[logger] Eliminate strlen overhead on LibreTiny

esphome/components/api/user_services.h

@@ -51,14 +51,13 @@ template<typename... Ts> class UserServiceBase : public UserServiceDescriptor {
       return false;
     if (req.args.size() != sizeof...(Ts))
       return false;
-    this->execute_(req.args, std::make_index_sequence<sizeof...(Ts)>{});
+    this->execute_(req.args, typename gens<sizeof...(Ts)>::type());
     return true;
   }
 
  protected:
   virtual void execute(Ts... x) = 0;
-  template<typename ArgsContainer, size_t... S>
-  void execute_(const ArgsContainer &args, std::index_sequence<S...> type) {
+  template<typename ArgsContainer, int... S> void execute_(const ArgsContainer &args, seq<S...> type) {
     this->execute((get_execute_arg_value<Ts>(args[S]))...);
   }
 
@@ -96,14 +95,13 @@ template<typename... Ts> class UserServiceDynamic : public UserServiceDescriptor
       return false;
     if (req.args.size() != sizeof...(Ts))
       return false;
-    this->execute_(req.args, std::make_index_sequence<sizeof...(Ts)>{});
+    this->execute_(req.args, typename gens<sizeof...(Ts)>::type());
     return true;
   }
 
  protected:
   virtual void execute(Ts... x) = 0;
-  template<typename ArgsContainer, size_t... S>
-  void execute_(const ArgsContainer &args, std::index_sequence<S...> type) {
+  template<typename ArgsContainer, int... S> void execute_(const ArgsContainer &args, seq<S...> type) {
     this->execute((get_execute_arg_value<Ts>(args[S]))...);
   }
 

esphome/components/logger/__init__.py

@@ -365,8 +365,10 @@ async def to_code(config):
     if CORE.is_esp32:
         if config[CONF_HARDWARE_UART] == USB_CDC:
             add_idf_sdkconfig_option("CONFIG_ESP_CONSOLE_USB_CDC", True)
+            cg.add_define("USE_LOGGER_UART_SELECTION_USB_CDC")
         elif config[CONF_HARDWARE_UART] == USB_SERIAL_JTAG:
             add_idf_sdkconfig_option("CONFIG_ESP_CONSOLE_USB_SERIAL_JTAG", True)
+            cg.add_define("USE_LOGGER_UART_SELECTION_USB_SERIAL_JTAG")
     try:
         uart_selection(USB_SERIAL_JTAG)
         cg.add_define("USE_LOGGER_USB_SERIAL_JTAG")

esphome/components/logger/logger.cpp

@@ -65,7 +65,9 @@ void HOT Logger::log_vprintf_(uint8_t level, const char *tag, int line, const ch
     uint16_t buffer_at = 0;                         // Initialize buffer position
     this->format_log_to_buffer_with_terminator_(level, tag, line, format, args, console_buffer, &buffer_at,
                                                 MAX_CONSOLE_LOG_MSG_SIZE);
-    this->write_msg_(console_buffer);
+    // Add newline if platform needs it (ESP32 doesn't add via write_msg_)
+    this->add_newline_to_buffer_if_needed_(console_buffer, &buffer_at, MAX_CONSOLE_LOG_MSG_SIZE);
+    this->write_msg_(console_buffer, buffer_at);
   }
 
   // Reset the recursion guard for this task
@@ -131,18 +133,19 @@ void Logger::log_vprintf_(uint8_t level, const char *tag, int line, const __Flas
 
   // Save the offset before calling format_log_to_buffer_with_terminator_
   // since it will increment tx_buffer_at_ to the end of the formatted string
-  uint32_t msg_start = this->tx_buffer_at_;
+  uint16_t msg_start = this->tx_buffer_at_;
   this->format_log_to_buffer_with_terminator_(level, tag, line, this->tx_buffer_, args, this->tx_buffer_,
                                               &this->tx_buffer_at_, this->tx_buffer_size_);
 
-  // Write to console and send callback starting at the msg_start
-  if (this->baud_rate_ > 0) {
-    this->write_msg_(this->tx_buffer_ + msg_start);
-  }
-  size_t msg_length =
+  uint16_t msg_length =
       this->tx_buffer_at_ - msg_start;  // Don't subtract 1 - tx_buffer_at_ is already at the null terminator position
+
+  // Callbacks get message first (before console write)
   this->log_callback_.call(level, tag, this->tx_buffer_ + msg_start, msg_length);
 
+  // Write to console starting at the msg_start
+  this->write_tx_buffer_to_console_(msg_start, &msg_length);
+
   global_recursion_guard_ = false;
 }
 #endif  // USE_STORE_LOG_STR_IN_FLASH
@@ -209,9 +212,7 @@ void Logger::process_messages_() {
       // This ensures all log messages appear on the console in a clean, serialized manner
       // Note: Messages may appear slightly out of order due to async processing, but
       // this is preferred over corrupted/interleaved console output
-      if (this->baud_rate_ > 0) {
-        this->write_msg_(this->tx_buffer_);
-      }
+      this->write_tx_buffer_to_console_();
     }
   } else {
     // No messages to process, disable loop if appropriate

esphome/components/logger/logger.h

@@ -71,6 +71,17 @@ static constexpr uint16_t MAX_HEADER_SIZE = 128;
 // "0x" + 2 hex digits per byte + '\0'
 static constexpr size_t MAX_POINTER_REPRESENTATION = 2 + sizeof(void *) * 2 + 1;
 
+// Platform-specific: does write_msg_ add its own newline?
+// false: Caller must add newline to buffer before calling write_msg_ (ESP32, ESP8266, LibreTiny)
+//        Allows single write call with newline included for efficiency
+// true:  write_msg_ adds newline itself via puts()/println() (other platforms)
+//        Newline should NOT be added to buffer
+#if defined(USE_ESP32) || defined(USE_ESP8266) || defined(USE_LIBRETINY)
+static constexpr bool WRITE_MSG_ADDS_NEWLINE = false;
+#else
+static constexpr bool WRITE_MSG_ADDS_NEWLINE = true;
+#endif
+
 #if defined(USE_ESP32) || defined(USE_ESP8266) || defined(USE_RP2040) || defined(USE_LIBRETINY) || defined(USE_ZEPHYR)
 /** Enum for logging UART selection
  *
@@ -173,7 +184,7 @@ class Logger : public Component {
 
  protected:
   void process_messages_();
-  void write_msg_(const char *msg);
+  void write_msg_(const char *msg, size_t len);
 
   // Format a log message with printf-style arguments and write it to a buffer with header, footer, and null terminator
   // It's the caller's responsibility to initialize buffer_at (typically to 0)
@@ -200,6 +211,35 @@ class Logger : public Component {
     }
   }
 
+  // Helper to add newline to buffer for platforms that need it
+  // Modifies buffer_at to include the newline
+  inline void HOT add_newline_to_buffer_if_needed_(char *buffer, uint16_t *buffer_at, uint16_t buffer_size) {
+    if constexpr (!WRITE_MSG_ADDS_NEWLINE) {
+      // Add newline - don't need to maintain null termination
+      // write_msg_ now always receives explicit length, so we can safely overwrite the null terminator
+      // This is safe because:
+      // 1. Callbacks already received the message (before we add newline)
+      // 2. write_msg_ receives the length explicitly (doesn't need null terminator)
+      if (*buffer_at < buffer_size) {
+        buffer[(*buffer_at)++] = '\n';
+      } else if (buffer_size > 0) {
+        // Buffer was full - replace last char with newline to ensure it's visible
+        buffer[buffer_size - 1] = '\n';
+        *buffer_at = buffer_size;
+      }
+    }
+  }
+
+  // Helper to write tx_buffer_ to console if logging is enabled
+  // INTERNAL USE ONLY - offset > 0 requires length parameter to be non-null
+  inline void HOT write_tx_buffer_to_console_(uint16_t offset = 0, uint16_t *length = nullptr) {
+    if (this->baud_rate_ > 0) {
+      uint16_t *len_ptr = length ? length : &this->tx_buffer_at_;
+      this->add_newline_to_buffer_if_needed_(this->tx_buffer_ + offset, len_ptr, this->tx_buffer_size_ - offset);
+      this->write_msg_(this->tx_buffer_ + offset, *len_ptr);
+    }
+  }
+
   // Helper to format and send a log message to both console and callbacks
   inline void HOT log_message_to_buffer_and_send_(uint8_t level, const char *tag, int line, const char *format,
                                                   va_list args) {
@@ -208,10 +248,11 @@ class Logger : public Component {
     this->format_log_to_buffer_with_terminator_(level, tag, line, format, args, this->tx_buffer_, &this->tx_buffer_at_,
                                                 this->tx_buffer_size_);
 
-    if (this->baud_rate_ > 0) {
-      this->write_msg_(this->tx_buffer_);  // If logging is enabled, write to console
-    }
+    // Callbacks get message WITHOUT newline (for API/MQTT/syslog)
     this->log_callback_.call(level, tag, this->tx_buffer_, this->tx_buffer_at_);
+
+    // Console gets message WITH newline (if platform needs it)
+    this->write_tx_buffer_to_console_();
   }
 
   // Write the body of the log message to the buffer
@@ -425,7 +466,9 @@ class Logger : public Component {
     }
 
     // Update buffer_at with the formatted length (handle truncation)
-    uint16_t formatted_len = (ret >= remaining) ? remaining : ret;
+    // When vsnprintf truncates (ret >= remaining), it writes (remaining - 1) chars + null terminator
+    // When it doesn't truncate (ret < remaining), it writes ret chars + null terminator
+    uint16_t formatted_len = (ret >= remaining) ? (remaining - 1) : ret;
     *buffer_at += formatted_len;
 
     // Remove all trailing newlines right after formatting

esphome/components/logger/logger_esp32.cpp

@@ -121,25 +121,23 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) {
-  if (
-#if defined(USE_LOGGER_USB_CDC) && !defined(USE_LOGGER_USB_SERIAL_JTAG)
-      this->uart_ == UART_SELECTION_USB_CDC
-#elif defined(USE_LOGGER_USB_SERIAL_JTAG) && !defined(USE_LOGGER_USB_CDC)
-      this->uart_ == UART_SELECTION_USB_SERIAL_JTAG
-#elif defined(USE_LOGGER_USB_CDC) && defined(USE_LOGGER_USB_SERIAL_JTAG)
-      this->uart_ == UART_SELECTION_USB_CDC || this->uart_ == UART_SELECTION_USB_SERIAL_JTAG
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Length is now always passed explicitly - no strlen() fallback needed
+
+#if defined(USE_LOGGER_UART_SELECTION_USB_CDC) || defined(USE_LOGGER_UART_SELECTION_USB_SERIAL_JTAG)
+  // USB CDC/JTAG - single write including newline (already in buffer)
+  // Use fwrite to stdout which goes through VFS to USB console
+  //
+  // Note: These defines indicate the user's YAML configuration choice (hardware_uart: USB_CDC/USB_SERIAL_JTAG).
+  // They are ONLY defined when the user explicitly selects USB as the logger output in their config.
+  // This is compile-time selection, not runtime detection - if USB is configured, it's always used.
+  // There is no fallback to regular UART if "USB isn't connected" - that's the user's responsibility
+  // to configure correctly for their hardware. This approach eliminates runtime overhead.
+  fwrite(msg, 1, len, stdout);
 #else
-      /* DISABLES CODE */ (false)  // NOLINT
+  // Regular UART - single write including newline (already in buffer)
+  uart_write_bytes(this->uart_num_, msg, len);
 #endif
-  ) {
-    puts(msg);
-  } else {
-    // Use tx_buffer_at_ if msg points to tx_buffer_, otherwise fall back to strlen
-    size_t len = (msg == this->tx_buffer_) ? this->tx_buffer_at_ : strlen(msg);
-    uart_write_bytes(this->uart_num_, msg, len);
-    uart_write_bytes(this->uart_num_, "\n", 1);
-  }
 }
 
 const LogString *Logger::get_uart_selection_() {

esphome/components/logger/logger_esp8266.cpp

@@ -33,7 +33,10 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) {
+  // Single write with newline already in buffer (added by caller)
+  this->hw_serial_->write(msg, len);
+}
 
 const LogString *Logger::get_uart_selection_() {
   switch (this->uart_) {

esphome/components/logger/logger_host.cpp

@@ -3,7 +3,7 @@
 
 namespace esphome::logger {
 
-void HOT Logger::write_msg_(const char *msg) {
+void HOT Logger::write_msg_(const char *msg, size_t) {
   time_t rawtime;
   struct tm *timeinfo;
   char buffer[80];

esphome/components/logger/logger_libretiny.cpp

@@ -49,7 +49,7 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t len) { this->hw_serial_->write(msg, len); }
 
 const LogString *Logger::get_uart_selection_() {
   switch (this->uart_) {

esphome/components/logger/logger_rp2040.cpp

@@ -27,7 +27,7 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg, size_t) { this->hw_serial_->println(msg); }
 
 const LogString *Logger::get_uart_selection_() {
   switch (this->uart_) {

esphome/components/logger/logger_zephyr.cpp

@@ -62,7 +62,7 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-void HOT Logger::write_msg_(const char *msg) {
+void HOT Logger::write_msg_(const char *msg, size_t) {
 #ifdef CONFIG_PRINTK
   printk("%s\n", msg);
 #endif

esphome/components/script/script.h

@@ -46,14 +46,14 @@ template<typename... Ts> class Script : public ScriptLogger, public Trigger<Ts..
 
   // execute this script using a tuple that contains the arguments
   void execute_tuple(const std::tuple<Ts...> &tuple) {
-    this->execute_tuple_(tuple, std::make_index_sequence<sizeof...(Ts)>{});
+    this->execute_tuple_(tuple, typename gens<sizeof...(Ts)>::type());
   }
 
   // Internal function to give scripts readable names.
   void set_name(const LogString *name) { name_ = name; }
 
  protected:
-  template<size_t... S> void execute_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> void execute_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     this->execute(std::get<S>(tuple)...);
   }
 
@@ -157,7 +157,7 @@ template<typename... Ts> class QueueingScript : public Script<Ts...>, public Com
       const size_t queue_capacity = static_cast<size_t>(this->max_runs_ - 1);
       auto tuple_ptr = std::move(this->var_queue_[this->queue_front_]);
       this->queue_front_ = (this->queue_front_ + 1) % queue_capacity;
-      this->trigger_tuple_(*tuple_ptr, std::make_index_sequence<sizeof...(Ts)>{});
+      this->trigger_tuple_(*tuple_ptr, typename gens<sizeof...(Ts)>::type());
     }
   }
 
@@ -174,7 +174,7 @@ template<typename... Ts> class QueueingScript : public Script<Ts...>, public Com
     }
   }
 
-  template<size_t... S> void trigger_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> void trigger_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     this->trigger(std::get<S>(tuple)...);
   }
 
@@ -305,7 +305,7 @@ template<class C, typename... Ts> class ScriptWaitAction : public Action<Ts...>,
 
     while (!this->param_queue_.empty()) {
       auto &params = this->param_queue_.front();
-      this->play_next_tuple_(params, std::make_index_sequence<sizeof...(Ts)>{});
+      this->play_next_tuple_(params, typename gens<sizeof...(Ts)>::type());
       this->param_queue_.pop_front();
     }
     // Queue is now empty - disable loop until next play_complex
@@ -321,7 +321,7 @@ template<class C, typename... Ts> class ScriptWaitAction : public Action<Ts...>,
   }
 
  protected:
-  template<size_t... S> void play_next_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> void play_next_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     this->play_next_(std::get<S>(tuple)...);
   }
 

esphome/core/automation.h

@@ -11,26 +11,10 @@
 
 namespace esphome {
 
-// C++20 std::index_sequence is now used for tuple unpacking
-// Legacy seq<>/gens<> pattern deprecated but kept for backwards compatibility
 // https://stackoverflow.com/questions/7858817/unpacking-a-tuple-to-call-a-matching-function-pointer/7858971#7858971
-// Remove before 2026.6.0
-// NOLINTBEGIN(readability-identifier-naming)
-#if defined(__GNUC__) || defined(__clang__)
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#endif
-
-template<int...> struct ESPDEPRECATED("Use std::index_sequence instead. Removed in 2026.6.0", "2025.12.0") seq {};
-template<int N, int... S>
-struct ESPDEPRECATED("Use std::make_index_sequence instead. Removed in 2026.6.0", "2025.12.0") gens
-    : gens<N - 1, N - 1, S...> {};
-template<int... S> struct gens<0, S...> { using type = seq<S...>; };
-
-#if defined(__GNUC__) || defined(__clang__)
-#pragma GCC diagnostic pop
-#endif
-// NOLINTEND(readability-identifier-naming)
+template<int...> struct seq {};                                       // NOLINT
+template<int N, int... S> struct gens : gens<N - 1, N - 1, S...> {};  // NOLINT
+template<int... S> struct gens<0, S...> { using type = seq<S...>; };  // NOLINT
 
 #define TEMPLATABLE_VALUE_(type, name) \
  protected: \
@@ -168,11 +152,11 @@ template<typename... Ts> class Condition {
 
   /// Call check with a tuple of values as parameter.
   bool check_tuple(const std::tuple<Ts...> &tuple) {
-    return this->check_tuple_(tuple, std::make_index_sequence<sizeof...(Ts)>{});
+    return this->check_tuple_(tuple, typename gens<sizeof...(Ts)>::type());
   }
 
  protected:
-  template<size_t... S> bool check_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> bool check_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     return this->check(std::get<S>(tuple)...);
   }
 };
@@ -247,11 +231,11 @@ template<typename... Ts> class Action {
       }
     }
   }
-  template<size_t... S> void play_next_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> void play_next_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     this->play_next_(std::get<S>(tuple)...);
   }
   void play_next_tuple_(const std::tuple<Ts...> &tuple) {
-    this->play_next_tuple_(tuple, std::make_index_sequence<sizeof...(Ts)>{});
+    this->play_next_tuple_(tuple, typename gens<sizeof...(Ts)>::type());
   }
 
   virtual void stop() {}
@@ -293,9 +277,7 @@ template<typename... Ts> class ActionList {
     if (this->actions_begin_ != nullptr)
       this->actions_begin_->play_complex(x...);
   }
-  void play_tuple(const std::tuple<Ts...> &tuple) {
-    this->play_tuple_(tuple, std::make_index_sequence<sizeof...(Ts)>{});
-  }
+  void play_tuple(const std::tuple<Ts...> &tuple) { this->play_tuple_(tuple, typename gens<sizeof...(Ts)>::type()); }
   void stop() {
     if (this->actions_begin_ != nullptr)
       this->actions_begin_->stop_complex();
@@ -316,7 +298,7 @@ template<typename... Ts> class ActionList {
   }
 
  protected:
-  template<size_t... S> void play_tuple_(const std::tuple<Ts...> &tuple, std::index_sequence<S...> /*unused*/) {
+  template<int... S> void play_tuple_(const std::tuple<Ts...> &tuple, seq<S...> /*unused*/) {
     this->play(std::get<S>(tuple)...);
   }