Claude models explained: Fable 5.1, Opus 5.5, Sonnet 5.5 and Haiku 5.5

Updated November 2, 2026. Researched and drafted with AI help; every figure is checked against the linked source.

Anthropic ships Claude in four sizes that are available to everyone, plus a restricted tier for vetted organizations. Here is what each one is for and what it costs, as of October 2026.

The lineup at a glance

Model	Best for	API input / output per 1M tokens	Context window	Released
Claude Fable 5.1	The hardest reasoning and long agentic work	$10 / $50	1M tokens	Sep 1, 2026
Claude Opus 5.5	Most workloads, especially coding and agents	$4 / $20	1M tokens	Sep 22, 2026
Claude Sonnet 5.5	Fast everyday work, bug fixing, documents	$2 / $10	1M tokens	Sep 28, 2026
Claude Haiku 5.5	High-volume, cheap, fast tasks and subagents	$0.10 / $0.50 (prompts up to 100K tokens)	1M tokens	Oct 7, 2026

All four offer a 50% discount through the Batch API, and cached input is billed far below the normal input price.

Claude Opus 5.5: the default pick

Opus 5.5 is the newest model and the one Anthropic recommends “for most workloads.” Anthropic says it performs at the level of Fable 5.1 on most work and costs 40% less to run than Opus 5. At $4 input and $20 output per million tokens it is also cheaper than the previous Opus 5 ($5 / $25).

It’s a strong choice for coding agents and long knowledge-work tasks, where its low cache-read price ($0.20 per million tokens) matters because the same context gets re-read many times.

Claude Fable 5.1: the top of the range

Fable 5.1 is Anthropic’s most capable generally available model, aimed at “demanding reasoning and long-horizon agentic work.” It costs $10 / $50 per million tokens, the most expensive in the lineup.

Two details matter for your bill. Like all Claude 4.7-and-later models, Fable 5.1 uses a newer tokenizer that produces about 30% more tokens for the same text than older Claude models, so a prompt costs more than older per-token comparisons suggest. On the other hand, cache reads on Fable 5.1 cost just $0.25 per million tokens, which Anthropic says makes it up to 45% cheaper than Fable 5 for agentic work.

Claude Sonnet 5.5: the everyday model

Sonnet 5.5, released on September 28, 2026, replaces Sonnet 5 at the same $2 / $10 price, with cache reads at $0.20 per million tokens (cut to $0.10 on October 7, 2026). Anthropic calls it “a faster, lower-cost complement to Claude Opus 5.5” and says it outputs over 30% faster than Sonnet 5 and costs up to 30% less per task. Its own benchmark numbers show the biggest jump on agentic coding: 70.6% on Terminal-Bench 4.0, against 10.3% for Sonnet 5. For a head-to-head with OpenAI’s model at the same price, see Claude Sonnet 5.5 vs GPT-6.1 Sol.

The previous model, Sonnet 5, was the default model on claude.ai’s Free and Pro plans. It launched at an introductory $2 / $10 price, and Anthropic later made that price permanent. For most chat and writing tasks it is the best value in the lineup.

Claude Haiku 5.5: cheap and fast

Haiku 5.5, released on October 7, 2026, is the smallest model and the one Anthropic calls “the cheapest, fastest, and most capable small model we’ve ever released.” It costs $0.10 input and $0.50 output per million tokens for prompts up to 100,000 tokens, and $0.50 / $2.50 above that. Cache reads cost $0.01 (or $0.05 above 100K). It has a 1M-token context window and up to 128K output tokens. Use it for classification, extraction, summarization, routing, and as a subagent under Opus 5.5 or Sonnet 5.5. Our Haiku 5.5 guide covers it in detail.

The previous small model, Haiku 4.5, costs $1 / $5 with a 200K-token context window. Anthropic says Haiku 5.5 is about 75% cheaper to run on average.

Fable vs Mythos, and Project Glasswing

Fable and Mythos are the same underlying model with different safeguards. Fable has stronger safeguards for general use and is what you can use on claude.ai and the API. Mythos has fewer safeguards and is limited to vetted organizations: Mythos 5.1 is available only through Anthropic’s Cyber Verification and Life Sciences Verification programs, currently for US organizations.

Separately, Claude Mythos Preview, which is not publicly available, was given to partners in Project Glasswing, a defensive cybersecurity effort Anthropic launched on April 7, 2026 with companies including AWS, Apple, Google, Microsoft and NVIDIA. Glasswing partners can now upgrade to Mythos 5.

The June 2026 suspension

On June 12, 2026, after a US government export-control directive covering foreign nationals, Anthropic suspended access to Fable 5 and Mythos 5 for all customers. The controls were lifted on June 30, and Fable 5 became available globally again on July 1. Other Claude models were not affected.

Which Claude plan do you need?

On claude.ai, the Free plan includes Sonnet and Haiku. Pro costs $20 a month ($17 a month billed yearly) and adds Opus and Fable. Max ($100 a month) and Ultra ($200 a month, formerly Max 20x) raise usage limits, and both include monthly Claude API credits: $100 on Max and $200 on Ultra. See Claude Max vs Ultra for what changed and what the credits buy. See every plan side by side on our plans page.

Quick recommendations

Building a coding agent? Start with Opus 5.5.
Hardest problems, budget no object? Fable 5.1.
A chatbot or writing tool on a budget? Sonnet 5.5.
Millions of small tasks? Haiku 5.5.

Estimate your own bill in the cost calculator, and see how people rate each model today on the dumb meter.