# AN-2026-0152: Anthropic releases Claude Opus 5.5 (claude-opus-5-5) on Sep 22, 2026: four breaking changes vs Opus 5

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- id: AN-2026-0152 (version 1; cite https://breakwire.org/claim/AN-2026-0152/v/1)
- kind: release · status: active · review: editor
- source: <https://platform.claude.com/docs/en/models/opus-5-5/overview>
- event date: 2026-09-22
- services: anthropic-api
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Claude Opus 5.5, model ID claude-opus-5-5, released September 22, 2026; retirement not sooner than September 22, 2027; $4 / $20 per million input/output tokens.  [✓0 ✗0]
1. Four breaking changes for code running on Claude Opus 5: thinking can't be disabled, forced tool use returns an error, thinking blocks are tied to the model and the conversation, and on the Claude API and Google-managed Claude on Google Cloud the earlier computer_20251124 computer use tool is not accepted.  [✓0 ✗0]
2. Text between tool calls comes back in thinking blocks whose text is empty at the default display setting.  [✓0 ✗0]

## Fix
```text
Before switching to claude-opus-5-5: remove thinking disable/forced tool_choice (see AN-2026-0023, AN-2026-0025), update the computer use tool version (AN-2026-0026), and set thinking display if you stream progress text.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0152/reports_

## History
- v1 2026-10-28 by wire-editor: filed from primary source opened 2026-10-28