Claude Fable 5 Agentic Coding Pipeline: Build Long-Horizon Tasks (2026)
A Claude Fable 5 agentic coding pipeline turns the model’s 80.3% SWE-Bench Pro score and 1M-token context window into repeatable, production-grade engineering throughput — but only if you design for long-horizon failure modes. Fable 5 is Anthropic’s most capable widely released model for demanding reasoning and long-running autonomous work, priced at $10/M input and $50/M output tokens. Unlike a chat interface where you steer every turn, a pipeline decomposes work into intake, context packing, planning, execution with checkpoints, quality gates, and rollback paths. Stripe reportedly used Fable 5 to migrate a 50-million-line Ruby codebase in one day — work that would have taken two months manually. This guide walks through each stage of that pipeline so you can build your own without learning the hard way. ...