Modelpeers

Claude Haiku 3.5 changelog

Every change to Claude Haiku 3.5 that Modelpeers has recorded, newest first, each with the source it came from. The record starts Sep 17, 2025.

All (1)Quality (1)

September 2025

Claude Code character

Claude Sonnet 4, Opus 4.1, Haiku 3.5

4 products from Anthropic

Quality report · Confirmed by the lab

Anthropic confirms three infrastructure bugs degraded Claude responses in August and September 2025

Anthropic published a postmortem saying three separate infrastructure bugs, the first introduced on August 5, intermittently degraded Claude's response quality until early September. A load balancing change on August 29 increased affected traffic. The Hacker News thread drew 381 points and 116 comments.

Who is affected:
Users of Claude Sonnet 4, Opus 4 and 4.1, and Haiku 3.5 on the Claude API and in Claude Code between August 5 and mid-September 2025.
What to do:
No action needed. Anthropic says all three bugs are fixed.

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