Fable 5 is now available to Augment Code users. At ~2x the cost of Opus 4.7, Fable 5 is a premium option for long, multi-step engineering work. Try Fable 5 today in Cosmos, our unified agent platform, to fully experience the power of the most advanced model on the market.

Fable 5 brings a new level of capability to complex software engineering work. We've found it performs best for: - Code review where catching subtle issues matters - PR authoring and implementation support - Large-project planning and architecture reasoning - Long-running, multi-step technical tasks - High-stakes engineering work where quality matters more than cost

TL;DR: Fable 5 isn’t the right-sized model for every task, but when quality and depth matter (review, architecture, long-running changes), the lift is impressive. Here’s how it stacks up vs Opus 4.8 + GPT‑5.5

The bigger unlock is Fable 5 running in our unified agent platform, Cosmos. Pull context from your tools and run across the SDLC (triage → spec → implement → review → test → deploy). Instead of “one prompt, one answer,” you get background workflows with triggers + durable memory: and engineers step in only when judgment is needed.

With models like Fable 5, model routing is more important than ever. We’ll be adding Fable 5 to our model router, Prism, soon. Prism routes each turn to the best-fit model and is cache-aware, so teams can keep frontier-level quality while cutting cost. In our internal benchmarks, Prism delivered up to 30% lower cost per task at no difference in quality.