diff --git a/confluence-mdx/bin/reverse_sync/preserving_patcher.py b/confluence-mdx/bin/reverse_sync/preserving_patcher.py
index 803829a66..0f2d4eeb1 100644
--- a/confluence-mdx/bin/reverse_sync/preserving_patcher.py
+++ b/confluence-mdx/bin/reverse_sync/preserving_patcher.py
@@ -8,7 +8,7 @@
 
 from reverse_sync.models import sha256_text
 from reverse_sync.sidecar import RoundtripSidecar
-from reverse_sync.xhtml_patcher import patch_xhtml
+from reverse_sync.xhtml_patcher import XhtmlPatchError, patch_xhtml
 
 if TYPE_CHECKING:
     from reverse_sync.operations import PatchPlan
@@ -111,7 +111,14 @@ def patch_xhtml_preserving(
     for position, block in enumerate(sidecar.blocks):
         local_patches = fragment_patches.get(position)
         if local_patches:
-            rendered = patch_xhtml(block.xhtml_fragment, local_patches)
+            try:
+                rendered = patch_xhtml(
+                    block.xhtml_fragment,
+                    local_patches,
+                    strict=True,
+                )
+            except XhtmlPatchError as exc:
+                raise PatchApplicationError(str(exc)) from exc
             parts.append(rendered)
         else:
             parts.append(block.xhtml_fragment)
diff --git a/confluence-mdx/bin/reverse_sync/xhtml_patcher.py b/confluence-mdx/bin/reverse_sync/xhtml_patcher.py
index 802f845e3..49672fe5e 100644
--- a/confluence-mdx/bin/reverse_sync/xhtml_patcher.py
+++ b/confluence-mdx/bin/reverse_sync/xhtml_patcher.py
@@ -6,7 +6,16 @@
 from reverse_sync.mapping_recorder import get_text_with_emoticons, iter_block_children
 
 
-def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
+class XhtmlPatchError(ValueError):
+    """strict XHTML renderer가 operation을 정확히 적용하지 못했습니다."""
+
+
+def patch_xhtml(
+    xhtml: str,
+    patches: List[Dict[str, str]],
+    *,
+    strict: bool = False,
+) -> str:
     """XHTML에 패치를 적용한다.
 
     Args:
@@ -22,6 +31,17 @@ def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
         패치된 XHTML 문자열
     """
     soup = BeautifulSoup(xhtml, 'html.parser')
+    supported_actions = {'modify', 'delete', 'insert', 'replace_fragment'}
+    if strict:
+        unsupported = [
+            str(patch.get('action', 'modify'))
+            for patch in patches
+            if patch.get('action', 'modify') not in supported_actions
+        ]
+        if unsupported:
+            raise XhtmlPatchError(
+                f"지원하지 않는 XHTML patch action입니다: {unsupported[0]}"
+            )
 
     # 패치를 action별로 분류
     delete_patches = [p for p in patches if p.get('action') == 'delete']
@@ -34,8 +54,13 @@ def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
     resolved_deletes = []
     for p in delete_patches:
         el = _find_element_by_xpath(soup, p['xhtml_xpath'])
-        if el is not None:
-            resolved_deletes.append(el)
+        if el is None:
+            if strict:
+                raise XhtmlPatchError(
+                    f"delete target을 찾을 수 없습니다: {p['xhtml_xpath']}"
+                )
+            continue
+        resolved_deletes.append(el)
 
     resolved_inserts = []
     for p in insert_patches:
@@ -44,20 +69,34 @@ def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
         if after_xpath is not None:
             anchor = _find_element_by_xpath(soup, after_xpath)
             if anchor is None:
-                continue  # anchor를 못 찾으면 skip
+                if strict:
+                    raise XhtmlPatchError(
+                        f"insert anchor를 찾을 수 없습니다: {after_xpath}"
+                    )
+                continue
         resolved_inserts.append((anchor, p))
 
     resolved_modifies = []
     for p in modify_patches:
         el = _find_element_by_xpath(soup, p['xhtml_xpath'])
-        if el is not None:
-            resolved_modifies.append((el, p))
+        if el is None:
+            if strict:
+                raise XhtmlPatchError(
+                    f"modify target을 찾을 수 없습니다: {p['xhtml_xpath']}"
+                )
+            continue
+        resolved_modifies.append((el, p))
 
     resolved_replacements = []
     for p in replace_patches:
         el = _find_element_by_xpath(soup, p['xhtml_xpath'])
-        if el is not None:
-            resolved_replacements.append((el, p))
+        if el is None:
+            if strict:
+                raise XhtmlPatchError(
+                    f"replace target을 찾을 수 없습니다: {p['xhtml_xpath']}"
+                )
+            continue
+        resolved_replacements.append((el, p))
 
     # 1단계: delete
     for element in resolved_deletes:
@@ -81,6 +120,11 @@ def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
             if old_text and current_plain.strip() != old_text.strip():
                 current_plain_with_emoticons = get_text_with_emoticons(element)
                 if current_plain_with_emoticons.strip() != old_text.strip():
+                    if strict:
+                        raise XhtmlPatchError(
+                            "modify source text가 target fragment와 다릅니다: "
+                            f"{patch['xhtml_xpath']}"
+                        )
                     continue
             _replace_inner_html(element, patch['new_inner_xhtml'])
             if 'ol_start' in patch and isinstance(element, Tag) and element.name == 'ol':
@@ -98,6 +142,11 @@ def patch_xhtml(xhtml: str, patches: List[Dict[str, str]]) -> str:
             if current_plain.strip() != old_text.strip():
                 current_plain_with_emoticons = get_text_with_emoticons(element)
                 if current_plain_with_emoticons.strip() != old_text.strip():
+                    if strict:
+                        raise XhtmlPatchError(
+                            "modify source text가 target fragment와 다릅니다: "
+                            f"{patch['xhtml_xpath']}"
+                        )
                     continue
             _materialize_replaced_emoticons(element, old_text, new_text)
             _apply_text_changes(element, old_text, new_text)
diff --git a/confluence-mdx/tests/test_reverse_sync_equivalence.py b/confluence-mdx/tests/test_reverse_sync_equivalence.py
index 614e65998..72ce55edf 100644
--- a/confluence-mdx/tests/test_reverse_sync_equivalence.py
+++ b/confluence-mdx/tests/test_reverse_sync_equivalence.py
@@ -105,6 +105,28 @@ def test_preserving_patcher_fails_when_exact_target_is_missing():
         raise AssertionError("missing target이 block되지 않았습니다")
 
 
+def test_preserving_patcher_fails_when_fragment_source_text_mismatches():
+    base = "<p>Before</p>"
+    sidecar = build_sidecar(base, "# Title\n\nBefore\n", page_id="123")
+
+    try:
+        patch_xhtml_preserving(
+            base,
+            [
+                {
+                    "xhtml_xpath": "p[1]",
+                    "old_plain_text": "Different source",
+                    "new_plain_text": "After",
+                }
+            ],
+            sidecar,
+        )
+    except PatchApplicationError as exc:
+        assert "source text" in str(exc)
+    else:
+        raise AssertionError("source text mismatch가 block되지 않았습니다")
+
+
 def test_preserving_patcher_keeps_envelope_and_separators_across_insert_delete():
     base = " \n<p>First</p>\n<!-- gap -->\n<p>Second</p>\n "
     original_mdx = "# Title\n\nFirst\n\nSecond\n"
diff --git a/confluence-mdx/tests/test_reverse_sync_xhtml_patcher.py b/confluence-mdx/tests/test_reverse_sync_xhtml_patcher.py
index e453d4886..a4f842c99 100644
--- a/confluence-mdx/tests/test_reverse_sync_xhtml_patcher.py
+++ b/confluence-mdx/tests/test_reverse_sync_xhtml_patcher.py
@@ -1,6 +1,6 @@
 import pytest
 from bs4 import BeautifulSoup
-from reverse_sync.xhtml_patcher import patch_xhtml
+from reverse_sync.xhtml_patcher import XhtmlPatchError, patch_xhtml
 
 
 def test_simple_text_replacement():
@@ -57,6 +57,43 @@ def test_no_change_when_text_not_found():
     assert result == xhtml  # 변경 없음
 
 
+def test_strict_mode_rejects_source_text_mismatch():
+    xhtml = '<p>Original text.</p>'
+    patches = [
+        {
+            'xhtml_xpath': 'p[1]',
+            'old_plain_text': 'Different source.',
+            'new_plain_text': 'Replaced.',
+        }
+    ]
+
+    with pytest.raises(XhtmlPatchError, match='source text'):
+        patch_xhtml(xhtml, patches, strict=True)
+
+
+def test_strict_mode_rejects_unresolved_nested_target():
+    xhtml = '<p>Original text.</p>'
+    patches = [
+        {
+            'xhtml_xpath': 'macro-info[1]/p[1]',
+            'old_plain_text': 'Original text.',
+            'new_plain_text': 'Replaced.',
+        }
+    ]
+
+    with pytest.raises(XhtmlPatchError, match='modify target'):
+        patch_xhtml(xhtml, patches, strict=True)
+
+
+def test_strict_mode_rejects_unknown_action():
+    with pytest.raises(XhtmlPatchError, match='action'):
+        patch_xhtml(
+            '<p>Original text.</p>',
+            [{'action': 'merge', 'xhtml_xpath': 'p[1]'}],
+            strict=True,
+        )
+
+
 def test_compound_xpath_patches_callout_child():
     """복합 xpath로 callout 매크로 내부 자식 요소를 패치한다."""
     xhtml = (
diff --git a/openspec/changes/complete-reverse-sync/design.md b/openspec/changes/complete-reverse-sync/design.md
index a6556a854..d9764c8c7 100644
--- a/openspec/changes/complete-reverse-sync/design.md
+++ b/openspec/changes/complete-reverse-sync/design.md
@@ -324,6 +324,13 @@ sidecar와 다시 비교합니다. CLI와 proof는 raw patch dict를 직접 소
 typed target identity가 바뀌었거나 다른 base에 plan을 적용하려 하면
 `PatchApplicationError`로 중단합니다.
 
+target identity를 통과한 operation은 `xhtml_patcher.patch_xhtml(strict=true)`로
+적용합니다. strict renderer는 rebased target/anchor가 없거나 source visible
+text가 base fragment와 다르거나 action이 미등록이면 조용히 skip하지 않고
+`PatchApplicationError`로 중단합니다. offline diagnostic은 migration fixture
+호환성을 위해 기본 lenient renderer를 계속 사용할 수 있지만 push candidate를
+생성할 수 없습니다.
+
 ### Decision: local proof를 여러 독립 gate로 분해합니다
 
 `verified` 상태는 다음 gate를 모두 통과해야 합니다.
diff --git a/openspec/changes/complete-reverse-sync/tasks.md b/openspec/changes/complete-reverse-sync/tasks.md
index 815057259..fb648cb20 100644
--- a/openspec/changes/complete-reverse-sync/tasks.md
+++ b/openspec/changes/complete-reverse-sync/tasks.md
@@ -181,6 +181,10 @@
   - mapping/sidecar 부재는 `missing_identity`로 정규화하고 같은 intent의 중복
     issue를 제거합니다.
 - [ ] 기존 `xhtml_patcher.py`는 validated operation 적용에 집중하도록 축소합니다.
+  - typed preserving renderer는 `strict=true`로 호출하여 unresolved target,
+    source text mismatch, unknown action을 `PatchApplicationError`로 전환합니다.
+  - offline diagnostic raw patch caller와 legacy helper를 분리하는 작업은 계속
+    남아 있습니다.
 
 완료 gate:
 
@@ -330,10 +334,18 @@ visible segment branch 검증 결과:
 - reverse-sync Python test: 801 passed
 - 전체 Python test: 1124 passed, 2 skipped
 
+strict renderer branch 검증 결과:
+
+- `make test-convert`: 21 passed
+- `make test-reverse-sync`: golden 16 passed, regression 43 passed
+- `make test-byte-verify`: fast/splice 각각 21/21 passed
+- reverse-sync Python test: 805 passed
+- 전체 Python test: 1128 passed, 2 skipped
+
 - [x] 영향도에 따라 전체 Python test와 render test를 실행합니다.
 
-이번 변경은 Python planner/renderer adapter 범위이므로 전체 Python test
-(`1124 passed, 2 skipped`)를 실행했고 frontend render test는 영향 범위에서
+이번 변경은 Python renderer 범위이므로 전체 Python test
+(`1128 passed, 2 skipped`)를 실행했고 frontend render test는 영향 범위에서
 제외했습니다.
 
 ```bash