feat: fix task polling issue

backend/docs/task_tool_improvements.md

@@ -0,0 +1,174 @@
+# Task Tool Improvements
+
+## Overview
+
+The task tool has been improved to eliminate wasteful LLM polling. Previously, when using background tasks, the LLM had to repeatedly call `task_status` to poll for completion, causing unnecessary API requests.
+
+## Changes Made
+
+### 1. Removed `run_in_background` Parameter
+
+The `run_in_background` parameter has been removed from the `task` tool. All subagent tasks now run asynchronously by default, but the tool handles completion automatically.
+
+**Before:**
+```python
+# LLM had to manage polling
+task_id = task(
+    subagent_type="bash",
+    prompt="Run tests",
+    description="Run tests",
+    run_in_background=True
+)
+# Then LLM had to poll repeatedly:
+while True:
+    status = task_status(task_id)
+    if completed:
+        break
+```
+
+**After:**
+```python
+# Tool blocks until complete, polling happens in backend
+result = task(
+    subagent_type="bash",
+    prompt="Run tests",
+    description="Run tests"
+)
+# Result is available immediately after the call returns
+```
+
+### 2. Backend Polling
+
+The `task_tool` now:
+- Starts the subagent task asynchronously
+- Polls for completion in the backend (every 2 seconds)
+- Blocks the tool call until completion
+- Returns the final result directly
+
+This means:
+- ✅ LLM makes only ONE tool call
+- ✅ No wasteful LLM polling requests
+- ✅ Backend handles all status checking
+- ✅ Timeout protection (5 minutes max)
+
+### 3. Removed `task_status` from LLM Tools
+
+The `task_status_tool` is no longer exposed to the LLM. It's kept in the codebase for potential internal/debugging use, but the LLM cannot call it.
+
+### 4. Updated Documentation
+
+- Updated `SUBAGENT_SECTION` in `prompt.py` to remove all references to background tasks and polling
+- Simplified usage examples
+- Made it clear that the tool automatically waits for completion
+
+## Implementation Details
+
+### Polling Logic
+
+Located in `src/tools/builtins/task_tool.py`:
+
+```python
+# Start background execution
+task_id = executor.execute_async(prompt)
+
+# Poll for task completion in backend
+while True:
+    result = get_background_task_result(task_id)
+
+    # Check if task completed or failed
+    if result.status == SubagentStatus.COMPLETED:
+        return f"[Subagent: {subagent_type}]\n\n{result.result}"
+    elif result.status == SubagentStatus.FAILED:
+        return f"[Subagent: {subagent_type}] Task failed: {result.error}"
+
+    # Wait before next poll
+    time.sleep(2)
+
+    # Timeout protection (5 minutes)
+    if poll_count > 150:
+        return "Task timed out after 5 minutes"
+```
+
+### Execution Timeout
+
+In addition to polling timeout, subagent execution now has a built-in timeout mechanism:
+
+**Configuration** (`src/subagents/config.py`):
+```python
+@dataclass
+class SubagentConfig:
+    # ...
+    timeout_seconds: int = 300  # 5 minutes default
+```
+
+**Thread Pool Architecture**:
+
+To avoid nested thread pools and resource waste, we use two dedicated thread pools:
+
+1. **Scheduler Pool** (`_scheduler_pool`):
+   - Max workers: 4
+   - Purpose: Orchestrates background task execution
+   - Runs `run_task()` function that manages task lifecycle
+
+2. **Execution Pool** (`_execution_pool`):
+   - Max workers: 8 (larger to avoid blocking)
+   - Purpose: Actual subagent execution with timeout support
+   - Runs `execute()` method that invokes the agent
+
+**How it works**:
+```python
+# In execute_async():
+_scheduler_pool.submit(run_task)  # Submit orchestration task
+
+# In run_task():
+future = _execution_pool.submit(self.execute, task)  # Submit execution
+exec_result = future.result(timeout=timeout_seconds)  # Wait with timeout
+```
+
+**Benefits**:
+- ✅ Clean separation of concerns (scheduling vs execution)
+- ✅ No nested thread pools
+- ✅ Timeout enforcement at the right level
+- ✅ Better resource utilization
+
+**Two-Level Timeout Protection**:
+1. **Execution Timeout**: Subagent execution itself has a 5-minute timeout (configurable in SubagentConfig)
+2. **Polling Timeout**: Tool polling has a 5-minute timeout (30 polls × 10 seconds)
+
+This ensures that even if subagent execution hangs, the system won't wait indefinitely.
+
+### Benefits
+
+1. **Reduced API Costs**: No more repeated LLM requests for polling
+2. **Simpler UX**: LLM doesn't need to manage polling logic
+3. **Better Reliability**: Backend handles all status checking consistently
+4. **Timeout Protection**: Two-level timeout prevents infinite waiting (execution + polling)
+
+## Testing
+
+To verify the changes work correctly:
+
+1. Start a subagent task that takes a few seconds
+2. Verify the tool call blocks until completion
+3. Verify the result is returned directly
+4. Verify no `task_status` calls are made
+
+Example test scenario:
+```python
+# This should block for ~10 seconds then return result
+result = task(
+    subagent_type="bash",
+    prompt="sleep 10 && echo 'Done'",
+    description="Test task"
+)
+# result should contain "Done"
+```
+
+## Migration Notes
+
+For users/code that previously used `run_in_background=True`:
+- Simply remove the parameter
+- Remove any polling logic
+- The tool will automatically wait for completion
+
+No other changes needed - the API is backward compatible (minus the removed parameter).

backend/src/agents/lead_agent/prompt.py

@@ -5,7 +5,7 @@ from src.skills import load_skills
 SUBAGENT_SECTION = """<subagent_system>
 **SUBAGENT MODE ENABLED**: You are running in subagent mode. Use the `task` tool proactively to delegate complex, multi-step tasks to specialized subagents.
 
-You can delegate tasks to specialized subagents using the `task` tool. Subagents run in isolated context and return concise results.
+You can delegate tasks to specialized subagents using the `task` tool. Subagents run in isolated context and return results when complete.
 
 **Available Subagents:**
 - **general-purpose**: For complex, multi-step tasks requiring exploration and action
@@ -14,7 +14,7 @@ You can delegate tasks to specialized subagents using the `task` tool. Subagents
 **When to Use task:**
 ✅ USE task when:
 - Output would be verbose (tests, builds, large file searches)
-- Multiple independent tasks can run in parallel (use `run_in_background=True`)
+- Complex tasks that would benefit from isolated context
 - Exploring/researching codebase extensively with many file reads
 
 ❌ DON'T use task when:
@@ -23,46 +23,31 @@ You can delegate tasks to specialized subagents using the `task` tool. Subagents
 - Need real-time feedback → main agent has streaming, subagents don't
 - Task depends on conversation context → subagents have isolated context
 
-**Background Task Protocol (CRITICAL):**
-When you use `run_in_background=True`:
-1. **You MUST wait for completion** - Background tasks run asynchronously, but you are responsible for getting results
-2. **Poll task status** - Call `task_status(task_id)` to check progress
-3. **Check status field** - Status can be: `pending`, `running`, `completed`, `failed`
-4. **Retry if still running** - If status is `pending` or `running`, wait a moment and call `task_status` again
-5. **Report results to user** - Only respond to user AFTER getting the final result
-
-**STRICT RULE: Never end the conversation with background tasks still running. You MUST retrieve all results first.**
+**How It Works:**
+- The task tool runs subagents asynchronously in the background
+- The backend automatically polls for completion (you don't need to poll)
+- The tool call will block until the subagent completes its work
+- Once complete, the result is returned to you directly
 
 **Usage:**
 ```python
-# Synchronous - wait for result (preferred for most cases)
-task(
+# Call task and wait for result
+result = task(
     subagent_type="general-purpose",
     prompt="Search all Python files for deprecated API usage and list them",
     description="Find deprecated APIs"
 )
 
-# Background - run in parallel (MUST poll for results)
-task_id = task(
+# Another example
+result = task(
     subagent_type="bash",
     prompt="Run npm install && npm run build && npm test",
-    description="Build and test frontend",
-    run_in_background=True
+    description="Build and test frontend"
 )
-# Extract task_id from the response
-# Then IMMEDIATELY start polling:
-while True:
-    status_result = task_status(task_id)
-    if "Status: completed" in status_result or "Status: failed" in status_result:
-        # Task finished, use the result
-        break
-    # Task still running, continue polling
-
-# Multiple parallel tasks
-task_id_1 = task(..., run_in_background=True)
-task_id_2 = task(..., run_in_background=True)
-# Poll BOTH tasks until complete before responding to user
+# Result is available immediately after the call returns
 ```
+
+**Note:** You can call multiple `task()` in parallel by using multiple tool calls in a single response. Each will run independently and return when complete.
 </subagent_system>"""
 
 SYSTEM_PROMPT_TEMPLATE = """

backend/src/subagents/config.py

@@ -15,6 +15,7 @@ class SubagentConfig:
         disallowed_tools: Optional list of tool names to deny.
         model: Model to use - 'inherit' uses parent's model.
         max_turns: Maximum number of agent turns before stopping.
+        timeout_seconds: Maximum execution time in seconds (default: 300 = 5 minutes).
     """
 
     name: str
@@ -24,3 +25,4 @@ class SubagentConfig:
     disallowed_tools: list[str] | None = field(default_factory=lambda: ["task"])
     model: str = "inherit"
     max_turns: int = 50
+    timeout_seconds: int = 300

backend/src/subagents/executor.py

@@ -3,7 +3,8 @@
 import logging
 import threading
 import uuid
-from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import Future, ThreadPoolExecutor
+from concurrent.futures import TimeoutError as FuturesTimeoutError
 from dataclasses import dataclass
 from datetime import datetime
 from enum import Enum
@@ -57,8 +58,12 @@ class SubagentResult:
 _background_tasks: dict[str, SubagentResult] = {}
 _background_tasks_lock = threading.Lock()
 
-# Thread pool for background execution
-_executor = ThreadPoolExecutor(max_workers=4, thread_name_prefix="subagent-")
+# Thread pool for background task scheduling and orchestration
+_scheduler_pool = ThreadPoolExecutor(max_workers=4, thread_name_prefix="subagent-scheduler-")
+
+# Thread pool for actual subagent execution (with timeout support)
+# Larger pool to avoid blocking when scheduler submits execution tasks
+_execution_pool = ThreadPoolExecutor(max_workers=8, thread_name_prefix="subagent-exec-")
 
 
 def _filter_tools(
@@ -214,6 +219,7 @@ class SubagentExecutor:
 
             # Run the agent using invoke for complete result
             # Note: invoke() runs until completion or interruption
+            # Timeout is handled at the execute_async level, not here
             final_state = agent.invoke(state, config=run_config)  # type: ignore[arg-type]
 
             logger.info(f"[trace={self.trace_id}] Subagent {self.config.name} completed execution")
@@ -290,26 +296,41 @@ class SubagentExecutor:
         with _background_tasks_lock:
             _background_tasks[task_id] = result
 
-        # Submit to thread pool
+        # Submit to scheduler pool
         def run_task():
             with _background_tasks_lock:
                 _background_tasks[task_id].status = SubagentStatus.RUNNING
                 _background_tasks[task_id].started_at = datetime.now()
 
             try:
-                exec_result = self.execute(task)
-                with _background_tasks_lock:
-                    _background_tasks[task_id].status = exec_result.status
-                    _background_tasks[task_id].result = exec_result.result
-                    _background_tasks[task_id].error = exec_result.error
-                    _background_tasks[task_id].completed_at = datetime.now()
+                # Submit execution to execution pool with timeout
+                execution_future: Future = _execution_pool.submit(self.execute, task)
+                try:
+                    # Wait for execution with timeout
+                    exec_result = execution_future.result(timeout=self.config.timeout_seconds)
+                    with _background_tasks_lock:
+                        _background_tasks[task_id].status = exec_result.status
+                        _background_tasks[task_id].result = exec_result.result
+                        _background_tasks[task_id].error = exec_result.error
+                        _background_tasks[task_id].completed_at = datetime.now()
+                except FuturesTimeoutError:
+                    logger.error(
+                        f"[trace={self.trace_id}] Subagent {self.config.name} execution timed out after {self.config.timeout_seconds}s"
+                    )
+                    with _background_tasks_lock:
+                        _background_tasks[task_id].status = SubagentStatus.FAILED
+                        _background_tasks[task_id].error = f"Execution timed out after {self.config.timeout_seconds} seconds"
+                        _background_tasks[task_id].completed_at = datetime.now()
+                    # Cancel the future (best effort - may not stop the actual execution)
+                    execution_future.cancel()
             except Exception as e:
+                logger.exception(f"[trace={self.trace_id}] Subagent {self.config.name} async execution failed")
                 with _background_tasks_lock:
                     _background_tasks[task_id].status = SubagentStatus.FAILED
                     _background_tasks[task_id].error = str(e)
                     _background_tasks[task_id].completed_at = datetime.now()
 
-        _executor.submit(run_task)
+        _scheduler_pool.submit(run_task)
         return task_id
 
 

backend/src/tools/builtins/__init__.py

@@ -1,6 +1,6 @@
 from .clarification_tool import ask_clarification_tool
 from .present_file_tool import present_file_tool
-from .task_tool import task_status_tool, task_tool
+from .task_tool import task_tool
 from .view_image_tool import view_image_tool
 
 __all__ = [
@@ -8,5 +8,4 @@ __all__ = [
     "ask_clarification_tool",
     "view_image_tool",
     "task_tool",
-    "task_status_tool",
 ]

backend/src/tools/builtins/task_tool.py

@@ -1,5 +1,7 @@
 """Task tool for delegating work to subagents."""
 
+import logging
+import time
 import uuid
 from typing import Literal
 
@@ -10,6 +12,8 @@ from src.agents.thread_state import ThreadState
 from src.subagents import SubagentExecutor, get_subagent_config
 from src.subagents.executor import SubagentStatus, get_background_task_result
 
+logger = logging.getLogger(__name__)
+
 
 @tool("task", parse_docstring=True)
 def task_tool(
@@ -18,7 +22,6 @@ def task_tool(
     prompt: str,
     description: str,
     max_turns: int | None = None,
-    run_in_background: bool = False,
 ) -> str:
     """Delegate a task to a specialized subagent that runs in its own context.
 
@@ -49,7 +52,6 @@ def task_tool(
         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.
         max_turns: Optional maximum number of agent turns. Defaults to subagent's configured max.
-        run_in_background: If True, run the task in background and return a task ID immediately.
     """
     # Get subagent configuration
     config = get_subagent_config(subagent_type)
@@ -100,61 +102,39 @@ def task_tool(
         trace_id=trace_id,
     )
 
-    if run_in_background:
-        # Start background execution
-        task_id = executor.execute_async(prompt)
-        return f"""Background task started with ID: {task_id} (trace: {trace_id})
+    # Start background execution (always async to prevent blocking)
+    task_id = executor.execute_async(prompt)
+    logger.info(f"[trace={trace_id}] Started background task {task_id}, polling for completion...")
 
-⚠️ IMPORTANT: You MUST poll this task until completion before responding to the user.
+    # Poll for task completion in backend (removes need for LLM to poll)
+    poll_count = 0
+    last_status = None
 
-Next steps:
-1. Call task_status("{task_id}") to check progress
-2. If status is "pending" or "running", wait briefly and call task_status again
-3. Continue polling until status is "completed" or "failed"
-4. Only then report results to the user
+    while True:
+        result = get_background_task_result(task_id)
 
-DO NOT end the conversation without retrieving the task result."""
+        if result is None:
+            logger.error(f"[trace={trace_id}] Task {task_id} not found in background tasks")
+            return f"Error: Task {task_id} disappeared from background tasks"
 
-    # Synchronous execution
-    result = executor.execute(prompt)
+        # Log status changes for debugging
+        if result.status != last_status:
+            logger.info(f"[trace={trace_id}] Task {task_id} status: {result.status.value}")
+            last_status = result.status
 
-    if result.status == SubagentStatus.COMPLETED:
-        return f"[Subagent: {subagent_type} | trace={result.trace_id}]\n\n{result.result}"
-    elif result.status == SubagentStatus.FAILED:
-        return f"[Subagent: {subagent_type} | trace={result.trace_id}] Task failed: {result.error}"
-    else:
-        return f"[Subagent: {subagent_type} | trace={result.trace_id}] Unexpected status: {result.status.value}"
+        # Check if task completed or failed
+        if result.status == SubagentStatus.COMPLETED:
+            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:
+            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
+        time.sleep(10)  # Poll every 10 seconds
+        poll_count += 1
 
-@tool("task_status", parse_docstring=True)
-def task_status_tool(
-    task_id: str,
-) -> str:
-    """Check the status of a background task and retrieve its result.
-
-    Use this tool to check on tasks that were started with run_in_background=True.
-
-    Args:
-        task_id: The task ID returned when starting the background task.
-    """
-    result = get_background_task_result(task_id)
-
-    if result is None:
-        return f"Error: No task found with ID '{task_id}'"
-
-    status_str = f"Task ID: {result.task_id}\nTrace ID: {result.trace_id}\nStatus: {result.status.value}"
-
-    if result.started_at:
-        status_str += f"\nStarted: {result.started_at.isoformat()}"
-
-    if result.completed_at:
-        status_str += f"\nCompleted: {result.completed_at.isoformat()}"
-
-    if result.status == SubagentStatus.COMPLETED and result.result:
-        status_str += f"\n\n✅ Task completed successfully.\n\nResult:\n{result.result}"
-    elif result.status == SubagentStatus.FAILED and result.error:
-        status_str += f"\n\n❌ Task failed.\n\nError: {result.error}"
-    elif result.status in (SubagentStatus.PENDING, SubagentStatus.RUNNING):
-        status_str += f"\n\n⏳ Task is still {result.status.value}. You MUST continue polling.\n\nAction required: Call task_status(\"{result.task_id}\") again after a brief wait."
-
-    return status_str
+        # Optional: Add timeout protection (e.g., max 5 minutes)
+        if poll_count > 30:  # 30 * 10s = 5 minutes
+            logger.warning(f"[trace={trace_id}] Task {task_id} timed out after {poll_count} polls")
+            return f"Task timed out after 5 minutes. Status: {result.status.value}"

backend/src/tools/tools.py

@@ -4,7 +4,7 @@ from langchain.tools import BaseTool
 
 from src.config import get_app_config
 from src.reflection import resolve_variable
-from src.tools.builtins import ask_clarification_tool, present_file_tool, task_status_tool, task_tool, view_image_tool
+from src.tools.builtins import ask_clarification_tool, present_file_tool, task_tool, view_image_tool
 
 logger = logging.getLogger(__name__)
 
@@ -15,7 +15,7 @@ BUILTIN_TOOLS = [
 
 SUBAGENT_TOOLS = [
     task_tool,
-    task_status_tool,
+    # task_status_tool is no longer exposed to LLM (backend handles polling internally)
 ]
 
 
@@ -69,7 +69,7 @@ def get_available_tools(
     # Add subagent tools only if enabled via runtime parameter
     if subagent_enabled:
         builtin_tools.extend(SUBAGENT_TOOLS)
-        logger.info("Including subagent tools (task, task_status)")
+        logger.info("Including subagent tools (task)")
 
     # If no model_name specified, use the first model (default)
     if model_name is None and config.models: