diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index 652b456850..d6384456d5 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -763,7 +763,7 @@ message SubscribeHomeassistantServicesRequest {
 
 message HomeassistantServiceMap {
   string key = 1;
-  string value = 2 [(no_zero_copy) = true];
+  string value = 2;
 }
 
 message HomeassistantActionRequest {
@@ -779,7 +779,7 @@ message HomeassistantActionRequest {
   bool is_event = 5;
   uint32 call_id = 6 [(field_ifdef) = "USE_API_HOMEASSISTANT_ACTION_RESPONSES"];
   bool wants_response = 7 [(field_ifdef) = "USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON"];
-  string response_template = 8 [(no_zero_copy) = true, (field_ifdef) = "USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON"];
+  string response_template = 8 [(field_ifdef) = "USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON"];
 }
 
 // Message sent by Home Assistant to ESPHome with service call response data
diff --git a/esphome/components/api/api_options.proto b/esphome/components/api/api_options.proto
index 1916e84625..a863f2c7a8 100644
--- a/esphome/components/api/api_options.proto
+++ b/esphome/components/api/api_options.proto
@@ -27,7 +27,6 @@ extend google.protobuf.MessageOptions {
 extend google.protobuf.FieldOptions {
     optional string field_ifdef = 1042;
     optional uint32 fixed_array_size = 50007;
-    optional bool no_zero_copy = 50008 [default=false];
     optional bool fixed_array_skip_zero = 50009 [default=false];
     optional string fixed_array_size_define = 50010;
     optional string fixed_array_with_length_define = 50011;
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 01fe44d7c7..e21b8596ca 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -1053,7 +1053,7 @@ class SubscribeHomeassistantServicesRequest final : public ProtoMessage {
 class HomeassistantServiceMap final : public ProtoMessage {
  public:
   StringRef key{};
-  std::string value{};
+  StringRef value{};
   void encode(ProtoWriteBuffer buffer) const override;
   void calculate_size(ProtoSize &size) const override;
 #ifdef HAS_PROTO_MESSAGE_DUMP
@@ -1081,7 +1081,7 @@ class HomeassistantActionRequest final : public ProtoMessage {
   bool wants_response{false};
 #endif
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON
-  std::string response_template{};
+  StringRef response_template{};
 #endif
   void encode(ProtoWriteBuffer buffer) const override;
   void calculate_size(ProtoSize &size) const override;
diff --git a/esphome/components/api/custom_api_device.h b/esphome/components/api/custom_api_device.h
index b16164270b..2fd9cb0dd2 100644
--- a/esphome/components/api/custom_api_device.h
+++ b/esphome/components/api/custom_api_device.h
@@ -265,7 +265,7 @@ class CustomAPIDevice {
     for (auto &it : data) {
       auto &kv = resp.data.emplace_back();
       kv.key = StringRef(it.first);
-      kv.value = it.second;  // value is std::string (no_zero_copy), assign directly
+      kv.value = StringRef(it.second);  // data map lives until send completes
     }
     global_api_server->send_homeassistant_action(resp);
   }
@@ -308,7 +308,7 @@ class CustomAPIDevice {
     for (auto &it : data) {
       auto &kv = resp.data.emplace_back();
       kv.key = StringRef(it.first);
-      kv.value = it.second;  // value is std::string (no_zero_copy), assign directly
+      kv.value = StringRef(it.second);  // data map lives until send completes
     }
     global_api_server->send_homeassistant_action(resp);
   }
diff --git a/esphome/components/api/homeassistant_service.h b/esphome/components/api/homeassistant_service.h
index a17c99b8ba..9bffe18764 100644
--- a/esphome/components/api/homeassistant_service.h
+++ b/esphome/components/api/homeassistant_service.h
@@ -149,11 +149,21 @@ template<typename... Ts> class HomeAssistantServiceCallAction : public Action<Ts
     std::string service_value = this->service_.value(x...);
     resp.service = StringRef(service_value);
     resp.is_event = this->flags_.is_event;
-    this->populate_service_map(resp.data, this->data_, x...);
-    this->populate_service_map(resp.data_template, this->data_template_, x...);
-    this->populate_service_map(resp.variables, this->variables_, x...);
+
+    // Local storage for lambda-evaluated strings - lives until after send
+    FixedVector<std::string> data_storage;
+    FixedVector<std::string> data_template_storage;
+    FixedVector<std::string> variables_storage;
+
+    this->populate_service_map(resp.data, this->data_, data_storage, x...);
+    this->populate_service_map(resp.data_template, this->data_template_, data_template_storage, x...);
+    this->populate_service_map(resp.variables, this->variables_, variables_storage, x...);
 
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
+#ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON
+    // IMPORTANT: Declare at outer scope so it lives until send_homeassistant_action returns.
+    std::string response_template_value;
+#endif
     if (this->flags_.wants_status) {
       // Generate a unique call ID for this service call
       static uint32_t call_id_counter = 1;
@@ -164,8 +174,8 @@ template<typename... Ts> class HomeAssistantServiceCallAction : public Action<Ts
         resp.wants_response = true;
         // Set response template if provided
         if (this->flags_.has_response_template) {
-          std::string response_template_value = this->response_template_.value(x...);
-          resp.response_template = response_template_value;
+          response_template_value = this->response_template_.value(x...);
+          resp.response_template = StringRef(response_template_value);
         }
       }
 #endif
@@ -205,12 +215,31 @@ template<typename... Ts> class HomeAssistantServiceCallAction : public Action<Ts
   }
 
   template<typename VectorType, typename SourceType>
-  static void populate_service_map(VectorType &dest, SourceType &source, Ts... x) {
+  static void populate_service_map(VectorType &dest, SourceType &source, FixedVector<std::string> &value_storage,
+                                   Ts... x) {
     dest.init(source.size());
+
+    // Count non-static strings to allocate exact storage needed
+    size_t lambda_count = 0;
+    for (const auto &it : source) {
+      if (!it.value.is_static_string()) {
+        lambda_count++;
+      }
+    }
+    value_storage.init(lambda_count);
+
     for (auto &it : source) {
       auto &kv = dest.emplace_back();
       kv.key = StringRef(it.key);
-      kv.value = it.value.value(x...);
+
+      if (it.value.is_static_string()) {
+        // Static string from YAML - zero allocation
+        kv.value = StringRef(it.value.get_static_string());
+      } else {
+        // Lambda evaluation - store result, reference it
+        value_storage.push_back(it.value.value(x...));
+        kv.value = StringRef(value_storage.back());
+      }
     }
   }
 
diff --git a/esphome/components/homeassistant/number/homeassistant_number.cpp b/esphome/components/homeassistant/number/homeassistant_number.cpp
index 82387a81e9..92ecd5ea39 100644
--- a/esphome/components/homeassistant/number/homeassistant_number.cpp
+++ b/esphome/components/homeassistant/number/homeassistant_number.cpp
@@ -91,11 +91,14 @@ void HomeassistantNumber::control(float value) {
   resp.data.init(2);
   auto &entity_id = resp.data.emplace_back();
   entity_id.key = ENTITY_ID_KEY;
-  entity_id.value = this->entity_id_;
+  entity_id.value = StringRef(this->entity_id_);
 
   auto &entity_value = resp.data.emplace_back();
   entity_value.key = VALUE_KEY;
-  entity_value.value = to_string(value);
+  // Stack buffer - no heap allocation; %g produces shortest representation
+  char value_buf[16];
+  snprintf(value_buf, sizeof(value_buf), "%g", value);
+  entity_value.value = StringRef(value_buf);
 
   api::global_api_server->send_homeassistant_action(resp);
 }
diff --git a/esphome/components/homeassistant/switch/homeassistant_switch.cpp b/esphome/components/homeassistant/switch/homeassistant_switch.cpp
index 79d17eb290..cc3d582bf3 100644
--- a/esphome/components/homeassistant/switch/homeassistant_switch.cpp
+++ b/esphome/components/homeassistant/switch/homeassistant_switch.cpp
@@ -55,7 +55,7 @@ void HomeassistantSwitch::write_state(bool state) {
   resp.data.init(1);
   auto &entity_id_kv = resp.data.emplace_back();
   entity_id_kv.key = ENTITY_ID_KEY;
-  entity_id_kv.value = this->entity_id_;
+  entity_id_kv.value = StringRef(this->entity_id_);
 
   api::global_api_server->send_homeassistant_action(resp);
 }
diff --git a/esphome/core/automation.h b/esphome/core/automation.h
index 61d2944acf..585b434bb2 100644
--- a/esphome/core/automation.h
+++ b/esphome/core/automation.h
@@ -159,6 +159,12 @@ template<typename T, typename... X> class TemplatableValue {
     return this->value(x...);
   }
 
+  /// Check if this holds a static string (const char* stored without allocation)
+  bool is_static_string() const { return this->type_ == STATIC_STRING; }
+
+  /// Get the static string pointer (only valid if is_static_string() returns true)
+  const char *get_static_string() const { return this->static_str_; }
+
  protected:
   enum : uint8_t {
     NONE,
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index c61555805e..118c87356e 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -376,10 +376,8 @@ def create_field_type_info(
 
         return BytesType(field, needs_decode, needs_encode)
 
-    # Special handling for string fields - use StringRef for zero-copy unless no_zero_copy is set
+    # Special handling for string fields - use StringRef for zero-copy
     if field.type == 9:
-        if get_field_opt(field, pb.no_zero_copy, False):
-            return StringType(field, needs_decode, needs_encode)
         return PointerToStringBufferType(field, None)
 
     validate_field_type(field.type, field.name)
@@ -585,15 +583,12 @@ class StringType(TypeInfo):
     def public_content(self) -> list[str]:
         content: list[str] = []
 
-        # Check if no_zero_copy option is set
-        no_zero_copy = get_field_opt(self._field, pb.no_zero_copy, False)
-
-        # Add std::string storage if message needs decoding OR if no_zero_copy is set
-        if self._needs_decode or no_zero_copy:
+        # Add std::string storage if message needs decoding
+        if self._needs_decode:
             content.append(f"std::string {self.field_name}{{}};")
 
-        # Only add StringRef if encoding is needed AND no_zero_copy is not set
-        if self._needs_encode and not no_zero_copy:
+        # Add StringRef if encoding is needed
+        if self._needs_encode:
             content.extend(
                 [
                     # Add StringRef field if message needs encoding
@@ -608,27 +603,14 @@ class StringType(TypeInfo):
 
     @property
     def encode_content(self) -> str:
-        # Check if no_zero_copy option is set
-        no_zero_copy = get_field_opt(self._field, pb.no_zero_copy, False)
-
-        if no_zero_copy:
-            # Use the std::string directly
-            return f"buffer.encode_string({self.number}, this->{self.field_name});"
         # Use the StringRef
         return f"buffer.encode_string({self.number}, this->{self.field_name}_ref_);"
 
     def dump(self, name):
-        # Check if no_zero_copy option is set
-        no_zero_copy = get_field_opt(self._field, pb.no_zero_copy, False)
-
         # If name is 'it', this is a repeated field element - always use string
         if name == "it":
             return "append_quoted_string(out, StringRef(it));"
 
-        # If no_zero_copy is set, always use std::string
-        if no_zero_copy:
-            return f'out.append("\'").append(this->{self.field_name}).append("\'");'
-
         # For SOURCE_CLIENT only, always use std::string
         if not self._needs_encode:
             return f'out.append("\'").append(this->{self.field_name}).append("\'");'
@@ -648,13 +630,6 @@ class StringType(TypeInfo):
 
     @property
     def dump_content(self) -> str:
-        # Check if no_zero_copy option is set
-        no_zero_copy = get_field_opt(self._field, pb.no_zero_copy, False)
-
-        # If no_zero_copy is set, always use std::string
-        if no_zero_copy:
-            return f'dump_field(out, "{self.name}", this->{self.field_name});'
-
         # For SOURCE_CLIENT only, use std::string
         if not self._needs_encode:
             return f'dump_field(out, "{self.name}", this->{self.field_name});'
@@ -670,17 +645,8 @@ class StringType(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        # Check if no_zero_copy option is set
-        no_zero_copy = get_field_opt(self._field, pb.no_zero_copy, False)
-
-        # For SOURCE_CLIENT only messages or no_zero_copy, use the string field directly
-        if not self._needs_encode or no_zero_copy:
-            # For no_zero_copy, we need to use .size() on the string
-            if no_zero_copy and name != "it":
-                field_id_size = self.calculate_field_id_size()
-                return (
-                    f"size.add_length({field_id_size}, this->{self.field_name}.size());"
-                )
+        # For SOURCE_CLIENT only messages, use the string field directly
+        if not self._needs_encode:
             return self._get_simple_size_calculation(name, force, "add_length")
 
         # Check if this is being called from a repeated field context