Best AI Reasoning Models for GitHub - Page 3

Claude Fable 5.5 is an anticipated but currently unannounced model in Anthropic's Claude family, and Anthropic has not confirmed that a model with this name will be released. As of September 30, 2026, Claude Fable 5.1 remains the latest officially documented Fable model. Fable represents Anthropic's highest-end model tier for demanding reasoning and long-horizon agentic work, while the newer Opus 5.5 and Sonnet 5.5 occupy lower-cost positions in the Claude lineup. Anthropic's current documentation gives Fable 5.1 a 1-million-token context window and maximum output length of 128,000 tokens. It supports text and image inputs with text output and uses adaptive thinking that remains active throughout model operation. Fable 5.1 defaults to high reasoning effort and is listed as having a June 2026 reliable knowledge cutoff and training-data cutoff. API pricing is $10 per million input tokens and $50 per million output tokens, while prompt-cache reads cost $0.25 per million tokens and Batch API processing receives a 50% input and output discount. Anthropic's official documentation currently provides model identifiers for Fable 5.1 across the Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, and Claude Platform on AWS. No equivalent model identifier, specifications, benchmark results, pricing, availability information, or release schedule has been published for Claude Fable 5.5.

OpenAI Bel is an unconfirmed artificial intelligence model reportedly associated with OpenAI's research into large-scale foundation models. The name has appeared in unofficial discussions describing a possible new generation of pretrained AI systems. Reports suggest that Bel may represent a successor to an earlier internal training effort referred to as Doug. Some accounts describe the project as a potential foundation for future models related to the Astra family and later GPT generations. Unverified claims place its parameter count above 10 trillion, although OpenAI has not disclosed any supporting architectural information. The model's training methodology, supported modalities, context window, and inference capabilities remain unknown. No official benchmark evaluations have established its performance in reasoning, coding, mathematics, or other AI tasks. OpenAI has not announced public access, API availability, pricing, or a release schedule for a model named Bel. The available information therefore characterizes Bel as a rumored research project rather than an established commercial AI product.