diff --git a/tools/check_graphrag_rescan.py b/tools/check_graphrag_rescan.py
new file mode 100644
index 0000000..c65038b
--- /dev/null
+++ b/tools/check_graphrag_rescan.py
@@ -0,0 +1,112 @@
+"""GraphRAG rebuilds when it is opened, not every time a project is picked.
+
+Switching project used to rescan the folder, redo the force layout and setHtml
+the whole D3 page immediately — for a tab usually not on screen. With the rail's
+picker one click away from anywhere, that fired constantly, and the rebuild you
+did see on opening GraphRAG read as the page reloading itself.
+"""
+from __future__ import annotations
+
+import os
+import sys
+import time
+
+sys.stdout.reconfigure(encoding="utf-8", errors="replace")
+
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO.parent))
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
+
+from capture_screens import (  # noqa: E402
+    _apply_theme, _freeze_schedulers, _isolate_home, _load_fonts)
+
+
+def main() -> int:
+    sandbox = _isolate_home()
+    from PySide6.QtWidgets import QApplication
+
+    app = QApplication([])
+    _load_fonts()
+    _freeze_schedulers()
+    _apply_theme(app)
+
+    from cowork_local.config import CONFIG_DIR
+    assert str(sandbox) in str(CONFIG_DIR), f"isolation failed: {CONFIG_DIR}"
+
+    from seed_demo_data import seed
+    seed()
+
+    from cowork_local.app import MainWindow
+    from cowork_local.config import AppConfig
+    from cowork_local.i18n import set_language
+    from cowork_local.state import AppContext
+
+    set_language("vi")
+    win = MainWindow(AppContext(AppConfig.load()), user_name="local")
+    win.resize(1600, 950)
+    win.show()
+    app.processEvents()
+    st, w = win.structure, win.workspace
+    fails = []
+
+    # first visit builds the view and scans once
+    win._goto(win._ROW_WORKSPACE, w._graphrag_tab_idx)
+    deadline = time.monotonic() + 30
+    while st._graph is None and time.monotonic() < deadline:
+        app.processEvents()
+        time.sleep(0.02)
+    if st._graph is None:
+        print("FAIL  lan dau khong dung duoc do thi")
+        sys.stdout.flush()
+        os._exit(1)
+
+    calls = {"scan": 0, "html": 0}
+    real_scan, real_html = st._scan, st._render_d3
+    st._scan = lambda: (calls.__setitem__("scan", calls["scan"] + 1), real_scan())[1]
+    st._render_d3 = lambda: (calls.__setitem__("html", calls["html"] + 1), real_html())[1]
+
+    # re-entering an unchanged graph must not rebuild anything
+    for _ in range(3):
+        win._goto(win._ROW_WORKSPACE, w._project_tab_idx)
+        app.processEvents()
+        win._goto(win._ROW_WORKSPACE, w._graphrag_tab_idx)
+        app.processEvents()
+    print(f"vao lai 3 lan (khong doi gi): _scan={calls['scan']} setHtml={calls['html']}")
+    if calls["scan"] or calls["html"]:
+        fails.append("vao lai GraphRAG van quet/reload du khong co gi doi")
+
+    # switching project off-screen defers the work
+    win._goto(win._ROW_WORKSPACE, w._cowork_tab_idx)
+    app.processEvents()
+    ids = [pid for _n, pid in w.project_choices()]
+    for pid in ids[1:3]:
+        w.choose_project(pid)
+        app.processEvents()
+    print(f"doi {len(ids[1:3])} project khi dang o Cowork: _scan={calls['scan']} "
+          f"setHtml={calls['html']} | can quet lan toi={st._needs_scan}")
+    if calls["scan"]:
+        fails.append("doi project van quet ngay du GraphRAG khong tren man")
+    if len(ids) > 1 and not st._needs_scan:
+        fails.append("doi project ma khong danh dau can quet lai")
+
+    # ...and opening it does the work once
+    win._goto(win._ROW_WORKSPACE, w._graphrag_tab_idx)
+    app.processEvents()
+    print(f"mo GraphRAG: _scan={calls['scan']}")
+    if len(ids) > 1 and calls["scan"] != 1:
+        fails.append(f"mo GraphRAG phai quet dung 1 lan, dang {calls['scan']}")
+
+    print()
+    for f in fails:
+        print("FAIL  " + f)
+    print("PASS  GraphRAG chi dung lai do thi khi can" if not fails
+          else f"{len(fails)} problem(s)")
+    sys.stdout.flush()
+    os._exit(1 if fails else 0)
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/ui/structure_graph_view.py b/ui/structure_graph_view.py
index 5d3e6a9..eb7a4c6 100644
--- a/ui/structure_graph_view.py
+++ b/ui/structure_graph_view.py
@@ -404,10 +404,13 @@ class StructureGraphView(QWidget):
             if project is not None:
                 self.path_edit.setText(str(project.workspace_dir()))
         if project_changed:
+            # Mark it and scan on the next visit rather than now. The rail's
+            # project picker made switching a one-click thing from any screen,
+            # and each switch rebuilt this graph — a folder walk plus a force
+            # layout plus a full setHtml of the D3 page — for a tab that was
+            # usually not even on screen. auto_scan_and_fit() picks the flag up
+            # when GraphRAG is actually opened.
             self._needs_scan = True
-            if self.web is not None:
-                self._needs_scan = False
-                self._scan()
 
     # ---- helpers -----------------------------------------------------
     def _pick(self) -> None: