fix: prevent consecutive user messages on streaming retry

When a streaming error occurs after a tool use, the retry logic was adding a duplicate user message to the API conversation history, causing 400 errors.

The fix skips adding the user message on retry attempts since it was already added in the first attempt.

Author: daniel-lxs

src/core/task/Task.ts

@@ -1867,8 +1867,13 @@ export class Task extends EventEmitter<TaskEvents> implements TaskLike {
 			// results.
 			const finalUserContent = [...parsedUserContent, { type: "text" as const, text: environmentDetails }]
 
-			await this.addToApiConversationHistory({ role: "user", content: finalUserContent })
-			TelemetryService.instance.captureConversationMessage(this.taskId, "user")
+			// Only add user message to conversation history if this is NOT a retry attempt
+			// On retries, the user message was already added in the previous attempt
+			// This prevents consecutive user messages (including tool->user sequences) which cause 400 errors
+			if ((currentItem.retryAttempt ?? 0) === 0) {
+				await this.addToApiConversationHistory({ role: "user", content: finalUserContent })
+				TelemetryService.instance.captureConversationMessage(this.taskId, "user")
+			}
 
 			// Since we sent off a placeholder api_req_started message to update the
 			// webview while waiting to actually start the API request (to load