Claude Sonnet 4.6 API pricing and setup
Claude Sonnet 4.6 (claude-sonnet-4-6) is a Anthropic model. It is available through the relay.fast API with one relay.fast key and pay-as-you-go billing.
Prices checked from the live catalog. "From" is the lowest price among the relay.fast sources that currently serve the model. The price you pay depends on the source your request uses and can change on any day. The pricing page always shows current values.
| Official input price | $3 per 1M tokens |
|---|---|
| Official output price | $15 per 1M tokens |
| relay.fast input from | $0.0833 per 1M tokens |
| relay.fast output from | $0.417 per 1M tokens |
| Cache read from | $0.00833 per 1M tokens |
| Lower than the official price by | up to 97% |
| Context window | 1M tokens |
| Endpoints | /v1/messages, /v1/chat/completions |
Example request
Keep the key in the RELAY_FAST_API_KEY environment variable.
curl https://relay.fast/v1/messages \
-H "x-api-key: $RELAY_FAST_API_KEY" \
-H "anthropic-version: 2023-06-01" \
-H "Content-Type: application/json" \
-d '{"model":"claude-sonnet-4-6","max_tokens":256,"messages":[{"role":"user","content":"Hello"}]}'Use Claude Sonnet 4.6 in coding tools
Setup guides: Claude Code, Codex, Cursor, Cline, Kilo Code, OpenCode, Aider. The API docs have one-command installers.
Frequently asked questions
How much does the Claude Sonnet 4.6 API cost?
On 2026-11-05, relay.fast charges from $0.0833 per 1M input tokens and $0.417 per 1M output tokens for Claude Sonnet 4.6, against the official $3 and $15. The price depends on the source your request uses and can change; https://relay.fast/pricing/claude-sonnet-4-6 shows the current value.
What is the context window of Claude Sonnet 4.6?
Claude Sonnet 4.6 accepts up to 1M tokens of context in the relay.fast catalog. Output limits depend on the model and client settings.
Which API endpoint does Claude Sonnet 4.6 use?
Call /v1/messages and /v1/chat/completions with a relay.fast API key. OpenAI-compatible SDKs use the base URL https://relay.fast/v1.
Do I need a Anthropic account to use Claude Sonnet 4.6?
No. You use a relay.fast account and API key. relay.fast is an independent API gateway and is not affiliated with Anthropic.
Other Anthropic models
Claude Fable 5 · Claude Fable 5.1 · Claude Haiku 4.5 · Claude Haiku 5.5 · Claude Opus 4.6 · Claude Opus 4.7 · Claude Opus 4.8 · Claude Opus 5 · Claude Opus 5.5 · Claude Sonnet 5 · Claude Sonnet 5.5