diff --git a/esphome/__main__.py b/esphome/__main__.py
index acb2a9ef46..d9f9ee6333 100644
--- a/esphome/__main__.py
+++ b/esphome/__main__.py
@@ -2784,14 +2784,15 @@ def run_esphome(argv):
     # Skipped when -s overrides are passed, since the cache was written
     # against the previous substitution set.
     config: ConfigType | None = None
-    cache_eligible = (
-        args.command in ("upload", "logs")
-        and not command_line_substitutions
-        # An explicit CLI toolchain must run the per-platform validators;
-        # the cache was validated under whatever the last compile used
-        and args.toolchain is None
+    cache_write_eligible = (
+        args.command in ("upload", "logs") and not command_line_substitutions
     )
-    if cache_eligible:
+    # An explicit CLI toolchain must run the per-platform validators; the
+    # cache was validated under whatever the last compile used. Only the
+    # read is gated: the refresh below may still save the freshly
+    # validated config, and its sidecar records the resolved toolchain.
+    cache_read_eligible = cache_write_eligible and args.toolchain is None
+    if cache_read_eligible:
         from esphome.compiled_config import load_compiled_config
 
         config = load_compiled_config(conf_path)
@@ -2825,7 +2826,7 @@ def run_esphome(argv):
 
     # Refresh the cache so the next upload/logs hits the fast path
     # instead of re-running read_config.
-    if cache_eligible and cache_missed:
+    if cache_write_eligible and cache_missed:
         from esphome.compiled_config import save_compiled_config_and_sidecar
 
         save_compiled_config_and_sidecar(config)
diff --git a/esphome/config_validation.py b/esphome/config_validation.py
index 907e59bac7..102e78b3d9 100644
--- a/esphome/config_validation.py
+++ b/esphome/config_validation.py
@@ -2537,7 +2537,7 @@ def platformio_version_constraint(value):
     return constraints
 
 
-def check_supported_toolchain(
+def _check_supported_toolchain(
     platform_name: str, supported: tuple[Toolchain, ...]
 ) -> None:
     """Raise when the resolved ``CORE.toolchain`` is not in ``supported``.
@@ -2582,7 +2582,7 @@ def resolve_toolchain(
     def validator(config: ConfigType) -> ConfigType:
         if CORE.toolchain is None:
             CORE.toolchain = config.get(CONF_TOOLCHAIN, default)
-        check_supported_toolchain(platform_name, supported)
+        _check_supported_toolchain(platform_name, supported)
         return config
 
     return validator
@@ -2593,8 +2593,11 @@ def require_platformio_toolchain(
 ) -> Callable[[ConfigType], ConfigType]:
     """Reject a CLI-selected toolchain other than PlatformIO.
 
-    For platforms with only the PlatformIO backend; without this a
-    ``--toolchain`` they cannot serve would silently build with PlatformIO.
+    For platforms with only the PlatformIO backend. Without this a
+    ``--toolchain`` they cannot serve would either build with PlatformIO
+    while claiming another backend, or (for a toolchain another platform
+    owns, like ``esp-idf``) dispatch to a native backend that cannot
+    build this platform at all.
     """
     return resolve_toolchain(
         platform_name, (Toolchain.PLATFORMIO,), Toolchain.PLATFORMIO
diff --git a/tests/unit_tests/test_config_validation.py b/tests/unit_tests/test_config_validation.py
index 6f98de2642..9f8633667e 100644
--- a/tests/unit_tests/test_config_validation.py
+++ b/tests/unit_tests/test_config_validation.py
@@ -3191,7 +3191,7 @@ def test_check_supported_toolchain_unresolved_is_an_ordering_bug() -> None:
 
     CORE.toolchain = None
     with pytest.raises(Invalid, match="not resolved before RP2 validation"):
-        cv.check_supported_toolchain("RP2", (Toolchain.PLATFORMIO,))
+        cv._check_supported_toolchain("RP2", (Toolchain.PLATFORMIO,))
 
 
 @pytest.mark.parametrize(
diff --git a/tests/unit_tests/test_main.py b/tests/unit_tests/test_main.py
index a809d3b4c8..8f55daba97 100644
--- a/tests/unit_tests/test_main.py
+++ b/tests/unit_tests/test_main.py
@@ -7429,3 +7429,27 @@ def test_compile_program_unclaimed_native_toolchain_raises(
     CORE.toolchain = Toolchain.ARDUINO  # esp32 has no arduino-native backend
     with pytest.raises(EsphomeError, match="no platform backend claimed"):
         compile_program(MockArgs(), {})
+
+
+def test_cli_toolchain_still_refreshes_the_validated_config_cache(
+    tmp_path: Path,
+) -> None:
+    """An explicit --toolchain gates only the cache read; the freshly
+    validated config is still saved, and its sidecar records the resolved
+    toolchain for a later plain run."""
+    from esphome.__main__ import run_esphome
+
+    conf = tmp_path / "device.yaml"
+    conf.write_text("esphome:\n  name: t\n")
+    argv = ["esphome", "--toolchain", "platformio", "logs", str(conf)]
+    with (
+        patch("esphome.compiled_config.load_compiled_config") as mock_load,
+        patch("esphome.config.read_config", return_value={CONF_ESPHOME: {}}),
+        patch("esphome.compiled_config.save_compiled_config_and_sidecar") as mock_save,
+        patch.dict(
+            "esphome.__main__.POST_CONFIG_ACTIONS", {"logs": Mock(return_value=0)}
+        ),
+    ):
+        assert run_esphome(argv) == 0
+    mock_load.assert_not_called()
+    mock_save.assert_called_once()