Backend-agnostic dispatch guards, positive native polarity, warn on dropped upload_speed

esphome/__main__.py

@@ -813,9 +813,10 @@ def write_cpp_file() -> int:
         from esphome.build_gen import espidf
 
         espidf.write_project()
-    elif CORE.using_toolchain_arduino:
-        # The ninja project is generated at compile time by
-        # esphome.arduino8266.toolchain (it needs the downloaded framework).
+    elif CORE.using_native_toolchain:
+        # Native builds generate their project at compile time (the ESP8266
+        # ninja build needs the downloaded framework); nothing to write here,
+        # and never a platformio.ini (must agree with _add_platformio_options)
         pass
     else:
         from esphome.build_gen import platformio
@@ -1937,7 +1938,15 @@ def _native_toolchain_module():
         return toolchain
     module = importlib.import_module("esphome.components." + CORE.target_platform)
     get_native = getattr(module, "native_toolchain_module", None)
-    return get_native() if get_native is not None else None
+    native = get_native() if get_native is not None else None
+    if native is None and CORE.using_native_toolchain:
+        # A missing/renamed hook must fail, not silently degrade the native
+        # build's tooling to the PlatformIO path
+        raise EsphomeError(
+            f"Platform {CORE.target_platform} resolved toolchain "
+            f"'{CORE.toolchain.value}' but provides no native toolchain module"
+        )
+    return native
 
 
 def command_idedata(args: ArgsProtocol, config: ConfigType) -> int:
@@ -2000,6 +2009,12 @@ def command_analyze_memory(args: ArgsProtocol, config: ConfigType) -> int:
     idedata = None
     native_toolchain = _native_toolchain_module()
 
+    if native_toolchain is None and not CORE.using_toolchain_platformio:
+        _LOGGER.error(
+            "analyze-memory is not supported with the '%s' toolchain",
+            CORE.toolchain.value if CORE.toolchain else "unresolved",
+        )
+        return 1
     if native_toolchain is not None:
         objdump_path = str(native_toolchain.get_objdump_path())
         readelf_path = str(native_toolchain.get_readelf_path())

esphome/arduino8266/toolchain.py

@@ -23,9 +23,11 @@ _LOGGER = logging.getLogger(__name__)
 # ESP8266 user RAM (matches upload.maximum_ram_size in every board manifest)
 _MAX_RAM_SIZE = 81920
 
-# platformio_options keys the native build consumes (lib_ignore) or that are
-# read from the raw config elsewhere (upload_speed, at upload time)
-_CONSUMED_PIO_OPTIONS = frozenset({"lib_ignore", "upload_speed"})
+# platformio_options keys the native build consumes. YAML-set upload_speed
+# never reaches CORE.platformio_options under the native toolchain (it is
+# read from the raw config at upload time), so anything here came from a
+# component and genuinely is dropped; warn for it.
+_CONSUMED_PIO_OPTIONS = frozenset({"lib_ignore"})
 
 
 _RAM_SECTIONS = (".data", ".rodata", ".bss")

esphome/components/esp8266/__init__.py

@@ -536,7 +536,8 @@ async def finalize_serial_config() -> None:
 # Called by __main__.compile_program; returning False falls through to the
 # PlatformIO toolchain.
 def run_compile(args, config: ConfigType) -> bool:
-    if CORE.using_toolchain_platformio:
+    # Positive check: the native backend only runs when explicitly resolved
+    if not CORE.using_toolchain_arduino:
         return False
     from esphome.arduino8266 import toolchain
 
@@ -547,9 +548,10 @@ def run_compile(args, config: ConfigType) -> bool:
 
 # Called by writer.py
 def copy_files() -> None:
-    if not CORE.using_toolchain_platformio:
-        # The extra scripts are PlatformIO/SCons-only; the native toolchain
-        # applies their logic in the build generator instead.
+    # Positive check, matching run_compile: only the arduino native backend
+    # skips the PlatformIO/SCons extra scripts (their logic lives in the
+    # build generator there)
+    if CORE.using_toolchain_arduino:
         return
     dir = Path(__file__).parent
     for script in (

tests/unit_tests/test_arduino8266_toolchain.py

@@ -336,7 +336,9 @@ def test_warn_ignored_platformio_options(caplog: pytest.LogCaptureFixture) -> No
     assert "platformio_options->board_build.ldscript is ignored" in caplog.text
     assert "native 'arduino' toolchain" in caplog.text
     assert "lib_ignore" not in caplog.text
-    assert "upload_speed" not in caplog.text
+    # Component-added upload_speed never gets read under the native
+    # toolchain, so it must warn
+    assert "upload_speed" in caplog.text
 
 
 def test_run_compile_idedata_error_does_not_fail_build(