diff --git a/firmware/platformio.ini b/firmware/platformio.ini
index f54a174..462a4f7 100644
--- a/firmware/platformio.ini
+++ b/firmware/platformio.ini
@@ -3,7 +3,7 @@ platform = espressif32
 board = esp32dev
 framework = arduino
 lib_deps =
-    wifwaf/ESPAsyncWebServer @ ^3.6.0
+    mathieucarbou/ESPAsyncWebServer @ ^3.6.0
     teemuatlut/TMCStepper @ ^0.7.3
     waspinator/AccelStepper @ ^1.64
     bblanchon/ArduinoJson @ ^7.3.0
diff --git a/firmware/src/main.cpp b/firmware/src/main.cpp
index 9a7d44b..6cf2d30 100644
--- a/firmware/src/main.cpp
+++ b/firmware/src/main.cpp
@@ -21,9 +21,10 @@
 
 static AsyncWebServer server(80);
 
-// TMC2209 drivers on shared UART bus (different addresses)
-static TMC2209Stepper tmc_theta(TMC_RX_PIN, TMC_TX_PIN, TMC_R_SENSE, THETA_TMC_ADDR);
-static TMC2209Stepper tmc_phi(TMC_RX_PIN, TMC_TX_PIN, TMC_R_SENSE, PHI_TMC_ADDR);
+// TMC2209 drivers on shared HardwareSerial bus (different addresses)
+// ESP32 requires HardwareSerial& — pin assignment happens in Serial2.begin()
+static TMC2209Stepper tmc_theta(&Serial2, TMC_R_SENSE, THETA_TMC_ADDR);
+static TMC2209Stepper tmc_phi(&Serial2, TMC_R_SENSE, PHI_TMC_ADDR);
 
 // AccelStepper instances (DRIVER mode = step + dir pins)
 static AccelStepper stepper_theta(AccelStepper::DRIVER, THETA_STEP_PIN, THETA_DIR_PIN);
@@ -144,7 +145,7 @@ static void init_tmc(TMC2209Stepper& tmc, const char* label) {
     // Verify communication
     uint8_t result = tmc.test_connection();
     if (result == 0) {
-        Serial.printf("[TMC] %s: OK (addr=%d)\n", label, tmc.slave_address);
+        Serial.printf("[TMC] %s: OK\n", label);
     } else {
         Serial.printf("[TMC] %s: FAILED (result=%d)\n", label, result);
     }
@@ -236,7 +237,7 @@ static void setup_routes() {
             return;
         }
 
-        if (!doc.containsKey("theta_deg") || !doc.containsKey("phi_deg")) {
+        if (!doc["theta_deg"].is<float>() || !doc["phi_deg"].is<float>()) {
             request->send(400, "application/json", error_json("Missing theta_deg or phi_deg"));
             return;
         }
@@ -361,17 +362,17 @@ static void setup_routes() {
             return;
         }
 
-        if (doc.containsKey("speed")) {
+        if (doc["speed"].is<float>()) {
             float speed = doc["speed"].as<float>();
             stepper_theta.setMaxSpeed(speed);
             stepper_phi.setMaxSpeed(speed);
         }
-        if (doc.containsKey("accel")) {
+        if (doc["accel"].is<float>()) {
             float accel = doc["accel"].as<float>();
             stepper_theta.setAcceleration(accel);
             stepper_phi.setAcceleration(accel);
         }
-        if (doc.containsKey("microstepping")) {
+        if (doc["microstepping"].is<unsigned>()) {
             uint16_t ms = doc["microstepping"].as<uint16_t>();
             if (ms == 1 || ms == 2 || ms == 4 || ms == 8 || ms == 16 ||
                 ms == 32 || ms == 64 || ms == 128 || ms == 256) {
@@ -466,7 +467,12 @@ void setup() {
     Serial.println("[HTTP] Server started on port 80");
 
     // Watchdog (resets if main loop hangs)
-    esp_task_wdt_init(WATCHDOG_TIMEOUT_S, true);
+    const esp_task_wdt_config_t wdt_cfg = {
+        .timeout_ms = WATCHDOG_TIMEOUT_S * 1000,
+        .idle_core_mask = 0,
+        .trigger_panic = true,
+    };
+    esp_task_wdt_init(&wdt_cfg);
     esp_task_wdt_add(NULL);
 
     last_command_ms = millis();