Implementation:HKUDS AI Trader STOP SIGNAL Check

Knowledge Sources	AI-Trader
Domains	LLM_Agents, Control_Flow
Last Updated	2026-02-09 14:00 GMT

Overview

Pattern implementation for detecting the agent's finish signal in LLM output to terminate the trading session reasoning loop.

Description

The STOP_SIGNAL is defined as the string "<FINISH_SIGNAL>" in prompts/agent_prompt.py (L23). It is injected into the system prompt template: "When you think your task is complete, output {STOP_SIGNAL}". In the trading loop at base_agent.py:L490, the check is a simple string containment: if STOP_SIGNAL in agent_response, break.

Usage

This pattern is checked at every iteration of the trading session loop after extracting the final assistant response. If detected, the loop exits and proceeds to _handle_trading_result().

Code Reference

Source Location

• Repository: AI-Trader
• File: agent/base_agent/base_agent.py (check at L490), prompts/agent_prompt.py (definition at L23)

Signature

# Definition (prompts/agent_prompt.py:L23):
STOP_SIGNAL = "<FINISH_SIGNAL>"

# Usage in system prompt template (L57-58):
# "When you think your task is complete, output\n{STOP_SIGNAL}"

# Check in trading loop (base_agent.py:L490):
if STOP_SIGNAL in agent_response:
    break  # Exit the multi-step reasoning loop

Import

from prompts.agent_prompt import STOP_SIGNAL

I/O Contract

Inputs

Name	Type	Required	Description
agent_response	str	Yes	Final assistant content from extract_conversation(response, "final")
STOP_SIGNAL	str	Constant	"<FINISH_SIGNAL>" sentinel token

Outputs

Name	Type	Description
detected	bool	True if STOP_SIGNAL found in agent_response (triggers loop break)

Usage Examples

Check in Trading Loop

from prompts.agent_prompt import STOP_SIGNAL
from tools.general_tools import extract_conversation

response = await self._ainvoke_with_retry(message)
agent_response = extract_conversation(response, "final")

if STOP_SIGNAL in agent_response:
    # Agent is done reasoning for today
    break

Related Pages

Implements Principle

• Principle:HKUDS_AI_Trader_Finish_Signal_Detection