# Prompt Bloat

> Every bug fix adds a sentence to the system prompt — nothing ever gets removed — until the prompt is unmaintainable and full of contradictions.

- **Category**: Agentic AI
- **Subcategory**: Anti-Patterns
- **Canonical URL**: https://designpattern.fyi/patterns/prompt_bloat/

---

## Description
**Intent**: Treating the system prompt as a scratch pad for bug fixes — appending forever, removing never, because removing a line feels riskier than leaving it.

**Context**: The agent has been live for months. Each complaint adds an instruction. Nobody owns the prompt as a whole. A year later it''s 2,000 lines, no single person understands it end to end, and the model is resolving contradictory instructions at random.

**Solution**: Treat the prompt like code — PR review, eval gate on length, quarterly pruning sprints. Lift recurring procedures into agent-skills. Move stable rules into a constitutional charter. See prompt-versioning, agent-skills.



## Use Cases
- Never use this; treat unbounded prompt growth as a process failure, not normal maintenance.
- Use prompt-versioning and eval gates on length to keep prompts in budget.
- Lift recurring procedures into agent-skills and stable rules into a constitutional charter.






## Trade-offs




### Considerations & Drawbacks

- Token cost per turn rises monotonically

- Every prompt edit blows the KV-cache

- Contradictory instructions accumulate — and the model picks one at random







---
**Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/prompt-bloat/)