Claude Opus 5.5 delivers cost and speed gains on reasoning, but doesn't outperform Opus 5

Anthropic released Claude Opus 5.5 this week with marketing emphasis on three advantages: lower cost, faster output, and capability parity with Claude Opus 5. The real-world picture from direct testing reveals a more nuanced story of trade-offs between cost savings and reasoning capability.

Pricing and performance claims#

The company reduced API costs significantly: Opus 5.5 runs at $4 per million input tokens and $20 per million output tokens, compared with $5 and $25 for Opus 5—a 20% saving from pricing alone. Anthropic claims the model costs 40% less overall and produces output 30% faster. The additional 20% savings beyond the price cut depends on the model using fewer tokens to solve identical problems.

Head-to-head testing on complex reasoning#

To assess whether these claims translate to user experience, a The New Stack editor tested both models on three challenging logic problems using identical prompts and adaptive thinking enabled.

Logic grid puzzle: Seven engineers assigned across days, languages, services, and cities, with 22 clues to solve. Both models produced correct answers, but Opus 5.5 finished in 65 seconds using 7,573 tokens ($0.16), while Opus 5 took 108 seconds and 10,621 tokens ($0.27)—a 43% cost reduction.

Constrained job ordering problem: Neither model succeeded. The task required reordering 10 deploy jobs with strict derangement and adjacency constraints. Both models exhausted their 48,000-token limits thinking without producing answers. When expanded to 128,000 tokens, Opus 5.5 ran for 19 minutes before the API returned a refusal, while Opus 5 used all tokens over 25 minutes with no solution.

Stone removal game: Both models solved all three subproblems correctly through combinatorial game theory. Opus 5.5 answered in 215 seconds with 28,740 tokens ($0.58), while Opus 5 required 624 seconds and 74,981 tokens ($1.88)—Opus 5.5 cost 69% less and used 62% fewer tokens.

Key findings#

Across all tests, Opus 5.5 generated tokens at 103.4 per second versus Opus 5's 93.1—an 11% speed advantage, falling short of the advertised 30% claim. Total cost savings ranged from 43% on the logic grid to 69% on the stone game, validating Anthropic's efficiency gains.

On reasoning accuracy, neither model outperformed the other; they matched on solved problems and both failed on the combinatorial ordering challenge. The edge went to Opus 5.5 purely on resource efficiency.