Behavioral Changes Must Be MobileConfig-Gated

Severity: HIGH — Ungated changes to shared image loading infrastructure cannot be rolled back without a new release

What to Look For

• Changes to image loading behavior (decode, fetch, cache, render)
• Modified return values or control flow in producer chain
• New code paths in KFrescoController, FrescoController2Impl, or ImagePipeline
• Changed cache eviction logic or memory pool behavior

When to Flag

• Behavioral change in shared code without config.useNewBehavior / MC flag guard
• New code path that is always-on with no way to disable
• Modified producer behavior without experiment gating

Do NOT Flag

• Bug fixes that restore correct behavior (no gating needed)
• Test-only changes
• Documentation or comment changes
• Changes already inside an existing MC flag guard

Examples

// BAD — Always-on behavioral change, can't roll back
fun fetch(request: ImageRequest): DataSource<CloseableReference<CloseableImage>> {
    return newFetchImplementation(request)  // ❌ No way to revert without code push
}

// GOOD — Gated with MC flag, can be disabled server-side
fun fetch(request: ImageRequest): DataSource<CloseableReference<CloseableImage>> {
    return if (config.useNewFetchImplementation) {
        newFetchImplementation(request)  // ✅ Can be disabled via MC
    } else {
        existingFetchImplementation(request)
    }
}

Evidence

• Recurring review pattern from oprisnik across 20+ fresco diffs (Dec 2025 - Mar 2026)
• D96566942: MC-gated hot path optimization
• D90468548: MC-gated postprocessor prefetch behavior