diff -urNP MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/docutil_link_resolution.md MyST-Parser-4.0.1/tests/test_renderers/fixtures/docutil_link_resolution.md
--- MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/docutil_link_resolution.md	2025-02-12 10:49:14.000000000 +0000
+++ MyST-Parser-4.0.1/tests/test_renderers/fixtures/docutil_link_resolution.md	2025-10-02 04:20:54.949806711 +0000
@@ -24,23 +24,23 @@
 .
 <document source="<src>/index.md">
     <paragraph>
-        <reference id_link="True" refid="test">
+        <reference id_link="1" refid="test">
             <system_message level="2" line="1" source="<src>/index.md" type="WARNING">
                 <paragraph>
                     'myst' reference target not found: 'test' [myst.xref_missing]
 
-        <reference id_link="True" refid="test">
+        <reference id_link="1" refid="test">
             <system_message level="2" line="1" source="<src>/index.md" type="WARNING">
                 <paragraph>
                     'myst' reference target not found: 'test' [myst.xref_missing]
 
-        <reference id_link="True" refid="test">
+        <reference id_link="1" refid="test">
             explicit
             <system_message level="2" line="1" source="<src>/index.md" type="WARNING">
                 <paragraph>
                     'myst' reference target not found: 'test' [myst.xref_missing]
 
-        <reference id_link="True" refid="name%20with%20spaces">
+        <reference id_link="1" refid="name%20with%20spaces">
             <system_message level="2" line="1" source="<src>/index.md" type="WARNING">
                 <paragraph>
                     'myst' reference target not found: 'name with spaces' [myst.xref_missing]
@@ -76,15 +76,15 @@
             <title>
                 Non-anchor heading
             <paragraph>
-                <reference id_link="True" refid="title">
+                <reference id_link="1" refid="title">
                     <inline classes="std std-ref">
                         Title
 
-                <reference id_link="True" refid="longer-title-with-nested-syntax">
+                <reference id_link="1" refid="longer-title-with-nested-syntax">
                     <inline classes="std std-ref">
                         Longer title with nested (syntax)
 
-                <reference id_link="True" refid="title">
+                <reference id_link="1" refid="title">
                     explicit
 .
 
@@ -102,15 +102,15 @@
         Test
     <target refid="target">
     <paragraph>
-        <reference id_link="True" refid="target">
+        <reference id_link="1" refid="target">
             <inline classes="std std-ref">
                 Test
 
-        <reference id_link="True" refid="target">
+        <reference id_link="1" refid="target">
             <inline classes="std std-ref">
                 Test
 
-        <reference id_link="True" refid="target">
+        <reference id_link="1" refid="target">
             explicit
 .
 
@@ -128,12 +128,9 @@
         Test
     <subtitle ids="other test-1" names="other test">
         Other
-    <system_message backrefs="test-1" level="1" line="3" source="<src>/index.md" type="INFO">
-        <paragraph>
-            Duplicate implicit target name: "test".
     <target refid="test-1">
     <paragraph>
-        <reference id_link="True" refid="test-1">
+        <reference id_link="1" refid="test-1">
             <inline classes="std std-ref">
                 Other
 .
@@ -150,7 +147,7 @@
     <paragraph ids="name-with-spaces" names="name\ with\ spaces">
         Paragraph
     <paragraph>
-        <reference id_link="True" refid="name-with-spaces">
+        <reference id_link="1" refid="name-with-spaces">
             <inline classes="std std-ref">
                 #name with spaces
 .
@@ -192,14 +189,14 @@
                         <paragraph>
                             d
     <paragraph>
-        <reference id_link="True" refid="table">
+        <reference id_link="1" refid="table">
             <inline classes="std std-ref">
                 caption
 
-        <reference id_link="True" refid="table">
+        <reference id_link="1" refid="table">
             <inline classes="std std-ref">
                 caption
 
-        <reference id_link="True" refid="table">
+        <reference id_link="1" refid="table">
             explicit
 .
diff -urNP MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/docutil_syntax_extensions.txt MyST-Parser-4.0.1/tests/test_renderers/fixtures/docutil_syntax_extensions.txt
--- MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/docutil_syntax_extensions.txt	2025-02-12 10:49:14.000000000 +0000
+++ MyST-Parser-4.0.1/tests/test_renderers/fixtures/docutil_syntax_extensions.txt	2025-10-02 04:20:55.090824403 +0000
@@ -25,12 +25,12 @@
             foo
             bar
          b
-    <math_block nowrap="False" number="True" xml:space="preserve">
+    <math_block nowrap="0" number="True" xml:space="preserve">
         foo
-    <math_block nowrap="False" number="True" xml:space="preserve">
+    <math_block nowrap="0" number="True" xml:space="preserve">
 
         a = 1
-    <math_block ids="label" names="label" nowrap="False" number="True" xml:space="preserve">
+    <math_block ids="label" names="label" nowrap="0" number="True" xml:space="preserve">
 
         b = 2
 .
@@ -48,13 +48,13 @@
 \end{equation*}
 .
 <document source="<string>">
-    <math_block classes="amsmath" nowrap="True" numbered="True" xml:space="preserve">
+    <math_block classes="amsmath" nowrap="1" numbered="1" xml:space="preserve">
         \begin{equation} a \end{equation}
-    <math_block classes="amsmath" nowrap="True" numbered="True" xml:space="preserve">
+    <math_block classes="amsmath" nowrap="1" numbered="1" xml:space="preserve">
         \begin{equation}
         a
         \end{equation}
-    <math_block classes="amsmath" nowrap="True" xml:space="preserve">
+    <math_block classes="amsmath" nowrap="1" xml:space="preserve">
         \begin{equation*}
         a
         \end{equation*}
diff -urNP MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/myst-config.txt MyST-Parser-4.0.1/tests/test_renderers/fixtures/myst-config.txt
--- MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/myst-config.txt	2025-02-12 10:49:14.000000000 +0000
+++ MyST-Parser-4.0.1/tests/test_renderers/fixtures/myst-config.txt	2025-10-02 04:20:55.345046213 +0000
@@ -219,7 +219,7 @@
     <title>
         My title
     <paragraph>
-        <reference id_link="True" refid="my-title">
+        <reference id_link="1" refid="my-title">
             <inline classes="std std-ref">
                 My title
 .
@@ -263,6 +263,12 @@
 <document source="<string>">
     <paragraph>
         a
+    <section classes="system-messages">
+        <title>
+            Docutils System Messages
+        <system_message level="2" source="<string>" type="WARNING">
+            <paragraph>
+                The `attrs_image` extension is deprecated, please use `attrs_inline` instead. [myst.deprecated]
 
 <string>:: (WARNING/2) The `attrs_image` extension is deprecated, please use `attrs_inline` instead. [myst.deprecated]
 .
@@ -381,7 +387,7 @@
             Chris Sewell
 .
 
-[inv_link]
+[inv_link] 
 .
 <inv:#index>
 [](inv:#index)
@@ -397,42 +403,42 @@
 .
 <document source="<string>">
     <paragraph>
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             <emphasis>
                 explicit
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:label:search" reftitle="Python" refuri="https://example.com/search.html">
+        <reference internal="0" inv_match="key:std:label:search" reftitle="Python" refuri="https://example.com/search.html">
             Search Page
 
-        <reference internal="False" inv_match="key:std:label:search" reftitle="Python" refuri="https://example.com/search.html">
+        <reference internal="0" inv_match="key:std:label:search" reftitle="Python" refuri="https://example.com/search.html">
             Search Page
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 
-        <reference internal="False" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
+        <reference internal="0" inv_match="key:std:doc:index" reftitle="Python" refuri="https://example.com/index.html">
             Title
 .
 
-[inv_link_error]
+[inv_link_error] 
 .
 <inv:#other>
 
@@ -447,7 +453,7 @@
         <system_message level="2" line="3" source="<string>" type="WARNING">
             <paragraph>
                 Multiple matches for '*:*:*:*index': key:std:label:genindex, key:std:label:modindex, key:std:label:py-modindex, ... [myst.iref_ambiguous]
-        <reference internal="False" inv_match="key:std:label:genindex" reftitle="Python" refuri="https://example.com/genindex.html">
+        <reference internal="0" inv_match="key:std:label:genindex" reftitle="Python" refuri="https://example.com/genindex.html">
             Index
 
 <string>:1: (WARNING/2) No matches for '*:*:*:other' [myst.iref_missing]
@@ -486,7 +492,7 @@
             <title>
                 other
             <paragraph>
-                <reference id_link="True" refid="title">
+                <reference id_link="1" refid="title">
                     reversed
 .
 
diff -urNP MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/reporter_warnings.md MyST-Parser-4.0.1/tests/test_renderers/fixtures/reporter_warnings.md
--- MyST-Parser-4.0.1.orig/tests/test_renderers/fixtures/reporter_warnings.md	2025-02-12 10:49:14.000000000 +0000
+++ MyST-Parser-4.0.1/tests/test_renderers/fixtures/reporter_warnings.md	2025-10-02 04:20:54.751283034 +0000
@@ -116,7 +116,7 @@
 
 [^a]
 .
-<string>:3: (ERROR/3) Too many autonumbered footnote references: only 0 corresponding footnotes available.
+<string>:3: (ERROR/3) Too many autonumbered footnote references: only 0 corresponding footnote available.
 <string>:1: (ERROR/3) Unknown target name: "1".
 <string>:3: (ERROR/3) Unknown target name: "a".
 .