Head-to-head
GPT-5.5 vs Claude Opus 4.5: which AI model wins in 2026?
GPT-5.5 ($30/1M out) and Claude Opus 4.5 ($25/1M out) are two of the most-used AI models in 2026. Across 3 community votes, GPT-5.5 leads with 57% approval.
Quick verdict
On Reasoning, pick GPT-5.5: the arena rates it 5/5 against 3.5/5 for Claude Opus 4.5. On budget, Claude Opus 4.5 wins: it starts at $25/1M out versus $30/1M out for GPT-5.5.
Line-by-line comparison
Strengths and weaknesses
GPT-5.5
- 1M-token context window (1,050,000) with 128K max output and reasoning effort tunable from none to xhigh
- State-of-the-art ARC-AGI-2 at 85.0% (vs 73.3% for GPT-5.4) and Terminal-Bench 2.0 at 82.7%
- Strong agentic coding autonomy: devs report it one-shots tasks that took GPT-5.4 multiple turns and fixes its own mistakes; +50 points on Code Arena vs GPT-5.4
- Aggressive discounts: 90% off cached input ($0.50/1M) and 50% off via Batch or Flex ($2.50/$15)
- Fast for a frontier reasoner: devs say it is the first GPT model comfortable to run at medium or low thinking effort
- List price doubled vs GPT-5.4 ($5/$30 vs $2.50/$15) for the same 1M-token context window
- Overly literal instruction-following: devs report it fails to infer intent in obvious places where Claude succeeds
- Trails Claude Opus 4.8 on SWE-bench Pro (58.6% vs 69.2%); HN developers still favor Claude roughly 2:1 for coding
- Sometimes too conservative with code changes or skips deep reasoning entirely, answering immediately on complex prompts
- Long-context surcharge: prompts over 272K input tokens are billed 2x input and 1.5x output for the whole session
Claude Opus 4.5
- First model past 80% on SWE-bench Verified (80.9% at launch), beating Gemini 3 Pro and GPT-5.1 on real-world coding
- 66% price cut vs Opus 4.1 ($5/$25 vs $15/$75 per 1M tokens) made Opus-tier viable for production workloads
- 48-76% fewer output tokens than Sonnet 4.5 at matched or better quality, compounding the price cut
- Effort parameter (introduced with this model) lets devs trade reasoning depth for cost and latency per call
- Strong hands-on reports: one-shot complex refactors, caught race conditions other models missed, converged in ~4 agentic iterations vs ~10 for rivals
- +29% on Vending-Bench vs Sonnet 4.5, with fewer dead-ends on long-horizon autonomous tasks
- 200K context window only (64K max output), far behind the 1M of Gemini 3 Pro and later Claude models; users reported selective attention above ~70% context fill
- Gated to $100-200/month Max tiers in Claude apps at launch; Pro subscribers were locked out and heavy users still hit limits (HN called it 'penny-wise and pound-foolish')
- Moderate latency; extended thinking adds cost and delay on simple tasks
- Superseded since early 2026: Opus 4.6/4.7/4.8 cost the same $5/$25 with 1M context and higher benchmarks, leaving 4.5 no price advantage
- Legacy API surface: manual budget_tokens extended thinking rather than the adaptive thinking of newer Claude models
Cast your verdict
One recommendation per tool per gladiator. It reshapes the crowd score everyone sees.
The arena’s verdict on GPT-5.5
Pick GPT-5.5 over GPT-5.4 if you need stronger agentic autonomy, terminal-heavy workflows, or SOTA abstract reasoning, but know the list price doubled from GPT-5.4's $2.50/$15 to $5/$30 while the 1M-token context stayed the same. Teams doing high-stakes multi-file refactoring may still prefer Claude Opus, which leads SWE-bench Pro (69.2% vs 58.6%) and infers intent better from loose prompts. Budget-sensitive users should mind the 272K-token surcharge and reports of faster limit burn, and lean on caching, Batch, or Flex to halve costs.
The arena’s verdict on Claude Opus 4.5
Pick Claude Opus 4.5 only if you have a workload already tuned and pinned to this snapshot (claude-opus-4-5-20251101) and need stability. It was a landmark release, the first past 80% on SWE-bench Verified and a 66% price cut over Opus 4.1, but Anthropic now sells Opus 4.6 through 4.8 at the identical $5/$25 rate with a 1M context window and better scores. Anyone starting a new project should choose Opus 4.8 instead, and cost-sensitive users get near-Opus coding from Sonnet 5 at $3/$15 (intro $2/$10 through Aug 2026). Avoid it entirely if your prompts approach the 200K context ceiling.
What the crowd says
On GPT-5.5
“It is painfully literal. Where Claude infers intent in obvious places, 5.5 wants everything spelled out. And the price doubled vs 5.4 for the same 1M context.”
“85 on ARC-AGI-2 and you can feel it. Stuff that used to stall my agent just resolves now. 1M context with 128K output covers every workflow I have.”
“5.5 one-shots tasks that took 5.4 three turns, and it fixes its own mistakes mid-run instead of doubling down. The reasoning effort dial from none to xhigh is genuinely useful.”
On Claude Opus 4.5
No verdicts yet. Be the first to speak.
Keep comparing
Frequently asked questions
Is GPT-5.5 better than Claude Opus 4.5?
The crowd currently sides with GPT-5.5: 57% recommend it, versus 50% for Claude Opus 4.5 (3 votes). On Reasoning, GPT-5.5 rates higher (5/5 vs 3.5/5). The right pick depends on your use case. The line-by-line comparison on this page breaks down pricing, key specs and arena ratings.
Which is cheaper, GPT-5.5 or Claude Opus 4.5?
Claude Opus 4.5 is cheaper: it starts at $25/1M out, while GPT-5.5 starts at $30/1M out.
How much do GPT-5.5 and Claude Opus 4.5 cost per 1M tokens?
GPT-5.5: $5/1M in per 1M input tokens, $30/1M out per 1M output tokens. Claude Opus 4.5: $5/1M in per 1M input tokens, $25/1M out per 1M output tokens.