Head-to-head
Claude Opus 4.8 vs GPT-5.5
Compare Claude Opus 4.8 and GPT-5.5 on the metrics that decide an agent workload.
| Metric | Claude Opus 4.8 | GPT-5.5 |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Input / 1M | $5.00 | $5.00 |
| Output / 1M | $25.00 | $30.00 |
| Cache read / 1M | $0.50 (−90%) | $0.50 (−90%) |
| Reuse-adj @55% | $8.14 | $9.39 |
| Context | 1M | 1.1M |
| Cache capture | 94% | 88% |
| Warm TTFT | 240ms (−68%) | 240ms (−67%) |
| Quality index | 99 | 99 |
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 it is cheaper once prefix reuse is priced in, it captures more of the available reuse.
Pick GPT-5.5 when it carries the larger 1.1M context window.
Claude Opus 4.8 wins on both reuse-adjusted cost and quality here, so it is the default pick. Reach for GPT-5.5 only when a specific constraint (modality, latency floor, or licensing) forces it.
Frequently asked
Claude Opus 4.8 vs GPT-5.5, answered.
Is Claude Opus 4.8 or GPT-5.5 cheaper?
At 55% prefix reuse, Claude Opus 4.8 blends to about $8.14 per 1M tokens and GPT-5.5 to about $9.39. Claude Opus 4.8 is cheaper on that basis.
Which has the larger context window?
GPT-5.5 has the larger window: 1.1M vs 1M tokens.
Which captures more reuse?
Claude Opus 4.8 shows higher measured cache capture (94% vs 88%) 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.