TV APK packaging based on APP_VARIANT.
• Restored passing lean APK gates:
  • Streaming: 30.82 MiB
  • TV: 27.60 MiB

The remaining production concern is the full app native AI footprint, especially LiteRT / on-device AI artifacts.

Scope

In scope:

• Measure exactly which native libraries account for the 427.10 MiB full-app native footprint.
• Decide whether full-app on-device AI should be bundled, downloaded on demand, split by flavor, or delivered through Play Feature Delivery / dynamic feature modules.
• Implement the selected production packaging strategy.
• Restore an enforced full-app size gate or create a documented production-specific gate if 35 MiB is no longer the correct target.
• Update CI, release docs, and any rollout notes.

Out of scope:

• Reverting PR ci: align Flutter SDK and clear core_ai analyzer hints #225's Flutter/Dart upgrade.
• Weakening streaming/TV APK gates.
• Removing on-device AI capability without an explicit product/architecture decision.
• Disabling security scans or release validation.

Suggested Investigation Plan

1. Generate a full release APK or AAB size breakdown using Android Studio APK Analyzer, apkanalyzer, or CI artifact inspection.
2. Identify all large .so files and their source Maven/package dependency.
3. Compare options:
   • Keep bundled and set a realistic full-app budget.
   • Move LiteRT/model runtime behind download-on-demand.
   • Split AI into a dedicated flavor or dynamic feature module.
   • Use Play Asset Delivery / Play Feature Delivery if suitable.
4. Validate install/startup behavior on target Android devices, especially Pixel 9 / on-device AI paths.
5. Update CI so the selected production artifact is enforced, not only reported.

Acceptance Criteria

• Full-app Android artifact strategy is documented in an ADR or release runbook.
• Native library breakdown is attached to this issue or linked from a PR.
• Production Android artifact target is explicit: APK, AAB, dynamic feature, or download-on-demand strategy.
• CI enforces the chosen production full-app size policy.
• Streaming and TV APK gates remain enforced and under 35 MiB.
• Full app build passes release signing validation in CI.
• flutter analyze --no-fatal-infos --no-fatal-warnings passes.
• Relevant Flutter/core package tests pass.
• Security scans remain green: Trivy/security-scan and Snyk.
• Release notes or docs explain any packaging/install behavior change.

Validation Commands / Checks

Use these as a baseline, adapting as needed for the selected packaging strategy:

cd app
flutter pub get
dart run build_runner clean
dart run build_runner build --delete-conflicting-outputs
flutter analyze --no-fatal-infos --no-fatal-warnings
flutter test --reporter=compact
flutter build apk --release \
  --target=lib/main.dart \
  --target-platform=android-arm64 \
  --dart-define=APP_VARIANT=full \
  --dart-define=APP_PLATFORM=mobileFull \
  --tree-shake-icons \
  --split-debug-info=build/debug-info-mobile-full \
  --obfuscate

CI checks to keep green:

• Continuous Integration / analyze
• Continuous Integration / lint
• Continuous Integration / test-core
• Continuous Integration / build-android matrix
• PR Checks / tests
• PR Checks / code-quality
• Security scan / Trivy
• Snyk
• SonarCloud
• Plugin Size Gate

Agent / Ownership

Primary agent: agent/performance

Supporting agents:

• agent/ci-cd for CI gates and release workflow.
• agent/ai-llm for on-device AI packaging decisions.
• agent/release for production artifact policy and release readiness.

Priority / Estimate

Priority: priority/P1

Estimate: 2-4 engineering days depending on whether the solution is CI budget re-baselining, dynamic delivery, or runtime download-on-demand.

Risks

• A naive size-gate increase could mask a poor production install experience.
• Removing bundled AI libraries could break Gemini Nano / LiteRT runtime paths if not feature-gated correctly.
• Dynamic delivery or download-on-demand changes can affect offline behavior and first-use latency.
• Release artifact choice may differ between GitHub APK validation and Play Store AAB distribution; document this explicitly.

[ucguy4u]

Required Before Implementation: Use Cases + Automation Flow

Before coding this ticket, add a deterministic implementation note or child task covering:

• Primary user journey: actor, preconditions, trigger, happy path, success state.
• Alternate/failure paths: offline, missing model, permission denied, runtime/tool failure, cancel/retry, background/foreground.
• Automation flow: Given/When/Then steps, fixtures, mocks/stubs, UI assertions, state/database assertions, notification/tool-trace/memory assertions where relevant.
• Hardening checks: privacy redaction, accessibility, timeout/performance bounds, cleanup/reset.
• Delegation prompt: Ask a QA/test agent to write the automation flow before implementation begins.

Tracker: #323