Claude Haiku 5.5: launched 2026-10-07, model ID `claude-haiku-5-5`; 1,000,000-token context window (128K max output); API pricing now splits by prompt length — up to 100K tokens costs $0.10 input / $0.50 output, over 100K costs $0.50 input / $2.50 output (prior Haiku 4.5 had one flat rate of $1.00/$5.00), averaging about 75% cheaper; OSWorld 2.1 (computer use) jumps from Haiku 4.5's 15.7% to 72.4%, and Terminal-Bench 4.0 goes from 0.0% to 39.2%, already ahead of Anthropic's own GPT-6 Luna comparison score of 16.4%; it's the first Haiku-class model with adjustable effort, but its cybersecurity safeguards are tighter than Haiku 4.5's, blocking penetration-testing-style operations
Claude Opus 5.5 shipped 2026-09-22, model ID `claude-opus-5-5`; 1,000,000-token context window (128K output cap); API pricing is $4.00 input / $20.00 output per 1M tokens (down from Opus 5's $5/$25), with cache reads cut 60% to $0.20; Terminal-Bench 4.0 jumps from Opus 5's 52.3% to 66.4%, and GDPval-AA v2.1 leads at 1846 Elo versus Fable 5.1's 1735 and GPT-6 Astra's 1542; Anthropic's own numbers show it still trailing GPT-6 Astra on AutomationBench and Terminal-Bench-Science; because its biology and cybersecurity capabilities now match Claude Mythos 5.1, it ships with Fable-5.1-level safeguards, and on the API side thinking mode can no longer be turned off while forced tool use now returns an error instead of failing silently
Claude Fable 5.1 (API ID: claude-fable-5-1): released by Anthropic on 2026-09-01, 1,000,000-token context window, 128,000 max output tokens, input $10.00 / output $50.00 per 1M tokens (cache reads cut to $0.25, down 75%), closed-source; 52.6% on Terminal-Bench-Science 0.1 self-reported (up from 24.7%), 66 on the neutral Artificial Analysis Intelligence Index (up from 62, ahead of GPT-6 Astra's 61); launched alongside the restricted Claude Mythos 5.1, available only to vetted cybersecurity and life-sciences organizations
Claude is Anthropic's closed-source LLM family, known for Constitutional AI training, agent capabilities, and coding performance. In July 2026, Opus 5 scored 96% on SWE-bench Verified to claim the coding crown, while Fable 5 led general capability at 83% on LiveBench. Four tiers (Fable / Opus / Sonnet / Haiku) span $1–$10, making this the only family in the series with zero open weights.