Apply the dial delay the same way at boot and after a disconnect, tell socket create and setblocking failures apart, and cap the delay so the wait always elapses

esphome/components/api/__init__.py

@@ -5,7 +5,7 @@ from typing import Any
 from esphome import automation
 from esphome.automation import Condition
 import esphome.codegen as cg
-from esphome.components.const import CONF_DESCRIPTION
+from esphome.components.const import CONF_DESCRIPTION, CONF_HOST
 from esphome.components.logger import request_log_listener
 
 # ENCRYPTION_SCHEMA and validate_encryption_key are re-exported for external
@@ -24,6 +24,8 @@ from esphome.const import (
     CONF_CAPTURE_RESPONSE,
     CONF_DATA,
     CONF_DATA_TEMPLATE,
+    CONF_DELAY,
+    CONF_ENABLE_IPV6,
     CONF_ENCRYPTION,
     CONF_EVENT,
     CONF_ID,
@@ -47,6 +49,7 @@ from esphome.const import (
 )
 from esphome.core import CORE, ID, CoroPriority, EsphomeError, coroutine_with_priority
 from esphome.cpp_generator import MockObj, TemplateArgsType
+import esphome.final_validate as fv
 from esphome.helpers import fnv1_hash
 from esphome.types import ConfigFragmentType, ConfigType
 
@@ -133,6 +136,7 @@ CONF_HOMEASSISTANT_SERVICES = "homeassistant_services"
 CONF_HOMEASSISTANT_STATES = "homeassistant_states"
 CONF_LISTEN_BACKLOG = "listen_backlog"
 CONF_MAX_SEND_QUEUE = "max_send_queue"
+CONF_OUTGOING_CONNECTION = "outgoing_connection"
 CONF_STATE_SUBSCRIPTION_ONLY = "state_subscription_only"
 
 
@@ -284,9 +288,53 @@ def _consume_api_sockets(config: ConfigType) -> ConfigType:
     # (not max_connections, which is the upper limit rarely reached)
     socket.consume_sockets(3, "api")(config)
     socket.consume_sockets(1, "api", socket.SocketType.TCP_LISTEN)(config)
+    if CONF_OUTGOING_CONNECTION in config:
+        socket.consume_sockets(1, "api_outgoing_connection")(config)
     return config
 
 
+def _validate_outgoing_connection(config: ConfigType) -> ConfigType:
+    if CONF_OUTGOING_CONNECTION not in config:
+        return config
+    # Platform default check here for a friendly early error; an explicit
+    # lwip_tcp selection on other platforms is caught against the resolved
+    # implementation in _validate_outgoing_socket_implementation
+    if CORE.is_esp8266 or CORE.is_rp2:
+        raise cv.Invalid(
+            "outgoing_connection is not supported on this platform because its "
+            "socket layer cannot make outgoing connections",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    if CONF_ENCRYPTION not in config:
+        raise cv.Invalid(
+            "outgoing_connection requires 'encryption' so the peer is verified by key",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    return config
+
+
+_OUTGOING_CONNECTION_SCHEMA = cv.Schema(
+    {
+        cv.Optional(CONF_HOST): cv.ipaddress,
+        cv.Optional(CONF_PORT, default=6054): cv.port,
+        # Bounded to half the device's uint32 millisecond range so the wait
+        # always elapses under a wrapping clock
+        cv.Optional(CONF_DELAY, default="60s"): cv.All(
+            cv.positive_time_period_milliseconds,
+            cv.Range(max=cv.TimePeriod(milliseconds=2147483647)),
+        ),
+    }
+)
+
+
+def _outgoing_connection_schema(config: ConfigType | None) -> ConfigType:
+    # A bare `outgoing_connection:` block is valid; without a host the device
+    # dials the remembered last dial-back client
+    if config is None:
+        config = {}
+    return _OUTGOING_CONNECTION_SCHEMA(config)
+
+
 CONFIG_SCHEMA = cv.All(
     cv.Schema(
         {
@@ -311,6 +359,7 @@ CONFIG_SCHEMA = cv.All(
             ): ACTIONS_SCHEMA,
             cv.Exclusive(CONF_ACTIONS, group_of_exclusion=CONF_ACTIONS): ACTIONS_SCHEMA,
             cv.Optional(CONF_ENCRYPTION): encryption_schema,
+            cv.Optional(CONF_OUTGOING_CONNECTION): _outgoing_connection_schema,
             cv.Optional(CONF_BATCH_DELAY, default="100ms"): cv.All(
                 cv.positive_time_period_milliseconds,
                 cv.Range(max=cv.TimePeriod(milliseconds=65535)),
@@ -367,6 +416,7 @@ CONFIG_SCHEMA = cv.All(
         }
     ).extend(cv.COMPONENT_SCHEMA),
     cv.rename_key(CONF_SERVICES, CONF_ACTIONS),
+    _validate_outgoing_connection,
     _consume_api_sockets,
     _register_provisioning_source,
 )
@@ -423,7 +473,47 @@ def _validate_esp8266_action_strings(config: ConfigType) -> ConfigType:
     return config
 
 
-FINAL_VALIDATE_SCHEMA = _validate_esp8266_action_strings
+def _validate_outgoing_socket_implementation(config: ConfigType) -> ConfigType:
+    """A raw lwip_tcp socket can be selected explicitly on any platform."""
+    if CONF_OUTGOING_CONNECTION not in config:
+        return config
+    from esphome.components import socket
+
+    socket_conf = fv.full_config.get().get("socket") or {}
+    if (
+        impl := socket_conf.get(socket.CONF_IMPLEMENTATION)
+    ) in socket.IMPLEMENTATIONS_WITHOUT_CONNECT:
+        raise cv.Invalid(
+            f"outgoing_connection is not supported with the {impl} socket "
+            "implementation because it cannot make outgoing connections",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    return config
+
+
+def _validate_outgoing_host_ipv6(config: ConfigType) -> ConfigType:
+    """An IPv6 host can never be parsed, so never dialed, without IPv6."""
+    if (
+        (outgoing := config.get(CONF_OUTGOING_CONNECTION)) is None
+        or (host := outgoing.get(CONF_HOST)) is None
+        or host.version != 6
+    ):
+        return config
+    network_conf = fv.full_config.get().get("network") or {}
+    if not network_conf.get(CONF_ENABLE_IPV6):
+        raise cv.Invalid(
+            "outgoing_connection host is an IPv6 address but IPv6 is not "
+            "enabled; set 'network: enable_ipv6: true'",
+            path=[CONF_OUTGOING_CONNECTION, CONF_HOST],
+        )
+    return config
+
+
+FINAL_VALIDATE_SCHEMA = cv.All(
+    _validate_esp8266_action_strings,
+    _validate_outgoing_socket_implementation,
+    _validate_outgoing_host_ipv6,
+)
 
 
 def _add_action_strings(
@@ -606,6 +696,13 @@ async def to_code(config: ConfigType) -> None:
     else:
         cg.add_define("USE_API_PLAINTEXT")
 
+    if (outgoing := config.get(CONF_OUTGOING_CONNECTION)) is not None:
+        cg.add_define("USE_API_OUTGOING_CONNECTION")
+        if (host := outgoing.get(CONF_HOST)) is not None:
+            cg.add_define("API_OUTGOING_CONNECTION_HOST", str(host))
+        cg.add_define("API_OUTGOING_CONNECTION_PORT", outgoing[CONF_PORT])
+        cg.add_define("API_OUTGOING_CONNECTION_DELAY", outgoing[CONF_DELAY])
+
     cg.add_define("USE_API")
     cg.add_global(api_ns.using)
 
@@ -992,6 +1089,7 @@ _define_filter = filter_source_files_from_defines(
         "user_services.cpp": "USE_API_USER_DEFINED_ACTIONS",
         "api_frame_helper_noise.cpp": "USE_API_NOISE",
         "api_frame_helper_plaintext.cpp": "USE_API_PLAINTEXT",
+        "api_outgoing_connection.cpp": "USE_API_OUTGOING_CONNECTION",
     }
 )
 

esphome/components/api/api.proto

@@ -112,6 +112,11 @@ message HelloRequest {
   string client_info = 1;
   uint32 api_version_major = 2;
   uint32 api_version_minor = 3;
+
+  // Set by clients that can accept connections the device opens to them
+  // (see api: outgoing_connection:). The device remembers this client's
+  // address as the target to dial when no such client is connected.
+  bool outgoing_connection_target = 4 [(field_ifdef) = "USE_API_OUTGOING_CONNECTION"];
 }
 
 // Confirmation of successful connection request.
@@ -331,6 +336,10 @@ message DeviceInfoResponse {
   // all-zeros PSK, so the api encryption key can be provisioned without being
   // sent in plaintext (protects against passive sniffing, not active MITM)
   bool api_encryption_provisionable = 26 [(field_ifdef) = "USE_API_NOISE"];
+
+  // Device is built with the api outgoing_connection option and can open
+  // the TCP connection to a dial-back target itself
+  bool api_outgoing_connection_supported = 27 [(field_ifdef) = "USE_API_OUTGOING_CONNECTION"];
 }
 
 // ==================== DEVICE CAPABILITIES ====================

esphome/components/api/api_connection.cpp

@@ -1822,6 +1822,19 @@ bool APIConnection::send_hello_response_(const HelloRequest &msg) {
   // Auto-authenticate - password auth was removed in ESPHome 2026.1.0
   this->complete_authentication_();
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  // With a PSK set only key-verified transports reach hello: plaintext and
+  // zero-PSK are rejected, and pre-activation sessions are force-closed
+  if (msg.outgoing_connection_target && !this->flags_.outgoing_connection_target) {
+    if (this->parent_->get_noise_ctx().has_psk()) {
+      this->flags_.outgoing_connection_target = true;
+      this->parent_->on_outgoing_target_client(this);
+    } else {
+      this->log_client_(ESPHOME_LOG_LEVEL_WARN, LOG_STR("Dial-back target refused; no key active"));
+    }
+  }
+#endif
+
   return this->send_message(resp);
 }
 
@@ -1944,6 +1957,9 @@ bool APIConnection::send_device_info_response_() {
   // one) so this advertisement survives the plaintext removal in 2027.2.0.
   resp.api_encryption_provisionable = !this->parent_->get_noise_ctx().has_psk();
 #endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  resp.api_outgoing_connection_supported = true;
+#endif
 #endif
 #ifdef USE_DEVICES
   size_t device_index = 0;

esphome/components/api/api_connection.h

@@ -375,6 +375,21 @@ class APIConnection final : public APIServerConnectionBase {
     return this->helper_->get_peername_to(buf);
   }
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  /// Outgoing connection: send our server hello immediately so the peer can
+  /// pick the matching key. Outgoing connections are only dialed when a PSK
+  /// is set, so the helper is always the noise helper. Call after start().
+  void mark_outgoing() {
+    if (this->flags_.remove) {
+      return;  // start() failed; the connection is already being torn down
+    }
+    APIError err = static_cast<APINoiseFrameHelper *>(this->helper_.get())->send_server_hello_first();
+    if (err != APIError::OK) {
+      this->fatal_error_with_log_(LOG_STR("Server hello failed"), err);
+    }
+  }
+#endif
+
  protected:
   bool try_to_clear_buffer_slow_(bool log_out_of_space);
 
@@ -745,6 +760,9 @@ class APIConnection final : public APIServerConnectionBase {
     uint8_t batch_first_message : 1;          // For batch buffer allocation
     uint8_t should_try_send_immediately : 1;  // True after initial states are sent
     uint8_t may_have_remaining_data : 1;      // Read loop hit limit, retry without ready check
+#ifdef USE_API_OUTGOING_CONNECTION
+    uint8_t outgoing_connection_target : 1;  // Client declared itself a dial-back target in its hello
+#endif
 #ifdef HAS_PROTO_MESSAGE_DUMP
     uint8_t log_only_mode : 1;
 #endif

esphome/components/api/api_frame_helper.h

@@ -18,7 +18,7 @@
 namespace esphome::api {
 
 // uncomment to log raw packets
-//#define HELPER_LOG_PACKETS
+// #define HELPER_LOG_PACKETS
 
 // Maximum message size limits to prevent OOM on constrained devices
 // Handshake messages are limited to a small size for security
@@ -282,7 +282,8 @@ class APIFrameHelper {
     DATA = 5,
     CLOSED = 6,
     FAILED = 7,
-    EXPLICIT_REJECT = 8,  // Noise only
+    EXPLICIT_REJECT = 8,        // Noise only
+    CLIENT_HELLO_OUTGOING = 9,  // Noise only: like CLIENT_HELLO but the server hello already went out (outgoing conn)
   };
 
   // Fast inline state check for read_packet/write_protobuf_messages hot path.

esphome/components/api/api_frame_helper_noise.cpp

@@ -81,6 +81,13 @@ APIError APINoiseFrameHelper::init() {
   state_ = State::CLIENT_HELLO;
   return APIError::OK;
 }
+#ifdef USE_API_OUTGOING_CONNECTION
+APIError APINoiseFrameHelper::send_server_hello_first() {
+  // The peer needs our name and MAC to pick the key before its first message
+  this->state_ = State::CLIENT_HELLO_OUTGOING;
+  return this->send_server_hello_frame_();
+}
+#endif
 #ifdef USE_API_PLAINTEXT
 APIError APINoiseFrameHelper::init_from_handoff(const uint8_t *header, uint8_t header_len) {
   APIError err = this->init();
@@ -253,6 +260,9 @@ APIError APINoiseFrameHelper::state_action_() {
       HELPER_LOG("Bad state for method: %d", (int) this->state_);
       return APIError::BAD_STATE;
     case State::CLIENT_HELLO:
+#ifdef USE_API_OUTGOING_CONNECTION
+    case State::CLIENT_HELLO_OUTGOING:
+#endif
       return this->state_action_client_hello_();
     case State::SERVER_HELLO:
       return this->state_action_server_hello_();
@@ -285,11 +295,16 @@ APIError APINoiseFrameHelper::state_action_client_hello_() {
     std::memcpy(this->prologue_.data() + old_size + 2, this->rx_buf_.data(), rx_size);
   }
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  if (this->state_ == State::CLIENT_HELLO_OUTGOING) {
+    // Server hello already went out at handoff
+    return this->start_handshake_();
+  }
+#endif
   state_ = State::SERVER_HELLO;
   return APIError::OK;
 }
-APIError APINoiseFrameHelper::state_action_server_hello_() {
-  // send server hello
+APIError APINoiseFrameHelper::send_server_hello_frame_() {
   const auto &name = App.get_name();
   char mac[MAC_ADDRESS_BUFFER_SIZE];
   get_mac_address_into_buffer(mac);
@@ -313,15 +328,18 @@ APIError APINoiseFrameHelper::state_action_server_hello_() {
   // node mac, terminated by null byte
   std::memcpy(msg + mac_offset, mac, MAC_ADDRESS_BUFFER_SIZE);
 
-  APIError aerr = write_frame_(msg, total_size);
+  return write_frame_(msg, total_size);
+}
+APIError APINoiseFrameHelper::state_action_server_hello_() {
+  APIError aerr = this->send_server_hello_frame_();
   if (aerr != APIError::OK)
     return aerr;
-
-  // start handshake
-  aerr = init_handshake_();
+  return this->start_handshake_();
+}
+APIError APINoiseFrameHelper::start_handshake_() {
+  APIError aerr = init_handshake_();
   if (aerr != APIError::OK)
     return aerr;
-
   state_ = State::HANDSHAKE;
   return APIError::OK;
 }

esphome/components/api/api_frame_helper_noise.h

@@ -28,6 +28,12 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   // Seeds the already-read header bytes and pumps the handshake state machine
   // until it would block.
   APIError init_from_handoff(const uint8_t *header, uint8_t header_len);
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Send the server hello immediately so the peer can pick the key before
+  // its PSK-mixed message. Call after init(); the mode is tracked in state_
+  // so the helper does not grow.
+  APIError send_server_hello_first();
 #endif
   APIError loop() override;
   APIError read_packet(ReadPacketBuffer *buffer) override;
@@ -39,6 +45,8 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   APIError state_action_();
   APIError state_action_client_hello_();
   APIError state_action_server_hello_();
+  APIError send_server_hello_frame_();
+  APIError start_handshake_();
   APIError state_action_handshake_();
   APIError state_action_handshake_read_();
   APIError state_action_handshake_write_();

esphome/components/api/api_outgoing_connection.cpp

@@ -0,0 +1,236 @@
+#include "api_outgoing_connection.h"
+#if defined(USE_API) && defined(USE_API_OUTGOING_CONNECTION)
+
+#include "api_connection.h"
+#include "api_server.h"
+#include "esphome/components/network/util.h"
+#include "esphome/core/application.h"
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
+
+#include <cerrno>
+#include <cstring>
+
+namespace esphome::api {
+
+static const char *const TAG = "api.outgoing";
+
+void OutgoingConnectionManager::setup() {
+#ifndef API_OUTGOING_CONNECTION_HOST
+  this->target_pref_ = global_preferences->make_preference<SavedOutgoingTarget>(629847102UL, true);
+  if (this->target_pref_.load(&this->saved_)) {
+    this->host_persisted_ = true;
+    ESP_LOGD(TAG, "Loaded target %s", this->saved_.host);
+  } else {
+    // Never saved, or the blob failed its size/CRC check
+    ESP_LOGD(TAG, "No saved target");
+    this->saved_ = {};
+  }
+  // Defend against a corrupt or truncated preference blob
+  this->saved_.host[sizeof(this->saved_.host) - 1] = '\0';
+#endif
+}
+
+void OutgoingConnectionManager::loop(APIServer *server) {
+  if (server->has_outgoing_target_client_()) {
+    return;  // on_target_client() already reset the dial state
+  }
+  if (this->dialed_conn_ != nullptr) {
+    // A live dialed session (flagged or not, e.g. a host: peer) is the
+    // target; a silent one dies on the handshake timeout
+    return;
+  }
+  const uint32_t now = App.get_loop_component_start_time();
+  switch (this->state_) {
+    case DialState::DIAL_STATE_IDLE:
+#ifdef USE_DEEP_SLEEP
+      // A deep sleep wake window is too short to spend on the delay
+      this->schedule_wait_(now, BACKOFF_MIN_MS);
+#else
+      // Target went away; give it the configured delay to reconnect first
+      this->schedule_wait_(now, API_OUTGOING_CONNECTION_DELAY);
+#endif
+      break;
+    case DialState::DIAL_STATE_WAITING:
+      if (now - this->state_ts_ >= this->wait_) {
+        this->try_dial_(server, now);
+      }
+      break;
+    case DialState::DIAL_STATE_CONNECTING:
+      this->poll_connect_(server, now);
+      break;
+  }
+}
+
+void OutgoingConnectionManager::try_dial_(APIServer *server, uint32_t now) {
+  if (!network::is_connected()) {
+    // Flips within seconds of boot; recheck fast so a deep sleep wake
+    // window is not spent waiting
+    this->schedule_wait_(now, NETWORK_RETRY_MS);
+    return;
+  }
+  const char *host = this->target_host_();
+  if (host == nullptr) {
+    // The steady state until a dial-back client has ever connected
+    ESP_LOGV(TAG, "Not dialing: no target");
+    this->schedule_wait_(now, PRECONDITION_RETRY_MS);
+    return;
+  }
+  const bool at_limit = server->at_client_limit_();
+  if (at_limit || !server->noise_ctx_.has_psk()) {
+    ESP_LOGD(TAG, "Not dialing: %s", at_limit ? "max connections" : "no key");
+    // Not a dial failure; retry without escalating the backoff
+    this->schedule_wait_(now, PRECONDITION_RETRY_MS);
+    return;
+  }
+  struct sockaddr_storage addr;
+  socklen_t addr_len =
+      socket::set_sockaddr((struct sockaddr *) &addr, sizeof(addr), host, API_OUTGOING_CONNECTION_PORT);
+  if (addr_len == 0) {
+    ESP_LOGW(TAG, "Invalid target %s", host);
+#ifndef API_OUTGOING_CONNECTION_HOST
+    // A corrupt remembered value can never become dialable; forget it
+    // (covers an IPv6 literal left by an earlier enable_ipv6 build too)
+    this->saved_ = {};
+    if (!this->persist_target_()) {
+      ESP_LOGW(TAG, "Failed to clear target");
+    }
+#endif
+    this->schedule_retry_(now);
+    return;
+  }
+  this->dial_socket_ = socket::socket_loop_monitored(((struct sockaddr *) &addr)->sa_family, SOCK_STREAM, IPPROTO_TCP);
+  if (!this->dial_socket_ || this->dial_socket_->setblocking(false) != 0) {
+    ESP_LOGW(TAG, "Socket %s failed: errno %d", this->dial_socket_ ? "setblocking" : "create", errno);
+    this->schedule_retry_(now);
+    return;
+  }
+  ESP_LOGD(TAG, "Dialing %s:%u", host, API_OUTGOING_CONNECTION_PORT);
+  int err = this->dial_socket_->connect((struct sockaddr *) &addr, addr_len);
+  if (err == 0) {
+    // Immediate success (possible for localhost)
+    this->handoff_(server, now);
+    return;
+  }
+  if (errno != EINPROGRESS) {
+    ESP_LOGW(TAG, "Connect failed: errno %d", errno);
+    this->schedule_retry_(now);
+    return;
+  }
+  this->state_ = DialState::DIAL_STATE_CONNECTING;
+  this->state_ts_ = now;
+  this->last_poll_ = now;
+}
+
+void OutgoingConnectionManager::poll_connect_(APIServer *server, uint32_t now) {
+  if (now - this->state_ts_ >= CONNECT_TIMEOUT_MS) {
+    ESP_LOGW(TAG, "Connect timeout");
+    this->schedule_retry_(now);
+    return;
+  }
+  if (now - this->last_poll_ < CONNECT_POLL_INTERVAL_MS) {
+    return;
+  }
+  this->last_poll_ = now;
+  int err = 0;
+  switch (socket::poll_connect(*this->dial_socket_, err)) {
+    case socket::ConnectPollResult::CONNECT_POLL_PENDING:
+      break;
+    case socket::ConnectPollResult::CONNECT_POLL_CONNECTED:
+      this->handoff_(server, now);
+      break;
+    case socket::ConnectPollResult::CONNECT_POLL_ERROR:
+      ESP_LOGW(TAG, "Connect failed: %d", err);
+      this->schedule_retry_(now);
+      break;
+  }
+}
+
+void OutgoingConnectionManager::handoff_(APIServer *server, uint32_t now) {
+  this->dialed_conn_ = server->add_outgoing_client_(std::move(this->dial_socket_));
+  if (this->dialed_conn_ == nullptr) {
+    // Only preconditions (slot limit, key cleared) refuse the handoff; the
+    // peer is reachable, so do not escalate the backoff
+    this->schedule_wait_(now, PRECONDITION_RETRY_MS);
+    return;
+  }
+  // Connected; dialed_conn_ gates further dialing until the session settles
+  this->state_ = DialState::DIAL_STATE_IDLE;
+}
+
+void OutgoingConnectionManager::schedule_wait_(uint32_t now, uint32_t wait) {
+  this->dial_socket_.reset();  // no-op when the socket was handed off
+  this->state_ = DialState::DIAL_STATE_WAITING;
+  this->state_ts_ = now;
+  this->wait_ = wait;
+}
+
+void OutgoingConnectionManager::schedule_retry_(uint32_t now) {
+  // +/-20% jitter so a fleet of devices does not retry one server in lockstep
+  const uint32_t jitter_span = this->backoff_ / 5;
+  this->schedule_wait_(now, this->backoff_ - jitter_span + (random_uint32() % (2 * jitter_span + 1)));
+  this->backoff_ = std::min(this->backoff_ * 2, BACKOFF_MAX_MS);
+}
+
+void OutgoingConnectionManager::on_client_removed(APIConnection *conn, bool was_authenticated) {
+  if (conn != this->dialed_conn_) {
+    return;
+  }
+  this->dialed_conn_ = nullptr;
+  const uint32_t now = App.get_loop_component_start_time();
+  if (was_authenticated) {
+    // A working peer (e.g. a host: target that never sends the flag)
+    // disconnected normally; state is IDLE, so loop() applies the delay
+    this->backoff_ = BACKOFF_MIN_MS;
+  } else {
+    this->schedule_retry_(now);
+  }
+}
+
+void OutgoingConnectionManager::on_target_client(APIConnection *conn) {
+  // The target is connected; stop any dial in flight and reset the backoff.
+  // A dialed connection stays tracked unless it is this one: an inbound
+  // target must not orphan a still-open dial.
+  this->dial_socket_.reset();
+  if (conn == this->dialed_conn_) {
+    this->dialed_conn_ = nullptr;
+  }
+  this->state_ = DialState::DIAL_STATE_IDLE;
+  this->backoff_ = BACKOFF_MIN_MS;
+#ifndef API_OUTGOING_CONNECTION_HOST
+  SavedOutgoingTarget target{};
+  conn->get_peername_to(target.host);
+  if (target.host[0] == '\0') {
+    ESP_LOGW(TAG, "Could not read peer address; not remembering target");
+    return;
+  }
+  if (this->host_persisted_ && strcmp(target.host, this->saved_.host) == 0) {
+    return;  // unchanged and already on flash; avoid flash wear
+  }
+  // Use the fresh address this boot even if the flash write fails; a failed
+  // write is retried on the next flagged hello via host_persisted_
+  this->saved_ = target;
+  if (!this->persist_target_()) {
+    ESP_LOGW(TAG, "Failed to save target");
+    return;
+  }
+  ESP_LOGD(TAG, "Saved %s as outgoing connection target", this->saved_.host);
+#endif
+}
+
+void OutgoingConnectionManager::dump_config() const {
+  const char *host = this->target_host_();
+  if (host == nullptr) {
+    host = "none remembered yet";
+  }
+  // The boot delay differs from delay: on deep sleep builds, so print the
+  // value that actually applies
+  ESP_LOGCONFIG(TAG,
+                "  Outgoing connection port: %u\n"
+                "  Outgoing connection host: %s\n"
+                "  Outgoing connection boot delay: %ums",
+                API_OUTGOING_CONNECTION_PORT, host, BOOT_WAIT_MS);
+}
+
+}  // namespace esphome::api
+#endif  // USE_API && USE_API_OUTGOING_CONNECTION

esphome/components/api/api_outgoing_connection.h

@@ -0,0 +1,117 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#if defined(USE_API) && defined(USE_API_OUTGOING_CONNECTION)
+
+#ifdef USE_SOCKET_IMPL_LWIP_TCP
+#error "api outgoing_connection needs a socket implementation that can make outgoing connections"
+#endif
+#ifndef USE_API_NOISE
+#error "api outgoing_connection needs noise encryption so the peer is verified by key"
+#endif
+
+#include "esphome/components/socket/socket.h"
+#include "esphome/core/preferences.h"
+
+#include <memory>
+
+namespace esphome::api {
+
+class APIServer;
+class APIConnection;
+
+// Follows the build's address family (ifdef'd in socket/headers.h): toggling
+// enable_ipv6 changes the blob size, load() rejects the old blob, and the
+// target is simply relearned
+static constexpr size_t SAVED_TARGET_HOST_LEN = socket::SOCKADDR_STR_LEN;
+
+struct SavedOutgoingTarget {
+  // IP as text so the socket component's v4-mapped-IPv6 normalization is
+  // reused on both ends; empty = none remembered
+  char host[SAVED_TARGET_HOST_LEN];
+} PACKED;  // NOLINT
+
+/// Dials out when no dial-back target client is connected. Only the TCP
+/// direction flips: the device stays the Noise responder, so both sides
+/// still verify by key. Targets the YAML host or the last remembered client.
+class OutgoingConnectionManager {
+ public:
+  void setup();
+  void loop(APIServer *server);
+  /// A key-verified client declared itself a dial-back target; last one wins
+  void on_target_client(APIConnection *conn);
+  /// Clears the dialed-connection gate; dying unauthenticated escalates the backoff
+  void on_client_removed(APIConnection *conn, bool was_authenticated);
+  void on_shutdown() { this->dial_socket_.reset(); }
+  void dump_config() const;
+
+ protected:
+  enum class DialState : uint8_t {
+    DIAL_STATE_IDLE,
+    DIAL_STATE_WAITING,
+    DIAL_STATE_CONNECTING,
+  };
+
+  static constexpr uint32_t BACKOFF_MIN_MS = 5000;
+  static constexpr uint32_t BACKOFF_MAX_MS = 300000;
+  static constexpr uint32_t CONNECT_TIMEOUT_MS = 10000;
+  static constexpr uint32_t CONNECT_POLL_INTERVAL_MS = 250;
+  static constexpr uint32_t NETWORK_RETRY_MS = 500;
+  static constexpr uint32_t PRECONDITION_RETRY_MS = 5000;
+  // Boot waits for the client to connect in first; a deep sleep wake window
+  // is short, so connecting out immediately is the wake state
+#ifdef USE_DEEP_SLEEP
+  static constexpr uint32_t BOOT_WAIT_MS = 0;
+#else
+  static constexpr uint32_t BOOT_WAIT_MS = API_OUTGOING_CONNECTION_DELAY;
+#endif
+
+  void try_dial_(APIServer *server, uint32_t now);
+  void poll_connect_(APIServer *server, uint32_t now);
+  // Hand the connected socket to the server and gate on the new connection
+  void handoff_(APIServer *server, uint32_t now);
+  // Close any half-open dial and wait a jittered backoff before retrying
+  void schedule_retry_(uint32_t now);
+  // Wait without escalating the backoff (used for unmet preconditions)
+  void schedule_wait_(uint32_t now, uint32_t wait);
+#ifndef API_OUTGOING_CONNECTION_HOST
+  // Write saved_ to flash, tracking success in host_persisted_
+  bool persist_target_() {
+    this->host_persisted_ = this->target_pref_.save(&this->saved_) && global_preferences->sync();
+    return this->host_persisted_;
+  }
+#endif
+  const char *target_host_() const {
+#ifdef API_OUTGOING_CONNECTION_HOST
+    return API_OUTGOING_CONNECTION_HOST;
+#else
+    return this->saved_.host[0] != '\0' ? this->saved_.host : nullptr;
+#endif
+  }
+
+  // Pointers first (4 bytes each on 32-bit)
+  std::unique_ptr<socket::Socket> dial_socket_;
+  // Compared only, never dereferenced
+  APIConnection *dialed_conn_{nullptr};
+#ifndef API_OUTGOING_CONNECTION_HOST
+  ESPPreferenceObject target_pref_;
+#endif
+
+  // 4-byte types
+  uint32_t backoff_{BACKOFF_MIN_MS};
+  uint32_t wait_{BOOT_WAIT_MS};
+  uint32_t state_ts_{0};
+  uint32_t last_poll_{0};
+
+  // Byte-aligned types last
+#ifndef API_OUTGOING_CONNECTION_HOST
+  SavedOutgoingTarget saved_{};
+  // False while saved_ holds a value the flash write failed for; retried on
+  // the next flagged hello
+  bool host_persisted_{false};
+#endif
+  DialState state_{DialState::DIAL_STATE_WAITING};
+};
+
+}  // namespace esphome::api
+#endif  // USE_API && USE_API_OUTGOING_CONNECTION

esphome/components/api/api_pb2.cpp

@@ -15,6 +15,11 @@ bool HelloRequest::decode_varint(uint32_t field_id, proto_varint_value_t value)
     case 3:
       this->api_version_minor = value;
       break;
+#ifdef USE_API_OUTGOING_CONNECTION
+    case 4:
+      this->outgoing_connection_target = value != 0;
+      break;
+#endif
     default:
       return false;
   }
@@ -175,6 +180,9 @@ uint8_t *DeviceInfoResponse::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_
 #endif
 #ifdef USE_API_NOISE
   ProtoEncode::encode_bool(pos PROTO_ENCODE_DEBUG_ARG, 26, this->api_encryption_provisionable);
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  ProtoEncode::encode_bool(pos PROTO_ENCODE_DEBUG_ARG, 27, this->api_outgoing_connection_supported);
 #endif
   return pos;
 }
@@ -240,6 +248,9 @@ uint32_t DeviceInfoResponse::calculate_size() const {
 #endif
 #ifdef USE_API_NOISE
   size += ProtoSize::calc_bool(2, this->api_encryption_provisionable);
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  size += ProtoSize::calc_bool(2, this->api_outgoing_connection_supported);
 #endif
   return size;
 }

esphome/components/api/api_pb2.h

@@ -412,13 +412,16 @@ class CommandProtoMessage : public ProtoDecodableMessage {
 class HelloRequest final : public ProtoDecodableMessage {
  public:
   static constexpr uint16_t MESSAGE_TYPE = 1;
-  static constexpr uint8_t ESTIMATED_SIZE = 17;
+  static constexpr uint8_t ESTIMATED_SIZE = 19;
 #ifdef HAS_PROTO_MESSAGE_DUMP
   const LogString *message_name() const override { return LOG_STR("hello_request"); }
 #endif
   StringRef client_info{};
   uint32_t api_version_major{0};
   uint32_t api_version_minor{0};
+#ifdef USE_API_OUTGOING_CONNECTION
+  bool outgoing_connection_target{false};
+#endif
 #ifdef HAS_PROTO_MESSAGE_DUMP
   const char *dump_to(DumpBuffer &out) const override;
 #endif
@@ -549,7 +552,7 @@ class SerialProxyInfo final : public ProtoMessage {
 class DeviceInfoResponse final : public ProtoMessage {
  public:
   static constexpr uint16_t MESSAGE_TYPE = 10;
-  static constexpr uint16_t ESTIMATED_SIZE = 312;
+  static constexpr uint16_t ESTIMATED_SIZE = 315;
 #ifdef HAS_PROTO_MESSAGE_DUMP
   const LogString *message_name() const override { return LOG_STR("device_info_response"); }
 #endif
@@ -607,6 +610,9 @@ class DeviceInfoResponse final : public ProtoMessage {
 #endif
 #ifdef USE_API_NOISE
   bool api_encryption_provisionable{false};
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  bool api_outgoing_connection_supported{false};
 #endif
   uint8_t *encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const;
   uint32_t calculate_size() const;

esphome/components/api/api_pb2_dump.cpp

@@ -885,6 +885,9 @@ const char *HelloRequest::dump_to(DumpBuffer &out) const {
   dump_field(out, ESPHOME_PSTR("client_info"), this->client_info);
   dump_field(out, ESPHOME_PSTR("api_version_major"), this->api_version_major);
   dump_field(out, ESPHOME_PSTR("api_version_minor"), this->api_version_minor);
+#ifdef USE_API_OUTGOING_CONNECTION
+  dump_field(out, ESPHOME_PSTR("outgoing_connection_target"), this->outgoing_connection_target);
+#endif
   return out.c_str();
 }
 const char *HelloResponse::dump_to(DumpBuffer &out) const {
@@ -1008,6 +1011,9 @@ const char *DeviceInfoResponse::dump_to(DumpBuffer &out) const {
 #endif
 #ifdef USE_API_NOISE
   dump_field(out, ESPHOME_PSTR("api_encryption_provisionable"), this->api_encryption_provisionable);
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  dump_field(out, ESPHOME_PSTR("api_outgoing_connection_supported"), this->api_outgoing_connection_supported);
 #endif
   return out.c_str();
 }

esphome/components/api/api_server.cpp

@@ -34,7 +34,52 @@ APIServer::APIServer() { global_api_server = this; }
 void APIServer::socket_failed_(const LogString *msg) {
   ESP_LOGW(TAG, "Socket %s: errno %d", LOG_STR_ARG(msg), errno);
   this->destroy_socket_();
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Dial-out needs no listener; degrade instead of stopping the component
+  this->status_set_error(LOG_STR("listen socket failed"));
+#else
   this->mark_failed();
+#endif
+}
+
+bool APIServer::create_listen_socket_() {
+  this->socket_ = socket::socket_ip_loop_monitored(SOCK_STREAM, 0).release();  // monitored for incoming connections
+  if (this->socket_ == nullptr) {
+    this->socket_failed_(LOG_STR("creation"));
+    return false;
+  }
+  int enable = 1;
+  int err = this->socket_->setsockopt(SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
+  if (err != 0) {
+    ESP_LOGW(TAG, "Socket reuseaddr: errno %d", errno);
+    // we can still continue
+  }
+  err = this->socket_->setblocking(false);
+  if (err != 0) {
+    this->socket_failed_(LOG_STR("nonblocking"));
+    return false;
+  }
+
+  struct sockaddr_storage server;
+
+  socklen_t sl = socket::set_sockaddr_any((struct sockaddr *) &server, sizeof(server), this->port_);
+  if (sl == 0) {
+    this->socket_failed_(LOG_STR("set sockaddr"));
+    return false;
+  }
+
+  err = this->socket_->bind((struct sockaddr *) &server, sl);
+  if (err != 0) {
+    this->socket_failed_(LOG_STR("bind"));
+    return false;
+  }
+
+  err = this->socket_->listen(this->listen_backlog_);
+  if (err != 0) {
+    this->socket_failed_(LOG_STR("listen"));
+    return false;
+  }
+  return true;
 }
 
 void APIServer::setup() {
@@ -53,42 +98,14 @@ void APIServer::setup() {
 #endif
 #endif
 
-  this->socket_ = socket::socket_ip_loop_monitored(SOCK_STREAM, 0).release();  // monitored for incoming connections
-  if (this->socket_ == nullptr) {
-    this->socket_failed_(LOG_STR("creation"));
-    return;
-  }
-  int enable = 1;
-  int err = this->socket_->setsockopt(SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
-  if (err != 0) {
-    ESP_LOGW(TAG, "Socket reuseaddr: errno %d", errno);
-    // we can still continue
-  }
-  err = this->socket_->setblocking(false);
-  if (err != 0) {
-    this->socket_failed_(LOG_STR("nonblocking"));
-    return;
-  }
-
-  struct sockaddr_storage server;
-
-  socklen_t sl = socket::set_sockaddr_any((struct sockaddr *) &server, sizeof(server), this->port_);
-  if (sl == 0) {
-    this->socket_failed_(LOG_STR("set sockaddr"));
-    return;
-  }
-
-  err = this->socket_->bind((struct sockaddr *) &server, sl);
-  if (err != 0) {
-    this->socket_failed_(LOG_STR("bind"));
-    return;
-  }
-
-  err = this->socket_->listen(this->listen_backlog_);
-  if (err != 0) {
-    this->socket_failed_(LOG_STR("listen"));
+#ifdef USE_API_OUTGOING_CONNECTION
+  // A dead listener degrades to an error status; dial-out still runs
+  this->create_listen_socket_();
+#else
+  if (!this->create_listen_socket_()) {
     return;
   }
+#endif
 
 #ifdef USE_LOGGER
   if (logger::global_logger != nullptr) {
@@ -135,6 +152,9 @@ void APIServer::setup() {
   if (this->reboot_timeout_ != 0 && !this->provisioning_pending_()) {
     this->status_set_warning(LOG_STR("waiting for client connection"));
   }
+#ifdef USE_API_OUTGOING_CONNECTION
+  this->outgoing_conn_.setup();
+#endif
 }
 
 void APIServer::loop() {
@@ -143,6 +163,12 @@ void APIServer::loop() {
     this->accept_new_connections_();
   }
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  if (!this->shutting_down_) {
+    this->outgoing_conn_.loop(this);
+  }
+#endif
+
   if (this->api_connection_count_ == 0) {
     // Check reboot timeout - done in loop to avoid scheduler heap churn
     // (cancelled scheduler items sit in heap memory until their scheduled time).
@@ -151,7 +177,12 @@ void APIServer::loop() {
     if (this->reboot_timeout_ != 0 && !this->provisioning_pending_()) {
       const uint32_t now = App.get_loop_component_start_time();
       if (now - this->last_connected_ > this->reboot_timeout_) {
-        ESP_LOGE(TAG, "No clients; rebooting");
+        // Distinguish a wrong-key peer from nothing connecting at all
+        if (this->saw_unauthenticated_client_) {
+          ESP_LOGE(TAG, "Clients connected but none authenticated; rebooting");
+        } else {
+          ESP_LOGE(TAG, "No clients; rebooting");
+        }
         App.reboot();
       }
     }
@@ -203,6 +234,15 @@ void APIServer::remove_client_(uint8_t client_index) {
   std::string client_peername(client->get_peername_to(peername_buf));
 #endif
 
+  // Read before the swap-and-reset below destroys the connection
+  const bool was_authenticated = client->is_authenticated();
+#ifdef USE_API_OUTGOING_CONNECTION
+  if (client->flags_.outgoing_connection_target) {
+    this->outgoing_target_count_--;
+  }
+  this->outgoing_conn_.on_client_removed(client.get(), was_authenticated);
+#endif
+
   // Close socket now (was deferred from on_fatal_error to allow getpeername)
   client->helper_->close();
 
@@ -221,9 +261,18 @@ void APIServer::remove_client_(uint8_t client_index) {
 
   // Last client disconnected - set warning and start tracking for reboot timeout
   // (suppressed while provisioning is pending - see loop()).
+  // Refresh on every authenticated removal, not just the last one, so an
+  // unauthenticated straggler removed later (e.g. a port scan, or a dial to
+  // a host that accepts TCP but never speaks the API) cannot discard a
+  // healthy session's timestamp and trigger a spurious reboot
+  if (was_authenticated) {
+    this->last_connected_ = App.get_loop_component_start_time();
+    this->saw_unauthenticated_client_ = false;
+  } else {
+    this->saw_unauthenticated_client_ = true;
+  }
   if (this->api_connection_count_ == 0 && this->reboot_timeout_ != 0 && !this->provisioning_pending_()) {
     this->status_set_warning(LOG_STR("waiting for client connection"));
-    this->last_connected_ = App.get_loop_component_start_time();
   }
 
 #ifdef USE_API_CLIENT_DISCONNECTED_TRIGGER
@@ -245,7 +294,7 @@ void __attribute__((flatten)) APIServer::accept_new_connections_() {
     sock->getpeername_to(peername);
 
     // Check if we're at the connection limit
-    if (this->api_connection_count_ >= MAX_API_CONNECTIONS) {
+    if (this->at_client_limit_()) {
       ESP_LOGW(TAG, "Max connections (%d), rejecting %s", MAX_API_CONNECTIONS, peername);
       // Immediately close - socket destructor will handle cleanup
       sock.reset();
@@ -254,18 +303,53 @@ void __attribute__((flatten)) APIServer::accept_new_connections_() {
 
     ESP_LOGD(TAG, "Accept %s", peername);
 
-    auto *conn = new APIConnection(std::move(sock), this);
-    this->clients_[this->api_connection_count_++].reset(conn);
-    conn->start();
-
-    // First client connected - clear warning and update timestamp
-    if (this->api_connection_count_ == 1 && this->reboot_timeout_ != 0 && !this->provisioning_pending_()) {
-      this->status_clear_warning();
-      this->last_connected_ = App.get_loop_component_start_time();
-    }
+    this->add_client_(new APIConnection(std::move(sock), this));
   }
 }
 
+bool APIServer::add_client_(APIConnection *conn) {
+  if (this->at_client_limit_()) {
+    // Callers check first; enforce the array bound where the write happens
+    ESP_LOGW(TAG, "Max connections (%d), dropping client", MAX_API_CONNECTIONS);
+    delete conn;
+    return false;
+  }
+  this->clients_[this->api_connection_count_++].reset(conn);
+  conn->start();
+
+  // First client connected - clear warning. The reboot watchdog timestamp is
+  // refreshed when an authenticated client is removed (see remove_client_),
+  // never on bare TCP connects.
+  if (this->api_connection_count_ == 1 && this->reboot_timeout_ != 0 && !this->provisioning_pending_()) {
+    this->status_clear_warning();
+  }
+  return true;
+}
+
+#ifdef USE_API_OUTGOING_CONNECTION
+APIConnection *APIServer::add_outgoing_client_(std::unique_ptr<socket::Socket> sock) {
+  // Re-check at the handoff: inbound clients may have filled the slots and
+  // the PSK may have been cleared (mark_outgoing() needs the noise helper)
+  const bool at_limit = this->at_client_limit_();
+  if (at_limit || !this->noise_ctx_.has_psk()) {
+    ESP_LOGW(TAG, "Dropping outgoing connection (%s)", at_limit ? "max connections" : "no key");
+    return nullptr;
+  }
+  auto *conn = new APIConnection(std::move(sock), this);
+  if (!this->add_client_(conn)) {
+    return nullptr;
+  }
+  // After start(): sends our server hello first so the peer can pick the key
+  conn->mark_outgoing();
+  return conn;
+}
+
+void APIServer::on_outgoing_target_client(APIConnection *conn) {
+  this->outgoing_target_count_++;
+  this->outgoing_conn_.on_target_client(conn);
+}
+#endif
+
 void APIServer::dump_config() {
   char addr_buf[network::USE_ADDRESS_BUFFER_SIZE];
   ESP_LOGCONFIG(TAG,
@@ -282,6 +366,9 @@ void APIServer::dump_config() {
 #else
   ESP_LOGCONFIG(TAG, "  Noise encryption: NO");
 #endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  this->outgoing_conn_.dump_config();
+#endif
 }
 
 void APIServer::handle_disconnect(APIConnection *conn) {}
@@ -576,6 +663,8 @@ bool APIServer::update_noise_psk_(const SavedNoisePsk &new_psk, const LogString
         if (!c->send_message(req)) {
           API_LOG_MSG_DROPPED(TAG, "Disconnect request");
         }
+        // Force it: a session from before the key was active must not survive
+        c->flags_.next_close = true;
       }
     });
   }
@@ -687,6 +776,9 @@ void APIServer::on_shutdown() {
 
   // Close the listening socket to prevent new connections
   this->destroy_socket_();
+#ifdef USE_API_OUTGOING_CONNECTION
+  this->outgoing_conn_.on_shutdown();
+#endif
 
   // Change batch delay to 5ms for quick flushing during shutdown
   this->batch_delay_ = 5;

esphome/components/api/api_server.h

@@ -11,6 +11,7 @@
 #endif
 #include "api_pb2.h"
 #include "api_pb2_service.h"
+#include "api_outgoing_connection.h"
 #include "esphome/components/socket/socket.h"
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
@@ -81,6 +82,10 @@ class APIServer final : public Component,
   void set_noise_psk(noise::psk_t psk) { this->noise_ctx_.set_psk(psk); }
   noise::NoiseContext &get_noise_ctx() { return this->noise_ctx_; }
 #endif  // USE_API_NOISE
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Called by APIConnection when a client declares itself a dial-back target in its hello
+  void on_outgoing_target_client(APIConnection *conn);
+#endif
 
   void handle_disconnect(APIConnection *conn);
 #ifdef USE_BINARY_SENSOR
@@ -258,6 +263,16 @@ class APIServer final : public Component,
  protected:
   // Accept incoming socket connections. Only called when socket has pending connections.
   void __attribute__((noinline)) accept_new_connections_();
+  // Insert a constructed connection into the client slots and start it.
+  // Takes ownership; deletes the connection and returns false at the limit
+  bool add_client_(APIConnection *conn);
+  bool at_client_limit_() const { return this->api_connection_count_ >= MAX_API_CONNECTIONS; }
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Returns the new connection, or nullptr (socket dropped) when at the limit
+  APIConnection *add_outgoing_client_(std::unique_ptr<socket::Socket> sock);
+  bool has_outgoing_target_client_() const { return this->outgoing_target_count_ != 0; }
+  friend class OutgoingConnectionManager;
+#endif
   // Remove a disconnected client by index. Swaps with the last populated slot and resets it.
   void __attribute__((noinline)) remove_client_(uint8_t client_index);
 
@@ -297,6 +312,7 @@ class APIServer final : public Component,
     this->socket_ = nullptr;
   }
   void socket_failed_(const LogString *msg);
+  bool create_listen_socket_();
   // Pointers and pointer-like types first (4 bytes each)
   socket::ListenSocket *socket_{nullptr};
 #ifdef USE_API_CLIENT_CONNECTED_TRIGGER
@@ -349,8 +365,16 @@ class APIServer final : public Component,
   // Connection limits - these defaults will be overridden by config values
   // from cv.SplitDefault in __init__.py which sets platform-specific defaults.
   uint8_t listen_backlog_{4};
-  bool shutting_down_ = false;
+  // Bit-packed so the two flags share one byte
+  bool shutting_down_ : 1 = false;
+  // For the reboot log: whether any removal since the last watchdog refresh
+  // was an unauthenticated session (e.g. a wrong-key peer)
+  bool saw_unauthenticated_client_ : 1 = false;
   uint8_t api_connection_count_{0};
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Connected clients whose hello declared them a dial-back target
+  uint8_t outgoing_target_count_{0};
+#endif
 #if defined(USE_PROVISIONING) && defined(USE_API_NOISE)
   // Index assigned by the provisioning manager for reporting this transport's state.
   uint8_t provisioning_source_{0};
@@ -360,6 +384,9 @@ class APIServer final : public Component,
   noise::NoiseContext noise_ctx_;
   ESPPreferenceObject noise_pref_;
 #endif  // USE_API_NOISE
+#ifdef USE_API_OUTGOING_CONNECTION
+  OutgoingConnectionManager outgoing_conn_;
+#endif
 };
 
 extern APIServer *global_api_server;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

esphome/components/async_tcp/async_tcp_socket.cpp

@@ -42,7 +42,16 @@ bool AsyncClient::connect(const char *host, uint16_t port) {
     return false;
   }
 
-  socket_->setblocking(false);
+  if (socket_->setblocking(false) != 0) {
+    // Capture before the log and reset() below can clobber errno; a blocking
+    // connect()/read() would otherwise stall the whole loop
+    const int saved_errno = errno;
+    ESP_LOGE(TAG, "Failed to set nonblocking: errno %d", saved_errno);
+    socket_.reset();
+    if (error_cb_)
+      error_cb_(error_arg_, this, saved_errno);
+    return false;
+  }
 
   int err = socket_->connect((struct sockaddr *) &addr, addrlen);
   if (err == 0) {
@@ -97,45 +106,22 @@ void AsyncClient::loop() {
     return;
 
   if (connecting_) {
-    // For connecting, we need to check writability, not readability
-    // The Application's select() only monitors read FDs, so we do our own check here
-    // For ESP platforms lwip_select() might be faster, but this code isn't used
-    // on those platforms anyway. If it was, we'd fix the Application select()
-    // to report writability instead of doing it this way.
-    int fd = socket_->get_fd();
-    if (fd < 0) {
-      ESP_LOGW(TAG, "Invalid socket fd");
-      close();
-      return;
-    }
-
-    fd_set writefds;
-    FD_ZERO(&writefds);
-    FD_SET(fd, &writefds);
-
-    struct timeval tv = {0, 0};
-    int ret = select(fd + 1, nullptr, &writefds, nullptr, &tv);
-
-    if (ret > 0 && FD_ISSET(fd, &writefds)) {
-      int error = 0;
-      socklen_t len = sizeof(error);
-      if (socket_->getsockopt(SOL_SOCKET, SO_ERROR, &error, &len) == 0 && error == 0) {
+    int err = 0;
+    switch (socket::poll_connect(*socket_, err)) {
+      case socket::ConnectPollResult::CONNECT_POLL_PENDING:
+        break;
+      case socket::ConnectPollResult::CONNECT_POLL_CONNECTED:
         connecting_ = false;
         connected_ = true;
         if (connect_cb_)
           connect_cb_(connect_arg_, this);
-      } else {
-        ESP_LOGW(TAG, "Connection failed: %d", error);
+        break;
+      case socket::ConnectPollResult::CONNECT_POLL_ERROR:
+        ESP_LOGW(TAG, "Connection failed: %d", err);
         close();
         if (error_cb_)
-          error_cb_(error_arg_, this, error);
-      }
-    } else if (ret < 0) {
-      const int err = errno;
-      ESP_LOGE(TAG, "Select error: %d", err);
-      close();
-      if (error_cb_)
-        error_cb_(error_arg_, this, err);
+          error_cb_(error_arg_, this, err);
+        break;
     }
   } else if (connected_) {
     // For connected sockets, use the Application's select() results

esphome/components/const/__init__.py

@@ -22,6 +22,7 @@ CONF_ENABLE_OTA_DOWNGRADE_PROTECTION = "enable_ota_downgrade_protection"
 CONF_ENABLED = "enabled"
 CONF_GYROSCOPE_ODR = "gyroscope_odr"
 CONF_GYROSCOPE_RANGE = "gyroscope_range"
+CONF_HOST = "host"
 CONF_IAQ = "iaq"
 CONF_IGNORE_NOT_FOUND = "ignore_not_found"
 CONF_IS_WRGB = "is_wrgb"

esphome/components/esphome/ota/ota_esphome.cpp

@@ -358,7 +358,10 @@ void ESPHomeOTAComponent::handle_data_() {
   tv.tv_usec = 0;
   this->client_->setsockopt(SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
   this->client_->setsockopt(SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
-  this->client_->setblocking(true);
+  if (this->client_->setblocking(true) != 0) {
+    this->log_socket_error_(LOG_STR("blocking"));
+    goto error;  // NOLINT(cppcoreguidelines-avoid-goto)
+  }
 
   // Acknowledge auth OK - 1 byte
   this->write_byte_(ota::OTA_RESPONSE_AUTH_OK);

esphome/components/socket/__init__.py

@@ -17,6 +17,8 @@ CONF_IMPLEMENTATION = "implementation"
 IMPLEMENTATION_LWIP_TCP = "lwip_tcp"
 IMPLEMENTATION_LWIP_SOCKETS = "lwip_sockets"
 IMPLEMENTATION_BSD_SOCKETS = "bsd_sockets"
+# Implementations whose sockets cannot make outgoing connections
+IMPLEMENTATIONS_WITHOUT_CONNECT = frozenset({IMPLEMENTATION_LWIP_TCP})
 
 # Socket tracking infrastructure
 # Components register their socket needs and platforms read this to configure appropriately

esphome/components/socket/bsd_sockets_impl.cpp

@@ -59,13 +59,15 @@ int BSDSocketImpl::close() {
 
 int BSDSocketImpl::setblocking(bool blocking) {
   int fl = ::fcntl(this->fd_, F_GETFL, 0);
+  if (fl < 0) {
+    return fl;
+  }
   if (blocking) {
     fl &= ~O_NONBLOCK;
   } else {
     fl |= O_NONBLOCK;
   }
-  ::fcntl(this->fd_, F_SETFL, fl);
-  return 0;
+  return ::fcntl(this->fd_, F_SETFL, fl);
 }
 
 size_t BSDSocketImpl::getpeername_to(std::span<char, SOCKADDR_STR_LEN> buf) {

esphome/components/socket/lwip_sockets_impl.cpp

@@ -49,13 +49,15 @@ int LwIPSocketImpl::close() {
 
 int LwIPSocketImpl::setblocking(bool blocking) {
   int fl = lwip_fcntl(this->fd_, F_GETFL, 0);
+  if (fl < 0) {
+    return fl;
+  }
   if (blocking) {
     fl &= ~O_NONBLOCK;
   } else {
     fl |= O_NONBLOCK;
   }
-  lwip_fcntl(this->fd_, F_SETFL, fl);
-  return 0;
+  return lwip_fcntl(this->fd_, F_SETFL, fl);
 }
 
 size_t LwIPSocketImpl::getpeername_to(std::span<char, SOCKADDR_STR_LEN> buf) {

esphome/components/socket/socket.cpp

@@ -2,6 +2,9 @@
 #if defined(USE_SOCKET_IMPL_LWIP_TCP) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS) || defined(USE_SOCKET_IMPL_BSD_SOCKETS)
 #include <cerrno>
 #include <cstring>
+#ifdef USE_SOCKET_IMPL_BSD_SOCKETS
+#include <sys/select.h>
+#endif
 #include <string>
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
@@ -165,7 +168,10 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_
 #else
     // Use LWIP-specific functions
     ip6_addr_t ip6;
-    inet6_aton(ip_address, &ip6);
+    if (inet6_aton(ip_address, &ip6) == 0) {
+      errno = EINVAL;
+      return 0;
+    }
     memcpy(server->sin6_addr.un.u32_addr, ip6.addr, sizeof(ip6.addr));
 #endif
     return sizeof(sockaddr_in6);
@@ -185,12 +191,58 @@ socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const char *ip_
     return 0;
   }
 #else
-  server->sin_addr.s_addr = inet_addr(ip_address);
+  // Unlike inet_addr(), inet_aton() can signal failure while still
+  // accepting the broadcast address 255.255.255.255
+  if (inet_aton(ip_address, &server->sin_addr) == 0) {
+    errno = EINVAL;
+    return 0;
+  }
 #endif
   server->sin_port = htons(port);
   return sizeof(sockaddr_in);
 }
 
+#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
+ConnectPollResult poll_connect(Socket &sock, int &err_out) {
+  int fd = sock.get_fd();
+  if (fd < 0 || fd >= FD_SETSIZE) {
+    // FD_SET on either is undefined behavior
+    err_out = EBADF;
+    return ConnectPollResult::CONNECT_POLL_ERROR;
+  }
+  // Connect completion is a write event; the main loop only selects on reads
+  fd_set writefds;
+  FD_ZERO(&writefds);
+  FD_SET(fd, &writefds);
+  struct timeval tv = {0, 0};
+#ifdef USE_SOCKET_IMPL_LWIP_SOCKETS
+  // LWIP_COMPAT_SOCKETS may be off (LibreTiny), so use the lwip symbol directly
+  int ret = lwip_select(fd + 1, nullptr, &writefds, nullptr, &tv);
+#else
+  // Global-scope select: the entity namespace esphome::select shadows it here
+  int ret = ::select(fd + 1, nullptr, &writefds, nullptr, &tv);
+#endif
+  if (ret < 0) {
+    err_out = errno;
+    return ConnectPollResult::CONNECT_POLL_ERROR;
+  }
+  if (ret == 0 || !FD_ISSET(fd, &writefds)) {
+    return ConnectPollResult::CONNECT_POLL_PENDING;
+  }
+  int error = 0;
+  socklen_t len = sizeof(error);
+  if (sock.getsockopt(SOL_SOCKET, SO_ERROR, &error, &len) != 0) {
+    err_out = errno;
+    return ConnectPollResult::CONNECT_POLL_ERROR;
+  }
+  if (error != 0) {
+    err_out = error;
+    return ConnectPollResult::CONNECT_POLL_ERROR;
+  }
+  return ConnectPollResult::CONNECT_POLL_CONNECTED;
+}
+#endif
+
 socklen_t set_sockaddr_any(struct sockaddr *addr, socklen_t addrlen, uint16_t port) {
 #if USE_NETWORK_IPV6
   if (addrlen < sizeof(sockaddr_in6)) {

esphome/components/socket/socket.h

@@ -145,6 +145,19 @@ inline socklen_t set_sockaddr(struct sockaddr *addr, socklen_t addrlen, const st
 /// Set a sockaddr to the any address and specified port for the IP version used by socket_ip().
 socklen_t set_sockaddr_any(struct sockaddr *addr, socklen_t addrlen, uint16_t port);
 
+#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
+enum class ConnectPollResult : uint8_t {
+  CONNECT_POLL_PENDING,
+  CONNECT_POLL_CONNECTED,
+  CONNECT_POLL_ERROR,
+};
+
+/// Check a non-blocking connect() for completion without blocking. On
+/// CONNECT_POLL_ERROR, err_out holds the socket's SO_ERROR, or errno when the
+/// poll itself failed.
+ConnectPollResult poll_connect(Socket &sock, int &err_out);
+#endif
+
 /// Format sockaddr into caller-provided buffer, returns length written (excluding null)
 size_t format_sockaddr_to(const struct sockaddr *addr_ptr, socklen_t len, std::span<char, SOCKADDR_STR_LEN> buf);
 

esphome/components/statsd/__init__.py

@@ -1,5 +1,6 @@
 import esphome.codegen as cg
 from esphome.components import binary_sensor, sensor
+from esphome.components.const import CONF_HOST
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_BINARY_SENSORS,
@@ -14,7 +15,6 @@ AUTO_LOAD = ["socket"]
 CODEOWNERS = ["@Links2004"]
 DEPENDENCIES = ["network"]
 
-CONF_HOST = "host"
 CONF_PREFIX = "prefix"
 
 statsd_component_ns = cg.esphome_ns.namespace("statsd")

esphome/components/udp/udp_component.cpp

@@ -13,9 +13,16 @@ void UDPComponent::setup() {
 #if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
   for (const auto &address : this->addresses_) {
     struct sockaddr saddr {};
-    socket::set_sockaddr(&saddr, sizeof(saddr), address, this->broadcast_port_);
+    if (socket::set_sockaddr(&saddr, sizeof(saddr), address, this->broadcast_port_) == 0) {
+      ESP_LOGW(TAG, "Invalid address %s", address);
+      continue;
+    }
     this->sockaddrs_.push_back(saddr);
   }
+  if (!this->addresses_.empty() && this->sockaddrs_.empty()) {
+    // Sending would be a silent no-op; surface the misconfiguration
+    this->status_set_warning(LOG_STR("no valid addresses"));
+  }
   // set up broadcast socket
   if (this->should_broadcast_) {
     this->broadcast_socket_ = socket::socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

esphome/components/wake_on_lan/wake_on_lan.cpp

@@ -34,6 +34,10 @@ void WakeOnLanButton::press_action() {
   struct sockaddr_storage saddr {};
   auto addr_len =
       socket::set_sockaddr(reinterpret_cast<sockaddr *>(&saddr), sizeof(saddr), "255.255.255.255", this->port_);
+  if (addr_len == 0) {
+    ESP_LOGW(TAG, "Invalid broadcast address");
+    return;
+  }
   uint8_t buffer[6 + sizeof this->macaddr_ * 16];
   memcpy(buffer, PREFIX, sizeof(PREFIX));
   for (size_t i = 0; i != 16; i++) {

esphome/core/defines.h

@@ -214,6 +214,11 @@
 #define USE_API_HOMEASSISTANT_SERVICES
 #define USE_API_HOMEASSISTANT_STATES
 #define USE_API_NOISE
+#if !defined(USE_ESP8266) && !defined(USE_RP2)  // raw-lwip sockets cannot make outgoing connections
+#define USE_API_OUTGOING_CONNECTION
+#define API_OUTGOING_CONNECTION_PORT 6054
+#define API_OUTGOING_CONNECTION_DELAY 60000
+#endif
 #define USE_API_VARINT64
 #define USE_API_PLAINTEXT
 #define USE_API_USER_DEFINED_ACTIONS

tests/component_tests/api/test_outgoing_connection.py

@@ -0,0 +1,145 @@
+"""Tests for the api outgoing_connection option."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from esphome.components.api import (
+    CONFIG_SCHEMA,
+    _validate_outgoing_host_ipv6,
+    _validate_outgoing_socket_implementation,
+)
+from esphome.components.esp32 import KEY_BOARD, KEY_VARIANT, VARIANT_ESP32
+import esphome.config_validation as cv
+from esphome.const import PlatformFramework
+from esphome.core import CORE
+from esphome.types import ConfigType
+from tests.component_tests.types import SetCoreConfigCallable
+
+KEY = "bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU="
+ESP32_PLATFORM_DATA = {KEY_BOARD: "esp32dev", KEY_VARIANT: VARIANT_ESP32}
+
+
+def _api_config(outgoing: ConfigType, *, encryption: bool = True) -> ConfigType:
+    config: ConfigType = {"outgoing_connection": outgoing}
+    if encryption:
+        config["encryption"] = {"key": KEY}
+    return config
+
+
+def test_outgoing_connection_generates_defines(
+    generate_main: Callable[[str | Path], str],
+) -> None:
+    """A valid config emits the compile-time defines with defaults applied."""
+    generate_main("tests/component_tests/api/test_outgoing_connection.yaml")
+
+    defines = {define.name: define.value for define in CORE.defines}
+    assert "USE_API_OUTGOING_CONNECTION" in defines
+    assert str(defines["API_OUTGOING_CONNECTION_HOST"]) == '"192.168.1.2"'
+    assert str(defines["API_OUTGOING_CONNECTION_PORT"]) == "6054"
+    assert str(defines["API_OUTGOING_CONNECTION_DELAY"]) == "60000"
+
+
+def test_outgoing_connection_defaults(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    config = CONFIG_SCHEMA(_api_config({"host": "192.168.1.2"}))
+    outgoing = config["outgoing_connection"]
+    assert outgoing["port"] == 6054
+    assert outgoing["delay"].total_milliseconds == 60000
+
+
+def test_outgoing_connection_bare_block(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    """A bare outgoing_connection: block is valid; the device dials the
+    remembered last dial-back client."""
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    config = CONFIG_SCHEMA(_api_config(None))
+    outgoing = config["outgoing_connection"]
+    assert "host" not in outgoing
+    assert outgoing["port"] == 6054
+
+
+def test_outgoing_connection_delay_bounded(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    """A delay past half the uint32 millisecond range is rejected, not wrapped."""
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    with pytest.raises(cv.Invalid, match="value must be at most"):
+        CONFIG_SCHEMA(_api_config({"delay": "60d"}))
+
+
+def test_outgoing_connection_requires_encryption(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    with pytest.raises(cv.Invalid, match="requires 'encryption'"):
+        CONFIG_SCHEMA(_api_config({"host": "192.168.1.2"}, encryption=False))
+
+
+@pytest.mark.parametrize(
+    "platform_framework",
+    [PlatformFramework.ESP8266_ARDUINO, PlatformFramework.RP2040_ARDUINO],
+)
+def test_outgoing_connection_rejected_on_raw_lwip_platforms(
+    set_core_config: SetCoreConfigCallable,
+    platform_framework: PlatformFramework,
+) -> None:
+    set_core_config(platform_framework)
+    with pytest.raises(cv.Invalid, match="not supported on this platform"):
+        CONFIG_SCHEMA(_api_config({"host": "192.168.1.2"}))
+
+
+def test_outgoing_connection_rejects_lwip_tcp_selected_on_esp32(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    """An explicit lwip_tcp selection is caught at final validate."""
+    set_core_config(
+        PlatformFramework.ESP32_IDF,
+        platform_data=ESP32_PLATFORM_DATA,
+        full_config={"socket": {"implementation": "lwip_tcp"}},
+    )
+    config = CONFIG_SCHEMA(_api_config({"host": "192.168.1.2"}))
+    with pytest.raises(cv.Invalid, match="lwip_tcp"):
+        _validate_outgoing_socket_implementation(config)
+
+
+def test_outgoing_connection_rejects_hostnames(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    with pytest.raises(cv.Invalid, match="not a valid IP address"):
+        CONFIG_SCHEMA(_api_config({"host": "homeassistant.local"}))
+
+
+def test_outgoing_connection_ipv6_host_requires_ipv6(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    set_core_config(PlatformFramework.ESP32_IDF, platform_data=ESP32_PLATFORM_DATA)
+    config = CONFIG_SCHEMA(_api_config({"host": "fd00::1"}))
+    with pytest.raises(cv.Invalid, match="IPv6 is not"):
+        _validate_outgoing_host_ipv6(config)
+
+
+def test_outgoing_connection_ipv6_host_passes_with_ipv6_enabled(
+    set_core_config: SetCoreConfigCallable,
+) -> None:
+    set_core_config(
+        PlatformFramework.ESP32_IDF,
+        platform_data=ESP32_PLATFORM_DATA,
+        full_config={"network": {"enable_ipv6": True}},
+    )
+    config = CONFIG_SCHEMA(_api_config({"host": "fd00::1"}))
+    assert _validate_outgoing_host_ipv6(config) is config
+
+
+def test_outgoing_connection_ipv6_host_with_ipv6(
+    generate_main: Callable[[str | Path], str],
+) -> None:
+    generate_main("tests/component_tests/api/test_outgoing_connection_ipv6.yaml")
+
+    defines = {define.name: define.value for define in CORE.defines}
+    assert str(defines["API_OUTGOING_CONNECTION_HOST"]) == '"fd00::1"'

tests/component_tests/api/test_outgoing_connection.yaml

@@ -0,0 +1,17 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+wifi:
+  ssid: SomeNetwork
+  password: SomePassword
+
+logger:
+
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    host: 192.168.1.2

tests/component_tests/api/test_outgoing_connection_ipv6.yaml

@@ -0,0 +1,20 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+
+wifi:
+  ssid: SomeNetwork
+  password: SomePassword
+
+network:
+  enable_ipv6: true
+
+logger:
+
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    host: fd00::1

tests/components/api/test-outgoing-connection.bk72xx-ard.yaml

@@ -0,0 +1,13 @@
+packages:
+  common: !include common-base.yaml
+
+wifi:
+  ssid: MySSID
+  password: password1
+
+# Outgoing connection on the lwip_sockets implementation used by LibreTiny
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    host: 192.168.1.2

tests/components/api/test-outgoing-connection.esp32-idf.yaml

@@ -0,0 +1,16 @@
+packages:
+  common: !include common-base.yaml
+
+wifi:
+  ssid: MySSID
+  password: password1
+
+# Outgoing connection: the device dials out when no dial-back client is
+# connected. Requires encryption so the peer is verified by key.
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    host: 192.168.1.2
+    port: 6054
+    delay: 60s

tests/components/api/test-outgoing-connection.host.yaml

@@ -0,0 +1,11 @@
+packages:
+  common: !include common-base.yaml
+
+network:
+
+# No host set: the device dials the last remembered Home Assistant address
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    delay: 30s

tests/integration/conftest.py

@@ -702,3 +702,11 @@ async def run_compiled(
         )
 
     yield _run_compiled
+
+
+@pytest.fixture
+def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
+    """Point host preferences at a per-test dir so every run starts clean
+    (host preferences otherwise persist to ~/.esphome/prefs, keyed only by
+    device name)."""
+    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))

tests/integration/fixtures/api_outgoing_connection.yaml

@@ -0,0 +1,14 @@
+esphome:
+  name: outgoing-conn-test
+
+host:
+
+logger:
+
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    host: 127.0.0.1
+    port: OUTGOING_PORT
+    delay: 1s

tests/integration/fixtures/api_outgoing_connection_remembered.yaml

@@ -0,0 +1,13 @@
+esphome:
+  name: outgoing-conn-test
+
+host:
+
+logger:
+
+api:
+  encryption:
+    key: bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU=
+  outgoing_connection:
+    port: OUTGOING_PORT
+    delay: 1s

tests/integration/fixtures/api_reboot_timeout_after_authenticated_disconnect.yaml

@@ -0,0 +1,7 @@
+esphome:
+  name: api-reboot-test
+host:
+api:
+  reboot_timeout: 2s  # Headroom to connect and authenticate a client first
+logger:
+  level: DEBUG

tests/integration/test_api_outgoing_connection.py

@@ -0,0 +1,179 @@
+"""Integration tests for the api outgoing_connection option.
+
+The device dials out to the test's listener when no dial-back target client is
+connected. The listener plays the Home Assistant side over the accepted socket
+using aioesphomeapi's sans-IO Noise handshake: the device sends its server
+hello first so the listener could pick the right key, and the NNpsk0 handshake
+then verifies both sides. Protocol roles stay unchanged, so the client speaks
+exactly the same frames as over a normal connection. A client becomes the
+remembered dial-back target by setting the outgoing_connection_target flag in
+its hello.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import socket
+from typing import Any
+
+from aioesphomeapi import api_pb2
+import pytest
+
+from .raw_api_client import MESSAGE_TYPE_OF
+from .types import RunCompiledFunction
+
+KEY = "bOFFzzvfpg5DB94DuBGLXD/hMnhpDKgP9UQyBulwWVU="
+DEVICE_NAME = "outgoing-conn-test"
+HA_CLIENT_INFO = "Home Assistant 2026.8.0"
+# HelloRequest field 4 (outgoing_connection_target) as raw protobuf bytes; the
+# installed aioesphomeapi's api_pb2 predates the field, so append it manually.
+HELLO_TARGET_FLAG = b"\x20\x01"
+
+
+# Every run must start with no saved peer
+pytestmark = pytest.mark.usefixtures("isolated_preferences")
+
+
+def _frame(payload: bytes) -> bytes:
+    return bytes((0x01, len(payload) >> 8, len(payload) & 0xFF)) + payload
+
+
+async def _read_frame(reader: asyncio.StreamReader, timeout: float = 10.0) -> bytes:
+    header = await asyncio.wait_for(reader.readexactly(3), timeout)
+    assert header[0] == 0x01, f"Bad frame indicator: {header[0]}"
+    return await asyncio.wait_for(
+        reader.readexactly((header[1] << 8) | header[2]), timeout
+    )
+
+
+def _check_server_hello(server_hello: bytes) -> None:
+    assert server_hello[0] == 0x01, "Bad chosen proto in server hello"
+    name, mac, _rest = server_hello[1:].split(b"\x00", 2)
+    assert name.decode() == DEVICE_NAME
+    assert len(mac) == 12, f"Expected bare MAC, got {mac!r}"
+
+
+async def _run_ha_session(
+    reader: asyncio.StreamReader,
+    writer: asyncio.StreamWriter,
+    *,
+    device_dialed_out: bool,
+) -> None:
+    """Handshake and exchange the usual first messages as Home Assistant would."""
+    # Lazy import per the module's own contract (pulls in the noise stack)
+    from aioesphomeapi.noise import NoiseHandshake
+
+    if device_dialed_out:
+        # On an outgoing connection the device announces itself first so the
+        # peer can pick the matching key before its PSK-mixed first message.
+        _check_server_hello(await _read_frame(reader))
+
+    handshake = NoiseHandshake(KEY, b"NoiseAPIInit\x00\x00")
+    writer.write(b"\x01\x00\x00" + _frame(b"\x00" + handshake.write_message()))
+    await writer.drain()
+
+    if not device_dialed_out:
+        _check_server_hello(await _read_frame(reader))
+
+    reply = await _read_frame(reader)
+    assert reply[0] == 0, f"Handshake rejected: {reply[1:].decode(errors='replace')}"
+    handshake.read_message(reply[1:])
+    encrypt_cipher, decrypt_cipher = handshake.get_ciphers()
+
+    async def transact(msg: Any, response_cls: Any, extra_payload: bytes = b"") -> Any:
+        msg_type = MESSAGE_TYPE_OF[type(msg)]
+        payload = msg.SerializeToString() + extra_payload
+        plaintext = (
+            bytes(
+                (msg_type >> 8, msg_type & 0xFF, len(payload) >> 8, len(payload) & 0xFF)
+            )
+            + payload
+        )
+        writer.write(_frame(encrypt_cipher.encrypt(plaintext)))
+        await writer.drain()
+        want = MESSAGE_TYPE_OF[response_cls]
+        while True:
+            plain = decrypt_cipher.decrypt(await _read_frame(reader))
+            if ((plain[0] << 8) | plain[1]) == want:
+                response = response_cls()
+                response.ParseFromString(bytes(plain[4:]))
+                return response
+
+    # Declare this client a dial-back target in the hello
+    await transact(
+        api_pb2.HelloRequest(client_info=HA_CLIENT_INFO),
+        api_pb2.HelloResponse,
+        extra_payload=HELLO_TARGET_FLAG,
+    )
+    device_info = await transact(
+        api_pb2.DeviceInfoRequest(), api_pb2.DeviceInfoResponse
+    )
+    assert device_info.name == DEVICE_NAME
+
+
+async def _serve_home_assistant(listener: socket.socket) -> None:
+    """Accept one dial-in from the device and run the client side over it."""
+    loop = asyncio.get_running_loop()
+    conn, _ = await asyncio.wait_for(loop.sock_accept(listener), timeout=30)
+    reader, writer = await asyncio.open_connection(sock=conn)
+    try:
+        await _run_ha_session(reader, writer, device_dialed_out=True)
+    finally:
+        writer.close()
+
+
+@pytest.mark.asyncio
+async def test_api_outgoing_connection(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+) -> None:
+    """With a configured host the device dials out and speaks the normal API."""
+    listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    listener.bind(("127.0.0.1", 0))
+    listener.listen(2)
+    listener.setblocking(False)
+    port = listener.getsockname()[1]
+
+    try:
+        yaml = yaml_config.replace("OUTGOING_PORT", str(port))
+        async with run_compiled(yaml):
+            await _serve_home_assistant(listener)
+    finally:
+        listener.close()
+
+
+@pytest.mark.asyncio
+async def test_api_outgoing_connection_remembered(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    unused_tcp_port: int,
+) -> None:
+    """No host configured: the device remembers the client whose hello carried
+    the dial-back flag and dials that address after a restart."""
+    listener = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    # Bound but not yet listening so first-phase dials cannot queue stale
+    # connections; whether the device attempts any dial before the restart
+    # is timing dependent and not asserted here.
+    listener.bind(("127.0.0.1", 0))
+    port = listener.getsockname()[1]
+
+    try:
+        yaml = yaml_config.replace("OUTGOING_PORT", str(port))
+
+        async with run_compiled(yaml):
+            # Connect inbound with the dial-back flag; the device persists the
+            # peer address during the hello.
+            reader, writer = await asyncio.open_connection("127.0.0.1", unused_tcp_port)
+            try:
+                await _run_ha_session(reader, writer, device_dialed_out=False)
+            finally:
+                writer.close()
+
+        # Restart with the same preferences: the device now dials the
+        # remembered address on its own.
+        listener.listen(2)
+        listener.setblocking(False)
+        async with run_compiled(yaml):
+            await _serve_home_assistant(listener)
+    finally:
+        listener.close()

tests/integration/test_api_reboot_timeout.py

@@ -5,7 +5,7 @@ import re
 
 import pytest
 
-from .types import RunCompiledFunction
+from .types import APIClientConnectedFactory, RunCompiledFunction
 
 
 @pytest.mark.asyncio
@@ -16,7 +16,9 @@ async def test_api_reboot_timeout(
     """Test that the device reboots when no API clients connect within the timeout."""
     loop = asyncio.get_running_loop()
     reboot_future = loop.create_future()
-    reboot_pattern = re.compile(r"No clients; rebooting")
+    # The harness port probe always connects without authenticating, so the
+    # reboot deterministically reports the unauthenticated form
+    reboot_pattern = re.compile(r"none authenticated; rebooting")
 
     def check_output(line: str) -> None:
         """Check output for reboot message."""
@@ -33,3 +35,30 @@ async def test_api_reboot_timeout(
             pytest.fail("Device did not reboot within expected timeout")
 
     # Test passes if we get here - reboot was detected
+
+
+@pytest.mark.asyncio
+async def test_api_reboot_timeout_after_authenticated_disconnect(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """An authenticated disconnect resets the flag; the clean branch reboots."""
+    loop = asyncio.get_running_loop()
+    reboot_future = loop.create_future()
+    reboot_pattern = re.compile(r"No clients; rebooting")
+
+    def check_output(line: str) -> None:
+        """Check output for reboot message."""
+        if not reboot_future.done() and reboot_pattern.search(line):
+            reboot_future.set_result(True)
+
+    async with run_compiled(yaml_config, line_callback=check_output):
+        # An authenticated session refreshes the watchdog and clears the
+        # unauthenticated flag the harness probe set
+        async with api_client_connected() as client:
+            await client.device_info()
+        try:
+            await asyncio.wait_for(reboot_future, timeout=5.0)
+        except TimeoutError:
+            pytest.fail("Device did not reboot within expected timeout")

tests/integration/test_api_zero_psk_provisioning.py

@@ -24,10 +24,8 @@ NEW_KEY = base64.b64encode(b"n" * 32)
 KEY_ACTIVATION_DELAY = 0.5
 
 
-@pytest.fixture(autouse=True)
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
-    """Keep host preferences per-test so every run starts unprovisioned."""
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
+# Every run must start unprovisioned
+pytestmark = pytest.mark.usefixtures("isolated_preferences")
 
 
 @pytest.mark.asyncio

tests/integration/test_light_initial_state.py

@@ -10,13 +10,8 @@ import pytest
 from .state_utils import InitialStateHelper, require_entity
 from .types import APIClientConnectedFactory, RunCompiledFunction
 
-
-@pytest.fixture(autouse=True)
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
-    """Keep host preferences per-test so RESTORE_AND_ON never loads a stale value left
-    behind by a previous run (host preferences otherwise persist to ~/.esphome/prefs,
-    keyed only by device name)."""
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
+# RESTORE_AND_ON must never load a stale value left behind by a previous run
+pytestmark = pytest.mark.usefixtures("isolated_preferences")
 
 
 @pytest.mark.asyncio