diff --git a/config.ini.example b/config.ini.example
index e14dab9..8c1bc79 100644
--- a/config.ini.example
+++ b/config.ini.example
@@ -851,6 +851,15 @@ mesh_connections_retention_days = 7
 # Enable or disable the path command
 enabled = true
 
+# Require minimum path byte length before responding to this command
+# 0 = allow all (default)
+# 1 = allow all (compatibility alias for 0)
+# 2 = only respond when path has 2 bytes or more (e.g. 0101...)
+# 3 = only respond when path is exactly 3 bytes (e.g. 010101)
+require_path_bytes_greater_or_equal_to = 0
+# Optional response when rejected by path-byte requirement; leave empty for silent reject
+require_path_bytes_failure_response =
+
 # Enable "p" shortcut for path command (similar to "t" for test command)
 # true: Respond to just "p" or "p <path_data>" as a shortcut for "path"  (default)
 # false: Only respond to "path", "decode", or "route" keywords
@@ -1095,6 +1104,14 @@ enabled = false
 response_format = @[{sender}] found {path_count} unique path(s):\n{paths}
 # condense_paths: false = one full path per line; true = flat condensed tree (default); nested = indented ├/└ under ┐ sub-blocks (uses ASCII spaces, not U+2502, to save bytes vs old │).
 condense_paths = true
+# Require minimum path byte length for triggering and collected packets
+# 0 = allow all (default)
+# 1 = allow all (compatibility alias for 0)
+# 2 = only include paths with 2 bytes or more (e.g. 0101...)
+# 3 = only include paths with exactly 3 bytes (e.g. 010101)
+require_path_bytes_greater_or_equal_to = 0
+# Optional response when rejected by path-byte requirement; leave empty for silent reject
+require_path_bytes_failure_response =
 
 [Greeter_Command]
 # Enable greeter to greet users on first channel message (true/false)
@@ -1324,6 +1341,14 @@ enabled = true
 
 [Test_Command]
 enabled = true
+# Require minimum path byte length before responding to test/t
+# 0 = allow all (default)
+# 1 = allow all (compatibility alias for 0)
+# 2 = only respond when path has 2 bytes or more (e.g. 0101...)
+# 3 = only respond when path is exactly 3 bytes (e.g. 010101)
+require_path_bytes_greater_or_equal_to = 0
+# Optional response when rejected by path-byte requirement; leave empty for silent reject
+require_path_bytes_failure_response =
 # channels =
 
 [Trace_Command]
diff --git a/modules/commands/base_command.py b/modules/commands/base_command.py
index a66aca7..1b49b75 100644
--- a/modules/commands/base_command.py
+++ b/modules/commands/base_command.py
@@ -919,6 +919,106 @@ class BaseCommand(ABC):
         """Check if this command can execute right now (permissions, cooldown, etc.)"""
         return self.can_execute(message)
 
+    def _get_required_path_bytes_setting(self, section: str) -> int:
+        """Return normalized path-byte requirement for a command section.
+
+        Supported values:
+        - 0/1: allow all
+        - 2: require >= 2 bytes
+        - 3: require exactly 3 bytes
+        """
+        required = self.get_config_value(
+            section,
+            'require_path_bytes_greater_or_equal_to',
+            fallback=0,
+            value_type='int',
+        )
+        if required in (0, 1, 2, 3):
+            return required
+        self.logger.warning(
+            f"Invalid {section}.require_path_bytes_greater_or_equal_to={required}; defaulting to 0"
+        )
+        return 0
+
+    def _path_bytes_match_requirement(self, path_byte_length: int, required_path_bytes: int) -> bool:
+        """Check whether path byte length satisfies configured requirement."""
+        if required_path_bytes in (0, 1):
+            return True
+        if required_path_bytes == 2:
+            return path_byte_length >= 2
+        if required_path_bytes == 3:
+            return path_byte_length == 3
+        return True
+
+    def _get_message_path_byte_length(self, message: MeshMessage) -> int:
+        """Best-effort extraction of message path byte length from routing/path data."""
+        routing_info = getattr(message, 'routing_info', None)
+        if routing_info:
+            raw_path_byte_length = routing_info.get('path_byte_length')
+            if isinstance(raw_path_byte_length, int) and raw_path_byte_length >= 0:
+                return raw_path_byte_length
+
+            bytes_per_hop = routing_info.get('bytes_per_hop')
+            path_length = routing_info.get('path_length')
+            if (
+                isinstance(bytes_per_hop, int)
+                and bytes_per_hop >= 0
+                and isinstance(path_length, int)
+                and path_length >= 0
+            ):
+                return bytes_per_hop * path_length
+
+            path_nodes = routing_info.get('path_nodes') or []
+            if path_nodes:
+                total = 0
+                for node in path_nodes:
+                    node_str = str(node).strip()
+                    if not node_str:
+                        continue
+                    total += len(node_str) // 2
+                return total
+
+        path_string = (getattr(message, 'path', None) or '').strip()
+        if not path_string:
+            return 0
+        if " via ROUTE_TYPE_" in path_string:
+            path_string = path_string.split(" via ROUTE_TYPE_")[0]
+        if "Direct" in path_string or "0 hops" in path_string:
+            return 0
+        path_string = re.sub(r'\s*\([^)]*hops?[^)]*\)', '', path_string, flags=re.IGNORECASE).strip()
+        if not path_string:
+            return 0
+        if ',' in path_string:
+            tokens = [t.strip() for t in path_string.split(',') if t.strip()]
+            if tokens:
+                return sum(len(t) // 2 for t in tokens)
+        return len(path_string) // 2
+
+    def _get_required_path_bytes_failure_response(self, section: str) -> Optional[str]:
+        """Get optional response text used when path-byte requirement fails."""
+        failure_response = self.get_config_value(
+            section,
+            'require_path_bytes_failure_response',
+            fallback='',
+            value_type='str',
+        )
+        if not failure_response:
+            return None
+        cleaned = self._strip_quotes_from_config(failure_response).strip()
+        return cleaned or None
+
+    async def enforce_path_byte_requirement(self, message: MeshMessage, section: str) -> bool:
+        """Apply path-byte requirement; optionally send configured failure response."""
+        required = self._get_required_path_bytes_setting(section)
+        path_byte_length = self._get_message_path_byte_length(message)
+        if self._path_bytes_match_requirement(path_byte_length, required):
+            return True
+
+        failure_response = self._get_required_path_bytes_failure_response(section)
+        if failure_response:
+            await self.send_response(message, failure_response)
+        return False
+
     def get_path_display_string(self, message: MeshMessage) -> str:
         """Get path string for display (test/ack placeholders). Prefers message.routing_info for multi-byte and direct."""
         routing_info = getattr(message, 'routing_info', None)
diff --git a/modules/commands/multitest_command.py b/modules/commands/multitest_command.py
index 17dcb5c..3bb4835 100644
--- a/modules/commands/multitest_command.py
+++ b/modules/commands/multitest_command.py
@@ -542,6 +542,7 @@ class MultitestSession:
     listening_duration: float
     collected_paths: set[str]
     initial_path: Optional[str] = None
+    required_path_bytes_mode: int = 0
 
 
 class MultitestCommand(BaseCommand):
@@ -741,6 +742,34 @@ class MultitestCommand(BaseCommand):
             return ','.join(n.lower() for n in node_ids)
         return None
 
+    def _get_routing_info_path_byte_length(self, routing_info: dict) -> int:
+        """Best-effort extraction of path byte length from routing_info."""
+        if not routing_info:
+            return 0
+
+        raw_path_byte_length = routing_info.get('path_byte_length')
+        if isinstance(raw_path_byte_length, int) and raw_path_byte_length >= 0:
+            return raw_path_byte_length
+
+        bytes_per_hop = routing_info.get('bytes_per_hop')
+        path_length = routing_info.get('path_length')
+        if (
+            isinstance(bytes_per_hop, int)
+            and bytes_per_hop >= 0
+            and isinstance(path_length, int)
+            and path_length >= 0
+        ):
+            return bytes_per_hop * path_length
+
+        path_nodes = routing_info.get('path_nodes') or []
+        total = 0
+        for node in path_nodes:
+            node_str = str(node).strip()
+            if not node_str:
+                continue
+            total += len(node_str) // 2
+        return total
+
     def get_rf_data_for_message(self, message: MeshMessage) -> Optional[dict]:
         """Get RF data for a message by looking it up in recent RF data"""
         try:
@@ -831,6 +860,11 @@ class MultitestCommand(BaseCommand):
             # CRITICAL: Only collect paths if this message has the same hash as the target
             # This ensures we only track variations of the same original message
             if message_hash == session.target_packet_hash:
+                routing_info = rf_data.get('routing_info', {})
+                path_byte_length = self._get_routing_info_path_byte_length(routing_info)
+                if not self._path_bytes_match_requirement(path_byte_length, session.required_path_bytes_mode):
+                    continue
+
                 # Try to extract path from RF data first (more reliable)
                 path = self.extract_path_from_rf_data(rf_data)
 
@@ -843,7 +877,6 @@ class MultitestCommand(BaseCommand):
                     self.logger.info(f"✓ Collected path for user {user_id}: {path} (hash: {message_hash[:8]}...)")
                 else:
                     # Log when we have a matching hash but can't extract path
-                    routing_info = rf_data.get('routing_info', {})
                     path_length = routing_info.get('path_length', 0)
                     if path_length == 0:
                         self.logger.debug(f"Matched hash {message_hash[:8]}... but path is direct (0 hops) for user {user_id}")
@@ -880,6 +913,11 @@ class MultitestCommand(BaseCommand):
 
                     # CRITICAL: Only process if hash matches exactly and is not None/empty
                     if packet_hash and packet_hash == session.target_packet_hash:
+                        routing_info = rf_data.get('routing_info', {})
+                        path_byte_length = self._get_routing_info_path_byte_length(routing_info)
+                        if not self._path_bytes_match_requirement(path_byte_length, session.required_path_bytes_mode):
+                            continue
+
                         matching_count += 1
                         # Extract path from this RF data
                         path = self.extract_path_from_rf_data(rf_data)
@@ -902,6 +940,9 @@ class MultitestCommand(BaseCommand):
     async def execute(self, message: MeshMessage) -> bool:
         """Execute the multitest command"""
         user_id = message.sender_id or "unknown"
+        required_path_bytes_mode = self._get_required_path_bytes_setting('Multitest_Command')
+        if not await self.enforce_path_byte_requirement(message, 'Multitest_Command'):
+            return True
 
         # Use lock to prevent concurrent execution from interfering
         async with self._get_execution_lock():
@@ -985,7 +1026,8 @@ class MultitestCommand(BaseCommand):
                 listening_start_time=time.time(),
                 listening_duration=listening_duration,
                 collected_paths=set(),
-                initial_path=initial_path
+                initial_path=initial_path,
+                required_path_bytes_mode=required_path_bytes_mode,
             )
 
             # Add initial path if available
diff --git a/modules/commands/path_command.py b/modules/commands/path_command.py
index dc43942..f9a9d17 100644
--- a/modules/commands/path_command.py
+++ b/modules/commands/path_command.py
@@ -197,6 +197,9 @@ class PathCommand(BaseCommand):
         """Execute path decode command"""
         self.logger.info(f"Path command executed with content: {message.content}")
 
+        if not await self.enforce_path_byte_requirement(message, 'Path_Command'):
+            return True
+
         # Store the current message for use in _extract_path_from_recent_messages
         self._current_message = message
 
diff --git a/modules/commands/test_command.py b/modules/commands/test_command.py
index 57b4874..fe833a1 100644
--- a/modules/commands/test_command.py
+++ b/modules/commands/test_command.py
@@ -710,6 +710,9 @@ class TestCommand(BaseCommand):
         Returns:
             bool: True if execution was successful.
         """
+        if not await self.enforce_path_byte_requirement(message, 'Test_Command'):
+            return True
+
         # Store the current message for use in location lookups
         self._current_message = message
         return await self.handle_keyword_match(message)
diff --git a/modules/service_plugins/packet_capture_service.py b/modules/service_plugins/packet_capture_service.py
index 3a38e58..60a302a 100644
--- a/modules/service_plugins/packet_capture_service.py
+++ b/modules/service_plugins/packet_capture_service.py
@@ -704,88 +704,15 @@ class PacketCaptureService(BaseServicePlugin):
         snr = str(payload.get('snr', 'Unknown'))
         rssi = str(payload.get('rssi', 'Unknown'))
 
-        # Get packet hash - check multiple sources in order of preference, then calculate if needed
-        # This matches the original script's approach: use hash from routing_info if available, otherwise calculate
-        packet_hash = '0000000000000000'
+        # Get packet hash from decoded packet_info — same clean bytes as the upload's "raw" field,
+        # so this is always the correct hash (matches what other observers compute).
+        packet_hash = packet_info.get('packet_hash', '0000000000000000')
 
-        # 1. Check if payload has packet_hash directly (from bot's processing)
-        if isinstance(payload, dict):
-            if 'packet_hash' in payload:
-                packet_hash = payload['packet_hash']
-            # 2. Check if payload has routing_info with packet_hash
-            elif 'routing_info' in payload:
-                routing_info = payload.get('routing_info', {})
-                if isinstance(routing_info, dict) and 'packet_hash' in routing_info:
-                    packet_hash = routing_info['packet_hash']
-
-        # 3. Check metadata if available
-        if packet_hash == '0000000000000000' and metadata and isinstance(metadata, dict):
-            if 'packet_hash' in metadata:
-                packet_hash = metadata['packet_hash']
-            elif 'routing_info' in metadata:
-                routing_info = metadata.get('routing_info', {})
-                if isinstance(routing_info, dict) and 'packet_hash' in routing_info:
-                    packet_hash = routing_info['packet_hash']
-
-        # 4. Try to get from bot's recent_rf_data cache (if message_handler has processed it)
-        # Note: The bot stores full raw_hex (with framing bytes) for packet_prefix, but we use stripped raw_hex
-        # So we need to use the full raw_hex from payload for prefix matching
-        # Optimized: Use indexed rf_data_by_pubkey for O(1) lookup instead of linear search
-        if packet_hash == '0000000000000000' and hasattr(self.bot, 'message_handler'):
-            try:
-                message_handler = self.bot.message_handler
-
-                # Get full raw_hex from payload for prefix matching (bot uses full raw_hex for packet_prefix)
-                full_raw_hex = payload.get('raw_hex', '')
-                if full_raw_hex:
-                    packet_prefix = full_raw_hex.replace('0x', '')[:32] if len(full_raw_hex.replace('0x', '')) >= 32 else full_raw_hex.replace('0x', '')
-                else:
-                    # Fallback: use stripped raw_hex (might not match, but worth trying)
-                    clean_raw_hex_for_lookup = raw_hex.replace('0x', '')
-                    packet_prefix = clean_raw_hex_for_lookup[:32] if len(clean_raw_hex_for_lookup) >= 32 else clean_raw_hex_for_lookup
-
-                # Use indexed lookup (O(1)) instead of linear search (O(n))
-                if hasattr(message_handler, 'rf_data_by_pubkey') and packet_prefix:
-                    rf_data_list = message_handler.rf_data_by_pubkey.get(packet_prefix, [])
-                    # Check most recent entries first (last in list, since they're appended in order)
-                    for rf_data in reversed(rf_data_list):
-                        if 'packet_hash' in rf_data:
-                            packet_hash = rf_data['packet_hash']
-                            break
-                        elif 'routing_info' in rf_data:
-                            routing_info = rf_data.get('routing_info', {})
-                            if isinstance(routing_info, dict) and 'packet_hash' in routing_info:
-                                packet_hash = routing_info['packet_hash']
-                                break
-
-                # Fallback to linear search only if indexed lookup not available (backward compatibility)
-                if packet_hash == '0000000000000000' and hasattr(message_handler, 'recent_rf_data'):
-                    for rf_data in message_handler.recent_rf_data:
-                        # Match by packet_prefix (bot uses full raw_hex for this)
-                        if rf_data.get('packet_prefix') == packet_prefix:
-                            if 'packet_hash' in rf_data:
-                                packet_hash = rf_data['packet_hash']
-                                break
-                            elif 'routing_info' in rf_data:
-                                routing_info = rf_data.get('routing_info', {})
-                                if isinstance(routing_info, dict) and 'packet_hash' in routing_info:
-                                    packet_hash = routing_info['packet_hash']
-                                    break
-            except Exception as e:
-                if self.debug:
-                    self.logger.debug(f"Error checking recent_rf_data for hash: {e}")
-
-        # 5. Fall back to hash from decoded packet_info (should be calculated correctly)
-        if packet_hash == '0000000000000000':
-            packet_hash = packet_info.get('packet_hash', '0000000000000000')
-
-        # 6. If still no hash, calculate it from raw_hex (matches original script's format_packet_data)
+        # Only fall back to direct calculation if decode_packet didn't produce a hash
         if packet_hash == '0000000000000000':
             try:
-                # Use payload_type_value from packet_info if available, otherwise None (will be extracted from header)
                 payload_type_value = packet_info.get('payload_type_value')
                 if payload_type_value is not None:
-                    # Ensure it's an integer (handle enum.value if passed)
                     if hasattr(payload_type_value, 'value'):
                         payload_type_value = payload_type_value.value
                     payload_type_value = int(payload_type_value) & 0x0F
diff --git a/modules/utils.py b/modules/utils.py
index b6e53c4..d0dcb52 100644
--- a/modules/utils.py
+++ b/modules/utils.py
@@ -529,9 +529,8 @@ def calculate_packet_hash(raw_hex: str, payload_type: Optional[int] = None) -> s
 
         if payload_type == 9:  # PAYLOAD_TYPE_TRACE
             # C++ does: sha.update(&path_len, sizeof(path_len))
-            # path_len is uint16_t, so sizeof(path_len) = 2 bytes
-            # Convert path_len to 2-byte little-endian uint16_t
-            hash_obj.update(path_byte_length.to_bytes(2, byteorder='little'))
+            # path_len is the raw wire byte (uint16_t in firmware), not the decoded byte count
+            hash_obj.update(path_len_byte.to_bytes(2, byteorder='little'))
 
         hash_obj.update(payload_data)
 
diff --git a/tests/unit/test_command_path_byte_gating.py b/tests/unit/test_command_path_byte_gating.py
new file mode 100644
index 0000000..ff3e0ec
--- /dev/null
+++ b/tests/unit/test_command_path_byte_gating.py
@@ -0,0 +1,139 @@
+#!/usr/bin/env python3
+"""Unit tests for path-byte gating across test/multitest/path commands."""
+
+import configparser
+from unittest.mock import AsyncMock, MagicMock, Mock
+
+import pytest
+
+from modules.commands.multitest_command import MultitestCommand, MultitestSession
+from modules.commands.path_command import PathCommand
+from modules.commands.test_command import TestCommand as MeshTestCommand
+from tests.conftest import mock_message
+
+
+def _base_bot() -> MagicMock:
+    bot = MagicMock()
+    bot.logger = Mock()
+    bot.config = configparser.ConfigParser()
+    bot.config.add_section("Bot")
+    bot.config.set("Bot", "bot_name", "TestBot")
+    bot.config.add_section("Channels")
+    bot.config.set("Channels", "monitor_channels", "general")
+    bot.config.set("Channels", "respond_to_dms", "true")
+    bot.config.add_section("Keywords")
+    bot.config.set("Keywords", "test", "ack")
+    bot.command_manager = MagicMock()
+    bot.command_manager.monitor_channels = ["general"]
+    bot.command_manager.send_response = AsyncMock(return_value=True)
+    bot.translator = MagicMock()
+    bot.translator.translate = Mock(side_effect=lambda key, **kwargs: key)
+    bot.prefix_hex_chars = 2
+    return bot
+
+
+@pytest.mark.asyncio
+async def test_test_command_rejects_silently_when_path_bytes_too_short():
+    bot = _base_bot()
+    bot.config.add_section("Test_Command")
+    bot.config.set("Test_Command", "enabled", "true")
+    bot.config.set("Test_Command", "require_path_bytes_greater_or_equal_to", "2")
+    bot.config.add_section("Path_Command")
+    bot.config.set("Path_Command", "recency_weight", "0.2")
+
+    cmd = MeshTestCommand(bot)
+    cmd.handle_keyword_match = AsyncMock(return_value=True)
+    message = mock_message(content="test", channel="general", routing_info={"path_byte_length": 1})
+
+    result = await cmd.execute(message)
+
+    assert result is True
+    cmd.handle_keyword_match.assert_not_called()
+    bot.command_manager.send_response.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_test_command_sends_failure_response_when_configured():
+    bot = _base_bot()
+    bot.config.add_section("Test_Command")
+    bot.config.set("Test_Command", "enabled", "true")
+    bot.config.set("Test_Command", "require_path_bytes_greater_or_equal_to", "3")
+    bot.config.set("Test_Command", "require_path_bytes_failure_response", "Need 3-byte path")
+    bot.config.add_section("Path_Command")
+    bot.config.set("Path_Command", "recency_weight", "0.2")
+
+    cmd = MeshTestCommand(bot)
+    cmd.handle_keyword_match = AsyncMock(return_value=True)
+    message = mock_message(content="test", channel="general", routing_info={"path_byte_length": 2})
+
+    result = await cmd.execute(message)
+
+    assert result is True
+    cmd.handle_keyword_match.assert_not_called()
+    bot.command_manager.send_response.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_path_command_mode_one_behaves_like_zero():
+    bot = _base_bot()
+    bot.config.add_section("Path_Command")
+    bot.config.set("Path_Command", "enabled", "true")
+    bot.config.set("Path_Command", "require_path_bytes_greater_or_equal_to", "1")
+
+    cmd = PathCommand(bot)
+    cmd._send_path_response = AsyncMock(return_value=True)
+    cmd._extract_path_from_recent_messages = AsyncMock(return_value="decoded")
+    message = mock_message(content="path", channel="general", routing_info={"path_byte_length": 0})
+
+    result = await cmd.execute(message)
+
+    assert result is True
+    cmd._extract_path_from_recent_messages.assert_awaited_once()
+    cmd._send_path_response.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_multitest_execute_rejects_with_custom_failure_message():
+    bot = _base_bot()
+    bot.config.add_section("Multitest_Command")
+    bot.config.set("Multitest_Command", "enabled", "true")
+    bot.config.set("Multitest_Command", "require_path_bytes_greater_or_equal_to", "2")
+    bot.config.set("Multitest_Command", "require_path_bytes_failure_response", "Need >=2 path bytes")
+
+    cmd = MultitestCommand(bot)
+    message = mock_message(content="multitest", channel="general", routing_info={"path_byte_length": 1})
+
+    result = await cmd.execute(message)
+
+    assert result is True
+    bot.command_manager.send_response.assert_awaited_once()
+
+
+def test_multitest_listener_filters_matching_hash_by_required_path_bytes():
+    bot = _base_bot()
+    bot.config.add_section("Multitest_Command")
+    bot.config.set("Multitest_Command", "enabled", "true")
+    cmd = MultitestCommand(bot)
+    cmd.extract_path_from_rf_data = Mock(return_value="0101")
+    cmd.get_rf_data_for_message = Mock(
+        return_value={
+            "packet_hash": "abc123",
+            "routing_info": {"path_byte_length": 2, "path_nodes": ["0101"]},
+        }
+    )
+
+    session = MultitestSession(
+        user_id="alice",
+        target_packet_hash="abc123",
+        triggering_timestamp=0.0,
+        listening_start_time=0.0,
+        listening_duration=9999.0,
+        collected_paths=set(),
+        required_path_bytes_mode=3,
+    )
+    cmd._active_sessions["alice"] = session
+    message = mock_message(content="x", sender_id="alice")
+
+    cmd.on_message_received(message)
+
+    assert session.collected_paths == set()
diff --git a/tests/unit/test_packet_capture_trace_decode.py b/tests/unit/test_packet_capture_trace_decode.py
index 8db1a04..f94fc31 100644
--- a/tests/unit/test_packet_capture_trace_decode.py
+++ b/tests/unit/test_packet_capture_trace_decode.py
@@ -1,8 +1,40 @@
 """Packet capture TRACE decode: path must come from payload, not RF SNR bytes."""
 
+import hashlib
 import logging
 
 from modules.service_plugins.packet_capture_service import PacketCaptureService
+from modules.utils import calculate_packet_hash
+
+
+def test_calculate_packet_hash_trace_uses_wire_byte():
+    """TRACE hash must use the raw path_len wire byte, not the decoded byte count.
+
+    When size_code > 0 (multi-byte-per-hop paths), path_len_byte != path_byte_length.
+    The firmware hashes path_len_byte (the raw wire value), so we must too.
+    """
+    # header 0x26: route_type=DIRECT(2), payload_type=TRACE(9), version=VER_1(0)
+    # path_len_byte 0x42: size_code=1 → 2 bytes/hop, hop_count=2 → path_byte_length=4
+    # path: AABBCCDD (4 bytes), payload: 01020304
+    raw_hex = "2642AABBCCDD01020304"
+
+    # Correct: use path_len_byte=0x42 (66), matching firmware Packet::calculatePacketHash()
+    expected = hashlib.sha256(
+        bytes([0x09])
+        + (0x42).to_bytes(2, "little")
+        + bytes.fromhex("01020304")
+    ).hexdigest()[:16].upper()
+
+    result = calculate_packet_hash(raw_hex, 9)
+    assert result == expected, f"Expected {expected}, got {result}"
+
+    # Confirm this differs from the old buggy value (path_byte_length=4 instead of wire byte 0x42)
+    buggy = hashlib.sha256(
+        bytes([0x09])
+        + (4).to_bytes(2, "little")
+        + bytes.fromhex("01020304")
+    ).hexdigest()[:16].upper()
+    assert result != buggy, "Hash must not match old path_byte_length computation"
 
 
 def test_decode_packet_trace_uses_payload_route_hashes():