The 70% Wall: Why Vibe Coding Falls Apart
AI gets you 70% there fast. The last 30% — edge cases, security, production integration — is just as hard as ever. Here's what to do about it.
The 70% Problem
Addy Osmani (Google Chrome DevEx) identified the central tension of AI-assisted coding: AI produces 70% of a solution rapidly, but the remaining 30% — edge cases, security, production integration, error handling — is just as hard as it ever was.
With agentic tools in 2026, this has become the 80% problem: even more code generated, even faster, but the critical last 20% requires the same human judgment it always did.
The DORA Data
Google’s DORA 2025 Report confirmed this across thousands of engineering teams:
| Metric | Change |
|---|---|
| Individual output | +98% |
| PR review time | +91% |
| PR size | +154% |
| Bug rates | +9% |
| Change failure rates | +~30% |
| Net delivery | Flat |
Teams generate dramatically more code but spend so much time reviewing, debugging, and fixing that net delivery doesn’t improve. The speed gains are consumed by verification overhead.
Why Vibe Coding Breaks
Vibe coding — accepting AI output with minimal verification — works for prototypes and throwaway code. It fails for production because:
- AI doesn’t think adversarially. It generates functional code, not secure code. 60-70% of AI vulnerabilities are BLOCKER severity (Sonar).
- AI doesn’t understand your architecture. It uses patterns from its training data, not patterns from your codebase.
- AI compounds errors. One hallucination in turn 3 becomes 693 lines of fabricated code by turn 39 (Surge AI documented this).
- AI makes you feel productive while degrading quality. Stanford found developers WITH AI wrote less secure code while feeling MORE confident.
The Methodology Response
Paranoid Verification addresses the 70% wall directly:
- Plan before generating — the plan catches the 30% before code is written
- Verify at every step — 5 layers catch what AI misses
- Document understanding — forces comprehension of the full 100%, not just the easy 70%
- 2 corrections max — breaks the sunk cost spiral before it begins
The goal isn’t to reject AI. It’s to get the full 100% instead of a fast but incomplete 70%.