diff --git a/scripts/snippets/diagnostics.py b/scripts/snippets/diagnostics.py
index 1baf73c18..e75284d53 100644
--- a/scripts/snippets/diagnostics.py
+++ b/scripts/snippets/diagnostics.py
@@ -3,6 +3,8 @@
 from pathlib import Path
 
 from .model import (
+    ConditionStructureIssue,
+    ConditionStructureRule,
     Diagnostic,
     IfVersionAttributeIssue,
     IfVersionAttributeRule,
@@ -41,6 +43,13 @@
     IfVersionAttributeRule.UNREGISTERED_REPOSITORY: "SNIP022",
     IfVersionAttributeRule.INVALID_PULL_REQUEST: "SNIP023",
 }
+IF_VERSION_STRUCTURE_CODES = {
+    ConditionStructureRule.UNEXPECTED_CLOSE: "SNIP012",
+    ConditionStructureRule.ELSE_NOT_DIRECT_CHILD: "SNIP025",
+    ConditionStructureRule.UNCLOSED_TAG: "SNIP026",
+    ConditionStructureRule.MULTIPLE_ELSE: "SNIP029",
+    ConditionStructureRule.ELSE_NOT_FINAL: "SNIP030",
+}
 
 
 def local_source_policy_diagnostic(
@@ -119,3 +128,19 @@ def if_version_attribute_diagnostics(
         )
         for issue in issues
     )
+
+
+def if_version_structure_diagnostics(
+    path: Path, issues: tuple[ConditionStructureIssue, ...]
+) -> tuple[Diagnostic, ...]:
+    """Assign stable diagnostic codes to conditional structure failures."""
+
+    return tuple(
+        Diagnostic(
+            path=path,
+            span=issue.span,
+            code=IF_VERSION_STRUCTURE_CODES[issue.rule],
+            message=issue.message,
+        )
+        for issue in issues
+    )
diff --git a/tests/test_if_version_structure_diagnostics.py b/tests/test_if_version_structure_diagnostics.py
new file mode 100644
index 000000000..a1c519d6f
--- /dev/null
+++ b/tests/test_if_version_structure_diagnostics.py
@@ -0,0 +1,37 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from scripts.snippets.diagnostics import if_version_structure_diagnostics
+from scripts.snippets.model import (
+    ConditionStructureIssue,
+    ConditionStructureRule,
+    Span,
+)
+
+PATH = Path("docs-main/validator.source.mdx")
+SPAN = Span(start=20, end=30, line=7, column=3)
+
+
+@pytest.mark.parametrize(
+    ("rule", "code"),
+    [
+        (ConditionStructureRule.UNEXPECTED_CLOSE, "SNIP012"),
+        (ConditionStructureRule.ELSE_NOT_DIRECT_CHILD, "SNIP025"),
+        (ConditionStructureRule.UNCLOSED_TAG, "SNIP026"),
+        (ConditionStructureRule.MULTIPLE_ELSE, "SNIP029"),
+        (ConditionStructureRule.ELSE_NOT_FINAL, "SNIP030"),
+    ],
+)
+def test_maps_structure_rule_to_stable_code(
+    rule: ConditionStructureRule, code: str
+) -> None:
+    diagnostics = if_version_structure_diagnostics(
+        PATH,
+        (ConditionStructureIssue(rule=rule, span=SPAN, message="failure"),),
+    )
+
+    assert diagnostics[0].code == code
+    assert diagnostics[0].span == SPAN