diff --git a/.gitlab/ci/test-win.yml b/.gitlab/ci/test-win.yml
index a3a2c3950f..59f0166e5a 100644
--- a/.gitlab/ci/test-win.yml
+++ b/.gitlab/ci/test-win.yml
@@ -146,7 +146,7 @@ pytest_buildv2_system_win:
   extends:
     - .test_build_system_template_win
     - .rules:labels:buildv2
-  parallel: 2
+  parallel: 10
   needs:
     - job: manual_gate
       optional: true
diff --git a/tools/test_build_system/conftest.py b/tools/test_build_system/conftest.py
index 6720a2abe7..1640e84774 100644
--- a/tools/test_build_system/conftest.py
+++ b/tools/test_build_system/conftest.py
@@ -47,7 +47,8 @@ def _create_idf_copy_via_worktree(path_from: Path, path_to: Path) -> str:
     """
     import uuid
 
-    branch_name = f'test-worktree-{uuid.uuid4().hex[:8]}'
+    timestamp = datetime.datetime.now().strftime('%H%M%S')
+    branch_name = f'test-worktree-{timestamp}-{uuid.uuid4().hex[:8]}'
 
     logging.debug(f'creating git worktree at {path_to} (branch: {branch_name})')
     subprocess.run(
diff --git a/tools/test_build_system/test_build.py b/tools/test_build_system/test_build.py
index 2f88c97f12..ef6f0d1c79 100644
--- a/tools/test_build_system/test_build.py
+++ b/tools/test_build_system/test_build.py
@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
+# SPDX-FileCopyrightText: 2022-2026 Espressif Systems (Shanghai) CO LTD
 # SPDX-License-Identifier: Apache-2.0
 import logging
 import os
@@ -17,6 +17,7 @@ from test_build_system_helpers import append_to_file
 from test_build_system_helpers import file_contains
 from test_build_system_helpers import get_idf_build_env
 from test_build_system_helpers import replace_in_file
+from test_build_system_helpers import run_cmake
 from test_build_system_helpers import run_cmake_and_build
 
 
@@ -28,23 +29,22 @@ def assert_built(paths: list[str] | list[Path]) -> None:
 def test_build_alternative_directories(idf_py: IdfPyFunc, func_work_dir: Path, test_app_copy: Path) -> None:
     logging.info('Moving BUILD_DIR_BASE out of tree')
     alt_build_dir = func_work_dir / 'alt_build'
-    try:
-        idf_py('-B', str(alt_build_dir), 'build')
-        assert os.listdir(alt_build_dir) != [], 'No files found in new build directory!'
-        default_build_dir = test_app_copy / 'build'
-        if default_build_dir.exists():
-            assert os.listdir(default_build_dir) == [], (
-                f'Some files were incorrectly put into the default build directory: {default_build_dir}'
-            )
-    except Exception:
-        raise
-    else:
-        shutil.rmtree(alt_build_dir)
+    # Use reconfigure instead of full build - we're testing directory placement, not compilation
+    idf_py('-B', str(alt_build_dir), 'reconfigure')
+    assert os.listdir(alt_build_dir) != [], 'No files found in new build directory!'
+    assert (alt_build_dir / 'CMakeCache.txt').exists(), 'CMakeCache.txt not found in alt build directory!'
+    default_build_dir = test_app_copy / 'build'
+    if default_build_dir.exists():
+        assert os.listdir(default_build_dir) == [], (
+            f'Some files were incorrectly put into the default build directory: {default_build_dir}'
+        )
+    shutil.rmtree(alt_build_dir)
 
     logging.info('BUILD_DIR_BASE inside default build directory')
     build_subdir_inside_build_dir = default_build_dir / 'subdirectory'
-    idf_py('-B', str(build_subdir_inside_build_dir), 'build')
+    idf_py('-B', str(build_subdir_inside_build_dir), 'reconfigure')
     assert os.listdir(build_subdir_inside_build_dir) != [], 'No files found in new build directory!'
+    assert (build_subdir_inside_build_dir / 'CMakeCache.txt').exists(), 'CMakeCache.txt not found in subdirectory!'
 
 
 @pytest.mark.usefixtures('test_app_copy')
@@ -84,30 +84,31 @@ def test_build_with_generator_makefile(idf_py: IdfPyFunc) -> None:
 
 
 def test_build_with_cmake_and_idf_path_unset(idf_py: IdfPyFunc, test_app_copy: Path) -> None:
+    # This test verifies CMake configuration works with various IDF_PATH setups.
+    # We use run_cmake (configure only) instead of full builds for speed.
     idf_path = Path(os.environ['IDF_PATH'])
     env = get_idf_build_env(idf_path)
     env.pop('IDF_PATH')
+    build_dir = test_app_copy / 'build'
 
-    logging.info('Can build with IDF_PATH set via cmake cache not environment')
+    logging.info('Can configure with IDF_PATH set via cmake cache not environment')
     replace_in_file('CMakeLists.txt', 'ENV{IDF_PATH}', '{IDF_PATH}')
-    run_cmake_and_build('-G', 'Ninja', '..', f'-DIDF_PATH={idf_path}', env=env)
-    assert_built(BOOTLOADER_BINS + APP_BINS + PARTITION_BIN)
-    idf_py('fullclean')
+    run_cmake('-G', 'Ninja', '..', f'-DIDF_PATH={idf_path}', env=env)
+    assert (build_dir / 'CMakeCache.txt').exists(), 'CMake configuration failed'
+    shutil.rmtree(build_dir)
 
-    logging.info('Can build with IDF_PATH unset and inferred by cmake when Kconfig needs it to be set')
-    # working with already changed CMakeLists.txt
+    logging.info('Can configure with IDF_PATH unset and inferred by cmake when Kconfig needs it to be set')
     kconfig_file = test_app_copy / 'main' / 'Kconfig.projbuild'
     kconfig_file.write_text('source "$IDF_PATH/examples/wifi/getting_started/station/main/Kconfig.projbuild"')
-    run_cmake_and_build('-G', 'Ninja', '..', f'-DIDF_PATH={idf_path}', env=env)
-    assert_built(BOOTLOADER_BINS + APP_BINS + PARTITION_BIN)
-    kconfig_file.unlink()  # remove file to not affect following sub-test
-    idf_py('fullclean')
+    run_cmake('-G', 'Ninja', '..', f'-DIDF_PATH={idf_path}', env=env)
+    assert (build_dir / 'CMakeCache.txt').exists(), 'CMake configuration failed'
+    kconfig_file.unlink()
+    shutil.rmtree(build_dir)
 
-    logging.info('Can build with IDF_PATH unset and inferred by build system')
-    # replacing {IDF_PATH} not ENV{IDF_PATH} since CMakeLists.txt was already changed in this test
+    logging.info('Can configure with IDF_PATH unset and inferred by build system')
     replace_in_file('CMakeLists.txt', '{IDF_PATH}', '{ci_idf_path}')
-    run_cmake_and_build('-G', 'Ninja', '-D', f'ci_idf_path={idf_path}', '..', env=env)
-    assert_built(BOOTLOADER_BINS + APP_BINS + PARTITION_BIN)
+    run_cmake('-G', 'Ninja', '-D', f'ci_idf_path={idf_path}', '..', env=env)
+    assert (build_dir / 'CMakeCache.txt').exists(), 'CMake configuration failed'
 
 
 def test_build_skdconfig_phy_init_data(idf_py: IdfPyFunc, test_app_copy: Path) -> None:
diff --git a/tools/test_build_system/test_cmake.py b/tools/test_build_system/test_cmake.py
index 5c881c803c..2917babe40 100644
--- a/tools/test_build_system/test_cmake.py
+++ b/tools/test_build_system/test_cmake.py
@@ -19,11 +19,10 @@ from test_build_system_helpers import run_cmake_and_build
 from test_build_system_helpers import run_idf_py
 
 
-# This test checks multiple targets in one test function. It would be better to have each target
-# tested in a isolated test case, but that would mean doing idf_copy each time, and copying takes most of the time
+# This test verifies ESP-IDF can be used as a library in custom CMake projects.
+# We use cmake configure only (not full build) and test representative targets from each arch.
 @pytest.mark.usefixtures('idf_copy')
 def test_build_custom_cmake_project(test_app_copy: Path, request: pytest.FixtureRequest) -> None:
-    # Test is compatible with any target. Random targets in the list are selected for performance reasons
     idf_path = Path(os.environ['IDF_PATH'])
     is_buildv2 = request.config.getoption('buildv2', False)
     if is_buildv2:
@@ -35,9 +34,11 @@ def test_build_custom_cmake_project(test_app_copy: Path, request: pytest.Fixture
         base_cmake_args = ['-G', 'Ninja']
         target_var = 'TARGET'
 
-    for target in ['esp32', 'esp32c2', 'esp32c3', 'esp32c6', 'esp32h2', 'esp32p4', 'esp32s2', 'esp32s3']:
-        logging.info(f'Test build ESP-IDF as a library to a custom CMake projects for {target}')
-        run_cmake_and_build(
+    # Test representative targets: Xtensa (esp32), RISC-V (esp32c3), and newest (esp32p4)
+    for target in ['esp32', 'esp32c3', 'esp32p4']:
+        logging.info(f'Test CMake configuration of ESP-IDF as a library for {target}')
+        # Use run_cmake (configure only) - compile_commands.json is generated during configure
+        run_cmake(
             str(idf_as_lib_path),
             *base_cmake_args,
             '-DCMAKE_TOOLCHAIN_FILE={}'.format(idf_path / 'tools' / 'cmake' / f'toolchain-{target}.cmake'),
@@ -45,9 +46,9 @@ def test_build_custom_cmake_project(test_app_copy: Path, request: pytest.Fixture
         )
         assert file_contains((test_app_copy / 'build' / 'compile_commands.json'), '"command"')
         shutil.rmtree(test_app_copy / 'build')
-        sdkconfig_path = idf_as_lib_path / 'sdkconfig'
-        if sdkconfig_path.exists():
-            os.remove(sdkconfig_path)
+        sdkconfig = idf_as_lib_path / 'sdkconfig'
+        if sdkconfig.exists():
+            sdkconfig.unlink()
 
 
 @pytest.mark.skipif(
diff --git a/tools/test_build_system/test_spaces.py b/tools/test_build_system/test_spaces.py
index 8ef2895031..438bb4853b 100644
--- a/tools/test_build_system/test_spaces.py
+++ b/tools/test_build_system/test_spaces.py
@@ -82,7 +82,7 @@ def test_spaces_bundle3(idf_copy: Path) -> None:
 def test_spaces_bundle4(dummy_: str, idf_py: IdfPyFunc, test_app_copy: Path) -> None:
     logging.info(f'Running test spaces bundle 4 in {test_app_copy}')
     (test_app_copy / 'sdkconfig').write_text('CONFIG_APP_REPRODUCIBLE_BUILD=y')
-    idf_py('reconfigure')
+    idf_py('build')
     (test_app_copy / 'sdkconfig').unlink()
 
     idf_py('set-target', 'esp32s2')