From c3252e861f95ceefa7cf468e66dcf08c0d65cd73 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Fri, 27 Feb 2026 10:39:53 -1000
Subject: [PATCH] Don't allocate Mutex on single-threaded platforms

On ESPHOME_THREAD_SINGLE (ESP8266), the lock is never used.
Guarding it avoids the static local guard variable overhead
(8 bytes RAM + init check on every call).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 esphome/core/time_64.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/esphome/core/time_64.cpp b/esphome/core/time_64.cpp
index c967505544..d067bc11c6 100644
--- a/esphome/core/time_64.cpp
+++ b/esphome/core/time_64.cpp
@@ -21,7 +21,9 @@ static constexpr uint32_t HALF_MAX_UINT32 = std::numeric_limits<uint32_t>::max()
 
 uint64_t Millis64Impl::compute(uint32_t now) {
   // State variables for rollover tracking - static to persist across calls
+#ifndef ESPHOME_THREAD_SINGLE
   static Mutex lock;
+#endif
 #ifdef ESPHOME_THREAD_MULTI_ATOMICS
   /*
    * Multi-threaded platforms with atomic support: last_millis needs atomic for lock-free updates.