diff --git a/src/plyngent/tools/workspace.py b/src/plyngent/tools/workspace.py
index 30a8a51..9e4164c 100644
--- a/src/plyngent/tools/workspace.py
+++ b/src/plyngent/tools/workspace.py
@@ -217,10 +217,21 @@ def remove_workspace_allowlist(root: Path | str) -> None:
         _state.allowlist.remove(path)
 
 
-def _under_any_root(resolved: Path) -> bool:
+def _primary_roots() -> list[Path]:
+    """Primary workspace roots: bound instance (if any) then process global."""
     roots: list[Path] = []
-    if _state.root is not None:
+    from plyngent.tools.context import get_instance
+
+    instance = get_instance()
+    if instance is not None and instance.workspace_root is not None:
+        roots.append(instance.workspace_root)
+    if _state.root is not None and _state.root not in roots:
         roots.append(_state.root)
+    return roots
+
+
+def _under_any_root(resolved: Path) -> bool:
+    roots = _primary_roots()
     roots.extend(_state.allowlist)
     for root in roots:
         try:
diff --git a/tests/test_tools/test_workspace_instance.py b/tests/test_tools/test_workspace_instance.py
index fd7602a..cbbab39 100644
--- a/tests/test_tools/test_workspace_instance.py
+++ b/tests/test_tools/test_workspace_instance.py
@@ -11,6 +11,7 @@ from plyngent.tools.workspace import (
     WorkspaceError,
     clear_workspace_root,
     get_workspace_root,
+    resolve_path,
     set_workspace_root,
 )
 
@@ -45,3 +46,15 @@ def test_clear_clears_bound_instance(tmp_path: Path) -> None:
         assert instance.workspace_root is None
         with pytest.raises(WorkspaceError):
             _ = get_workspace_root()
+
+
+def test_resolve_path_accepts_instance_root_without_process_global(tmp_path: Path) -> None:
+    """Instance-only workspace must be a valid resolve root (not only process global)."""
+    clear_workspace_root()
+    target = tmp_path / "note.txt"
+    _ = target.write_text("hi", encoding="utf-8")
+    instance = InstanceState(workspace_root=tmp_path.resolve())
+    with bind_instance(instance):
+        resolved = resolve_path("note.txt")
+        assert resolved == target.resolve()
+    clear_workspace_root()