refactor: optimize task tool parameter order and improve task tracking

- Reorder task tool parameters to prioritize description first for better usability
- Add tool_call_id injection for better task traceability
- Use tool_call_id as task_id in executor for consistent tracking
- Simplify event messages by removing redundant task_type field
- Update task examples in prompt to reflect new parameter order

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/src/tools/builtins/task_tool.py

@@ -3,9 +3,9 @@
 import logging
 import time
 import uuid
-from typing import Literal
+from typing import Annotated, Literal
 
-from langchain.tools import ToolRuntime, tool
+from langchain.tools import InjectedToolCallId, ToolRuntime, tool
 from langgraph.typing import ContextT
 from langgraph.config import get_stream_writer
 
@@ -19,9 +19,10 @@ logger = logging.getLogger(__name__)
 @tool("task", parse_docstring=True)
 def task_tool(
     runtime: ToolRuntime[ContextT, ThreadState],
-    subagent_type: Literal["general-purpose", "bash"],
-    prompt: str,
     description: str,
+    prompt: str,
+    subagent_type: Literal["general-purpose", "bash"],
+    tool_call_id: Annotated[str, InjectedToolCallId],
     max_turns: int | None = None,
 ) -> str:
     """Delegate a task to a specialized subagent that runs in its own context.
@@ -49,9 +50,9 @@ def task_tool(
     - Tasks requiring user interaction or clarification
 
     Args:
-        subagent_type: The type of subagent to use.
-        prompt: The task description for the subagent. Be specific and clear about what needs to be done.
-        description: A short (3-5 word) description of the task for logging/display.
+        description: A short (3-5 word) description of the task for logging/display. ALWAYS PROVIDE THIS PARAMETER FIRST.
+        prompt: The task description for the subagent. Be specific and clear about what needs to be done. ALWAYS PROVIDE THIS PARAMETER SECOND.
+        subagent_type: The type of subagent to use. ALWAYS PROVIDE THIS PARAMETER THIRD.
         max_turns: Optional maximum number of agent turns. Defaults to subagent's configured max.
     """
     # Get subagent configuration
@@ -104,7 +105,8 @@ def task_tool(
     )
 
     # Start background execution (always async to prevent blocking)
-    task_id = executor.execute_async(prompt)
+    # Use tool_call_id as task_id for better traceability
+    task_id = executor.execute_async(prompt, task_id=tool_call_id)
     logger.info(f"[trace={trace_id}] Started background task {task_id}, polling for completion...")
 
     # Poll for task completion in backend (removes need for LLM to poll)
@@ -113,7 +115,7 @@ def task_tool(
 
     writer = get_stream_writer()
     # Send Task Started message'
-    writer({"type": "task_started", "task_id": task_id, "task_type": subagent_type, "description": description})
+    writer({"type": "task_started", "task_id": task_id, "description": description})
 
 
     while True:
@@ -121,7 +123,7 @@ def task_tool(
 
         if result is None:
             logger.error(f"[trace={trace_id}] Task {task_id} not found in background tasks")
-            writer({"type": "task_failed", "task_id": task_id, "task_type": subagent_type, "error": "Task disappeared from background tasks"})
+            writer({"type": "task_failed", "task_id": task_id, "error": "Task disappeared from background tasks"})
             return f"Error: Task {task_id} disappeared from background tasks"
 
         # Log status changes for debugging
@@ -131,21 +133,21 @@ def task_tool(
 
         # Check if task completed or failed
         if result.status == SubagentStatus.COMPLETED:
-            writer({"type": "task_completed", "task_id": task_id, "task_type": subagent_type, "result": result.result})
+            writer({"type": "task_completed", "task_id": task_id, "result": result.result})
             logger.info(f"[trace={trace_id}] Task {task_id} completed after {poll_count} polls")
             return f"Task Succeeded. Result: {result.result}"
         elif result.status == SubagentStatus.FAILED:
-            writer({"type": "task_failed", "task_id": task_id, "task_type": subagent_type, "error": result.error})
+            writer({"type": "task_failed", "task_id": task_id, "error": result.error})
             logger.error(f"[trace={trace_id}] Task {task_id} failed: {result.error}")
             return f"Task failed. Error: {result.error}"
 
         # Still running, wait before next poll
-        writer({"type": "task_running", "task_id": task_id, "task_type": subagent_type, "poll_count": poll_count})
+        writer({"type": "task_running", "task_id": task_id, "poll_count": poll_count})
         time.sleep(5)  # Poll every 5 seconds
         poll_count += 1
 
         # Optional: Add timeout protection (e.g., max 5 minutes)
         if poll_count > 60:  # 60 * 5s = 5 minutes
             logger.warning(f"[trace={trace_id}] Task {task_id} timed out after {poll_count} polls")
-            writer({"type": "task_timed_out", "task_id": task_id, "task_type": subagent_type})
+            writer({"type": "task_timed_out", "task_id": task_id})
             return f"Task timed out after 5 minutes. Status: {result.status.value}"