Claude Opus 4.8 vs Gemini 3.1 Pro Preview

Quality coding model vs. very-long-context multimodal model.

MetricClaude Opus 4.8Gemini 3.1 Pro Preview
ProviderAnthropicGoogle Gemini
Input / 1M$5.00$2.00
Output / 1M$25.00$12.00
Cache read / 1M$0.50 (−90%)$0.20 (−90%)
Reuse-adj @55%$8.14$3.76
Context1M1M
Cache capture93%82%
Warm TTFT240ms (−68%)360ms (−56%)
Quality index9794

Teal marks the better value in each row. Reuse-adjusted assumes 55% prefix reuse and a 25% output share.

Pick Claude Opus 4.8 when

Coding and tool-heavy agents where explicit caching and capture predictability matter most.

Pick Gemini 3.1 Pro Preview when

Multimodal or document-scale work that needs the larger window and implicit caching convenience.

Verdict

Pick Claude Opus 4.8 for predictable coding economics; pick Gemini 3.1 Pro when context length and modalities dominate the decision.

Claude Opus 4.8 vs Gemini 3.1 Pro Preview, answered.

Is Claude Opus 4.8 or Gemini 3.1 Pro Preview cheaper?

At 55% prefix reuse, Claude Opus 4.8 blends to about $8.14 per 1M tokens and Gemini 3.1 Pro Preview to about $3.76. Gemini 3.1 Pro Preview is cheaper on that basis.

Which has the larger context window?

Gemini 3.1 Pro Preview has the larger window: 1M vs 1M tokens.

Which captures more reuse?

Claude Opus 4.8 shows higher measured cache capture (93% vs 82%) in the Zumik corpus.

Let an alias pick for you.

Route to whichever model wins under current policy automatically. Zumik resolves the alias to the best fit per request, so you never hard-code a loser.