- Launch of Claude Fable 5.2 and Claude Mythos 5.2 with 1 M‑token context, 128 k output, lower pricing ($8/$40 per MTok vs $10/$50) and availability on API, AWS, Google Cloud, Bedrock, and Microsoft Foundry.
- Mandatory prefix check and new computer_toolset_20260801 cause 400 errors for legacy prompt edits, older computer_20251124 tool (except Bedrock), and advisor compatibility, requiring code updates.
- Enforced 30‑day data retention and thinking‑block preservation rules; migration guidance provided.