[sntp] Merge multiple instances to fix crash and undefined behavior

.github/workflows/codeql.yml

@@ -58,7 +58,7 @@ jobs:
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@014f16e7ab1402f30e7c3329d33797e7948572db # v4.31.3
+        uses: github/codeql-action/init@0499de31b99561a6d14a36a5f662c2a54f91beee # v4.31.2
         with:
           languages: ${{ matrix.language }}
           build-mode: ${{ matrix.build-mode }}
@@ -86,6 +86,6 @@ jobs:
           exit 1
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@014f16e7ab1402f30e7c3329d33797e7948572db # v4.31.3
+        uses: github/codeql-action/analyze@0499de31b99561a6d14a36a5f662c2a54f91beee # v4.31.2
         with:
           category: "/language:${{matrix.language}}"

.pre-commit-config.yaml

@@ -11,7 +11,7 @@ ci:
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
     # Ruff version.
-    rev: v0.14.5
+    rev: v0.14.4
     hooks:
       # Run the linter.
       - id: ruff

esphome/components/logger/__init__.py

@@ -365,10 +365,8 @@ 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

@@ -65,9 +65,7 @@ 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);
-    // 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);
+    this->write_msg_(console_buffer);
   }
 
   // Reset the recursion guard for this task
@@ -133,19 +131,18 @@ 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
-  uint16_t msg_start = this->tx_buffer_at_;
+  uint32_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_);
 
-  uint16_t msg_length =
+  // 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 =
       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
@@ -212,7 +209,9 @@ 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
-      this->write_tx_buffer_to_console_();
+      if (this->baud_rate_ > 0) {
+        this->write_msg_(this->tx_buffer_);
+      }
     }
   } else {
     // No messages to process, disable loop if appropriate

esphome/components/logger/logger.h

@@ -71,17 +71,6 @@ 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)
-//        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)
-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
  *
@@ -184,7 +173,7 @@ class Logger : public Component {
 
  protected:
   void process_messages_();
-  void write_msg_(const char *msg, size_t len);
+  void write_msg_(const char *msg);
 
   // 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)
@@ -211,35 +200,6 @@ 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) {
@@ -248,11 +208,10 @@ 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_);
 
-    // Callbacks get message WITHOUT newline (for API/MQTT/syslog)
+    if (this->baud_rate_ > 0) {
+      this->write_msg_(this->tx_buffer_);  // If logging is enabled, write to console
+    }
     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
@@ -466,9 +425,7 @@ class Logger : public Component {
     }
 
     // Update buffer_at with the formatted length (handle truncation)
-    // 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;
+    uint16_t formatted_len = (ret >= remaining) ? remaining : ret;
     *buffer_at += formatted_len;
 
     // Remove all trailing newlines right after formatting

esphome/components/logger/logger_esp32.cpp

@@ -121,23 +121,25 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-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);
+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
 #else
-  // Regular UART - single write including newline (already in buffer)
-  uart_write_bytes(this->uart_num_, msg, len);
+      /* DISABLES CODE */ (false)  // NOLINT
 #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

@@ -33,10 +33,7 @@ void Logger::pre_setup() {
   ESP_LOGI(TAG, "Log initialized");
 }
 
-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);
-}
+void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
 
 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, size_t) {
+void HOT Logger::write_msg_(const char *msg) {
   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, size_t) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg) { this->hw_serial_->println(msg); }
 
 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, size_t) { this->hw_serial_->println(msg); }
+void HOT Logger::write_msg_(const char *msg) { 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, size_t) {
+void HOT Logger::write_msg_(const char *msg) {
 #ifdef CONFIG_PRINTK
   printk("%s\n", msg);
 #endif

esphome/components/sntp/time.py

@@ -1,9 +1,14 @@
+import logging
+
 import esphome.codegen as cg
 from esphome.components import time as time_
+from esphome.config_helpers import merge_config
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_ID,
+    CONF_PLATFORM,
     CONF_SERVERS,
+    CONF_TIME,
     PLATFORM_BK72XX,
     PLATFORM_ESP32,
     PLATFORM_ESP8266,
@@ -12,13 +17,74 @@ from esphome.const import (
     PLATFORM_RTL87XX,
 )
 from esphome.core import CORE
+import esphome.final_validate as fv
+from esphome.types import ConfigType
+
+_LOGGER = logging.getLogger(__name__)
 
 DEPENDENCIES = ["network"]
+
+CONF_SNTP = "sntp"
+
 sntp_ns = cg.esphome_ns.namespace("sntp")
 SNTPComponent = sntp_ns.class_("SNTPComponent", time_.RealTimeClock)
 
 DEFAULT_SERVERS = ["0.pool.ntp.org", "1.pool.ntp.org", "2.pool.ntp.org"]
 
+
+def _sntp_final_validate(config: ConfigType) -> None:
+    """Merge multiple SNTP instances into one, similar to OTA merging behavior."""
+    full_conf = fv.full_config.get()
+    time_confs = full_conf.get(CONF_TIME, [])
+
+    sntp_configs: list[ConfigType] = []
+    other_time_configs: list[ConfigType] = []
+
+    for time_conf in time_confs:
+        if time_conf.get(CONF_PLATFORM) == CONF_SNTP:
+            sntp_configs.append(time_conf)
+        else:
+            other_time_configs.append(time_conf)
+
+    if len(sntp_configs) <= 1:
+        return
+
+    # Merge all SNTP configs into the first one
+    merged = sntp_configs[0]
+    for sntp_conf in sntp_configs[1:]:
+        # Validate that IDs are consistent if manually specified
+        if merged[CONF_ID].is_manual and sntp_conf[CONF_ID].is_manual:
+            raise cv.Invalid(
+                f"Found multiple SNTP configurations but {CONF_ID} is inconsistent"
+            )
+        merged = merge_config(merged, sntp_conf)
+
+    # Deduplicate servers while preserving order
+    servers = merged[CONF_SERVERS]
+    unique_servers = list(dict.fromkeys(servers))
+
+    # Warn if we're dropping servers due to 3-server limit
+    if len(unique_servers) > 3:
+        dropped = unique_servers[3:]
+        unique_servers = unique_servers[:3]
+        _LOGGER.warning(
+            "SNTP supports maximum 3 servers. Dropped excess server(s): %s",
+            dropped,
+        )
+
+    merged[CONF_SERVERS] = unique_servers
+
+    _LOGGER.warning(
+        "Found and merged %d SNTP time configurations into one instance",
+        len(sntp_configs),
+    )
+
+    # Replace time configs with merged SNTP + other time platforms
+    other_time_configs.append(merged)
+    full_conf[CONF_TIME] = other_time_configs
+    fv.full_config.set(full_conf)
+
+
 CONFIG_SCHEMA = cv.All(
     time_.TIME_SCHEMA.extend(
         {
@@ -40,6 +106,8 @@ CONFIG_SCHEMA = cv.All(
     ),
 )
 
+FINAL_VALIDATE_SCHEMA = _sntp_final_validate
+
 
 async def to_code(config):
     servers = config[CONF_SERVERS]

esphome/components/uart/__init__.py

@@ -1,4 +1,3 @@
-from logging import getLogger
 import math
 import re
 
@@ -36,8 +35,6 @@ from esphome.core import CORE, ID
 import esphome.final_validate as fv
 from esphome.yaml_util import make_data_base
 
-_LOGGER = getLogger(__name__)
-
 CODEOWNERS = ["@esphome/core"]
 uart_ns = cg.esphome_ns.namespace("uart")
 UARTComponent = uart_ns.class_("UARTComponent")
@@ -133,21 +130,6 @@ def validate_host_config(config):
     return config
 
 
-def validate_rx_buffer_size(config):
-    if CORE.is_esp32:
-        # ESP32 UART hardware FIFO is 128 bytes (LP UART is 16 bytes, but we use 128 as safe minimum)
-        # rx_buffer_size must be greater than the hardware FIFO length
-        min_buffer_size = 128
-        if config[CONF_RX_BUFFER_SIZE] <= min_buffer_size:
-            _LOGGER.warning(
-                "UART rx_buffer_size (%d bytes) is too small and must be greater than the hardware "
-                "FIFO size (%d bytes). The buffer size will be automatically adjusted at runtime.",
-                config[CONF_RX_BUFFER_SIZE],
-                min_buffer_size,
-            )
-    return config
-
-
 def _uart_declare_type(value):
     if CORE.is_esp8266:
         return cv.declare_id(ESP8266UartComponent)(value)
@@ -265,7 +247,6 @@ CONFIG_SCHEMA = cv.All(
     ).extend(cv.COMPONENT_SCHEMA),
     cv.has_at_least_one_key(CONF_TX_PIN, CONF_RX_PIN, CONF_PORT),
     validate_host_config,
-    validate_rx_buffer_size,
 )
 
 

esphome/components/uart/uart_component_esp_idf.cpp

@@ -91,16 +91,6 @@ void IDFUARTComponent::setup() {
   this->uart_num_ = static_cast<uart_port_t>(next_uart_num++);
   this->lock_ = xSemaphoreCreateMutex();
 
-#if (SOC_UART_LP_NUM >= 1)
-  size_t fifo_len = ((this->uart_num_ < SOC_UART_HP_NUM) ? SOC_UART_FIFO_LEN : SOC_LP_UART_FIFO_LEN);
-#else
-  size_t fifo_len = SOC_UART_FIFO_LEN;
-#endif
-  if (this->rx_buffer_size_ <= fifo_len) {
-    ESP_LOGW(TAG, "rx_buffer_size is too small, must be greater than %zu", fifo_len);
-    this->rx_buffer_size_ = fifo_len * 2;
-  }
-
   xSemaphoreTake(this->lock_, portMAX_DELAY);
 
   this->load_settings(false);
@@ -247,12 +237,8 @@ void IDFUARTComponent::set_rx_timeout(size_t rx_timeout) {
 
 void IDFUARTComponent::write_array(const uint8_t *data, size_t len) {
   xSemaphoreTake(this->lock_, portMAX_DELAY);
-  int32_t write_len = uart_write_bytes(this->uart_num_, data, len);
+  uart_write_bytes(this->uart_num_, data, len);
   xSemaphoreGive(this->lock_);
-  if (write_len != (int32_t) len) {
-    ESP_LOGW(TAG, "uart_write_bytes failed: %d != %zu", write_len, len);
-    this->mark_failed();
-  }
 #ifdef USE_UART_DEBUGGER
   for (size_t i = 0; i < len; i++) {
     this->debug_callback_.call(UART_DIRECTION_TX, data[i]);
@@ -281,7 +267,6 @@ bool IDFUARTComponent::peek_byte(uint8_t *data) {
 
 bool IDFUARTComponent::read_array(uint8_t *data, size_t len) {
   size_t length_to_read = len;
-  int32_t read_len = 0;
   if (!this->check_read_timeout_(len))
     return false;
   xSemaphoreTake(this->lock_, portMAX_DELAY);
@@ -292,31 +277,25 @@ bool IDFUARTComponent::read_array(uint8_t *data, size_t len) {
     this->has_peek_ = false;
   }
   if (length_to_read > 0)
-    read_len = uart_read_bytes(this->uart_num_, data, length_to_read, 20 / portTICK_PERIOD_MS);
+    uart_read_bytes(this->uart_num_, data, length_to_read, 20 / portTICK_PERIOD_MS);
   xSemaphoreGive(this->lock_);
 #ifdef USE_UART_DEBUGGER
   for (size_t i = 0; i < len; i++) {
     this->debug_callback_.call(UART_DIRECTION_RX, data[i]);
   }
 #endif
-  return read_len == (int32_t) length_to_read;
+  return true;
 }
 
 int IDFUARTComponent::available() {
-  size_t available = 0;
-  esp_err_t err;
+  size_t available;
 
   xSemaphoreTake(this->lock_, portMAX_DELAY);
-  err = uart_get_buffered_data_len(this->uart_num_, &available);
+  uart_get_buffered_data_len(this->uart_num_, &available);
+  if (this->has_peek_)
+    available++;
   xSemaphoreGive(this->lock_);
 
-  if (err != ESP_OK) {
-    ESP_LOGW(TAG, "uart_get_buffered_data_len failed: %s", esp_err_to_name(err));
-    this->mark_failed();
-  }
-  if (this->has_peek_) {
-    available++;
-  }
   return available;
 }
 

esphome/components/wifi/__init__.py

@@ -12,6 +12,7 @@ from esphome.components.network import (
 from esphome.components.psram import is_guaranteed as psram_is_guaranteed
 from esphome.config_helpers import filter_source_files_from_platform
 import esphome.config_validation as cv
+from esphome.config_validation import only_with_esp_idf
 from esphome.const import (
     CONF_AP,
     CONF_BSSID,
@@ -351,7 +352,7 @@ CONFIG_SCHEMA = cv.All(
                 single=True
             ),
             cv.Optional(CONF_USE_PSRAM): cv.All(
-                cv.only_on_esp32, cv.requires_component("psram"), cv.boolean
+                only_with_esp_idf, cv.requires_component("psram"), cv.boolean
             ),
         }
     ),

requirements_test.txt

@@ -1,6 +1,6 @@
 pylint==4.0.3
 flake8==7.3.0  # also change in .pre-commit-config.yaml when updating
-ruff==0.14.5  # also change in .pre-commit-config.yaml when updating
+ruff==0.14.4  # also change in .pre-commit-config.yaml when updating
 pyupgrade==3.21.1  # also change in .pre-commit-config.yaml when updating
 pre-commit
 

tests/component_tests/sntp/__init__.py

@@ -0,0 +1 @@
+"""Tests for SNTP component."""

tests/component_tests/sntp/config/sntp_test.yaml

@@ -0,0 +1,22 @@
+esphome:
+  name: sntp-test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: "testssid"
+  password: "testpassword"
+
+# Test multiple SNTP instances that should be merged
+time:
+  - platform: sntp
+    servers:
+      - 192.168.1.1
+      - pool.ntp.org
+  - platform: sntp
+    servers:
+      - pool.ntp.org
+      - 192.168.1.2

tests/component_tests/sntp/test_init.py

@@ -0,0 +1,238 @@
+"""Tests for SNTP time configuration validation."""
+
+from __future__ import annotations
+
+import logging
+from typing import Any
+
+import pytest
+
+from esphome import config_validation as cv
+from esphome.components.sntp.time import CONF_SNTP, _sntp_final_validate
+from esphome.const import CONF_ID, CONF_PLATFORM, CONF_SERVERS, CONF_TIME
+from esphome.core import ID
+import esphome.final_validate as fv
+
+
+@pytest.mark.parametrize(
+    ("time_configs", "expected_count", "expected_servers", "warning_messages"),
+    [
+        pytest.param(
+            [
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.1", "pool.ntp.org"],
+                }
+            ],
+            1,
+            ["192.168.1.1", "pool.ntp.org"],
+            [],
+            id="single_instance_no_merge",
+        ),
+        pytest.param(
+            [
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_1", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.1", "pool.ntp.org"],
+                },
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_2", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.2"],
+                },
+            ],
+            1,
+            ["192.168.1.1", "pool.ntp.org", "192.168.1.2"],
+            ["Found and merged 2 SNTP time configurations into one instance"],
+            id="two_instances_merged",
+        ),
+        pytest.param(
+            [
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_1", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.1", "pool.ntp.org"],
+                },
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_2", is_manual=False),
+                    CONF_SERVERS: ["pool.ntp.org", "192.168.1.2"],
+                },
+            ],
+            1,
+            ["192.168.1.1", "pool.ntp.org", "192.168.1.2"],
+            ["Found and merged 2 SNTP time configurations into one instance"],
+            id="deduplication_preserves_order",
+        ),
+        pytest.param(
+            [
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_1", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.1", "pool.ntp.org"],
+                },
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_2", is_manual=False),
+                    CONF_SERVERS: ["192.168.1.2", "pool2.ntp.org"],
+                },
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_3", is_manual=False),
+                    CONF_SERVERS: ["pool3.ntp.org"],
+                },
+            ],
+            1,
+            ["192.168.1.1", "pool.ntp.org", "192.168.1.2"],
+            [
+                "SNTP supports maximum 3 servers. Dropped excess server(s): ['pool2.ntp.org', 'pool3.ntp.org']",
+                "Found and merged 3 SNTP time configurations into one instance",
+            ],
+            id="three_instances_drops_excess_servers",
+        ),
+        pytest.param(
+            [
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_1", is_manual=False),
+                    CONF_SERVERS: [
+                        "192.168.1.1",
+                        "pool.ntp.org",
+                        "pool.ntp.org",
+                        "192.168.1.1",
+                    ],
+                },
+                {
+                    CONF_PLATFORM: CONF_SNTP,
+                    CONF_ID: ID("sntp_time_2", is_manual=False),
+                    CONF_SERVERS: ["pool.ntp.org", "192.168.1.2"],
+                },
+            ],
+            1,
+            ["192.168.1.1", "pool.ntp.org", "192.168.1.2"],
+            ["Found and merged 2 SNTP time configurations into one instance"],
+            id="deduplication_multiple_duplicates",
+        ),
+    ],
+)
+def test_sntp_instance_merging(
+    time_configs: list[dict[str, Any]],
+    expected_count: int,
+    expected_servers: list[str],
+    warning_messages: list[str],
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test SNTP instance merging behavior."""
+    # Create a mock full config with time configs
+    full_conf = {CONF_TIME: time_configs.copy()}
+
+    # Set the context var
+    token = fv.full_config.set(full_conf)
+    try:
+        with caplog.at_level(logging.WARNING):
+            _sntp_final_validate({})
+
+        # Get the updated config
+        updated_conf = fv.full_config.get()
+
+        # Check if merging occurred
+        if len(time_configs) > 1:
+            # Verify only one SNTP instance remains
+            sntp_instances = [
+                tc
+                for tc in updated_conf[CONF_TIME]
+                if tc.get(CONF_PLATFORM) == CONF_SNTP
+            ]
+            assert len(sntp_instances) == expected_count
+
+            # Verify server list
+            assert sntp_instances[0][CONF_SERVERS] == expected_servers
+
+            # Verify warnings
+            for expected_msg in warning_messages:
+                assert any(
+                    expected_msg in record.message for record in caplog.records
+                ), f"Expected warning message '{expected_msg}' not found in log"
+        else:
+            # Single instance should not trigger merging or warnings
+            assert len(caplog.records) == 0
+            # Config should be unchanged
+            assert updated_conf[CONF_TIME] == time_configs
+    finally:
+        fv.full_config.reset(token)
+
+
+def test_sntp_inconsistent_manual_ids() -> None:
+    """Test that inconsistent manual IDs raise an error."""
+    # Create configs with manual IDs that are inconsistent
+    time_configs = [
+        {
+            CONF_PLATFORM: CONF_SNTP,
+            CONF_ID: ID("sntp_time_1", is_manual=True),
+            CONF_SERVERS: ["192.168.1.1"],
+        },
+        {
+            CONF_PLATFORM: CONF_SNTP,
+            CONF_ID: ID("sntp_time_2", is_manual=True),
+            CONF_SERVERS: ["192.168.1.2"],
+        },
+    ]
+
+    full_conf = {CONF_TIME: time_configs}
+
+    token = fv.full_config.set(full_conf)
+    try:
+        with pytest.raises(
+            cv.Invalid,
+            match="Found multiple SNTP configurations but id is inconsistent",
+        ):
+            _sntp_final_validate({})
+    finally:
+        fv.full_config.reset(token)
+
+
+def test_sntp_with_other_time_platforms(caplog: pytest.LogCaptureFixture) -> None:
+    """Test that SNTP merging doesn't affect other time platforms."""
+    time_configs = [
+        {
+            CONF_PLATFORM: CONF_SNTP,
+            CONF_ID: ID("sntp_time_1", is_manual=False),
+            CONF_SERVERS: ["192.168.1.1"],
+        },
+        {
+            CONF_PLATFORM: "homeassistant",
+            CONF_ID: ID("homeassistant_time", is_manual=False),
+        },
+        {
+            CONF_PLATFORM: CONF_SNTP,
+            CONF_ID: ID("sntp_time_2", is_manual=False),
+            CONF_SERVERS: ["192.168.1.2"],
+        },
+    ]
+
+    full_conf = {CONF_TIME: time_configs.copy()}
+
+    token = fv.full_config.set(full_conf)
+    try:
+        with caplog.at_level(logging.WARNING):
+            _sntp_final_validate({})
+
+        updated_conf = fv.full_config.get()
+
+        # Should have 2 time platforms: 1 merged SNTP + 1 homeassistant
+        assert len(updated_conf[CONF_TIME]) == 2
+
+        # Find the platforms
+        platforms = {tc[CONF_PLATFORM] for tc in updated_conf[CONF_TIME]}
+        assert platforms == {CONF_SNTP, "homeassistant"}
+
+        # Verify SNTP was merged
+        sntp_instances = [
+            tc for tc in updated_conf[CONF_TIME] if tc[CONF_PLATFORM] == CONF_SNTP
+        ]
+        assert len(sntp_instances) == 1
+        assert sntp_instances[0][CONF_SERVERS] == ["192.168.1.1", "192.168.1.2"]
+    finally:
+        fv.full_config.reset(token)