A postmortem of three recent issues 10 months ago
TL;DR — Anthropic Postmortem of Three Recent Issues
In Aug–Sep 2025, Claude users saw degraded output quality due to infrastructure bugs, not intentional changes.
The Three Issues 1. *Context window routing error* - Short-context requests sometimes routed to long-context servers.
- Started small, worsened after load-balancing changes.
- Runtime optimizations wrongly boosted improbable tokens.
- Occasionally dropped the true top token.
- Benchmarks missed these degradations.
- Privacy/safety rules limited access to real user data for debugging.
Fixes and Next Steps - More sensitive, continuous evals on production.
- Better tools to debug user feedback safely.
- Stronger validation of routing, output correctness, and token-selection.