diff --git a/internal/fsext/fileutil.go b/internal/fsext/fileutil.go
index 27b5e48f62e388d707cbfdf62780779e54129dab..e68888452cdc190cb1e6cbdec8d87760dd8e432c 100644
--- a/internal/fsext/fileutil.go
+++ b/internal/fsext/fileutil.go
@@ -233,3 +233,19 @@ func HasPrefix(path, prefix string) bool {
 	// If path is within prefix, Rel will not return a path starting with ".."
 	return !strings.HasPrefix(rel, "..")
 }
+
+// ToUnixLineEndings converts Windows line endings (CRLF) to Unix line endings (LF).
+func ToUnixLineEndings(content string) (string, bool) {
+	if strings.Contains(content, "\r\n") {
+		return strings.ReplaceAll(content, "\r\n", "\n"), true
+	}
+	return content, false
+}
+
+// ToWindowsLineEndings converts Unix line endings (LF) to Windows line endings (CRLF).
+func ToWindowsLineEndings(content string) (string, bool) {
+	if !strings.Contains(content, "\r\n") {
+		return strings.ReplaceAll(content, "\n", "\r\n"), true
+	}
+	return content, false
+}
diff --git a/internal/llm/tools/edit.go b/internal/llm/tools/edit.go
index fd9ed81d55bc96e7b7767adad2f1186d88d97023..8cc3154ebab98ca34a49715d48b110caabc4ffe3 100644
--- a/internal/llm/tools/edit.go
+++ b/internal/llm/tools/edit.go
@@ -99,6 +99,7 @@ WINDOWS NOTES:
 - File paths should use forward slashes (/) for cross-platform compatibility
 - On Windows, absolute paths start with drive letters (C:/) but forward slashes work throughout
 - File permissions are handled automatically by the Go runtime
+- Always assumes \n for line endings. The tool will handle \r\n conversion automatically if needed.
 
 Remember: when making multiple file edits in a row to the same file, you should prefer to send all edits in a single message with multiple calls to this tool, rather than multiple messages with a single call each.`
 )
@@ -299,7 +300,7 @@ func (e *editTool) deleteContent(ctx context.Context, filePath, oldString string
 		return ToolResponse{}, fmt.Errorf("failed to read file: %w", err)
 	}
 
-	oldContent := string(content)
+	oldContent, isCrlf := fsext.ToUnixLineEndings(string(content))
 
 	var newContent string
 	var deletionCount int
@@ -356,6 +357,10 @@ func (e *editTool) deleteContent(ctx context.Context, filePath, oldString string
 		return ToolResponse{}, permission.ErrorPermissionDenied
 	}
 
+	if isCrlf {
+		newContent, _ = fsext.ToWindowsLineEndings(newContent)
+	}
+
 	err = os.WriteFile(filePath, []byte(newContent), 0o644)
 	if err != nil {
 		return ToolResponse{}, fmt.Errorf("failed to write file: %w", err)
@@ -428,7 +433,7 @@ func (e *editTool) replaceContent(ctx context.Context, filePath, oldString, newS
 		return ToolResponse{}, fmt.Errorf("failed to read file: %w", err)
 	}
 
-	oldContent := string(content)
+	oldContent, isCrlf := fsext.ToUnixLineEndings(string(content))
 
 	var newContent string
 	var replacementCount int
@@ -487,6 +492,10 @@ func (e *editTool) replaceContent(ctx context.Context, filePath, oldString, newS
 		return ToolResponse{}, permission.ErrorPermissionDenied
 	}
 
+	if isCrlf {
+		newContent, _ = fsext.ToWindowsLineEndings(newContent)
+	}
+
 	err = os.WriteFile(filePath, []byte(newContent), 0o644)
 	if err != nil {
 		return ToolResponse{}, fmt.Errorf("failed to write file: %w", err)
diff --git a/internal/llm/tools/multiedit.go b/internal/llm/tools/multiedit.go
index 271603a5b0f97b78bb7dbe53b93a060cff48b9cc..50070ca613464a280e53ab964155b8d1e205dde5 100644
--- a/internal/llm/tools/multiedit.go
+++ b/internal/llm/tools/multiedit.go
@@ -335,7 +335,7 @@ func (m *multiEditTool) processMultiEditExistingFile(ctx context.Context, params
 		return ToolResponse{}, fmt.Errorf("failed to read file: %w", err)
 	}
 
-	oldContent := string(content)
+	oldContent, isCrlf := fsext.ToUnixLineEndings(string(content))
 	currentContent := oldContent
 
 	// Apply all edits sequentially
@@ -377,6 +377,10 @@ func (m *multiEditTool) processMultiEditExistingFile(ctx context.Context, params
 		return ToolResponse{}, permission.ErrorPermissionDenied
 	}
 
+	if isCrlf {
+		currentContent, _ = fsext.ToWindowsLineEndings(currentContent)
+	}
+
 	// Write the updated content
 	err = os.WriteFile(params.FilePath, []byte(currentContent), 0o644)
 	if err != nil {