What is the Bus Factor?
Bus Factor: A classic engineering metric representing the risk of losing critical knowledge. In the context of AI-assisted development, the Bus Factor often drops dangerously low—even reaching zero—because "The AI wrote the code and no human truly understands it."
The "Bus Factor < 1" Phenomenon
In a traditional project, if the lead dev leaves, someone else can eventually read the code. In an AI project built with Vibe Coding, the codebase can become a collection of Magic Black Boxes.
If the person who prompted those boxes leaves, and they didn't document the intent or rationale, the remaining team may own a system they literally cannot maintain. This is effectively a Bus Factor of Zero: the project is alive, but its "soul" (the comprehension) is gone.
Why AI Makes it Worse
- Generation Speed: AI can generate code faster than humans can document or share it.
- Opaque Logic: AI patterns are often non-standard, making "manual archaeology" difficult for successors.
- Lost Chat Logs: The reasoning often lives in individual, ephemeral chat histories rather than in the repository.
The Statistics
How to Increase Your Bus Factor
The Clean Vibe methodology focuses on Knowledge Preservation:
- ADRs (Architectural Decision Records): Document the "Why" in the repo.
- The Explain Rule: No one merges code they can't explain to someone else.
- Pair Prompting: Human + Human + AI sessions to ensure shared understanding.
- Memory Files: Persistent context documents that survive individual chat sessions.
Related Terms
- Comprehension Debt: The reason for a low bus factor.
- Team Debt: The broader category of risk.
- Digital Archaeologist: The person you hire when your bus factor was too low.
Book Reference
- Chapter 9: Team Chaos — how AI fragments team knowledge.
- Chapter 12: The Handover — what happens when the bus factor hits zero.