Claude Fable 5 vs GPT-5.3 Codex
Claude Fable 5 (Anthropic) and GPT-5.3 Codex (OpenAI) compared on benchmarks, pricing, context window, and use-case rankings.
- Claude Fable 5 leads on overall intelligence (ECI 161 vs 156).
- GPT-5.3 Codex is cheaper on input tokens — $1.75 vs $10.00 per 1M.
- Claude Fable 5 has a larger context window (1M vs 400K tokens).
- Claude Fable 5 ranks higher for coding (99th vs 67th percentile).
| Attribute | Claude Fable 5 | GPT-5.3 Codex |
|---|---|---|
| Scores | ||
| Intelligence (ECI) | 161 | 156 |
| Coding | 99 | 67 |
| Math | 95 | — |
| Reasoning & Knowledge | 96 | 87 |
| Agentic & Tools | 98 | 67 |
| Specifications | ||
| Developer | Anthropic | OpenAI |
| Family | Claude | GPT |
| Released | Jun 9, 2026 | Feb 5, 2026 |
| Parameters | — | — |
| Availability | API access | API access |
| Context window | 1M | 400K |
| Price — $/M input | $10.00 | $1.75 |
| Price — $/M output | $50.00 | $14.00 |
| Inputs | text, image, file | text, image, file |
| Outputs | text | text |
| Benchmarks | ||
| AIME 2024/2025 | 100% | — |
| APEX | 45% | 32% |
| GPQA Diamond | 93% | 92% |
| Humanity's Last Exam | 53% | 40% |
| SciCode | 60% | 53% |
| SimpleBench | 82% | — |
| SimpleQA Verified | 68% | — |
| WebDev Arena | 1654 | 1407 |
| WeirdML | 92% | 79% |
| τ²-bench | 99% | 86% |
| METR task horizon | — | 5.8 h |
| SWE-bench Verified | — | 75% |
| Terminal-Bench | — | 78% |
Use-case scores are 0–100 percentile composites across each area’s benchmarks, ranked against every model from the past year. Highlighted cells lead each row. Open a model for the full picture.
Frequently asked questions
Is Claude Fable 5 better than GPT-5.3 Codex?
On Epoch AI's Capabilities Index, Claude Fable 5 scores higher (161) than GPT-5.3 Codex (156). The right pick depends on your task — compare their coding, math, and reasoning scores in the table above.
Which is cheaper, Claude Fable 5 or GPT-5.3 Codex?
GPT-5.3 Codex is cheaper on input tokens at $1.75 per million, versus $10.00 (representative OpenRouter pricing).
Which has a larger context window, Claude Fable 5 or GPT-5.3 Codex?
Claude Fable 5 supports up to 1M tokens, compared with 400K for the other.
Which is better for coding, Claude Fable 5 or GPT-5.3 Codex?
Across coding benchmarks like SWE-bench Verified and Terminal-Bench, Claude Fable 5 ranks higher — 99th vs 67th percentile among the models tracked on Model Beat.
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Benchmarks & model data from Epoch AI (CC BY); pricing & specs from OpenRouter. ECI = Epoch Capabilities Index.