Side-by-side comparison of pricing, 12 benchmarks, and generation speed.
| Metric | GPT-6 Astra (low) | Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) |
|---|---|---|
| Input ($/M tokens) | $10 | $10 |
| Output ($/M tokens) | $50 | $50 |
Verdict. GPT-6 Astra (low) and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) split the benchmark comparison evenly at 1–1. The tiebreaker here is price, speed, and what you actually run them on.
Pricing. Both models sit in the premium bracket for output-token pricing. At 1.0× the per-million-token cost, Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) is meaningfully cheaper if your traffic is output-heavy (long completions, document generation, agent loops). Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) makes more sense when output volume is low and absolute reasoning quality justifies the premium.
Strengths. GPT-6 Astra (low) is strongest on Coding Index (75.7), Intelligence Index (56.7). Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) leads on Coding Index (75.2), Intelligence Index (58.1).
Speed. Speed data is incomplete for this pair; benchmark and price should decide.
Provider. OpenAI and Anthropic sell to overlapping but distinct developer audiences: OpenAI tends to ship frontier reasoning models with premium positioning, while Anthropic often prices more aggressively. Your existing vendor relationships, billing, and SLA preferences may matter as much as the raw numbers above.
Workload cost. Workload scenarios (per million requests at 30M input + 15M output tokens): GPT-6 Astra (low) costs $1050.00 ($12600/year); Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) costs $1050.00 ($12600/year). At a smaller 5M-input/2M-output scale (single-developer tool or prototype): GPT-6 Astra (low) ≈ $150.00/run, Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) ≈ $150.00/run. At agent/realtime scale (200M input / 100M output per million requests): GPT-6 Astra (low) ≈ $7000/run, Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) ≈ $7000/run.
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
Both models have similar pricing. Check the detailed breakdown above for input vs output token costs.
It's a tie — both models win 1 benchmarks each across 12 evaluated categories. See the detailed benchmark chart above for per-category results.
Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) generates tokens faster at 59 tok/s vs — tok/s. However, Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) has lower time-to-first-token (6.58s vs —s).
Choose based on your priorities: both are similarly priced, both perform similarly on benchmarks, and Claude Fable 5.1 (Adaptive Reasoning, Low Effort, Default Fallback) for faster generation. For latency-sensitive apps, check the TTFT comparison above.