Anthropic Models

Overview of Anthropic’s latest Claude models with positioning, capabilities, and practical guidance.

Latest: Claude Fable 5.1

Claude Fable 5.1 (Sep 2026) is Anthropic's most capable general-access model, with a 1M-token context window and adaptive thinking for coding and knowledge work. Claude Mythos 5.1 is the same weights with relaxed cyber/bio safeguards for vetted trusted-access partners.

Strengths

  • 1M-token context window
  • Adaptive thinking for hard problems
  • Multi-day autonomous agentic sessions

Best For

  • Ambitious coding projects
  • Document analysis and synthesis
  • Multi‑step workflows with tool calls

Model Lineup

Claude Fable 5.1

Latest, highest-capability tier for coding and knowledge work.

Claude Opus 5

Frontier-class model for complex agentic coding at roughly half the price of Fable-tier models.

Claude Sonnet 5

Mainstream frontier-at-scale model balancing intelligence, speed, and cost.

Claude Haiku 4.5

Fastest, most cost-efficient tier; well suited to high-volume sub-agent workloads.

Practical Guidance

  • Use structured prompts and function schemas for consistent tool calls.
  • Prefer citation storage when summarizing documents for auditability.
  • Set sensible token caps and retry policies for long‑context tasks.