Claude Fable 5.1 and Claude Mythos 5.1 launch

GASep 1, 20263 weeks agoUnverifiedAdded Sep 28, 2026

Anthropic launched Claude Fable 5.1 and Claude Mythos 5.1, designed for coding and knowledge work.

Topics: LLMs, Coding agents

Anthropic's release notes

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Every Claude Platform release

Date	Release	Type
Sep 13 weeks ago	Claude Fable 5.1 launches alongside Claude Mythos 5.1 with 1M token context GA	GA
Sep 13 weeks ago	Prompt cache reads on Claude Fable 5.1 and Mythos 5.1 drop to $0.25 per MTok Pricing	Pricing
Sep 13 weeks ago	Claude Fable 5.1 and Mythos 5.1 reject tool_choice any and tool Update	Update
Sep 13 weeks ago	Claude Fable 5.1 thinking blocks only replay to the same or newer models Update	Update
Sep 13 weeks ago	Per-message effort changes enter beta on the Claude API Beta	Beta
Sep 13 weeks ago	Claude API adds turn-scoped system messages in beta Beta	Beta
Sep 13 weeks ago	Claude API thinking.display adds an updates mode in beta Beta	Beta
Sep 13 weeks ago	Claude Fable 5.1 output carries text watermarks and C2PA Content Credentials Update	Update

Also shipped on Sep 1, 2026

Anthropic in September 2026

Date	Company	Release	Product	Type
Sep 20263 weeks ago	Fivetran	Fivetran connection cron scheduling enters beta FivetranBeta	Fivetran	Beta
Sep 20263 weeks ago	Fivetran	Fivetran Connection Warnings REST API enters private preview FivetranPreview	Fivetran	Preview
Sep 13 weeks ago	Google Cloud	The Rust SDK for BigQuery is now in Preview Google CloudBigQueryPreview	BigQuery	Preview
Sep 13 weeks ago	Snowflake	Snowflake App Runtime (General availability) SnowflakeGA	Snowflake	GA
Sep 13 weeks ago	Databricks	Apache Arrow support for Zerobus Ingest is now generally available DatabricksLakeflowGA	Lakeflow	GA
Sep 13 weeks ago	Databricks	Genie One web search is in Beta DatabricksAI/BI and GenieBeta	AI/BI and Genie	Beta

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