diff --git a/docs/manual/cli.md b/docs/manual/cli.md
index bc03a45..1e607ff 100644
--- a/docs/manual/cli.md
+++ b/docs/manual/cli.md
@@ -18,7 +18,7 @@ Run a spec against an app for a fixed duration.
 | `--bundle-id` | required | Target app bundle ID (Android: applicationId). |
 | `--launcher-activity` | resolved | Optional `<pkg>/<activity>` to launch. Overrides default resolution. |
 | `--platform` | `android` | Target platform. Only `android` in the current alpha. |
-| `--avd` | required (android) | Android AVD name. |
+| `--avd` | optional (android) | Android AVD name to boot if no device is connected. Required only when no device is connected and multiple AVDs exist. |
 | `--duration` | `5m` | Total test duration (`30s`, `5m`, `2h`, `1d`). |
 | `--seed` | `0` | PRNG seed. `0` uses a random seed and records it in `meta.json`. |
 | `--output` | `./runs` | Output directory for traces. |
diff --git a/docs/manual/getting-started.md b/docs/manual/getting-started.md
index 2249df0..898f937 100644
--- a/docs/manual/getting-started.md
+++ b/docs/manual/getting-started.md
@@ -59,10 +59,11 @@ uatu test \
   --spec spec.ts \
   --bundle-id dev.uatu.sample \
   --platform android \
-  --avd Pixel_7 \
   --duration 2m
 ```
 
+Pass `--avd <name>` only when no device is connected and you have multiple AVDs; otherwise uatu uses the connected device or boots the single AVD it finds.
+
 When the run ends, the trace lands in `runs/<timestamp>/`:
 
 ```
diff --git a/docs/manual/runs.md b/docs/manual/runs.md
index 91542d1..1f0441c 100644
--- a/docs/manual/runs.md
+++ b/docs/manual/runs.md
@@ -11,7 +11,7 @@ A run is not analogous to a unit test. A closer framing is: boot a fuzzer for an
 ## Lifecycle
 
 ```
-uatu test --spec spec.ts --bundle-id com.example.app --avd Pixel_7 --duration 30m
+uatu test --spec spec.ts --bundle-id com.example.app --duration 30m
   │
   ├── uninstall and reinstall the app (clean slate, every run)
   ├── boot the sidecar, connect the agent socket
diff --git a/examples/sample-app/README.md b/examples/sample-app/README.md
index eed65af..9f58a77 100644
--- a/examples/sample-app/README.md
+++ b/examples/sample-app/README.md
@@ -47,4 +47,4 @@ Traces land in `./runs/<timestamp>/`.
   registers snapshot extractors (`app_state`, `click_count`)
 - `spec.ts` imports `@uatu/spec` (see `package.json`), reads those snapshots,
   asserts properties on them, and weights the actions the fuzzer picks from
-- `just test` invokes `uatu test` against the installed APK on the named AVD
+- `just test` invokes `uatu test` against the installed APK on the connected device (or the AVD named via `AVD=`)
diff --git a/internal/runner/runner.go b/internal/runner/runner.go
index 2ce99b3..4da598a 100644
--- a/internal/runner/runner.go
+++ b/internal/runner/runner.go
@@ -79,8 +79,12 @@ func Run(ctx context.Context, options Options) (Summary, error) {
 		if err := options.Verifier.PushSnapshot(verifier.Snapshots(snapshot.Snapshots), tree); err != nil {
 			return summary, fmt.Errorf("step %d push: %w", stepIndex, err)
 		}
+		screen, screenErr := screenFromSnapshot(snapshot.Snapshots)
+		if screenErr != nil {
+			fmt.Printf("warning: step %d screen: %v\n", stepIndex, screenErr)
+		}
 		fmt.Printf("step %d: screen=%q hierarchy=%d nodes\n",
-			stepIndex, screenFromSnapshot(snapshot.Snapshots), treeSize)
+			stepIndex, screen, treeSize)
 		verdicts := options.Verifier.EvaluateProperties()
 		violations := violationNames(verdicts)
 
@@ -95,7 +99,7 @@ func Run(ctx context.Context, options Options) (Summary, error) {
 		step := trace.Step{
 			Index:      stepIndex,
 			Timestamp:  stepStart,
-			Screen:     screenFromSnapshot(snapshot.Snapshots),
+			Screen:     screen,
 			Snapshots:  snapshot.Snapshots,
 			Action:     traceAction,
 			Violations: violations,
@@ -175,14 +179,16 @@ func violationNames(verdicts map[string]ltl.Verdict) []string {
 	return names
 }
 
-func screenFromSnapshot(snapshots map[string]json.RawMessage) string {
+func screenFromSnapshot(snapshots map[string]json.RawMessage) (string, error) {
 	raw, ok := snapshots["screen"]
 	if !ok {
-		return ""
+		return "", nil
 	}
 	var screen string
-	_ = json.Unmarshal(raw, &screen)
-	return screen
+	if err := json.Unmarshal(raw, &screen); err != nil {
+		return "", err
+	}
+	return screen, nil
 }
 
 func applyAction(ctx context.Context, drv driver.Driver, action verifier.Action, tree *hierarchy.Tree) error {
diff --git a/internal/runner/runner_test.go b/internal/runner/runner_test.go
index 98e6b91..e5cf9d5 100644
--- a/internal/runner/runner_test.go
+++ b/internal/runner/runner_test.go
@@ -235,6 +235,38 @@ func TestRunner_RecordsScreenFieldFromSnapshot(t *testing.T) {
 	}
 }
 
+func TestScreenFromSnapshot(t *testing.T) {
+	t.Run("string value returns screen", func(t *testing.T) {
+		snapshots := map[string]json.RawMessage{"screen": json.RawMessage(`"home"`)}
+		screen, err := screenFromSnapshot(snapshots)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if screen != "home" {
+			t.Errorf("screen = %q, want %q", screen, "home")
+		}
+	})
+	t.Run("missing key returns empty with no error", func(t *testing.T) {
+		screen, err := screenFromSnapshot(map[string]json.RawMessage{})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if screen != "" {
+			t.Errorf("screen = %q, want empty", screen)
+		}
+	})
+	t.Run("non-string value returns error", func(t *testing.T) {
+		snapshots := map[string]json.RawMessage{"screen": json.RawMessage(`{"nested":1}`)}
+		screen, err := screenFromSnapshot(snapshots)
+		if err == nil {
+			t.Fatalf("expected error for non-string screen, got nil")
+		}
+		if screen != "" {
+			t.Errorf("screen = %q, want empty on error", screen)
+		}
+	})
+}
+
 func TestApplyAction_InputTextSurfacesFocusTapError(t *testing.T) {
 	t.Run("selector focus tap fails", func(t *testing.T) {
 		driverMock := mockdriver.New()