diff --git a/esphome/components/esphome/ota/__init__.py b/esphome/components/esphome/ota/__init__.py
index 72a690b926..e6f249e021 100644
--- a/esphome/components/esphome/ota/__init__.py
+++ b/esphome/components/esphome/ota/__init__.py
@@ -140,13 +140,14 @@ async def to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     cg.add(var.set_port(config[CONF_PORT]))
 
-    # Only include SHA256 support on platforms that have it
-    if supports_sha256():
-        cg.add_define("USE_OTA_SHA256")
-
     if CONF_PASSWORD in config:
         cg.add(var.set_auth_password(config[CONF_PASSWORD]))
         cg.add_define("USE_OTA_PASSWORD")
+        # Only include hash algorithms when password is configured
+        cg.add_define("USE_OTA_MD5")
+        # Only include SHA256 support on platforms that have it
+        if supports_sha256():
+            cg.add_define("USE_OTA_SHA256")
     cg.add_define("USE_OTA_VERSION", config[CONF_VERSION])
 
     await cg.register_component(var, config)
diff --git a/esphome/components/esphome/ota/ota_esphome.cpp b/esphome/components/esphome/ota/ota_esphome.cpp
index 206905d0d8..f503ff795e 100644
--- a/esphome/components/esphome/ota/ota_esphome.cpp
+++ b/esphome/components/esphome/ota/ota_esphome.cpp
@@ -1,6 +1,8 @@
 #include "ota_esphome.h"
 #ifdef USE_OTA
+#ifdef USE_OTA_MD5
 #include "esphome/components/md5/md5.h"
+#endif
 #ifdef USE_OTA_SHA256
 #include "esphome/components/sha256/sha256.h"
 #endif
@@ -267,12 +269,14 @@ void ESPHomeOTAComponent::handle_data_() {
     if (client_supports_sha256) {
       sha256::SHA256 sha_hasher;
       auth_success = this->perform_hash_auth_(&sha_hasher, this->password_, 16, ota::OTA_RESPONSE_REQUEST_SHA256_AUTH,
-                                              LOG_STR("SHA256"));
+                                              LOG_STR("SHA256"), sbuf);
     } else {
+#ifdef USE_OTA_MD5
       ESP_LOGW(TAG, "Using MD5 auth for compatibility (deprecated)");
       md5::MD5Digest md5_hasher;
-      auth_success =
-          this->perform_hash_auth_(&md5_hasher, this->password_, 8, ota::OTA_RESPONSE_REQUEST_AUTH, LOG_STR("MD5"));
+      auth_success = this->perform_hash_auth_(&md5_hasher, this->password_, 8, ota::OTA_RESPONSE_REQUEST_AUTH,
+                                              LOG_STR("MD5"), sbuf);
+#endif  // USE_OTA_MD5
     }
 #else
     // Strict mode: SHA256 required on capable platforms (future default)
@@ -281,13 +285,18 @@ void ESPHomeOTAComponent::handle_data_() {
       error_code = ota::OTA_RESPONSE_ERROR_AUTH_INVALID;
       goto error;  // NOLINT(cppcoreguidelines-avoid-goto)
     }
-    auth_success = this->perform_hash_auth_<sha256::SHA256>(this->password_);
+    sha256::SHA256 sha_hasher;
+    auth_success = this->perform_hash_auth_(&sha_hasher, this->password_, 16, ota::OTA_RESPONSE_REQUEST_SHA256_AUTH,
+                                            LOG_STR("SHA256"), sbuf);
 #endif  // ALLOW_OTA_DOWNGRADE_MD5
 #else
     // Platform only supports MD5 - use it as the only available option
     // This is not a security downgrade as the platform cannot support SHA256
+#ifdef USE_OTA_MD5
     md5::MD5Digest md5_hasher;
-    auth_success = this->perform_hash_auth_(&md5_hasher, this->password_, 8, ota::OTA_RESPONSE_REQUEST_AUTH);
+    auth_success =
+        this->perform_hash_auth_(&md5_hasher, this->password_, 8, ota::OTA_RESPONSE_REQUEST_AUTH, LOG_STR("MD5"), sbuf);
+#endif  // USE_OTA_MD5
 #endif  // USE_OTA_SHA256
 
     if (!auth_success) {
@@ -514,29 +523,24 @@ void ESPHomeOTAComponent::yield_and_feed_watchdog_() {
   delay(1);
 }
 
+#ifdef USE_OTA_PASSWORD
 void ESPHomeOTAComponent::log_auth_warning_(const LogString *action, const LogString *hash_name) {
   ESP_LOGW(TAG, "Auth: %s %s failed", LOG_STR_ARG(action), LOG_STR_ARG(hash_name));
 }
 
 // Non-template function definition to reduce binary size
 bool ESPHomeOTAComponent::perform_hash_auth_(HashBase *hasher, const std::string &password, size_t nonce_size,
-                                             uint8_t auth_request, const LogString *name) {
+                                             uint8_t auth_request, const LogString *name, char *buf) {
   // Get sizes from the hasher
   const size_t hex_size = hasher->get_hex_size();
 
-  // Use fixed-size buffers for the maximum possible hash size (SHA256 = 64 chars)
-  // This avoids dynamic allocation overhead
-  static constexpr size_t MAX_HEX_SIZE = 65;  // SHA256 hex + null terminator
-  char hex_buffer1[MAX_HEX_SIZE];             // Used for: nonce -> expected result
-  char hex_buffer2[MAX_HEX_SIZE];             // Used for: cnonce -> response
+  // Use the provided buffer for all hex operations
 
-  // Small stack buffer for auth request and nonce seed bytes
-  uint8_t buf[1];
+  // Small stack buffer for nonce seed bytes
   uint8_t nonce_bytes[8];  // Max 8 bytes (2 x uint32_t for SHA256)
 
   // Send auth request type
-  buf[0] = auth_request;
-  this->writeall_(buf, 1);
+  this->writeall_(&auth_request, 1);
 
   hasher->init();
 
@@ -562,56 +566,55 @@ bool ESPHomeOTAComponent::perform_hash_auth_(HashBase *hasher, const std::string
   }
   hasher->calculate();
 
-  // Use hex_buffer1 for nonce
-  hasher->get_hex(hex_buffer1);
-  hex_buffer1[hex_size] = '\0';
-  ESP_LOGV(TAG, "Auth: %s Nonce is %s", LOG_STR_ARG(name), hex_buffer1);
+  // Generate and send nonce
+  hasher->get_hex(buf);
+  buf[hex_size] = '\0';
+  ESP_LOGV(TAG, "Auth: %s Nonce is %s", LOG_STR_ARG(name), buf);
 
-  // Send nonce
-  if (!this->writeall_(reinterpret_cast<uint8_t *>(hex_buffer1), hex_size)) {
+  if (!this->writeall_(reinterpret_cast<uint8_t *>(buf), hex_size)) {
     this->log_auth_warning_(LOG_STR("Writing nonce"), name);
     return false;
   }
 
-  // Prepare challenge
+  // Start challenge: password + nonce
   hasher->init();
   hasher->add(password.c_str(), password.length());
-  hasher->add(hex_buffer1, hex_size);  // Add nonce
+  hasher->add(buf, hex_size);
 
-  // Receive cnonce into hex_buffer2
-  if (!this->readall_(reinterpret_cast<uint8_t *>(hex_buffer2), hex_size)) {
+  // Read cnonce and add to hash
+  if (!this->readall_(reinterpret_cast<uint8_t *>(buf), hex_size)) {
     this->log_auth_warning_(LOG_STR("Reading cnonce"), name);
     return false;
   }
-  hex_buffer2[hex_size] = '\0';
-  ESP_LOGV(TAG, "Auth: %s CNonce is %s", LOG_STR_ARG(name), hex_buffer2);
+  buf[hex_size] = '\0';
+  ESP_LOGV(TAG, "Auth: %s CNonce is %s", LOG_STR_ARG(name), buf);
 
-  // Add cnonce to hash
-  hasher->add(hex_buffer2, hex_size);
-
-  // Calculate result - reuse hex_buffer1 for expected
+  hasher->add(buf, hex_size);
   hasher->calculate();
-  hasher->get_hex(hex_buffer1);
-  hex_buffer1[hex_size] = '\0';
-  ESP_LOGV(TAG, "Auth: %s Result is %s", LOG_STR_ARG(name), hex_buffer1);
 
-  // Receive response - reuse hex_buffer2
-  if (!this->readall_(reinterpret_cast<uint8_t *>(hex_buffer2), hex_size)) {
+  // Log expected result (digest is already in hasher)
+  hasher->get_hex(buf);
+  buf[hex_size] = '\0';
+  ESP_LOGV(TAG, "Auth: %s Result is %s", LOG_STR_ARG(name), buf);
+
+  // Read response into the buffer
+  if (!this->readall_(reinterpret_cast<uint8_t *>(buf), hex_size)) {
     this->log_auth_warning_(LOG_STR("Reading response"), name);
     return false;
   }
-  hex_buffer2[hex_size] = '\0';
-  ESP_LOGV(TAG, "Auth: %s Response is %s", LOG_STR_ARG(name), hex_buffer2);
+  buf[hex_size] = '\0';
+  ESP_LOGV(TAG, "Auth: %s Response is %s", LOG_STR_ARG(name), buf);
 
-  // Compare
-  bool matches = memcmp(hex_buffer1, hex_buffer2, hex_size) == 0;
+  // Compare response directly with digest in hasher
+  bool matches = hasher->equals_hex(buf);
 
   if (!matches) {
-    ESP_LOGW(TAG, "Auth failed! %s passwords do not match", LOG_STR_ARG(name));
+    this->log_auth_warning_(LOG_STR("Password mismatch"), name);
   }
 
   return matches;
 }
+#endif  // USE_OTA_PASSWORD
 
 }  // namespace esphome
 #endif
diff --git a/esphome/components/esphome/ota/ota_esphome.h b/esphome/components/esphome/ota/ota_esphome.h
index 5d806028ac..39f2f878de 100644
--- a/esphome/components/esphome/ota/ota_esphome.h
+++ b/esphome/components/esphome/ota/ota_esphome.h
@@ -31,14 +31,16 @@ class ESPHomeOTAComponent : public ota::OTAComponent {
  protected:
   void handle_handshake_();
   void handle_data_();
+#ifdef USE_OTA_PASSWORD
   bool perform_hash_auth_(HashBase *hasher, const std::string &password, size_t nonce_size, uint8_t auth_request,
-                          const LogString *name);
+                          const LogString *name, char *buf);
+  void log_auth_warning_(const LogString *action, const LogString *hash_name);
+#endif  // USE_OTA_PASSWORD
   bool readall_(uint8_t *buf, size_t len);
   bool writeall_(const uint8_t *buf, size_t len);
   void log_socket_error_(const LogString *msg);
   void log_read_error_(const LogString *what);
   void log_start_(const LogString *phase);
-  void log_auth_warning_(const LogString *action, const LogString *hash_name);
   void cleanup_connection_();
   void yield_and_feed_watchdog_();
 
diff --git a/esphome/components/sha256/__init__.py b/esphome/components/sha256/__init__.py
index 91d4929a4f..f07157416d 100644
--- a/esphome/components/sha256/__init__.py
+++ b/esphome/components/sha256/__init__.py
@@ -13,12 +13,10 @@ CONFIG_SCHEMA = cv.Schema({})
 
 async def to_code(config: ConfigType) -> None:
     # Add OpenSSL library for host platform
-    if CORE.is_host:
-        if IS_MACOS:
-            # macOS needs special handling for Homebrew OpenSSL
-            cg.add_build_flag("-I/opt/homebrew/opt/openssl/include")
-            cg.add_build_flag("-L/opt/homebrew/opt/openssl/lib")
-            cg.add_build_flag("-lcrypto")
-        else:
-            # Linux and other Unix systems usually have OpenSSL in standard paths
-            cg.add_build_flag("-lcrypto")
+    if not CORE.is_host:
+        return
+    if IS_MACOS:
+        # macOS needs special handling for Homebrew OpenSSL
+        cg.add_build_flag("-I/opt/homebrew/opt/openssl/include")
+        cg.add_build_flag("-L/opt/homebrew/opt/openssl/lib")
+    cg.add_build_flag("-lcrypto")
diff --git a/esphome/writer.py b/esphome/writer.py
index c0d4379b3a..6d34d8f751 100644
--- a/esphome/writer.py
+++ b/esphome/writer.py
@@ -1,5 +1,6 @@
 import importlib
 import logging
+import os
 from pathlib import Path
 import re
 
@@ -301,6 +302,11 @@ def clean_cmake_cache():
 def clean_build():
     import shutil
 
+    # Allow skipping cache cleaning for integration tests
+    if os.environ.get("ESPHOME_SKIP_CLEAN_BUILD"):
+        _LOGGER.warning("Skipping build cleaning (ESPHOME_SKIP_CLEAN_BUILD set)")
+        return
+
     pioenvs = CORE.relative_pioenvs_path()
     if pioenvs.is_dir():
         _LOGGER.info("Deleting %s", pioenvs)
diff --git a/tests/integration/conftest.py b/tests/integration/conftest.py
index 94632f8439..965363972f 100644
--- a/tests/integration/conftest.py
+++ b/tests/integration/conftest.py
@@ -58,6 +58,8 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
     env["PLATFORMIO_CORE_DIR"] = str(cache_dir)
     env["PLATFORMIO_CACHE_DIR"] = str(cache_dir / ".cache")
     env["PLATFORMIO_LIBDEPS_DIR"] = str(cache_dir / "libdeps")
+    # Prevent cache cleaning during integration tests
+    env["ESPHOME_SKIP_CLEAN_BUILD"] = "1"
     return env
 
 
@@ -68,6 +70,11 @@ def shared_platformio_cache() -> Generator[Path]:
     test_cache_dir = Path.home() / ".esphome-integration-tests"
     cache_dir = test_cache_dir / "platformio"
 
+    # Create the temp directory that PlatformIO uses to avoid race conditions
+    # This ensures it exists and won't be deleted by parallel processes
+    platformio_tmp_dir = cache_dir / ".cache" / "tmp"
+    platformio_tmp_dir.mkdir(parents=True, exist_ok=True)
+
     # Use a lock file in the home directory to ensure only one process initializes the cache
     # This is needed when running with pytest-xdist
     # The lock file must be in a directory that already exists to avoid race conditions
@@ -83,17 +90,11 @@ def shared_platformio_cache() -> Generator[Path]:
             test_cache_dir.mkdir(exist_ok=True)
 
             with tempfile.TemporaryDirectory() as tmpdir:
-                # Create a basic host config
+                # Use the cache_init fixture for initialization
                 init_dir = Path(tmpdir)
+                fixture_path = Path(__file__).parent / "fixtures" / "cache_init.yaml"
                 config_path = init_dir / "cache_init.yaml"
-                config_path.write_text("""esphome:
-  name: cache-init
-host:
-api:
-  encryption:
-    key: "IIevImVI42I0FGos5nLqFK91jrJehrgidI0ArwMLr8w="
-logger:
-""")
+                config_path.write_text(fixture_path.read_text())
 
                 # Run compilation to populate the cache
                 # We must succeed here to avoid race conditions where multiple
@@ -346,7 +347,8 @@ async def wait_and_connect_api_client(
     noise_psk: str | None = None,
     client_info: str = "integration-test",
     timeout: float = API_CONNECTION_TIMEOUT,
-) -> AsyncGenerator[APIClient]:
+    return_disconnect_event: bool = False,
+) -> AsyncGenerator[APIClient | tuple[APIClient, asyncio.Event]]:
     """Wait for API to be available and connect."""
     client = APIClient(
         address=address,
@@ -359,14 +361,17 @@ async def wait_and_connect_api_client(
     # Create a future to signal when connected
     loop = asyncio.get_running_loop()
     connected_future: asyncio.Future[None] = loop.create_future()
+    disconnect_event = asyncio.Event()
 
     async def on_connect() -> None:
         """Called when successfully connected."""
+        disconnect_event.clear()  # Clear the disconnect event on new connection
         if not connected_future.done():
             connected_future.set_result(None)
 
     async def on_disconnect(expected_disconnect: bool) -> None:
         """Called when disconnected."""
+        disconnect_event.set()
         if not connected_future.done() and not expected_disconnect:
             connected_future.set_exception(
                 APIConnectionError("Disconnected before fully connected")
@@ -397,7 +402,10 @@ async def wait_and_connect_api_client(
         except TimeoutError:
             raise TimeoutError(f"Failed to connect to API after {timeout} seconds")
 
-        yield client
+        if return_disconnect_event:
+            yield client, disconnect_event
+        else:
+            yield client
     finally:
         # Stop reconnect logic and disconnect
         await reconnect_logic.stop()
@@ -430,6 +438,33 @@ async def api_client_connected(
     yield _connect_client
 
 
+@pytest_asyncio.fixture
+async def api_client_connected_with_disconnect(
+    unused_tcp_port: int,
+) -> AsyncGenerator:
+    """Factory for creating connected API client context managers with disconnect event."""
+
+    def _connect_client_with_disconnect(
+        address: str = LOCALHOST,
+        port: int | None = None,
+        password: str = "",
+        noise_psk: str | None = None,
+        client_info: str = "integration-test",
+        timeout: float = API_CONNECTION_TIMEOUT,
+    ):
+        return wait_and_connect_api_client(
+            address=address,
+            port=port if port is not None else unused_tcp_port,
+            password=password,
+            noise_psk=noise_psk,
+            client_info=client_info,
+            timeout=timeout,
+            return_disconnect_event=True,
+        )
+
+    yield _connect_client_with_disconnect
+
+
 async def _read_stream_lines(
     stream: asyncio.StreamReader,
     lines: list[str],
diff --git a/tests/integration/fixtures/cache_init.yaml b/tests/integration/fixtures/cache_init.yaml
new file mode 100644
index 0000000000..de208196cd
--- /dev/null
+++ b/tests/integration/fixtures/cache_init.yaml
@@ -0,0 +1,10 @@
+esphome:
+  name: cache-init
+
+host:
+
+api:
+  encryption:
+    key: "IIevImVI42I0FGos5nLqFK91jrJehrgidI0ArwMLr8w="
+
+logger:
diff --git a/tests/integration/fixtures/noise_corrupt_encrypted_frame.yaml b/tests/integration/fixtures/noise_corrupt_encrypted_frame.yaml
new file mode 100644
index 0000000000..6f0266c6fd
--- /dev/null
+++ b/tests/integration/fixtures/noise_corrupt_encrypted_frame.yaml
@@ -0,0 +1,11 @@
+esphome:
+  name: oversized-noise
+
+host:
+
+api:
+  encryption:
+    key: N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU=
+
+logger:
+  level: VERY_VERBOSE
diff --git a/tests/integration/fixtures/oversized_payload_noise.yaml b/tests/integration/fixtures/oversized_payload_noise.yaml
new file mode 100644
index 0000000000..6f0266c6fd
--- /dev/null
+++ b/tests/integration/fixtures/oversized_payload_noise.yaml
@@ -0,0 +1,11 @@
+esphome:
+  name: oversized-noise
+
+host:
+
+api:
+  encryption:
+    key: N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU=
+
+logger:
+  level: VERY_VERBOSE
diff --git a/tests/integration/fixtures/oversized_payload_plaintext.yaml b/tests/integration/fixtures/oversized_payload_plaintext.yaml
new file mode 100644
index 0000000000..44ece4f770
--- /dev/null
+++ b/tests/integration/fixtures/oversized_payload_plaintext.yaml
@@ -0,0 +1,9 @@
+esphome:
+  name: oversized-plaintext
+
+host:
+
+api:
+
+logger:
+  level: VERY_VERBOSE
diff --git a/tests/integration/fixtures/oversized_protobuf_message_id_noise.yaml b/tests/integration/fixtures/oversized_protobuf_message_id_noise.yaml
new file mode 100644
index 0000000000..6f0266c6fd
--- /dev/null
+++ b/tests/integration/fixtures/oversized_protobuf_message_id_noise.yaml
@@ -0,0 +1,11 @@
+esphome:
+  name: oversized-noise
+
+host:
+
+api:
+  encryption:
+    key: N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU=
+
+logger:
+  level: VERY_VERBOSE
diff --git a/tests/integration/fixtures/oversized_protobuf_message_id_plaintext.yaml b/tests/integration/fixtures/oversized_protobuf_message_id_plaintext.yaml
new file mode 100644
index 0000000000..1e9eadfdc5
--- /dev/null
+++ b/tests/integration/fixtures/oversized_protobuf_message_id_plaintext.yaml
@@ -0,0 +1,9 @@
+esphome:
+  name: oversized-protobuf-plaintext
+
+host:
+
+api:
+
+logger:
+  level: VERY_VERBOSE
diff --git a/tests/integration/test_oversized_payloads.py b/tests/integration/test_oversized_payloads.py
new file mode 100644
index 0000000000..f3e422620c
--- /dev/null
+++ b/tests/integration/test_oversized_payloads.py
@@ -0,0 +1,335 @@
+"""Integration tests for oversized payloads and headers that should cause disconnection."""
+
+from __future__ import annotations
+
+import asyncio
+
+import pytest
+
+from .types import APIClientConnectedWithDisconnectFactory, RunCompiledFunction
+
+
+@pytest.mark.asyncio
+async def test_oversized_payload_plaintext(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected_with_disconnect: APIClientConnectedWithDisconnectFactory,
+) -> None:
+    """Test that oversized payloads (>100KiB) from client cause disconnection without crashing."""
+    process_exited = False
+    helper_log_found = False
+
+    def check_logs(line: str) -> None:
+        nonlocal process_exited, helper_log_found
+        # Check for signs that the process exited/crashed
+        if "Segmentation fault" in line or "core dumped" in line:
+            process_exited = True
+        # Check for HELPER_LOG message about message size exceeding maximum
+        if (
+            "[VV]" in line
+            and "Bad packet: message size" in line
+            and "exceeds maximum" in line
+        ):
+            helper_log_found = True
+
+    async with run_compiled(yaml_config, line_callback=check_logs):
+        async with api_client_connected_with_disconnect() as (client, disconnect_event):
+            # Verify basic connection works first
+            device_info = await client.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-plaintext"
+
+            # Create an oversized payload (>100KiB)
+            oversized_data = b"X" * (100 * 1024 + 1)  # 100KiB + 1 byte
+
+            # Access the internal connection to send raw data
+            frame_helper = client._connection._frame_helper
+            # Create a message with oversized payload
+            # Using message type 1 (DeviceInfoRequest) as an example
+            message_type = 1
+            frame_helper.write_packets([(message_type, oversized_data)], True)
+
+            # Wait for the connection to be closed by ESPHome
+            await asyncio.wait_for(disconnect_event.wait(), timeout=5.0)
+
+        # After disconnection, verify process didn't crash
+        assert not process_exited, "ESPHome process should not crash"
+        # Verify we saw the expected HELPER_LOG message
+        assert helper_log_found, (
+            "Expected to see HELPER_LOG about message size exceeding maximum"
+        )
+
+        # Try to reconnect to verify the process is still running
+        async with api_client_connected_with_disconnect() as (client2, _):
+            device_info = await client2.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-plaintext"
+
+
+@pytest.mark.asyncio
+async def test_oversized_protobuf_message_id_plaintext(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected_with_disconnect: APIClientConnectedWithDisconnectFactory,
+) -> None:
+    """Test that protobuf messages with ID > UINT16_MAX cause disconnection without crashing.
+
+    This tests the message type limit - message IDs must fit in a uint16_t (0-65535).
+    """
+    process_exited = False
+    helper_log_found = False
+
+    def check_logs(line: str) -> None:
+        nonlocal process_exited, helper_log_found
+        # Check for signs that the process exited/crashed
+        if "Segmentation fault" in line or "core dumped" in line:
+            process_exited = True
+        # Check for HELPER_LOG message about message type exceeding maximum
+        if (
+            "[VV]" in line
+            and "Bad packet: message type" in line
+            and "exceeds maximum" in line
+        ):
+            helper_log_found = True
+
+    async with run_compiled(yaml_config, line_callback=check_logs):
+        async with api_client_connected_with_disconnect() as (client, disconnect_event):
+            # Verify basic connection works first
+            device_info = await client.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-protobuf-plaintext"
+
+            # Access the internal connection to send raw message with large ID
+            frame_helper = client._connection._frame_helper
+            # Message ID that exceeds uint16_t limit (> 65535)
+            large_message_id = 65536  # 2^16, exceeds UINT16_MAX
+            # Small payload for the test
+            payload = b"test"
+
+            # This should cause disconnection due to oversized varint
+            frame_helper.write_packets([(large_message_id, payload)], True)
+
+            # Wait for the connection to be closed by ESPHome
+            await asyncio.wait_for(disconnect_event.wait(), timeout=5.0)
+
+        # After disconnection, verify process didn't crash
+        assert not process_exited, "ESPHome process should not crash"
+        # Verify we saw the expected HELPER_LOG message
+        assert helper_log_found, (
+            "Expected to see HELPER_LOG about message type exceeding maximum"
+        )
+
+        # Try to reconnect to verify the process is still running
+        async with api_client_connected_with_disconnect() as (client2, _):
+            device_info = await client2.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-protobuf-plaintext"
+
+
+@pytest.mark.asyncio
+async def test_oversized_payload_noise(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected_with_disconnect: APIClientConnectedWithDisconnectFactory,
+) -> None:
+    """Test that oversized payloads (>100KiB) from client cause disconnection without crashing with noise encryption."""
+    noise_key = "N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU="
+    process_exited = False
+    cipherstate_failed = False
+
+    def check_logs(line: str) -> None:
+        nonlocal process_exited, cipherstate_failed
+        # Check for signs that the process exited/crashed
+        if "Segmentation fault" in line or "core dumped" in line:
+            process_exited = True
+        # Check for the expected warning about decryption failure
+        if (
+            "[W][api.connection" in line
+            and "Reading failed CIPHERSTATE_DECRYPT_FAILED" in line
+        ):
+            cipherstate_failed = True
+
+    async with run_compiled(yaml_config, line_callback=check_logs):
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client,
+            disconnect_event,
+        ):
+            # Verify basic connection works first
+            device_info = await client.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
+
+            # Create an oversized payload (>100KiB)
+            oversized_data = b"Y" * (100 * 1024 + 1)  # 100KiB + 1 byte
+
+            # Access the internal connection to send raw data
+            frame_helper = client._connection._frame_helper
+            # For noise connections, we still send through write_packets
+            # but the frame helper will handle encryption
+            # Using message type 1 (DeviceInfoRequest) as an example
+            message_type = 1
+            frame_helper.write_packets([(message_type, oversized_data)], True)
+
+            # Wait for the connection to be closed by ESPHome
+            await asyncio.wait_for(disconnect_event.wait(), timeout=5.0)
+
+        # After disconnection, verify process didn't crash
+        assert not process_exited, "ESPHome process should not crash"
+        # Verify we saw the expected warning message
+        assert cipherstate_failed, (
+            "Expected to see warning about CIPHERSTATE_DECRYPT_FAILED"
+        )
+
+        # Try to reconnect to verify the process is still running
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client2,
+            _,
+        ):
+            device_info = await client2.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
+
+
+@pytest.mark.asyncio
+async def test_oversized_protobuf_message_id_noise(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected_with_disconnect: APIClientConnectedWithDisconnectFactory,
+) -> None:
+    """Test that the noise protocol handles unknown message types correctly.
+
+    With noise encryption, message types are stored as uint16_t (2 bytes) after decryption.
+    Unknown message types should be ignored without disconnecting, as ESPHome needs to
+    read the full message to maintain encryption stream continuity.
+    """
+    noise_key = "N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU="
+    process_exited = False
+
+    def check_logs(line: str) -> None:
+        nonlocal process_exited
+        # Check for signs that the process exited/crashed
+        if "Segmentation fault" in line or "core dumped" in line:
+            process_exited = True
+
+    async with run_compiled(yaml_config, line_callback=check_logs):
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client,
+            disconnect_event,
+        ):
+            # Verify basic connection works first
+            device_info = await client.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
+
+            # With noise, message types are uint16_t, so we test with an unknown but valid value
+            frame_helper = client._connection._frame_helper
+
+            # Test with an unknown message type (65535 is not used by ESPHome)
+            unknown_message_id = 65535  # Valid uint16_t but unknown to ESPHome
+            payload = b"test"
+
+            # Send the unknown message type - ESPHome should read and ignore it
+            frame_helper.write_packets([(unknown_message_id, payload)], True)
+
+            # Give ESPHome a moment to process (but expect no disconnection)
+            # The connection should stay alive as ESPHome ignores unknown message types
+            with pytest.raises(asyncio.TimeoutError):
+                await asyncio.wait_for(disconnect_event.wait(), timeout=0.5)
+
+            # Connection should still be alive - unknown types are ignored, not fatal
+            assert client._connection.is_connected, (
+                "Connection should remain open for unknown message types"
+            )
+
+            # Verify we can still communicate by sending a valid request
+            device_info2 = await client.device_info()
+            assert device_info2 is not None
+            assert device_info2.name == "oversized-noise"
+
+        # After test, verify process didn't crash
+        assert not process_exited, "ESPHome process should not crash"
+
+        # Verify we can still reconnect
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client2,
+            _,
+        ):
+            device_info = await client2.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
+
+
+@pytest.mark.asyncio
+async def test_noise_corrupt_encrypted_frame(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected_with_disconnect: APIClientConnectedWithDisconnectFactory,
+) -> None:
+    """Test that noise protocol properly handles corrupt encrypted frames.
+
+    Send a frame with valid size but corrupt encrypted content (garbage bytes).
+    This should fail decryption and cause disconnection.
+    """
+    noise_key = "N4Yle5YirwZhPiHHsdZLdOA73ndj/84veVaLhTvxCuU="
+    process_exited = False
+    cipherstate_failed = False
+
+    def check_logs(line: str) -> None:
+        nonlocal process_exited, cipherstate_failed
+        # Check for signs that the process exited/crashed
+        if "Segmentation fault" in line or "core dumped" in line:
+            process_exited = True
+        # Check for the expected warning about decryption failure
+        if (
+            "[W][api.connection" in line
+            and "Reading failed CIPHERSTATE_DECRYPT_FAILED" in line
+        ):
+            cipherstate_failed = True
+
+    async with run_compiled(yaml_config, line_callback=check_logs):
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client,
+            disconnect_event,
+        ):
+            # Verify basic connection works first
+            device_info = await client.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
+
+            # Get the socket to send raw corrupt data
+            socket = client._connection._socket
+
+            # Send a corrupt noise frame directly to the socket
+            # Format: [indicator=0x01][size_high][size_low][garbage_encrypted_data]
+            # Size of 32 bytes (reasonable size for a noise frame with MAC)
+            corrupt_frame = bytes(
+                [
+                    0x01,  # Noise indicator
+                    0x00,  # Size high byte
+                    0x20,  # Size low byte (32 bytes)
+                ]
+            ) + bytes(32)  # 32 bytes of zeros (invalid encrypted data)
+
+            # Send the corrupt frame
+            socket.sendall(corrupt_frame)
+
+            # Wait for ESPHome to disconnect due to decryption failure
+            await asyncio.wait_for(disconnect_event.wait(), timeout=5.0)
+
+        # After disconnection, verify process didn't crash
+        assert not process_exited, (
+            "ESPHome process should not crash on corrupt encrypted frames"
+        )
+        # Verify we saw the expected warning message
+        assert cipherstate_failed, (
+            "Expected to see warning about CIPHERSTATE_DECRYPT_FAILED"
+        )
+
+        # Verify we can still reconnect after handling the corrupt frame
+        async with api_client_connected_with_disconnect(noise_psk=noise_key) as (
+            client2,
+            _,
+        ):
+            device_info = await client2.device_info()
+            assert device_info is not None
+            assert device_info.name == "oversized-noise"
diff --git a/tests/integration/types.py b/tests/integration/types.py
index 5e4bfaa29d..b6728a2fcb 100644
--- a/tests/integration/types.py
+++ b/tests/integration/types.py
@@ -54,3 +54,17 @@ class APIClientConnectedFactory(Protocol):
         client_info: str = "integration-test",
         timeout: float = 30,
     ) -> AbstractAsyncContextManager[APIClient]: ...
+
+
+class APIClientConnectedWithDisconnectFactory(Protocol):
+    """Protocol for connected API client factory that returns disconnect event."""
+
+    def __call__(  # noqa: E704
+        self,
+        address: str = "localhost",
+        port: int | None = None,
+        password: str = "",
+        noise_psk: str | None = None,
+        client_info: str = "integration-test",
+        timeout: float = 30,
+    ) -> AbstractAsyncContextManager[tuple[APIClient, asyncio.Event]]: ...
diff --git a/tests/unit_tests/conftest.py b/tests/unit_tests/conftest.py
index e84ba299a2..e8d9c02524 100644
--- a/tests/unit_tests/conftest.py
+++ b/tests/unit_tests/conftest.py
@@ -94,3 +94,10 @@ def mock_run_git_command() -> Generator[Mock, None, None]:
     """Mock run_git_command for git module."""
     with patch("esphome.git.run_git_command") as mock:
         yield mock
+
+
+@pytest.fixture
+def mock_get_idedata() -> Generator[Mock, None, None]:
+    """Mock get_idedata for platformio_api."""
+    with patch("esphome.platformio_api.get_idedata") as mock:
+        yield mock
diff --git a/tests/unit_tests/test_git.py b/tests/unit_tests/test_git.py
index ebe7177bd2..6a51206ec2 100644
--- a/tests/unit_tests/test_git.py
+++ b/tests/unit_tests/test_git.py
@@ -15,7 +15,7 @@ def test_clone_or_update_with_never_refresh(
 ) -> None:
     """Test that NEVER_REFRESH skips updates for existing repos."""
     # Set up CORE.config_path so data_dir uses tmp_path
-    CORE.config_path = str(tmp_path / "test.yaml")
+    CORE.config_path = tmp_path / "test.yaml"
 
     # Compute the expected repo directory path
     url = "https://github.com/test/repo"
@@ -56,7 +56,7 @@ def test_clone_or_update_with_refresh_updates_old_repo(
 ) -> None:
     """Test that refresh triggers update for old repos."""
     # Set up CORE.config_path so data_dir uses tmp_path
-    CORE.config_path = str(tmp_path / "test.yaml")
+    CORE.config_path = tmp_path / "test.yaml"
 
     # Compute the expected repo directory path
     url = "https://github.com/test/repo"
@@ -110,7 +110,7 @@ def test_clone_or_update_with_refresh_skips_fresh_repo(
 ) -> None:
     """Test that refresh doesn't update fresh repos."""
     # Set up CORE.config_path so data_dir uses tmp_path
-    CORE.config_path = str(tmp_path / "test.yaml")
+    CORE.config_path = tmp_path / "test.yaml"
 
     # Compute the expected repo directory path
     url = "https://github.com/test/repo"
@@ -156,7 +156,7 @@ def test_clone_or_update_clones_missing_repo(
 ) -> None:
     """Test that missing repos are cloned regardless of refresh setting."""
     # Set up CORE.config_path so data_dir uses tmp_path
-    CORE.config_path = str(tmp_path / "test.yaml")
+    CORE.config_path = tmp_path / "test.yaml"
 
     # Compute the expected repo directory path
     url = "https://github.com/test/repo"
@@ -198,7 +198,7 @@ def test_clone_or_update_with_none_refresh_always_updates(
 ) -> None:
     """Test that refresh=None always updates existing repos."""
     # Set up CORE.config_path so data_dir uses tmp_path
-    CORE.config_path = str(tmp_path / "test.yaml")
+    CORE.config_path = tmp_path / "test.yaml"
 
     # Compute the expected repo directory path
     url = "https://github.com/test/repo"
diff --git a/tests/unit_tests/test_main.py b/tests/unit_tests/test_main.py
index da280b1fd8..bb047d063c 100644
--- a/tests/unit_tests/test_main.py
+++ b/tests/unit_tests/test_main.py
@@ -12,6 +12,7 @@ from unittest.mock import MagicMock, Mock, patch
 import pytest
 from pytest import CaptureFixture
 
+from esphome import platformio_api
 from esphome.__main__ import (
     Purpose,
     choose_upload_log_host,
@@ -28,7 +29,9 @@ from esphome.__main__ import (
     mqtt_get_ip,
     show_logs,
     upload_program,
+    upload_using_esptool,
 )
+from esphome.components.esp32.const import KEY_ESP32, KEY_VARIANT, VARIANT_ESP32
 from esphome.const import (
     CONF_API,
     CONF_BROKER,
@@ -220,6 +223,14 @@ def mock_run_external_process() -> Generator[Mock]:
         yield mock
 
 
+@pytest.fixture
+def mock_run_external_command() -> Generator[Mock]:
+    """Mock run_external_command for testing."""
+    with patch("esphome.__main__.run_external_command") as mock:
+        mock.return_value = 0  # Default to success
+        yield mock
+
+
 def test_choose_upload_log_host_with_string_default() -> None:
     """Test with a single string default device."""
     setup_core()
@@ -818,6 +829,122 @@ def test_upload_program_serial_esp8266_with_file(
     )
 
 
+def test_upload_using_esptool_path_conversion(
+    tmp_path: Path,
+    mock_run_external_command: Mock,
+    mock_get_idedata: Mock,
+) -> None:
+    """Test upload_using_esptool properly converts Path objects to strings for esptool.
+
+    This test ensures that img.path (Path object) is converted to string before
+    passing to esptool, preventing AttributeError.
+    """
+    setup_core(platform=PLATFORM_ESP32, tmp_path=tmp_path, name="test")
+
+    # Set up ESP32-specific data required by get_esp32_variant()
+    CORE.data[KEY_ESP32] = {KEY_VARIANT: VARIANT_ESP32}
+
+    # Create mock IDEData with Path objects
+    mock_idedata = MagicMock(spec=platformio_api.IDEData)
+    mock_idedata.firmware_bin_path = tmp_path / "firmware.bin"
+    mock_idedata.extra_flash_images = [
+        platformio_api.FlashImage(path=tmp_path / "bootloader.bin", offset="0x1000"),
+        platformio_api.FlashImage(path=tmp_path / "partitions.bin", offset="0x8000"),
+    ]
+
+    mock_get_idedata.return_value = mock_idedata
+
+    # Create the actual firmware files so they exist
+    (tmp_path / "firmware.bin").touch()
+    (tmp_path / "bootloader.bin").touch()
+    (tmp_path / "partitions.bin").touch()
+
+    config = {CONF_ESPHOME: {"platformio_options": {}}}
+
+    # Call upload_using_esptool without custom file argument
+    result = upload_using_esptool(config, "/dev/ttyUSB0", None, None)
+
+    assert result == 0
+
+    # Verify that run_external_command was called
+    assert mock_run_external_command.call_count == 1
+
+    # Get the actual call arguments
+    call_args = mock_run_external_command.call_args[0]
+
+    # The first argument should be esptool.main function,
+    # followed by the command arguments
+    assert len(call_args) > 1
+
+    # Find the indices of the flash image arguments
+    # They should come after "write-flash" and "-z"
+    cmd_list = list(call_args[1:])  # Skip the esptool.main function
+
+    # Verify all paths are strings, not Path objects
+    # The firmware and flash images should be at specific positions
+    write_flash_idx = cmd_list.index("write-flash")
+
+    # After write-flash we have: -z, --flash-size, detect, then offset/path pairs
+    # Check firmware at offset 0x10000 (ESP32)
+    firmware_offset_idx = write_flash_idx + 4
+    assert cmd_list[firmware_offset_idx] == "0x10000"
+    firmware_path = cmd_list[firmware_offset_idx + 1]
+    assert isinstance(firmware_path, str)
+    assert firmware_path.endswith("firmware.bin")
+
+    # Check bootloader
+    bootloader_offset_idx = firmware_offset_idx + 2
+    assert cmd_list[bootloader_offset_idx] == "0x1000"
+    bootloader_path = cmd_list[bootloader_offset_idx + 1]
+    assert isinstance(bootloader_path, str)
+    assert bootloader_path.endswith("bootloader.bin")
+
+    # Check partitions
+    partitions_offset_idx = bootloader_offset_idx + 2
+    assert cmd_list[partitions_offset_idx] == "0x8000"
+    partitions_path = cmd_list[partitions_offset_idx + 1]
+    assert isinstance(partitions_path, str)
+    assert partitions_path.endswith("partitions.bin")
+
+
+def test_upload_using_esptool_with_file_path(
+    tmp_path: Path,
+    mock_run_external_command: Mock,
+) -> None:
+    """Test upload_using_esptool with a custom file that's a Path object."""
+    setup_core(platform=PLATFORM_ESP8266, tmp_path=tmp_path, name="test")
+
+    # Create a test firmware file
+    firmware_file = tmp_path / "custom_firmware.bin"
+    firmware_file.touch()
+
+    config = {CONF_ESPHOME: {"platformio_options": {}}}
+
+    # Call with a Path object as the file argument (though usually it's a string)
+    result = upload_using_esptool(config, "/dev/ttyUSB0", str(firmware_file), None)
+
+    assert result == 0
+
+    # Verify that run_external_command was called
+    mock_run_external_command.assert_called_once()
+
+    # Get the actual call arguments
+    call_args = mock_run_external_command.call_args[0]
+    cmd_list = list(call_args[1:])  # Skip the esptool.main function
+
+    # Find the firmware path in the command
+    write_flash_idx = cmd_list.index("write-flash")
+
+    # For custom file, it should be at offset 0x0
+    firmware_offset_idx = write_flash_idx + 4
+    assert cmd_list[firmware_offset_idx] == "0x0"
+    firmware_path = cmd_list[firmware_offset_idx + 1]
+
+    # Verify it's a string, not a Path object
+    assert isinstance(firmware_path, str)
+    assert firmware_path.endswith("custom_firmware.bin")
+
+
 @pytest.mark.parametrize(
     "platform,device",
     [