Claude Sonnet 5.5: Anthropic's faster mid-tier model that beats Opus 5.5 on agentic coding at half the price
Anthropic released Claude Sonnet 5.5, the second model in the Claude 5.5 family: 30%+ faster outputs, up to 30% cheaper per task than Sonnet 5 at unchanged $2/$10 per Mtoken pricing, and a 70.6% Terminal-Bench 4.0 score that beats flagship Opus 5.5 at half the token cost.
Why it matters
A rare inversion of the model hierarchy: the mid-tier model beats the flagship on agentic coding benchmarks (Terminal-Bench 4.0: 70.6% vs Opus 5.5's 66.4%) while costing half per token - the price/performance frontier for agentic coding workloads just moved down-market.
What you could build with it
A devtools startup could rebuild its agentic coding product's default model tier on Sonnet 5.5: flagship-class agentic coding at mid-tier pricing means higher margins per seat or undercutting incumbents on per-task pricing.
Does it hold up?
Days old, so evidence is thin: early independent runs (CodeRabbit) confirm the benchmark shape for code review, but Merkle.Press flags higher token consumption that could erode the cost story; verdict pending real workload reports.
Built with Claude Sonnet 5.5
- Sonnet 5.5 vs Opus 5.5 code-review benchmarks (CodeRabbit)article · Independent code-review benchmarks: Sonnet 5.5 moves coverage back up without losing precision; finds thinking-on-by-default and effort dial (low..max) the key migration points for review workflows.
- Claude Sonnet 5.5 release coverage: benchmarks and cybersecurity controlsarticle · Deep coverage of the launch: agentic coding benchmark jumps, frontier-style cybersecurity controls and anti-distillation classifiers added for European AI Act compliance.
- Claude Sonnet 5.5 on DigitalOcean Inference (Sept 28 release notes)article · Sonnet 5.5 listed as available for serverless inference and the Agent Development Kit on DigitalOcean Inference the day of launch - immediate third-party platform availability.
- Sonnet 5.5 outperforms Opus but at what token cost (Merkle.Press)article · Independent testing confirms the benchmark gains but flags that Sonnet 5.5 consumes more tokens than any competitor measured - the per-task cost advantage may be thinner than Anthropic's headline numbers suggest.
Learn more
First spotted on article: source.
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