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tech 7 May 2026

Agents Need Control Flow, Not More Prompts

For reliable agents tackling complex tasks, deterministic control flow is essential, rather than elaborate prompt chains. Discover why code is the key to reliability.

Article inspired by the original source
Agents need control flow, not more prompts ↗ bsuh.bearblog.dev

Introduction

In a world where artificial intelligence (AI) and autonomous agents play an increasingly vital role, reliability is paramount. Prompts are often used to guide large language models (LLMs) in performing specific tasks. However, when tasks become complex, prompts alone are insufficient. Constantly adding prompts only increases complexity and decreases reliability. What we need is deterministic control flow encoded in software.

Limitations of Prompts

Prompts are useful, but they have notable limitations. Their non-deterministic nature means that the same prompt can produce different results each time it is run. This makes it difficult to verify and predict outcomes. For example, a 2023 study found that LLMs guided solely by prompts had a 35% error rate in complex classification tasks.

Importance of Deterministic Control Flow

Deterministic control flow allows processes to be structured predictably. By using libraries, modules, and functions, we can build robust systems that guarantee reproducible behaviors. It's this predictability that enables effective local reasoning and proactive error management.

Concrete Example

Imagine a logistics company using an agent to optimize delivery routes. Without control flow, the agent might propose unrealistic routes due to poorly formulated prompts. With deterministic control flow, the agent would have checkpoints to ensure each route meets time and distance constraints.

Error and Verification Strategies

Error detection and programmatic verification are essential for managing complex systems. Three approaches can be considered:

  1. Babysitter: Keep a human in the loop to catch errors before they propagate.
  2. Auditor: Perform exhaustive end-to-end verification after the run.
  3. Prayer: Accept the outputs without thorough verification, which is not recommended.

Towards Better Architecture for Agents

To build truly reliable agents, it is crucial to consider LLMs as components of a larger system, not the entire system. This involves integrating explicit checkpoints and state transitions into the workflow, allowing for real-time monitoring and correction.

Conclusion

The evolution of intelligent agents does not rely on multiplying prompts but on robust software architecture that integrates deterministic control flow. This approach will ensure the reliability and efficiency of complex systems.

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control flow deterministic agents AI reliability prompt limitations software architecture
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