diff --git a/tests/test_main.py b/tests/test_main.py
index 4f665df..4a68d53 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -60,3 +60,61 @@ def test_flag_detector_stream_no_pattern():
     stream.write("normal output flag{hello}")
     assert out.getvalue() == "normal output flag{hello}"
 
+def test_flag_detector_stream_persistence():
+    """
+    Verifies that FlagDetectorStream writes the detected flag to config.toml.
+    """
+    from io import StringIO
+    from ctf.main import FlagDetectorStream
+    from ctf.utils import load_config, write_config
+    from pathlib import Path
+    
+    config_file = Path("/home/venus/code/ctf/config.toml")
+    original_config = load_config(str(config_file))
+    
+    try:
+        out = StringIO()
+        stream = FlagDetectorStream(out, r"flag\{[a-z_]+\}")
+        stream.write("found flag{persisted_flag} in stdout")
+        
+        # Reload config and check last_flag
+        updated_config = load_config(str(config_file))
+        assert updated_config.get("Competition", {}).get("last_flag") == "flag{persisted_flag}"
+    finally:
+        write_config(original_config, str(config_file))
+
+def test_flag_cmd_cli():
+    """
+    Verifies the ctf flag command outputs last_flag with and without --plain.
+    """
+    from click.testing import CliRunner
+    from ctf.main import cli
+    from ctf.utils import load_config, write_config
+    from pathlib import Path
+    
+    config_file = Path("/home/venus/code/ctf/config.toml")
+    original_config = load_config(str(config_file))
+    
+    try:
+        # Pre-set last_flag in config
+        temp_config = load_config(str(config_file))
+        if "Competition" not in temp_config:
+            temp_config["Competition"] = {}
+        temp_config["Competition"]["last_flag"] = "flag{test_cli_flag}"
+        write_config(temp_config, str(config_file))
+        
+        runner = CliRunner()
+        
+        # Test standard flag command output
+        result_std = runner.invoke(cli, ["flag"])
+        assert result_std.exit_code == 0
+        assert "Last detected flag: flag{test_cli_flag}" in result_std.output
+        
+        # Test plain flag command output (no flavor text, no newline)
+        result_plain = runner.invoke(cli, ["flag", "--plain"])
+        assert result_plain.exit_code == 0
+        assert result_plain.output == "flag{test_cli_flag}"
+    finally:
+        write_config(original_config, str(config_file))
+
+