Claude Opus 5 vs Claude Fable 5: Which Model Should You Use?
A practical comparison of Claude Opus 5 and Claude Fable 5: benchmarks, pricing, agentic capabilities, and a decision framework for choosing between them.
TL;DR
Claude Opus 5 matches or beats Claude Fable 5 on most published benchmarks at half the input price ($5/M vs $10/M). Fable 5 keeps the edge for long-horizon autonomous agents that run for days and for the deepest research workloads. For everything that finishes within a working session — coding, analysis, computer use, knowledge work — Opus 5 is now the better-value choice.
The Numbers
On the benchmarks Anthropic published at launch, the gap is smaller than the price difference suggests:
- SWE-bench Pro: Fable 5 leads narrowly, 80.0% vs 79.2%
- Frontier-Bench v0.1: Opus 5 leads, 43.3% vs 33.7%
- GDPval-AA v2 (knowledge work, Elo): Opus 5 leads, 1,861 vs 1,747
- CursorBench 3.2: Opus 5 within 0.5% of Fable 5 at half the cost
- OSWorld 2.0: Opus 5 surpasses Fable 5 at roughly one-third the cost per task
The headline: on agentic coding and knowledge work, Opus 5 is not a compromise — it actually leads several of these evaluations outright.
Where Fable 5 Still Wins
Anthropic is explicit about the remaining gap. Fable 5 is the recommendation for long-horizon agents — workloads that run autonomously for days, accumulate massive state, and need the most reliable self-correction over thousands of steps. Fable 5 also carries the flagship position for the hardest open-ended research problems.
Fable 5 additionally ships with stricter dual-use safeguards. Opus 5's cybersecurity safeguards are about 85% less restrictive than Fable 5's because the model does not advance risky frontier capabilities — which in practice means fewer refusals on legitimate security work.
Pricing Comparison
- Opus 5: $5/M input, $25/M output; fast mode $10/$50
- Fable 5: $10/M input — double Opus 5 on input
For a team spending $10,000/month on Fable 5 for session-scale coding tasks, switching to Opus 5 cuts that roughly in half with little or no quality loss on most tasks.
Decision Framework
Choose Claude Opus 5 when:- Tasks complete within a session (coding, reviews, analysis, document work)
- You run high volumes of agentic coding or computer-use workloads
- Cost per task matters and you want frontier-class output
- You do legitimate security research and want fewer safeguard frictions
- Agents run autonomously for days with long-horizon planning
- You need the absolute maximum on the hardest research problems
- Budget is not the binding constraint
Conclusion
The safe default has changed. Before July 2026, Fable 5 was the obvious pick whenever quality mattered; now Opus 5 delivers Fable-class results on most real work at half the price. Start new projects on Opus 5 and escalate to Fable 5 only where long-horizon autonomy demonstrably needs it.