diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index 9d79b0ec23..6de93d6ecb 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -2886,7 +2886,14 @@ message SerialProxyGetUsbInfoRequest {
 
 // The USB identity of the device currently behind a port, read live from the cached
 // USB descriptors. Fields are zero/empty while no device is connected.
-message SerialProxyGetUsbInfoResponse {
+//
+// Sent in reply to SerialProxyGetUsbInfoRequest, and also unsolicited to every connected
+// client whenever a USB device is attached to or removed from a USB_SERIAL port. A client
+// therefore subscribes to this message before querying the current state, so the
+// connect-time query and later hotplug events are handled by one path. The port's
+// subscription is untouched by a hotplug: the session belongs to the client, which decides
+// whether to keep it.
+message SerialProxyUsbInfo {
   option (id) = 154;
   option (source) = SOURCE_SERVER;
   option (ifdef) = "USE_SERIAL_PROXY";
@@ -2897,7 +2904,7 @@ message SerialProxyGetUsbInfoResponse {
   uint32 vendor_id = 4;
   uint32 product_id = 5;
   uint32 bcd_device = 6;
-  uint32 interface_number = 7;    // Channel index on multi-port bridges
+  uint32 interface_number = 7;    // bInterfaceNumber a host driver binds to, as Linux reports it
   string manufacturer = 8;
   string product = 9;
   string serial_number = 10;
diff --git a/esphome/components/api/api_connection.cpp b/esphome/components/api/api_connection.cpp
index a132bb6f72..ac26a90c25 100644
--- a/esphome/components/api/api_connection.cpp
+++ b/esphome/components/api/api_connection.cpp
@@ -1647,14 +1647,14 @@ void APIConnection::on_serial_proxy_get_modem_pins_request(const SerialProxyGetM
 
 void APIConnection::on_serial_proxy_get_usb_info_request(const SerialProxyGetUsbInfoRequest &msg) {
   auto &proxies = App.get_serial_proxies();
-  SerialProxyGetUsbInfoResponse resp{};
+  SerialProxyUsbInfo resp{};
   resp.instance = msg.instance;
   if (msg.instance >= proxies.size()) {
     ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range", msg.instance);
     resp.status = enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT;
   } else {
 #ifdef USE_SERIAL_PROXY_USB_INFO
-    // The response's strings are views into this buffer, which outlives the send below
+    // The message's strings are views into this buffer, which outlives the send below
     usb_host::UsbDeviceInfo info;
     proxies[msg.instance]->get_usb_info(info, resp);
 #else
diff --git a/esphome/components/api/api_pb2.cpp b/esphome/components/api/api_pb2.cpp
index 1a0aaefd6a..13fa91cdbd 100644
--- a/esphome/components/api/api_pb2.cpp
+++ b/esphome/components/api/api_pb2.cpp
@@ -4276,7 +4276,7 @@ bool SerialProxyGetUsbInfoRequest::decode_varint(uint32_t field_id, proto_varint
   }
   return true;
 }
-uint8_t *SerialProxyGetUsbInfoResponse::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
+uint8_t *SerialProxyUsbInfo::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
   uint8_t *__restrict__ pos = buffer.get_pos();
   ProtoEncode::encode_uint32(pos PROTO_ENCODE_DEBUG_ARG, 1, this->instance);
   ProtoEncode::encode_uint32(pos PROTO_ENCODE_DEBUG_ARG, 2, static_cast<uint32_t>(this->status));
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 7fa1560a02..4a0b7db55b 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -3440,12 +3440,12 @@ class SerialProxyGetUsbInfoRequest final : public ProtoDecodableMessage {
  protected:
   bool decode_varint(uint32_t field_id, proto_varint_value_t value) override;
 };
-class SerialProxyGetUsbInfoResponse final : public ProtoMessage {
+class SerialProxyUsbInfo final : public ProtoMessage {
  public:
   static constexpr uint16_t MESSAGE_TYPE = 154;
   static constexpr uint8_t ESTIMATED_SIZE = 51;
 #ifdef HAS_PROTO_MESSAGE_DUMP
-  const LogString *message_name() const override { return LOG_STR("serial_proxy_get_usb_info_response"); }
+  const LogString *message_name() const override { return LOG_STR("serial_proxy_usb_info"); }
 #endif
   uint32_t instance{0};
   enums::SerialProxyStatus status{};
diff --git a/esphome/components/api/api_pb2_dump.cpp b/esphome/components/api/api_pb2_dump.cpp
index b264c917ac..ede3f2350f 100644
--- a/esphome/components/api/api_pb2_dump.cpp
+++ b/esphome/components/api/api_pb2_dump.cpp
@@ -2830,8 +2830,8 @@ const char *SerialProxyGetUsbInfoRequest::dump_to(DumpBuffer &out) const {
   dump_field(out, ESPHOME_PSTR("instance"), this->instance);
   return out.c_str();
 }
-const char *SerialProxyGetUsbInfoResponse::dump_to(DumpBuffer &out) const {
-  MessageDumpHelper helper(out, ESPHOME_PSTR("SerialProxyGetUsbInfoResponse"));
+const char *SerialProxyUsbInfo::dump_to(DumpBuffer &out) const {
+  MessageDumpHelper helper(out, ESPHOME_PSTR("SerialProxyUsbInfo"));
   dump_field(out, ESPHOME_PSTR("instance"), this->instance);
   dump_field(out, ESPHOME_PSTR("status"), static_cast<enums::SerialProxyStatus>(this->status));
   dump_field(out, ESPHOME_PSTR("connected"), this->connected);
diff --git a/esphome/components/api/api_server.cpp b/esphome/components/api/api_server.cpp
index 43d35363d3..01c811156f 100644
--- a/esphome/components/api/api_server.cpp
+++ b/esphome/components/api/api_server.cpp
@@ -404,6 +404,18 @@ void APIServer::on_zwave_proxy_request(const ZWaveProxyRequest &msg) {
 }
 #endif
 
+#ifdef USE_SERIAL_PROXY_USB_INFO
+void APIServer::send_serial_proxy_usb_info(const SerialProxyUsbInfo &msg) {
+  // Unsolicited: a hotplug is rare and the message small, so every client hears of it
+  // rather than maintaining a subscription for the one client there normally is
+  for (auto &c : this->active_clients()) {
+    if (!c->send_message(msg)) {
+      API_LOG_MSG_DROPPED(TAG, "USB info notification");
+    }
+  }
+}
+#endif
+
 #if defined(USE_IR_RF) || defined(USE_RADIO_FREQUENCY)
 void APIServer::send_infrared_rf_receive_event([[maybe_unused]] uint32_t device_id, uint32_t key,
                                                const std::vector<int32_t> *timings) {
diff --git a/esphome/components/api/api_server.h b/esphome/components/api/api_server.h
index 072a583901..a58506b4c8 100644
--- a/esphome/components/api/api_server.h
+++ b/esphome/components/api/api_server.h
@@ -189,6 +189,10 @@ class APIServer final : public Component,
 #ifdef USE_ZWAVE_PROXY
   void on_zwave_proxy_request(const ZWaveProxyRequest &msg);
 #endif
+#ifdef USE_SERIAL_PROXY_USB_INFO
+  /// Tell every client that the USB device behind a serial proxy port changed
+  void send_serial_proxy_usb_info(const SerialProxyUsbInfo &msg);
+#endif
 #if defined(USE_IR_RF) || defined(USE_RADIO_FREQUENCY)
   void send_infrared_rf_receive_event(uint32_t device_id, uint32_t key, const std::vector<int32_t> *timings);
 #endif
diff --git a/esphome/components/serial_proxy/serial_proxy.cpp b/esphome/components/serial_proxy/serial_proxy.cpp
index 6a9208c01b..61263287c4 100644
--- a/esphome/components/serial_proxy/serial_proxy.cpp
+++ b/esphome/components/serial_proxy/serial_proxy.cpp
@@ -34,6 +34,13 @@ void SerialProxy::setup() {
   // instance_index_ is fixed at registration time; pre-set it so loop() only needs to update data
   this->outgoing_msg_.instance = this->instance_index_;
 #endif
+#ifdef USE_SERIAL_PROXY_USB_INFO
+  // The define is global, so a hardware UART port in the same config also gets here
+  if (this->usb_channel_ != nullptr) {
+    this->usb_channel_->get_parent()->add_on_connection_callback(
+        [this](bool connected) { this->on_usb_connection_changed_(connected); });
+  }
+#endif
 #ifdef USE_SERIAL_PROXY_TAP
   // A tap sets itself up before this runs (its setup priority is higher), so it may
   // already be waiting on the port -- a boot-time handshake with the device, say. Leaving
@@ -338,26 +345,54 @@ SerialProxyResult SerialProxy::set_modem_pins(api::APIConnection *api_connection
   return SerialProxyResult::SERIAL_PROXY_RESULT_OK;
 }
 
-#if defined(USE_SERIAL_PROXY_USB_INFO) && defined(USE_API)
-void SerialProxy::get_usb_info(usb_host::UsbDeviceInfo &info, api::SerialProxyGetUsbInfoResponse &resp) const {
+#ifdef USE_SERIAL_PROXY_USB_INFO
+void SerialProxy::on_usb_connection_changed_(bool connected) {
+  ESP_LOGD(TAG, "USB device %s serial proxy [%" PRIu32 "]",
+           connected ? LOG_STR_LITERAL("attached to") : LOG_STR_LITERAL("removed from"), this->instance_index_);
+#ifdef USE_SERIAL_PROXY_TAP
+  // Before telling clients, so a tap never acknowledges a frame from the old device after
+  // a client has been told it is gone. The subscriber and the mode stay: both belong to
+  // the client's session, and only the client knows whether that session is over.
+  if (!connected && this->tap_ != nullptr) {
+    this->tap_->on_device_disconnected();
+  }
+#endif
+#ifdef USE_API
+  if (api::global_api_server == nullptr) {
+    return;
+  }
+  // The message's strings are views into this buffer, which outlives the send below
+  usb_host::UsbDeviceInfo info;
+  api::SerialProxyUsbInfo msg{};
+  msg.instance = this->instance_index_;
+  this->get_usb_info(info, msg);
+  api::global_api_server->send_serial_proxy_usb_info(msg);
+#endif
+}
+
+#ifdef USE_API
+void SerialProxy::get_usb_info(usb_host::UsbDeviceInfo &info, api::SerialProxyUsbInfo &msg) const {
   if (this->usb_channel_ == nullptr) {
-    resp.status = api::enums::SERIAL_PROXY_STATUS_NOT_SUPPORTED;
+    msg.status = api::enums::SERIAL_PROXY_STATUS_NOT_SUPPORTED;
     return;
   }
-  resp.interface_number = this->usb_channel_->get_index();
   if (!this->usb_channel_->get_parent()->get_device_info(info)) {
     // No device attached right now; not an error
     return;
   }
-  resp.connected = true;
-  resp.vendor_id = info.vendor_id;
-  resp.product_id = info.product_id;
-  resp.bcd_device = info.bcd_device;
-  resp.manufacturer = StringRef(info.manufacturer);
-  resp.product = StringRef(info.product);
-  resp.serial_number = StringRef(info.serial_number);
+  msg.connected = true;
+  msg.vendor_id = info.vendor_id;
+  msg.product_id = info.product_id;
+  msg.bcd_device = info.bcd_device;
+  msg.interface_number = this->usb_channel_->get_interface_number();
+  msg.manufacturer = StringRef(info.manufacturer);
+  msg.product = StringRef(info.product);
+  msg.serial_number = StringRef(info.serial_number);
+  // Lives in the channel for as long as the device is attached
+  msg.interface_description = StringRef(this->usb_channel_->get_interface_string());
 }
 #endif
+#endif
 
 uint32_t SerialProxy::get_modem_pins() const {
   return (this->rts_state_ ? static_cast<uint32_t>(SERIAL_PROXY_LINE_STATE_FLAG_RTS) : 0u) |
diff --git a/esphome/components/serial_proxy/serial_proxy.h b/esphome/components/serial_proxy/serial_proxy.h
index 07c7b643cb..8ebb9ea94f 100644
--- a/esphome/components/serial_proxy/serial_proxy.h
+++ b/esphome/components/serial_proxy/serial_proxy.h
@@ -89,6 +89,11 @@ class SerialProxyTap {
   /// else with the device -- reflash it, most likely -- so anything the tap believes about
   /// it should be treated as suspect.
   virtual void on_protocol_disabled() = 0;
+
+  /// The device behind the port went away -- unplugged, or its power was cut. Whatever
+  /// session the tap had observed ended with it; the device that appears next starts from
+  /// scratch and may not even be the same one. Only a USB UART can report this.
+  virtual void on_device_disconnected() = 0;
 };
 #endif
 
@@ -169,9 +174,9 @@ class SerialProxy final : public uart::UARTDevice, public Component {
   void set_usb_channel(usb_uart::USBUartChannel *channel) { this->usb_channel_ = channel; }
 
 #ifdef USE_API
-  /// Fill a USB info response for this port. The response's strings are views into
-  /// info, so info must outlive the send.
-  void get_usb_info(usb_host::UsbDeviceInfo &info, api::SerialProxyGetUsbInfoResponse &resp) const;
+  /// Fill a USB info message for this port. The message's strings are views into info,
+  /// so info must outlive the send.
+  void get_usb_info(usb_host::UsbDeviceInfo &info, api::SerialProxyUsbInfo &msg) const;
 #endif
 #endif
 
@@ -238,6 +243,12 @@ class SerialProxy final : public uart::UARTDevice, public Component {
   bool tap_observing_() const;
 #endif
 
+#ifdef USE_SERIAL_PROXY_USB_INFO
+  /// The USB device behind this port was attached or removed. Reports the port's new USB
+  /// identity to every API client, and ends the tap's view of the old device.
+  void on_usb_connection_changed_(bool connected);
+#endif
+
   /// Instance index for identifying this proxy in API messages
   uint32_t instance_index_{0};
 
diff --git a/esphome/components/usb_host/usb_host.h b/esphome/components/usb_host/usb_host.h
index 088b222c0e..4d1e188928 100644
--- a/esphome/components/usb_host/usb_host.h
+++ b/esphome/components/usb_host/usb_host.h
@@ -167,6 +167,15 @@ class USBClient : public Component {
   void set_manufacturer_filter(const char *manufacturer) { this->manufacturer_filter_ = manufacturer; }
   void set_product_filter(const char *product) { this->product_filter_ = product; }
 
+  /// Register a callback for the device this client claims being connected (true) or
+  /// removed (false). Fires only for a device that passed every filter and was fully
+  /// opened, so a device another client claims is never reported. Called from the main
+  /// loop: connected once the device is ready to use (a subclass may hold this back until
+  /// its own setup of the device has finished), removed after on_disconnected() has run.
+  template<typename F> void add_on_connection_callback(F &&callback) {
+    this->connection_callback_.add(std::forward<F>(callback));
+  }
+
   // Lock-free event queue and pool for USB task to main loop communication
   // Must be public for access from static callbacks
   LockFreeQueue<UsbEvent, USB_EVENT_QUEUE_SIZE> event_queue;
@@ -187,6 +196,13 @@ class USBClient : public Component {
 
   /// Whether the device's descriptor strings satisfy every filter that is set.
   bool descriptor_strings_match_(const usb_device_info_t &dev_info) const;
+
+  /// Whether the subclass reports the device as connected itself, once its own setup of
+  /// the device has finished, rather than as soon as the device has been opened
+  virtual bool reports_connection_itself() const { return false; }
+  /// Report the claimed device to the connection callbacks. Idempotent; a subclass that
+  /// reports itself calls this once the device is ready to use.
+  void report_connected_();
   virtual void on_disconnected() {
     // Reset all requests to available (all bits to 0)
     this->trq_in_use_.store(0);
@@ -207,11 +223,15 @@ class USBClient : public Component {
   // Bit i = 1: requests_[i] is in use, Bit i = 0: requests_[i] is available
   // Supports multiple concurrent consumers and producers (both threads can allocate/deallocate)
   std::atomic<trq_bitmask_t> trq_in_use_;
+  LazyCallbackManager<void(bool)> connection_callback_;
   // Descriptor strings a device must report to be claimed; nullptr means no constraint
   const char *manufacturer_filter_{nullptr};
   const char *product_filter_{nullptr};
   uint16_t vid_{};
   uint16_t pid_{};
+  // Whether the connection callbacks were told about the current device, so a removal is
+  // only ever reported for a device that was reported connected
+  bool connection_reported_{false};
 };
 class USBHost final : public Component {
  public:
diff --git a/esphome/components/usb_host/usb_host_client.cpp b/esphome/components/usb_host/usb_host_client.cpp
index 58914ced6e..04b2b864e9 100644
--- a/esphome/components/usb_host/usb_host_client.cpp
+++ b/esphome/components/usb_host/usb_host_client.cpp
@@ -397,6 +397,18 @@ void USBClient::handle_open_state_() {
     usb_client_print_config_descriptor(config_desc, nullptr);
 #endif
   this->on_connected();
+  // on_connected() may have rejected the device (no usable interface, say) and closed it
+  if (this->state_ == USB_CLIENT_CONNECTED && !this->reports_connection_itself()) {
+    this->report_connected_();
+  }
+}
+
+void USBClient::report_connected_() {
+  if (this->state_ != USB_CLIENT_CONNECTED || this->connection_reported_) {
+    return;
+  }
+  this->connection_reported_ = true;
+  this->connection_callback_.call(true);
 }
 
 void USBClient::on_opened(uint8_t addr) {
@@ -467,6 +479,10 @@ TransferRequest *USBClient::get_trq_() {
 }
 
 void USBClient::disconnect() {
+  // Also reached for a device this client opened and then declined, or lost before it was
+  // ready; neither was reported as connected, so neither is reported as removed
+  const bool was_reported = this->connection_reported_;
+  this->connection_reported_ = false;
   this->on_disconnected();
   auto err = usb_host_device_close(this->handle_, this->device_handle_);
   if (err != ESP_OK) {
@@ -475,6 +491,9 @@ void USBClient::disconnect() {
   this->state_ = USB_CLIENT_INIT;
   this->device_handle_ = nullptr;
   this->device_addr_ = -1;
+  if (was_reported) {
+    this->connection_callback_.call(false);
+  }
 }
 
 // THREAD CONTEXT: Called from main loop thread only
diff --git a/esphome/components/usb_uart/usb_uart.h b/esphome/components/usb_uart/usb_uart.h
index 357e41c639..139315841e 100644
--- a/esphome/components/usb_uart/usb_uart.h
+++ b/esphome/components/usb_uart/usb_uart.h
@@ -164,9 +164,16 @@ class USBUartChannelBase : public uart::UARTComponent, public Parented<USBUartCo
   /// they arrive, eliminating one full main-loop-wakeup cycle of latency.
   void set_rx_callback(std::function<void()> cb) { this->rx_callback_ = std::move(cb); }
 
-  /// Channel index on the bridge (interface number on multi-port bridges)
+  /// Channel index on the bridge
   uint8_t get_index() const { return this->index_; }
 
+  /// USB interface number a host driver binds to for this channel: the communication
+  /// interface of a CDC ACM function, otherwise the data interface.
+  uint8_t get_interface_number() const {
+    return this->cdc_dev_.interrupt_interface_number != 0xFF ? this->cdc_dev_.interrupt_interface_number
+                                                             : this->cdc_dev_.bulk_interface_number;
+  }
+
  protected:
   // Not directly instantiable; construct a concrete channel type instead.
   USBUartChannelBase(uint8_t index, uint16_t buffer_size) : input_buffer_(RingBuffer(buffer_size)), index_(index) {}
@@ -252,6 +259,10 @@ class USBUartComponent : public usb_host::USBClient {
   // (e.g. CH34x chip detection). Same contract as config_step_(). Default: no steps.
   virtual bool config_device_step(uint8_t step, bool ok, const uint8_t *response) { return false; }
 
+  // The device is only usable once the config machine has applied every channel's line
+  // settings, so the connected report waits for run_config_machine_() to finish the init
+  bool reports_connection_itself() const override { return true; }
+
   std::vector<USBUartChannelBase *> channels_{};
 
   // Config state machine
diff --git a/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.cpp b/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.cpp
index ae82410e62..8edff1bfc2 100644
--- a/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.cpp
+++ b/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.cpp
@@ -56,6 +56,16 @@ void ZigbeeProxyTap::on_protocol_disabled() {
   this->detector_.reset();
 }
 
+void ZigbeeProxyTap::on_device_disconnected() {
+  // The ASH session died with the NCP's power. Staying armed would acknowledge frames from
+  // whatever boots next, before its own RSTACK has proven it speaks ASH at all.
+  if (this->was_armed_) {
+    ESP_LOGD(TAG, "Device removed, no longer acknowledging frames");
+    this->was_armed_ = false;
+  }
+  this->detector_.reset();
+}
+
 }  // namespace esphome::zigbee_proxy_tap
 
 #endif  // USE_ZIGBEE_PROXY_TAP
diff --git a/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.h b/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.h
index 702ae12eb7..1cae8cd1df 100644
--- a/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.h
+++ b/esphome/components/zigbee_proxy_tap/zigbee_proxy_tap.h
@@ -31,6 +31,7 @@ class ZigbeeProxyTap : public serial_proxy::SerialProxyTap, public Component {
   // there is nothing to do and the port need not be read.
   bool tap_needs_port() const override { return false; }
   void on_protocol_disabled() override;
+  void on_device_disconnected() override;
 
  protected:
   // The port this component observes. Owns the UART and the bytes; every write we make
diff --git a/esphome/components/zwave_proxy_tap/zwave_proxy_tap.cpp b/esphome/components/zwave_proxy_tap/zwave_proxy_tap.cpp
index d4b35c3d24..29797e44fc 100644
--- a/esphome/components/zwave_proxy_tap/zwave_proxy_tap.cpp
+++ b/esphome/components/zwave_proxy_tap/zwave_proxy_tap.cpp
@@ -57,6 +57,16 @@ void ZWaveProxyTap::on_protocol_disabled() {
   this->detector_.reset();
 }
 
+void ZWaveProxyTap::on_device_disconnected() {
+  // The controller lost power, so the exchange we saw belongs to a session that no longer
+  // exists. Whatever appears next has to prove itself again.
+  if (this->was_armed_) {
+    ESP_LOGD(TAG, "Device removed, no longer acknowledging frames");
+    this->was_armed_ = false;
+  }
+  this->detector_.reset();
+}
+
 }  // namespace esphome::zwave_proxy_tap
 
 #endif  // USE_ZWAVE_PROXY_TAP
diff --git a/esphome/components/zwave_proxy_tap/zwave_proxy_tap.h b/esphome/components/zwave_proxy_tap/zwave_proxy_tap.h
index 16066b30a1..ff95b411db 100644
--- a/esphome/components/zwave_proxy_tap/zwave_proxy_tap.h
+++ b/esphome/components/zwave_proxy_tap/zwave_proxy_tap.h
@@ -34,6 +34,7 @@ class ZWaveProxyTap : public serial_proxy::SerialProxyTap, public Component {
   // there is nothing to do and the port need not be read.
   bool tap_needs_port() const override { return false; }
   void on_protocol_disabled() override;
+  void on_device_disconnected() override;
 
  protected:
   // The port this component observes. Owns the UART and the bytes; every write we make