Verifying a minified Android release without a device

assembleRelease exiting 0 proves almost nothing. R8 failures are runtime failures, and the debug build can never reveal them. These checks all run with no device attached.

1. The ServiceLoader engine trap (highest value)

Libraries that resolve an implementation via ServiceLoader break under R8 because the META-INF/services/* entries get renamed. Symptom: works in every debug build, the whole feature dies in release.

Check what the APK actually contains:

python - <<'PY'
import zipfile
z = zipfile.ZipFile("app/build/outputs/apk/release/app-release-unsigned.apk")
print([n for n in z.namelist() if "META-INF/services" in n])
PY

Renamed entries (META-INF/services/ad0, an1, …) mean discovery is in play.

Fix by removing the discovery, not by adding keep rules. For supabase-kt, the ktor engine is discovered unless named explicitly:

createSupabaseClient(url, key) {
    install(Auth); install(Postgrest)
    httpEngine = OkHttp.create()   // compile-time reference; R8 cannot lose it
}

The engine artifact (io.ktor:ktor-client-okhttp) is usually already a dependency — check before adding one.

2. Dex probing: did R8 strip what the app needs?

Concatenate the dex files and grep for names that MUST survive:

python - <<'PY'
import zipfile
z = zipfile.ZipFile("app/build/outputs/apk/release/app-release-unsigned.apk")
dex = b"".join(z.read(n) for n in z.namelist() if n.endswith(".dex"))
for p in [b"$$serializer", b"YourDto", b"okhttp3", b"OkHttpEngine", b"YourDatabase_Impl"]:
    print(p.decode(), "KEPT" if p in dex else "MISSING", dex.count(p))
PY

Interpretation matters:

• @Serializable DTOs and $$serializer classes must appear — kotlinx keep rules preserve those names. Absent = decoding will fail at runtime.
• A missing ordinary class name is not evidence of removal — R8 renames everything not covered by a keep rule. Only conclude "stripped" for names that a keep rule was supposed to preserve.

3. Keep rules: source them, don't invent them

Most libraries ship consumer rules inside the artifact; read them instead of guessing:

unzip -p ~/.gradle/**/kotlinx-serialization-core-jvm-*.jar 'META-INF/proguard/*'
unzip -p ~/.gradle/**/ktor-utils-jvm-*.jar 'META-INF/proguard/*'

If a library ships none (supabase-kt does not), it usually relies on another library's rules — scope your own rule to your package rather than writing -keep class ** { *; }, which silently disables shrinking.

4. Prove the release credential gate fires

A release that ships blank backend keys "works" and is dead at runtime. If you add a fail-fast gate, test the negative case, reversibly:

cp local.properties /tmp/lp.bak
# blank the keys, then:
./gradlew :app:assembleRelease   # expect failure with your message
cp /tmp/lp.bak local.properties  # restore, then verify the keys are back

Always verify restoration — a missed restore silently breaks later builds.

5. The androidTest blind spot

assembleDebug does not compile src/androidTest. Instrumented tests written by anyone (including an agent) can be committed broken and unnoticed:

./gradlew :app:assembleDebugAndroidTest   # compiles + packages, no device needed

Also build the store artifact, which exercises a different path from the APK: ./gradlew :app:bundleRelease.

6. Lint triage via SARIF, not the HTML report

Run ./gradlew :app:lintRelease (a flavoured app runs :app:lint<Flavour>Release and writes lint-results-<flavour>Release.sarif) and triage the SARIF with the script in android-release-readiness-audit section 2, never the HTML report.

Judgement calls worth keeping:

• UnusedResources on hand-made art is usually a feature gap (assets built, never wired), not dead weight. Wire it or report it; don't delete silently.
• ModifierParameter "should be the first optional parameter" is pure convention when all call sites use named arguments — low value, real churn.
• Lint objecting to a documented, deliberate non-plain Modifier default (e.g. a scroll container that must not receive infinite height) should be left alone; changing it alters layout at every call site.
• Fixing DefaultLocale with Locale.getDefault() inside a @Composable trades a warning for the NonObservableLocale error. Use Compose's observable locale instead, after confirming the API exists in the pinned artifact: androidx.compose.ui.text.intl.Locale.current.platformLocale.

What still needs a device

Nothing above proves the app runs. After the checks pass, still require: connectedDebugAndroidTest, and installing a debug-signed copy of the release APK to exercise the network/serialization paths. Say so plainly rather than implying the release is verified.