What is the best alternative to Claude Sonnet 5.5?

GPT-6.1 Terra is the closest model that scores higher on the BenchLeader Index (65.2 against 65.1). For less money, GPT-6.1 Terra scores 65.2 at $2.00 per 1M tokens.

Is there a cheaper alternative to Claude Sonnet 5.5?

Yes: GPT-6.1 Terra (65.2, $2.00), Gemini 3.5 Flash (62.5, $3.38) and Qwen3.6 Max (62.4, $2.96), each within 4 Index points and cheaper than Claude Sonnet 5.5's $4.00.

Is there an open-source alternative to Claude Sonnet 5.5?

The best open-weights models on the BenchLeader Index are Kimi K3 (62.1), GLM-5 (60.2) and GLM 5.2 (60.1). You can download and run them yourself; check each licence on its model page.

How are these alternatives chosen?

From the models ranked on the BenchLeader Index today: the ones just above Claude Sonnet 5.5, cheaper ones within 4 points, ones at least 1.5× as fast within 4 points, and the best open-weights models. Prices are list prices blended three input tokens to one output.

Anthropic

Claude Sonnet 5.5 alternatives

Data as of 2 Nov 2026 · ranked on the BenchLeader Index

As of 2 Nov 2026, Claude Sonnet 5.5 by Anthropic scores 65.1 on the BenchLeader Index at $4.00 per 1M tokens blended. GPT-6.1 Terra scores higher (65.2); GPT-6.1 Terra is the best cheaper model within 4 points (65.2 at $2.00); Muse Spark 1.1 is at least 1.5× as fast at a similar score; Kimi K3 is the best open-weights option (62.1).

Scores higher

The closest models above Claude Sonnet 5.5 on the Index.

GPT-6.1 Terra OpenAI compare65.2 · $2.00
Claude Opus 5 Anthropic compare65.4 · $10.00
GPT-5.6 Sol OpenAI compare65.4 · $8.00

Cheaper, nearly as good

Within 4 Index points, for less per token.

GPT-6.1 Terra OpenAI compare65.2 · $2.00
Gemini 3.5 Flash Google compare62.5 · $3.38
Qwen3.6 Max Alibaba compare62.4 · $2.96
Gemini 3.7 Flash Google compare62.2 · $1.50
Muse Spark 1.1 Meta compare62.2 · $2.00

Faster

At least 1.5× the output speed, within 4 points.

Muse Spark 1.1 Meta compare62.2 · $2.00
Muse Spark 1.2 Meta compare61.6 · $2.00

Open weights

The best models whose weights you can run yourself.

Kimi K3 Moonshot AI compare62.1 · $6.00
GLM-5 Zhipu AI compare60.2 · $1.55
GLM 5.2 Zhipu AI60.1 · $2.15

Every alternative side by side

Model	Index	$ / 1M blended	Tokens / s	Why
Claude Sonnet 5.5 (this model)	65.1	$4.00	137	–
Claude Opus 5	65.4	$10.00	53	scores higher
GPT-5.6 Sol	65.4	$8.00	127	scores higher
GPT-6.1 Terra	65.2	$2.00	107	scores higher, cheaper
Gemini 3.5 Flash	62.5	$3.38	190	cheaper
Qwen3.6 Max	62.4	$2.96	–	cheaper
Gemini 3.7 Flash	62.2	$1.50	91	cheaper
Muse Spark 1.1	62.2	$2.00	206	cheaper, faster
Kimi K3	62.1	$6.00	66	open weights
Muse Spark 1.2	61.6	$2.00	296	faster
GLM-5	60.2	$1.55	62	open weights
GLM 5.2	60.1	$2.15	89	open weights

Prices are list prices blended three input tokens to one output; speeds are measured medians, credited on each model page. The Index is BenchLeader's own, from independent benchmarks.

Questions people ask

What is the best alternative to Claude Sonnet 5.5?: GPT-6.1 Terra is the closest model that scores higher on the BenchLeader Index (65.2 against 65.1). For less money, GPT-6.1 Terra scores 65.2 at $2.00 per 1M tokens.
Is there a cheaper alternative to Claude Sonnet 5.5?: Yes: GPT-6.1 Terra (65.2, $2.00), Gemini 3.5 Flash (62.5, $3.38) and Qwen3.6 Max (62.4, $2.96), each within 4 Index points and cheaper than Claude Sonnet 5.5's $4.00.
Is there an open-source alternative to Claude Sonnet 5.5?: The best open-weights models on the BenchLeader Index are Kimi K3 (62.1), GLM-5 (60.2) and GLM 5.2 (60.1). You can download and run them yourself; check each licence on its model page.
How are these alternatives chosen?: From the models ranked on the BenchLeader Index today: the ones just above Claude Sonnet 5.5, cheaper ones within 4 points, ones at least 1.5× as fast within 4 points, and the best open-weights models. Prices are list prices blended three input tokens to one output.