From 7a0d7c5ca141ea40ffeb638cceb627196f901fc8 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 5 Jan 2026 09:24:33 -1000
Subject: [PATCH 1/2] [voice_assistant] Reduce heap allocation with stack-based
 timer formatting

---
 esphome/components/voice_assistant/voice_assistant.cpp |  3 ++-
 esphome/components/voice_assistant/voice_assistant.h   | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/esphome/components/voice_assistant/voice_assistant.cpp b/esphome/components/voice_assistant/voice_assistant.cpp
index de683113bb..05c356ae4c 100644
--- a/esphome/components/voice_assistant/voice_assistant.cpp
+++ b/esphome/components/voice_assistant/voice_assistant.cpp
@@ -866,11 +866,12 @@ void VoiceAssistant::on_timer_event(const api::VoiceAssistantTimerEventResponse
       .is_active = msg.is_active,
   };
   this->timers_[timer.id] = timer;
+  char timer_buf[Timer::TO_STR_BUFFER_SIZE];
   ESP_LOGD(TAG,
            "Timer Event\n"
            "  Type: %" PRId32 "\n"
            "  %s",
-           msg.event_type, timer.to_string().c_str());
+           msg.event_type, timer.to_str(timer_buf));
 
   switch (msg.event_type) {
     case api::enums::VOICE_ASSISTANT_TIMER_STARTED:
diff --git a/esphome/components/voice_assistant/voice_assistant.h b/esphome/components/voice_assistant/voice_assistant.h
index 8d3d3497ec..7b0c9072ba 100644
--- a/esphome/components/voice_assistant/voice_assistant.h
+++ b/esphome/components/voice_assistant/voice_assistant.h
@@ -23,6 +23,7 @@
 #endif
 #include "esphome/components/socket/socket.h"
 
+#include <span>
 #include <unordered_map>
 #include <vector>
 
@@ -76,6 +77,15 @@ struct Timer {
                        this->id.c_str(), this->name.c_str(), this->total_seconds, this->seconds_left,
                        YESNO(this->is_active));
   }
+  /// Buffer size for to_str() - sufficient for typical timer names
+  static constexpr size_t TO_STR_BUFFER_SIZE = 128;
+  /// Format to buffer, returns pointer to buffer (may truncate long names)
+  const char *to_str(std::span<char, TO_STR_BUFFER_SIZE> buffer) const {
+    snprintf(buffer.data(), buffer.size(),
+             "Timer(id=%s, name=%s, total_seconds=%" PRIu32 ", seconds_left=%" PRIu32 ", is_active=%s)",
+             this->id.c_str(), this->name.c_str(), this->total_seconds, this->seconds_left, YESNO(this->is_active));
+    return buffer.data();
+  }
 };
 
 struct WakeWord {

From cc8bd2d29d4ed84fcb52c2efa9df0dda06a34907 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Mon, 5 Jan 2026 09:26:41 -1000
Subject: [PATCH 2/2] dry

---
 esphome/components/voice_assistant/voice_assistant.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/esphome/components/voice_assistant/voice_assistant.h b/esphome/components/voice_assistant/voice_assistant.h
index 7b0c9072ba..b1b3df7bbd 100644
--- a/esphome/components/voice_assistant/voice_assistant.h
+++ b/esphome/components/voice_assistant/voice_assistant.h
@@ -72,11 +72,6 @@ struct Timer {
   uint32_t seconds_left;
   bool is_active;
 
-  std::string to_string() const {
-    return str_sprintf("Timer(id=%s, name=%s, total_seconds=%" PRIu32 ", seconds_left=%" PRIu32 ", is_active=%s)",
-                       this->id.c_str(), this->name.c_str(), this->total_seconds, this->seconds_left,
-                       YESNO(this->is_active));
-  }
   /// Buffer size for to_str() - sufficient for typical timer names
   static constexpr size_t TO_STR_BUFFER_SIZE = 128;
   /// Format to buffer, returns pointer to buffer (may truncate long names)
@@ -86,6 +81,10 @@ struct Timer {
              this->id.c_str(), this->name.c_str(), this->total_seconds, this->seconds_left, YESNO(this->is_active));
     return buffer.data();
   }
+  std::string to_string() const {
+    char buffer[TO_STR_BUFFER_SIZE];
+    return this->to_str(buffer);
+  }
 };
 
 struct WakeWord {