diff --git a/internal/verify-map-paint.mjs b/internal/verify-map-paint.mjs
index a124870c5..7c3047935 100644
--- a/internal/verify-map-paint.mjs
+++ b/internal/verify-map-paint.mjs
@@ -89,10 +89,26 @@ for (const url of urls) {
   await page.waitForTimeout(15000)
 
   const r = await page.evaluate(() => {
-    const host = [...document.querySelectorAll('*')].find((e) => e.tagName.includes('-'))
+    // ★ SHADOW DOM DOES NOT PIERCE — walk NESTED roots recursively (fixed 2026-09-20).
+    //   A cap-4/cap-5 COMPOSITE mounts child custom elements, each with its OWN shadow root,
+    //   so the map canvas lives one (or more) levels DOWN. A single-level
+    //   `shadowRoot.querySelector('canvas')` can never see it and reports a perfectly working
+    //   map as "no canvas". That false negative cost three wrong diagnoses of upg-100-mfe:
+    //   "the Map tab is unwired", then "the pane has zero height" — while live measurement
+    //   through nested roots showed a 1280x800 canvas with a live GL context the whole time.
+    //   Flat leaves were unaffected, which is exactly why the blind spot survived: the gate
+    //   passed the four single-level leaves and only lied about composites.
+    const deep = (root, sel, out = []) => {
+      out.push(...root.querySelectorAll(sel))
+      for (const el of root.querySelectorAll('*')) if (el.shadowRoot) deep(el.shadowRoot, sel, out)
+      return out
+    }
+    const host = [...document.querySelectorAll('*')].find((e) => e.tagName.includes('-') && e.shadowRoot)
     const sr = host && host.shadowRoot
     if (!sr) return { shadow: false }
-    const cv = sr.querySelector('canvas')
+    // Prefer a canvas that actually HAS a GL context, at any depth.
+    const canvases = deep(sr, 'canvas')
+    const cv = canvases.find((c) => c.getContext('webgl2') || c.getContext('webgl')) || canvases[0] || null
     // Read ONLY user-visible copy: shadowRoot.textContent includes the injected <style>,
     // which has produced false "unavailable"/"error" matches before.
     const clone = document.createElement('div')
@@ -102,10 +118,12 @@ for (const url of urls) {
     return {
       shadow: true,
       canvas: cv ? cv.width + 'x' + cv.height : null,
+      depth: canvases.length,
       // THE load-bearing assertion: a live GL context, not merely a sized canvas.
       glContext: cv ? !!(cv.getContext('webgl2') || cv.getContext('webgl')) : false,
-      // Mapbox only emits attribution once tiles are actually loading.
-      attribution: /mapbox|openstreetmap/i.test(text),
+      // Mapbox only emits attribution once tiles are actually loading. Search nested roots too:
+      // in a composite the attribution control lives beside the canvas, inside the CHILD's root.
+      attribution: /mapbox|openstreetmap/i.test(text) || deep(sr, '.mapboxgl-ctrl-attrib').length > 0,
       asksForToken: /paste|access token|pk\./i.test(text),
     }
   })