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Releases.
Anthropic

Anthropic, September 2026 new features

36 releases · 3 products · 4 GA · 1 Preview · 11 Beta · 1 Pricing

Aug 2026
DateRelease
Sep 23Claude Code 2.1.281unverified
Claude CodeUpdate
Sep 22Claude API beta lets tools be defined inside mid-conversation system messages
Claude PlatformBeta
Sep 22Claude Code 2.1.280
Claude CodeUpdate
Sep 22Claude Opus 5.5 breaking changes: thinking can't be disabled, forced tool_choice removed
Claude PlatformUpdate
Sep 22Claude Opus 5.5 launched, first model in the Claude 5.5 family
Claude appsGA
Sep 22Claude Opus 5.5 launches with a 1M token context window and 128k output
Claude PlatformGA
Sep 22Fast mode research preview available for Claude Opus 5.5 on the Claude API
Claude PlatformPreview
Sep 19Claude Code 2.1.278
Claude CodeUpdate
Sep 18Claude Code 2.1.276
Claude CodeUpdate
Sep 18Claude Code 2.1.277
Claude CodeUpdate
Sep 18Compliance API adds Claude in Chrome session transcripts in beta
Claude PlatformBeta
Sep 17Claude Code 2.1.274
Claude CodeUpdate
Sep 17Claude Code 2.1.275
Claude CodeUpdate
Sep 15Claude Code 2.1.272
Claude CodeUpdate
Sep 15Claude Code 2.1.273
Claude CodeUpdate
Sep 15Salesforce in Claude plugin (beta) with 37 pre-built sales skills
Claude appsBeta
Sep 14Claude API input_transformations adds thinking_mismatch_allowed entries in beta
Claude PlatformBeta
Sep 14Claude Code 2.1.271
Claude CodeUpdate
Sep 14Messages API adds on-demand conversation compaction in beta
Claude PlatformBeta
Sep 12Claude Code 2.1.270
Claude CodeUpdate
Sep 10Claude Managed Agents permission policies add an auto mode
Claude PlatformUpdate
Sep 10Smart reports (beta) on Claude Enterprise analyze team usage and costs
Claude appsBeta
Sep 10ant CLI 1.32.0 adds sessions connect for live Managed Agents sessions
Claude PlatformBeta
Sep 3Per-message effort changes beta expands to Claude on Google Cloud
Claude PlatformBeta
Sep 3ant CLI 1.30.0 adds ant apply to manage agents and resources as code
Claude PlatformUpdate
Sep 1Claude API adds turn-scoped system messages in beta
Claude PlatformBeta
Sep 1Claude API thinking.display adds an updates mode in beta
Claude PlatformBeta
Sep 1Claude Enterprise Admin, Analytics and Compliance API guides add anthropic-version
Claude PlatformUpdate
Sep 1Claude Fable 5.1 and Claude Mythos 5.1 launched
Claude appsGA
Sep 1Claude Fable 5.1 and Mythos 5.1 reject tool_choice any and tool
Claude PlatformUpdate
Sep 1Claude Fable 5.1 and Mythos 5.1 require 30-day data retention
Claude PlatformUpdate
Sep 1Claude Fable 5.1 launches alongside Claude Mythos 5.1 with 1M token context
Claude PlatformGA
Sep 1Claude Fable 5.1 output carries text watermarks and C2PA Content Credentials
Claude PlatformUpdate
Sep 1Claude Fable 5.1 thinking blocks only replay to the same or newer models
Claude PlatformUpdate
Sep 1Per-message effort changes enter beta on the Claude API
Claude PlatformBeta
Sep 1Prompt cache reads on Claude Fable 5.1 and Mythos 5.1 drop to $0.25 per MTok
Claude PlatformPricing

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