Vector-Based Prompts Enhance LLM Response Quality

Series Update: Vector-Based System Prompts Substantially Improve Response Quality in Open-Weight LLMs – New Preprint (Dec 23, 2025) + GitHub Artifacts

Recent advancements in vector-based system prompts have significantly enhanced the response quality of open-weight large language models (LLMs) without the need for fine-tuning or external tools. By using lightweight YAML system prompts to set immutable values like compassion and truth, and allowing behavioral scalars such as curiosity and clarity to be adjustable, the study achieved notable improvements in response metrics. These include a 37.8% increase in response length, a 60% rise in positive sentiment, and a 66.7% boost in structured formatting. The approach, tested on the GPT-OSS-120B MXFP4 model, also resulted in a remarkable 1100% increase in self-reflective notes, all while maintaining factual accuracy and lexical diversity comparable to the baseline. This method simplifies earlier complex techniques into a portable scalar-vector approach, making it easily applicable across various LLMs like Gemma, Llama-3.3, and GPT-OSS. The research invites feedback on the practical implications of these enhancements, particularly in domains such as coding assistance and safety testing, and explores preferences for using YAML, JSON, or plain text for prompt injection. This matters because it demonstrates a scalable and accessible way to improve AI alignment and response quality using consumer-grade hardware.

The recent advancements in vector-based system prompts for large language models (LLMs) present an intriguing development in the field of artificial intelligence. By focusing on prompt-based behavioral steering and simulated metacognition, these methods aim to enhance the response quality of open-weight LLMs without the need for fine-tuning or external tools. This approach is particularly significant because it allows for improvements in AI capabilities using consumer-grade hardware, making advanced AI functionalities more accessible to a broader audience. The ability to achieve substantial improvements in response quality through lightweight system prompts could democratize AI technology, enabling more people to leverage sophisticated AI models for various applications.

One of the key findings is the use of YAML system prompts to fix immutable values such as compassion and truth while allowing tunable behavioral scalars like curiosity and clarity. This method has shown remarkable improvements in response metrics, including a 37.8% increase in response length and a 60.0% rise in positive sentiment polarity. These enhancements suggest that vector-based prompts can significantly influence the way LLMs interact, providing more structured and empathetic responses. The implications of these findings are far-reaching, as they highlight a potential pathway to refining AI behavior without the complexities of reinforcement learning from human feedback (RLHF), which can be resource-intensive and challenging to implement.

The research also underscores the importance of self-reflective capabilities in AI, with a reported 1100% increase in self-reflective notes. This aspect of AI development is crucial as it aligns with the broader goal of creating AI systems that can understand and adapt their behavior based on context and feedback. The ability to self-reflect and adjust responses can lead to more meaningful interactions between AI and users, fostering trust and reliability in AI systems. Moreover, the fact that these improvements were achieved with factual accuracy and lexical diversity comparable to the vanilla baseline indicates that the enhancements do not come at the cost of essential communication qualities.

Exploring the practical applications of these advancements is essential for understanding their full potential. Testing vector-based system prompts in various domains, such as coding assistance and safety red-teaming, could reveal new opportunities for AI to contribute to different fields. Additionally, the choice between YAML, JSON, or plain text for implementing these prompts could impact their effectiveness and ease of use. As the AI community continues to experiment with and refine these techniques, feedback from those running large quantized models locally will be invaluable. This ongoing exploration of prompt-based methods highlights the dynamic nature of AI development and the continuous quest for more aligned and capable AI systems.

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