Side-by-side comparison of pricing, 12 benchmarks, and generation speed.
| Metric | Claude Opus 5 (Adaptive Reasoning, Max Effort) | Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) |
|---|---|---|
| Input ($/M tokens) | $5 | $10 |
| Output ($/M tokens) | $25 | $50 |
Verdict. Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) takes the aggregate benchmark matchup 2–0 across 2 categories. Real workloads usually care about a handful of specific tasks — see the per-benchmark table above.
Pricing. Both models sit in the premium bracket for output-token pricing. At 0.5× the per-million-token cost, Claude Opus 5 (Adaptive Reasoning, Max Effort) is meaningfully cheaper if your traffic is output-heavy (long completions, document generation, agent loops). Claude Opus 5 (Adaptive Reasoning, Max Effort) makes more sense when output volume is low and absolute reasoning quality justifies the premium.
Strengths. Claude Opus 5 (Adaptive Reasoning, Max Effort) is strongest on Coding Index (78.0), Intelligence Index (63.1). Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) leads on Coding Index (80.7), Intelligence Index (64.8).
Speed. Throughput is comparable — 59 tok/s vs 69 tok/s — so generation speed shouldn't drive your choice here. Look at the per-benchmark wins instead.
Provider. Both models come from the same vendor, so the choice comes down to which tier or generation fits your workload — not vendor lock-in.
Workload cost. Workload scenarios (per million requests at 30M input + 15M output tokens): Claude Opus 5 (Adaptive Reasoning, Max Effort) costs $525.00 ($6300/year); Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) costs $1050.00 ($12600/year). At a smaller 5M-input/2M-output scale (single-developer tool or prototype): Claude Opus 5 (Adaptive Reasoning, Max Effort) ≈ $75.00/run, Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) ≈ $150.00/run. At agent/realtime scale (200M input / 100M output per million requests): Claude Opus 5 (Adaptive Reasoning, Max Effort) ≈ $3500/run, Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) ≈ $7000/run. Claude Opus 5 (Adaptive Reasoning, Max Effort) becomes more attractive at higher volume — the absolute per-token pricing difference compounds when you ship at scale.
Recommendation. Both models have legitimate use cases — the right answer depends on whether you are optimizing for benchmark ceiling, latency, or unit cost. Start with the cheaper / faster model, evaluate against your specific task, and only switch if the upgrade shows a meaningful lift.
Head-to-head deltas
Data from Artificial Analysis API — 12 benchmarks
Claude Opus 5 (Adaptive Reasoning, Max Effort) is cheaper overall. Its blended price (3:1 input/output ratio) is $10.00/M tokens vs $20.00/M for Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback).
Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) wins 2 out of 12 benchmarks compared to 0 for Claude Opus 5 (Adaptive Reasoning, Max Effort). See the detailed benchmark chart above for per-category results.
Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) generates tokens faster at 69 tok/s vs 59 tok/s. Claude Opus 5 (Adaptive Reasoning, Max Effort) also has lower time-to-first-token (77.25s vs 111.68s).
Choose based on your priorities: Claude Opus 5 (Adaptive Reasoning, Max Effort) for lower cost, Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) for stronger benchmark performance, and Claude Fable 5.1 (Adaptive Reasoning, Xhigh Effort, Default Fallback) for faster generation. For latency-sensitive apps, check the TTFT comparison above.