From 8f8c578ed394ab1287bb3e22f74bae4861703416 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:25 +1000
Subject: [PATCH 01/21] modules: mavlink: update for 32 bit system ID support

---
 modules/mavlink | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/modules/mavlink b/modules/mavlink
index 13f2f7351a9bd..5ad0e91056065 160000
--- a/modules/mavlink
+++ b/modules/mavlink
@@ -1 +1 @@
-Subproject commit 13f2f7351a9bdf5292a2c243eb9a2c19ff4b6472
+Subproject commit 5ad0e9105606572ae2a3302b07302f8029ff99e1

From 8ec3ae430287cb8cf9170a96e782ed8a4578a907 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:25 +1000
Subject: [PATCH 02/21] GCS_MAVLink: fix statustext chunking component check

the component was compared against last_src_system, so chunked
statustexts from different components on the same system were joined
together.
---
 libraries/GCS_MAVLink/GCS_Common.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/GCS_MAVLink/GCS_Common.cpp b/libraries/GCS_MAVLink/GCS_Common.cpp
index 67a7fe18f189a..316c7eae5db5b 100644
--- a/libraries/GCS_MAVLink/GCS_Common.cpp
+++ b/libraries/GCS_MAVLink/GCS_Common.cpp
@@ -3856,7 +3856,7 @@ void GCS_MAVLINK::handle_statustext(const mavlink_message_t &msg)
     const uint8_t max_prefix_len = 14;
     const uint8_t text_len = MAVLINK_MSG_STATUSTEXT_FIELD_TEXT_LEN+1+max_prefix_len;
     if (msg.sysid != statustext_chunking.last_src_system ||
-        msg.compid != statustext_chunking.last_src_system ||
+        msg.compid != statustext_chunking.last_src_component ||
         packet.id != statustext_chunking.last_id) {
         statustext_chunking.last_src_system = msg.sysid;
         statustext_chunking.last_src_component = msg.compid;

From 41bbd7d69efcef9e35e73b0af5cb79caf5ee7645 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:40 +1000
Subject: [PATCH 03/21] GCS_MAVLink: support 32 bit system IDs

Widen system ID handling throughout for MAVLink2.1 32 bit system IDs
(mavlink/rfcs#20):

 - MAV_SYSID, MAV_GCS_SYSID and MAV_GCS_SYSID_HI become AP_Int32 with
   parameter width conversion. Values must stay below 2^24 until the
   parameter transport moves away from float32
 - routing table entries, get_targets() and find_by_mavtype use the
   mavlink_msg_get_target_sysid/compid helpers so targets in the
   extended header are honoured
 - packet_overhead_chan() conservatively reserves the extended header
 - TSYN and MAVC log the full 32 bit source and target system IDs
---
 libraries/GCS_MAVLink/GCS.cpp                 | 17 ++++---
 libraries/GCS_MAVLink/GCS.h                   | 48 +++++++++++++------
 libraries/GCS_MAVLink/GCS_Common.cpp          | 24 ++++++----
 libraries/GCS_MAVLink/GCS_FTP.cpp             |  5 +-
 libraries/GCS_MAVLink/GCS_FTP.h               |  4 +-
 libraries/GCS_MAVLink/GCS_MAVLink.cpp         |  2 +-
 libraries/GCS_MAVLink/GCS_Signing.cpp         | 16 ++++++-
 libraries/GCS_MAVLink/MAVLink_routing.cpp     | 37 +++++++++-----
 libraries/GCS_MAVLink/MAVLink_routing.h       |  8 ++--
 libraries/GCS_MAVLink/MissionItemProtocol.cpp | 10 ++--
 libraries/GCS_MAVLink/MissionItemProtocol.h   |  2 +-
 11 files changed, 114 insertions(+), 59 deletions(-)

diff --git a/libraries/GCS_MAVLink/GCS.cpp b/libraries/GCS_MAVLink/GCS.cpp
index cdaa7fda23db6..87e98071a8eb3 100644
--- a/libraries/GCS_MAVLink/GCS.cpp
+++ b/libraries/GCS_MAVLink/GCS.cpp
@@ -38,14 +38,14 @@ const AP_Param::GroupInfo GCS::var_info[] {
     // @Param: _SYSID
     // @DisplayName: MAVLink system ID of this vehicle
     // @Description: Allows setting an individual MAVLink system id for this vehicle to distinguish it from others on the same network.
-    // @Range: 1 255
+    // @Range: 1 16777215
     // @User: Advanced
     AP_GROUPINFO("_SYSID",    1,     GCS,  sysid,  MAV_SYSID_DEFAULT),
 
     // @Param: _GCS_SYSID
     // @DisplayName: My ground station number
     // @Description: This sets what MAVLink source system IDs are accepted for GCS failsafe handling, RC overrides and manual control. When MAV_GCS_SYSID_HI is less than MAV_GCS_SYSID then only this value is considered to be a GCS. When MAV_GCS_SYSID_HI is greater than or equal to MAV_GCS_SYSID then the range of values between MAV_GCS_SYSID and MAV_GCS_SYSID_HI (inclusive) are all treated as valid GCS MAVLink system IDs
-    // @Range: 1 255
+    // @Range: 1 16777215
     // @Increment: 1
     // @User: Advanced
     AP_GROUPINFO("_GCS_SYSID",    2,      GCS, mav_gcs_sysid, 255),
@@ -53,7 +53,7 @@ const AP_Param::GroupInfo GCS::var_info[] {
     // @Param: _GCS_SYSID_HI
     // @DisplayName: ground station system ID, maximum
     // @Description: Upper limit of MAVLink source system IDs considered to be from the GCS. When this is less than MAV_GCS_SYSID then only MAV_GCS_SYSID is used as GCS ID. When this is greater than or equal to MAV_GCS_SYSID then the range of values from MAV_GCS_SYSID to MAV_GCS_SYSID_HI (inclusive) is treated as a GCS ID.
-    // @Range: 0 255
+    // @Range: 0 16777215
     // @Increment: 1
     // @User: Advanced
     AP_GROUPINFO("_GCS_SYSID_HI",    5,   GCS, mav_gcs_sysid_high, 0),
@@ -261,6 +261,11 @@ MissionItemProtocol *GCS::missionitemprotocols[3];
 
 void GCS::init()
 {
+    // sysid parameters widened for 32 bit system IDs
+    sysid.convert_parameter_width(AP_PARAM_INT16);
+    mav_gcs_sysid.convert_parameter_width(AP_PARAM_INT16);
+    mav_gcs_sysid_high.convert_parameter_width(AP_PARAM_INT16);
+
     mavlink_system.sysid = sysid_this_mav();
 }
 
@@ -724,12 +729,12 @@ MAV_RESULT GCS::lua_command_int_packet(const mavlink_command_int_t &packet)
 /*
   return true if a MAVLink system ID is a GCS for this vehicle
 */
-bool GCS::sysid_is_gcs(uint8_t _sysid) const
+bool GCS::sysid_is_gcs(uint32_t _sysid) const
 {
     if (mav_gcs_sysid_high <= mav_gcs_sysid) {
-        return mav_gcs_sysid == _sysid;
+        return uint32_t(mav_gcs_sysid.get()) == _sysid;
     }
-    return _sysid >= mav_gcs_sysid && _sysid <= mav_gcs_sysid_high;
+    return _sysid >= uint32_t(mav_gcs_sysid.get()) && _sysid <= uint32_t(mav_gcs_sysid_high.get());
 }
 
 #endif  // HAL_GCS_ENABLED
diff --git a/libraries/GCS_MAVLink/GCS.h b/libraries/GCS_MAVLink/GCS.h
index 9d845e40dcef6..c350431622ca8 100644
--- a/libraries/GCS_MAVLink/GCS.h
+++ b/libraries/GCS_MAVLink/GCS.h
@@ -149,13 +149,13 @@ class GCS_MAVLINK_InProgress
     Type task;
     MAV_CMD mav_cmd;
 
-    static class GCS_MAVLINK_InProgress *get_task(MAV_CMD cmd, Type t, uint8_t sysid, uint8_t compid, mavlink_channel_t chan);
+    static class GCS_MAVLINK_InProgress *get_task(MAV_CMD cmd, Type t, uint32_t sysid, uint8_t compid, mavlink_channel_t chan);
 
     static void check_tasks();
 
 private:
 
-    uint8_t requesting_sysid;
+    uint32_t requesting_sysid;
     uint8_t requesting_compid;
     mavlink_channel_t chan;
 
@@ -260,6 +260,26 @@ class GCS_MAVLINK
                                         entry->max_msg_len,
                                         entry->crc_extra);
     }
+    // variant for raw payload structs with a target sysid over 255; the
+    // caller must have written the payload target_system byte as
+    // (target_sysid > 255 ? 0 : target_sysid)
+    void send_message_target(uint32_t msgid, const char *pkt, uint32_t target_sysid, uint8_t target_compid) {
+        const mavlink_msg_entry_t *entry = mavlink_get_msg_entry(msgid);
+        if (entry == nullptr) {
+            return;
+        }
+        if (!check_payload_size(entry->max_msg_len)) {
+            return;
+        }
+        _mav_finalize_message_chan_send_target(chan,
+                                               entry->msgid,
+                                               pkt,
+                                               entry->min_msg_len,
+                                               entry->max_msg_len,
+                                               entry->crc_extra,
+                                               target_sysid,
+                                               target_compid);
+    }
 
     // accessor for uart
     AP_HAL::UARTDriver *get_uart() { return _port; }
@@ -391,7 +411,7 @@ class GCS_MAVLINK
     void send_accelcal_vehicle_position(uint32_t position);
     void send_scaled_imu(uint8_t instance, void (*send_fn)(mavlink_channel_t chan, uint32_t time_ms, int16_t xacc, int16_t yacc, int16_t zacc, int16_t xgyro, int16_t ygyro, int16_t zgyro, int16_t xmag, int16_t ymag, int16_t zmag, int16_t temperature));
     void send_sys_status();
-    void send_set_position_target_global_int(uint8_t target_system, uint8_t target_component, const Location& loc);
+    void send_set_position_target_global_int(uint32_t target_system, uint8_t target_component, const Location& loc);
     void send_rpm() const;
     void send_generator_status() const;
 #if AP_WINCH_ENABLED
@@ -469,16 +489,16 @@ class GCS_MAVLINK
       search for a component in the routing table with given mav_type and retrieve it's sysid, compid and channel
       returns if a matching component is found
      */
-    static bool find_by_mavtype(uint8_t mav_type, uint8_t &sysid, uint8_t &compid, mavlink_channel_t &channel) { return routing.find_by_mavtype(mav_type, sysid, compid, channel); }
+    static bool find_by_mavtype(uint8_t mav_type, uint32_t &sysid, uint8_t &compid, mavlink_channel_t &channel) { return routing.find_by_mavtype(mav_type, sysid, compid, channel); }
 
     /*
       search for the first vehicle or component in the routing table with given mav_type and component id and retrieve its sysid and channel
       returns true if a match is found
      */
-    static bool find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint8_t &sysid, mavlink_channel_t &channel) { return routing.find_by_mavtype_and_compid(mav_type, compid, sysid, channel); }
+    static bool find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint32_t &sysid, mavlink_channel_t &channel) { return routing.find_by_mavtype_and_compid(mav_type, compid, sysid, channel); }
     // same as above, but returns a pointer to the GCS_MAVLINK object
     // corresponding to the channel
-    static GCS_MAVLINK *find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint8_t &sysid);
+    static GCS_MAVLINK *find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint32_t &sysid);
 
 #if AP_MAVLINK_SIGNING_ENABLED
     // update signing timestamp on GPS lock
@@ -681,7 +701,7 @@ class GCS_MAVLINK
 
     void handle_statustext(const mavlink_message_t &msg);
     struct {
-        uint8_t last_src_system;
+        uint32_t last_src_system;
         uint8_t last_src_component;
         uint8_t last_id; // ID from the mavlink packet
         uint8_t msg_id;  // ID used in our logs
@@ -983,7 +1003,7 @@ class GCS_MAVLINK
         mavlink_channel_t chan;
         int16_t param_index;
         char param_name[AP_MAX_NAME_SIZE+1];
-        uint8_t src_system_id;
+        uint32_t src_system_id;
         uint8_t src_component_id;
     };
 
@@ -994,7 +1014,7 @@ class GCS_MAVLINK
         int16_t param_index;
         uint16_t count;
         char param_name[AP_MAX_NAME_SIZE+1];
-        uint8_t src_system_id;
+        uint32_t src_system_id;
         uint8_t src_component_id;
         MAV_PARAM_ERROR param_error;
     };
@@ -1176,7 +1196,7 @@ class GCS
     /*
       return true if a MAVLink system ID is a GCS
      */
-    bool sysid_is_gcs(uint8_t sysid) const;
+    bool sysid_is_gcs(uint32_t sysid) const;
 
     // last time traffic was seen from my designated GCS.  traffic
     // includes heartbeats and some manual control messages.
@@ -1302,7 +1322,7 @@ class GCS
     bool get_high_latency_status();
 #endif // HAL_HIGH_LATENCY2_ENABLED
 
-    uint8_t sysid_this_mav() const { return sysid; }
+    uint32_t sysid_this_mav() const { return sysid; }
     uint32_t telem_delay() const { return mav_telem_delay; }
 
 #if AP_SCRIPTING_ENABLED
@@ -1330,9 +1350,9 @@ class GCS
     GCS_MAVLINK *_chan[MAVLINK_COMM_NUM_BUFFERS];
 
     // parameters
-    AP_Int16                 sysid;
-    AP_Int16                 mav_gcs_sysid;
-    AP_Int16                 mav_gcs_sysid_high;
+    AP_Int32                 sysid;
+    AP_Int32                 mav_gcs_sysid;
+    AP_Int32                 mav_gcs_sysid_high;
     AP_Enum16<Option>        mav_options;
     AP_Int8                  mav_telem_delay;
 
diff --git a/libraries/GCS_MAVLink/GCS_Common.cpp b/libraries/GCS_MAVLink/GCS_Common.cpp
index 316c7eae5db5b..c1f63e0bacfe4 100644
--- a/libraries/GCS_MAVLink/GCS_Common.cpp
+++ b/libraries/GCS_MAVLink/GCS_Common.cpp
@@ -1470,7 +1470,7 @@ bool GCS_MAVLINK_InProgress::conclude(MAV_RESULT result)
     return true;
 }
 
-GCS_MAVLINK_InProgress *GCS_MAVLINK_InProgress::get_task(MAV_CMD mav_cmd, GCS_MAVLINK_InProgress::Type t, uint8_t sysid, uint8_t compid, mavlink_channel_t chan)
+GCS_MAVLINK_InProgress *GCS_MAVLINK_InProgress::get_task(MAV_CMD mav_cmd, GCS_MAVLINK_InProgress::Type t, uint32_t sysid, uint8_t compid, mavlink_channel_t chan)
 {
     // we can't have two outstanding tasks for the same command from
     // the same mavlink node or the result is ambiguous:
@@ -3799,7 +3799,7 @@ void GCS_MAVLINK::handle_timesync(const mavlink_message_t &msg)
                 "TimeUS,SysID,RTT",
                 "s-s",
                 "F-F",
-                "QBQ",
+                "QIQ",
                 AP_HAL::micros64(),
                 msg.sysid,
                 round_trip_time_us
@@ -3875,7 +3875,7 @@ void GCS_MAVLINK::handle_statustext(const mavlink_message_t &msg)
             offset = hal.util->snprintf(text,
                                         max_prefix_len,
                                         "SRC=%u/%u:",
-                                        msg.sysid,
+                                        (unsigned)msg.sysid,
                                         msg.compid);
             offset = MIN(offset, max_prefix_len);
         }
@@ -3902,7 +3902,7 @@ void GCS_MAVLINK::handle_named_value(const mavlink_message_t &msg) const
     mavlink_msg_named_value_float_decode(&msg, &p);
     char s[11] {};
     strncpy(s, p.name, sizeof(s)-1);
-    logger->Write("NVAL", "TimeUS,TimeBootMS,Name,Value,SSys,SCom", "ss#---", "FC----", "QINfBB",
+    logger->Write("NVAL", "TimeUS,TimeBootMS,Name,Value,SSys,SCom", "ss#---", "FC----", "QINfIB",
                   AP_HAL::micros64(),
                   p.time_boot_ms,
                   s,
@@ -5441,7 +5441,8 @@ void GCS_MAVLINK::handle_command_long(const mavlink_message_t &msg)
     // log the packet:
     mavlink_command_int_t packet_int;
     convert_COMMAND_LONG_to_COMMAND_INT(packet, packet_int);
-    AP::logger().Write_Command(packet_int, msg.sysid, msg.compid, result, true);
+    AP::logger().Write_Command(packet_int, mavlink_msg_command_long_get_target_system(&msg),
+                               msg.sysid, msg.compid, result, true);
 #endif
 
     hal.util->persistent_data.last_mavlink_cmd = 0;
@@ -5660,8 +5661,9 @@ MAV_RESULT GCS_MAVLINK::handle_command_do_follow(const mavlink_command_int_t &pa
     }
 
     // param1: sysid of target to follow
-    if ((packet.param1 > 0) && (packet.param1 <= 255)) {
-        follow->set_target_sysid((uint8_t)packet.param1);
+    const int64_t sysid = (int64_t)packet.param1;
+    if (sysid > 0 && sysid <= (int64_t)0xFFFFFFFF) {
+        follow->set_target_sysid((uint32_t)sysid);
         return MAV_RESULT_ACCEPTED;
     }
     return MAV_RESULT_DENIED;
@@ -5931,7 +5933,8 @@ void GCS_MAVLINK::handle_command_int(const mavlink_message_t &msg)
                                  msg.compid);
 
 #if HAL_LOGGING_ENABLED
-    AP::logger().Write_Command(packet, msg.sysid, msg.compid, result);
+    AP::logger().Write_Command(packet, mavlink_msg_command_int_get_target_system(&msg),
+                               msg.sysid, msg.compid, result);
 #endif
 
     hal.util->persistent_data.last_mavlink_cmd = 0;
@@ -6342,7 +6345,7 @@ void GCS_MAVLINK::send_gimbal_manager_status() const
 }
 #endif
 
-void GCS_MAVLINK::send_set_position_target_global_int(uint8_t target_system, uint8_t target_component, const Location& loc)
+void GCS_MAVLINK::send_set_position_target_global_int(uint32_t target_system, uint8_t target_component, const Location& loc)
 {
 
     const uint16_t type_mask = POSITION_TARGET_TYPEMASK_VX_IGNORE | POSITION_TARGET_TYPEMASK_VY_IGNORE | POSITION_TARGET_TYPEMASK_VZ_IGNORE | \
@@ -7642,7 +7645,8 @@ void GCS_MAVLINK::handle_manual_control(const mavlink_message_t &msg)
     mavlink_manual_control_t packet;
     mavlink_msg_manual_control_decode(&msg, &packet);
 
-    if (packet.target != gcs().sysid_this_mav()) {
+    // use the getter as the target may be in the extended header
+    if (mavlink_msg_manual_control_get_target(&msg) != gcs().sysid_this_mav()) {
         return; // only accept control aimed at us
     }
 
diff --git a/libraries/GCS_MAVLink/GCS_FTP.cpp b/libraries/GCS_MAVLink/GCS_FTP.cpp
index 09875323d752b..3ecd8697ac76e 100644
--- a/libraries/GCS_MAVLink/GCS_FTP.cpp
+++ b/libraries/GCS_MAVLink/GCS_FTP.cpp
@@ -110,7 +110,8 @@ bool GCS_FTP::send_reply(const Transaction &reply)
     }
     mavlink_file_transfer_protocol_t pkt {};
     pkt.target_network = 0;
-    pkt.target_system = reply.sysid;
+    // targets > 255 travel in the extended header
+    pkt.target_system = reply.sysid>255?0:reply.sysid;
     pkt.target_component = reply.compid;
     uint8_t *payload = pkt.payload;
     put_le16_ptr(payload, reply.seq_number);
@@ -121,7 +122,7 @@ bool GCS_FTP::send_reply(const Transaction &reply)
     payload[6] = reply.burst_complete ? 1 : 0;
     put_le32_ptr(&payload[8], reply.offset);
     memcpy(&pkt.payload[12], reply.data, sizeof(reply.data));
-    mavlink_msg_file_transfer_protocol_send_struct(reply.chan, &pkt);
+    mavlink_msg_file_transfer_protocol_send(reply.chan, pkt.target_network, reply.sysid, reply.compid, pkt.payload);
     return true;
 }
 
diff --git a/libraries/GCS_MAVLink/GCS_FTP.h b/libraries/GCS_MAVLink/GCS_FTP.h
index 51f97f25fd290..f77688127a842 100644
--- a/libraries/GCS_MAVLink/GCS_FTP.h
+++ b/libraries/GCS_MAVLink/GCS_FTP.h
@@ -64,7 +64,7 @@ class GCS_FTP {
         bool  burst_complete;
         uint8_t size;
         uint8_t session;
-        uint8_t sysid;
+        uint32_t sysid;
         uint8_t compid;
         uint8_t data[239];
     };
@@ -86,7 +86,7 @@ class GCS_FTP {
         int16_t session_id;
         FTP_FILE_MODE mode; // work around AP_Filesystem not supporting file modes
         mavlink_channel_t chan;
-        uint8_t sysid;
+        uint32_t sysid;
         uint8_t compid;
 
         bool check_name_len(const Transaction &request);
diff --git a/libraries/GCS_MAVLink/GCS_MAVLink.cpp b/libraries/GCS_MAVLink/GCS_MAVLink.cpp
index ffbc50207f575..2584656beff76 100644
--- a/libraries/GCS_MAVLink/GCS_MAVLink.cpp
+++ b/libraries/GCS_MAVLink/GCS_MAVLink.cpp
@@ -81,7 +81,7 @@ mavlink_system_t mavlink_system = {7,1};
 // routing table
 MAVLink_routing GCS_MAVLINK::routing;
 
-GCS_MAVLINK *GCS_MAVLINK::find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint8_t &sysid) {
+GCS_MAVLINK *GCS_MAVLINK::find_by_mavtype_and_compid(uint8_t mav_type, uint8_t compid, uint32_t &sysid) {
     mavlink_channel_t channel;
     if (!routing.find_by_mavtype_and_compid(mav_type, compid, sysid, channel)) {
         return nullptr;
diff --git a/libraries/GCS_MAVLink/GCS_Signing.cpp b/libraries/GCS_MAVLink/GCS_Signing.cpp
index 44396eaf15bb6..fd7854982fb58 100644
--- a/libraries/GCS_MAVLink/GCS_Signing.cpp
+++ b/libraries/GCS_MAVLink/GCS_Signing.cpp
@@ -260,10 +260,22 @@ uint8_t GCS_MAVLINK::packet_overhead_chan(mavlink_channel_t chan)
     }
     
     const mavlink_status_t *status = mavlink_get_channel_status(chan);
+
+    // allow for the sysid32 extended header when our sysid is over
+    // 255, and conservatively for an extended target on any message.
+    // MAVLink1 channels never have extended headers
+    uint8_t ext_header_space = 0;
+    if (status == nullptr || !(status->flags & MAVLINK_STATUS_FLAG_OUT_MAVLINK1)) {
+        ext_header_space = MAVLINK_TARGETTED_HEADER_EXTRA;
+        if (mavlink_system.sysid > 255) {
+            ext_header_space += MAVLINK_SYSID32_HEADER_EXTRA;
+        }
+    }
+
     if ((status != nullptr) && status->signing && (status->signing->flags & MAVLINK_SIGNING_FLAG_SIGN_OUTGOING)) {
-        return MAVLINK_NUM_NON_PAYLOAD_BYTES + MAVLINK_SIGNATURE_BLOCK_LEN + reserved_space;
+        return MAVLINK_NUM_NON_PAYLOAD_BYTES + ext_header_space + MAVLINK_SIGNATURE_BLOCK_LEN + reserved_space;
     }
-    return MAVLINK_NUM_NON_PAYLOAD_BYTES + reserved_space;
+    return MAVLINK_NUM_NON_PAYLOAD_BYTES + ext_header_space + reserved_space;
 }
 
 #if !AP_MAVLINK_SIGNING_ENABLED
diff --git a/libraries/GCS_MAVLink/MAVLink_routing.cpp b/libraries/GCS_MAVLink/MAVLink_routing.cpp
index fa94f111bed31..dad1dfac57fcf 100644
--- a/libraries/GCS_MAVLink/MAVLink_routing.cpp
+++ b/libraries/GCS_MAVLink/MAVLink_routing.cpp
@@ -175,7 +175,7 @@ bool MAVLink_routing::forward(GCS_MAVLINK &in_link,
                               const mavlink_message_t &msg)
 {
     // extract the targets for this packet
-    int16_t target_system = -1;
+    int64_t target_system = -1;
     int16_t target_component = -1;
     get_targets(msg, target_system, target_component);
 
@@ -230,11 +230,11 @@ bool MAVLink_routing::forward(GCS_MAVLINK &in_link,
             if (&in_link != out_link && !sent_to_chan[routes[i].channel]) {
                 if (out_link->check_payload_size(msg.len)) {
 #if ROUTING_DEBUG
-                    ::printf("fwd msg %u from chan %u on chan %u sysid=%d compid=%d\n",
+                    ::printf("fwd msg %u from chan %u on chan %u sysid=%lld compid=%d\n",
                              msg.msgid,
                              (unsigned)in_link.get_chan(),
                              (unsigned)routes[i].channel,
-                             (int)target_system,
+                             (long long)target_system,
                              (int)target_component);
 #endif
                     _mavlink_resend_uart(routes[i].channel, &msg);
@@ -299,12 +299,20 @@ void MAVLink_routing::send_to_components(const char *pkt, const mavlink_msg_entr
                           entry->max_msg_len, pkt_len);
         }
 #endif
-        _mav_finalize_message_chan_send(routes[i].channel,
+        // the target is a component of this system; pass our (possibly
+        // 32 bit) sysid so it can go in the extended header if needed
+        uint8_t target_compid = 0;
+        if (entry->flags & MAV_MSG_ENTRY_FLAG_HAVE_TARGET_COMPONENT) {
+            target_compid = pkt[entry->target_component_ofs];
+        }
+        _mav_finalize_message_chan_send_target(routes[i].channel,
                                         entry->msgid,
                                         pkt,
                                         entry->min_msg_len,
                                         MIN(entry->max_msg_len, pkt_len),
-                                        entry->crc_extra);
+                                        entry->crc_extra,
+                                        mavlink_system.sysid,
+                                        target_compid);
         sent_to_chan[routes[i].channel] = true;
     }
 }
@@ -313,7 +321,7 @@ void MAVLink_routing::send_to_components(const char *pkt, const mavlink_msg_entr
   search for the first vehicle or component in the routing table with given mav_type and retrieve it's sysid, compid and channel
   returns true if a match is found
  */
-bool MAVLink_routing::find_by_mavtype(uint8_t mavtype, uint8_t &sysid, uint8_t &compid, mavlink_channel_t &channel)
+bool MAVLink_routing::find_by_mavtype(uint8_t mavtype, uint32_t &sysid, uint8_t &compid, mavlink_channel_t &channel)
 {
     // check learned routes
     for (uint8_t i=0; i<num_routes; i++) {
@@ -333,7 +341,7 @@ bool MAVLink_routing::find_by_mavtype(uint8_t mavtype, uint8_t &sysid, uint8_t &
   search for the first vehicle or component in the routing table with given mav_type and component id and retrieve its sysid and channel
   returns true if a match is found
  */
-bool MAVLink_routing::find_by_mavtype_and_compid(uint8_t mavtype, uint8_t compid, uint8_t &sysid, mavlink_channel_t &channel) const
+bool MAVLink_routing::find_by_mavtype_and_compid(uint8_t mavtype, uint8_t compid, uint32_t &sysid, mavlink_channel_t &channel) const
 {
     for (uint8_t i=0; i<num_routes; i++) {
         if ((routes[i].mavtype == mavtype) && (routes[i].compid == compid)) {
@@ -451,17 +459,20 @@ void MAVLink_routing::handle_heartbeat(GCS_MAVLINK &link, const mavlink_message_
   that the caller can set them to -1 and know when a sysid or compid
   target is found in the message
 */
-void MAVLink_routing::get_targets(const mavlink_message_t &msg, int16_t &sysid, int16_t &compid)
+void MAVLink_routing::get_targets(const mavlink_message_t &msg, int64_t &sysid, int16_t &compid)
 {
     const mavlink_msg_entry_t *msg_entry = mavlink_get_msg_entry(msg.msgid);
-    if (msg_entry == nullptr) {
+    const bool targetted = (msg.incompat_flags & MAVLINK_IFLAG_TARGETTED) != 0;
+    if (msg_entry == nullptr && !targetted) {
         return;
     }
-    if (msg_entry->flags & MAV_MSG_ENTRY_FLAG_HAVE_TARGET_SYSTEM) {
-        sysid = _MAV_RETURN_uint8_t(&msg,  msg_entry->target_system_ofs);
+    if (targetted ||
+        (msg_entry != nullptr && (msg_entry->flags & MAV_MSG_ENTRY_FLAG_HAVE_TARGET_SYSTEM))) {
+        sysid = mavlink_msg_get_target_sysid(&msg, msg_entry);
     }
-    if (msg_entry->flags & MAV_MSG_ENTRY_FLAG_HAVE_TARGET_COMPONENT) {
-        compid = _MAV_RETURN_uint8_t(&msg,  msg_entry->target_component_ofs);
+    if (targetted ||
+        (msg_entry != nullptr && (msg_entry->flags & MAV_MSG_ENTRY_FLAG_HAVE_TARGET_COMPONENT))) {
+        compid = mavlink_msg_get_target_compid(&msg, msg_entry);
     }
 }
 
diff --git a/libraries/GCS_MAVLink/MAVLink_routing.h b/libraries/GCS_MAVLink/MAVLink_routing.h
index a91c4a30d07e3..4b6b10da048c3 100644
--- a/libraries/GCS_MAVLink/MAVLink_routing.h
+++ b/libraries/GCS_MAVLink/MAVLink_routing.h
@@ -43,20 +43,20 @@ class MAVLink_routing
       search for the first vehicle or component in the routing table with given mav_type and retrieve it's sysid, compid and channel
       returns true if a match is found
      */
-    bool find_by_mavtype(uint8_t mavtype, uint8_t &sysid, uint8_t &compid, mavlink_channel_t &channel);
+    bool find_by_mavtype(uint8_t mavtype, uint32_t &sysid, uint8_t &compid, mavlink_channel_t &channel);
 
     /*
       search for the first vehicle or component in the routing table with given mav_type and component id and retrieve its sysid and channel
       returns true if a match is found
      */
-    bool find_by_mavtype_and_compid(uint8_t mavtype, uint8_t compid, uint8_t &sysid, mavlink_channel_t &channel) const;
+    bool find_by_mavtype_and_compid(uint8_t mavtype, uint8_t compid, uint32_t &sysid, mavlink_channel_t &channel) const;
 
 private:
     // a simple linear routing table. We don't expect to have a lot of
     // routes, so a scalable structure isn't worthwhile yet.
     uint8_t num_routes;
     struct route {
-        uint8_t sysid;
+        uint32_t sysid;
         uint8_t compid;
         mavlink_channel_t channel;
         uint8_t mavtype;
@@ -69,7 +69,7 @@ class MAVLink_routing
     void learn_route(GCS_MAVLINK &link, const mavlink_message_t &msg);
 
     // extract target sysid and compid from a message
-    void get_targets(const mavlink_message_t &msg, int16_t &sysid, int16_t &compid);
+    void get_targets(const mavlink_message_t &msg, int64_t &sysid, int16_t &compid);
 
     // special handling for heartbeat messages
     void handle_heartbeat(GCS_MAVLINK &link, const mavlink_message_t &msg);
diff --git a/libraries/GCS_MAVLink/MissionItemProtocol.cpp b/libraries/GCS_MAVLink/MissionItemProtocol.cpp
index 9e92377e0bb9c..ae1f4e0806594 100644
--- a/libraries/GCS_MAVLink/MissionItemProtocol.cpp
+++ b/libraries/GCS_MAVLink/MissionItemProtocol.cpp
@@ -173,10 +173,11 @@ void MissionItemProtocol::handle_mission_request_int(GCS_MAVLINK &_link,
         return;
     }
 
-    ret_packet.target_system = msg.sysid;
+    // targets > 255 travel in the extended header
+    ret_packet.target_system = msg.sysid>255?0:msg.sysid;
     ret_packet.target_component = msg.compid;
 
-    _link.send_message(MAVLINK_MSG_ID_MISSION_ITEM_INT, (const char*)&ret_packet);
+    _link.send_message_target(MAVLINK_MSG_ID_MISSION_ITEM_INT, (const char*)&ret_packet, msg.sysid, msg.compid);
 }
 
 #if AP_MAVLINK_MSG_MISSION_REQUEST_ENABLED
@@ -196,7 +197,8 @@ void MissionItemProtocol::handle_mission_request(GCS_MAVLINK &_link,
         return;
     }
 
-    item_int.target_system = msg.sysid;
+    // targets > 255 travel in the extended header
+    item_int.target_system = msg.sysid>255?0:msg.sysid;
     item_int.target_component = msg.compid;
 
     mavlink_mission_item_t ret_packet{};
@@ -212,7 +214,7 @@ void MissionItemProtocol::handle_mission_request(GCS_MAVLINK &_link,
     }
 
     // buffer space is checked by send_message
-    _link.send_message(MAVLINK_MSG_ID_MISSION_ITEM, (const char*)&ret_packet);
+    _link.send_message_target(MAVLINK_MSG_ID_MISSION_ITEM, (const char*)&ret_packet, msg.sysid, msg.compid);
 }
 #endif  // AP_MAVLINK_MSG_MISSION_REQUEST_ENABLED
 
diff --git a/libraries/GCS_MAVLink/MissionItemProtocol.h b/libraries/GCS_MAVLink/MissionItemProtocol.h
index ff8a6ae73adbf..bf3e3103e5d73 100644
--- a/libraries/GCS_MAVLink/MissionItemProtocol.h
+++ b/libraries/GCS_MAVLink/MissionItemProtocol.h
@@ -88,7 +88,7 @@ class MissionItemProtocol
     uint16_t        request_i; // request index
 
     // waypoints
-    uint8_t         dest_sysid;  // where to send requests
+    uint32_t        dest_sysid;  // where to send requests
     uint8_t         dest_compid; // "
     uint32_t        timelast_receive_ms;
     uint32_t        timelast_request_ms;

From 363bffeefaabeacfedbd1b8397ac1383acbfa4c7 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:40 +1000
Subject: [PATCH 04/21] AP_Mount: support 32 bit system IDs

Widen gimbal and target sysid storage and pass 32 bit targets via the
extended header aware send path. MAV_CMD_DO_GIMBAL_MANAGER_CONFIGURE
accepts a controller sysid up to 2^24-1, the largest a float command
parameter can carry exactly.
---
 libraries/AP_Mount/AP_Mount.cpp         |  9 +++++++--
 libraries/AP_Mount/AP_Mount.h           |  4 ++--
 libraries/AP_Mount/AP_Mount_Backend.cpp | 14 ++++++++------
 libraries/AP_Mount/AP_Mount_Backend.h   |  8 ++++----
 libraries/AP_Mount/AP_Mount_MAVLink.cpp | 20 ++++++++++----------
 libraries/AP_Mount/AP_Mount_MAVLink.h   |  2 +-
 libraries/AP_Mount/AP_Mount_Params.h    |  2 +-
 libraries/AP_Mount/AP_Mount_SToRM32.h   |  2 +-
 8 files changed, 34 insertions(+), 27 deletions(-)

diff --git a/libraries/AP_Mount/AP_Mount.cpp b/libraries/AP_Mount/AP_Mount.cpp
index df6394b47beda..5ec3b2a51f630 100644
--- a/libraries/AP_Mount/AP_Mount.cpp
+++ b/libraries/AP_Mount/AP_Mount.cpp
@@ -64,6 +64,11 @@ void AP_Mount::init()
     // perform any required parameter conversion
     convert_params();
 
+    // PARAMETER_CONVERSION - Added: Jul-2026 for 32 bit sysids
+    for (uint8_t instance=0; instance<AP_MOUNT_MAX_INSTANCES; instance++) {
+        _params[instance].sysid_default.convert_parameter_width(AP_PARAM_INT8);
+    }
+
     // primary is reset to the first instantiated mount
     bool primary_set = false;
 
@@ -548,7 +553,7 @@ void AP_Mount::handle_gimbal_manager_set_pitchyaw(const mavlink_message_t &msg)
 
 MAV_RESULT AP_Mount::handle_command_do_set_roi_sysid(const mavlink_command_int_t &packet)
 {
-    set_target_sysid((uint8_t)packet.param1);
+    set_target_sysid((uint32_t)packet.param1);
     return MAV_RESULT_ACCEPTED;
 }
 
@@ -804,7 +809,7 @@ void AP_Mount::write_log(uint8_t instance, uint64_t timestamp_us)
 #endif
 
 // point at system ID sysid
-void AP_Mount::set_target_sysid(uint8_t instance, uint8_t sysid)
+void AP_Mount::set_target_sysid(uint8_t instance, uint32_t sysid)
 {
     auto *backend = get_instance(instance);
     if (backend == nullptr) {
diff --git a/libraries/AP_Mount/AP_Mount.h b/libraries/AP_Mount/AP_Mount.h
index 2b601562b6770..98c57531948fa 100644
--- a/libraries/AP_Mount/AP_Mount.h
+++ b/libraries/AP_Mount/AP_Mount.h
@@ -208,8 +208,8 @@ class AP_Mount
     void clear_roi_target(uint8_t instance);
 
     // point at system ID sysid
-    void set_target_sysid(uint8_t sysid) { set_target_sysid(_primary, sysid); }
-    void set_target_sysid(uint8_t instance, uint8_t sysid);
+    void set_target_sysid(uint32_t sysid) { set_target_sysid(_primary, sysid); }
+    void set_target_sysid(uint8_t instance, uint32_t sysid);
 
     // handling of set_roi_sysid message
     MAV_RESULT handle_command_do_set_roi_sysid(const mavlink_command_int_t &packet);
diff --git a/libraries/AP_Mount/AP_Mount_Backend.cpp b/libraries/AP_Mount/AP_Mount_Backend.cpp
index 653981f64c759..bbd223b23dc4e 100644
--- a/libraries/AP_Mount/AP_Mount_Backend.cpp
+++ b/libraries/AP_Mount/AP_Mount_Backend.cpp
@@ -394,7 +394,7 @@ void AP_Mount_Backend::set_roi_target_wpnext_offset(const Vector3f &rpy)
 #endif  // AP_MOUNT_ROI_WPNEXT_OFFSET_ENABLED
 
 // set_sys_target - sets system that mount should attempt to point towards
-void AP_Mount_Backend::set_target_sysid(uint8_t sysid)
+void AP_Mount_Backend::set_target_sysid(uint32_t sysid)
 {
     _target_sysid = sysid;
 
@@ -536,7 +536,7 @@ void AP_Mount_Backend::send_gimbal_manager_status(mavlink_channel_t chan)
                                            AP_HAL::millis(),    // autopilot system time
                                            flags,               // bitmap of gimbal manager flags
                                            _instance + 1,       // gimbal device id
-                                           mavlink_control_id.sysid,    // primary control system id
+                                           mavlink_control_id.sysid>255?0:mavlink_control_id.sysid,    // primary control system id (8 bit only in this message)
                                            mavlink_control_id.compid,   // primary control component id
                                            0,                           // secondary control system id
                                            0);                          // secondary control component id
@@ -606,8 +606,10 @@ MAV_RESULT AP_Mount_Backend::handle_command_do_mount_control(const mavlink_comma
 // requires original message in order to extract caller's sysid and compid
 MAV_RESULT AP_Mount_Backend::handle_command_do_gimbal_manager_configure(const mavlink_command_int_t &packet, const mavlink_message_t &msg)
 {
-    // sanity check param1 and param2 values
-    if ((packet.param1 < -3) || (packet.param1 > UINT8_MAX) || (packet.param2 < -3) || (packet.param2 > UINT8_MAX)) {
+    // sanity check param1 and param2 values. param1 is a system ID, which a
+    // float parameter can only carry exactly up to 2^24-1; param2 is a compid
+    if ((packet.param1 < -3) || (packet.param1 > float((1U<<24)-1)) ||
+        (packet.param2 < -3) || (packet.param2 > UINT8_MAX)) {
         return MAV_RESULT_FAILED;
     }
 
@@ -615,7 +617,7 @@ MAV_RESULT AP_Mount_Backend::handle_command_do_gimbal_manager_configure(const ma
     mavlink_control_id_t prev_control_id = mavlink_control_id;
 
     // convert negative packet1 and packet2 values
-    int16_t new_sysid = packet.param1;
+    int64_t new_sysid = packet.param1;
     switch (new_sysid) {
         case -1:
             // leave unchanged
@@ -647,7 +649,7 @@ MAV_RESULT AP_Mount_Backend::handle_command_do_gimbal_manager_configure(const ma
 }
 
 // handle a GLOBAL_POSITION_INT message
-bool AP_Mount_Backend::handle_global_position_int(uint8_t msg_sysid, const mavlink_global_position_int_t &packet)
+bool AP_Mount_Backend::handle_global_position_int(uint32_t msg_sysid, const mavlink_global_position_int_t &packet)
 {
     if (_target_sysid != msg_sysid) {
         return false;
diff --git a/libraries/AP_Mount/AP_Mount_Backend.h b/libraries/AP_Mount/AP_Mount_Backend.h
index 2cc192fe4c684..81926664e9099 100644
--- a/libraries/AP_Mount/AP_Mount_Backend.h
+++ b/libraries/AP_Mount/AP_Mount_Backend.h
@@ -119,7 +119,7 @@ class AP_Mount_Backend
     void clear_roi_target();
 
     // set_sys_target - sets system that mount should attempt to point towards
-    void set_target_sysid(uint8_t sysid);
+    void set_target_sysid(uint32_t sysid);
 
 #if AP_MOUNT_ROI_WPNEXT_OFFSET_ENABLED
     // set_roi_target_wpnext_offset - point to next waypoint, with offsets
@@ -152,7 +152,7 @@ class AP_Mount_Backend
     virtual void handle_param_value(const mavlink_message_t &msg) {}
 
     // handle a GLOBAL_POSITION_INT message
-    bool handle_global_position_int(uint8_t msg_sysid, const mavlink_global_position_int_t &packet);
+    bool handle_global_position_int(uint32_t msg_sysid, const mavlink_global_position_int_t &packet);
 
     // handle GIMBAL_DEVICE_INFORMATION message
     virtual void handle_gimbal_device_information(const mavlink_message_t &msg) {}
@@ -483,7 +483,7 @@ class AP_Mount_Backend
     Vector3f _roi_wpnext_rpy;       // angular offsets for pointing-at-waypoint
 #endif  // AP_MOUNT_ROI_WPNEXT_OFFSET_ENABLED
 
-    uint8_t _target_sysid;          // sysid to track
+    uint32_t _target_sysid;         // sysid to track
     Location _target_sysid_location;// sysid target location
 
     uint32_t _last_warning_ms;      // system time of last warning sent to GCS
@@ -499,7 +499,7 @@ class AP_Mount_Backend
     // structure holding mavlink sysid and compid of controller of this gimbal
     // see MAV_CMD_DO_GIMBAL_MANAGER_CONFIGURE and GIMBAL_MANAGER_STATUS
     struct mavlink_control_id_t {
-        uint8_t sysid;
+        uint32_t sysid;
         uint8_t compid;
 
         // equality operators
diff --git a/libraries/AP_Mount/AP_Mount_MAVLink.cpp b/libraries/AP_Mount/AP_Mount_MAVLink.cpp
index ea2a73575edd0..0bb95082a1ff1 100644
--- a/libraries/AP_Mount/AP_Mount_MAVLink.cpp
+++ b/libraries/AP_Mount/AP_Mount_MAVLink.cpp
@@ -183,12 +183,12 @@ void AP_Mount_MAVLink::request_gimbal_device_information() const
         0,  // param6
         0,  // param7
         MAV_CMD_REQUEST_MESSAGE,
-        _sysid,
+        uint8_t(_sysid>255?0:_sysid),  // targets > 255 travel in the extended header
         _compid,
         0  // confirmation
     };
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 }
 
 // start sending ATTITUDE and AUTOPILOT_STATE_FOR_GIMBAL_DEVICE to gimbal
@@ -219,11 +219,11 @@ void AP_Mount_MAVLink::send_target_retracted()
         0,  // angular velocity y
         0,    // angular velocity z
         GIMBAL_DEVICE_FLAGS_RETRACT,  // flags
-        _sysid,
+        uint8_t(_sysid>255?0:_sysid),  // targets > 255 travel in the extended header
         _compid
     };
 
-    _link->send_message(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt, _sysid, _compid);
 }
 
 // send GIMBAL_DEVICE_SET_ATTITUDE to gimbal to control rate
@@ -243,11 +243,11 @@ void AP_Mount_MAVLink::send_target_rates(const MountRateTarget &rate_rads)
         pitch_rads,  // angular velocity y
         yaw_rads,    // angular velocity z
         flags,
-        _sysid,
+        uint8_t(_sysid>255?0:_sysid),  // targets > 255 travel in the extended header
         _compid
     };
 
-    _link->send_message(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt, _sysid, _compid);
 }
 
 // send GIMBAL_DEVICE_SET_ATTITUDE to gimbal to control attitude
@@ -276,11 +276,11 @@ void AP_Mount_MAVLink::send_target_angles(const MountAngleTarget &angle_rad)
         NAN,  // angular velocity y
         NAN,  // angular velocity z
         flags,
-        _sysid,
+        uint8_t(_sysid>255?0:_sysid),  // targets > 255 travel in the extended header
         _compid
     };
 
-    _link->send_message(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE, (const char*)&pkt, _sysid, _compid);
 }
 
 // Send MAV_CMD_DO_SET_ROI_LOCATION  to gimbal
@@ -291,7 +291,7 @@ void AP_Mount_MAVLink::send_target_location(const Location &roi_loc)
     }
 
     mavlink_command_int_t pkt {};
-    pkt.target_system = _sysid;
+    pkt.target_system = _sysid>255?0:_sysid;  // targets > 255 travel in the extended header
     pkt.target_component = _compid;
 
     if (roi_loc.initialised()) {
@@ -304,7 +304,7 @@ void AP_Mount_MAVLink::send_target_location(const Location &roi_loc)
         pkt.command = MAV_CMD_DO_SET_ROI_NONE;
     }
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_INT, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_INT, (const char*)&pkt, _sysid, _compid);
 }
 
 #endif // HAL_MOUNT_MAVLINK_ENABLED
diff --git a/libraries/AP_Mount/AP_Mount_MAVLink.h b/libraries/AP_Mount/AP_Mount_MAVLink.h
index 9914790d7061b..4bdb21a516d03 100644
--- a/libraries/AP_Mount/AP_Mount_MAVLink.h
+++ b/libraries/AP_Mount/AP_Mount_MAVLink.h
@@ -98,7 +98,7 @@ class AP_Mount_MAVLink : public AP_Mount_Backend
     bool _initialised;              // true once the gimbal has provided a GIMBAL_DEVICE_INFORMATION
     uint32_t _last_devinfo_req_ms;  // system time that GIMBAL_DEVICE_INFORMATION was last requested (used to throttle requests)
     class GCS_MAVLINK *_link;       // link we have found gimbal on; nullptr if not seen yet
-    uint8_t _sysid;                 // sysid of gimbal
+    uint32_t _sysid;                // sysid of gimbal
     uint8_t _compid;                // component id of gimbal
     mavlink_gimbal_device_attitude_status_t _gimbal_device_attitude_status;  // copy of most recently received gimbal status
     uint32_t _last_attitude_status_ms;  // system time last attitude status was received (used for health reporting)
diff --git a/libraries/AP_Mount/AP_Mount_Params.h b/libraries/AP_Mount/AP_Mount_Params.h
index ccf42c1fe050c..7be1694c069da 100644
--- a/libraries/AP_Mount/AP_Mount_Params.h
+++ b/libraries/AP_Mount/AP_Mount_Params.h
@@ -29,7 +29,7 @@ class AP_Mount_Params {
 
     AP_Float    roll_stb_lead;      // roll lead control gain (only used by servo backend)
     AP_Float    pitch_stb_lead;     // pitch lead control gain (only used by servo backend)
-    AP_Int8     sysid_default;      // target sysid for mount to follow
+    AP_Int32    sysid_default;      // target sysid for mount to follow
     AP_Int32    dev_id;             // Device id taking into account bus
     AP_Int8     options;            // mount options bitmask
 };
diff --git a/libraries/AP_Mount/AP_Mount_SToRM32.h b/libraries/AP_Mount/AP_Mount_SToRM32.h
index 9ea963bc6e09d..be95c49657840 100644
--- a/libraries/AP_Mount/AP_Mount_SToRM32.h
+++ b/libraries/AP_Mount/AP_Mount_SToRM32.h
@@ -50,7 +50,7 @@ class AP_Mount_SToRM32 : public AP_Mount_Backend
 
     // internal variables
     bool _initialised;              // true once the driver has been initialised
-    uint8_t _sysid;                 // sysid of gimbal
+    uint32_t _sysid;                // sysid of gimbal
     uint8_t _compid;                // component id of gimbal
     mavlink_channel_t _chan = MAVLINK_COMM_0;        // mavlink channel used to communicate with gimbal
 };

From 150f53c273c73e20859f03f6cf6ec915ba90541f Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:40 +1000
Subject: [PATCH 05/21] AP_Camera: support 32 bit system IDs

---
 .../AP_Camera/AP_Camera_MAVLinkCamV2.cpp      | 20 +++++++++----------
 libraries/AP_Camera/AP_Camera_MAVLinkCamV2.h  |  2 +-
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.cpp b/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.cpp
index b89c7be9e3623..3125686149da0 100644
--- a/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.cpp
+++ b/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.cpp
@@ -29,13 +29,13 @@ bool AP_Camera_MAVLinkCamV2::trigger_pic()
 
     // prepare and send message
     mavlink_command_long_t pkt {};
-    pkt.target_system = _sysid;
+    pkt.target_system = _sysid>255?0:_sysid;  // targets > 255 travel in the extended header
     pkt.target_component = _compid;
     pkt.command = MAV_CMD_IMAGE_START_CAPTURE;
     pkt.param3 = 1;             // number of images to take
     pkt.param4 = image_index+1; // starting sequence number
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 
     return true;
 }
@@ -51,7 +51,7 @@ bool AP_Camera_MAVLinkCamV2::record_video(bool start_recording)
 
     // prepare and send message
     mavlink_command_long_t pkt {};
-    pkt.target_system = _sysid;
+    pkt.target_system = _sysid>255?0:_sysid;  // targets > 255 travel in the extended header
     pkt.target_component = _compid;
 
     if (start_recording) {
@@ -63,7 +63,7 @@ bool AP_Camera_MAVLinkCamV2::record_video(bool start_recording)
         // param1 = 0, video stream id. 0 for all streams
     }
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 
     return true;
 }
@@ -78,7 +78,7 @@ bool AP_Camera_MAVLinkCamV2::set_zoom(ZoomType zoom_type, float zoom_value)
 
     // prepare and send message
     mavlink_command_long_t pkt {};
-    pkt.target_system = _sysid;
+    pkt.target_system = _sysid>255?0:_sysid;  // targets > 255 travel in the extended header
     pkt.target_component = _compid;
     pkt.command = MAV_CMD_SET_CAMERA_ZOOM;
     switch (zoom_type) {
@@ -91,7 +91,7 @@ bool AP_Camera_MAVLinkCamV2::set_zoom(ZoomType zoom_type, float zoom_value)
     }
     pkt.param2 = zoom_value;            // Zoom Value
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 
     return true;
 }
@@ -107,7 +107,7 @@ SetFocusResult AP_Camera_MAVLinkCamV2::set_focus(FocusType focus_type, float foc
 
     // prepare and send message
     mavlink_command_long_t pkt {};
-    pkt.target_system = _sysid;
+    pkt.target_system = _sysid>255?0:_sysid;  // targets > 255 travel in the extended header
     pkt.target_component = _compid;
     pkt.command = MAV_CMD_SET_CAMERA_FOCUS;
     switch (focus_type) {
@@ -126,7 +126,7 @@ SetFocusResult AP_Camera_MAVLinkCamV2::set_focus(FocusType focus_type, float foc
     }
     pkt.param2 = focus_value;
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 
     return SetFocusResult::ACCEPTED;
 }
@@ -242,12 +242,12 @@ void AP_Camera_MAVLinkCamV2::request_camera_information() const
         0,  // param6
         0,  // param7
         MAV_CMD_REQUEST_MESSAGE,
-        _sysid,
+        uint8_t(_sysid>255?0:_sysid),  // targets > 255 travel in the extended header
         _compid,
         0  // confirmation
     };
 
-    _link->send_message(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt);
+    _link->send_message_target(MAVLINK_MSG_ID_COMMAND_LONG, (const char*)&pkt, _sysid, _compid);
 }
 
 #endif // AP_CAMERA_MAVLINKCAMV2_ENABLED
diff --git a/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.h b/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.h
index 44949bc02f1fd..1425fc5e392bd 100644
--- a/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.h
+++ b/libraries/AP_Camera/AP_Camera_MAVLinkCamV2.h
@@ -70,7 +70,7 @@ class AP_Camera_MAVLinkCamV2 : public AP_Camera_Backend
     mavlink_camera_information_t _cam_info {}; // latest camera information received from camera
     uint32_t _last_caminfo_req_ms;  // system time that CAMERA_INFORMATION was last requested (used to throttle requests)
     class GCS_MAVLINK *_link;   // link we have found the camera on. nullptr if not seen yet
-    uint8_t _sysid;             // sysid of camera
+    uint32_t _sysid;            // sysid of camera
     uint8_t _compid;            // component id of gimbal
 };
 

From 7e52c926d065f41895dddffff34b2e65948709cd Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:40 +1000
Subject: [PATCH 06/21] AP_AccelCal: support 32 bit system IDs

---
 libraries/AP_AccelCal/AP_AccelCal.cpp | 4 ++--
 libraries/AP_AccelCal/AP_AccelCal.h   | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libraries/AP_AccelCal/AP_AccelCal.cpp b/libraries/AP_AccelCal/AP_AccelCal.cpp
index 068308ab2125d..965ec5094f57f 100644
--- a/libraries/AP_AccelCal/AP_AccelCal.cpp
+++ b/libraries/AP_AccelCal/AP_AccelCal.cpp
@@ -183,7 +183,7 @@ void AP_AccelCal::update()
     }
 }
 
-void AP_AccelCal::start(GCS_MAVLINK *gcs, uint8_t sysid, uint8_t compid)
+void AP_AccelCal::start(GCS_MAVLINK *gcs, uint32_t sysid, uint8_t compid)
 {
     if (gcs == nullptr || _started) {
         return;
@@ -364,7 +364,7 @@ bool AP_AccelCal::client_active(uint8_t client_num)
 }
 
 #if HAL_GCS_ENABLED
-void AP_AccelCal::handle_command_ack(const mavlink_command_ack_t &packet, uint8_t src_sysid, uint8_t src_compid)
+void AP_AccelCal::handle_command_ack(const mavlink_command_ack_t &packet, uint32_t src_sysid, uint8_t src_compid)
 {
     if(_sysid != src_sysid || _compid != src_compid) {
         return;
diff --git a/libraries/AP_AccelCal/AP_AccelCal.h b/libraries/AP_AccelCal/AP_AccelCal.h
index be87f690a06b3..73be7cf3c8747 100644
--- a/libraries/AP_AccelCal/AP_AccelCal.h
+++ b/libraries/AP_AccelCal/AP_AccelCal.h
@@ -28,7 +28,7 @@ class AP_AccelCal {
     { update_status(); }
 
     // start all the registered calibrations
-    void start(GCS_MAVLINK *gcs, uint8_t sysid, uint8_t compid);
+    void start(GCS_MAVLINK *gcs, uint32_t sysid, uint8_t compid);
 
     // called on calibration cancellation
     void cancel();
@@ -46,7 +46,7 @@ class AP_AccelCal {
     static void register_client(AP_AccelCal_Client* client);
 
 #if HAL_GCS_ENABLED
-    void handle_command_ack(const mavlink_command_ack_t &packet, uint8_t src_sysid, uint8_t src_compid);
+    void handle_command_ack(const mavlink_command_ack_t &packet, uint32_t src_sysid, uint8_t src_compid);
 #endif
 
     // true if we are in a calibration process
@@ -54,7 +54,7 @@ class AP_AccelCal {
 
 private:
     class GCS_MAVLINK *_gcs;
-    uint8_t _sysid;
+    uint32_t _sysid;
     uint8_t _compid;
     bool _use_gcs_snoop;
     bool _waiting_for_mavlink_ack = false;

From 2dc14cb1cd51aaa54bc28c19e451127384efdca8 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 07/21] AP_Logger: support 32 bit system IDs

Widen source/target system IDs in the MAVC log message and the MAVLink
log transfer target. Write_Command() takes the target from the caller,
as the packet's target_system byte is zero when the target travelled in
the extended header.
---
 libraries/AP_Logger/AP_Logger.h           | 5 ++++-
 libraries/AP_Logger/AP_Logger_MAVLink.cpp | 2 +-
 libraries/AP_Logger/AP_Logger_MAVLink.h   | 2 +-
 libraries/AP_Logger/LogFile.cpp           | 5 +++--
 libraries/AP_Logger/LogStructure.h        | 6 +++---
 5 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/libraries/AP_Logger/AP_Logger.h b/libraries/AP_Logger/AP_Logger.h
index e2503a10a6a17..43402d068bd42 100644
--- a/libraries/AP_Logger/AP_Logger.h
+++ b/libraries/AP_Logger/AP_Logger.h
@@ -277,8 +277,11 @@ class AP_Logger
     void Write_Mode(uint8_t mode, const ModeReason reason);
 
     void Write_EntireMission();
+    // target_system must come from the message header, not the packet;
+    // the payload byte is zero when the target is in the extended header
     void Write_Command(const mavlink_command_int_t &packet,
-                       uint8_t source_system,
+                       uint32_t target_system,
+                       uint32_t source_system,
                        uint8_t source_component,
                        MAV_RESULT result,
                        bool was_command_long=false);
diff --git a/libraries/AP_Logger/AP_Logger_MAVLink.cpp b/libraries/AP_Logger/AP_Logger_MAVLink.cpp
index c3670d32087f2..00ba6c6437571 100644
--- a/libraries/AP_Logger/AP_Logger_MAVLink.cpp
+++ b/libraries/AP_Logger/AP_Logger_MAVLink.cpp
@@ -254,7 +254,7 @@ void AP_Logger_MAVLink::handle_ack(const GCS_MAVLINK &link,
             _next_seq_num = 0;
             start_new_log_reset_variables();
             _last_response_time = AP_HAL::millis();
-            Debug("Target: (%u/%u)", _target_system_id, _target_component_id);
+            Debug("Target: (%u/%u)", (unsigned)_target_system_id, _target_component_id);
         }
         return;
     }
diff --git a/libraries/AP_Logger/AP_Logger_MAVLink.h b/libraries/AP_Logger/AP_Logger_MAVLink.h
index 621da879ba455..375c1ba40d2b6 100644
--- a/libraries/AP_Logger/AP_Logger_MAVLink.h
+++ b/libraries/AP_Logger/AP_Logger_MAVLink.h
@@ -119,7 +119,7 @@ class AP_Logger_MAVLink : public AP_Logger_Backend
 
     const GCS_MAVLINK *_link;
 
-    uint8_t _target_system_id;
+    uint32_t _target_system_id;
     uint8_t _target_component_id;
 
     // this controls the maximum number of blocks we will push from
diff --git a/libraries/AP_Logger/LogFile.cpp b/libraries/AP_Logger/LogFile.cpp
index 33da495d640d8..803297fa80e90 100644
--- a/libraries/AP_Logger/LogFile.cpp
+++ b/libraries/AP_Logger/LogFile.cpp
@@ -277,7 +277,8 @@ void AP_Logger::Write_RSSI()
 #endif
 
 void AP_Logger::Write_Command(const mavlink_command_int_t &packet,
-                              uint8_t source_system,
+                              uint32_t target_system,
+                              uint32_t source_system,
                               uint8_t source_component,
                               const MAV_RESULT result,
                               bool was_command_long)
@@ -285,7 +286,7 @@ void AP_Logger::Write_Command(const mavlink_command_int_t &packet,
     const struct log_MAVLink_Command pkt{
         LOG_PACKET_HEADER_INIT(LOG_MAVLINK_COMMAND_MSG),
         time_us         : AP_HAL::micros64(),
-        target_system   : packet.target_system,
+        target_system   : target_system,
         target_component: packet.target_component,
         source_system   : source_system,
         source_component: source_component,
diff --git a/libraries/AP_Logger/LogStructure.h b/libraries/AP_Logger/LogStructure.h
index 5da9588e1d847..c793daeb56078 100644
--- a/libraries/AP_Logger/LogStructure.h
+++ b/libraries/AP_Logger/LogStructure.h
@@ -365,9 +365,9 @@ struct PACKED log_MCU {
 struct PACKED log_MAVLink_Command {
     LOG_PACKET_HEADER;
     uint64_t time_us;
-    uint8_t target_system;
+    uint32_t target_system;
     uint8_t target_component;
-    uint8_t source_system;
+    uint32_t source_system;
     uint8_t source_component;
     uint8_t frame;
     uint16_t command;
@@ -1187,7 +1187,7 @@ LOG_STRUCTURE_FROM_PRECLAND \
       "MCU","Qffff","TimeUS,MTemp,MVolt,MVmin,MVmax", "sOvvv", "F0000", true }, \
 LOG_STRUCTURE_FROM_MISSION \
     { LOG_MAVLINK_COMMAND_MSG, sizeof(log_MAVLink_Command), \
-      "MAVC", "QBBBBBHffffiifBB","TimeUS,TS,TC,SS,SC,Fr,Cmd,P1,P2,P3,P4,X,Y,Z,Res,WL", "s---------------", "F---------------" }, \
+      "MAVC", "QIBIBBHffffiifBB","TimeUS,TS,TC,SS,SC,Fr,Cmd,P1,P2,P3,P4,X,Y,Z,Res,WL", "s---------------", "F---------------" }, \
     { LOG_RADIO_MSG, sizeof(log_Radio), \
       "RAD", "QBBBBBHH", "TimeUS,RSSI,RemRSSI,TxBuf,Noise,RemNoise,RxErrors,Fixed", "s-------", "F-------", true }, \
 LOG_STRUCTURE_FROM_CAMERA \

From 82cf50dcd05d173ec014082a63233cae73017bee Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 08/21] AP_Follow: support 32 bit system IDs

FOLL_SYSID becomes AP_Int32 with parameter width conversion. Values
must stay below 2^24 until the parameter transport moves away from
float32. The conversion runs from the vehicle's load_parameters() as
mode entry at startup can read the parameter.
---
 libraries/AP_Follow/AP_Follow.cpp | 13 +++++++++++--
 libraries/AP_Follow/AP_Follow.h   | 10 ++++++----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/libraries/AP_Follow/AP_Follow.cpp b/libraries/AP_Follow/AP_Follow.cpp
index c541b999cb0de..ceb2ec9abf5eb 100644
--- a/libraries/AP_Follow/AP_Follow.cpp
+++ b/libraries/AP_Follow/AP_Follow.cpp
@@ -83,7 +83,7 @@ const AP_Param::GroupInfo AP_Follow::var_info[] = {
     // @Param: _SYSID
     // @DisplayName: Follow target's mavlink system id
     // @Description: Follow target's mavlink system id
-    // @Range: 0 255
+    // @Range: 0 16777215
     // @User: Standard
     AP_GROUPINFO("_SYSID", 3, AP_Follow, _sysid, 0),
 
@@ -228,6 +228,15 @@ AP_Follow::AP_Follow() :
     AP_Param::setup_object_defaults(this, var_info);
 }
 
+// convert parameters. Must be called before anything reads FOLL_SYSID,
+// which includes mode entry at startup, so this is done from the vehicle's
+// load_parameters() rather than lazily on first use
+void AP_Follow::convert_params()
+{
+    // PARAMETER_CONVERSION - Added: Jul-2026 for 32 bit sysids
+    _sysid.convert_parameter_width(AP_PARAM_INT16);
+}
+
 
 //==============================================================================
 // Target Estimation Update Functions
@@ -558,7 +567,7 @@ bool AP_Follow::should_handle_message(const mavlink_message_t &msg) const
     }
 
     // skip message if not from our target
-    if (_sysid != 0 && msg.sysid != _sysid) {
+    if (_sysid != 0 && msg.sysid != uint32_t(_sysid.get())) {
         return false;
     }
 
diff --git a/libraries/AP_Follow/AP_Follow.h b/libraries/AP_Follow/AP_Follow.h
index 24ee0be15c36f..0dab56adde638 100644
--- a/libraries/AP_Follow/AP_Follow.h
+++ b/libraries/AP_Follow/AP_Follow.h
@@ -68,7 +68,7 @@ class AP_Follow
     bool enabled() const { return _enabled; }
 
     // set which target to follow
-    void set_target_sysid(uint8_t sysid) { _sysid.set(sysid); }
+    void set_target_sysid(uint32_t sysid) { _sysid.set(sysid); }
 
     // Resets the follow mode offsets to zero if they were automatically initialized. Should be called when exiting Follow mode.
     void clear_offsets_if_required();
@@ -83,6 +83,9 @@ class AP_Follow
     // Projects the target’s position, velocity, and heading forward using the latest updates, smoothing with input shaping if necessary 
     void update_estimates();
 
+    // convert parameters, called from the vehicle's load_parameters()
+    void convert_params();
+
     // Retrieves the estimated target position, velocity, and acceleration in the NED frame relative to the origin (units: meters and meters/second).
     bool get_target_pos_vel_accel_NED_m(Vector3p &pos_ned_m, Vector3f &vel_ned_ms, Vector3f &accel_ned_mss) const;
 
@@ -115,7 +118,6 @@ class AP_Follow
     // Accessor Methods
     //==========================================================================
 
-    // get target sysid as a 32 bit number to allow for future expansion of MAV_SYSID
     uint32_t get_target_sysid() const { return (uint32_t)_sysid.get(); }
 
     // get position controller.  this controller is not used within this library but it is convenient to hold it here
@@ -194,7 +196,7 @@ class AP_Follow
     //==========================================================================
 
     AP_Int8     _enabled;           // 1 = Follow mode is enabled; 0 = disabled
-    AP_Int16    _sysid;             // MAVLink system ID of the target (0 = auto-select first sender)
+    AP_Int32    _sysid;             // MAVLink system ID of the target (0 = auto-select first sender)
     AP_Float    _dist_max_m;        // Maximum allowed distance to target in meters; if exceeded, estimation is rejected
     AP_Int8     _offset_type;       // Offset frame type: 0 = NED, 1 = relative to lead vehicle heading
     AP_Vector3f _offset_m;          // Offset from lead vehicle (meters), in NED or FRD frame depending on _offset_type
@@ -237,7 +239,7 @@ class AP_Follow
     Vector3f    _ofs_estimate_accel_ned_mss;    // Estimated acceleration with offsets applied (NED frame)
 
     bool        _automatic_sysid;               // True if target sysid was automatically selected
-    int16_t     _sysid_used;                    // Currently active sysid used for updates
+    int64_t     _sysid_used;                    // Currently active sysid used for updates, -1 when none
     float       _dist_to_target_m;              // Horizontal distance to target, for reporting (meters)
     float       _bearing_to_target_deg;         // Bearing to target from vehicle (degrees, 0 = North)
     bool        _offsets_were_zero;             // True if initial offset was zero before being initialized

From 41d84ad7126361729bae404d03041426cc1ba87d Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 09/21] AP_DDS: support 32 bit system IDs

---
 libraries/AP_DDS/AP_DDS_Client.cpp | 8 ++++----
 libraries/AP_DDS/AP_DDS_Client.h   | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/libraries/AP_DDS/AP_DDS_Client.cpp b/libraries/AP_DDS/AP_DDS_Client.cpp
index ef89c6a0eb5c7..8a7d90a3048e2 100644
--- a/libraries/AP_DDS/AP_DDS_Client.cpp
+++ b/libraries/AP_DDS/AP_DDS_Client.cpp
@@ -1437,10 +1437,10 @@ bool AP_DDS_Client::init_session()
     return true;
 }
 
-void AP_DDS_Client::dds_format_name(char* buf, const char* dds_prefix, const uint8_t sysid, const char* name, bool use_sysid_ns)
+void AP_DDS_Client::dds_format_name(char* buf, const char* dds_prefix, const uint32_t sysid, const char* name, bool use_sysid_ns)
 {
     if (use_sysid_ns) {
-        snprintf(buf, AP_DDS_MAX_NAME_LEN, "%s/%s/v%u/%s", dds_prefix, participant_name_prefix, sysid, name);
+        snprintf(buf, AP_DDS_MAX_NAME_LEN, "%s/%s/v%u/%s", dds_prefix, participant_name_prefix, (unsigned)sysid, name);
     } else {
         snprintf(buf, AP_DDS_MAX_NAME_LEN, "%s/%s/%s", dds_prefix, participant_name_prefix, name);
     }
@@ -1450,7 +1450,7 @@ bool AP_DDS_Client::create()
 {
     WITH_SEMAPHORE(csem);
 
-    const uint8_t sysid = gcs().sysid_this_mav();
+    const uint32_t sysid = gcs().sysid_this_mav();
     const bool use_sysid_ns = use_ns.get() != 0;
 
     // Participant
@@ -1460,7 +1460,7 @@ bool AP_DDS_Client::create()
     };
     char participant_name[AP_DDS_MAX_NAME_LEN];
     if (use_sysid_ns) {
-        snprintf(participant_name, sizeof(participant_name), "%s_v%u", participant_name_prefix, sysid);
+        snprintf(participant_name, sizeof(participant_name), "%s_v%u", participant_name_prefix, (unsigned)sysid);
     } else {
         snprintf(participant_name, sizeof(participant_name), "%s", participant_name_prefix);
     }
diff --git a/libraries/AP_DDS/AP_DDS_Client.h b/libraries/AP_DDS/AP_DDS_Client.h
index c0fad3692b937..9e4908a326ace 100644
--- a/libraries/AP_DDS/AP_DDS_Client.h
+++ b/libraries/AP_DDS/AP_DDS_Client.h
@@ -323,7 +323,7 @@ class AP_DDS_Client
     static constexpr const char *dds_service_reply_prefix = "rr";
     static constexpr const char *participant_name_prefix = "ap";
 
-    static void dds_format_name(char* buf, const char* dds_prefix, uint8_t sysid, const char* name, bool use_sysid_ns);
+    static void dds_format_name(char* buf, const char* dds_prefix, uint32_t sysid, const char* name, bool use_sysid_ns);
 
 
 public:

From e5e6e553f5f67011129bc17ef1ba0d4c8cc90525 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 10/21] AP_CANManager: support 32 bit system IDs

Widen the CAN forwarding requester system ID so replies to a 32 bit
GCS are not aliased.
---
 libraries/AP_CANManager/AP_MAVLinkCAN.cpp | 2 +-
 libraries/AP_CANManager/AP_MAVLinkCAN.h   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libraries/AP_CANManager/AP_MAVLinkCAN.cpp b/libraries/AP_CANManager/AP_MAVLinkCAN.cpp
index ecf1cdb60fe57..87c4779b091fa 100644
--- a/libraries/AP_CANManager/AP_MAVLinkCAN.cpp
+++ b/libraries/AP_CANManager/AP_MAVLinkCAN.cpp
@@ -295,7 +295,7 @@ void AP_MAVLinkCAN::_handle_can_filter_modify(const mavlink_message_t &msg)
 void AP_MAVLinkCAN::can_frame_callback(uint8_t bus, const AP_HAL::CANFrame &frame, AP_HAL::CANIface::CanIOFlags flags)
 {
     mavlink_channel_t chan;
-    uint8_t system_id;
+    uint32_t system_id;
     uint8_t component_id;
     {
         WITH_SEMAPHORE(can_forward.sem);
diff --git a/libraries/AP_CANManager/AP_MAVLinkCAN.h b/libraries/AP_CANManager/AP_MAVLinkCAN.h
index d238d9c889f09..6f80470b34879 100644
--- a/libraries/AP_CANManager/AP_MAVLinkCAN.h
+++ b/libraries/AP_CANManager/AP_MAVLinkCAN.h
@@ -48,7 +48,7 @@ class AP_MAVLinkCAN {
      */
     struct {
         mavlink_channel_t chan;
-        uint8_t system_id;
+        uint32_t system_id;
         uint8_t component_id;
         uint8_t frame_counter;
         uint32_t last_callback_enable_ms;

From 1cabfffaba7e700604cd1c0284fe8218cc19c27a Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 11/21] AP_Scripting: support 32 bit system IDs

---
 .../AP_Scripting/applets/param-lockdown.lua   | 18 +++++-
 .../AP_Scripting/examples/config_profiles.lua |  5 +-
 .../modules/MAVLink/mavlink_msgs.lua          | 60 ++++++++++++++++---
 3 files changed, 72 insertions(+), 11 deletions(-)

diff --git a/libraries/AP_Scripting/applets/param-lockdown.lua b/libraries/AP_Scripting/applets/param-lockdown.lua
index e5a3b74e2e044..8e5611838d7bc 100644
--- a/libraries/AP_Scripting/applets/param-lockdown.lua
+++ b/libraries/AP_Scripting/applets/param-lockdown.lua
@@ -211,12 +211,26 @@ local function update()
             break
         end
 
-        local param_value, _, _, param_id, _ = string.unpack("<fBBc16B", string.sub(msg, 13, 36))
+        -- newer firmware passes a structure with a 4 byte sysid (299
+        -- bytes); older firmware uses a 1 byte sysid (291 bytes)
+        local sysid32_layout = #msg >= 299
+        local payload_ofs = sysid32_layout and 16 or 13
+        local param_value, _, _, param_id, _ = string.unpack("<fBBc16B", string.sub(msg, payload_ofs, payload_ofs + 23))
         param_id = string.gsub(param_id, string.char(0), "")
 
         param_error = handle_param_set(param_id, param_value)
         if param_error ~= 0 then
-           sysid, compid = string.unpack("<BBB", msg, 8)
+           if sysid32_layout then
+              sysid = string.unpack("<I4", msg, 8)
+              if sysid > 255 then
+                 -- scripting cannot send the extended target header yet, and
+                 -- the payload target byte cannot hold a 32 bit sysid
+                 sysid = 0
+              end
+              compid = string.unpack("<B", msg, 12)
+           else
+              sysid, compid = string.unpack("<BB", msg, 8)
+           end
            send_param_error_response(chan, sysid, compid, param_id, param_error)
         end
     end
diff --git a/libraries/AP_Scripting/examples/config_profiles.lua b/libraries/AP_Scripting/examples/config_profiles.lua
index 14d2b67bde4c2..065930308a0ec 100644
--- a/libraries/AP_Scripting/examples/config_profiles.lua
+++ b/libraries/AP_Scripting/examples/config_profiles.lua
@@ -718,7 +718,10 @@ local function handle_param_setting()
       end
 
       if gcs_allow_set == false then -- we are in change of param setting
-         local param_value, _, _, param_id, _ = string.unpack("<fBBc16B", string.sub(msg, 13, 36))
+         -- newer firmware passes a structure with a 4 byte sysid (299
+         -- bytes); older firmware uses a 1 byte sysid (291 bytes)
+         local payload_ofs = (#msg >= 299) and 16 or 13
+         local param_value, _, _, param_id, _ = string.unpack("<fBBc16B", string.sub(msg, payload_ofs, payload_ofs + 23))
          param_id = string.gsub(param_id, string.char(0), "")
 
          handle_param_set(param_id, param_value)
diff --git a/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua b/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
index c9b66e1fd3e80..88eb5d3408c36 100644
--- a/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
+++ b/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
@@ -12,9 +12,20 @@ function mavlink_msgs.get_msgid(msgname)
   return message_map.id
 end
 
+---True when this firmware passes messages with the MAVLink2.1 32 bit
+---sysid mavlink_message_t layout. Older firmware uses a 1 byte sysid and
+---has no trailing extended target fields, giving a 291 byte structure
+---instead of 299, so the same script can work on both
+---@param message any -- encoded message
+---@return boolean
+function mavlink_msgs.sysid32_layout(message)
+  return #message >= 299
+end
+
 ---Return a object containing everything that is not the payload
 ---@param message any -- encoded message
 ---@return table
+---@return integer -- offset of the payload in the message
 function mavlink_msgs.decode_header(message)
   -- build up a map of the result
   local result = {}
@@ -37,13 +48,29 @@ function mavlink_msgs.decode_header(message)
   -- fetch the incompat/compat flags
   result.incompat_flags, result.compat_flags = string.unpack("<BB", message, 5)
 
-  -- fetch seq/sysid/compid
-  result.seq, result.sysid, result.compid = string.unpack("<BBB", message, 7)
+  if not mavlink_msgs.sysid32_layout(message) then
+    -- older firmware with a 1 byte sysid in the structure
+    result.seq, result.sysid, result.compid = string.unpack("<BBB", message, 7)
+    result.msgid = string.unpack("<I3", message, 10)
+    return result, 13
+  end
+
+  -- fetch seq/sysid/compid, sysid is 32 bits to support MAVLink2.1
+  result.seq = string.unpack("<B", message, 7)
+  result.sysid = string.unpack("<I4", message, 8)
+  result.compid = string.unpack("<B", message, 12)
 
   -- fetch the message id
-  result.msgid = string.unpack("<I3", message, 10)
+  result.msgid = string.unpack("<I3", message, 13)
 
-  return result
+  -- extended target from the MAVLink2.1 TARGETTED header, stored at the
+  -- end of the C structure
+  if (result.incompat_flags & 0x04) ~= 0 then
+    result.target_sysid = string.unpack("<I4", message, 295)
+    result.target_compid = string.unpack("<B", message, 299)
+  end
+
+  return result, 16
 end
 
 -- generate the x25crc for a given buffer
@@ -67,7 +94,7 @@ end
 ---@param msg_map table -- table containing message objects with keys of the message ID
 ---@return table|nil -- a table representing the contents of the message, or nill if decode failed
 function mavlink_msgs.decode(message, msg_map)
-  local result = mavlink_msgs.decode_header(message)
+  local result, payload_ofs = mavlink_msgs.decode_header(message)
   local message_map = require("MAVLink/mavlink_msg_" .. msg_map[result.msgid])
   if not message_map then
     -- we don't know how to decode this message, bail on it
@@ -80,7 +107,24 @@ function mavlink_msgs.decode(message, msg_map)
     -- crc of payload and header values
     local crc_buffer
     if result.protocol_version == 2 then
-      crc_buffer = string.sub(message, 4, 12 + result.payload_length)
+      if not mavlink_msgs.sysid32_layout(message) then
+        -- older firmware: structure matches the wire header directly
+        crc_buffer = string.sub(message, 4, 12 + result.payload_length)
+      else
+        -- reconstruct the wire header; the structure holds a 4 byte sysid
+        -- but the wire form is 1 byte unless MAVLINK_IFLAG_SYSID32 is set
+        crc_buffer = string.sub(message, 4, 7)
+        if (result.incompat_flags & 0x02) ~= 0 then
+          crc_buffer = crc_buffer .. string.sub(message, 8, 11)
+        else
+          crc_buffer = crc_buffer .. string.sub(message, 8, 8)
+        end
+        crc_buffer = crc_buffer .. string.sub(message, 12, 15)
+        if (result.incompat_flags & 0x04) ~= 0 then
+          crc_buffer = crc_buffer .. string.sub(message, 295, 299)
+        end
+        crc_buffer = crc_buffer .. string.sub(message, payload_ofs, payload_ofs - 1 + result.payload_length)
+      end
 
     else
       -- V1 does not include all fields on the wire
@@ -90,7 +134,7 @@ function mavlink_msgs.decode(message, msg_map)
       crc_buffer = crc_buffer .. string.char(result.compid)
       crc_buffer = crc_buffer .. string.char(result.msgid)
       if result.payload_length > 0 then
-        crc_buffer = crc_buffer .. string.sub(message, 13, 12 + result.payload_length)
+        crc_buffer = crc_buffer .. string.sub(message, payload_ofs, payload_ofs - 1 + result.payload_length)
       end
 
     end
@@ -104,7 +148,7 @@ function mavlink_msgs.decode(message, msg_map)
   end
 
   -- map all the fields out
-  local offset = 13
+  local offset = payload_ofs
   for _,v in ipairs(message_map.fields) do
     if v[3] then
       result[v[1]] = {}

From 6fb174a237b70a3a4aa32d0a58dcb23c058b8a77 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:41 +1000
Subject: [PATCH 12/21] AP_BattMonitor: support 32 bit system IDs

---
 libraries/AP_BattMonitor/AP_BattMonitor.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libraries/AP_BattMonitor/AP_BattMonitor.cpp b/libraries/AP_BattMonitor/AP_BattMonitor.cpp
index 61554c8d41758..2dbc001028872 100644
--- a/libraries/AP_BattMonitor/AP_BattMonitor.cpp
+++ b/libraries/AP_BattMonitor/AP_BattMonitor.cpp
@@ -1148,7 +1148,7 @@ void AP_BattMonitor::checkPoweringOff(void)
             cmd_msg.command = MAV_CMD_POWER_OFF_INITIATED;
             cmd_msg.param1 = i+1;
             GCS_MAVLINK::send_to_components(MAVLINK_MSG_ID_COMMAND_LONG, (char*)&cmd_msg, sizeof(cmd_msg));
-            GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "Vehicle %d battery %d is powering off", mavlink_system.sysid, i+1);
+            GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "Vehicle %u battery %d is powering off", (unsigned)mavlink_system.sysid, i+1);
 #endif
 
             // only send this once

From f9e92af86c02fcc9b6b9050bd2c472221f747810 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 13/21] AP_Generator: support 32 bit system IDs

Widen the recorded Loweheiser source sysid so the source-match guard
and the commands we send back are not truncated. The LOEC log SI field
widens to uint32 to match.
---
 libraries/AP_Generator/AP_Generator_Loweheiser.cpp | 2 +-
 libraries/AP_Generator/AP_Generator_Loweheiser.h   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libraries/AP_Generator/AP_Generator_Loweheiser.cpp b/libraries/AP_Generator/AP_Generator_Loweheiser.cpp
index a26e46ea8854a..19f3aef424a87 100644
--- a/libraries/AP_Generator/AP_Generator_Loweheiser.cpp
+++ b/libraries/AP_Generator/AP_Generator_Loweheiser.cpp
@@ -504,7 +504,7 @@ void AP_Generator_Loweheiser::command_generator()
             "TimeUS," "SI," "CI," "C," "I," "ES," "GS," "Thr," "Strtr",
             "s"       "-"   "-"   "-"  "#"  "-"   "-"   "-"    "-"     ,
             "F"       "-"   "-"   "-"  "-"  "-"   "-"   "-"    "-"     ,
-            "Q"       "B"   "B"   "I"  "B"  "B"   "B"   "f"    "B"     ,
+            "Q"       "I"   "B"   "I"  "B"  "B"   "B"   "f"    "B"     ,
             AP_HAL::micros64(),
             sysid,
             compid,
diff --git a/libraries/AP_Generator/AP_Generator_Loweheiser.h b/libraries/AP_Generator/AP_Generator_Loweheiser.h
index 041b8d1d9934a..643743df03bca 100644
--- a/libraries/AP_Generator/AP_Generator_Loweheiser.h
+++ b/libraries/AP_Generator/AP_Generator_Loweheiser.h
@@ -103,7 +103,7 @@ class AP_Generator_Loweheiser : public AP_Generator_Backend
     // only process from one source:
     bool seen_good_message;
     const class GCS_MAVLINK *mavlink_channel;
-    uint8_t sysid;
+    uint32_t sysid;
     uint8_t compid;
     uint8_t efi_index;
 

From b9ff0d91dc54deffa31cc86ba4d19564be85b887 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 14/21] AP_OpenDroneID: support 32 bit system IDs

The basic ID packet is sent as a raw struct, so there is no extended
header available for a target sysid over 255; clamp to zero as we do
elsewhere rather than silently truncating.
---
 libraries/AP_OpenDroneID/AP_OpenDroneID.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libraries/AP_OpenDroneID/AP_OpenDroneID.cpp b/libraries/AP_OpenDroneID/AP_OpenDroneID.cpp
index 63ef541649062..1923637a9d831 100644
--- a/libraries/AP_OpenDroneID/AP_OpenDroneID.cpp
+++ b/libraries/AP_OpenDroneID/AP_OpenDroneID.cpp
@@ -135,8 +135,10 @@ void AP_OpenDroneID::set_basic_id() {
     }
     if (id_len > 0) {
         // prepare basic id pkt
-        uint8_t val = gcs().sysid_this_mav();
-        pkt_basic_id.target_system = val;
+        // this packet is sent as a raw struct, so has no extended header
+        // for a target sysid over 255
+        const uint32_t val = gcs().sysid_this_mav();
+        pkt_basic_id.target_system = val>255?0:val;
         pkt_basic_id.target_component = MAV_COMP_ID_ODID_TXRX_1;
         pkt_basic_id.id_type = atoi(id_type);
         pkt_basic_id.ua_type = atoi(ua_type);

From 4900af1e28ce75a68f649ce3651e0418ebdb963b Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 15/21] SITL: support 32 bit system IDs

The ADSB, SoloGimbal, MAVLink gimbal v2 and camera v2 simulators
truncated the vehicle sysid they learn from its heartbeat, matched
commands against the payload target byte (which is zero when the
target travels in the extended header), and addressed replies through
payload structs. The simulated heartbeats are also serialised properly
rather than writing the mavlink_message_t memory as wire bytes, which
is no longer the wire layout now that sysid is 32 bit.
---
 libraries/SITL/SIM_ADSB.cpp            |  6 ++-
 libraries/SITL/SIM_ADSB.h              |  2 +-
 libraries/SITL/SIM_AVT_CM62.h          |  2 +-
 libraries/SITL/SIM_MAVLinkCamV2.cpp    | 25 ++++++------
 libraries/SITL/SIM_MAVLinkCamV2.h      |  6 +--
 libraries/SITL/SIM_MAVLinkGimbalv2.cpp | 55 ++++++++++++--------------
 libraries/SITL/SIM_MAVLinkGimbalv2.h   |  6 +--
 libraries/SITL/SIM_SoloGimbal.cpp      | 47 ++++++++++++----------
 libraries/SITL/SIM_SoloGimbal.h        |  2 +-
 9 files changed, 79 insertions(+), 72 deletions(-)

diff --git a/libraries/SITL/SIM_ADSB.cpp b/libraries/SITL/SIM_ADSB.cpp
index 28cd56a4ccc91..183f57c4b5fea 100644
--- a/libraries/SITL/SIM_ADSB.cpp
+++ b/libraries/SITL/SIM_ADSB.cpp
@@ -216,7 +216,11 @@ void ADSB::send_report(const class Aircraft &aircraft)
                                                   &mavlink.status,
                                                   &msg, &heartbeat);
 
-        write_to_autopilot((char*)&msg.magic, len);
+        uint8_t msgbuf[len];
+        len = mavlink_msg_to_send_buffer(msgbuf, &msg);
+        if (len > 0) {
+            write_to_autopilot((char*)msgbuf, len);
+        }
 
         last_heartbeat_ms = now;
     }
diff --git a/libraries/SITL/SIM_ADSB.h b/libraries/SITL/SIM_ADSB.h
index 488d59b517cdf..02c842cd88809 100644
--- a/libraries/SITL/SIM_ADSB.h
+++ b/libraries/SITL/SIM_ADSB.h
@@ -76,7 +76,7 @@ class ADSB : public SerialDevice {
     
     uint32_t last_heartbeat_ms;
     bool seen_heartbeat = false;
-    uint8_t vehicle_system_id;
+    uint32_t vehicle_system_id;
     uint8_t vehicle_component_id;
 
     struct {
diff --git a/libraries/SITL/SIM_AVT_CM62.h b/libraries/SITL/SIM_AVT_CM62.h
index 7a5ce3abd1ad4..93612f83e9610 100644
--- a/libraries/SITL/SIM_AVT_CM62.h
+++ b/libraries/SITL/SIM_AVT_CM62.h
@@ -57,7 +57,7 @@ class AVT_CM62 : public MAVLinkGimbalv2, public MAVLinkCamV2 {
     void camera_send_mavlink_message(const mavlink_message_t &msg) override {
         send_mavlink_message(msg);
     }
-    uint8_t camera_vehicle_sysid() const override { return vehicle_sysid(); }
+    uint32_t camera_vehicle_sysid() const override { return vehicle_sysid(); }
     mavlink_status_t &camera_mav_status() override { return gimbal_mav_status(); }
 };
 
diff --git a/libraries/SITL/SIM_MAVLinkCamV2.cpp b/libraries/SITL/SIM_MAVLinkCamV2.cpp
index 8575c859c7133..2eba0b915ff4b 100644
--- a/libraries/SITL/SIM_MAVLinkCamV2.cpp
+++ b/libraries/SITL/SIM_MAVLinkCamV2.cpp
@@ -36,7 +36,9 @@ void MAVLinkCamV2::handle_message(const mavlink_message_t &msg)
     }
     mavlink_command_long_t cmd;
     mavlink_msg_command_long_decode(&msg, &cmd);
-    if (cmd.target_system    != camera_vehicle_sysid() ||
+    // use the header-aware getter: the payload byte is zero for a target
+    // over 255
+    if (mavlink_msg_command_long_get_target_system(&msg) != camera_vehicle_sysid() ||
         cmd.target_component != _camera_compid) {
         return;
     }
@@ -110,7 +112,7 @@ void MAVLinkCamV2::send_camera_heartbeat()
     camera_send_mavlink_message(msg);
 }
 
-void MAVLinkCamV2::send_camera_information(uint8_t target_sysid, uint8_t target_compid)
+void MAVLinkCamV2::send_camera_information(uint32_t target_sysid, uint8_t target_compid)
 {
     mavlink_camera_information_t info {};
     info.time_boot_ms     = AP_HAL::millis();
@@ -144,20 +146,19 @@ void MAVLinkCamV2::send_camera_settings()
     camera_send_mavlink_message(msg);
 }
 
-void MAVLinkCamV2::send_camera_command_ack(uint8_t target_sysid, uint8_t target_compid,
+void MAVLinkCamV2::send_camera_command_ack(uint32_t target_sysid, uint8_t target_compid,
                                             MAV_CMD cmd, MAV_RESULT result)
 {
-    mavlink_command_ack_t ack {};
-    ack.command          = (uint16_t)cmd;
-    ack.result           = (uint8_t)result;
-    ack.progress         = 255;
-    ack.target_system    = target_sysid;
-    ack.target_component = target_compid;
-
+    // pack rather than encode so a target over 255 goes in the extended
+    // header rather than being truncated in the payload
     mavlink_message_t msg;
-    mavlink_msg_command_ack_encode_status(
+    mavlink_msg_command_ack_pack_status(
         camera_vehicle_sysid(), _camera_compid,
-        &camera_mav_status(), &msg, &ack);
+        &camera_mav_status(), &msg,
+        (uint16_t)cmd, (uint8_t)result,
+        255,                // progress
+        0,                  // result_param2
+        target_sysid, target_compid);
     camera_send_mavlink_message(msg);
 }
 
diff --git a/libraries/SITL/SIM_MAVLinkCamV2.h b/libraries/SITL/SIM_MAVLinkCamV2.h
index 7b50bbde5ab13..7736b6f4c2b1c 100644
--- a/libraries/SITL/SIM_MAVLinkCamV2.h
+++ b/libraries/SITL/SIM_MAVLinkCamV2.h
@@ -38,14 +38,14 @@ class MAVLinkCamV2 {
 
     // transport — combined device class wires these to the shared serial link
     virtual void camera_send_mavlink_message(const mavlink_message_t &msg) = 0;
-    virtual uint8_t camera_vehicle_sysid() const = 0;
+    virtual uint32_t camera_vehicle_sysid() const = 0;
     virtual mavlink_status_t &camera_mav_status() = 0;
 
 private:
     void send_camera_heartbeat();
-    void send_camera_information(uint8_t target_sysid, uint8_t target_compid);
+    void send_camera_information(uint32_t target_sysid, uint8_t target_compid);
     void send_camera_settings();
-    void send_camera_command_ack(uint8_t target_sysid, uint8_t target_compid,
+    void send_camera_command_ack(uint32_t target_sysid, uint8_t target_compid,
                                   MAV_CMD cmd, MAV_RESULT result);
 
     uint8_t  _camera_compid {MAV_COMP_ID_CAMERA};
diff --git a/libraries/SITL/SIM_MAVLinkGimbalv2.cpp b/libraries/SITL/SIM_MAVLinkGimbalv2.cpp
index 37e39f5476961..a43029aadb669 100644
--- a/libraries/SITL/SIM_MAVLinkGimbalv2.cpp
+++ b/libraries/SITL/SIM_MAVLinkGimbalv2.cpp
@@ -70,8 +70,9 @@ void MAVLinkGimbalv2::handle_message(const mavlink_message_t &msg)
     case MAVLINK_MSG_ID_COMMAND_LONG: {
         mavlink_command_long_t cmd;
         mavlink_msg_command_long_decode(&msg, &cmd);
-        // only handle messages addressed to this gimbal
-        if (cmd.target_system != _vehicle_system_id ||
+        // only handle messages addressed to this gimbal. Use the header-aware
+        // getter: the payload byte is zero for a target over 255
+        if (mavlink_msg_command_long_get_target_system(&msg) != _vehicle_system_id ||
             cmd.target_component != _compid) {
             break;
         }
@@ -88,7 +89,7 @@ void MAVLinkGimbalv2::handle_message(const mavlink_message_t &msg)
     case MAVLINK_MSG_ID_COMMAND_INT: {
         mavlink_command_int_t cmd;
         mavlink_msg_command_int_decode(&msg, &cmd);
-        if (cmd.target_system != _vehicle_system_id ||
+        if (mavlink_msg_command_int_get_target_system(&msg) != _vehicle_system_id ||
             cmd.target_component != _compid) {
             break;
         }
@@ -105,7 +106,7 @@ void MAVLinkGimbalv2::handle_message(const mavlink_message_t &msg)
     case MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE: {
         mavlink_gimbal_device_set_attitude_t cmd;
         mavlink_msg_gimbal_device_set_attitude_decode(&msg, &cmd);
-        if (cmd.target_system != _vehicle_system_id ||
+        if (mavlink_msg_gimbal_device_set_attitude_get_target_system(&msg) != _vehicle_system_id ||
             cmd.target_component != _compid) {
             break;
         }
@@ -292,42 +293,36 @@ void MAVLinkGimbalv2::send_attitude_status()
         q.from_rotation_matrix(body_to_gimbal);
     }
 
-    mavlink_gimbal_device_attitude_status_t status {};
-    status.target_system    = _vehicle_system_id;
-    status.target_component = _vehicle_component_id;
-    status.time_boot_ms     = AP_HAL::millis();
-    status.flags = flags;
-    status.q[0] = q.q1;  // w
-    status.q[1] = q.q2;  // x
-    status.q[2] = q.q3;  // y
-    status.q[3] = q.q4;  // z
-    status.angular_velocity_x = 0.0f;
-    status.angular_velocity_y = 0.0f;
-    status.angular_velocity_z = 0.0f;
-    status.failure_flags = 0;
+    const float qarr[4] { q.q1, q.q2, q.q3, q.q4 };  // w, x, y, z
 
+    // pack rather than encode so a target over 255 goes in the extended
+    // header rather than being truncated in the payload
     mavlink_message_t msg;
-    mavlink_msg_gimbal_device_attitude_status_encode_status(
+    mavlink_msg_gimbal_device_attitude_status_pack_status(
         _vehicle_system_id, _compid,
-        &mav.status, &msg, &status);
+        &mav.status, &msg,
+        _vehicle_system_id, _vehicle_component_id,
+        AP_HAL::millis(), flags, qarr,
+        0.0f, 0.0f, 0.0f,   // angular velocity x, y, z
+        0,                  // failure_flags
+        0.0f, 0.0f,         // delta_yaw, delta_yaw_velocity
+        0);                 // gimbal_device_id
     send_mavlink_message(msg);
 }
 
-void MAVLinkGimbalv2::send_command_ack(uint8_t target_sysid, uint8_t target_compid,
+void MAVLinkGimbalv2::send_command_ack(uint32_t target_sysid, uint8_t target_compid,
                                         MAV_CMD command, MAV_RESULT result)
 {
-    mavlink_command_ack_t ack {};
-    ack.command          = (uint16_t)command;
-    ack.result           = (uint8_t)result;
-    ack.progress         = 255;
-    ack.result_param2    = 0;
-    ack.target_system    = target_sysid;
-    ack.target_component = target_compid;
-
+    // pack rather than encode so a target over 255 goes in the extended
+    // header rather than being truncated in the payload
     mavlink_message_t msg;
-    mavlink_msg_command_ack_encode_status(
+    mavlink_msg_command_ack_pack_status(
         _vehicle_system_id, _compid,
-        &mav.status, &msg, &ack);
+        &mav.status, &msg,
+        (uint16_t)command, (uint8_t)result,
+        255,                // progress
+        0,                  // result_param2
+        target_sysid, target_compid);
     send_mavlink_message(msg);
 }
 
diff --git a/libraries/SITL/SIM_MAVLinkGimbalv2.h b/libraries/SITL/SIM_MAVLinkGimbalv2.h
index f612275efbb8a..72589bd123c78 100644
--- a/libraries/SITL/SIM_MAVLinkGimbalv2.h
+++ b/libraries/SITL/SIM_MAVLinkGimbalv2.h
@@ -54,7 +54,7 @@ class MAVLinkGimbalv2 : public Mount {
     // available to combined classes (e.g. gimbal+camera) for sending messages
     // and accessing transport state
     void send_mavlink_message(const mavlink_message_t &msg);
-    uint8_t vehicle_sysid()  const { return _vehicle_system_id; }
+    uint32_t vehicle_sysid() const { return _vehicle_system_id; }
     uint8_t vehicle_compid() const { return _vehicle_component_id; }
     mavlink_status_t &gimbal_mav_status() { return mav.status; }
 
@@ -68,13 +68,13 @@ class MAVLinkGimbalv2 : public Mount {
     void send_heartbeat();
     void send_gimbal_device_information();
     void send_attitude_status();
-    void send_command_ack(uint8_t target_sysid, uint8_t target_compid,
+    void send_command_ack(uint32_t target_sysid, uint8_t target_compid,
                           MAV_CMD command, MAV_RESULT result);
 
     uint8_t _compid {MAV_COMP_ID_GIMBAL};
 
     bool     _seen_autopilot_heartbeat;
-    uint8_t  _vehicle_system_id;
+    uint32_t _vehicle_system_id;
     uint8_t  _vehicle_component_id;
 
     uint32_t _last_heartbeat_ms;
diff --git a/libraries/SITL/SIM_SoloGimbal.cpp b/libraries/SITL/SIM_SoloGimbal.cpp
index dccf15727249e..55aab0512a142 100644
--- a/libraries/SITL/SIM_SoloGimbal.cpp
+++ b/libraries/SITL/SIM_SoloGimbal.cpp
@@ -191,7 +191,10 @@ void SoloGimbal::send_report(void)
                 case MAVLINK_MSG_ID_PARAM_REQUEST_LIST: {
                     mavlink_param_request_list_t pkt;
                     mavlink_msg_param_request_list_decode(&msg, &pkt);
-                    if (pkt.target_system == 0 && pkt.target_component == MAV_COMP_ID_GIMBAL) {
+                    // use the header-aware getter: the payload byte is zero
+                    // for a target over 255, which would look like a broadcast
+                    if (mavlink_msg_param_request_list_get_target_system(&msg) == 0 &&
+                        pkt.target_component == MAV_COMP_ID_GIMBAL) {
                         // start param send
                         param_send_idx = 0;
                         param_send_last_ms = AP_HAL::millis();
@@ -227,7 +230,11 @@ void SoloGimbal::send_report(void)
                                                   &mavlink.status,
                                                   &msg, &heartbeat);
 
-        mav_socket.send(&msg.magic, len);
+        uint8_t msgbuf[len];
+        len = mavlink_msg_to_send_buffer(msgbuf, &msg);
+        if (len > 0) {
+            mav_socket.send(msgbuf, len);
+        }
         last_heartbeat_ms = now;
     }
 
@@ -246,24 +253,24 @@ void SoloGimbal::send_report(void)
         Vector3f joint_angles;
         gimbal.get_joint_angles(joint_angles);
 
-        mavlink_gimbal_report_t gimbal_report;
-        gimbal_report.target_system = vehicle_system_id;
-        gimbal_report.target_component = vehicle_component_id;
-        gimbal_report.delta_time = delta_time_us * 1e-6;
-        gimbal_report.delta_angle_x = delta_angle.x;
-        gimbal_report.delta_angle_y = delta_angle.y;
-        gimbal_report.delta_angle_z = delta_angle.z;
-        gimbal_report.delta_velocity_x = delta_velocity.x;
-        gimbal_report.delta_velocity_y = delta_velocity.y;
-        gimbal_report.delta_velocity_z = delta_velocity.z;
-        gimbal_report.joint_roll = joint_angles.x;
-        gimbal_report.joint_el = joint_angles.y;
-        gimbal_report.joint_az = joint_angles.z;
-
-        len = mavlink_msg_gimbal_report_encode_status(vehicle_system_id,
-                                                      gimbal_component_id,
-                                                      &mavlink.status,
-                                                      &msg, &gimbal_report);
+        // pack rather than encode so a target over 255 goes in the
+        // extended header rather than being truncated in the payload
+        len = mavlink_msg_gimbal_report_pack_status(vehicle_system_id,
+                                                    gimbal_component_id,
+                                                    &mavlink.status,
+                                                    &msg,
+                                                    vehicle_system_id,
+                                                    vehicle_component_id,
+                                                    delta_time_us * 1e-6,
+                                                    delta_angle.x,
+                                                    delta_angle.y,
+                                                    delta_angle.z,
+                                                    delta_velocity.x,
+                                                    delta_velocity.y,
+                                                    delta_velocity.z,
+                                                    joint_angles.x,
+                                                    joint_angles.y,
+                                                    joint_angles.z);
 
         uint8_t msgbuf[len];
         len = mavlink_msg_to_send_buffer(msgbuf, &msg);
diff --git a/libraries/SITL/SIM_SoloGimbal.h b/libraries/SITL/SIM_SoloGimbal.h
index a87c8ef851561..fa7d57be4cfd3 100644
--- a/libraries/SITL/SIM_SoloGimbal.h
+++ b/libraries/SITL/SIM_SoloGimbal.h
@@ -62,7 +62,7 @@ class SoloGimbal {
     uint32_t last_heartbeat_ms;
     bool seen_heartbeat;
     bool seen_gimbal_control;
-    uint8_t vehicle_system_id;
+    uint32_t vehicle_system_id;
     uint8_t vehicle_component_id;
 
     SocketAPM_native mav_socket{false};

From c9d0397be216aaf043b187c88266adb05396efcc Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 16/21] AP_Periph: support 32 bit system IDs

Writing len bytes from &msg.magic assumed the mavlink_message_t header
matched the wire format. With a 32 bit sysid the struct header is 3
bytes longer than a small-sysid wire header, so the frame was shifted
and lost its last 3 bytes, including the CRC.
---
 Tools/AP_Periph/adsb.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Tools/AP_Periph/adsb.cpp b/Tools/AP_Periph/adsb.cpp
index b0a2637bae003..540cc7694455f 100644
--- a/Tools/AP_Periph/adsb.cpp
+++ b/Tools/AP_Periph/adsb.cpp
@@ -86,7 +86,11 @@ void AP_Periph_FW::adsb_update(void)
                                                        &adsb.status,
                                                        &msg, &heartbeat);
 
-        uart->write((uint8_t*)&msg.magic, len);
+        uint8_t msgbuf[len];
+        len = mavlink_msg_to_send_buffer(msgbuf, &msg);
+        if (len > 0) {
+            uart->write(msgbuf, len);
+        }
     }
 }
 

From 21086d1401bfbcc7e9a6054c66829a7fc0b566aa Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 17/21] autotest: add 32 bit MAV_SYSID test

Reboots with MAV_SYSID 100000, checks the SYSID32 extended header is
used, fetches parameters from a source system over 255, and runs
mission upload and arming checks at the new sysid.
---
 Tools/autotest/rover.py | 65 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/Tools/autotest/rover.py b/Tools/autotest/rover.py
index 7f7f0b8e505f6..b22a32f2fb1f0 100644
--- a/Tools/autotest/rover.py
+++ b/Tools/autotest/rover.py
@@ -6663,6 +6663,70 @@ def TestWebServer(self, url):
 
         self.progress("WebServer tests OK")
 
+    def MAV_SYSID_32bit(self):
+        '''test 32 bit MAV_SYSID'''
+        if not hasattr(mavutil.mavlink, "MAVLINK_IFLAG_SYSID32"):
+            raise NotAchievedException("pymavlink is too old for 32 bit system IDs")
+
+        # sysid values must round-trip losslessly through the float32
+        # parameter transport, so stay below 2^24 for now
+        sysid = 100000
+        self.set_parameter("MAV_SYSID", sysid)
+
+        # the sysid changes across the reboot so we can't use
+        # reboot_sitl(); send the reboot at the old sysid and re-point
+        # the connection at the new one
+        self.send_reboot_command()
+        self.mav.target_system = sysid
+        self.sysid_thismav = lambda: sysid
+        try:
+            self.wait_heartbeat(timeout=60)
+            m = self.wait_heartbeat()
+            if m.get_srcSystem() != sysid:
+                raise NotAchievedException("Did not get 32 bit sysid, got %u" % m.get_srcSystem())
+            hdr = m.get_header()
+            if not (hdr.incompat_flags & mavutil.mavlink.MAVLINK_IFLAG_SYSID32):
+                raise NotAchievedException("expected MAVLINK_IFLAG_SYSID32 to be set")
+
+            # parameter fetch at the new sysid
+            if int(self.get_parameter("MAV_SYSID")) != sysid:
+                raise NotAchievedException("MAV_SYSID readback failed")
+
+            # our own GCS with a 32 bit source system, and a targeted
+            # message each way
+            mav2 = mavutil.mavlink_connection(
+                "tcp:localhost:%u" % self.adjust_ardupilot_port(5763),
+                robust_parsing=True,
+                source_system=70000,
+                source_component=7,
+            )
+            mav2.mav.param_request_read_send(sysid, 1, b"MAV_SYSID", -1)
+            m = mav2.recv_match(type='PARAM_VALUE', blocking=True, timeout=10)
+            if m is None:
+                raise NotAchievedException("no PARAM_VALUE for 32 bit source system")
+            if m.param_id != "MAV_SYSID" or int(m.param_value) != sysid:
+                raise NotAchievedException("bad PARAM_VALUE %s" % str(m))
+            mav2.close()
+
+            # targeted mission-protocol round trip (the mission upload
+            # helpers hard-code target system 1, so do this by hand)
+            self.mav.mav.mission_request_list_send(sysid, 1, mavutil.mavlink.MAV_MISSION_TYPE_MISSION)
+            m = self.assert_receive_message('MISSION_COUNT', timeout=10)
+            if m.mission_type != mavutil.mavlink.MAV_MISSION_TYPE_MISSION:
+                raise NotAchievedException("bad MISSION_COUNT")
+
+            self.wait_ready_to_arm()
+            self.arm_vehicle()
+            self.disarm_vehicle()
+        finally:
+            # restore the old sysid
+            self.set_parameter("MAV_SYSID", 1)
+            self.send_reboot_command()
+            del self.sysid_thismav
+            self.mav.target_system = 1
+            self.wait_heartbeat(timeout=60)
+            self.wait_heartbeat()
+
     def NetworkingWebServer(self):
         '''web server'''
         applet_script = "net_webserver.lua"
@@ -7553,6 +7617,7 @@ def tests(self):
             self.MAV_CMD_BATTERY_RESET,
             self.GPSForYaw,
             self.NetworkingWebServer,
+            self.MAV_SYSID_32bit,
             self.NetworkingWebServerPPP,
             self.RTL_SPEED,
             self.ScriptingLocationBindings,

From 328f8cef05b2316866a30926d4e297b264569b6a Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 18/21] Plane: support 32 bit system IDs

Accept 32 bit sysids in MAV_CMD_DO_FOLLOW and convert the Follow
parameters at load time.
---
 ArduPlane/GCS_MAVLink_Plane.cpp | 8 +++++---
 ArduPlane/Parameters.cpp        | 5 +++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/ArduPlane/GCS_MAVLink_Plane.cpp b/ArduPlane/GCS_MAVLink_Plane.cpp
index 1edd99a9ac63d..ff70b70de1395 100644
--- a/ArduPlane/GCS_MAVLink_Plane.cpp
+++ b/ArduPlane/GCS_MAVLink_Plane.cpp
@@ -746,13 +746,15 @@ MAV_RESULT GCS_MAVLINK_Plane::handle_command_int_packet(const mavlink_command_in
 #endif
 
 #if AP_SCRIPTING_ENABLED && AP_FOLLOW_ENABLED
-    case MAV_CMD_DO_FOLLOW:
+    case MAV_CMD_DO_FOLLOW: {
         // param1: sysid of target to follow
-        if ((packet.param1 > 0) && (packet.param1 <= 255)) {
-            plane.g2.follow.set_target_sysid((uint8_t)packet.param1);
+        const int64_t sysid = (int64_t)packet.param1;
+        if (sysid > 0 && sysid <= (int64_t)0xFFFFFFFF) {
+            plane.g2.follow.set_target_sysid((uint32_t)sysid);
             return MAV_RESULT_ACCEPTED;
         }
         return MAV_RESULT_DENIED;
+    }
 #endif
 
 #if AP_ICENGINE_ENABLED
diff --git a/ArduPlane/Parameters.cpp b/ArduPlane/Parameters.cpp
index ce6671385d148..c77af68dd30b4 100644
--- a/ArduPlane/Parameters.cpp
+++ b/ArduPlane/Parameters.cpp
@@ -1478,6 +1478,11 @@ void Plane::load_parameters(void)
 
     g.use_reverse_thrust.convert_parameter_width(AP_PARAM_INT16);
 
+#if AP_SCRIPTING_ENABLED && AP_FOLLOW_ENABLED
+    // convert Follow parameters
+    g2.follow.convert_params();
+#endif
+
     // PARAMETER_CONVERSION - Added: Jun-2026 for FBWB_CLIMB_RATE width change
     g.flybywire_climb_rate.convert_parameter_width(AP_PARAM_INT8);
 

From 3cfb2e05fa0a8be02c2e29c6d50ef9e6eb022ad4 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 19/21] Copter: support 32 bit system IDs

Convert the Follow parameters at load time, before mode entry can read
FOLL_SYSID.
---
 ArduCopter/Parameters.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/ArduCopter/Parameters.cpp b/ArduCopter/Parameters.cpp
index 06b5cb487b007..c55b274519a20 100644
--- a/ArduCopter/Parameters.cpp
+++ b/ArduCopter/Parameters.cpp
@@ -1337,6 +1337,11 @@ void Copter::load_parameters(void)
     copter.avoid.convert_params();
 #endif
 
+#if MODE_FOLLOW_ENABLED
+    // convert Follow parameters
+    copter.g2.follow.convert_params();
+#endif
+
     // convert PILOT vertical speed and acceleration parameters
     // PARAMETER_CONVERSION - Added: Feb 2026 for ardupilot-4.7
     {

From e30452af5238aee12f6837d16b42fb5d1d3d217b Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 20/21] Rover: support 32 bit system IDs

---
 Rover/Parameters.cpp | 5 +++++
 Rover/mode_auto.cpp  | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Rover/Parameters.cpp b/Rover/Parameters.cpp
index 504ed2168f85b..bb9add7bf7145 100644
--- a/Rover/Parameters.cpp
+++ b/Rover/Parameters.cpp
@@ -842,6 +842,11 @@ void Rover::load_parameters(void)
     };
     AP_Param::convert_old_parameters(&ff_and_filt_conversion_info[0], ARRAY_SIZE(ff_and_filt_conversion_info));
 
+#if AP_FOLLOW_ENABLED
+    // convert Follow parameters
+    g2.follow.convert_params();
+#endif
+
     // configure safety switch to allow stopping the motors while armed
 #if HAL_HAVE_SAFETY_SWITCH
     AP_Param::set_default_by_name("BRD_SAFETYOPTION", AP_BoardConfig::BOARD_SAFETY_OPTION_BUTTON_ACTIVE_SAFETY_OFF|
diff --git a/Rover/mode_auto.cpp b/Rover/mode_auto.cpp
index db061454f6b90..e51d0de1a61f1 100644
--- a/Rover/mode_auto.cpp
+++ b/Rover/mode_auto.cpp
@@ -497,7 +497,7 @@ void ModeAuto::send_guided_position_target()
         guided_target.last_sent_ms = now_ms;
 
         // get system id and component id of offboard navigation system
-        uint8_t sysid;
+        uint32_t sysid;
         uint8_t compid;
         mavlink_channel_t chan;
         if (GCS_MAVLINK::find_by_mavtype(MAV_TYPE_ONBOARD_CONTROLLER, sysid, compid, chan)) {

From 9cd18bc9e46f6334cda0fffefc7b0222ff249dd1 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 28 Jul 2026 07:29:57 +1000
Subject: [PATCH 21/21] Tracker: support 32 bit system IDs

---
 AntennaTracker/GCS_MAVLink_Tracker.cpp | 2 +-
 AntennaTracker/GCS_Tracker.cpp         | 4 ++--
 AntennaTracker/GCS_Tracker.h           | 4 ++--
 AntennaTracker/Parameters.cpp          | 2 +-
 AntennaTracker/Parameters.h            | 2 +-
 AntennaTracker/system.cpp              | 3 +++
 6 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/AntennaTracker/GCS_MAVLink_Tracker.cpp b/AntennaTracker/GCS_MAVLink_Tracker.cpp
index 6749dc9e0c744..0613908a3e61c 100644
--- a/AntennaTracker/GCS_MAVLink_Tracker.cpp
+++ b/AntennaTracker/GCS_MAVLink_Tracker.cpp
@@ -254,7 +254,7 @@ void GCS_MAVLINK_Tracker::packetReceived(const mavlink_status_t &status,
                                          const mavlink_message_t &msg)
 {
     // return immediately if sysid doesn't match our target sysid
-    if ((tracker.g.sysid_target != 0) && (tracker.g.sysid_target != msg.sysid)) {
+    if ((tracker.g.sysid_target != 0) && (uint32_t(tracker.g.sysid_target.get()) != msg.sysid)) {
         GCS_MAVLINK::packetReceived(status, msg);
         return;
     }
diff --git a/AntennaTracker/GCS_Tracker.cpp b/AntennaTracker/GCS_Tracker.cpp
index ef5c991856d31..7305edf0fea8f 100644
--- a/AntennaTracker/GCS_Tracker.cpp
+++ b/AntennaTracker/GCS_Tracker.cpp
@@ -1,7 +1,7 @@
 #include "GCS_Tracker.h"
 #include "Tracker.h"
 
-void GCS_Tracker::request_datastream_position(const uint8_t _sysid, const uint8_t compid)
+void GCS_Tracker::request_datastream_position(const uint32_t _sysid, const uint8_t compid)
 {
     for (uint8_t i=0; i < num_gcs(); i++) {
             // request position
@@ -17,7 +17,7 @@ void GCS_Tracker::request_datastream_position(const uint8_t _sysid, const uint8_
     }
 }
 
-void GCS_Tracker::request_datastream_airpressure(const uint8_t _sysid, const uint8_t compid)
+void GCS_Tracker::request_datastream_airpressure(const uint32_t _sysid, const uint8_t compid)
 {
     for (uint8_t i=0; i < num_gcs(); i++) {
             // request air pressure
diff --git a/AntennaTracker/GCS_Tracker.h b/AntennaTracker/GCS_Tracker.h
index 5695d23782682..055a205f4ea09 100644
--- a/AntennaTracker/GCS_Tracker.h
+++ b/AntennaTracker/GCS_Tracker.h
@@ -30,7 +30,7 @@ class GCS_Tracker : public GCS
 
 private:
 
-    void request_datastream_position(uint8_t sysid, uint8_t compid);
-    void request_datastream_airpressure(uint8_t sysid, uint8_t compid);
+    void request_datastream_position(uint32_t sysid, uint8_t compid);
+    void request_datastream_airpressure(uint32_t sysid, uint8_t compid);
 
 };
diff --git a/AntennaTracker/Parameters.cpp b/AntennaTracker/Parameters.cpp
index 3a5fd8c0eb2a2..1851ea3faf421 100644
--- a/AntennaTracker/Parameters.cpp
+++ b/AntennaTracker/Parameters.cpp
@@ -19,7 +19,7 @@ const AP_Param::Info Tracker::var_info[] = {
     // @Param: SYSID_TARGET
     // @DisplayName: Target vehicle's MAVLink system ID
     // @Description: The identifier of the vehicle being tracked. This should be zero (to auto detect) or be the same as the MAV_SYSID parameter of the vehicle being tracked.
-    // @Range: 1 255
+    // @Range: 1 16777215
     // @User: Advanced
     GSCALAR(sysid_target,           "SYSID_TARGET",    0),
 
diff --git a/AntennaTracker/Parameters.h b/AntennaTracker/Parameters.h
index 033f18eac353f..4c345a80d9640 100644
--- a/AntennaTracker/Parameters.h
+++ b/AntennaTracker/Parameters.h
@@ -140,7 +140,7 @@ class Parameters {
 
     // Telemetry control
     //
-    AP_Int16 sysid_target;
+    AP_Int32 sysid_target;
 
     AP_Float yaw_slew_time;
     AP_Float pitch_slew_time;
diff --git a/AntennaTracker/system.cpp b/AntennaTracker/system.cpp
index dd7cee2fe8143..2113234c8f34b 100644
--- a/AntennaTracker/system.cpp
+++ b/AntennaTracker/system.cpp
@@ -5,6 +5,9 @@ static const StorageAccess wp_storage(StorageManager::StorageMission);
 
 void Tracker::init_ardupilot()
 {
+    // PARAMETER_CONVERSION - Added: Jul-2026 for 32 bit sysids
+    g.sysid_target.convert_parameter_width(AP_PARAM_INT16);
+
     // initialise notify
     notify.init();
     AP_Notify::flags.pre_arm_check = true;