Where do I create an API key and buy tokens?

Both happen on api.reapi.ai — the chat workspace runs as its own platform separate from the image / video task gateway at reapi.ai. Sign up at api.reapi.ai, generate a key under API Keys, and top up under Top Up. A reapi.ai/settings/apikeys key will not authenticate against the chat endpoint.

Is the Claude Opus 4.8 API OpenAI-compatible?

Yes. The Claude Opus 4.8 API is a drop-in for OpenAI's /v1/chat/completions — same request shape, same `messages` array, same `stream` / `temperature` / `top_p` / `max_tokens` parameters, same SSE wire format. Most teams migrate by changing the base URL to https://api.reapi.ai/v1, swapping the API key, and setting `model: "claude-opus-4-8"`. The native Anthropic Messages format at /v1/messages is also available for SDK callers that prefer it.

What is the Claude Opus 4.8 context window?

Claude Opus 4.8 has a 1M token context window and supports up to 128K output tokens per response on the synchronous API. Long inputs benefit from prompt caching — cache stable parts of the prompt once and pay only the cache-read rate on subsequent calls.

How is Claude Opus 4.8 different from Claude Opus 4.7?

Claude Opus 4.8 builds on Opus 4.7 with improvements across benchmarks and is available at the same per-token price. Anthropic highlights better honesty — around four times less likely to let code flaws pass unremarked — sharper agentic judgement, and more efficient tool calling. Opus 4.7 and earlier remain available on api.reapi.ai for traffic already validated against them; switching is a one-line change in the `model` field.

Does Claude Opus 4.8 support vision and multimodal input?

Yes. Claude Opus 4.8 accepts text and image inputs in the same call — useful for screenshots, diagrams, document scans, chart analysis, and multimodal review flows. Images are passed as URL or content parts on the standard Chat Completions content-parts payload.

How does prompt caching work and when is it worth it?

Prompt caching lets you mark a portion of the prompt (system instructions, RAG context, long documents) as cacheable. The first call writes the cache; subsequent calls reuse it and pay only the low cache-read rate on those tokens. Worth turning on for long system prompts reused across users, recurring RAG context, and multi-turn agents replaying long histories. See the pricing card for the resolved rates.

What is the `group` parameter?

`group` selects a token group on the api.reapi.ai gateway, which routes the request to a specific channel pool. `default` is the standard pool and covers nearly every workload. You can leave the field out of the body if you're happy with the default routing.

Claude Opus 4.8 API — Anthropic's Most Capable Model

Claude Opus 4.8 is Anthropic's most capable model for complex reasoning and long-horizon agentic coding — 1M context, 128K max output, vision input, prompt caching, and OpenAI-compatible /v1/chat/completions in one call. Pay-as-you-go pricing in USD.

Price

Input tokens$5/ 1M tokens

Output tokens$25/ 1M tokens

Cache read$0.5/ 1M tokens

Web search$0.015/ request

Get API key View API docs

02use cases

What you can build

Real workflows powered by this model.

01/case

Long-horizon agentic coding

Claude Opus 4.8 is Anthropic's most capable model for high-autonomy engineering work — multi-service refactors, codebase-scale migrations, and agent runs that have to stay on-task across many steps. Early testers report sharper judgement: it asks the right questions, catches its own mistakes, and pushes back when a plan isn't sound.

Read the API docs

Claude Opus 4.8 reasoning carefully through a high-stakes task

02/case

High-stakes reasoning where mistakes are costly

One of the most prominent changes in Opus 4.8 is honesty: Anthropic's evaluations show it is around four times less likely than its predecessor to let flaws in the code it writes pass unremarked, and more likely to flag uncertainty instead of overclaiming. Pick it when a confident-but-wrong answer has real downstream cost.

Claude Opus 4.8 reasoning across a 1M-token analysis pack

03/case

Large-context analysis and review

Feed entire codebases, long research packs, multi-file technical material, or full policy documents into a single Claude Opus 4.8 request. The 1M token context window means analysis-heavy workflows rarely need chunking — the model sees the whole input and returns a coherent answer.

03pricing

Pricing

Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.

Category	Unit	Price
Tokens
Input tokens	1M tokens	$5
Output tokens	1M tokens	$25
Cache read	1M tokens	$0.5
Tools
Web search	request	$0.015

05why

Why reAPI

OpenAI-compatible drop-in for Anthropic's top model

The Claude Opus 4.8 API speaks OpenAI Chat Completions verbatim. Moving an existing OpenAI integration to Anthropic's most capable model is a base URL, an API key, and a model-string change — not a platform rewrite. The same `messages` array, the same streaming format, and the native Anthropic /v1/messages surface is available too for SDK callers that prefer it.

Most-capable reasoning and agentic coding

Claude Opus 4.8 is Anthropic's most capable model — built on Opus 4.7 with improvements across benchmarks, available at the same price. Adaptive thinking and an effort control that defaults to high mean it puts real work into hard problems. Route premium coding and high-autonomy agent traffic here; send simpler calls to cheaper Claude or GPT models on the same key.

One key across GPT, Claude, and Gemini

A single api.reapi.ai key unlocks Claude Opus 4.8 alongside GPT-5.5, Gemini 3.1 Pro, and every other frontier chat model on the platform. Compare vendors, add fallbacks, and route traffic per call with a configuration change instead of an integration project.

06vs

Claude Opus 4.8 vs Claude Opus 4.7

Opus 4.8 is built on Opus 4.7 and ships at the same per-token price, so the upgrade is a one-line model-string change. Here is what Anthropic says actually changed between the two generations.

Capability

Claude Opus 4.8 on reAPI

Claude Opus 4.7

Capability tier

Anthropic's most capable model for complex reasoning and long-horizon agentic coding.

Previous flagship Opus generation; still available on the same key.

Per-token price

Same input and output rates as Opus 4.7 — the upgrade carries no price increase.

Same input and output rates as 4.8.

Code self-checking (honesty)

Around four times less likely to let flaws in its own code pass unremarked, per Anthropic's evaluations.

Higher rate of unremarked code flaws than 4.8.

Agentic judgement & tool use

Sharper judgement on agentic tasks; more efficient tool calling — fewer steps for the same result.

Capable agentic model, with more tool-calling steps than 4.8.

Fast mode

Runs at 2.5× speed, now three times cheaper than fast mode was on previous models.

Fast mode available at the previous, higher pricing.

Context, output & vision

1M-token context, 128K max output, text + image input — at parity with 4.7.

1M-token context, 128K max output, text + image input.

Comparison reflects publicly documented behavior from Anthropic's Claude Opus 4.8 announcement and model documentation at the time of writing. Model behavior and pricing can change; check the pricing card above and the API docs for current values.

07quickstart

Ship the Claude Opus 4.8 API in three steps

step 01
Create an account and key on api.reapi.ai
Sign up at api.reapi.ai, open the console, generate an API key under API Keys, and top up tokens under Top Up. The chat workspace is separate from the reapi.ai image/video gateway — keys do not cross over.
Open
step 02
Send your first request
POST https://api.reapi.ai/v1/chat/completions with `model: "claude-opus-4-8"`, your `messages` array, and `max_tokens` set generously. The endpoint is OpenAI-compatible, including streamed responses; the native Anthropic /v1/messages format works too.
Open
step 03
Tune for cost and stability
Use prompt caching for stable system prompts and recurring long inputs to bring repeated-context costs down. Reserve Claude Opus 4.8 for the highest-value calls and route everything else to a cheaper model on the same key.
Open

08faq

Frequently asked questions

Common questions about this model.

Claude Opus 4.8 is billed pay-as-you-go in USD against your api.reapi.ai token balance — see the pricing card on this page for the live per-1M-token input and output rates. The same card lists the prompt-caching cache-read rate and the per-request web-search rate. Cache hits are dramatically cheaper than re-sending the same tokens. Failed requests are not charged.

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10api reference

docs/api/claude-opus-4-8

API reference

Drop-in code and the full parameter table.

View full reference

curl https://api.reapi.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-4-8",
    "group": "default",
    "messages": [
      { "role": "user", "content": "Hello" }
    ],
    "stream": true,
    "max_tokens": 4096,
    "temperature": 0.7
  }'

start building

Ready to ship?

Try it in the playground or grab an API key to integrate now.

Get API key Get API key

What you can build

Real workflows powered by this model.

01/case