diff --git a/README.md b/README.md
index 51fdafa..01472a5 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,24 @@ JSX attribute nodes have no source position in the MDX AST.
 Use the JSX element position to read its full source with `sourceMap.getRaw(element)`.
 Apply fixes only to mapped Markdown fields. Keep ESM, JSX attributes, and expressions unchanged.
 
+### GFM autolink behavior
+
+The parser uses `remark-gfm` to tokenize GFM autolinks.
+It disables the autolink-literal transform after parsing.
+That transform can create nodes without source positions ([remark-gfm issue #16](https://github.com/remarkjs/remark-gfm/issues/16)).
+Markdown AST nodes must keep their source positions for source maps and fixes.
+
+| Input | AST behavior |
+| --- | --- |
+| `www.example.com` | Link |
+| `<https://example.com>` | Link |
+| `<contact@example.com>` | Link |
+| `visit https://example.com` | Text followed by a link |
+| `"www.google.com"` | Text |
+
+The quoted URL remains text because the tokenizer does not recognize it.
+Other URLs that require the disabled transform also remain text.
+
 ### 序列化说明
 
 `revertMdAstNode` 会将 AST 序列化为 Markdown，但 **不保证恢复原始文本**。
diff --git a/__tests__/plugins/gfm.spec.ts b/__tests__/plugins/gfm.spec.ts
index 77f47a8..d1f6ac9 100644
--- a/__tests__/plugins/gfm.spec.ts
+++ b/__tests__/plugins/gfm.spec.ts
@@ -79,4 +79,37 @@ describe('remark-gfm plugin', () => {
       }
     }
   });
+
+  test('autolink www-prefixed URL', () => {
+    const root = parseMd('www.example.com');
+    const paragraph = root.children[0];
+    expect(paragraph.type).toBe('paragraph');
+    if (paragraph.type === 'paragraph') {
+      expect(paragraph.children).toHaveLength(1);
+      const link = paragraph.children[0];
+      expect(link.type).toBe('link');
+      if (link.type === 'link') {
+        expect(link.url).toContain('www.example.com');
+        expect(link.position.start.offset).toBe(0);
+        expect(link.position.end.offset).toBe('www.example.com'.length);
+      }
+    }
+  });
+
+  test('quoted www URL remains positioned text', () => {
+    const source = '"www.google.com"';
+    const root = parseMd(source);
+    const paragraph = root.children[0];
+    expect(paragraph.type).toBe('paragraph');
+    if (paragraph.type === 'paragraph') {
+      expect(paragraph.children).toHaveLength(1);
+      const text = paragraph.children[0];
+      expect(text.type).toBe('text');
+      if (text.type === 'text') {
+        expect(text.value).toBe(source);
+        expect(text.position.start.offset).toBe(0);
+        expect(text.position.end.offset).toBe(source.length);
+      }
+    }
+  });
 });
diff --git a/__tests__/unit/source-map.spec.ts b/__tests__/unit/source-map.spec.ts
index af80c0b..e1f6f9a 100644
--- a/__tests__/unit/source-map.spec.ts
+++ b/__tests__/unit/source-map.spec.ts
@@ -30,6 +30,24 @@ describe('TypeScript source entry points', () => {
     expect(ast.children[0].type).toBe('heading');
   });
 
+  test('preserves positions and AST parity for quoted www URLs', () => {
+    const source = '"www.google.com"';
+    const ast = parseMd(source);
+    const mapped = parseMdWithSourceMap(source);
+    const text = firstNode(ast, 'text');
+    const mappedText = firstNode(mapped.ast, 'text');
+
+    expect(text.value).toBe(source);
+    expect(text.position.start.offset).toBe(0);
+    expect(text.position.end.offset).toBe(source.length);
+    expect(mappedText.value).toBe(source);
+    expect(mapped.sourceMap.getRaw(mappedText)).toBe(source);
+    expect(mappedText.position.start.offset).toBe(0);
+    expect(mappedText.position.end.offset).toBe(source.length);
+    expect(JSON.parse(JSON.stringify(mapped.ast)))
+      .toEqual(JSON.parse(JSON.stringify(ast)));
+  });
+
   test('maps a plain text value', () => {
     const source = 'Hello world';
     const { ast, sourceMap } = parseMdWithSourceMap(source);