Overview
Fast-mode variant of Opus 4.8 - identical capabilities with higher output speed at 2x pricing relative to regular Opus 4.8.
Get up to 2.5x higher output tokens per second from supported Claude Opus models.
Fast mode delivers up to 2.5x higher output tokens per second from Claude Opus 4.8 and Claude Opus 4.7 at premium pricing. Set speed: "fast" with the fast-mode-2026-02-01 beta header on your request to opt in.
#How fast mode works
Fast mode runs the same model with a faster inference configuration. There is no change to intelligence or capabilities.
- Up to 2.5x higher output tokens per second compared to standard speed
- Speed benefits are focused on output tokens per second (OTPS), not time to first token (TTFT)
- Same model weights and behavior (not a different model)
- Compatible with streaming, where the OTPS gain is most visible
#Basic usage
client = anthropic.Anthropic()
response = client.beta.messages.create(
model="claude-opus-4-8",
max_tokens=4096,
speed="fast",
betas=["fast-mode-2026-02-01"],
messages=[
{"role": "user", "content": "Refactor this module to use dependency injection"}
],
)
print(response.content[0].text)
Usage example
cURL
curl https://www.namoclaw.ai/api/v1/chat/completions \
-H "Authorization: Bearer $API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "anthropic/claude-4.8-opus-fast-20260528",
"messages": [{ "role": "user", "content": "Hello!" }]
}'Default parameters
| Name | Type | Default | Description |
|---|---|---|---|
| temperature | number | — | — |
| top_p | number | — | — |
| top_k | number | — | — |
| frequency_penalty | number | — | — |
| presence_penalty | number | — | — |
| repetition_penalty | number | — | — |
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