What is the best alternative to Claude Sonnet 5?

Claude Opus 4.5 is the closest model that scores higher on the BenchLeader Index (59.7 against 59.4). 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?

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's $4.00.

Is there an open-source alternative to Claude Sonnet 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, 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 alternatives

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

As of 2 Nov 2026, Claude Sonnet 5 by Anthropic scores 59.4 on the BenchLeader Index at $4.00 per 1M tokens blended. Claude Opus 4.5 scores higher (59.7); GPT-6.1 Terra is the best cheaper model within 4 points (65.2 at $2.00); GPT-5.6 Sol 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 on the Index.

Claude Opus 4.5 Anthropic59.7 · $10.00
Kimi K2.6 Moonshot AI59.7 · $1.71
GPT-5 Pro OpenAI59.8 · $41.25

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 Google62.5 · $3.38
Qwen3.6 Max Alibaba62.4 · $2.96
Gemini 3.7 Flash Google62.2 · $1.50
Muse Spark 1.1 Meta62.2 · $2.00

Faster

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

GPT-5.6 Sol OpenAI65.4 · $8.00
Claude Sonnet 5.5 Anthropic65.1 · $4.00
GPT-6 Sol OpenAI63.5 · $4.00

Open weights

The best models whose weights you can run yourself.

Kimi K3 Moonshot AI62.1 · $6.00
GLM-5 Zhipu AI60.2 · $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 (this model)	59.4	$4.00	71	–
GPT-5.6 Sol	65.4	$8.00	127	faster
GPT-6.1 Terra	65.2	$2.00	107	cheaper
Claude Sonnet 5.5	65.1	$4.00	137	faster
GPT-6 Sol	63.5	$4.00	149	faster
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
Kimi K3	62.1	$6.00	66	open weights
GLM-5	60.2	$1.55	62	open weights
GLM 5.2	60.1	$2.15	89	open weights
GPT-5 Pro	59.8	$41.25	18	scores higher
Claude Opus 4.5	59.7	$10.00	57	scores higher
Kimi K2.6	59.7	$1.71	41	scores higher

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?: Claude Opus 4.5 is the closest model that scores higher on the BenchLeader Index (59.7 against 59.4). 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?: 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's $4.00.
Is there an open-source alternative to Claude Sonnet 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, 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.