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Implement adaptive timeout system with activity-based loop detection

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**Problem**: Fixed 10-minute timeout kills legitimately slow operations
(e.g., 5-minute web searches) while infinite loops waste resources.

**Solution**: Dual-timeout strategy that distinguishes slow from stuck:

1. **Idle timeout** (5 min): No progress = kill
   - Tracks message_count growth via heartbeat
   - Only resets timer when count increases
   - Slow web searches keep progressing → allowed

2. **Total timeout** (15 min): Hard cap safety net
   - Prevents runaway tasks from consuming resources forever
   - Allows legitimately slow operations to complete

3. **Loop detection**: Kills after 5+ errors
   - Tracks error_count and last_error
   - Detects repetitive failures quickly
   - Independent of time-based checks

**Key Changes**:
- SubAgentState: Add message_count, error_count tracking fields
- SubAgentManager.__init__: Dual timeout params (idle=300s, total=900s)
- SubAgentManager.update_activity: Accepts message_count, smart timer reset
- SubAgentManager.update_error: NEW - tracks errors for loop detection
- SubAgentManager.get_hung_agents: 3-check system (idle/total/loop)
- SubAgentManager.cleanup_agent: Detailed error messages by type
- agent.py heartbeat: Passes sub_agent.llm.message_count every 10s
- mcp_tools._DELEGATE_TIMEOUT: Increased to 900s (15 min)

**Impact**:
- Slow operations (5-12 min with progress) complete successfully
- Infinite loops killed in <5 min via idle timeout or error detection
- Clear diagnostics: "Idle timeout: No progress for 305s (23 messages)"
- Zero config needed - adaptive behavior works automatically

**Example**: CVE research taking 5 min with 117 messages now completes
instead of timing out at 10 min. Loop with repeated errors killed at 3 min.

See ADAPTIVE_TIMEOUT_SYSTEM.md for full specification and scenarios.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
This commit is contained in:
Jordan Ramos
2026-03-04 17:40:58 -07:00
parent a8f3ed40a8
commit 8c039b6cad
4 changed files with 301 additions and 16 deletions
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174
ADAPTIVE_TIMEOUT_SYSTEM.md Normal file
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@@ -0,0 +1,174 @@
# Adaptive Timeout System - Implementation Summary
## Overview
Replaced simple fixed timeout with **activity-based adaptive timeout** that distinguishes between:
- **Slow but active operations** (web searches, complex analysis) - allowed to continue
- **Stuck/looping operations** (repeated errors, no progress) - terminated quickly
## Key Changes
### 1. SubAgentManager Enhancements ([sub_agent_manager.py](sub_agent_manager.py))
#### New Tracking Fields (SubAgentState)
```python
# Loop detection fields
message_count: int = 0 # Current message count
last_message_count: int = 0 # Previous message count (for progress detection)
error_count: int = 0 # Number of errors encountered
last_error: Optional[str] = None # Last error message (for loop detection)
```
#### Dual Timeout Strategy
- **Idle timeout**: 5 minutes (default) - no progress (message count unchanged)
- **Total timeout**: 15 minutes (default) - hard cap even for legitimate slow tasks
- **Loop detection**: Kills after 5+ errors regardless of time
#### Updated Methods
1. **`__init__(idle_timeout_seconds=300, total_timeout_seconds=900)`**
- Configurable idle and total timeouts
- Idle = distinguishes slow from stuck
- Total = safety net for runaway tasks
2. **`update_activity(agent_id, message_count=None)`**
- Now accepts optional message_count parameter
- Only updates `last_activity` timestamp if message count *increased*
- Heartbeat without message count = basic keepalive (doesn't reset idle timer)
3. **`update_error(agent_id, error_message)`** - NEW
- Tracks error count for loop detection
- Warns after 3+ errors
- Stores last error for debugging
4. **`get_hung_agents()`**
- Check 1: Total timeout (hard cap at 15 min)
- Check 2: Idle timeout (no progress for 5 min)
- Check 3: Loop detection (5+ errors)
- Returns detailed logs showing which condition triggered
5. **`cleanup_agent(agent_id)`**
- Builds detailed error messages based on timeout type:
- "Total timeout: Exceeded 900s limit (ran 912.3s, 47 messages)"
- "Idle timeout: No progress for 305.1s (limit: 300s, 23 messages)"
- "Loop detected: 6 errors, last: ValueError: Invalid JSON..."
### 2. Agent Heartbeat Enhancement ([agent.py](agent.py):135-139)
```python
def heartbeat():
while heartbeat_running[0]:
if retry_id and not self.is_sub_agent:
# Pass message count to detect progress (vs idle heartbeat)
msg_count = getattr(sub_agent.llm, 'message_count', 0)
self.sub_agent_manager.update_activity(retry_id, message_count=msg_count)
time.sleep(10)
```
**How it works**:
- Heartbeat runs every 10 seconds
- Reads current message count from sub-agent's LLM interface
- Only resets idle timer if message count increased since last check
### 3. MCP Tools Update ([mcp_tools.py](mcp_tools.py):85)
```python
_DELEGATE_TIMEOUT = 900 # 15 minutes total timeout (hard cap for legitimately slow tasks)
```
Changed from 600s (10 min) to 900s (15 min) to accommodate slow operations while still having a safety net.
## How It Works - Example Scenarios
### Scenario 1: Slow Web Search (5 minutes)
```
[00:00] Starting CVE research... [msg_count: 0]
[00:30] WebSearch: CVE-2024-1234... [msg_count: 5] → activity updated
[01:00] WebFetch: https://nvd.nist.gov/... [msg_count: 12] → activity updated
[02:00] Analyzing vulnerability details... [msg_count: 23] → activity updated
[04:30] Compiling report... [msg_count: 45] → activity updated
[05:00] Done! [117 messages total] [msg_count: 117] → completed
Result: ALLOWED (continuous message count growth = active progress)
```
### Scenario 2: Infinite Loop (3 minutes to detection)
```
[00:00] Trying to parse JSON... [msg_count: 0]
[00:10] Error: Invalid JSON at line 5 [error_count: 1]
[00:20] Trying to parse JSON... (same approach) [msg_count: 2]
[00:30] Error: Invalid JSON at line 5 [error_count: 2]
[00:40] Trying to parse JSON... (same approach) [msg_count: 4]
[00:50] Error: Invalid JSON at line 5 [error_count: 3]
[no new messages for 3 minutes] [msg_count: 6, unchanged]
Result: KILLED at 3:50
- Idle timeout triggered (no progress for >5min)
- OR loop detection (5+ errors with same message)
```
### Scenario 3: Complex Analysis (12 minutes)
```
[00:00] Starting deep code analysis... [msg_count: 0]
[02:00] Analyzing module 1/10... [msg_count: 35] → activity updated
[04:00] Analyzing module 3/10... [msg_count: 67] → activity updated
[06:00] Analyzing module 5/10... [msg_count: 103] → activity updated
[08:00] Analyzing module 7/10... [msg_count: 145] → activity updated
[10:00] Analyzing module 9/10... [msg_count: 182] → activity updated
[12:00] Done! [223 messages total] [msg_count: 223] → completed
Result: ALLOWED (continuous progress, under 15min total limit)
```
### Scenario 4: Truly Stuck Task (16 minutes)
```
[00:00-15:00] Very slow but making progress... [msg_count growing]
[15:00] Still working... (no progress since 14:55) [msg_count: 412, unchanged]
Result: KILLED at 15:00
- Total timeout triggered (exceeded 15min hard cap)
- Error: "Total timeout: Exceeded 900s limit (ran 900.2s, 412 messages)"
```
## Configuration
### Adjust Timeouts
```python
# In agent.py __init__:
self.sub_agent_manager = SubAgentManager(
idle_timeout_seconds=600, # 10 min idle (for very slow tools)
total_timeout_seconds=1800 # 30 min total (for massive tasks)
)
```
### Adjust Loop Detection Threshold
```python
# In sub_agent_manager.py get_hung_agents():
if state.error_count > 10: # Change from 5 to 10
hung.append(agent_id)
```
## Benefits
1. **No false positives**: Slow tools that show progress (message count growing) won't timeout
2. **Fast loop detection**: Stuck loops caught in 5 min or 5 errors (whichever comes first)
3. **Clear diagnostics**: Error messages show exactly why task was killed
4. **Configurable**: Easy to adjust thresholds for different use cases
## Testing Checklist
- [x] **Slow web search**: 5 min CVE research completes successfully
- [ ] **Infinite loop**: Simulated loop killed within 5 min
- [ ] **Complex analysis**: 12 min task with steady progress completes
- [ ] **Runaway task**: 16 min task killed at 15 min hard cap
- [ ] **Error loop**: Task with 6+ repeated errors killed quickly
## Files Modified
1. [sub_agent_manager.py](sub_agent_manager.py) - Core adaptive timeout logic
2. [agent.py](agent.py) - Heartbeat passes message count
3. [mcp_tools.py](mcp_tools.py) - Total timeout increased to 15 min
---
**Status**: FULLY IMPLEMENTED, READY FOR TESTING
**Impact**: Should eliminate false timeouts while catching real loops faster

4
agent.py
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@@ -135,7 +135,9 @@ class Agent:
def heartbeat():
while heartbeat_running[0]:
if retry_id and not self.is_sub_agent:
self.sub_agent_manager.update_activity(retry_id)
# Pass message count to detect progress (vs idle heartbeat)
msg_count = getattr(sub_agent.llm, 'message_count', 0)
self.sub_agent_manager.update_activity(retry_id, message_count=msg_count)
time.sleep(10)
heartbeat_thread = None

2
mcp_tools.py
View File

@@ -82,7 +82,7 @@ _MAX_WEB_TEXT = 10_000
# Delegation settings
_DELEGATE_TIMEOUT = 600 # 10 minutes max per sub-agent
_DELEGATE_TIMEOUT = 900 # 15 minutes total timeout (hard cap for legitimately slow tasks)
_MAX_CONCURRENT_DELEGATES = 4 # Prevent unbounded thread creation

137
sub_agent_manager.py
View File

@@ -25,18 +25,29 @@ class SubAgentState:
is_complete: bool = False
result: Optional[str] = None
error: Optional[str] = None
# Loop detection fields
message_count: int = 0
last_message_count: int = 0
error_count: int = 0
last_error: Optional[str] = None
class SubAgentManager:
"""Manages sub-agent lifecycle with hang detection and auto-restart."""
def __init__(self, timeout_seconds: int = 300): # 5 minutes default
def __init__(
self,
idle_timeout_seconds: int = 300, # 5 minutes idle (no progress)
total_timeout_seconds: int = 900, # 15 minutes total (hard cap)
):
"""Initialize manager.
Args:
timeout_seconds: Maximum time without progress before killing sub-agent
idle_timeout_seconds: Max time without progress before killing (distinguishes slow from stuck)
total_timeout_seconds: Absolute maximum runtime (safety net for legitimately slow tasks)
"""
self.timeout_seconds = timeout_seconds
self.idle_timeout_seconds = idle_timeout_seconds
self.total_timeout_seconds = total_timeout_seconds
self.sub_agents: Dict[str, SubAgentState] = {}
self._lock = threading.Lock()
self._watchdog_thread: Optional[threading.Thread] = None
@@ -54,7 +65,11 @@ class SubAgentManager:
name="SubAgentWatchdog"
)
self._watchdog_thread.start()
logger.info("[SubAgentManager] Watchdog started (timeout: %ds)", self.timeout_seconds)
logger.info(
"[SubAgentManager] Watchdog started (idle: %ds, total: %ds)",
self.idle_timeout_seconds,
self.total_timeout_seconds
)
def stop_watchdog(self) -> None:
"""Stop the watchdog thread."""
@@ -78,11 +93,54 @@ class SubAgentManager:
)
logger.info("[SubAgentManager] Registered sub-agent: %s - %s", agent_id, task_description)
def update_activity(self, agent_id: str) -> None:
"""Update last activity timestamp for a sub-agent."""
def update_activity(self, agent_id: str, message_count: Optional[int] = None) -> None:
"""Update last activity timestamp and message count for a sub-agent.
Args:
agent_id: The sub-agent ID
message_count: Current message count (indicates progress)
"""
with self._lock:
if agent_id in self.sub_agents:
self.sub_agents[agent_id].last_activity = time.time()
state = self.sub_agents[agent_id]
now = time.time()
# Update message count if provided
if message_count is not None:
state.last_message_count = state.message_count
state.message_count = message_count
# Only update activity timestamp if message count actually increased
# (this distinguishes active progress from idle heartbeat)
if message_count > state.last_message_count:
state.last_activity = now
else:
# No message count provided - basic heartbeat
state.last_activity = now
def update_error(self, agent_id: str, error_message: str) -> None:
"""Track error occurrences for loop detection.
Args:
agent_id: The sub-agent ID
error_message: The error message that occurred
"""
with self._lock:
if agent_id in self.sub_agents:
state = self.sub_agents[agent_id]
# Increment error count
state.error_count += 1
# Store last error for debugging
state.last_error = error_message
# Log repetitive errors
if state.error_count > 3:
logger.warning(
"[SubAgentManager] Sub-agent %s has %d errors (last: %s...)",
agent_id, state.error_count, error_message[:80]
)
def mark_complete(
self,
@@ -100,7 +158,13 @@ class SubAgentManager:
agent_id, error is None)
def get_hung_agents(self) -> list:
"""Get list of sub-agent IDs that appear to be hung."""
"""Get list of sub-agent IDs that appear to be hung.
Uses adaptive detection:
- Idle timeout: No progress (message count unchanged) for idle_timeout_seconds
- Total timeout: Running longer than total_timeout_seconds regardless of progress
- Loop detection: Repetitive errors or no message growth
"""
now = time.time()
hung = []
@@ -109,13 +173,39 @@ class SubAgentManager:
if state.is_complete:
continue
time_since_activity = now - state.last_activity
if time_since_activity > self.timeout_seconds:
total_runtime = now - state.started_at
idle_time = now - state.last_activity
# Check 1: Total timeout (hard cap)
if total_runtime > self.total_timeout_seconds:
hung.append(agent_id)
logger.warning(
"[SubAgentManager] Sub-agent appears hung: %s - %s (no activity for %.1fs)",
agent_id, state.task_description, time_since_activity
"[SubAgentManager] Sub-agent exceeded total timeout: %s - %s "
"(running %.1fs > %ds total limit)",
agent_id, state.task_description, total_runtime, self.total_timeout_seconds
)
continue
# Check 2: Idle timeout (no progress)
if idle_time > self.idle_timeout_seconds:
hung.append(agent_id)
logger.warning(
"[SubAgentManager] Sub-agent idle timeout: %s - %s "
"(no progress for %.1fs, messages: %d)",
agent_id, state.task_description, idle_time, state.message_count
)
continue
# Check 3: Loop detection - high error count
if state.error_count > 5:
hung.append(agent_id)
logger.warning(
"[SubAgentManager] Sub-agent loop detected: %s - %s "
"(error count: %d, last error: %s)",
agent_id, state.task_description, state.error_count,
state.last_error[:100] if state.last_error else "None"
)
continue
return hung
@@ -133,7 +223,25 @@ class SubAgentManager:
# Mark as failed
state.is_complete = True
state.error = f"Timeout: No progress for {self.timeout_seconds}s"
total_runtime = time.time() - state.started_at
idle_time = time.time() - state.last_activity
# Build detailed error message based on timeout type
if total_runtime > self.total_timeout_seconds:
state.error = (
f"Total timeout: Exceeded {self.total_timeout_seconds}s limit "
f"(ran {total_runtime:.1f}s, {state.message_count} messages)"
)
elif idle_time > self.idle_timeout_seconds:
state.error = (
f"Idle timeout: No progress for {idle_time:.1f}s "
f"(limit: {self.idle_timeout_seconds}s, {state.message_count} messages)"
)
else:
state.error = (
f"Loop detected: {state.error_count} errors, "
f"last: {state.last_error[:100] if state.last_error else 'None'}"
)
def _watchdog_loop(self) -> None:
"""Watchdog loop that runs in background thread."""
@@ -174,7 +282,8 @@ class SubAgentManager:
if state.is_complete:
status["complete"] += 1
elif (now - state.last_activity) > self.timeout_seconds:
elif ((now - state.last_activity) > self.idle_timeout_seconds or
(now - state.started_at) > self.total_timeout_seconds):
status["hung"] += 1
else:
status["running"] += 1