Yesterday in AI: 23 April 2026 — GPT-5.5 Ships as Anthropic Admits 50-Day Claude Nerf

Anthropic confessed to three engineering mistakes that quietly degraded Claude Code for 50 days and reset all subscriber limits. Same day: OpenAI dropped GPT-5.5 at double the price with a 1M-token context window, and Alibaba’s 27B Qwen model beat its own 397B predecessor on coding.

By OMC Editorial on 2026-04-24

Anthropic published a frank postmortem confessing three separate changes quietly broke Claude Code for nearly seven weeks — the same day OpenAI shipped its priciest model yet and Alibaba’s leanest model shocked benchmark charts. Anthropic Admits 50-Day Claude Code Degradation On April 23, Anthropic published a postmortem at anthropic.com/engineering/april-23-postmortemhttps://www.anthropic.com/engineering/april-23-postmortem revealing three distinct engineering mistakes that degraded Claude Code from early March through April 20. Change 1 March 4: Engineers reduced Claude Code’s default reasoning effort from “high” to “medium” to cut UI latency. Users never consented to this tradeoff. Reverted April 7. Change 2 March 26: A caching optimization to clear idle-session thinking was bugged: it cleared context on every turn, making Claude seem forgetful all session long. Change 3 April 16: A system prompt tweak to reduce verbosity cut 3% off coding performance before being rolled back April 20. Anthropic reset usage limits for all subscribers on April 23 and launched @ClaudeDevs on X to explain product decisions going forward. The community response was sharp: developers had flagged degradation for weeks and were largely dismissed before the postmortem arrived. OpenAI Ships GPT-5.5 — 1M Context, Double the Price OpenAI released GPT-5.5https://techcrunch.com/2026/04/23/openai-chatgpt-gpt-5-5-ai-model-superapp/ on April 23, calling it “a new class of intelligence for real work and powering agents.” It is the first fully retrained base model since GPT-4.5, with a reworked architecture, new pretraining corpus, and agent-oriented objectives baked in throughout. Key numbers: 1M-token context window first in the OpenAI API lineup, priced at /0 per million input/output tokens — exactly double GPT-5.4’s rates. A Pro tier runs 0/80. The model is available immediately in ChatGPT Plus, Pro, Business, Enterprise and Codex; API access is imminent. OpenAI president Greg Broc