diff --git a/scripts/instrumented.sh b/scripts/instrumented.sh
index 34e210f..d7e70d0 100755
--- a/scripts/instrumented.sh
+++ b/scripts/instrumented.sh
@@ -66,14 +66,38 @@ if ! "$ADB" shell getprop sys.boot_completed 2>/dev/null | grep -q 1; then
     -no-snapshot-load -no-snapshot-save -no-boot-anim \
     -netdelay none -netspeed full >/tmp/fnmsg-emu.log 2>&1 &
   until "$ADB" shell getprop sys.boot_completed 2>/dev/null | grep -q 1; do sleep 5; done
-else
-  echo "### emulator already up, clearing the app rather than trusting it"
-  "$ADB" uninstall io.flamenet.messenger >/dev/null 2>&1 || true
-  "$ADB" uninstall io.flamenet.messenger.test >/dev/null 2>&1 || true
 fi
 
-echo "### signed-in account on the device before we start:"
-"$ADB" shell pm list packages 2>/dev/null | grep -i flamenet || echo "    (nothing installed, good)"
+# Unconditionally, on BOTH paths. This uninstall used to live only in the
+# "emulator already up" branch, on the reasoning that a cold boot starts clean.
+# A cold boot starts with no SNAPSHOT; the disk image keeps whatever was
+# installed on it. So an AVD that had been used to test a RELEASE build kept
+# that build, and the debug APK could not install over it:
+#
+#   INSTALL_FAILED_UPDATE_INCOMPATIBLE: Existing package
+#   io.flamenet.messenger signatures do not match newer version
+#
+# Release and debug are signed by different keys, which is the whole point of
+# them, so this is not a rare collision: it happens every time somebody uses
+# this AVD to try a real build, which is what an AVD is for.
+#
+# The line below already PRINTED the leftover package, and the run continued
+# anyway. A check whose output nobody acts on is decoration.
+"$ADB" uninstall io.flamenet.messenger >/dev/null 2>&1 || true
+"$ADB" uninstall io.flamenet.messenger.test >/dev/null 2>&1 || true
+
+echo "### installed packages after clearing:"
+LEFTOVER=$("$ADB" shell pm list packages 2>/dev/null | grep -i flamenet || true)
+if [ -n "$LEFTOVER" ]; then
+  echo "$LEFTOVER"
+  echo "REFUSED: could not remove the existing install above." >&2
+  echo "It will make the test APK fail to install, and the run would report" >&2
+  echo "zero tests as though nothing were wrong. Remove it by hand:" >&2
+  echo "  $ADB uninstall io.flamenet.messenger" >&2
+  exit 1
+else
+  echo "    (nothing installed, good)"
+fi
 
 echo "### relay $RELAY  ·  classes $CLASSES"
 set +e