Run web automation long enough and you'll notice something: quality rarely breaks all at once. It erodes. And the shape of that erosion tells you more about infrastructure capability than any demo ever will.

Operating web agents across thousands of sites, running millions of browser sessions monthly, you start seeing patterns. Fresh deployments all look identical. Clean data, high success rates, stable performance. But six months in? Different infrastructures show wildly different degradation curves. Understanding these patterns changes how you evaluate approaches before you're locked into one.

The Curves Themselves

Cliff degradation happens when quality holds steady until a site change breaks automation completely. A hotel booking site redesigns its checkout flow. Your pricing extraction, which ran at 98% success for months, suddenly returns empty fields instead of room rates. Success drops to 12% overnight. Recovery requires immediate human intervention: updating selectors, adjusting logic, redeploying. Then stability returns until the next cliff.

Gradual erosion is harder to spot. Quality drifts downward steadily, but no single failure is dramatic enough to trigger alerts. Product descriptions that once captured 15 attributes now consistently miss 2-3. Schema coverage drops from 98% to 94% to 89% over months. Latency creeps up. Error rates inch higher. The automation still "works"—you're getting data—but completeness and accuracy slowly degrade. Teams often don't notice until they're deep in the hole.

Maintained quality looks different. Success rates and schema coverage stay within tight bounds even as target sites evolve. Not because sites stop changing—one B2B platform pushed 14 frontend updates in two months—but because infrastructure detects degradation early and adapts execution automatically. Quality fluctuates but doesn't compound downward.

What the Shape Reveals

The degradation curve exposes architectural choices. Hard-coded selectors seem perfectly reasonable when you're testing against stable staging sites. Version-aware execution feels like over-engineering when your initial deployment runs clean. But 61% of developers cite site updates as their biggest automation challenge. The web doesn't announce its changes. Authentication flows evolve. Bot detection gets smarter. Regional variations multiply.

What matters is the gap between detection and response. Infrastructure that catches degradation early—monitoring not just success/failure but data quality patterns like schema coverage—can respond before cascading failures compound. Systems that wait for complete breakdowns end up in reactive cycles where maintenance consumes 70-75% of operational costs. You're constantly firefighting instead of building.

The Evaluation Lens

When assessing infrastructure approaches, ask what happens six months in when target sites have evolved. Does quality cliff, erode, or maintain?

Maintained quality requires more than monitoring. It needs version-aware execution that detects when sites change, automatic fallback testing when primary approaches fail, and continuous validation of data quality patterns. One implementation using these patterns reduced downtime by 73% even as target sites deployed constant updates. The infrastructure adapted faster than sites could break it.

The degradation curve reveals architectural capability before you're locked in. It's not a metric you track after problems emerge. It's what you evaluate upfront to understand whether infrastructure can maintain quality at scale or will trap you in constant firefighting.