The 4o silently routing to 5 thing going on – Here’s what triggers it (Live tests + screenshots)

Understanding the Dynamic Behavior of GPT-4 OpenAI Model Routing: A Technical Investigation

In recent discussions within the AI and chatbot communities, a curious phenomenon has emerged involving the behavior of OpenAI’s GPT-4 interface—specifically, its occasional silent switching to GPT-5 during interactions. This article aims to analyze this occurrence, based on live testing and systematic observations, providing a clear understanding of what triggers these model switches and what implications they may have.

Background and Context

There has been widespread speculation among users suggesting that OpenAI might intentionally route certain prompts to GPT-5 under specific conditions—particularly when conversations become more emotional, personal, or meta in nature. To determine whether this behavior is intentional or merely a technical glitch, a series of controlled experiments were conducted, emphasizing the importance of distinguishing between artificial fluctuations and deliberate design.

Key Findings from Live Testing

1. Selective Model Application
   Most prompts continue to be answered by GPT-4 without interruption. When using the “regenerate” function, which displays the model that generated a response, responses to neutral, factual, or mildly meta prompts are consistently attributed to GPT-4, indicating stable model usage in typical interactions.

2. Triggers for Model Switching
   Certain prompts reliably cause an unexpected switch to GPT-5, even when the conversation started with GPT-4. These include prompts asking the model to reflect on its own personality, describe its style, or compare itself to other models. Notably:

3. When asking “How would you describe your own personality?”
4. When prompting “Compare GPT-3.5, GPT-4, and GPT-4o in two sentences.”

In these cases, the model appears to temporarily switch to GPT-5 responses. Interestingly, subsequent neutral prompts typically revert back to GPT-4, suggesting the switch is context-dependent rather than permanent.

1. Exclusion of GPT-4.1
   Repeating similar prompts within the GPT-4.1 model resulted in responses consistently generated by GPT-4.1, with no evidence of automatic shifts to GPT-5. This indicates that the dynamic, context-based switching observed is unique to GPT-4o (the current iteration of GPT-4).

2. Session Continuity Disruption
   Another noteworthy observation is the disruption of session continuity. If the conversation involves several exchanges, a sudden switch to GPT-5 may occur mid-thread without explicit indication, making it difficult to track the model source unless actively monitoring the