Claude 3.5 Sonnet (Anthropic) and Grok 4 (xAI) are both frontier AI models. Claude 3.5 Sonnet was published in June 2024 and Grok 4 in July 2025.
Grok 4 was trained on 5 x 10^26 FLOP, about 18.5x the compute of Claude 3.5 Sonnet at 2.7 x 10^25 FLOP. Training compute is the closest available proxy for how much was invested in a model, though it says nothing on its own about how well that compute was spent.
Grok 4 wins the single benchmark both were scored on. Benchmark counts are a crude scoreboard — the evaluations differ wildly in what they measure and in how saturated they are — so the per-benchmark table below matters more than the tally.
| Field | Claude 3.5 Sonnet | Grok 4 |
|---|---|---|
| Organization | Anthropic | xAI |
| Published | Jun 20, 2024 | Jul 9, 2025 |
| Training compute | 2.7 x 10^25 FLOP | 5 x 10^26 FLOP |
| Parameters | — | 3T |
| Chips used | — | 200,000 |
| Training cost (2023 USD) | $26M | $388M |
| Accessibility | API access | API access |
| Open weights | No | No |
| Country | United States | United States |
| Benchmark | Claude 3.5 Sonnet | Grok 4 |
|---|---|---|
| Epoch Capabilities Index(ECI Score) | 130 | 147 |
