Tutorials, deep dives and product notes — built for developers.
Anthropic's new Mythos-class Fable 5 (80.3% SWE-bench Pro, $50/1M) vs the outgoing flagship Opus 4.8 (69.2%, $25/1M). Fable 5 dominates every benchmark — but costs 2× more, hallucinates more, and sometimes falls back to Opus 4.8 anyway. Full 30-benchmark comparison.
The complete Claude Fable 5 review. Mythos-class for everyone. 80.3% Pro, 88.0% Terminal-Bench, 93.9% Verified. Stripe's 50M-line migration in a day. Karpathy: "major-version-bump-deserving." Simon Willison: "a beast." Safety classifiers, $10/$50 pricing, and why this is the biggest step toward AGI yet.
Claude Fable 5 ($50/1M) vs GPT-5.5 ($30/1M). Fable 5 leads all 8 coding benchmarks (+11.8 avg). GPT-5.5 counters with lower price and Batch/Flex at $15. 5× better Pro value from Fable 5. The definitive head-to-head comparison.
Claude Fable 5 ($50/1M) vs GPT-5.5 Pro ($180/1M). Fable 5 leads all 8 coding benchmarks by +11.8 pts avg. GPT-5.5 Pro fights back on BrowseComp (90.1%) and FrontierMath (39.6%) via parallel compute — but has no published Pro coding scores. Updated with separate GPT-5.5 Pro benchmarks.
SWE-bench Pro: Anthropic-reported Opus 5.5 leads at 89.9%; newly tracked vendor results include Ornith-1.5-397B (65.1%) and Qwen3.8-Omni-Flash (63.3%), kept distinct from Scale standardized results. Updated October 9, 2026.