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Claude Sonnet 4.5 API — how expensive is Claude Sonnet 4 API?

The Sonnet that made agentic coding mainstream in 2025. Served under its dated id at $3 / $15 for teams that have not moved to Sonnet 5 yet.

Searching for the Claude Sonnet API? Claude Sonnet 4.5 is the current Claude Sonnet release — same endpoint and key across every version, so code written for the Claude Sonnet API works unchanged when new versions ship.

Pricing

Rate	Official	AI Prime Tech	You save
Input (per 1M tokens)	$3	$0.3	90% OFF
Output (per 1M tokens)	$15	$1.5	90% OFF

Pay-as-you-go, no subscription. Prompt caching is passed through from the upstream model.

Claude Sonnet 4.5 API pricing in detail

Anthropic pricing for Claude Sonnet 4.5 is per million input tokens and per million output tokens: $3 and $15 at list. Output tokens are the expensive side, and long answers, extended thinking and agent loops are output-heavy — which is why a model that gets the task right in one attempt is usually cheaper than a nominally cheaper one that needs three. On this gateway the same list rates are billed in credits that cost 90% less than face value, so the effective price is $0.3 per million input tokens and $1.5 per million output tokens.

Prompt caching. A long, stable system prompt or document can be cached; cache writes cost 25% more than a normal input token, and cache hits (cache reads) about a tenth of one, so a 20k-token system prompt reused across a session costs a fraction of resending it. The gateway forwards the cache_control blocks unchanged, and cache read tokens show separately in your usage log.

Batch processing. Anthropic’s Batch API prices asynchronous jobs at half the real-time rate. The gateway serves the real-time Messages API only — batch endpoints are not proxied — so if half-price overnight batches are the core of your workload, run those directly on Anthropic and keep the interactive traffic here, where the credit discount is larger than the batch discount anyway.

Worked example. A Claude Code session that sends 2 million input tokens and receives 100k output tokens costs $7.50 at Anthropic list price and $0.75 here; with a cached system prompt the input side drops further.

Best for

Pinned production workloads
Coding agents built on 4.5
Migration comparisons
200K-context tasks

Specifications

Release	September 2025
Context window	200K tokens
Max output	64K tokens
Vision	Yes
Tool use	Yes
Thinking	Extended (budget_tokens)
Model ID	claude-sonnet-4-5-20250929

Quick start

Use your existing SDK — just point it at our gateway and use model ID claude-sonnet-4-5-20250929:

export ANTHROPIC_BASE_URL=https://aiprimetech.io
export ANTHROPIC_AUTH_TOKEN=sk-your-key-here

Works with Claude Code, Cursor, Cline, Aider, and the official Anthropic / OpenAI SDKs. See the 60-second setup guide.

Start using Claude Sonnet 4.5 today

Instant API key, pay-as-you-go, crypto accepted. 90% below official pricing.

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Frequently asked questions

How expensive is Claude Sonnet 4 API?

Claude Sonnet 4.5 lists at $3 per million input tokens and $15 per million output tokens on Anthropic pricing. Through this gateway the same calls cost $0.3 / $1.5, because credits are bought 90% below face value. Cache hits are cheaper still.

What is the model id for Claude Sonnet 4.5?

claude-sonnet-4-5-20250929 — pass it as model in the Messages API or select it with /model in Claude Code. It is listed by GET /v1/models on this gateway.

Does the Claude Sonnet 4.5 API support prompt caching and batch processing here?

Prompt caching yes — cache_control is forwarded and cache reads are billed at the reduced rate. The Batch API is not proxied; interactive, real-time requests only.

Is this the official Anthropic API?

No. AI Prime Tech is an independent gateway that serves Claude Sonnet 4.5 through the same Messages API shape and model id. Nothing about the model changes; the billing does.

All models: Claude Fable 5.1 · Claude Opus 5.5 · Claude Sonnet 5.5 · Claude Opus 5 · Claude Sonnet 5 · Claude Fable 5 · Claude Opus 4.8 · Claude Opus 4.7 · Claude Opus 4.6 · Claude Sonnet 4.6 · Claude Opus 4.5 · Claude Haiku 4.5 · Claude 1M Context · GPT-6 Astra · GPT-6 Sol · GPT-6 Luna · GPT-5.6 · GPT-5.6 Sol · GPT-5.6 Terra · GPT-5.6 Luna · GPT-5.5 · GPT-5.4 · GPT-5.4 Mini · GPT-5.3 Codex Spark · GPT-5.2 · GPT-5.2 Pro · Gemini 3 Pro · Gemini 3 Flash · MiniMax M3

AI Prime Tech is an independent third-party API gateway. Model names and trademarks belong to their respective owners (Anthropic, OpenAI, Google, MiniMax). No affiliation or endorsement is implied. Effective price = official rate ÷ the top-up multiplier: the gateway bills official per-token rates in credits, and credits are bought below face value. Rates shown are read from this site's live settings.