4 files changed, 9 insertions, 1 deletions
diff --git a/packages/core/src/tools/edit.ts b/packages/core/src/tools/edit.ts
index 3317d460..ddb521be 100644
--- a/packages/core/src/tools/edit.ts
+++ b/packages/core/src/tools/edit.ts
@@ -467,10 +467,12 @@ Expectation for required parameters:
         }
       },
       createUpdatedParams: (
+        oldContent: string,
         modifiedProposedContent: string,
         originalParams: EditToolParams,
       ): EditToolParams => ({
         ...originalParams,
+        old_string: oldContent,
         new_string: modifiedProposedContent,
       }),
     };
diff --git a/packages/core/src/tools/modifiable-tool.test.ts b/packages/core/src/tools/modifiable-tool.test.ts
index 56c27fe0..850da02b 100644
--- a/packages/core/src/tools/modifiable-tool.test.ts
+++ b/packages/core/src/tools/modifiable-tool.test.ts
@@ -74,9 +74,10 @@ describe('modifyWithEditor', () => {
       getProposedContent: vi.fn().mockResolvedValue(proposedContent),
       createUpdatedParams: vi
         .fn()
-        .mockImplementation((modifiedContent, originalParams) => ({
+        .mockImplementation((oldContent, modifiedContent, originalParams) => ({
           ...originalParams,
           modifiedContent,
+          oldContent,
         })),
     };
 
@@ -153,6 +154,7 @@ describe('modifyWithEditor', () => {
       );
 
       expect(mockModifyContext.createUpdatedParams).toHaveBeenCalledWith(
+        currentContent,
         modifiedContent,
         mockParams,
       );
@@ -183,6 +185,7 @@ describe('modifyWithEditor', () => {
         updatedParams: {
           ...mockParams,
           modifiedContent,
+          oldContent: currentContent,
         },
         updatedDiff: 'mock diff content',
       });
diff --git a/packages/core/src/tools/modifiable-tool.ts b/packages/core/src/tools/modifiable-tool.ts
index 96fe176c..e935a704 100644
--- a/packages/core/src/tools/modifiable-tool.ts
+++ b/packages/core/src/tools/modifiable-tool.ts
@@ -29,6 +29,7 @@ export interface ModifyContext<ToolParams> {
   getProposedContent: (params: ToolParams) => Promise<string>;
 
   createUpdatedParams: (
+    oldContent: string,
     modifiedProposedContent: string,
     originalParams: ToolParams,
   ) => ToolParams;
@@ -98,6 +99,7 @@ function getUpdatedParams<ToolParams>(
   }
 
   const updatedParams = modifyContext.createUpdatedParams(
+    oldContent,
     newContent,
     originalParams,
   );
diff --git a/packages/core/src/tools/write-file.ts b/packages/core/src/tools/write-file.ts
index b19b00ac..87f6e21e 100644
--- a/packages/core/src/tools/write-file.ts
+++ b/packages/core/src/tools/write-file.ts
@@ -389,6 +389,7 @@ export class WriteFileTool
         return correctedContentResult.correctedContent;
       },
       createUpdatedParams: (
+        _oldContent: string,
         modifiedProposedContent: string,
         originalParams: WriteFileToolParams,
       ) => ({