diff --git a/esp32s3/balance/main/CMakeLists.txt b/esp32s3/balance/main/CMakeLists.txt
index 2fd31d5..518a489 100644
--- a/esp32s3/balance/main/CMakeLists.txt
+++ b/esp32s3/balance/main/CMakeLists.txt
@@ -1,4 +1,22 @@
 idf_component_register(
-    SRCS "main.c" "orin_serial.c" "vesc_can.c"
+    SRCS
+        "main.c"
+        "orin_serial.c"
+        "vesc_can.c"
+        "gitea_ota.c"
+        "ota_self.c"
+        "uart_ota.c"
+        "ota_display.c"
     INCLUDE_DIRS "."
+    REQUIRES
+        esp_wifi
+        esp_http_client
+        esp_https_ota
+        nvs_flash
+        app_update
+        mbedtls
+        cJSON
+        driver
+        freertos
+        esp_timer
 )
diff --git a/esp32s3/balance/main/main.c b/esp32s3/balance/main/main.c
index c382c04..f8c4796 100644
--- a/esp32s3/balance/main/main.c
+++ b/esp32s3/balance/main/main.c
@@ -1,15 +1,11 @@
-/* main.c — ESP32-S3 BALANCE app_main (bd-66hx)
- *
- * Initializes Orin serial and VESC CAN TWAI, creates tasks:
- *   orin_rx   — parse incoming Orin commands
- *   orin_tx   — transmit queued serial frames
- *   vesc_rx   — receive VESC CAN telemetry, proxy to Orin
- *   telem     — periodic TELEM_STATUS to Orin @ 10 Hz
- *   drive     — apply Orin drive commands to VESCs via CAN
- */
+/* main.c — ESP32-S3 BALANCE app_main (bd-66hx + OTA beads) */
 
 #include "orin_serial.h"
 #include "vesc_can.h"
+#include "gitea_ota.h"
+#include "ota_self.h"
+#include "uart_ota.h"
+#include "ota_display.h"
 #include "config.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
@@ -86,7 +82,10 @@ static void drive_task(void *arg)
 
 void app_main(void)
 {
-    ESP_LOGI(TAG, "ESP32-S3 BALANCE bd-66hx starting");
+    ESP_LOGI(TAG, "ESP32-S3 BALANCE starting");
+
+    /* OTA rollback health check — must be called within OTA_ROLLBACK_WINDOW_S */
+    ota_self_health_check();
 
     /* Init peripherals */
     orin_serial_init();
@@ -106,6 +105,10 @@ void app_main(void)
     xTaskCreate(telem_task,          "telem",    2048, NULL,          5, NULL);
     xTaskCreate(drive_task,          "drive",    2048, NULL,          8, NULL);
 
+    /* OTA subsystem — WiFi version checker + display overlay */
+    gitea_ota_init();
+    ota_display_init();
+
     ESP_LOGI(TAG, "all tasks started");
     /* app_main returns — FreeRTOS scheduler continues */
 }
diff --git a/esp32s3/balance/main/orin_serial.c b/esp32s3/balance/main/orin_serial.c
index 2cb3ef4..52de20b 100644
--- a/esp32s3/balance/main/orin_serial.c
+++ b/esp32s3/balance/main/orin_serial.c
@@ -1,17 +1,18 @@
-/* orin_serial.c — Orin↔ESP32-S3 serial protocol implementation (bd-66hx)
- *
- * Implements the binary framing protocol matching bd-wim1 (Orin side).
- * CRC8-SMBUS: poly=0x07, init=0x00, covers LEN+TYPE+PAYLOAD bytes.
- */
+/* orin_serial.c — Orin↔ESP32-S3 serial protocol (bd-66hx + bd-1s1s OTA cmds) */
 
 #include "orin_serial.h"
 #include "config.h"
+#include "gitea_ota.h"
+#include "ota_self.h"
+#include "uart_ota.h"
+#include "version.h"
 #include "driver/uart.h"
 #include "esp_log.h"
 #include "esp_timer.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/queue.h"
 #include <string.h>
+#include <stdio.h>
 
 static const char *TAG = "orin";
 
@@ -206,6 +207,46 @@ static void dispatch_cmd(uint8_t type, const uint8_t *payload, uint8_t len,
         orin_send_ack(tx_q, type);
         break;
 
+    case CMD_OTA_CHECK:
+        /* Trigger an immediate Gitea version check */
+        gitea_ota_check_now();
+        orin_send_version_info(tx_q, OTA_TARGET_BALANCE,
+                                BALANCE_FW_VERSION,
+                                g_balance_update.available
+                                    ? g_balance_update.version : "");
+        orin_send_version_info(tx_q, OTA_TARGET_IO,
+                                IO_FW_VERSION,
+                                g_io_update.available
+                                    ? g_io_update.version : "");
+        orin_send_ack(tx_q, type);
+        break;
+
+    case CMD_OTA_UPDATE:
+        if (len < 1u) { orin_send_nack(tx_q, type, ERR_BAD_LEN); break; }
+        {
+            uint8_t target = payload[0];
+            bool triggered = false;
+            if (target == OTA_TARGET_IO || target == OTA_TARGET_BOTH) {
+                if (!uart_ota_trigger()) {
+                    orin_send_nack(tx_q, type,
+                        g_io_update.available ? ERR_OTA_BUSY : ERR_OTA_NO_UPDATE);
+                    break;
+                }
+                triggered = true;
+            }
+            if (target == OTA_TARGET_BALANCE || target == OTA_TARGET_BOTH) {
+                if (!ota_self_trigger()) {
+                    if (!triggered) {
+                        orin_send_nack(tx_q, type,
+                            g_balance_update.available ? ERR_OTA_BUSY : ERR_OTA_NO_UPDATE);
+                        break;
+                    }
+                }
+            }
+            orin_send_ack(tx_q, type);
+        }
+        break;
+
     default:
         ESP_LOGW(TAG, "unknown cmd type=0x%02x", type);
         break;
@@ -290,3 +331,24 @@ void orin_serial_tx_task(void *arg)
         }
     }
 }
+
+/* ── OTA telemetry helpers (bd-1s1s) ── */
+
+void orin_send_ota_status(QueueHandle_t q, uint8_t target,
+                           uint8_t state, uint8_t progress, uint8_t err)
+{
+    /* TELEM_OTA_STATUS: uint8 target, uint8 state, uint8 progress, uint8 err */
+    uint8_t p[4] = {target, state, progress, err};
+    enqueue(q, TELEM_OTA_STATUS, p, 4u);
+}
+
+void orin_send_version_info(QueueHandle_t q, uint8_t target,
+                             const char *current, const char *available)
+{
+    /* TELEM_VERSION_INFO: uint8 target, char current[16], char available[16] */
+    uint8_t p[33];
+    p[0] = target;
+    strncpy((char *)&p[1],  current,   16); p[16] = '\0';
+    strncpy((char *)&p[17], available ? available : "", 16); p[32] = '\0';
+    enqueue(q, TELEM_VERSION_INFO, p, 33u);
+}
diff --git a/esp32s3/balance/main/orin_serial.h b/esp32s3/balance/main/orin_serial.h
index d533794..6df1f0c 100644
--- a/esp32s3/balance/main/orin_serial.h
+++ b/esp32s3/balance/main/orin_serial.h
@@ -29,14 +29,27 @@
 #define TELEM_STATUS        0x80u   /* status @ 10 Hz */
 #define TELEM_VESC_LEFT     0x81u   /* VESC ID 56 telemetry @ 10 Hz */
 #define TELEM_VESC_RIGHT    0x82u   /* VESC ID 68 telemetry @ 10 Hz */
+#define TELEM_OTA_STATUS    0x83u   /* OTA state + progress (bd-1s1s) */
+#define TELEM_VERSION_INFO  0x84u   /* firmware version report (bd-1s1s) */
 #define RESP_ACK            0xA0u
 #define RESP_NACK           0xA1u
 
+/* ── OTA commands (Orin → ESP32, bd-1s1s) ── */
+#define CMD_OTA_CHECK       0x10u   /* no payload: trigger Gitea version check */
+#define CMD_OTA_UPDATE      0x11u   /* uint8 target: 0=balance, 1=io, 2=both */
+
+/* ── OTA target constants ── */
+#define OTA_TARGET_BALANCE  0x00u
+#define OTA_TARGET_IO       0x01u
+#define OTA_TARGET_BOTH     0x02u
+
 /* ── NACK error codes ── */
 #define ERR_BAD_CRC         0x01u
 #define ERR_BAD_LEN         0x02u
 #define ERR_ESTOP_ACTIVE    0x03u
 #define ERR_DISARMED        0x04u
+#define ERR_OTA_BUSY        0x05u
+#define ERR_OTA_NO_UPDATE   0x06u
 
 /* ── Balance state (mirrored from TELEM_STATUS.balance_state) ── */
 typedef enum {
@@ -92,3 +105,9 @@ void orin_send_vesc(QueueHandle_t q, uint8_t telem_type,
                     int16_t current_ma, uint16_t temp_c_x10);
 void orin_send_ack(QueueHandle_t q, uint8_t cmd_type);
 void orin_send_nack(QueueHandle_t q, uint8_t cmd_type, uint8_t err);
+
+/* OTA telemetry helpers (bd-1s1s) */
+void orin_send_ota_status(QueueHandle_t q, uint8_t target,
+                           uint8_t state, uint8_t progress, uint8_t err);
+void orin_send_version_info(QueueHandle_t q, uint8_t target,
+                             const char *current, const char *available);
diff --git a/esp32s3/io/main/CMakeLists.txt b/esp32s3/io/main/CMakeLists.txt
index 46381b1..57d5760 100644
--- a/esp32s3/io/main/CMakeLists.txt
+++ b/esp32s3/io/main/CMakeLists.txt
@@ -1,4 +1,10 @@
 idf_component_register(
     SRCS "main.c" "uart_ota_recv.c"
     INCLUDE_DIRS "."
+    REQUIRES
+        app_update
+        mbedtls
+        driver
+        freertos
+        esp_timer
 )