Claude Opus 5.5 launch

GASep 22, 20266 days agoUnverifiedAdded Sep 28, 2026

Claude Opus 5.5 is the first model in the Claude 5.5 family. It performs at the level of Claude Fable 5.1 while costing 40% less than Opus 5.

Topics: LLMs, Performance

Anthropic's release notes

More Claude Platform releases

Every Claude Platform release

Date	Release	Type
Sep 226 days ago	Claude Opus 5.5 launches with a 1M token context window and 128k output GA	GA
Sep 226 days ago	Claude Opus 5.5 breaking changes: thinking can't be disabled, forced tool_choice removed Update	Update
Sep 226 days ago	Fast mode research preview available for Claude Opus 5.5 on the Claude API Preview	Preview
Sep 226 days ago	Claude API beta lets tools be defined inside mid-conversation system messages Beta	Beta
Sep 235 days ago	Cache diagnostics is out of beta on the Claude API and no longer requires the cache-diagnosis-2026-04-07 beta unverified Beta	Beta
Sep 244 days ago	We're expanding which refusals are billed to include refusals that arrive before any output when unverified Update	Update
Sep 244 days ago	We're resuming billing for refusals that arrive before any output when stop_details.category is "bio" unverified Pricing	Pricing
Sep 244 days ago	The Compliance API local session endpoints are out of beta for Claude for Microsoft 365 sessions in Excel unverified Beta	Beta

Also shipped on Sep 22, 2026

Anthropic in September 2026

Date	Company	Release	Product	Type
Sep 226 days ago	Databricks	Shopify connector (Beta) DatabricksLakeflowBeta	Lakeflow	Beta
Sep 226 days ago	Databricks	Lakebase backup schedule API (Beta) DatabricksLakebaseBeta	Lakebase	Beta
Sep 226 days ago	AWS	OpenAI GPT-6 Sol and GPT-6 Luna are now generally available on Amazon Bedrock AWSAmazon BedrockGA	Amazon Bedrock	GA
Sep 226 days ago	Vercel	Drives for Vercel Sandbox are now in public beta VercelAI SDK and AI GatewayBeta	AI SDK and AI Gateway	Beta
Sep 226 days ago	GitHub	Deprecation notice: All-platform CodeQL bundle GitHubGitHub Advanced SecurityDeprecation	GitHub Advanced Security	Deprecation
Sep 226 days ago	GitHub	Refreshed repository pull requests page generally available GitHubGitHub platformGA	GitHub platform	GA

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