Claude Fable Latest (Claude Fable 5.1)

ComputingForGeeks (September 3, 2026) provides a third-party technical review of Claude Fable 5.1, reporting that Anthropic released it on September 1, 2026 at the same $10/$50 per million token price as Fable 5 while cutting cache reads 75% (from $1.00 to $0.25 per 1M tokens), loosening safeguards that were refusing b The review highlights three breaking API changes that will affect existing Fable 5 code: forced tool use is disabled in Fable 5.1, thinking blocks cannot be shared with older Claude models, and editing prior conversation turns invalidates reasoning history. It notes Anthropic frames the cache savings as roughly 25% off

explainx.ai's September 2, 2026 analysis unpacks Anthropic's September 1-2 announcement, confirming that Claude Fable 5.1 (general availability, API model ID claude-fable-5-1) and Claude Mythos 5.1 (trusted access only, claude-mythos-5-1) are the same model with different safeguard levels. The post preserves concrete s The piece details pricing: $10/$50 per MTok input/output unchanged, with cache reads cut 75% from $1.00 to $0.25/MTok, yielding a net 25% cheaper typical workload and up to 45% cheaper for highly agentic work per Anthropic. It also documents a 1M-token context window (default and max) with 128K max output, a new Enterp

Anthropic released Claude Fable 5.1 alongside access-gated Claude Mythos 5.1 on September 1, 2026, positioning Fable 5.1 as generally available across Claude apps, Claude Code, Claude Enterprise, the API, and Amazon Bedrock, Google Cloud, and Microsoft Foundry. Both variants share the same underlying weights and specif Fable 5.1 more than doubles its predecessor's score on the agentic Terminal-Bench-Science 0.1 benchmark, reporting 52.6% versus 24.7% for Fable 5, 29.0% for Claude Opus 5, and 22.4% for GPT-5.6 Sol (standard error 3.5–4.5 points). On Terminal-Bench 4.0, Fable 5.1 scored 55.8% against 42.0% for Fable 5, 52.3% for Opus 5

The BuildFast editorial review (September 1, 2026) confirms Claude Fable 5.1 launched September 1, 2026 as Anthropic's latest model for demanding reasoning and long-horizon agentic work, with a 1M-token context window, 128K maximum output, adaptive thinking, and a default reasoning effort of high. It reports API pricin The review notes that Fable 5.1 remains expensive on uncached tokens and slower than Opus 5, and that Anthropic itself recommends starting with Opus 5 for most workloads, moving to Fable 5.1 only when cheaper or faster models still fail on the hardest tasks. It positions Fable 5.1 as a premium-tier choice for long-runn

VentureBeat's September 1, 2026 report covers the joint launch of Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (restricted-access for vetted cybersecurity and life-sciences organizations), noting that both names refer to the same underlying model. It details that the release simultaneously cuts cache-re The article cites specific benchmark numbers: Terminal-Bench-Science 0.1 at 52.6% for Fable 5.1 vs 24.7% for Fable 5, 29.0% for Opus 5, and 22.4% for GPT-5.6; Terminal-Bench 4.0 at 55.8% for Fable 5.1 vs 42.0% for Fable 5 and 52.3% for Opus 5; with Mythos 5.1 reaching 60.9% on Terminal-Bench 4.0 under its modified safe

SoftReviewed (September 1, 2026) covers the simultaneous launch of Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (restricted under Project Glasswing for vetted cybersecurity and biology research), noting both share an identical core architecture. Fable 5.1 is available immediately on the Claude API, Amaz The piece documents three concrete breaking developer changes when migrating from Fable 5: forced tool use is disabled, thinking blocks cannot be shared with older models, and editing prior conversation turns invalidates reasoning history. It reiterates the 75% cache price cut (from $1.00 to $0.25 per 1M tokens) and An

Artificial Analysis published independent third-party evaluation of Claude Fable 5.1 on September 1, 2026, reporting that at max effort the model scores 66 on the Artificial Analysis Intelligence Index — the highest score they have measured, ahead of Claude Opus 5 (63), Claude Fable 5 (62), GPT-5.6 Sol (61) and Grok 4. The same Artificial Analysis analysis details Fable 5.1's economics: cache reads are cut to $0.25 per 1M tokens (from $1), while standard input/output pricing stays at $10/$50 per 1M tokens. Despite the cache cut, Fable 5.1 (max) costs $3.76 per Intelligence Index task, about 20% more than Fable 5 (max), because it con

Amazon's official press release, updated September 1, 2026 (originally June 9, 2026), confirms Claude Fable 5.1 is available on Amazon Bedrock and Claude Platform on AWS and describes it as Anthropic's "new frontier model" delivering "top-tier intelligence for coding, scientific research, and enterprise workflows." It The post outlines four named capability gains: stronger reasoning on hard math, science, and multi-step benchmarks; agentic coding across multi-hour sessions; autonomous operation spanning many applications with planning, failure recovery, and progress updates; and end-to-end knowledge work including improved Excel and