Vision Agents Deprecate Stale UI Observations

A developer building a vision-driven UI agent on a MacBook Pro M4 with 48 GB RAM found that rich per-step UI observations accumulated in the LLM context caused fixation loops, contradictory states, and wrong actions. They implemented DeprecateOldScreenshotsMiddleware (LangChain-style) to replace older describe_webpage outputs with a deprecation sentinel, preserving chronology while keeping the latest detailed observation and reducing token bloat. The pattern prioritizes fresh UI state and domain-specific pruning.