fix: use binary mode in screenshot subprocess calls to avoid encoding errors

phone_agent/adb/screenshot.py

@@ -41,24 +41,25 @@ def get_screenshot(device_id: str | None = None, timeout: int = 10) -> Screensho
     adb_prefix = _get_adb_prefix(device_id)
 
     try:
-        # Execute screenshot command
+        # Execute screenshot command (use binary mode to avoid encoding issues)
         result = subprocess.run(
             adb_prefix + ["shell", "screencap", "-p", "/sdcard/tmp.png"],
             capture_output=True,
-            text=True,
+            text=False,
             timeout=timeout,
         )
 
         # Check for screenshot failure (sensitive screen)
-        output = result.stdout + result.stderr
+        # Decode with error handling for binary output
+        output = (result.stdout + result.stderr).decode("utf-8", errors="replace")
         if "Status: -1" in output or "Failed" in output:
             return _create_fallback_screenshot(is_sensitive=True)
 
-        # Pull screenshot to local temp path
+        # Pull screenshot to local temp path (use binary mode for file transfer)
         subprocess.run(
             adb_prefix + ["pull", "/sdcard/tmp.png", temp_path],
             capture_output=True,
-            text=True,
+            text=False,
             timeout=5,
         )
 

tests/test_screenshot_encoding.py

@@ -0,0 +1,73 @@
+"""Tests for screenshot.py encoding handling.
+
+This test verifies that subprocess.run uses binary mode (text=False) to avoid
+UTF-8 encoding errors when handling screenshot operations (Issue #224).
+"""
+
+import os
+import re
+import unittest
+
+
+class TestScreenshotEncodingFix(unittest.TestCase):
+    """Test that screenshot.py uses binary mode for subprocess calls."""
+
+    def test_screenshot_uses_binary_mode_for_screencap(self):
+        """Verify screencap command uses text=False."""
+        screenshot_py_path = os.path.join(
+            os.path.dirname(os.path.dirname(__file__)),
+            'phone_agent', 'adb', 'screenshot.py'
+        )
+
+        with open(screenshot_py_path, 'r', encoding='utf-8') as f:
+            content = f.read()
+
+        # Find the screencap subprocess.run call
+        screencap_pattern = r'subprocess\.run\([^)]*screencap[^)]*\)'
+        match = re.search(screencap_pattern, content, re.DOTALL)
+        self.assertIsNotNone(match, "Could not find subprocess.run with screencap")
+
+        subprocess_call = match.group(0)
+
+        # Verify text=False is used (binary mode)
+        self.assertIn('text=False', subprocess_call,
+                      "screencap should use text=False for binary mode")
+
+    def test_screenshot_uses_binary_mode_for_pull(self):
+        """Verify pull command uses text=False."""
+        screenshot_py_path = os.path.join(
+            os.path.dirname(os.path.dirname(__file__)),
+            'phone_agent', 'adb', 'screenshot.py'
+        )
+
+        with open(screenshot_py_path, 'r', encoding='utf-8') as f:
+            content = f.read()
+
+        # Find the pull subprocess.run call
+        pull_pattern = r'subprocess\.run\([^)]*"pull"[^)]*\)'
+        match = re.search(pull_pattern, content, re.DOTALL)
+        self.assertIsNotNone(match, "Could not find subprocess.run with pull")
+
+        subprocess_call = match.group(0)
+
+        # Verify text=False is used (binary mode)
+        self.assertIn('text=False', subprocess_call,
+                      "pull should use text=False for binary mode")
+
+    def test_screenshot_decodes_output_with_error_handling(self):
+        """Verify output is decoded with errors='replace'."""
+        screenshot_py_path = os.path.join(
+            os.path.dirname(os.path.dirname(__file__)),
+            'phone_agent', 'adb', 'screenshot.py'
+        )
+
+        with open(screenshot_py_path, 'r', encoding='utf-8') as f:
+            content = f.read()
+
+        # Check for proper decoding with error handling
+        self.assertIn('decode("utf-8", errors="replace")', content,
+                      "Output should be decoded with errors='replace' to handle surrogates")
+
+
+if __name__ == '__main__':
+    unittest.main()