AI Agent A/B Testing 2026

Changed one line of the System Prompt, and the Agent's behavior shifted dramatically. But how do you know if it's for the better or worse? A/B testing has the answer.

💡 What You Will Learn

Changed one line of the System Prompt, and the Agent's behavior shifted dramatically. But how do you know if it's for the better or worse? A/B testing has the answer.

# ID
if hash(user_id) % 2 == 0:
    result = agent_v1.run(query)
else:
    result = agent_v2.run(query)

Summary

import math

def required_sample(base_rate, min_effect, alpha=0.05, power=0.8):
    # base_rate: 75%
    # min_effect: 5%
    z_alpha = 1.96  # 95%
    z_beta = 0.84   # 80%
    p_pooled = base_rate * (1 - base_rate)
    n = (2 * (z_alpha + z_beta)**2 * p_pooled) / (min_effect**2)
    return int(n)