diff --git a/scripts/src/hwlab-node-web-observe-runner-sampling-source.test.ts b/scripts/src/hwlab-node-web-observe-runner-sampling-source.test.ts
new file mode 100644
index 00000000..134d21c1
--- /dev/null
+++ b/scripts/src/hwlab-node-web-observe-runner-sampling-source.test.ts
@@ -0,0 +1,24 @@
+import assert from "node:assert/strict";
+import { test } from "bun:test";
+
+import {
+  MDTODO_TASK_TREE_PANE_CONTENT_SELECTOR,
+  nodeWebObserveRunnerSamplingSource,
+} from "./hwlab-node-web-observe-runner-sampling-source";
+
+test("MDTODO task tree pane gap treats the pinned facts footer as content", async () => {
+  assert.match(MDTODO_TASK_TREE_PANE_CONTENT_SELECTOR, /\[data-testid="mdtodo-task-tree-facts"\]/u);
+
+  const source = nodeWebObserveRunnerSamplingSource();
+  assert.ok(source.includes(`measurePaneGap("task-tree", '[data-testid="mdtodo-task-tree"]', ${JSON.stringify(MDTODO_TASK_TREE_PANE_CONTENT_SELECTOR)})`));
+
+  const child = Bun.spawn(["node", "--input-type=module", "--check", "-"], {
+    stdin: "pipe",
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+  child.stdin.write(source);
+  child.stdin.end();
+  const [stderr, exitCode] = await Promise.all([new Response(child.stderr).text(), child.exited]);
+  assert.equal(exitCode, 0, stderr);
+});
diff --git a/scripts/src/hwlab-node-web-observe-runner-sampling-source.ts b/scripts/src/hwlab-node-web-observe-runner-sampling-source.ts
index 33e7a130..c0b6809d 100644
--- a/scripts/src/hwlab-node-web-observe-runner-sampling-source.ts
+++ b/scripts/src/hwlab-node-web-observe-runner-sampling-source.ts
@@ -1,6 +1,19 @@
 // SPEC: PJ2026-01040111 long-running Workbench observation.
 // Responsibility: Runner page sampling, screenshots, DOM digest, response body summaries, and command record source fragment.
 
+export const MDTODO_TASK_TREE_PANE_CONTENT_SELECTOR = [
+  '[data-testid="mdtodo-task-tree-facts"]',
+  "[data-task-ref]",
+  '[role="treeitem"]',
+  '[role="listitem"]',
+  "li",
+  "button",
+  "input",
+  "select",
+  ".task-row-shell",
+  ".task-tools",
+].join(", ");
+
 export function nodeWebObserveRunnerSamplingSource(): string {
   return String.raw`async function preflightSummary() {
   return { currentUrl: currentPageUrl(), title: await page.title().catch(() => null), pageId, auth: publicAuth(auth) };
@@ -461,7 +474,7 @@ async function sampleOnePage(targetPage, { reason, groupSeq, pageRole, targetPag
         };
       };
       const paneGaps = [
-        measurePaneGap("task-tree", '[data-testid="mdtodo-task-tree"]', '[data-task-ref], [role="treeitem"], [role="listitem"], li, button, input, select, .task-row-shell, .task-tools'),
+        measurePaneGap("task-tree", '[data-testid="mdtodo-task-tree"]', ${JSON.stringify(MDTODO_TASK_TREE_PANE_CONTENT_SELECTOR)}),
         measurePaneGap("task-detail", '[data-testid="mdtodo-task-detail"]', '[data-testid="mdtodo-body-rendered"] > *, [data-testid="mdtodo-report-section"], [data-testid="mdtodo-workbench-launch"], [data-testid="mdtodo-delete-task"], [data-testid="mdtodo-task-detail-error"], .mdtodo-detail-header, .task-status-stack > *, .task-document-footer'),
         measurePaneGap("report-sidebar", '[data-testid="mdtodo-report-sidebar"]', '[data-testid="mdtodo-report-preview"] > *, [data-testid="mdtodo-report-error"], [data-testid="mdtodo-report-fullscreen"], [data-testid="mdtodo-report-close"], .report-sidebar-header, .report-preview .markdown-body > *'),
       ];