diff --git a/docs/development/agent-workflow.md b/docs/development/agent-workflow.md
index 567b87c50..109af4ff7 100644
--- a/docs/development/agent-workflow.md
+++ b/docs/development/agent-workflow.md
@@ -57,6 +57,7 @@ Only headings present outside inert HTML containers contribute slugs or duplicat
 Explicit HTML anchors use `parse5`, excluding comments, scripts, styles and template contents.
 Rendered HTML anchor and image-map area hrefs and image sources use the same local-reference checks
 as Markdown links, including decoded attributes and fragment validation.
+Iframe sources are document references and retain Markdown-target anchor checks.
 Image references check file existence without interpreting image fragments as
 Markdown headings; document links keep anchor checks even when sharing a target.
 HTML video, audio, source and track `src` assets and video posters use the same
diff --git a/tools/skills/agent-guidance-markdown.mjs b/tools/skills/agent-guidance-markdown.mjs
index 5ec5943da..4484bd3ef 100644
--- a/tools/skills/agent-guidance-markdown.mjs
+++ b/tools/skills/agent-guidance-markdown.mjs
@@ -71,15 +71,20 @@ function htmlNavigation(html, inspect = () => {}) {
             if (
                 (['a', 'area'].includes(node.tagName) &&
                     attribute.name === 'href') ||
-                (['img', 'video', 'audio', 'source', 'track'].includes(
-                    node.tagName
-                ) &&
+                ([
+                    'img',
+                    'video',
+                    'audio',
+                    'source',
+                    'track',
+                    'iframe',
+                ].includes(node.tagName) &&
                     attribute.name === 'src') ||
                 (node.tagName === 'video' && attribute.name === 'poster')
             )
                 references.push({
                     target: attribute.value,
-                    image: !['a', 'area'].includes(node.tagName),
+                    image: !['a', 'area', 'iframe'].includes(node.tagName),
                 });
             if (
                 ['img', 'source'].includes(node.tagName) &&
diff --git a/tools/skills/validate-agent-guidance.test.mjs b/tools/skills/validate-agent-guidance.test.mjs
index fb23d6960..fc7a6e36c 100644
--- a/tools/skills/validate-agent-guidance.test.mjs
+++ b/tools/skills/validate-agent-guidance.test.mjs
@@ -1170,3 +1170,24 @@ for (const suffix of [',then', ';then', ':then', '!then', '?then']) {
         );
     });
 }
+
+for (const target of ['docs/missing.html', 'docs/example.md#missing']) {
+    test(`iframe document target is validated: ${target}`, async (t) => {
+        assert.ok(
+            (
+                await diagnostics(t, {
+                    'AGENTS.md': `<iframe src="${target}"></iframe>`,
+                })
+            ).length > 0
+        );
+    });
+}
+test('valid iframe and inert iframe targets pass', async (t) => {
+    assert.deepEqual(
+        await diagnostics(t, {
+            'AGENTS.md':
+                '<iframe src="docs/example.md#repeat"></iframe>\n<template><iframe src="missing.html"></iframe></template>',
+        }),
+        []
+    );
+});