diff --git a/esphome/components/api/api.proto b/esphome/components/api/api.proto
index eb6ccbfb91..e0e1602fcb 100644
--- a/esphome/components/api/api.proto
+++ b/esphome/components/api/api.proto
@@ -760,7 +760,7 @@ message SubscribeHomeassistantServicesRequest {
 
 message HomeassistantServiceMap {
   string key = 1;
-  string value = 2;
+  string value = 2 [(no_zero_copy) = true];
 }
 
 message HomeassistantServiceResponse {
diff --git a/esphome/components/api/api_options.proto b/esphome/components/api/api_options.proto
index bb3947e8a3..4f0f52fc6f 100644
--- a/esphome/components/api/api_options.proto
+++ b/esphome/components/api/api_options.proto
@@ -27,4 +27,5 @@ 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];
 }
diff --git a/esphome/components/api/api_pb2.cpp b/esphome/components/api/api_pb2.cpp
index 89177b233a..b587ee5f03 100644
--- a/esphome/components/api/api_pb2.cpp
+++ b/esphome/components/api/api_pb2.cpp
@@ -846,11 +846,11 @@ void NoiseEncryptionSetKeyResponse::calculate_size(uint32_t &total_size) const {
 #ifdef USE_API_HOMEASSISTANT_SERVICES
 void HomeassistantServiceMap::encode(ProtoWriteBuffer buffer) const {
   buffer.encode_string(1, this->key_ref_);
-  buffer.encode_string(2, this->value_ref_);
+  buffer.encode_string(2, this->value);
 }
 void HomeassistantServiceMap::calculate_size(uint32_t &total_size) const {
   ProtoSize::add_string_field(total_size, 1, this->key_ref_.size());
-  ProtoSize::add_string_field(total_size, 1, this->value_ref_.size());
+  ProtoSize::add_string_field(total_size, 1, this->value.size());
 }
 void HomeassistantServiceResponse::encode(ProtoWriteBuffer buffer) const {
   buffer.encode_string(1, this->service_ref_);
diff --git a/esphome/components/api/api_pb2.h b/esphome/components/api/api_pb2.h
index 65623144d1..fb8174f988 100644
--- a/esphome/components/api/api_pb2.h
+++ b/esphome/components/api/api_pb2.h
@@ -1062,8 +1062,7 @@ class HomeassistantServiceMap : public ProtoMessage {
  public:
   StringRef key_ref_{};
   void set_key(const StringRef &ref) { this->key_ref_ = ref; }
-  StringRef value_ref_{};
-  void set_value(const StringRef &ref) { this->value_ref_ = ref; }
+  std::string value{};
   void encode(ProtoWriteBuffer buffer) const override;
   void calculate_size(uint32_t &total_size) const override;
 #ifdef HAS_PROTO_MESSAGE_DUMP
diff --git a/esphome/components/api/api_pb2_dump.cpp b/esphome/components/api/api_pb2_dump.cpp
index c18425f369..aca60464a3 100644
--- a/esphome/components/api/api_pb2_dump.cpp
+++ b/esphome/components/api/api_pb2_dump.cpp
@@ -1045,7 +1045,7 @@ void SubscribeHomeassistantServicesRequest::dump_to(std::string &out) const {
 void HomeassistantServiceMap::dump_to(std::string &out) const {
   MessageDumpHelper helper(out, "HomeassistantServiceMap");
   dump_field(out, "key", this->key_ref_);
-  dump_field(out, "value", this->value_ref_);
+  dump_field(out, "value", this->value);
 }
 void HomeassistantServiceResponse::dump_to(std::string &out) const {
   MessageDumpHelper helper(out, "HomeassistantServiceResponse");
diff --git a/esphome/components/api/custom_api_device.h b/esphome/components/api/custom_api_device.h
index 2f85a40614..a39947e725 100644
--- a/esphome/components/api/custom_api_device.h
+++ b/esphome/components/api/custom_api_device.h
@@ -175,7 +175,7 @@ class CustomAPIDevice {
       resp.data.emplace_back();
       auto &kv = resp.data.back();
       kv.set_key(StringRef(it.first));
-      kv.set_value(StringRef(it.second));
+      kv.value = it.second;
     }
     global_api_server->send_homeassistant_service_call(resp);
   }
@@ -218,7 +218,7 @@ class CustomAPIDevice {
       resp.data.emplace_back();
       auto &kv = resp.data.back();
       kv.set_key(StringRef(it.first));
-      kv.set_value(StringRef(it.second));
+      kv.value = it.second;
     }
     global_api_server->send_homeassistant_service_call(resp);
   }
diff --git a/esphome/components/api/homeassistant_service.h b/esphome/components/api/homeassistant_service.h
index ec17c0c7a4..5df9c7c792 100644
--- a/esphome/components/api/homeassistant_service.h
+++ b/esphome/components/api/homeassistant_service.h
@@ -70,22 +70,19 @@ template<typename... Ts> class HomeAssistantServiceCallAction : public Action<Ts
       resp.data.emplace_back();
       auto &kv = resp.data.back();
       kv.set_key(StringRef(it.key));
-      std::string value = it.value.value(x...);
-      kv.set_value(StringRef(value));
+      kv.value = it.value.value(x...);
     }
     for (auto &it : this->data_template_) {
       resp.data_template.emplace_back();
       auto &kv = resp.data_template.back();
       kv.set_key(StringRef(it.key));
-      std::string value = it.value.value(x...);
-      kv.set_value(StringRef(value));
+      kv.value = it.value.value(x...);
     }
     for (auto &it : this->variables_) {
       resp.variables.emplace_back();
       auto &kv = resp.variables.back();
       kv.set_key(StringRef(it.key));
-      std::string value = it.value.value(x...);
-      kv.set_value(StringRef(value));
+      kv.value = it.value.value(x...);
     }
     this->parent_->send_homeassistant_service_call(resp);
   }
diff --git a/esphome/components/homeassistant/number/homeassistant_number.cpp b/esphome/components/homeassistant/number/homeassistant_number.cpp
index ffb352c969..87bf6727f2 100644
--- a/esphome/components/homeassistant/number/homeassistant_number.cpp
+++ b/esphome/components/homeassistant/number/homeassistant_number.cpp
@@ -93,14 +93,12 @@ void HomeassistantNumber::control(float value) {
   resp.data.emplace_back();
   auto &entity_id = resp.data.back();
   entity_id.set_key(ENTITY_ID_KEY);
-  entity_id.set_value(StringRef(this->entity_id_));
+  entity_id.value = this->entity_id_;
 
   resp.data.emplace_back();
   auto &entity_value = resp.data.back();
   entity_value.set_key(VALUE_KEY);
-  // to_string() returns a temporary - must store it to avoid dangling reference
-  std::string value_str = to_string(value);
-  entity_value.set_value(StringRef(value_str));
+  entity_value.value = to_string(value);
 
   api::global_api_server->send_homeassistant_service_call(resp);
 }
diff --git a/esphome/components/homeassistant/switch/homeassistant_switch.cpp b/esphome/components/homeassistant/switch/homeassistant_switch.cpp
index 0fe609bf43..b3300335b9 100644
--- a/esphome/components/homeassistant/switch/homeassistant_switch.cpp
+++ b/esphome/components/homeassistant/switch/homeassistant_switch.cpp
@@ -54,7 +54,7 @@ void HomeassistantSwitch::write_state(bool state) {
   resp.data.emplace_back();
   auto &entity_id_kv = resp.data.back();
   entity_id_kv.set_key(ENTITY_ID_KEY);
-  entity_id_kv.set_value(StringRef(this->entity_id_));
+  entity_id_kv.value = this->entity_id_;
 
   api::global_api_server->send_homeassistant_service_call(resp);
 }
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index 92c85d2366..4b9a61383d 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -562,11 +562,16 @@ class StringType(TypeInfo):
     @property
     def public_content(self) -> list[str]:
         content: list[str] = []
-        # Add std::string storage if message needs decoding
-        if self._needs_decode:
+
+        # 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:
             content.append(f"std::string {self.field_name}{{}};")
 
-        if self._needs_encode:
+        # Only add StringRef if encoding is needed AND no_zero_copy is not set
+        if self._needs_encode and not no_zero_copy:
             content.extend(
                 [
                     # Add StringRef field if message needs encoding
@@ -581,13 +586,28 @@ class StringType(TypeInfo):
 
     @property
     def encode_content(self) -> str:
-        return f"buffer.encode_string({self.number}, this->{self.field_name}_ref_);"
+        # 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});"
+        else:
+            # 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("\'");'
@@ -607,6 +627,13 @@ 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});'
@@ -622,8 +649,15 @@ class StringType(TypeInfo):
         return o
 
     def get_size_calculation(self, name: str, force: bool = False) -> str:
-        # For SOURCE_CLIENT only messages, use the string field directly
-        if not self._needs_encode:
+        # 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"ProtoSize::add_string_field(total_size, {field_id_size}, this->{self.field_name}.size());"
             return self._get_simple_size_calculation(name, force, "add_string_field")
 
         # Check if this is being called from a repeated field context
diff --git a/tests/integration/fixtures/api_homeassistant.yaml b/tests/integration/fixtures/api_homeassistant.yaml
new file mode 100644
index 0000000000..ce8628977a
--- /dev/null
+++ b/tests/integration/fixtures/api_homeassistant.yaml
@@ -0,0 +1,311 @@
+esphome:
+  name: test-ha-api
+  friendly_name: Home Assistant API Test
+
+host:
+
+api:
+  services:
+    - service: trigger_all_tests
+      then:
+        - logger.log: "=== Starting Home Assistant API Tests ==="
+        - button.press: test_basic_service
+        - button.press: test_templated_service
+        - button.press: test_empty_string_service
+        - button.press: test_multiple_fields_service
+        - button.press: test_complex_lambda_service
+        - button.press: test_all_empty_service
+        - button.press: test_rapid_service_calls
+        - button.press: test_read_ha_states
+        - number.set:
+            id: ha_number
+            value: 42.5
+        - switch.turn_on: ha_switch
+        - switch.turn_off: ha_switch
+        - logger.log: "=== All tests completed ==="
+
+logger:
+  level: DEBUG
+
+# Time component for templated values
+time:
+  - platform: homeassistant
+    id: homeassistant_time
+
+# Global variables for testing
+globals:
+  - id: test_brightness
+    type: int
+    initial_value: '75'
+  - id: test_string
+    type: std::string
+    initial_value: '"test_value"'
+
+# Sensors for testing state reading
+sensor:
+  - platform: template
+    name: "Test Sensor"
+    id: test_sensor
+    lambda: return 42.0;
+    update_interval: 0.1s
+
+  # Home Assistant sensor that reads external state
+  - platform: homeassistant
+    name: "HA Temperature"
+    entity_id: sensor.external_temperature
+    id: ha_temperature
+    on_value:
+      then:
+        - logger.log:
+            format: "HA Temperature state updated: %.1f"
+            args: ['x']
+
+  # Test multiple HA state sensors
+  - platform: homeassistant
+    name: "HA Humidity"
+    entity_id: sensor.external_humidity
+    id: ha_humidity
+    on_value:
+      then:
+        - logger.log:
+            format: "HA Humidity state updated: %.1f"
+            args: ['x']
+
+# Binary sensor from Home Assistant
+binary_sensor:
+  - platform: homeassistant
+    name: "HA Motion"
+    entity_id: binary_sensor.external_motion
+    id: ha_motion
+    on_state:
+      then:
+        - logger.log:
+            format: "HA Motion state changed: %s"
+            args: ['x ? "ON" : "OFF"']
+
+# Text sensor from Home Assistant
+text_sensor:
+  - platform: homeassistant
+    name: "HA Weather"
+    entity_id: weather.home
+    attribute: condition
+    id: ha_weather
+    on_value:
+      then:
+        - logger.log:
+            format: "HA Weather condition updated: %s"
+            args: ['x.c_str()']
+
+  # Test empty state handling
+  - platform: homeassistant
+    name: "HA Empty State"
+    entity_id: sensor.nonexistent_sensor
+    id: ha_empty_state
+    on_value:
+      then:
+        - logger.log:
+            format: "HA Empty state updated: %s"
+            args: ['x.c_str()']
+
+# Number component for testing HA number control
+number:
+  - platform: template
+    name: "HA Controlled Number"
+    id: ha_number
+    min_value: 0
+    max_value: 100
+    step: 1
+    optimistic: true
+    set_action:
+      - logger.log:
+          format: "Setting HA number to: %.1f"
+          args: ['x']
+      - homeassistant.action:
+          action: input_number.set_value
+          data:
+            entity_id: input_number.test_number
+            value: !lambda 'return to_string(x);'
+
+# Switch component for testing HA switch control
+switch:
+  - platform: template
+    name: "HA Controlled Switch"
+    id: ha_switch
+    optimistic: true
+    turn_on_action:
+      - logger.log: "Toggling HA switch: switch.test_switch ON"
+      - homeassistant.action:
+          action: switch.turn_on
+          data:
+            entity_id: switch.test_switch
+    turn_off_action:
+      - logger.log: "Toggling HA switch: switch.test_switch OFF"
+      - homeassistant.action:
+          action: switch.turn_off
+          data:
+            entity_id: switch.test_switch
+
+# Buttons for testing various service call scenarios
+button:
+  # Test 1: Basic service call with static values
+  - platform: template
+    name: "Test Basic Service"
+    id: test_basic_service
+    on_press:
+      - logger.log: "Sending HomeAssistant service call: light.turn_off"
+      - homeassistant.action:
+          action: light.turn_off
+          data:
+            entity_id: light.test_light
+      - logger.log: "Service data: entity_id=light.test_light"
+
+  # Test 2: Service call with templated/lambda values (main bug fix test)
+  - platform: template
+    name: "Test Templated Service"
+    id: test_templated_service
+    on_press:
+      - logger.log: "Testing templated service call"
+      - lambda: |-
+          int brightness_percent = id(test_brightness);
+          std::string computed = to_string(brightness_percent * 255 / 100);
+          ESP_LOGI("test", "Lambda computed value: %s", computed.c_str());
+      - homeassistant.action:
+          action: light.turn_on
+          data:
+            entity_id: light.test_light
+            # This creates a temporary string - the main test case
+            brightness: !lambda 'return to_string(id(test_brightness) * 255 / 100);'
+          data_template:
+            color_name: !lambda 'return id(test_string);'
+          variables:
+            transition: !lambda 'return "2.5";'
+
+  # Test 3: Service call with empty string values
+  - platform: template
+    name: "Test Empty String Service"
+    id: test_empty_string_service
+    on_press:
+      - logger.log: "Testing empty string values"
+      - homeassistant.action:
+          action: notify.test
+          data:
+            message: "Test message"
+            title: ""
+          data_template:
+            target: !lambda 'return "";'
+          variables:
+            sound: !lambda 'return "";'
+
+      - logger.log: "Empty value for key: title"
+      - logger.log: "Empty value for key: target"
+      - logger.log: "Empty value for key: sound"
+
+  # Test 4: Service call with multiple data fields
+  - platform: template
+    name: "Test Multiple Fields Service"
+    id: test_multiple_fields_service
+    on_press:
+      - logger.log: "Testing multiple data fields"
+      - homeassistant.action:
+          action: climate.set_temperature
+          data:
+            entity_id: climate.test_climate
+            temperature: "22"
+            hvac_mode: "heat"
+          data_template:
+            target_temp_high: !lambda 'return "24";'
+            target_temp_low: !lambda 'return "20";'
+          variables:
+            preset_mode: !lambda 'return "comfort";'
+
+  # Test 5: Complex lambda with string operations
+  - platform: template
+    name: "Test Complex Lambda Service"
+    id: test_complex_lambda_service
+    on_press:
+      - logger.log: "Testing complex lambda expressions"
+      - homeassistant.action:
+          action: script.test_script
+          data:
+            entity_id: !lambda |-
+              std::string base = "light.";
+              std::string room = "living_room";
+              return base + room;
+            brightness_pct: !lambda |-
+              float sensor_val = id(test_sensor).state;
+              int pct = (int)(sensor_val * 2.38);  // 42 * 2.38 ≈ 100
+              return to_string(pct);
+          data_template:
+            message: !lambda |-
+              char buffer[50];
+              snprintf(buffer, sizeof(buffer), "Sensor: %.1f, Time: %02d:%02d",
+                       id(test_sensor).state,
+                       id(homeassistant_time).now().hour,
+                       id(homeassistant_time).now().minute);
+              return std::string(buffer);
+
+  # Test 6: Service with only empty strings to verify size calculation
+  - platform: template
+    name: "Test All Empty Service"
+    id: test_all_empty_service
+    on_press:
+      - logger.log: "Testing all empty string values"
+      - homeassistant.action:
+          action: test.empty
+          data:
+            field1: ""
+            field2: ""
+          data_template:
+            field3: !lambda 'return "";'
+          variables:
+            field4: !lambda 'return "";'
+      - logger.log: "All empty service call completed"
+
+  # Test 7: Rapid successive service calls
+  - platform: template
+    name: "Test Rapid Service Calls"
+    id: test_rapid_service_calls
+    on_press:
+      - logger.log: "Testing rapid service calls"
+      - repeat:
+          count: 5
+          then:
+            - homeassistant.action:
+                action: counter.increment
+                data:
+                  entity_id: counter.test_counter
+            - delay: 10ms
+      - logger.log: "Rapid service calls completed"
+
+  # Test 8: Log current HA states
+  - platform: template
+    name: "Test Read HA States"
+    id: test_read_ha_states
+    on_press:
+      - logger.log: "Reading current HA states"
+      - lambda: |-
+          if (id(ha_temperature).has_state()) {
+            ESP_LOGI("test", "Current HA Temperature: %.1f", id(ha_temperature).state);
+          } else {
+            ESP_LOGI("test", "HA Temperature has no state");
+          }
+
+          if (id(ha_humidity).has_state()) {
+            ESP_LOGI("test", "Current HA Humidity: %.1f", id(ha_humidity).state);
+          } else {
+            ESP_LOGI("test", "HA Humidity has no state");
+          }
+
+          ESP_LOGI("test", "Current HA Motion: %s", id(ha_motion).state ? "ON" : "OFF");
+
+          if (id(ha_weather).has_state()) {
+            ESP_LOGI("test", "Current HA Weather: %s", id(ha_weather).state.c_str());
+          } else {
+            ESP_LOGI("test", "HA Weather has no state");
+          }
+
+          if (id(ha_empty_state).has_state()) {
+            ESP_LOGI("test", "HA Empty State value: %s", id(ha_empty_state).state.c_str());
+          } else {
+            ESP_LOGI("test", "HA Empty State has no value (expected)");
+          }
diff --git a/tests/integration/test_api_homeassistant.py b/tests/integration/test_api_homeassistant.py
new file mode 100644
index 0000000000..f69838396d
--- /dev/null
+++ b/tests/integration/test_api_homeassistant.py
@@ -0,0 +1,305 @@
+"""Integration test for Home Assistant API functionality.
+
+Tests:
+- Home Assistant service calls with templated values (main bug fix)
+- Service calls with empty string values
+- Home Assistant state reading (sensors, binary sensors, text sensors)
+- Home Assistant number and switch component control
+- Complex lambda expressions and string handling
+"""
+
+from __future__ import annotations
+
+import asyncio
+import re
+
+from aioesphomeapi import HomeassistantServiceCall
+import pytest
+
+from .types import APIClientConnectedFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_api_homeassistant(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Comprehensive test for Home Assistant API functionality."""
+    loop = asyncio.get_running_loop()
+
+    # Create futures for patterns that capture values
+    lambda_computed_future = loop.create_future()
+    ha_temp_state_future = loop.create_future()
+    ha_humidity_state_future = loop.create_future()
+    ha_motion_state_future = loop.create_future()
+    ha_weather_state_future = loop.create_future()
+
+    # State update futures
+    temp_update_future = loop.create_future()
+    humidity_update_future = loop.create_future()
+    motion_update_future = loop.create_future()
+    weather_update_future = loop.create_future()
+
+    # Number future
+    ha_number_future = loop.create_future()
+
+    tests_complete_future = loop.create_future()
+
+    # Patterns to match in logs - only keeping patterns that capture values
+    lambda_computed_pattern = re.compile(r"Lambda computed value: (\d+)")
+    ha_temp_state_pattern = re.compile(r"Current HA Temperature: ([\d.]+)")
+    ha_humidity_state_pattern = re.compile(r"Current HA Humidity: ([\d.]+)")
+    ha_motion_state_pattern = re.compile(r"Current HA Motion: (ON|OFF)")
+    ha_weather_state_pattern = re.compile(r"Current HA Weather: (\w+)")
+
+    # State update patterns
+    temp_update_pattern = re.compile(r"HA Temperature state updated: ([\d.]+)")
+    humidity_update_pattern = re.compile(r"HA Humidity state updated: ([\d.]+)")
+    motion_update_pattern = re.compile(r"HA Motion state changed: (ON|OFF)")
+    weather_update_pattern = re.compile(r"HA Weather condition updated: (\w+)")
+
+    # Number pattern
+    ha_number_pattern = re.compile(r"Setting HA number to: ([\d.]+)")
+
+    tests_complete_pattern = re.compile(r"=== All tests completed ===")
+
+    # Track all log lines for debugging
+    log_lines: list[str] = []
+
+    # Track HomeAssistant service calls
+    ha_service_calls: list[HomeassistantServiceCall] = []
+
+    # Service call futures organized by service name
+    service_call_futures = {
+        "light.turn_off": loop.create_future(),  # basic_service_call
+        "light.turn_on": loop.create_future(),  # templated_service_call
+        "notify.test": loop.create_future(),  # empty_string_service_call
+        "climate.set_temperature": loop.create_future(),  # multiple_fields_service_call
+        "script.test_script": loop.create_future(),  # complex_lambda_service_call
+        "test.empty": loop.create_future(),  # all_empty_service_call
+        "input_number.set_value": loop.create_future(),  # ha_number_service_call
+        "switch.turn_on": loop.create_future(),  # ha_switch_on_service_call
+        "switch.turn_off": loop.create_future(),  # ha_switch_off_service_call
+    }
+
+    def on_service_call(service_call: HomeassistantServiceCall) -> None:
+        """Capture HomeAssistant service calls."""
+        ha_service_calls.append(service_call)
+
+        # Check if this service call is one we're waiting for
+        if service_call.service in service_call_futures:
+            future = service_call_futures[service_call.service]
+            if not future.done():
+                future.set_result(service_call)
+
+    def check_output(line: str) -> None:
+        """Check log output for expected messages."""
+        log_lines.append(line)
+
+        # Check for patterns that capture values
+        if not lambda_computed_future.done():
+            match = lambda_computed_pattern.search(line)
+            if match:
+                lambda_computed_future.set_result(match.group(1))
+        elif not ha_temp_state_future.done() and ha_temp_state_pattern.search(line):
+            ha_temp_state_future.set_result(line)
+        elif not ha_humidity_state_future.done() and ha_humidity_state_pattern.search(
+            line
+        ):
+            ha_humidity_state_future.set_result(line)
+        elif not ha_motion_state_future.done() and ha_motion_state_pattern.search(line):
+            ha_motion_state_future.set_result(line)
+        elif not ha_weather_state_future.done() and ha_weather_state_pattern.search(
+            line
+        ):
+            ha_weather_state_future.set_result(line)
+
+        # Check state update patterns
+        elif not temp_update_future.done() and temp_update_pattern.search(line):
+            temp_update_future.set_result(line)
+        elif not humidity_update_future.done() and humidity_update_pattern.search(line):
+            humidity_update_future.set_result(line)
+        elif not motion_update_future.done() and motion_update_pattern.search(line):
+            motion_update_future.set_result(line)
+        elif not weather_update_future.done() and weather_update_pattern.search(line):
+            weather_update_future.set_result(line)
+
+        # Check number pattern
+        elif not ha_number_future.done() and ha_number_pattern.search(line):
+            match = ha_number_pattern.search(line)
+            if match:
+                ha_number_future.set_result(match.group(1))
+
+        elif not tests_complete_future.done() and tests_complete_pattern.search(line):
+            tests_complete_future.set_result(True)
+
+    # Run with log monitoring
+    async with (
+        run_compiled(yaml_config, line_callback=check_output),
+        api_client_connected() as client,
+    ):
+        # Verify device info
+        device_info = await client.device_info()
+        assert device_info is not None
+        assert device_info.name == "test-ha-api"
+
+        # Subscribe to HomeAssistant service calls
+        client.subscribe_service_calls(on_service_call)
+
+        # Send some Home Assistant states for our sensors to read
+        client.send_home_assistant_state("sensor.external_temperature", "", "22.5")
+        client.send_home_assistant_state("sensor.external_humidity", "", "65.0")
+        client.send_home_assistant_state("binary_sensor.external_motion", "", "ON")
+        client.send_home_assistant_state("weather.home", "condition", "sunny")
+
+        # List entities and services
+        _, services = await client.list_entities_services()
+
+        # Find the trigger service
+        trigger_service = next(
+            (s for s in services if s.name == "trigger_all_tests"), None
+        )
+        assert trigger_service is not None, "trigger_all_tests service not found"
+
+        # Execute all tests
+        client.execute_service(trigger_service, {})
+
+        # Wait for all tests to complete with appropriate timeouts
+        try:
+            # Templated service test - the main bug fix
+            computed_value = await asyncio.wait_for(lambda_computed_future, timeout=5.0)
+            # Verify the computed value is reasonable (75 * 255 / 100 = 191.25 -> 191)
+            assert computed_value in ["191", "192"], (
+                f"Unexpected computed value: {computed_value}"
+            )
+
+            # Check state reads - verify we received the mocked values
+            temp_line = await asyncio.wait_for(ha_temp_state_future, timeout=5.0)
+            assert "Current HA Temperature: 22.5" in temp_line
+
+            humidity_line = await asyncio.wait_for(
+                ha_humidity_state_future, timeout=5.0
+            )
+            assert "Current HA Humidity: 65.0" in humidity_line
+
+            motion_line = await asyncio.wait_for(ha_motion_state_future, timeout=5.0)
+            assert "Current HA Motion: ON" in motion_line
+
+            weather_line = await asyncio.wait_for(ha_weather_state_future, timeout=5.0)
+            assert "Current HA Weather: sunny" in weather_line
+
+            # Number test
+            number_value = await asyncio.wait_for(ha_number_future, timeout=5.0)
+            assert number_value == "42.5", f"Unexpected number value: {number_value}"
+
+            # Wait for completion
+            await asyncio.wait_for(tests_complete_future, timeout=5.0)
+
+            # Now verify the protobuf messages
+            # 1. Basic service call
+            basic_call = await asyncio.wait_for(
+                service_call_futures["light.turn_off"], timeout=2.0
+            )
+            assert basic_call.service == "light.turn_off"
+            assert "entity_id" in basic_call.data, (
+                f"entity_id not found in data: {basic_call.data}"
+            )
+            assert basic_call.data["entity_id"] == "light.test_light", (
+                f"Wrong entity_id: {basic_call.data['entity_id']}"
+            )
+
+            # 2. Templated service call - verify the temporary string issue is fixed
+            templated_call = await asyncio.wait_for(
+                service_call_futures["light.turn_on"], timeout=2.0
+            )
+            assert templated_call.service == "light.turn_on"
+            # Check the computed brightness value
+            assert "brightness" in templated_call.data
+            assert templated_call.data["brightness"] in ["191", "192"]  # 75 * 255 / 100
+            # Check data_template
+            assert "color_name" in templated_call.data_template
+            assert templated_call.data_template["color_name"] == "test_value"
+            # Check variables
+            assert "transition" in templated_call.variables
+            assert templated_call.variables["transition"] == "2.5"
+
+            # 3. Empty string service call
+            empty_call = await asyncio.wait_for(
+                service_call_futures["notify.test"], timeout=2.0
+            )
+            assert empty_call.service == "notify.test"
+            # Verify empty strings are properly handled
+            assert "title" in empty_call.data and empty_call.data["title"] == ""
+            assert (
+                "target" in empty_call.data_template
+                and empty_call.data_template["target"] == ""
+            )
+            assert (
+                "sound" in empty_call.variables and empty_call.variables["sound"] == ""
+            )
+
+            # 4. Multiple fields service call
+            multi_call = await asyncio.wait_for(
+                service_call_futures["climate.set_temperature"], timeout=2.0
+            )
+            assert multi_call.service == "climate.set_temperature"
+            assert multi_call.data["temperature"] == "22"
+            assert multi_call.data["hvac_mode"] == "heat"
+            assert multi_call.data_template["target_temp_high"] == "24"
+            assert multi_call.variables["preset_mode"] == "comfort"
+
+            # 5. Complex lambda service call
+            complex_call = await asyncio.wait_for(
+                service_call_futures["script.test_script"], timeout=2.0
+            )
+            assert complex_call.service == "script.test_script"
+            assert complex_call.data["entity_id"] == "light.living_room"
+            assert complex_call.data["brightness_pct"] == "99"  # 42 * 2.38 ≈ 99
+            # Check message includes sensor value
+            assert "message" in complex_call.data_template
+            assert "Sensor: 42.0" in complex_call.data_template["message"]
+
+            # 6. All empty service call
+            all_empty_call = await asyncio.wait_for(
+                service_call_futures["test.empty"], timeout=2.0
+            )
+            assert all_empty_call.service == "test.empty"
+            # All fields should be empty strings
+            assert all(v == "" for v in all_empty_call.data.values())
+            assert all(v == "" for v in all_empty_call.data_template.values())
+            assert all(v == "" for v in all_empty_call.variables.values())
+
+            # 7. HA Number service call
+            number_call = await asyncio.wait_for(
+                service_call_futures["input_number.set_value"], timeout=2.0
+            )
+            assert number_call.service == "input_number.set_value"
+            assert number_call.data["entity_id"] == "input_number.test_number"
+            # The value might be formatted with trailing zeros
+            assert float(number_call.data["value"]) == 42.5
+
+            # 8. HA Switch service calls
+            switch_on_call = await asyncio.wait_for(
+                service_call_futures["switch.turn_on"], timeout=2.0
+            )
+            assert switch_on_call.service == "switch.turn_on"
+            assert switch_on_call.data["entity_id"] == "switch.test_switch"
+
+            switch_off_call = await asyncio.wait_for(
+                service_call_futures["switch.turn_off"], timeout=2.0
+            )
+            assert switch_off_call.service == "switch.turn_off"
+            assert switch_off_call.data["entity_id"] == "switch.test_switch"
+
+        except TimeoutError as e:
+            # Show recent log lines for debugging
+            recent_logs = "\n".join(log_lines[-20:])
+            service_calls_summary = "\n".join(
+                f"- {call.service}" for call in ha_service_calls
+            )
+            pytest.fail(
+                f"Test timed out waiting for expected log pattern or service call. Error: {e}\n\n"
+                f"Recent log lines:\n{recent_logs}\n\n"
+                f"Received service calls:\n{service_calls_summary}"
+            )