diff --git a/archaeology/cli.py b/archaeology/cli.py
index 5242b07..18cba43 100644
--- a/archaeology/cli.py
+++ b/archaeology/cli.py
@@ -83,7 +83,7 @@ def demo(project_name, force, build_db):
         cmd = [sys.executable, "-m", "archaeology.db.builder", "--project-root", str(project_root)]
         _env = os.environ.copy()
         _pkg_root = str(Path(__file__).parent.parent)
-        _env["PYTHONPATH"] = _pkg_root + ((":" + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
+        _env["PYTHONPATH"] = _pkg_root + ((os.pathsep + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
         result = subprocess.run(cmd, check=True, timeout=300, env=_env)
         if result.returncode != 0:
             raise click.exceptions.Exit(result.returncode)
@@ -143,7 +143,7 @@ def build_db(project_name, verbose):
 
     _env = os.environ.copy()
     _pkg_root = str(Path(__file__).parent.parent)
-    _env["PYTHONPATH"] = _pkg_root + ((":" + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
+    _env["PYTHONPATH"] = _pkg_root + ((os.pathsep + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
     result = subprocess.run(cmd, check=True, timeout=300, env=_env)
     if result.returncode == 0 and os.path.exists(db_path):
         click.echo(f"Database built at {db_path}")
@@ -658,7 +658,7 @@ def cascade(project_name, dry_run, skip_mine):
            "--project-root", str(project_dir)]
     _env = os.environ.copy()
     _pkg_root = str(Path(__file__).parent.parent)
-    _env["PYTHONPATH"] = _pkg_root + ((":" + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
+    _env["PYTHONPATH"] = _pkg_root + ((os.pathsep + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
     result = subprocess.run(cmd, capture_output=True, text=True, timeout=300, env=_env)
     if result.returncode == 0:
         click.echo(f"  Database built ({db_path})")
@@ -993,7 +993,7 @@ def sync(projects, skip_mine, skip_signals, verbose):
 
         _env = os.environ.copy()
         _pkg_root = str(Path(__file__).parent.parent)
-        _env["PYTHONPATH"] = _pkg_root + ((":" + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
+        _env["PYTHONPATH"] = _pkg_root + ((os.pathsep + _env["PYTHONPATH"]) if _env.get("PYTHONPATH") else "")
         result = subprocess.run(cmd, capture_output=not verbose, check=True, timeout=300, env=_env)
         if result.returncode == 0 and os.path.exists(db_path):
             click.echo(f"    DB built")
diff --git a/tests/test_cli_coverage.py b/tests/test_cli_coverage.py
index fc7720a..c8825a9 100644
--- a/tests/test_cli_coverage.py
+++ b/tests/test_cli_coverage.py
@@ -14,6 +14,7 @@
 import pytest
 from click.testing import CliRunner
 
+import archaeology.cli as cli
 from archaeology.cli import main
 
 
@@ -397,13 +398,11 @@ def fake_run(cmd, **kwargs):
     assert db_builder_calls, "db.builder was never invoked"
     env = db_builder_calls[0]["env"]
     assert "PYTHONPATH" in env
-    # PYTHONPATH is set to the package root (Path(__file__).parent.parent)
-    # which varies by checkout name — verify it's an absolute path containing
-    # the archaeology package directory, not a hardcoded repo name.
+    # PYTHONPATH is set to the package root (Path(__file__).parent.parent).
+    # Verify that exact path without relying on checkout-specific repo names.
     pp = env["PYTHONPATH"]
-    assert os.path.isabs(pp.split(os.pathsep)[0]), (
-        f"PYTHONPATH should start with an absolute path, got: {pp}"
-    )
+    expected_pkg_root = str(Path(cli.__file__).parent.parent)
+    assert pp.split(os.pathsep)[0] == expected_pkg_root
 
 
 # ── analyze (unknown vector) ──────────────────────────────────────────────────