diff --git a/esphome/components/mdns/mdns_component.cpp b/esphome/components/mdns/mdns_component.cpp
index cdd24015f5..9bf27e71e4 100644
--- a/esphome/components/mdns/mdns_component.cpp
+++ b/esphome/components/mdns/mdns_component.cpp
@@ -39,6 +39,37 @@ MDNS_STATIC_CONST_CHAR(SERVICE_TCP, "_tcp");
 // Wrap build-time defines into flash storage
 MDNS_STATIC_CONST_CHAR(VALUE_VERSION, ESPHOME_VERSION);
 
+void MDNSComponent::setup_buffers_and_register_(PlatformRegisterFn platform_register) {
+#ifdef USE_MDNS_STORE_SERVICES
+  auto &services = this->services_;
+#else
+  StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_storage;
+  auto &services = services_storage;
+#endif
+
+#ifdef USE_API
+#ifdef USE_MDNS_STORE_SERVICES
+  get_mac_address_into_buffer(this->mac_address_);
+  char *mac_ptr = this->mac_address_;
+  format_hex_to(this->config_hash_str_, App.get_config_hash());
+  char *cfg_ptr = this->config_hash_str_;
+#else
+  char mac_address[MAC_ADDRESS_BUFFER_SIZE];
+  char config_hash_str[CONFIG_HASH_STR_SIZE];
+  get_mac_address_into_buffer(mac_address);
+  format_hex_to(config_hash_str, App.get_config_hash());
+  char *mac_ptr = mac_address;
+  char *cfg_ptr = config_hash_str;
+#endif
+#else
+  char *mac_ptr = nullptr;
+  char *cfg_ptr = nullptr;
+#endif
+
+  this->compile_records_(services, mac_ptr, cfg_ptr);
+  platform_register(this, services);
+}
+
 void MDNSComponent::compile_records_(StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services, char *mac_address_buf,
                                      char *config_hash_buf) {
   // IMPORTANT: The #ifdef blocks below must match COMPONENTS_WITH_MDNS_SERVICES
diff --git a/esphome/components/mdns/mdns_component.h b/esphome/components/mdns/mdns_component.h
index a4aedab5fe..e981a65941 100644
--- a/esphome/components/mdns/mdns_component.h
+++ b/esphome/components/mdns/mdns_component.h
@@ -1,10 +1,7 @@
 #pragma once
 #include "esphome/core/defines.h"
 #ifdef USE_MDNS
-#include <cinttypes>
-#include <cstdio>
 #include <string>
-#include "esphome/core/application.h"
 #include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/helpers.h"
@@ -74,7 +71,7 @@ class MDNSComponent final : public Component
   void dump_config() override;
 
   /// Size of buffer required for config hash hex string (8 hex chars + null terminator)
-  static constexpr size_t CONFIG_HASH_STR_SIZE = 9;
+  static constexpr size_t CONFIG_HASH_STR_SIZE = format_hex_size(sizeof(uint32_t));
 
 #ifdef USE_MDNS_EVENT_DRIVEN_POLLING
   // LEAmDNS has meaningful work only during the probe+announce phase (3×250ms probes +
@@ -130,35 +127,7 @@ class MDNSComponent final : public Component
   /// Helper to set up services and MAC buffers, then call platform-specific registration
   using PlatformRegisterFn = void (*)(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &);
 
-  void setup_buffers_and_register_(PlatformRegisterFn platform_register) {
-#ifdef USE_MDNS_STORE_SERVICES
-    auto &services = this->services_;
-#else
-    StaticVector<MDNSService, MDNS_SERVICE_COUNT> services_storage;
-    auto &services = services_storage;
-#endif
-
-#ifdef USE_API
-#ifdef USE_MDNS_STORE_SERVICES
-    get_mac_address_into_buffer(this->mac_address_);
-    char *mac_ptr = this->mac_address_;
-    char *cfg_ptr = this->config_hash_str_;
-#else
-    char mac_address[MAC_ADDRESS_BUFFER_SIZE];
-    char config_hash_str[CONFIG_HASH_STR_SIZE];
-    get_mac_address_into_buffer(mac_address);
-    char *mac_ptr = mac_address;
-    char *cfg_ptr = config_hash_str;
-#endif
-    snprintf(cfg_ptr, CONFIG_HASH_STR_SIZE, "%08" PRIx32, App.get_config_hash());
-#else
-    char *mac_ptr = nullptr;
-    char *cfg_ptr = nullptr;
-#endif
-
-    this->compile_records_(services, mac_ptr, cfg_ptr);
-    platform_register(this, services);
-  }
+  void setup_buffers_and_register_(PlatformRegisterFn platform_register);
 
 #ifdef USE_MDNS_DYNAMIC_TXT
   /// Storage for runtime-generated TXT values from user lambdas