diff --git a/python/tach/cli.py b/python/tach/cli.py
index 3b76da72..3f0c06d9 100644
--- a/python/tach/cli.py
+++ b/python/tach/cli.py
@@ -8,9 +8,8 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Any
 
-from tach import __version__, cache, icons
+from tach import __version__, cache, extension, icons
 from tach import filesystem as fs
-from tach.check_external import check_external
 from tach.colors import BCOLORS
 from tach.constants import CONFIG_FILE_NAME, TOOL_NAME
 from tach.errors import (
@@ -21,17 +20,7 @@
     TachSetupError,
     TachVisibilityError,
 )
-from tach.extension import (
-    ProjectConfig,
-    check,
-    check_computation_cache,
-    create_computation_cache_key,
-    detect_unused_dependencies,
-    format_diagnostics,
-    run_server,
-    serialize_diagnostics_json,
-    update_computation_cache,
-)
+from tach.extension import ProjectConfig
 from tach.filesystem import install_pre_commit
 from tach.logging import CallInfo, init_logging, logger
 from tach.modularity import export_report, upload_report_to_gauge
@@ -458,7 +447,7 @@ def replay(self):
 def check_cache_for_action(
     project_root: Path, project_config: ProjectConfig, action: str
 ) -> CachedOutput:
-    cache_key = create_computation_cache_key(
+    cache_key = extension.create_computation_cache_key(
         project_root=str(project_root),
         source_roots=[
             str(project_root / source_root)
@@ -470,7 +459,7 @@ def check_cache_for_action(
         env_dependencies=project_config.cache.env_dependencies,
         backend=project_config.cache.backend,
     )
-    cache_result = check_computation_cache(
+    cache_result = extension.check_computation_cache(
         project_root=str(project_root), cache_key=cache_key
     )
     if cache_result:
@@ -503,7 +492,7 @@ def tach_check(
     try:
         exact |= project_config.exact
 
-        diagnostics = check(
+        diagnostics = extension.check(
             project_root=project_root,
             project_config=project_config,
             dependencies=dependencies,
@@ -514,21 +503,25 @@ def tach_check(
 
         if output_format == "json":
             try:
-                print(serialize_diagnostics_json(diagnostics, pretty_print=True))
+                print(
+                    extension.serialize_diagnostics_json(diagnostics, pretty_print=True)
+                )
             except ValueError as e:
                 json.dump({"error": str(e)}, sys.stdout)
             sys.exit(1 if has_errors else 0)
 
         if diagnostics:
             print(
-                format_diagnostics(project_root=project_root, diagnostics=diagnostics),
+                extension.format_diagnostics(
+                    project_root=project_root, diagnostics=diagnostics
+                ),
                 file=sys.stderr,
             )
         exit_code = 1 if has_errors else 0
 
         # If we're checking in exact mode, we want to verify that there are no unused dependencies
         if dependencies and exact:
-            unused_dependencies = detect_unused_dependencies(
+            unused_dependencies = extension.detect_unused_dependencies(
                 project_root=project_root,
                 project_config=project_config,
                 exclude_paths=exclude_paths,
@@ -569,7 +562,7 @@ def tach_check_external(
         },
     )
     try:
-        diagnostics = check_external(
+        diagnostics = extension.check_external_dependencies(
             project_root=project_root,
             project_config=project_config,
             exclude_paths=exclude_paths,
@@ -577,7 +570,9 @@ def tach_check_external(
 
         if diagnostics:
             print(
-                format_diagnostics(project_root=project_root, diagnostics=diagnostics),
+                extension.format_diagnostics(
+                    project_root=project_root, diagnostics=diagnostics
+                ),
                 file=sys.stderr,
             )
 
@@ -907,7 +902,7 @@ def tach_test(
         )
 
         if results.tests_ran_to_completion:
-            update_computation_cache(
+            extension.update_computation_cache(
                 str(project_root),
                 cache_key=cached_output.key,
                 value=(
@@ -1008,7 +1003,7 @@ def tach_server(
             sys.exit(1)
 
     try:
-        run_server(project_root, project_config)
+        extension.run_server(project_root, project_config)
     except TachSetupError as e:
         print(f"Failed to setup LSP server: {e}")
         sys.exit(1)
diff --git a/python/tests/test_cli.py b/python/tests/test_cli.py
index 6ed04640..10309b1f 100644
--- a/python/tests/test_cli.py
+++ b/python/tests/test_cli.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import pathlib
 from pathlib import Path
 from unittest.mock import Mock
 
@@ -8,6 +9,8 @@
 from tach import cli
 from tach.extension import ProjectConfig
 
+_VALID_TACH_TOML = pathlib.Path(__file__).parent / "example" / "valid" / "tach.toml"
+
 
 @pytest.fixture
 def mock_check(mocker) -> Mock:
@@ -64,3 +67,15 @@ def test_execute_with_valid_exclude(capfd, mock_check, mock_project_config):
     assert sys_exit.value.code == 0
     assert "✅" in captured.out
     assert "All modules validated!" in captured.out
+
+
+def test_tach_server_with_config(mocker):
+    mock_run_server = mocker.patch("tach.extension.run_server", autospec=True)
+    cli.tach_server(
+        project_root=Path(),
+        project_config=ProjectConfig(),
+        config_path=_VALID_TACH_TOML,
+    )
+    # Verify server was run with the custom config.
+    mock_run_server.assert_called_once()
+    assert "domain_four.py" in mock_run_server.call_args[0][1].exclude