Anthropic launched Claude Fable 5, a Mythos-class model claiming state-of-the-art performance across software engineering, scientific research, and knowledge work. It was quickly taken down by the U.S. government after a jailbreak was reported, though Anthropic asserts it is now available again, with Fable 5 showing exceptional capabilities and a more nuanced, thoughtful reasoning style compared to prior models.
Claude Fable 5 and Mythos 5: Capabilities
P4IR Framework Improves LLM-Based Code Compliance Accuracy
P4IR, a two-stage framework, uses supervised fine-tuning and Group Relative Policy Optimization to enhance large language model-based automated code compliance systems. It reduces tree edit and token-level Levenshtein distances by up to 23.8% and 38.6% respectively, outperforming leading LLMs like Claude Opus, GPT-5.2, and GLM-4.7 in zero-shot settings with few-shot prompting, and reduces false positives by a statistically significant margin.
LLM-as-Interface, ML-as-Predictor for Pediatric Appendicitis
ClaMPAPP, a hybrid system, uses an LLM to extract structured clinical features from free-text notes and passes them to an XGBoost classifier for diagnosis. It outperformed end-to-end LLMs in both internal and external validation, with better stability and fewer missed appendicitis cases, demonstrating superior diagnostic performance and safety in pediatric triage.
ALeRCE Launches Text-to-SQL System with LLMs
The ALeRCE astronomical database introduces a text-to-SQL system using large language models, enabling natural language queries to generate executable SQL. The system, evaluated on 110 NL/SQL pairs, uses a step-by-step framework that outperforms direct-inference baselines, with Claude Opus 4.6 achieving high precision on simple queries and among the best overall performance across evaluated models.
Anthropic releases Claude Opus 4 and Sonnet 4 with hybrid reasoning
Anthropic has released two new large language models, Claude Opus 4 and Claude Sonnet 4, which introduce "hybrid reasoning" capabilities to merge quick responses with extended step-by-step thinking. These models succeed the Claude 3.x generation and retain a 200,000-token context window while offering improved safety and agentic abilities.
Claude Code v2.1.280 adds Claude Opus 5.5 and fixes numerous bugs
Claude Code version 2.1.280 introduces Claude Opus 5.5 as the new default Opus model, featuring a 1M context window and updated pricing. The update also adds mouse wheel support for scrolling lists in fullscreen mode and allows configuration of MCP tool description length limits.