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 standard /api/v1/chat/completions in one call. Pay-as-you-go from your reAPI balance.
Start with the prompt in the composer or choose an example.
Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.
44% off official pricing· Input / output tokens
One 1K-token prompt with a 1K-token answer at the cheapest tier.
Claude Opus 4.8 is Anthropic's model for complex reasoning and long-horizon agentic coding, served on an OpenAI-compatible /api/v1/chat/completions endpoint. It carries a 1M-token context window, up to 128K output tokens per call, vision input, prompt caching, tool use, and the temperature and top_p controls. Billing is per million tokens with input and output priced separately, cached reads charged at a lower rate, and web search billed per request.
Real-world workflows and production use cases you can build and ship with this model.
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
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.
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.
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.
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.
A single reAPI 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.
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.
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.
Sign in to reAPI and create a key under API keys. That one key reaches Claude Opus 4.8 and every other model on the platform, billed from a single balance.
OpenPOST https://reapi.ai/api/v1/chat/completions with `model: "claude-opus-4-8"`, your `messages` array, and `max_tokens` set generously. The endpoint uses the standard chat-completions format, including streamed responses.
OpenUse 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.
Opencurl https://reapi.ai/api/v1/chat/completions \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-opus-4-8",
"messages": [
{ "role": "user", "content": "Hello" }
],
"stream": true,
"max_tokens": 4096,
"temperature": 0.7
}'Rejected synchronously with the failing field named. Check enum values, ranges, and URL fields — nothing is charged.
401 means a missing or invalid Bearer key; 402 means the reserve exceeds your balance. Manage keys and credits in the console.
Reference material and outputs pass automated moderation. Rejected tasks fail with a clear error and a full refund.
A task that reaches a failed state is never charged — the reserve refunds automatically. Keep the task id and retry when ready.
Common questions about this model.
Guides
How to use Claude Opus 4.8: the official benchmark table, the honesty gain, Dynamic Workflows, the effort default that moved, and what to plan when migrating.
Guides
Claude Opus 4.8 is Anthropic's most capable model for reasoning and agentic coding. Here is what's new, its benchmarks, pricing, and how to access it.
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