@@ -30,8 +30,9 @@ type writeTool struct {
3030}
3131
3232type WriteResponseMetadata struct {
33− Additions int `json:"additions"`
34− Removals int `json:"removals"`
33+ Diff string `json:"diff"`
34+ Additions int `json:"additions"`
35+ Removals int `json:"removals"`
3536}
3637
3738const (
@@ -128,12 +129,12 @@ func (w *writeTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error
128129 return NewTextErrorResponse(fmt.Sprintf("File %s already contains the exact content. No changes made.", filePath)), nil
129130 }
130131 } else if !os.IsNotExist(err) {
131− return NewTextErrorResponse(fmt.Sprintf("Failed to access file: %s", err)), nil
132+ return ToolResponse{}, fmt.Errorf("error checking file: %w", err)
132133 }
133134
134135 dir := filepath.Dir(filePath)
135136 if err = os.MkdirAll(dir, 0o755); err != nil {
136− return NewTextErrorResponse(fmt.Sprintf("Failed to create parent directories: %s", err)), nil
137+ return ToolResponse{}, fmt.Errorf("error creating directory: %w", err)
137138 }
138139
139140 oldContent := ""
@@ -146,7 +147,7 @@ func (w *writeTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error
146147
147148 sessionID, messageID := GetContextValues(ctx)
148149 if sessionID == "" || messageID == "" {
149− return NewTextErrorResponse("session ID or message ID is missing"), nil
150+ return ToolResponse{}, fmt.Errorf("session_id and message_id are required")
150151 }
151152 diff, stats, err := git.GenerateGitDiffWithStats(
152153 removeWorkingDirectoryPrefix(filePath),
@@ -154,7 +155,7 @@ func (w *writeTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error
154155 params.Content,
155156 )
156157 if err != nil {
157− return NewTextErrorResponse(fmt.Sprintf("Failed to get file diff: %s", err)), nil
158+ return ToolResponse{}, fmt.Errorf("error generating diff: %w", err)
158159 }
159160 p := w.permissions.Request(
160161 permission.CreatePermissionRequest{
@@ -169,12 +170,12 @@ func (w *writeTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error
169170 },
170171 )
171172 if !p {
172− return NewTextErrorResponse(fmt.Sprintf("Permission denied to create file: %s", filePath)), nil
173+ return ToolResponse{}, permission.ErrorPermissionDenied
173174 }
174175
175176 err = os.WriteFile(filePath, []byte(params.Content), 0o644)
176177 if err != nil {
177− return NewTextErrorResponse(fmt.Sprintf("Failed to write file: %s", err)), nil
178+ return ToolResponse{}, fmt.Errorf("error writing file: %w", err)
178179 }
179180
180181 recordFileWrite(filePath)
@@ -186,6 +187,7 @@ func (w *writeTool) Run(ctx context.Context, call ToolCall) (ToolResponse, error
186187 result += getDiagnostics(filePath, w.lspClients)
187188 return WithResponseMetadata(NewTextResponse(result),
188189 WriteResponseMetadata{
190+ Diff: diff,
189191 Additions: stats.Additions,
190192 Removals: stats.Removals,
191193 },