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No. 2 · 5 October 2026

This week in Claude

  1. 2.1
    Prompting · 2026-09-28

    Anthropic's guide to prompting Claude Opus 5.5

    It lists how Opus 5.5 behaves differently from Opus 5, including how to pick an effort level and what to change if you ran with thinking turned off.

    Try it: If turns got longer or costlier since you switched to Opus 5.5, read its "Calibrate effort" section first.

    platform.claude.com ↗
  2. 2.2
    API · 2026-10-01

    The Models API now says which model line each model belongs to

    GET /v1/models returns a line field (for example opus), so you can group models without parsing their ids.

    Try it: Nothing to do unless your code guesses a model's family from its name.

    platform.claude.com ↗
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