diff --git a/tools/cmakev2/kconfig.cmake b/tools/cmakev2/kconfig.cmake
index bc944116b85..a4b08c5a53b 100644
--- a/tools/cmakev2/kconfig.cmake
+++ b/tools/cmakev2/kconfig.cmake
@@ -68,6 +68,32 @@ function(__init_kconfig)
     idf_build_set_property(CONFIG_DIR "${config_dir}")
 endfunction()
 
+#[[
+    __create_sdkconfig_orig_copy()
+
+    Create a copy of the sdkconfig file in the build directory to preserve
+    all original options, including those from managed components that are
+    not yet known to kconfgen. The copy is referenced via __SDKCONFIG_ORIG
+    and used as the --config input for kconfgen, so that unknown options
+    are not dropped during intermediate sdkconfig regeneration rounds.
+
+    After the component manager has fetched all components (and their Kconfig
+    definitions are available), __SDKCONFIG_ORIG is reset to point to the
+    real sdkconfig so that subsequent operations (menuconfig, etc.) read
+    and write the actual file.
+#]]
+function(__create_sdkconfig_orig_copy)
+    idf_build_get_property(sdkconfig SDKCONFIG)
+    idf_build_get_property(build_dir BUILD_DIR)
+    set(sdkconfig_orig "${build_dir}/sdkconfig.orig")
+    if(EXISTS "${sdkconfig}")
+        file(COPY_FILE "${sdkconfig}" "${sdkconfig_orig}" ONLY_IF_DIFFERENT)
+    else()
+        set(sdkconfig_orig "${sdkconfig}")
+    endif()
+    idf_build_set_property(__SDKCONFIG_ORIG "${sdkconfig_orig}")
+endfunction()
+
 #[[
 .. cmakev2:function:: __should_generate_sdkconfig
 
@@ -671,12 +697,20 @@ function(__create_base_kconfgen_command sdkconfig sdkconfig_defaults)
         endforeach()
     endif()
 
+    # Use __SDKCONFIG_ORIG for --config so that unknown options from managed
+    # components are preserved during intermediate kconfgen runs. Falls back
+    # to the real sdkconfig when __SDKCONFIG_ORIG is not yet set.
+    idf_build_get_property(sdkconfig_orig __SDKCONFIG_ORIG)
+    if(NOT sdkconfig_orig)
+        set(sdkconfig_orig "${sdkconfig}")
+    endif()
+
     # Create base kconfgen command
     set(base_kconfgen_cmd ${python} -m kconfgen
         --list-separator=semicolon
         --kconfig "${root_kconfig}"
         --sdkconfig-rename "${root_sdkconfig_rename}"
-        --config "${sdkconfig}"
+        --config "${sdkconfig_orig}"
         ${defaults_args}
         --env "IDF_BUILD_V2=y")
 
diff --git a/tools/cmakev2/manager.cmake b/tools/cmakev2/manager.cmake
index 7bf8d6e6582..c0488e6ec01 100644
--- a/tools/cmakev2/manager.cmake
+++ b/tools/cmakev2/manager.cmake
@@ -83,6 +83,15 @@ function(__fetch_components_from_registry)
             idf_die("IDF Component Manager error: ${cmgr_result}")
         endif()
     endwhile()
+
+    # All managed components are now fetched and their Kconfig definitions
+    # are available. Point __SDKCONFIG_ORIG back to the real sdkconfig so
+    # that subsequent operations (menuconfig, save-defconfig, confserver)
+    # read and write the actual file, not the preserved copy.
+    idf_build_get_property(sdkconfig SDKCONFIG)
+    idf_build_set_property(__SDKCONFIG_ORIG "${sdkconfig}")
+    idf_build_get_property(sdkconfig_defaults SDKCONFIG_DEFAULTS)
+    __create_base_kconfgen_command("${sdkconfig}" "${sdkconfig_defaults}")
 endfunction()
 
 #[[
diff --git a/tools/cmakev2/project.cmake b/tools/cmakev2/project.cmake
index 770d535b0d2..fed486e1575 100644
--- a/tools/cmakev2/project.cmake
+++ b/tools/cmakev2/project.cmake
@@ -581,6 +581,9 @@ macro(idf_project_init)
         # Discover and initialize components
         __init_components()
 
+        # Save original sdkconfig before kconfgen may drop unknown options
+        __create_sdkconfig_orig_copy()
+
         # Generate initial sdkconfig with discovered components
         __generate_sdkconfig()
 
diff --git a/tools/test_build_system/buildv2/__init__.py b/tools/test_build_system/buildv2/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tools/test_build_system/buildv2/test_sdkconfig.py b/tools/test_build_system/buildv2/test_sdkconfig.py
new file mode 100644
index 00000000000..33a0488c65d
--- /dev/null
+++ b/tools/test_build_system/buildv2/test_sdkconfig.py
@@ -0,0 +1,38 @@
+# SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Apache-2.0
+import logging
+from pathlib import Path
+
+from test_build_system_helpers import IdfPyFunc
+from test_build_system_helpers import file_contains
+
+
+def test_sdkconfig_preserves_managed_component_options(idf_py: IdfPyFunc, test_app_copy: Path) -> None:
+    logging.info('sdkconfig options from managed components should be preserved during reconfigure')
+
+    # Create a local managed component outside the project directory.
+    # Since it is referenced via path in idf_component.yml, the component
+    # manager processes it as a managed component whose Kconfig is only
+    # available after the CM run -- i.e. after the initial kconfgen round.
+    managed_comp_dir = test_app_copy / '..' / 'managed_comp'
+    managed_comp_dir.mkdir(parents=True)
+    (managed_comp_dir / 'CMakeLists.txt').write_text('idf_component_register()\n')
+    (managed_comp_dir / 'Kconfig').write_text(
+        'config MANAGED_COMP_TEST_OPTION\n    int "Managed component test option"\n    default 10\n'
+    )
+
+    # Reference the local component as a managed dependency
+    (test_app_copy / 'main' / 'idf_component.yml').write_text(
+        'dependencies:\n  managed_comp:\n    path: "../../managed_comp"\n'
+    )
+
+    # Write a non-default value directly into sdkconfig (not sdkconfig.defaults).
+    # Before the fix, kconfgen would drop this unknown option via --output config
+    # during the first generation round (before the component manager makes the
+    # managed component's Kconfig available), causing the value to revert to the
+    # default (10) in the final sdkconfig.
+    (test_app_copy / 'sdkconfig').write_text('CONFIG_MANAGED_COMP_TEST_OPTION=30\n')
+
+    idf_py('reconfigure')
+
+    assert file_contains(test_app_copy / 'sdkconfig', 'CONFIG_MANAGED_COMP_TEST_OPTION=30')