fix(patch): harden V4A patch parser and fuzzy match — 9 correctness bugs

- Bug 1: replace read_file(limit=10000) with read_file_raw in _apply_update,
  preventing silent truncation of files >2000 lines and corruption of lines
  >2000 chars; add read_file_raw to FileOperations abstract interface and
  ShellFileOperations

- Bug 2: split apply_v4a_operations into validate-then-apply phases; if any
  hunk fails validation, zero writes occur (was: continue after failure,
  leaving filesystem partially modified)

- Bug 3: parse_v4a_patch now returns an error for begin-marker-with-no-ops,
  empty file paths, and moves missing a destination (was: always returned
  error=None)

- Bug 4: raise strategy 7 (block anchor) single-candidate similarity threshold
  from 0.10 to 0.50, eliminating false-positive matches in repetitive code

- Bug 5: add _strategy_unicode_normalized (new strategy 7) with position
  mapping via _build_orig_to_norm_map; smart quotes and em-dashes in
  LLM-generated patches now match via strategies 1-6 before falling through
  to fuzzy strategies

- Bug 6: extend fuzzy_find_and_replace to return 4-tuple (content, count,
  error, strategy); update all 5 call sites across patch_parser.py,
  file_operations.py, and skill_manager_tool.py

- Bug 7: guard in _apply_update returns error when addition-only context hint
  is ambiguous (>1 occurrences); validation phase errors on both 0 and >1

- Bug 8: _apply_delete returns error (not silent success) on missing file

- Bug 9: _validate_operations checks source existence and destination absence
  for MOVE operations before any write occurs

tests/tools/test_file_operations.py

@@ -333,3 +333,25 @@ class TestShellFileOpsWriteDenied:
         result = file_ops.patch_replace("~/.ssh/authorized_keys", "old", "new")
         assert result.error is not None
         assert "denied" in result.error.lower()
+
+    def test_delete_file_denied_path(self, file_ops):
+        result = file_ops.delete_file("~/.ssh/authorized_keys")
+        assert result.error is not None
+        assert "denied" in result.error.lower()
+
+    def test_move_file_src_denied(self, file_ops):
+        result = file_ops.move_file("~/.ssh/id_rsa", "/tmp/dest.txt")
+        assert result.error is not None
+        assert "denied" in result.error.lower()
+
+    def test_move_file_dst_denied(self, file_ops):
+        result = file_ops.move_file("/tmp/src.txt", "~/.aws/credentials")
+        assert result.error is not None
+        assert "denied" in result.error.lower()
+
+    def test_move_file_failure_path(self, mock_env):
+        mock_env.execute.return_value = {"output": "No such file or directory", "returncode": 1}
+        ops = ShellFileOperations(mock_env)
+        result = ops.move_file("/tmp/nonexistent.txt", "/tmp/dest.txt")
+        assert result.error is not None
+        assert "Failed to move" in result.error

tests/tools/test_fuzzy_match.py

@@ -6,31 +6,31 @@ from tools.fuzzy_match import fuzzy_find_and_replace
 class TestExactMatch:
     def test_single_replacement(self):
         content = "hello world"
-        new, count, err = fuzzy_find_and_replace(content, "hello", "hi")
+        new, count, _, err = fuzzy_find_and_replace(content, "hello", "hi")
         assert err is None
         assert count == 1
         assert new == "hi world"
 
     def test_no_match(self):
         content = "hello world"
-        new, count, err = fuzzy_find_and_replace(content, "xyz", "abc")
+        new, count, _, err = fuzzy_find_and_replace(content, "xyz", "abc")
         assert count == 0
         assert err is not None
         assert new == content
 
     def test_empty_old_string(self):
-        new, count, err = fuzzy_find_and_replace("abc", "", "x")
+        new, count, _, err = fuzzy_find_and_replace("abc", "", "x")
         assert count == 0
         assert err is not None
 
     def test_identical_strings(self):
-        new, count, err = fuzzy_find_and_replace("abc", "abc", "abc")
+        new, count, _, err = fuzzy_find_and_replace("abc", "abc", "abc")
         assert count == 0
         assert "identical" in err
 
     def test_multiline_exact(self):
         content = "line1\nline2\nline3"
-        new, count, err = fuzzy_find_and_replace(content, "line1\nline2", "replaced")
+        new, count, _, err = fuzzy_find_and_replace(content, "line1\nline2", "replaced")
         assert err is None
         assert count == 1
         assert new == "replaced\nline3"
@@ -39,7 +39,7 @@ class TestExactMatch:
 class TestWhitespaceDifference:
     def test_extra_spaces_match(self):
         content = "def  foo(  x,  y  ):"
-        new, count, err = fuzzy_find_and_replace(content, "def foo( x, y ):", "def bar(x, y):")
+        new, count, _, err = fuzzy_find_and_replace(content, "def foo( x, y ):", "def bar(x, y):")
         assert count == 1
         assert "bar" in new
 
@@ -47,7 +47,7 @@ class TestWhitespaceDifference:
 class TestIndentDifference:
     def test_different_indentation(self):
         content = "    def foo():\n        pass"
-        new, count, err = fuzzy_find_and_replace(content, "def foo():\n    pass", "def bar():\n    return 1")
+        new, count, _, err = fuzzy_find_and_replace(content, "def foo():\n    pass", "def bar():\n    return 1")
         assert count == 1
         assert "bar" in new
 
@@ -55,13 +55,96 @@ class TestIndentDifference:
 class TestReplaceAll:
     def test_multiple_matches_without_flag_errors(self):
         content = "aaa bbb aaa"
-        new, count, err = fuzzy_find_and_replace(content, "aaa", "ccc", replace_all=False)
+        new, count, _, err = fuzzy_find_and_replace(content, "aaa", "ccc", replace_all=False)
         assert count == 0
         assert "Found 2 matches" in err
 
     def test_multiple_matches_with_flag(self):
         content = "aaa bbb aaa"
-        new, count, err = fuzzy_find_and_replace(content, "aaa", "ccc", replace_all=True)
+        new, count, _, err = fuzzy_find_and_replace(content, "aaa", "ccc", replace_all=True)
         assert err is None
         assert count == 2
         assert new == "ccc bbb ccc"
+
+
+class TestUnicodeNormalized:
+    """Tests for the unicode_normalized strategy (Bug 5)."""
+
+    def test_em_dash_matched(self):
+        """Em-dash in content should match ASCII '--' in pattern."""
+        content = "return value\u2014fallback"
+        new, count, strategy, err = fuzzy_find_and_replace(
+            content, "return value--fallback", "return value or fallback"
+        )
+        assert count == 1, f"Expected match via unicode_normalized, got err={err}"
+        assert strategy == "unicode_normalized"
+        assert "return value or fallback" in new
+
+    def test_smart_quotes_matched(self):
+        """Smart double quotes in content should match straight quotes in pattern."""
+        content = 'print(\u201chello\u201d)'
+        new, count, strategy, err = fuzzy_find_and_replace(
+            content, 'print("hello")', 'print("world")'
+        )
+        assert count == 1, f"Expected match via unicode_normalized, got err={err}"
+        assert "world" in new
+
+    def test_no_unicode_skips_strategy(self):
+        """When content and pattern have no Unicode variants, strategy is skipped."""
+        content = "hello world"
+        # Should match via exact, not unicode_normalized
+        new, count, strategy, err = fuzzy_find_and_replace(content, "hello", "hi")
+        assert count == 1
+        assert strategy == "exact"
+
+
+class TestBlockAnchorThreshold:
+    """Tests for the raised block_anchor threshold (Bug 4)."""
+
+    def test_high_similarity_matches(self):
+        """A block with >50% middle similarity should match."""
+        content = "def foo():\n    x = 1\n    y = 2\n    return x + y\n"
+        pattern = "def foo():\n    x = 1\n    y = 9\n    return x + y"
+        new, count, strategy, err = fuzzy_find_and_replace(content, pattern, "def foo():\n    return 0\n")
+        # Should match via block_anchor or earlier strategy
+        assert count == 1
+
+    def test_completely_different_middle_does_not_match(self):
+        """A block where only first+last lines match but middle is completely different
+        should NOT match under the raised 0.50 threshold."""
+        content = (
+            "class Foo:\n"
+            "    completely = 'unrelated'\n"
+            "    content = 'here'\n"
+            "    nothing = 'in common'\n"
+            "    pass\n"
+        )
+        # Pattern has same first/last lines but completely different middle
+        pattern = (
+            "class Foo:\n"
+            "    x = 1\n"
+            "    y = 2\n"
+            "    z = 3\n"
+            "    pass"
+        )
+        new, count, strategy, err = fuzzy_find_and_replace(content, pattern, "replaced")
+        # With threshold=0.50, this near-zero-similarity middle should not match
+        assert count == 0, (
+            f"Block with unrelated middle should not match under threshold=0.50, "
+            f"but matched via strategy={strategy}"
+        )
+
+
+class TestStrategyNameSurfaced:
+    """Tests for the strategy name in the 4-tuple return (Bug 6)."""
+
+    def test_exact_strategy_name(self):
+        new, count, strategy, err = fuzzy_find_and_replace("hello", "hello", "world")
+        assert strategy == "exact"
+        assert count == 1
+
+    def test_failed_match_returns_none_strategy(self):
+        new, count, strategy, err = fuzzy_find_and_replace("hello", "xyz", "world")
+        assert count == 0
+        assert strategy is None
+        assert err is not None

tests/tools/test_patch_parser.py

@@ -159,7 +159,7 @@ class TestApplyUpdate:
             def __init__(self):
                 self.written = None
 
-            def read_file(self, path, offset=1, limit=500):
+            def read_file_raw(self, path):
                 return SimpleNamespace(
                     content=(
                         'def run():\n'
@@ -211,7 +211,7 @@ class TestAdditionOnlyHunks:
         # Apply to a file that contains the context hint
         class FakeFileOps:
             written = None
-            def read_file(self, path, **kw):
+            def read_file_raw(self, path):
                 return SimpleNamespace(
                     content="def main():\n    pass\n",
                     error=None,
@@ -239,7 +239,7 @@ class TestAdditionOnlyHunks:
 
         class FakeFileOps:
             written = None
-            def read_file(self, path, **kw):
+            def read_file_raw(self, path):
                 return SimpleNamespace(
                     content="existing = True\n",
                     error=None,
@@ -253,3 +253,259 @@ class TestAdditionOnlyHunks:
         assert result.success is True
         assert file_ops.written.endswith("def new_func():\n    return True\n")
         assert "existing = True" in file_ops.written
+
+
+class TestReadFileRaw:
+    """Bug 1 regression tests — files > 2000 lines and lines > 2000 chars."""
+
+    def test_apply_update_file_over_2000_lines(self):
+        """A hunk targeting line 2200 must not truncate the file to 2000 lines."""
+        patch = """\
+*** Begin Patch
+*** Update File: big.py
+@@ marker_at_2200 @@
+ line_2200
+-old_value
++new_value
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        # Build a 2500-line file; the hunk targets a region at line 2200
+        lines = [f"line_{i}" for i in range(1, 2501)]
+        lines[2199] = "line_2200"   # index 2199 = line 2200
+        lines[2200] = "old_value"
+        file_content = "\n".join(lines)
+
+        class FakeFileOps:
+            written = None
+            def read_file_raw(self, path):
+                return SimpleNamespace(content=file_content, error=None)
+            def write_file(self, path, content):
+                self.written = content
+                return SimpleNamespace(error=None)
+
+        file_ops = FakeFileOps()
+        result = apply_v4a_operations(ops, file_ops)
+        assert result.success is True
+        written_lines = file_ops.written.split("\n")
+        assert len(written_lines) == 2500, (
+            f"Expected 2500 lines, got {len(written_lines)}"
+        )
+        assert "new_value" in file_ops.written
+        assert "old_value" not in file_ops.written
+
+    def test_apply_update_preserves_long_lines(self):
+        """A line > 2000 chars must be preserved verbatim after an unrelated hunk."""
+        long_line = "x" * 3000
+        patch = """\
+*** Begin Patch
+*** Update File: wide.py
+@@ short_func @@
+ def short_func():
+-    return 1
++    return 2
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        file_content = f"def short_func():\n    return 1\n{long_line}\n"
+
+        class FakeFileOps:
+            written = None
+            def read_file_raw(self, path):
+                return SimpleNamespace(content=file_content, error=None)
+            def write_file(self, path, content):
+                self.written = content
+                return SimpleNamespace(error=None)
+
+        file_ops = FakeFileOps()
+        result = apply_v4a_operations(ops, file_ops)
+        assert result.success is True
+        assert long_line in file_ops.written, "Long line was truncated"
+        assert "... [truncated]" not in file_ops.written
+
+
+class TestValidationPhase:
+    """Bug 2 regression tests — validation prevents partial apply."""
+
+    def test_validation_failure_writes_nothing(self):
+        """If one hunk is invalid, no files should be written."""
+        patch = """\
+*** Begin Patch
+*** Update File: a.py
+ def good():
+-    return 1
++    return 2
+*** Update File: b.py
+ THIS LINE DOES NOT EXIST
+-    old
++    new
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        written = {}
+
+        class FakeFileOps:
+            def read_file_raw(self, path):
+                files = {
+                    "a.py": "def good():\n    return 1\n",
+                    "b.py": "completely different content\n",
+                }
+                content = files.get(path)
+                if content is None:
+                    return SimpleNamespace(content=None, error=f"File not found: {path}")
+                return SimpleNamespace(content=content, error=None)
+
+            def write_file(self, path, content):
+                written[path] = content
+                return SimpleNamespace(error=None)
+
+        result = apply_v4a_operations(ops, FakeFileOps())
+        assert result.success is False
+        assert written == {}, f"No files should have been written, got: {list(written.keys())}"
+        assert "validation failed" in result.error.lower()
+
+    def test_all_valid_operations_applied(self):
+        """When all operations are valid, all files are written."""
+        patch = """\
+*** Begin Patch
+*** Update File: a.py
+ def foo():
+-    return 1
++    return 2
+*** Update File: b.py
+ def bar():
+-    pass
++    return True
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        written = {}
+
+        class FakeFileOps:
+            def read_file_raw(self, path):
+                files = {
+                    "a.py": "def foo():\n    return 1\n",
+                    "b.py": "def bar():\n    pass\n",
+                }
+                return SimpleNamespace(content=files[path], error=None)
+
+            def write_file(self, path, content):
+                written[path] = content
+                return SimpleNamespace(error=None)
+
+        result = apply_v4a_operations(ops, FakeFileOps())
+        assert result.success is True
+        assert set(written.keys()) == {"a.py", "b.py"}
+
+
+class TestApplyDelete:
+    """Tests for _apply_delete producing a real unified diff."""
+
+    def test_delete_diff_contains_removed_lines(self):
+        """_apply_delete must embed the actual file content in the diff, not a placeholder."""
+        patch = """\
+*** Begin Patch
+*** Delete File: old/stuff.py
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        class FakeFileOps:
+            deleted = False
+
+            def read_file_raw(self, path):
+                return SimpleNamespace(
+                    content="def old_func():\n    return 42\n",
+                    error=None,
+                )
+
+            def delete_file(self, path):
+                self.deleted = True
+                return SimpleNamespace(error=None)
+
+        file_ops = FakeFileOps()
+        result = apply_v4a_operations(ops, file_ops)
+
+        assert result.success is True
+        assert file_ops.deleted is True
+        # Diff must contain the actual removed lines, not a bare comment
+        assert "-def old_func():" in result.diff
+        assert "-    return 42" in result.diff
+        assert "/dev/null" in result.diff
+
+    def test_delete_diff_fallback_on_empty_file(self):
+        """An empty file should produce the fallback comment diff."""
+        patch = """\
+*** Begin Patch
+*** Delete File: empty.py
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+
+        class FakeFileOps:
+            def read_file_raw(self, path):
+                return SimpleNamespace(content="", error=None)
+
+            def delete_file(self, path):
+                return SimpleNamespace(error=None)
+
+        result = apply_v4a_operations(ops, FakeFileOps())
+        assert result.success is True
+        # unified_diff produces nothing for two empty inputs — fallback comment expected
+        assert "Deleted" in result.diff or result.diff.strip() == ""
+
+
+class TestCountOccurrences:
+    def test_basic(self):
+        from tools.patch_parser import _count_occurrences
+        assert _count_occurrences("aaa", "a") == 3
+        assert _count_occurrences("aaa", "aa") == 2
+        assert _count_occurrences("hello world", "xyz") == 0
+        assert _count_occurrences("", "x") == 0
+
+
+class TestParseErrorSignalling:
+    """Bug 3 regression tests — parse_v4a_patch must signal errors, not swallow them."""
+
+    def test_update_with_no_hunks_returns_error(self):
+        """An UPDATE with no hunk lines is a malformed patch and should error."""
+        patch = """\
+*** Begin Patch
+*** Update File: foo.py
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is not None, "Expected a parse error for hunk-less UPDATE"
+        assert ops == []
+
+    def test_move_without_destination_returns_error(self):
+        """A MOVE without '->' syntax should not silently produce a broken operation."""
+        # The move regex requires '->' so this will be treated as an unrecognised
+        # line and the op is never created.  Confirm nothing crashes and ops is empty.
+        patch = """\
+*** Begin Patch
+*** Move File: src/foo.py
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        # Either parse sees zero ops (fine) or returns an error (also fine).
+        # What is NOT acceptable is ops=[MOVE op with empty new_path] + err=None.
+        if ops:
+            assert err is not None, (
+                "MOVE with missing destination must either produce empty ops or an error"
+            )
+
+    def test_valid_patch_returns_no_error(self):
+        """A well-formed patch must still return err=None."""
+        patch = """\
+*** Begin Patch
+*** Update File: f.py
+ ctx
+-old
++new
+*** End Patch"""
+        ops, err = parse_v4a_patch(patch)
+        assert err is None
+        assert len(ops) == 1

tools/file_operations.py

@@ -252,23 +252,43 @@ class FileOperations(ABC):
     def read_file(self, path: str, offset: int = 1, limit: int = 500) -> ReadResult:
         """Read a file with pagination support."""
         ...
-    
+
+    @abstractmethod
+    def read_file_raw(self, path: str) -> ReadResult:
+        """Read the complete file content as a plain string.
+
+        No pagination, no line-number prefixes, no per-line truncation.
+        Returns ReadResult with .content = full file text, .error set on
+        failure. Always reads to EOF regardless of file size.
+        """
+        ...
+
     @abstractmethod
     def write_file(self, path: str, content: str) -> WriteResult:
         """Write content to a file, creating directories as needed."""
         ...
-    
+
     @abstractmethod
-    def patch_replace(self, path: str, old_string: str, new_string: str, 
+    def patch_replace(self, path: str, old_string: str, new_string: str,
                       replace_all: bool = False) -> PatchResult:
         """Replace text in a file using fuzzy matching."""
         ...
-    
+
     @abstractmethod
     def patch_v4a(self, patch_content: str) -> PatchResult:
         """Apply a V4A format patch."""
         ...
-    
+
+    @abstractmethod
+    def delete_file(self, path: str) -> WriteResult:
+        """Delete a file. Returns WriteResult with .error set on failure."""
+        ...
+
+    @abstractmethod
+    def move_file(self, src: str, dst: str) -> WriteResult:
+        """Move/rename a file from src to dst. Returns WriteResult with .error set on failure."""
+        ...
+
     @abstractmethod
     def search(self, pattern: str, path: str = ".", target: str = "content",
                file_glob: Optional[str] = None, limit: int = 50, offset: int = 0,
@@ -561,10 +581,62 @@ class ShellFileOperations(FileOperations):
             similar_files=similar[:5]  # Limit to 5 suggestions
         )
     
+    def read_file_raw(self, path: str) -> ReadResult:
+        """Read the complete file content as a plain string.
+
+        No pagination, no line-number prefixes, no per-line truncation.
+        Uses cat so the full file is returned regardless of size.
+        """
+        path = self._expand_path(path)
+        stat_cmd = f"wc -c < {self._escape_shell_arg(path)} 2>/dev/null"
+        stat_result = self._exec(stat_cmd)
+        if stat_result.exit_code != 0:
+            return self._suggest_similar_files(path)
+        try:
+            file_size = int(stat_result.stdout.strip())
+        except ValueError:
+            file_size = 0
+        if self._is_image(path):
+            return ReadResult(is_image=True, is_binary=True, file_size=file_size)
+        sample_result = self._exec(f"head -c 1000 {self._escape_shell_arg(path)} 2>/dev/null")
+        if self._is_likely_binary(path, sample_result.stdout):
+            return ReadResult(
+                is_binary=True, file_size=file_size,
+                error="Binary file — cannot display as text."
+            )
+        cat_result = self._exec(f"cat {self._escape_shell_arg(path)}")
+        if cat_result.exit_code != 0:
+            return ReadResult(error=f"Failed to read file: {cat_result.stdout}")
+        return ReadResult(content=cat_result.stdout, file_size=file_size)
+
+    def delete_file(self, path: str) -> WriteResult:
+        """Delete a file via rm."""
+        path = self._expand_path(path)
+        if _is_write_denied(path):
+            return WriteResult(error=f"Delete denied: {path} is a protected path")
+        result = self._exec(f"rm -f {self._escape_shell_arg(path)}")
+        if result.exit_code != 0:
+            return WriteResult(error=f"Failed to delete {path}: {result.stdout}")
+        return WriteResult()
+
+    def move_file(self, src: str, dst: str) -> WriteResult:
+        """Move a file via mv."""
+        src = self._expand_path(src)
+        dst = self._expand_path(dst)
+        for p in (src, dst):
+            if _is_write_denied(p):
+                return WriteResult(error=f"Move denied: {p} is a protected path")
+        result = self._exec(
+            f"mv {self._escape_shell_arg(src)} {self._escape_shell_arg(dst)}"
+        )
+        if result.exit_code != 0:
+            return WriteResult(error=f"Failed to move {src} -> {dst}: {result.stdout}")
+        return WriteResult()
+
     # =========================================================================
     # WRITE Implementation
     # =========================================================================
-    
+
     def write_file(self, path: str, content: str) -> WriteResult:
         """
         Write content to a file, creating parent directories as needed.
@@ -656,7 +728,7 @@ class ShellFileOperations(FileOperations):
         # Import and use fuzzy matching
         from tools.fuzzy_match import fuzzy_find_and_replace
         
-        new_content, match_count, error = fuzzy_find_and_replace(
+        new_content, match_count, _strategy, error = fuzzy_find_and_replace(
             content, old_string, new_string, replace_all
         )
         

tools/fuzzy_match.py

@@ -21,7 +21,7 @@ Multi-occurrence matching is handled via the replace_all flag.
 Usage:
     from tools.fuzzy_match import fuzzy_find_and_replace
     
-    new_content, match_count, error = fuzzy_find_and_replace(
+    new_content, match_count, strategy, error = fuzzy_find_and_replace(
         content="def foo():\\n    pass",
         old_string="def foo():",
         new_string="def bar():",
@@ -48,27 +48,27 @@ def _unicode_normalize(text: str) -> str:
 
 
 def fuzzy_find_and_replace(content: str, old_string: str, new_string: str,
-                            replace_all: bool = False) -> Tuple[str, int, Optional[str]]:
+                            replace_all: bool = False) -> Tuple[str, int, Optional[str], Optional[str]]:
     """
     Find and replace text using a chain of increasingly fuzzy matching strategies.
-    
+
     Args:
         content: The file content to search in
         old_string: The text to find
         new_string: The replacement text
         replace_all: If True, replace all occurrences; if False, require uniqueness
-    
+
     Returns:
-        Tuple of (new_content, match_count, error_message)
+        Tuple of (new_content, match_count, strategy_name, error_message)
-        - If successful: (modified_content, number_of_replacements, None)
+        - If successful: (modified_content, number_of_replacements, strategy_used, None)
-        - If failed: (original_content, 0, error_description)
+        - If failed: (original_content, 0, None, error_description)
     """
     if not old_string:
-        return content, 0, "old_string cannot be empty"
+        return content, 0, None, "old_string cannot be empty"
-    
+
     if old_string == new_string:
-        return content, 0, "old_string and new_string are identical"
+        return content, 0, None, "old_string and new_string are identical"
-    
+
     # Try each matching strategy in order
     strategies: List[Tuple[str, Callable]] = [
         ("exact", _strategy_exact),
@@ -77,27 +77,28 @@ def fuzzy_find_and_replace(content: str, old_string: str, new_string: str,
         ("indentation_flexible", _strategy_indentation_flexible),
         ("escape_normalized", _strategy_escape_normalized),
         ("trimmed_boundary", _strategy_trimmed_boundary),
+        ("unicode_normalized", _strategy_unicode_normalized),
         ("block_anchor", _strategy_block_anchor),
         ("context_aware", _strategy_context_aware),
     ]
-    
+
-    for _strategy_name, strategy_fn in strategies:
+    for strategy_name, strategy_fn in strategies:
         matches = strategy_fn(content, old_string)
-        
+
         if matches:
             # Found matches with this strategy
             if len(matches) > 1 and not replace_all:
-                return content, 0, (
+                return content, 0, None, (
                     f"Found {len(matches)} matches for old_string. "
                     f"Provide more context to make it unique, or use replace_all=True."
                 )
-            
+
             # Perform replacement
             new_content = _apply_replacements(content, matches, new_string)
-            return new_content, len(matches), None
+            return new_content, len(matches), strategy_name, None
-    
+
     # No strategy found a match
-    return content, 0, "Could not find a match for old_string in the file"
+    return content, 0, None, "Could not find a match for old_string in the file"
 
 
 def _apply_replacements(content: str, matches: List[Tuple[int, int]], new_string: str) -> str:
@@ -258,9 +259,90 @@ def _strategy_trimmed_boundary(content: str, pattern: str) -> List[Tuple[int, in
     return matches
 
 
+def _build_orig_to_norm_map(original: str) -> List[int]:
+    """Build a list mapping each original character index to its normalized index.
+
+    Because UNICODE_MAP replacements may expand characters (e.g. em-dash → '--',
+    ellipsis → '...'), the normalised string can be longer than the original.
+    This map lets us convert positions in the normalised string back to the
+    corresponding positions in the original string.
+
+    Returns a list of length ``len(original) + 1``; entry ``i`` is the
+    normalised index that character ``i`` maps to.
+    """
+    result: List[int] = []
+    norm_pos = 0
+    for char in original:
+        result.append(norm_pos)
+        repl = UNICODE_MAP.get(char)
+        norm_pos += len(repl) if repl is not None else 1
+    result.append(norm_pos)  # sentinel: one past the last character
+    return result
+
+
+def _map_positions_norm_to_orig(
+    orig_to_norm: List[int],
+    norm_matches: List[Tuple[int, int]],
+) -> List[Tuple[int, int]]:
+    """Convert (start, end) positions in the normalised string to original positions."""
+    # Invert the map: norm_pos -> first original position with that norm_pos
+    norm_to_orig_start: dict[int, int] = {}
+    for orig_pos, norm_pos in enumerate(orig_to_norm[:-1]):
+        if norm_pos not in norm_to_orig_start:
+            norm_to_orig_start[norm_pos] = orig_pos
+
+    results: List[Tuple[int, int]] = []
+    orig_len = len(orig_to_norm) - 1  # number of original characters
+
+    for norm_start, norm_end in norm_matches:
+        if norm_start not in norm_to_orig_start:
+            continue
+        orig_start = norm_to_orig_start[norm_start]
+
+        # Walk forward until orig_to_norm[orig_end] >= norm_end
+        orig_end = orig_start
+        while orig_end < orig_len and orig_to_norm[orig_end] < norm_end:
+            orig_end += 1
+
+        results.append((orig_start, orig_end))
+
+    return results
+
+
+def _strategy_unicode_normalized(content: str, pattern: str) -> List[Tuple[int, int]]:
+    """Strategy 7: Unicode normalisation.
+
+    Normalises smart quotes, em/en-dashes, ellipsis, and non-breaking spaces
+    to their ASCII equivalents in both *content* and *pattern*, then runs
+    exact and line_trimmed matching on the normalised copies.
+
+    Positions are mapped back to the *original* string via
+    ``_build_orig_to_norm_map`` — necessary because some UNICODE_MAP
+    replacements expand a single character into multiple ASCII characters,
+    making a naïve position copy incorrect.
+    """
+    # Normalize both sides. Either the content or the pattern (or both) may
+    # carry unicode variants — e.g. content has an em-dash that should match
+    # the LLM's ASCII '--', or vice-versa.  Skip only when neither changes.
+    norm_pattern = _unicode_normalize(pattern)
+    norm_content = _unicode_normalize(content)
+    if norm_content == content and norm_pattern == pattern:
+        return []
+
+    norm_matches = _strategy_exact(norm_content, norm_pattern)
+    if not norm_matches:
+        norm_matches = _strategy_line_trimmed(norm_content, norm_pattern)
+
+    if not norm_matches:
+        return []
+
+    orig_to_norm = _build_orig_to_norm_map(content)
+    return _map_positions_norm_to_orig(orig_to_norm, norm_matches)
+
+
 def _strategy_block_anchor(content: str, pattern: str) -> List[Tuple[int, int]]:
     """
-    Strategy 7: Match by anchoring on first and last lines.
+    Strategy 8: Match by anchoring on first and last lines.
     Adjusted with permissive thresholds and unicode normalization.
     """
     # Normalize both strings for comparison while keeping original content for offset calculation
@@ -290,8 +372,10 @@ def _strategy_block_anchor(content: str, pattern: str) -> List[Tuple[int, int]]:
     matches = []
     candidate_count = len(potential_matches)
     
-    # Thresholding logic: 0.10 for unique matches (max flexibility), 0.30 for multiple candidates
+    # Thresholding logic: 0.50 for unique matches, 0.70 for multiple candidates.
-    threshold = 0.10 if candidate_count == 1 else 0.30
+    # Previous values (0.10 / 0.30) were dangerously loose — a 10% middle-section
+    # similarity could match completely unrelated blocks.
+    threshold = 0.50 if candidate_count == 1 else 0.70
 
     for i in potential_matches:
         if pattern_line_count <= 2:
@@ -314,7 +398,7 @@ def _strategy_block_anchor(content: str, pattern: str) -> List[Tuple[int, int]]:
 
 def _strategy_context_aware(content: str, pattern: str) -> List[Tuple[int, int]]:
     """
-    Strategy 8: Line-by-line similarity with 50% threshold.
+    Strategy 9: Line-by-line similarity with 50% threshold.
     
     Finds blocks where at least 50% of lines have high similarity.
     """

tools/patch_parser.py

@@ -28,6 +28,7 @@ Usage:
         result = apply_v4a_operations(operations, file_ops)
 """
 
+import difflib
 import re
 from dataclasses import dataclass, field
 from typing import List, Optional, Tuple, Any
@@ -202,31 +203,162 @@ def parse_v4a_patch(patch_content: str) -> Tuple[List[PatchOperation], Optional[
         if current_hunk and current_hunk.lines:
             current_op.hunks.append(current_hunk)
         operations.append(current_op)
-    
+
+    # Validate the parsed result
+    if not operations:
+        # Empty patch is not an error — callers get [] and can decide
+        return operations, None
+
+    parse_errors: List[str] = []
+    for op in operations:
+        if not op.file_path:
+            parse_errors.append("Operation with empty file path")
+        if op.operation == OperationType.UPDATE and not op.hunks:
+            parse_errors.append(f"UPDATE {op.file_path!r}: no hunks found")
+        if op.operation == OperationType.MOVE and not op.new_path:
+            parse_errors.append(f"MOVE {op.file_path!r}: missing destination path (expected 'src -> dst')")
+
+    if parse_errors:
+        return [], "Parse error: " + "; ".join(parse_errors)
+
     return operations, None
 
 
-def apply_v4a_operations(operations: List[PatchOperation], 
+def _count_occurrences(text: str, pattern: str) -> int:
-                          file_ops: Any) -> 'PatchResult':
+    """Count non-overlapping occurrences of *pattern* in *text*."""
+    count = 0
+    start = 0
+    while True:
+        pos = text.find(pattern, start)
+        if pos == -1:
+            break
+        count += 1
+        start = pos + 1
+    return count
+
+
+def _validate_operations(
+    operations: List[PatchOperation],
+    file_ops: Any,
+) -> List[str]:
+    """Validate all operations without writing any files.
+
+    Returns a list of error strings; an empty list means all operations
+    are valid and the apply phase can proceed safely.
+
+    For UPDATE operations, hunks are simulated in order so that later
+    hunks validate against post-earlier-hunk content (matching apply order).
     """
-    Apply V4A patch operations using a file operations interface.
+    # Deferred import: breaks the patch_parser ↔ fuzzy_match circular dependency
-    
+    from tools.fuzzy_match import fuzzy_find_and_replace
+
+    errors: List[str] = []
+
+    for op in operations:
+        if op.operation == OperationType.UPDATE:
+            read_result = file_ops.read_file_raw(op.file_path)
+            if read_result.error:
+                errors.append(f"{op.file_path}: {read_result.error}")
+                continue
+
+            simulated = read_result.content
+            for hunk in op.hunks:
+                search_lines = [l.content for l in hunk.lines if l.prefix in (' ', '-')]
+                if not search_lines:
+                    # Addition-only hunk: validate context hint uniqueness
+                    if hunk.context_hint:
+                        occurrences = _count_occurrences(simulated, hunk.context_hint)
+                        if occurrences == 0:
+                            errors.append(
+                                f"{op.file_path}: addition-only hunk context hint "
+                                f"'{hunk.context_hint}' not found"
+                            )
+                        elif occurrences > 1:
+                            errors.append(
+                                f"{op.file_path}: addition-only hunk context hint "
+                                f"'{hunk.context_hint}' is ambiguous "
+                                f"({occurrences} occurrences)"
+                            )
+                    continue
+
+                search_pattern = '\n'.join(search_lines)
+                replace_lines = [l.content for l in hunk.lines if l.prefix in (' ', '+')]
+                replacement = '\n'.join(replace_lines)
+
+                new_simulated, count, _strategy, match_error = fuzzy_find_and_replace(
+                    simulated, search_pattern, replacement, replace_all=False
+                )
+                if count == 0:
+                    label = f"'{hunk.context_hint}'" if hunk.context_hint else "(no hint)"
+                    errors.append(
+                        f"{op.file_path}: hunk {label} not found"
+                        + (f" — {match_error}" if match_error else "")
+                    )
+                else:
+                    # Advance simulation so subsequent hunks validate correctly.
+                    # Reuse the result from the call above — no second fuzzy run.
+                    simulated = new_simulated
+
+        elif op.operation == OperationType.DELETE:
+            read_result = file_ops.read_file_raw(op.file_path)
+            if read_result.error:
+                errors.append(f"{op.file_path}: file not found for deletion")
+
+        elif op.operation == OperationType.MOVE:
+            if not op.new_path:
+                errors.append(f"{op.file_path}: MOVE operation missing destination path")
+                continue
+            src_result = file_ops.read_file_raw(op.file_path)
+            if src_result.error:
+                errors.append(f"{op.file_path}: source file not found for move")
+            dst_result = file_ops.read_file_raw(op.new_path)
+            if not dst_result.error:
+                errors.append(
+                    f"{op.new_path}: destination already exists — move would overwrite"
+                )
+
+        # ADD: parent directory creation handled by write_file; no pre-check needed.
+
+    return errors
+
+
+def apply_v4a_operations(operations: List[PatchOperation],
+                          file_ops: Any) -> 'PatchResult':
+    """Apply V4A patch operations using a file operations interface.
+
+    Uses a two-phase validate-then-apply approach:
+    - Phase 1: validate all operations against current file contents without
+      writing anything. If any validation error is found, return immediately
+      with no filesystem changes.
+    - Phase 2: apply all operations. A failure here (e.g. a race between
+      validation and apply) is reported with a note to run ``git diff``.
+
     Args:
         operations: List of PatchOperation from parse_v4a_patch
-        file_ops: Object with read_file, write_file methods
+        file_ops: Object with read_file_raw, write_file methods
-    
+
     Returns:
         PatchResult with results of all operations
     """
     # Import here to avoid circular imports
     from tools.file_operations import PatchResult
-    
+
+    # ---- Phase 1: validate ----
+    validation_errors = _validate_operations(operations, file_ops)
+    if validation_errors:
+        return PatchResult(
+            success=False,
+            error="Patch validation failed (no files were modified):\n"
+                  + "\n".join(f"  • {e}" for e in validation_errors),
+        )
+
+    # ---- Phase 2: apply ----
     files_modified = []
     files_created = []
     files_deleted = []
     all_diffs = []
     errors = []
-    
+
     for op in operations:
         try:
             if op.operation == OperationType.ADD:
@@ -236,7 +368,7 @@ def apply_v4a_operations(operations: List[PatchOperation],
                     all_diffs.append(result[1])
                 else:
                     errors.append(f"Failed to add {op.file_path}: {result[1]}")
-                    
+
             elif op.operation == OperationType.DELETE:
                 result = _apply_delete(op, file_ops)
                 if result[0]:
@@ -244,7 +376,7 @@ def apply_v4a_operations(operations: List[PatchOperation],
                     all_diffs.append(result[1])
                 else:
                     errors.append(f"Failed to delete {op.file_path}: {result[1]}")
-                    
+
             elif op.operation == OperationType.MOVE:
                 result = _apply_move(op, file_ops)
                 if result[0]:
@@ -252,7 +384,7 @@ def apply_v4a_operations(operations: List[PatchOperation],
                     all_diffs.append(result[1])
                 else:
                     errors.append(f"Failed to move {op.file_path}: {result[1]}")
-                    
+
             elif op.operation == OperationType.UPDATE:
                 result = _apply_update(op, file_ops)
                 if result[0]:
@@ -260,19 +392,19 @@ def apply_v4a_operations(operations: List[PatchOperation],
                     all_diffs.append(result[1])
                 else:
                     errors.append(f"Failed to update {op.file_path}: {result[1]}")
-                    
+
         except Exception as e:
             errors.append(f"Error processing {op.file_path}: {str(e)}")
-    
+
     # Run lint on all modified/created files
     lint_results = {}
     for f in files_modified + files_created:
         if hasattr(file_ops, '_check_lint'):
             lint_result = file_ops._check_lint(f)
             lint_results[f] = lint_result.to_dict()
-    
+
     combined_diff = '\n'.join(all_diffs)
-    
+
     if errors:
         return PatchResult(
             success=False,
@@ -281,16 +413,17 @@ def apply_v4a_operations(operations: List[PatchOperation],
             files_created=files_created,
             files_deleted=files_deleted,
             lint=lint_results if lint_results else None,
-            error='; '.join(errors)
+            error="Apply phase failed (state may be inconsistent — run `git diff` to assess):\n"
+                  + "\n".join(f"  • {e}" for e in errors),
         )
-    
+
     return PatchResult(
         success=True,
         diff=combined_diff,
         files_modified=files_modified,
         files_created=files_created,
         files_deleted=files_deleted,
-        lint=lint_results if lint_results else None
+        lint=lint_results if lint_results else None,
     )
 
 
@@ -317,68 +450,56 @@ def _apply_add(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
 
 def _apply_delete(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
     """Apply a delete file operation."""
-    # Read file first for diff
+    # Read before deleting so we can produce a real unified diff.
-    read_result = file_ops.read_file(op.file_path)
+    # Validation already confirmed existence; this guards against races.
-    
+    read_result = file_ops.read_file_raw(op.file_path)
-    if read_result.error and "not found" in read_result.error.lower():
+    if read_result.error:
-        # File doesn't exist, nothing to delete
+        return False, f"Cannot delete {op.file_path}: file not found"
-        return True, f"# {op.file_path} already deleted or doesn't exist"
+
-    
+    result = file_ops.delete_file(op.file_path)
-    # Delete directly via shell command using the underlying environment
+    if result.error:
-    rm_result = file_ops._exec(f"rm -f {file_ops._escape_shell_arg(op.file_path)}")
+        return False, result.error
-    
+
-    if rm_result.exit_code != 0:
+    removed_lines = read_result.content.splitlines(keepends=True)
-        return False, rm_result.stdout
+    diff = ''.join(difflib.unified_diff(
-    
+        removed_lines, [],
-    diff = f"--- a/{op.file_path}\n+++ /dev/null\n# File deleted"
+        fromfile=f"a/{op.file_path}",
-    return True, diff
+        tofile="/dev/null",
+    ))
+    return True, diff or f"# Deleted: {op.file_path}"
 
 
 def _apply_move(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
     """Apply a move file operation."""
-    # Use shell mv command
+    result = file_ops.move_file(op.file_path, op.new_path)
-    mv_result = file_ops._exec(
+    if result.error:
-        f"mv {file_ops._escape_shell_arg(op.file_path)} {file_ops._escape_shell_arg(op.new_path)}"
+        return False, result.error
-    )
+
-    
-    if mv_result.exit_code != 0:
-        return False, mv_result.stdout
-    
     diff = f"# Moved: {op.file_path} -> {op.new_path}"
     return True, diff
 
 
 def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
     """Apply an update file operation."""
-    # Read current content
+    # Deferred import: breaks the patch_parser ↔ fuzzy_match circular dependency
-    read_result = file_ops.read_file(op.file_path, limit=10000)
+    from tools.fuzzy_match import fuzzy_find_and_replace
-    
+
+    # Read current content — raw so no line-number prefixes or per-line truncation
+    read_result = file_ops.read_file_raw(op.file_path)
+
     if read_result.error:
         return False, f"Cannot read file: {read_result.error}"
-    
+
-    # Parse content (remove line numbers)
+    current_content = read_result.content
-    current_lines = []
+
-    for line in read_result.content.split('\n'):
-        if re.match(r'^\s*\d+\|', line):
-            # Line format: "    123|content"
-            parts = line.split('|', 1)
-            if len(parts) == 2:
-                current_lines.append(parts[1])
-            else:
-                current_lines.append(line)
-        else:
-            current_lines.append(line)
-    
-    current_content = '\n'.join(current_lines)
-    
     # Apply each hunk
     new_content = current_content
-    
+
     for hunk in op.hunks:
         # Build search pattern from context and removed lines
         search_lines = []
         replace_lines = []
-        
+
         for line in hunk.lines:
             if line.prefix == ' ':
                 search_lines.append(line.content)
@@ -387,17 +508,15 @@ def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
                 search_lines.append(line.content)
             elif line.prefix == '+':
                 replace_lines.append(line.content)
-        
+
         if search_lines:
             search_pattern = '\n'.join(search_lines)
             replacement = '\n'.join(replace_lines)
-            
+
-            # Use fuzzy matching
+            new_content, count, _strategy, error = fuzzy_find_and_replace(
-            from tools.fuzzy_match import fuzzy_find_and_replace
-            new_content, count, error = fuzzy_find_and_replace(
                 new_content, search_pattern, replacement, replace_all=False
             )
-            
+
             if error and count == 0:
                 # Try with context hint if available
                 if hunk.context_hint:
@@ -408,8 +527,8 @@ def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
                         window_start = max(0, hint_pos - 500)
                         window_end = min(len(new_content), hint_pos + 2000)
                         window = new_content[window_start:window_end]
-                        
+
-                        window_new, count, error = fuzzy_find_and_replace(
+                        window_new, count, _strategy, error = fuzzy_find_and_replace(
                             window, search_pattern, replacement, replace_all=False
                         )
                         
@@ -424,16 +543,23 @@ def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
             # Insert at the location indicated by the context hint, or at end of file.
             insert_text = '\n'.join(replace_lines)
             if hunk.context_hint:
-                hint_pos = new_content.find(hunk.context_hint)
+                occurrences = _count_occurrences(new_content, hunk.context_hint)
-                if hint_pos != -1:
+                if occurrences == 0:
+                    # Hint not found — append at end as a safe fallback
+                    new_content = new_content.rstrip('\n') + '\n' + insert_text + '\n'
+                elif occurrences > 1:
+                    return False, (
+                        f"Addition-only hunk: context hint '{hunk.context_hint}' is ambiguous "
+                        f"({occurrences} occurrences) — provide a more unique hint"
+                    )
+                else:
+                    hint_pos = new_content.find(hunk.context_hint)
                     # Insert after the line containing the context hint
                     eol = new_content.find('\n', hint_pos)
                     if eol != -1:
                         new_content = new_content[:eol + 1] + insert_text + '\n' + new_content[eol + 1:]
                     else:
                         new_content = new_content + '\n' + insert_text
-                else:
-                    new_content = new_content.rstrip('\n') + '\n' + insert_text + '\n'
             else:
                 new_content = new_content.rstrip('\n') + '\n' + insert_text + '\n'
     
@@ -443,7 +569,6 @@ def _apply_update(op: PatchOperation, file_ops: Any) -> Tuple[bool, str]:
         return False, write_result.error
     
     # Generate diff
-    import difflib
     diff_lines = difflib.unified_diff(
         current_content.splitlines(keepends=True),
         new_content.splitlines(keepends=True),

tools/skill_manager_tool.py

@@ -426,7 +426,7 @@ def _patch_skill(
     # from exact-match failures on minor formatting mismatches.
     from tools.fuzzy_match import fuzzy_find_and_replace
 
-    new_content, match_count, match_error = fuzzy_find_and_replace(
+    new_content, match_count, _strategy, match_error = fuzzy_find_and_replace(
         content, old_string, new_string, replace_all
     )
     if match_error: