Question 1

What is Claude Sonnet 4.5?

Accepted Answer

Claude Sonnet 4.5 is a model from Anthropic, released on Sep 29, 2025. Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with improvements across system design, code security, and specification adherence. The model is designed for extended autonomous operation, maintaining task continuity across sessions and providing fact-based progress tracking. Sonnet 4.5 also introduces stronger agentic capabilities, including improved tool orchestration, speculative parallel execution, and more efficient context and memory management. With enhanced context tracking and awareness of token usage across tool calls, it is particularly well-suited for multi-context and long-running workflows. Use cases span software engineering, cybersecurity, financial analysis, research agents, and other domains requiring sustained reasoning and tool use.

Question 2

How much does Claude Sonnet 4.5 cost?

Accepted Answer

On the Respan gateway, input starts at $3.00 per 1M tokens on every provider, and output starts at $15.00 per 1M tokens on every provider, after gateway discounts.

Question 3

Which providers serve Claude Sonnet 4.5 on Respan?

Accepted Answer

5 providers serve Claude Sonnet 4.5: Anthropic, Bedrock, OpenRouter, and Perplexity. Perplexity requires your own provider API key (BYOK).

Question 4

What is Claude Sonnet 4.5's context window?

Accepted Answer

Claude Sonnet 4.5 accepts up to 1M tokens of context on its largest provider route.

Question 5

How do I use Claude Sonnet 4.5 with the Respan gateway?

Accepted Answer

Point any OpenAI-compatible SDK at https://api.respan.ai/api/ with your Respan API key and set the model to "anthropic/claude-sonnet-4-5-20250929". To set it up with a coding agent, copy the agent setup prompt at the top of this page.

Question 6

How fast is Claude Sonnet 4.5?

Accepted Answer

Over the last 30 days of requests through the Respan gateway, the fastest provider was Anthropic at 783 tokens per second, and the lowest response latency was 1.9 seconds on OpenRouter. Speed varies with request size and provider.

Question 7

Where does Claude Sonnet 4.5 rank on the Respan Index?

Accepted Answer

Claude Sonnet 4.5 scores 29.1 out of 100 on the Respan Index v1.1, ranking #65 of 138 models. By category: Coding 12.9, Agents 41.7, Reasoning 19.2, Knowledge & language 31.1, and Human preference 50.0. The Respan Index combines independent and lab-reported benchmark results into one score, using benchmark data collected by llmmetric.com.

Question 8

How does Claude Sonnet 4.5 score on benchmarks?

Accepted Answer

Claude Sonnet 4.5 has 40 published benchmark scores, including SWE-bench Verified 77.2%, Tau2-bench Telecom 98%, and GPQA Diamond 83.4%. Each score links to where it was published; the data is collected by llmmetric.com.

Provider	Context	Input	Output
Anthropic`anthropic/claude-sonnet-4-5`	200K	$3.00/M	$15.00/M
Anthropic`anthropic/claude-sonnet-4-5-20250929`	200K	$3.00/M	$15.00/M
Bedrock`bedrock/us.anthropic.claude-sonnet-4-5-20250929-v1:0`	200K	$3.00/M	$15.00/M
OpenRouter`openrouter/anthropic/claude-sonnet-4.5`	1M	$3.00/M	$15.00/M
PerplexityBYOK only`perplexity/anthropic/claude-sonnet-4-5`	200K	$3.00/M	$15.00/M

Claude Sonnet 4.5

Providers

Certified where it counts.

Pricing

Cost by volume

Throughput and latency

Output speed

Time to first token

Response latency

Benchmarks

Respan Indexv1.1

Coding5

Apps

Claude Sonnet 4.5 FAQ

Works with your entire stack

Built for AI agents.
Break less.
Ship more.

Agents11

Reasoning9

Math7

Knowledge3

Multimodal2

Arena2

Other1