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Context Window Routing Bug Affecting 16% of Requests

8/10 High

A context window routing error caused requests to be misrouted to incorrect server configurations, with sticky routing amplifying the impact. At peak, 16% of Sonnet 4 requests were affected, with fix rollout spanning multiple platforms over weeks.

Claude Sonnet 4context windowload balancing
Category
networking
Workaround
none
Stage
deploy
Freshness
declining
Scope
single_lib
Upstream
wontfix
Recurring
No
Buyer Type
team
Maintainer
active

Sources

Collection History

Query: “What are the most common pain points with Anthropic API for developers in 2025?”3/30/2026

At the worst impacted hour on August 31, 16% of Sonnet 4 requests were affected... This meant that once a request was served by the incorrect server, subsequent follow-ups were likely to be served by the same incorrect server.

Created: 3/30/2026Updated: 3/30/2026