diff --git a/pm/workspace.py b/pm/workspace.py
index 18316036e1..9d7a652162 100644
--- a/pm/workspace.py
+++ b/pm/workspace.py
@@ -82,7 +82,9 @@ def _copy_core_inputs(source: Path, destination: Path) -> None:
         files.update(str(p.relative_to(source)) for p in source.glob(pattern))
     files.update(p.name for p in source.glob("*.py"))
 
-    excluded = {".git", ".venv", "venv", "node_modules", "__pycache__", "build", "dist", "release", "uv.lock"}
+    # uv.lock is not excluded: the root lock is never copied (only ``files`` are; lock_and_sync
+    # seeds or resolves it), and pm/uv.lock is the PM runtime's input (pm/runtime.py::_inputs).
+    excluded = {".git", ".venv", "venv", "node_modules", "__pycache__", "build", "dist", "release"}
     def ignore(directory, names):
         return [name for name in names if name in excluded or name.startswith(".")
                 or name.endswith(".egg-info") or (Path(directory) / name).is_symlink()]
diff --git a/tests/pm/test_workspace_build_inputs.py b/tests/pm/test_workspace_build_inputs.py
index 70ac8c6c43..468a7b0d04 100644
--- a/tests/pm/test_workspace_build_inputs.py
+++ b/tests/pm/test_workspace_build_inputs.py
@@ -240,3 +240,24 @@ def test_plugin_can_move_compatible_transitive_but_not_exact_requirement(tmp_pat
                                 capture_output=True, text=True, check=True, timeout=30)
         assert result.stdout.strip() == "1.0 1.3"
     assert (baseline / "uv.lock").read_bytes() == first_lock
+
+
+def test_member_uv_lock_travels_with_its_member(tmp_path):
+    """pm/runtime.py::_inputs reads <workspace>/pm/uv.lock; the snapshot must carry it."""
+    core = tmp_path / "core"
+    member = core / "pm"
+    member.mkdir(parents=True)
+    (core / "pyproject.toml").write_text(
+        '[project]\nname="core"\nversion="1"\nrequires-python=">=3.11"\n'
+        '[tool.setuptools.packages.find]\ninclude=["pm"]\n',
+        encoding="utf-8",
+    )
+    (core / "uv.lock").write_text("version = 1\n# root lock\n", encoding="utf-8")
+    (member / "pyproject.toml").write_text('[project]\nname="pm"\nversion="1"\n', encoding="utf-8")
+    (member / "uv.lock").write_text("version = 1\n# member lock\n", encoding="utf-8")
+
+    destination = tmp_path / "stage"
+    workspace._copy_core_inputs(core, destination)
+
+    assert (destination / "pm/uv.lock").read_text(encoding="utf-8") == "version = 1\n# member lock\n"
+    assert not (destination / "uv.lock").exists(), "the root lock is seeded by lock_and_sync, not copied"