Claude Opus 5.5

Available · Language, Multimodal, Reasoning

Claude Opus 5.5 is a language model in Anthropic's Claude Opus line and, according to Anthropic, the first model of its Claude 5.5 family, released on 22 September 2026 on all platforms. It costs less per token than Claude Opus 5, has adaptive thinking that cannot be switched off, is available with zero data retention and carries Anthropic's output watermarking. [1] [2]September 22, 2026 Primary source

Timeline of Claude Opus 5.5 →

Claims and evidence

Released 22 September 2026 Primary source[1] [3]Availability: Released

Status Available Primary source[4]Compare models table [3]Availability [5]Model status table

Successor of Claude Opus 5 Primary source[1]Introduction [6]

Change · Other Priced at 4 USD input and 20 USD output per million tokens, down from 5 and 25 USD for Opus 5; cache reads cost 0.20 USD.Compared with Claude Opus 5 Primary source[1] [2]September 22, 2026
Change · Reasoning Thinking can no longer be switched off; its depth is set with the effort parameter.Compared with Claude Opus 5 Primary source[2]September 22, 2026
Change · Tool use Forced tool choice (tool_choice types any and tool) returns an error.Compared with Claude Opus 5 Primary source[2]September 22, 2026
Change · Safety Deployed with safeguards similar to those on Claude Fable 5.1 and with Anthropic's output watermarking.Compared with Claude Opus 5 Primary source[1]

Input text, image Primary source[3]Capabilities: Input and output
Output text Primary source[3]Capabilities: Input and output
Context window 1M tokens Primary source[3]Capabilities: Context window
Parameters Not disclosedNot disclosed by Anthropic. No claim madeNo source
Access API, consumer app, cloud partner Primary source[1]Availability [3]Availability: Platforms

Lineage

Predecessors

Claude Opus 5 · 24 July 2026

Successors

No known successor.

Based on

Not derived from another model.

Variants and derived

None recorded.

Siblings

None recorded.

All ancestors

Claude · 14 March 2023
Claude 2 · 11 July 2023
Claude 2.1 · 21 November 2023
Claude 3 Opus · 4 March 2024
Claude Opus 4 · 22 May 2025
Claude Opus 4.1 · 5 August 2025
Claude Opus 4.5 · 24 November 2025
Claude Opus 4.6 · 5 February 2026
Claude Opus 4.7 · 16 April 2026
Claude Opus 4.8 · 28 May 2026
Claude Opus 5 · 24 July 2026

All descendants

None.

Related AI Radar coverage

The Sequence Learning Loop - Issue 942: Learning About Opus 5.5, DeepSeek’s Training Grounds, and Claude’s DNA DiscoveryDeepSeek · TheSequence | Jesus Rodriguez · 30 September 2026
Claude Opus 5.5 comes to Microsoft Foundry for long-running coding and knowledge workMicrosoft AI · Azure · 22 September 2026

All model releases from Anthropic on AI Radar →

Organisation: Anthropic
Family: Claude Opus
Generation: 5.5
Timeline date: 22 September 2026
Released
Prominence: Standard release Editorial
Also known as: Opus 5.5, claude-opus-5-5
Record: Full record
Last reviewed: 1 October 2026

Sources

[1] Introducing Claude Opus 5.5

Announcement · Anthropic · published 22 September 2026

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://www.anthropic.com/claude-opus-5-5 Title from the HTML title. https://www.anthropic.com/news/claude-opus-5-5 redirects (307) here.
[2] Claude Platform release notes

Release notes · Anthropic

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://platform.claude.com/docs/en/release-notes/overview Living page; content as seen on 2026-10-01; earliest entry May 2024. The old address https://docs.anthropic.com/en/release-notes/api redirects here (301 to platform.claude.com/docs/en/release-notes/api, then 307).
[3] Claude Opus 5.5

Documentation · Anthropic

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://platform.claude.com/docs/en/models/opus-5-5/overview Per-model reference page in the Claude Platform docs (status, release date, model IDs, context window, input and output). Living page.
[4] Models overview

Documentation · Anthropic

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://platform.claude.com/docs/en/models/overview Living page that changes with each release; content as seen on 2026-10-01. Older addresses redirect here: https://docs.anthropic.com/en/docs/about-claude/models/overview (301) and https://platform.claude.com/docs/en/about-claude/models/overview (307).
[5] Model deprecations

Deprecation notice · Anthropic

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://platform.claude.com/docs/en/about-claude/model-deprecations Living page; content as seen on 2026-10-01. The old address https://docs.anthropic.com/en/docs/about-claude/model-deprecations redirects here (301, then 307 via platform.claude.com/docs/en/docs/about-claude/model-deprecations). The page says its dates apply to the Claude API, Claude Platform on AWS and Microsoft Foundry; Amazon Bedrock and Google Cloud set their own schedules.
[6] Claude Opus 5

Documentation · Anthropic

Provenance
Primary

Availability
Active

Last checked
8 October 2026

Original ↗ https://platform.claude.com/docs/en/models/opus-5/overview Per-model reference page in the Claude Platform docs (status, release date, model IDs, context window, input and output). Living page.