Yesterday in AI: 09 June 2026 — Claude Fable 5 Breaks 80% on SWE-Bench

Anthropic made its Mythos-class model publicly available as Claude Fable 5, scoring 80.3% on SWE-Bench Pro at $10/$50 per million tokens; Claude Code shipped safe mode and a /cd command; and Open-Notebook crossed 28K GitHub stars.

By OMC Editorial on 2026-06-10

TL;DR — Anthropic released Claude Fable 5, its first Mythos-class model at general availability, scoring 80.3% on SWE-Bench Pro at half the Mythos Preview price; Claude Code 2.1.169 shipped safe mode, a /cd command, and a disableBundledSkills enterprise setting; and open-source NotebookLM alternative Open-Notebook crossed 28,000 GitHub stars after gaining 3,891 in seven days. --- 1️⃣ Claude Fable 5: Mythos-Class AI Goes Public at $10/$50 per MTok - What: Anthropic released Claude Fable 5 on June 9, making its highest-capability model tier generally available for the first time, alongside a limited-access Claude Mythos 5 for vetted cyber defenders and infrastructure providers. - Why it matters: At 80.3% on SWE-Bench Pro — versus 69.2% for Opus 4.8, 58.6% for GPT-5.5, and 54.2% for Gemini 3.1 Pro — Fable 5 is now the clear leader for agentic coding, priced at $10/$50 per million input/output tokens with a 90% caching discount. - Key number: 80.3% SWE-Bench Pro — a 21.7-point lead over the nearest rival. Claude Fable 5 is the GA release of Anthropic's Mythos model tier, previously gated to a small early-access cohort. The model ships with a novel set of safety classifiers that silently reroute queries touching cybersecurity, biology, chemistry, or model distillation to a less capable fallback — the first production model where a user's request may be answered by a different model than the one they selected. On long-horizon agentic work, Anthropic benchmarked the model using the deck-building game Slay the Spire with persistent file-based memory. Fable 5 improved three times faster than Opus 4.8 across game sessions and reached the final act three times as often. The model launched simultaneously on the Claude API, AWS Bedrock, and as a GA option inside GitHub Copilot. 📎 CNBChttps://www.cnbc.com/2026/06/09/anthropic-mythos-claude-fable-5.html · VentureBeathttps://venturebeat.com/technology/anthropic-brings-mythos-to-the-masses-with-claude-fable-5-its-most-powerf