diff --git a/src/cycod/FunctionCalling/FunctionFactory.cs b/src/cycod/FunctionCalling/FunctionFactory.cs
index 18bdeaa6..877c6f03 100644
--- a/src/cycod/FunctionCalling/FunctionFactory.cs
+++ b/src/cycod/FunctionCalling/FunctionFactory.cs
@@ -318,7 +318,8 @@ private static object CreateGenericCollectionFromJsonArray(string parameterValue
             var collection = Array.CreateInstance(elementType, array.Length);
             for (int i = 0; i < array.Length; i++)
             {
-                var parsed = ParseParameterValue(array[i].GetRawText(), elementType);
+                var elementValue = array[i].ValueKind == JsonValueKind.String ? array[i].GetString()! : array[i].GetRawText();
+                var parsed = ParseParameterValue(elementValue, elementType);
                 if (parsed != null) collection.SetValue(parsed, i);
             }
             return collection;
@@ -329,7 +330,8 @@ private static object CreateGenericCollectionFromJsonArray(string parameterValue
             var list = collection as IList;
             foreach (var item in array)
             {
-                var parsed = ParseParameterValue(item.GetRawText(), elementType);
+                var elementValue = item.ValueKind == JsonValueKind.String ? item.GetString()! : item.GetRawText();
+                var parsed = ParseParameterValue(elementValue, elementType);
                 if (parsed != null) list!.Add(parsed);
             }
             return collection!;
@@ -349,7 +351,8 @@ private static object CreateTuppleTypeFromJsonArray(string parameterValue, Type
 
         foreach (var item in array)
         {
-            var parsed = ParseParameterValue(item.GetRawText(), elementType);
+            var elementValue = item.ValueKind == JsonValueKind.String ? item.GetString()! : item.GetRawText();
+            var parsed = ParseParameterValue(elementValue, elementType);
             if (parsed != null) list!.Add(parsed);
         }
 
diff --git a/src/cycod/FunctionCallingTools/StrReplaceEditorHelperFunctions.cs b/src/cycod/FunctionCallingTools/StrReplaceEditorHelperFunctions.cs
index be8bab2e..a32b5602 100644
--- a/src/cycod/FunctionCallingTools/StrReplaceEditorHelperFunctions.cs
+++ b/src/cycod/FunctionCallingTools/StrReplaceEditorHelperFunctions.cs
@@ -305,6 +305,43 @@ public string CreateFile(
         return $"Created file {path} with {fileText.Length} characters.";
     }
 
+    [ReadOnly(false)]
+    [Description("Replaces the entire content of an existing file. Requires knowing the current line count as verification that you've read the file.")]
+    public string ReplaceFileContent(
+        [Description("Absolute or relative path to file.")] string path,
+        [Description("New content to replace the entire file.")] string newContent,
+        [Description("Current line count of the file (for verification).")] int oldContentLineCount)
+    {
+        if (!File.Exists(path))
+        {
+            return $"File {path} does not exist. Use CreateFile to create a new file.";
+        }
+
+        // Read current content and count lines
+        var currentContent = File.ReadAllText(path);
+        var currentLines = currentContent.Split(new[] { "\r\n", "\n" }, StringSplitOptions.None);
+        var actualLineCount = currentLines.Length;
+
+        // Verify line count matches
+        if (actualLineCount != oldContentLineCount)
+        {
+            return $"Line count mismatch: you specified {oldContentLineCount} but file has {actualLineCount} lines. Please read the file with ViewFile and verify the line count.";
+        }
+
+        // Save current content for undo
+        if (!EditHistory.ContainsKey(path))
+        {
+            EditHistory[path] = currentContent;
+        }
+
+        // Replace entire content
+        File.WriteAllText(path, newContent);
+        var newLines = newContent.Split(new[] { "\r\n", "\n" }, StringSplitOptions.None);
+        
+        return $"Replaced content in {path}: {actualLineCount} lines → {newLines.Length} lines ({newContent.Length} characters).";
+    }
+
+
     // [ReadOnly(false)]
     // [Description("Replaces the lines in the file at `path` from `startLine` to `endLine` with the new string `newStr`. If `endLine` is -1, all remaining lines are replaced.")]
     // public string LinesReplace(
@@ -378,6 +415,75 @@ public string ReplaceOneInFile(
         return $"File {path} updated: replaced 1 occurrence of specified text.";
     }
 
+    [ReadOnly(false)]
+    [Description("Replaces multiple text patterns in a single file atomically. All replacements must be unique occurrences.")]
+    public string ReplaceMultipleInFile(
+        [Description("Absolute or relative path to file.")] string path,
+        [Description("Array of old strings to be replaced. Each must match exactly one occurrence.")] string[] oldStrings,
+        [Description("Array of new strings to replace with. Must be same length as oldStrings.")] string[] newStrings)
+    {
+        if (!File.Exists(path))
+        {
+            return $"File {path} does not exist.";
+        }
+
+        if (oldStrings.Length != newStrings.Length)
+        {
+            return $"Error: oldStrings array length ({oldStrings.Length}) must match newStrings array length ({newStrings.Length}).";
+        }
+
+        if (oldStrings.Length == 0)
+        {
+            return "Error: No replacements specified.";
+        }
+
+        var originalText = FileHelpers.ReadAllText(path);
+        var currentText = originalText;
+
+        // Validate all patterns exist and are unique before making any changes
+        for (int i = 0; i < oldStrings.Length; i++)
+        {
+            var oldStr = oldStrings[i];
+            var newStr = newStrings[i];
+            
+            var testReplacement = StringHelpers.ReplaceOnce(currentText, oldStr, newStr, out var countFound);
+            if (countFound != 1)
+            {
+                var message = countFound == 0
+                    ? $"Replacement {i + 1}: No occurrences of specified text found."
+                    : $"Replacement {i + 1}: Multiple matches found for specified text; must be unique.";
+                return $"{message}\nNo changes made to {path}.";
+            }
+        }
+
+        // All validations passed, now perform the replacements
+        for (int i = 0; i < oldStrings.Length; i++)
+        {
+            var oldStr = oldStrings[i];
+            var newStr = newStrings[i];
+            
+            var replacedText = StringHelpers.ReplaceOnce(currentText, oldStr, newStr, out var countFound);
+            if (replacedText != null && countFound == 1)
+            {
+                currentText = replacedText;
+            }
+            else
+            {
+                // This shouldn't happen since we validated, but handle gracefully
+                return $"Unexpected error during replacement {i + 1}. File may be in inconsistent state.";
+            }
+        }
+
+        // Save original content for undo before writing
+        if (!EditHistory.ContainsKey(path))
+        {
+            EditHistory[path] = originalText;
+        }
+
+        File.WriteAllText(path, currentText);
+        
+        return $"File {path} updated: replaced {oldStrings.Length} occurrences.";
+    }
     [ReadOnly(false)]
     [Description("Inserts the specified string `newStr` into the file at `path` after the specified line number (`insertLine`). Use 0 to insert at the beginning of the file.")]
     public string Insert(
diff --git a/tests/cycod-yaml/file-replacement-functions.yaml b/tests/cycod-yaml/file-replacement-functions.yaml
new file mode 100644
index 00000000..463b21e9
--- /dev/null
+++ b/tests/cycod-yaml/file-replacement-functions.yaml
@@ -0,0 +1,150 @@
+tests:
+  # ReplaceFileContent tests
+  - name: ReplaceFileContent with correct line count succeeds
+    steps:
+    - name: Run test
+      bash: |
+        printf 'line 1\nline 2\nline 3' > test-replace-content.txt
+        cycod --input "use ReplaceFileContent to replace test-replace-content.txt with 'new content', it has 3 lines" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceFileContent
+        path.*test-replace-content\.txt
+        newContent.*new content
+        oldContentLineCount.*3
+        Replaced content.*3 lines.*1 lines
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-replace-content.txt
+    optional: needsAI
+
+  - name: ReplaceFileContent with wrong line count fails
+    steps:
+    - name: Run test
+      bash: |
+        printf 'line 1\nline 2\nline 3' > test-replace-fail.txt
+        cycod --input "use ReplaceFileContent to replace test-replace-fail.txt with 'new', say it has 5 lines (which is wrong)" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceFileContent
+        oldContentLineCount.*5
+        Line count mismatch.*you specified 5 but file has 3 lines
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-replace-fail.txt
+    optional: needsAI
+
+  - name: ReplaceFileContent on non-existent file fails
+    bash: |
+      cycod --input "use ReplaceFileContent to replace nonexistent-file.txt with 'content', say it has 1 line" --auto-approve '*'
+    expect-regex: |
+      assistant-function: ReplaceFileContent
+      File.*does not exist.*Use CreateFile
+    timeout: 30000
+    optional: needsAI
+
+  - name: ReplaceFileContent can be undone
+    steps:
+    - name: Run test
+      bash: |
+        echo "original content" > test-undo-replace.txt
+        cycod --input "First use ReplaceFileContent to replace test-undo-replace.txt with 'new content', it has 1 line. Then use UndoEdit to revert it." --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceFileContent
+        Replaced content
+        assistant-function: UndoEdit
+        Reverted last edit
+      timeout: 45000
+    - name: Cleanup
+      bash: rm -f test-undo-replace.txt
+    optional: needsAI
+
+  # ReplaceMultipleInFile tests
+  - name: ReplaceMultipleInFile replaces multiple patterns atomically
+    steps:
+    - name: Run test
+      bash: |
+        echo "foo bar baz" > test-multi-replace.txt
+        cycod --input "use ReplaceMultipleInFile on test-multi-replace.txt to replace 'foo' with 'FOO' and 'bar' with 'BAR'" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        path.*test-multi-replace\.txt
+        oldStrings.*foo.*bar
+        newStrings.*FOO.*BAR
+        replaced 2 occurrences
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-multi-replace.txt
+    optional: needsAI
+
+  - name: ReplaceMultipleInFile fails if pattern not found
+    steps:
+    - name: Run test
+      bash: |
+        echo "foo bar" > test-multi-fail.txt
+        cycod --input "use ReplaceMultipleInFile on test-multi-fail.txt to replace 'foo' with 'FOO' and 'baz' with 'BAZ' (baz doesn't exist)" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        No occurrences.*found|not found
+        No changes made
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-multi-fail.txt
+    optional: needsAI
+
+  - name: ReplaceMultipleInFile fails if array lengths don't match
+    steps:
+    - name: Run test
+      bash: |
+        echo "foo bar baz" > test-array-length.txt
+        cycod --input "use ReplaceMultipleInFile on test-array-length.txt with oldStrings=['foo','bar'] but newStrings=['FOO'] (mismatched lengths)" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        array length.*must match
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-array-length.txt
+    optional: needsAI
+
+  - name: ReplaceMultipleInFile handles string arrays correctly
+    steps:
+    - name: Run test
+      bash: |
+        echo "alpha beta gamma delta" > test-string-array.txt
+        cycod --input "use ReplaceMultipleInFile on test-string-array.txt to replace ['alpha', 'beta', 'gamma'] with ['ALPHA', 'BETA', 'GAMMA']" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        replaced 3 occurrences
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-string-array.txt
+    optional: needsAI
+
+  - name: ReplaceMultipleInFile can be undone
+    steps:
+    - name: Run test
+      bash: |
+        echo "foo bar baz" > test-multi-undo.txt
+        cycod --input "First use ReplaceMultipleInFile on test-multi-undo.txt to replace 'foo' with 'FOO' and 'bar' with 'BAR'. Then use UndoEdit to revert." --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        replaced 2 occurrences
+        assistant-function: UndoEdit
+        Reverted last edit
+      timeout: 45000
+    - name: Cleanup
+      bash: rm -f test-multi-undo.txt
+    optional: needsAI
+
+  - name: ReplaceMultipleInFile validates uniqueness of patterns
+    steps:
+    - name: Run test
+      bash: |
+        echo "test test test" > test-unique.txt
+        cycod --input "use ReplaceMultipleInFile on test-unique.txt to replace 'test' with 'TEST' (but 'test' appears multiple times, so should fail)" --auto-approve '*'
+      expect-regex: |
+        assistant-function: ReplaceMultipleInFile
+        Multiple matches found.*must be unique
+        No changes made
+      timeout: 30000
+    - name: Cleanup
+      bash: rm -f test-unique.txt
+    optional: needsAI