generated: '2026-10-03'
method: searched
generator: extract-docs-artifacts.py (local)
source: https://platform.claude.com/docs/en/release-notes/overview
sources:
- https://platform.claude.com/docs/en/release-notes/overview
- https://platform.claude.com/docs/en/about-claude/models/migration-guide
- https://platform.claude.com/docs/en/managed-agents/migration
- https://docs.cloud.google.com/docs/migration
entries:
- breaking: false
  highlights:
  - We announced the deprecation of the Claude Sonnet 4.5 model ( claude-sonnet-4-5-20250929 ), with retirement on the Claude API scheduled for
    November 30, 2026.
  date: '2026-09-30'
- breaking: true
  highlights:
  - We've launched Claude Sonnet 5.5 ( claude-sonnet-5-5 ).
  - Code written for Claude Sonnet 5 can break on Claude Sonnet 5.5 in five ways.
  - 'To turn off up-front thinking, send thinking: {"type": "between_tools"} instead of "disabled" , at high effort or below.'
  date: '2026-09-28'
- breaking: false
  highlights:
  - We're resuming billing for refusals that arrive before any output when stop_details.category is "bio" , "frontier_llm" , or "reasoning_extraction".
  date: '2026-09-24'
- breaking: false
  highlights:
  - Cache diagnostics is out of beta on the Claude API and no longer requires the cache-diagnosis-2026-04-07 beta header.
  date: '2026-09-23'
- breaking: true
  highlights:
  - We've launched Claude Opus 5.5 ( claude-opus-5-5 ), a model for long-running agentic coding and knowledge work.
  - 'On Claude Opus 5.5, thinking can''t be disabled: thinking: {"type": "disabled"} and thinking: {"type": "enabled", ...} return a 400 error.'
  date: '2026-09-22'
- breaking: false
  highlights:
  - For cache diagnostics , a response to a request that sends the cache-diagnosis-2026-04-07 beta header now always includes the diagnostics
    field.
  date: '2026-09-18'
- breaking: false
  highlights:
  - The Messages API can now compact a conversation on demand on the Claude API, in beta with the compact-2026-09-04 beta header.
  date: '2026-09-14'
- breaking: false
  highlights:
  - 'Claude Managed Agents permission policies now include auto : the server evaluates each agent or MCP tool call and runs it, denies it, or
    pauses for your approval.'
  date: '2026-09-10'
- breaking: false
  highlights:
  - For cache diagnostics , the API now stores a request's fingerprint only when the request includes the diagnostics object.
  date: '2026-09-09'
note: Versioning scheme and current version are not specified on the provided pages.
docs: https://platform.claude.com/docs/en/release-notes/overview