diff --git a/.gitignore b/.gitignore
index 180a2a7..d720fdd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ dist/
 build/
 .venv/
 decode-errors.log
+auth-test.log
diff --git a/simtrace2_pysniff/protocol.py b/simtrace2_pysniff/protocol.py
index 091fa1d..d3dc5d5 100644
--- a/simtrace2_pysniff/protocol.py
+++ b/simtrace2_pysniff/protocol.py
@@ -85,6 +85,12 @@ def _parse_change(payload):
     consumed = 4
     return consumed, flags, b''
 
+
+def _parse_fidi(payload):
+    if len(payload) < 1:
+        return None
+    return 1, 0, payload[:1]
+
 _SNIFF_DATA_FMT = '<IH'
 _SNIFF_DATA_HDR_SIZE = struct.calcsize(_SNIFF_DATA_FMT)  # 6 bytes
 
@@ -102,7 +108,7 @@ def _parse_data(payload):
 
 _PAYLOAD_PARSERS = {
     SIMTRACE_MSGT_SNIFF_CHANGE: _parse_change,
-    SIMTRACE_MSGT_SNIFF_FIDI:   _parse_change,
+    SIMTRACE_MSGT_SNIFF_FIDI:   _parse_fidi,
     SIMTRACE_MSGT_SNIFF_ATR:    _parse_data,
     SIMTRACE_MSGT_SNIFF_PPS:    _parse_data,
     SIMTRACE_MSGT_SNIFF_TPDU:   _parse_data,
diff --git a/simtrace2_pysniff/server/capture.py b/simtrace2_pysniff/server/capture.py
index bf02048..898085e 100644
--- a/simtrace2_pysniff/server/capture.py
+++ b/simtrace2_pysniff/server/capture.py
@@ -24,7 +24,7 @@ class GsmtapListener:
             if sub_type is None:
                 continue
             msg_type = 'atr' if sub_type == GSMTAP_SIM_ATR else 'tpdu'
-            yield msg_type, data
+            yield msg_type, data, 0
 
 
 class DirectSniffer:
@@ -49,7 +49,7 @@ class DirectSniffer:
         for msg in self._session.iter_messages():
             if not self._running:
                 break
-            yield msg.type, msg.data
+            yield msg.type, msg.data, msg.flags
 
 
 class CaptureManager:
@@ -103,9 +103,9 @@ class CaptureManager:
         return sid
 
     def _capture_loop(self):
-        for msg_type, data in self._backend.iter_messages():
+        for msg_type, data, flags in self._backend.iter_messages():
             if self._session_id is None:
                 break
             elapsed = round(time.monotonic() - self._start_time, 3)
-            mid = self._db.insert_message(self._session_id, elapsed, msg_type, data)
+            mid = self._db.insert_message(self._session_id, elapsed, msg_type, data, flags)
             self._latest_msg_id = mid
diff --git a/simtrace2_pysniff/server/database.py b/simtrace2_pysniff/server/database.py
index 938b0aa..c3982f9 100644
--- a/simtrace2_pysniff/server/database.py
+++ b/simtrace2_pysniff/server/database.py
@@ -168,18 +168,19 @@ class Database:
 
     def _row_to_message(self, row):
         data_blob = row[4]
+        flags = row[5]
         msg = {
             'id': row[0],
             'session_id': row[1],
             'elapsed': row[2],
             'type': row[3],
             'data': data_blob.hex(),
-            'flags': row[5],
+            'flags': flags,
         }
-        if row[3] in ('tpdu', 'change', 'fidi', 'atr', 'pps') and data_blob:
+        if row[3] in ('tpdu', 'change', 'fidi', 'atr', 'pps'):
             try:
                 from .decode import decode_sniff_msg
-                msg['decoded'] = decode_sniff_msg(data_blob, row[3])
+                msg['decoded'] = decode_sniff_msg(data_blob, row[3], flags)
             except Exception as e:
                 import sys
                 print(f'Decode error for msg {row[0]} ({row[3]}, {len(data_blob)} bytes): {e}',
diff --git a/simtrace2_pysniff/server/decode.py b/simtrace2_pysniff/server/decode.py
index 32d0683..4eb0d41 100644
--- a/simtrace2_pysniff/server/decode.py
+++ b/simtrace2_pysniff/server/decode.py
@@ -590,12 +590,8 @@ CHANGE_FLAGS = {
 }
 
 
-def decode_change(raw_data):
-    """Decode a SIMtrace2 sniff_change payload (4-byte flags)."""
-    if len(raw_data) < 4:
-        return None
-    import struct
-    flags = struct.unpack('<I', raw_data[:4])[0]
+def decode_change(flags):
+    """Decode SIMtrace2 sniff_change flags into a list of human-readable names."""
     bits = []
     for mask, name in sorted(CHANGE_FLAGS.items()):
         if flags & mask:
@@ -628,7 +624,7 @@ def decode_fidi(raw_data):
     }
 
 
-def decode_sniff_msg(raw_data, msg_type):
+def decode_sniff_msg(raw_data, msg_type, flags=0):
     """Decode a raw sniff message of the given type.
 
     Returns a structured dict with at least a 'type' key, or None if
@@ -636,8 +632,8 @@ def decode_sniff_msg(raw_data, msg_type):
     """
     if msg_type == 'tpdu' and raw_data:
         return decode_message(raw_data)
-    if msg_type == 'change' and raw_data:
-        return decode_change(raw_data)
+    if msg_type == 'change':
+        return decode_change(flags)
     if msg_type == 'fidi' and raw_data:
         return decode_fidi(raw_data)
     if msg_type == 'atr':
diff --git a/tests/test_decode.py b/tests/test_decode.py
index 0e70a5d..18e509a 100644
--- a/tests/test_decode.py
+++ b/tests/test_decode.py
@@ -92,5 +92,32 @@ class TestCommandTypeTables(unittest.TestCase):
         self.assertEqual(ENVELOPE_TYPES[0xD6], 'EVENT DOWNLOAD')
 
 
+class TestChangeAndFidiDecoding(unittest.TestCase):
+    def test_change_reset_assert(self):
+        r = decode_sniff_msg(b'', 'change', flags=1 << 2)
+        self.assertEqual(r['type'], 'change')
+        self.assertEqual(r['flags'], ['Reset asserted'])
+
+    def test_change_card_insert(self):
+        r = decode_sniff_msg(b'', 'change', flags=1 << 0)
+        self.assertEqual(r['flags'], ['Card inserted'])
+
+    def test_change_multiple_flags(self):
+        r = decode_sniff_msg(b'', 'change', flags=(1 << 2) | (1 << 3))
+        self.assertEqual(r['flags'], ['Reset asserted', 'Reset de-asserted'])
+
+    def test_change_no_flags(self):
+        r = decode_sniff_msg(b'', 'change', flags=0)
+        self.assertEqual(r['flags'], ['no changes'])
+
+    def test_fidi(self):
+        r = decode_sniff_msg(b'\x97', 'fidi')
+        self.assertEqual(r['type'], 'fidi')
+        self.assertEqual(r['fi'], 9)
+        self.assertEqual(r['di'], 7)
+        self.assertEqual(r['fi_val'], 512)
+        self.assertEqual(r['di_val'], 64)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/test_protocol.py b/tests/test_protocol.py
index ffdf177..bf1b558 100644
--- a/tests/test_protocol.py
+++ b/tests/test_protocol.py
@@ -83,13 +83,14 @@ class TestParseMessage(unittest.TestCase):
         self.assertEqual(msg.flags, CHANGE_FLAG_TIMEOUT_WT)
 
     def test_fidi_message(self):
-        payload = struct.pack('<I', 0x97)  # Fi=9, Di=7
+        payload = b'\x97'  # Fi=9, Di=7
         buf = _build_hdr(SIMTRACE_MSGC_SNIFF, SIMTRACE_MSGT_SNIFF_FIDI,
                          payload=payload)
         msg, consumed = parse_message(buf)
         self.assertEqual(msg.type, 'fidi')
-        self.assertEqual(len(msg.data), 0)
-        self.assertEqual(msg.flags, 0x97)
+        self.assertEqual(len(msg.data), 1)
+        self.assertEqual(msg.data, b'\x97')
+        self.assertEqual(msg.flags, 0)
 
     def test_atr_message(self):
         atr = b'\x3b\x9e\x12\x34\x56\x78\x90'