Updates: #Model.

[NEW] Claude Sonnet 5.5 · Anthropic introduced Claude Sonnet 5.5 on September 28, 2026, the second model in the Claude 5.5 family. It's a clear upgrade over Claude Sonnet 5, runs 30%+ faster, and costs up to 30% less for most work. It's priced the same as Sonnet 5 at $2 per million input tokens, $10 per million output tokens, and $0.20 per million tokens for cache reads, and the model ID is claude-sonnet-5-5. It scores 70.6% on Terminal-Bench 4.0, compared to Sonnet 5's 10.3%, and two points below Opus 5.5 on GDPval-AA.

[NEW] Claude Opus 5.5 · Anthropic introduced Claude Opus 5.5 on September 22, 2026, the first model in the new Claude 5.5 family. It performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5. Input and output tokens are $4 and $20 per million, 20% less than Opus 5, and cache reads are $0.20 per million tokens, 60% less. The model ID is claude-opus-5-5, and it generates output more than 30% faster than Opus 5. Five-hour usage limits are increasing on Pro, Max, Team, and seat-based Enterprise plans.

[NEW] Claude Fable 5.1 and Claude Mythos 5.1 · Anthropic introduced Claude Fable 5.1 and Claude Mythos 5.1 on September 1, 2026, describing them as the world's most advanced models for coding and knowledge work. Input and output pricing is unchanged from Claude Fable 5 at $10 / $50 per MTok, but cache reads drop to $0.25 per MTok, making Fable 5.1 an estimated 25% less expensive than Fable 5 for typical workloads. The model ID is claude-fable-5-1, with a 1M token context window and 128k max output tokens. Three changes are breaking for existing Fable 5 callers, starting with forced tool use. Mythos 5.1 offers the same capabilities to Project Glasswing participants only.

[NEW] Claude Opus 5 · Anthropic introduced Claude Opus 5 on July 24, 2026, for complex agentic coding and enterprise work. It is priced at $5 per million input tokens and $25 per million output tokens, the same as Opus 4.8, with the model ID claude-opus-5, a 1M token context window, and 128k max output tokens. Adaptive thinking is now on by default, effort runs up to max, and two betas ship alongside it: mid-conversation tool changes and automatic fallbacks. It is the new default model on Claude Max and the strongest model on Claude Pro.

[NEW] Introducing Claude Sonnet 5 · Anthropic released Claude Sonnet 5 on June 30, 2026, an agentic model that approaches Opus 4.8 performance at lower prices. It can make plans, use tools like browsers and terminals, and run autonomously, with benchmark gains over Sonnet 4.6 across coding, reasoning, tool use, and knowledge work. The model ID is claude-sonnet-5; it is the default model for Free and Pro plans and is available in Claude Code, the Claude Platform, and the Claude API.

[NEW] Claude Fable 5 and Claude Mythos 5 · Anthropic released Claude Fable 5 and Claude Mythos 5 on June 9, 2026. Fable 5 is a Mythos-class model made safe for general use — state-of-the-art on nearly all tested benchmarks, with the `claude-fable-5` model ID. Mythos 5 is identical with cybersecurity safeguards lifted, available in limited release through Project Glasswing. Both support a 1M token context window and up to 128k output tokens by default, priced at $10/$50 per MTok. When a safety classifier declines a request, the Messages API returns stop_reason: "refusal" as an HTTP 200, and the fallbacks parameter (beta) or SDK middleware retries on another Claude model.

[NEW] Claude Opus 4.8 · Claude Opus 4.8 builds on Claude Opus 4.7 with improvements across benchmarks and is a more effective collaborator, available today for the same price. It targets long-horizon agentic coding with better long-context handling and compaction recovery, more reliable effort calibration, and better tool triggering. The model ID is claude-opus-4-8; it supports the 1M token context window by default on the Claude API, Amazon Bedrock, and Vertex AI, with 128k max output tokens.

[NEW] Claude Opus 4.7 · A new Opus model with significant gains in coding, high-resolution vision, and instruction following. Claude Code adds /ultrareview and the xhigh effort level.