Claude Opus 4.8

claude-opus-4-8

Claude Opus 4.8 is the most powerful general-purpose model in the Anthropic Opus series. It supports text, image, and file inputs as well as text output, and features reasoning support and a 1M token context window. It is suitable for highly autonomous agents, long-running agent work, knowledge work, and memory-driven tasks where consistency over long sessions is important. It is especially powerful in multi-step reasoning, complex coding, and end-to-end project orchestration — large codebases, multi-stage debugging, and long-running asynchronous agent pipelines. Beyond coding, it also handles knowledge work such as drafting documents, building presentations, and analyzing data, while maintaining quality over very long outputs.

Context window1.0M

ProviderClaude

Released2026/05/29

Playground

Pricing

The same model is available through multiple service channels — choose based on latency, reliability and cost.

Prices in $ / 1M tokens

To pick a channel, add a provider field to the request body, for example "provider": { "channel": "direct" }. Valid values are direct / stable / economical; omit it to use the default channel.

Direct

Direct upstream connection — best when you need native behavior and the full context window.

Input	Output	Cache read	Cache write
5.00/M	25.00/M	0.50/M	6.25/M

Overview

Input

Text Image

Output

Text

Claude Opus 4.8 API: The Strongest General-Purpose Flagship Model in the Opus Series

Claude Opus 4.8 is the most capable general-purpose model in Anthropic's Opus series. Highly autonomous, it achieves industry-leading performance in long-horizon agent execution, knowledge work, and memory tasks. It supports text, image, and file input, with reasoning capabilities and a 1M token context window.

Opus 4.8 excels at work that needs to stay consistent over long periods: agent tasks spanning hours, multi-stage project orchestration, and long sessions that need to remember early decisions. Compared with Opus 4.7, its writing is clearer and gentler, it reports proactively more often, and its code review is better at detecting defects.

SeaWhale AI provides Opus 4.8 through the Anthropic native Messages API, with support for adaptive thinking, five Effort levels, task budget, and full tool calling.

Get API Key · Model ID: claude-opus-4-8

Why Choose Claude Opus 4.8

Strongest general-purpose model in the Opus series — the industry benchmark for long-horizon agent execution, knowledge work, and memory tasks
1M token context — standard pricing, no long-context premium
Adaptive thinking + five Effort levels — from low to max, precisely tune intelligence and cost by routing
Clearer writing and proactive reporting — provides periodic progress updates on long tasks without needing extra scaffolding
Stronger code review — better real defect detection rate and explanation quality than the previous generation

Core Capabilities

01 Long-Horizon Agent Execution

Opus 4.8 is the go-to model for long-running autonomous work — complex refactoring, overnight coding runs, without needing human course correction midway. Give it the complete task brief up front and let it run to completion at high Effort for the best results.

Complex refactoring and end-to-end feature implementation
Multi-stage project orchestration and task decomposition
Maintaining decision consistency across long sessions

02 Memory and Filesystem Notes

Opus 4.8 performs significantly better at reading and writing filesystem-based memory. Give it a memory directory and explain when to use it, and it will proactively record what it has learned and retrieve it in subsequent tasks.

Persistent memory read/write across sessions
Retrieving relevant context from existing notes
Consolidating intermediate conclusions in long tasks

03 Code Review and Debugging

Stronger than Opus 4.7 in real defect detection and explanation clarity — provides a working fix in one pass, and correctly identifies intermittent flaky tests rather than declaring the issue fixed after a single green run.

High-precision defect localization and root cause analysis
Identifying intermittent failures and race conditions
Pull Request-level quality review

04 In-Session System Prompts and Cache Friendliness

Supports inserting role: system messages into the messages array, letting you pass context that is only known mid-session (mode switches, disk changes, remaining budget) to the model without invalidating the cached prefix.

Injecting context mid-session without invalidating the cache
Prompt caching significantly reduces long-session costs
Context compaction supports extremely long conversations

Best Use Cases

Use case	Description
Long-horizon coding agent	Starts from a single instruction and completes complex refactoring or overnight development tasks
Knowledge work	Research synthesis, report writing, financial and policy analysis
Memory-driven assistant	Remembers user preferences, project conventions, and historical decisions across sessions
Code review	High-recall defect detection, root cause localization, and fix suggestions
Multi-stage business automation	Enterprise process orchestration that needs to stay consistent over long periods
Documents and spreadsheets	Structured reports, workbooks, and presentations

Claude Opus 4.8 vs Opus 4.7 and Sonnet 5

Capability	Claude Opus 4.8	Claude Opus 4.7	Claude Sonnet 5
Model ID	`claude-opus-4-8`	`claude-opus-4-7`	`claude-sonnet-5`
Positioning	Strongest general-purpose model in the Opus series	Previous-generation Opus	Balance of speed and intelligence
Context window	1M tokens	1M tokens	1M tokens
Max output	128K tokens	128K tokens	128K tokens
Writing style	Clearer and gentler, with fewer stacked qualifiers	More direct and concise	Balanced
Proactive reporting	Provides periodic progress by default	Requires prompt guidance	Provides progress by default
In-session system messages	Supported	Not supported	Not supported

For specific billing, refer to the real-time price card at the top of the page.

How to Use the Claude Opus 4.8 API

1. Create a SeaWhale AI API key Generate a key in the console and top up your balance.

2. Explicitly enable adaptive thinking Opus 4.8 will not think if the thinking field is omitted; you need to explicitly pass {"type": "adaptive"}.

3. Make a request

curl -X POST https://api.atalk-ai.com/v1/messages \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "claude-opus-4-8",
    "max_tokens": 32000,
    "thinking": {"type": "adaptive"},
    "output_config": {"effort": "high"},
    "messages": [
      {"role": "user", "content": "Refactor the dependency injection approach for this module, add the missing tests, and verify they pass."}
    ]
  }'

FAQ

What improvements does Opus 4.8 bring over 4.7? The request API is completely identical, with no new breaking changes. The improvements are focused on long-horizon execution, writing clarity, proactive reporting, and code review quality. Migration only requires changing the model ID and re-tuning your prompts.

How should I choose Effort? We recommend starting with high as the default, running medium / high / xhigh on your own evaluation set, then deciding by routing. High Effort often reduces the total number of rounds and total cost on agent tasks.

Is there an extra charge for long context? No. The 1M token context is billed at standard API prices, with no long-context premium.

Why does the model keep asking me whether it should continue? Opus 4.8 is more cautious than the previous generation. If you state in the system prompt "make small decisions on your own; only ask when scope changes or destructive operations are involved," you can significantly reduce the frequency of questions.

Why does it use tools less than expected? Opus 4.8 is fairly conservative with search, sub-agents, memory, and custom tools. If you explicitly write "when this should be called" in the system prompt and in each tool's description, the trigger rate will improve noticeably.

Can I change the system prompt mid-session? Yes. Just append a role: system message to messages; it will not invalidate the cached prefix.

Why Choose SeaWhale AI for the Claude Opus 4.8 API

Complete native API capabilities — adaptive thinking, Effort, task budget, and prompt caching are all passed through
Stable direct connection in China — no need to set up your own proxy or use overseas servers
Unified billing and usage dashboard — shares the same set of keys as other models, with centralized cost management
Free switching between models — Fable 5 for difficult tasks, Opus 4.8 for daily work, and switch to Sonnet 5 for high traffic

API

API integration

Model IDUse this value as the model in inference requests

claude-opus-4-8

API KeyBearer token used to authenticate inference requests

Manage API keys

Base URLOpenAI compatible · /chat/completions

https://api.atalk-ai.com/v2/

provider OptionalSelects a service channel; omit it and the system picks the default

"provider": { "channel": "direct" }

claude-opus-4-8 usage examples

SeaWhale AI is compatible with the OpenAI API protocol, so you can call it with the OpenAI SDK or plain HTTP requests. Streaming is enabled by default.

About the provider parameter (optional, a SeaWhale AI extension): most models are served over several channels that differ slightly in price and reliability. Add a provider field to the request body to pick one; omit it and the system selects the default channel — normal calls are unaffected.

provider is not part of the official OpenAI protocol — it is a SeaWhale AI extension that only takes effect on this platform. The OpenAI SDK allows custom fields like this to pass through; see the examples below.

Value	Channel	Best for
`direct`	Direct	The official upstream link, for native behavior and the full context window
`stable`	Preferred	Balanced availability and speed — a good default for production traffic
`economical`	Economy	Cost first, well suited to batch processing and price-sensitive workloads

Available channels and their prices are listed under "Pricing" above (channels vary by model). Additional notes:

Syntax: "provider": { "channel": "direct" }.
If the requested channel is not enabled for that model, the request automatically falls back to the default channel and returns normally — it does not error.
With the official SDKs: in Python pass it via extra_body; in Node.js put it directly on the request object and it passes through. In TypeScript projects, add a // @ts-expect-error line to skip the type check.

cURLPythonNode.js

curl https://api.atalk-ai.com/v2/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <API_KEY>" \
  -d '{
    "model": "claude-opus-4-8",
    "messages": [
      {"role": "system", "content": "You are a helpful assistant."},
      {"role": "user", "content": "Hello!"}
    ],
    "provider": { "channel": "direct" },
    "stream": true
  }'
# provider is optional — remove this line to use the default channel

from openai import OpenAI

client = OpenAI(
    base_url="https://api.atalk-ai.com/v2",
    api_key="<API_KEY>",
)

stream = client.chat.completions.create(
    model="claude-opus-4-8",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Hello!"},
    ],
    stream=True,
    # Optional: pick a service channel; omit to use the default
    extra_body={"provider": {"channel": "direct"}},
)

for chunk in stream:
    if chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="", flush=True)

import OpenAI from 'openai'

const client = new OpenAI({
  baseURL: 'https://api.atalk-ai.com/v2',
  apiKey: '<API_KEY>',
})

const stream = await client.chat.completions.create({
  model: 'claude-opus-4-8',
  messages: [
    { role: 'system', content: 'You are a helpful assistant.' },
    { role: 'user', content: 'Hello!' },
  ],
  stream: true,
  // Optional: pick a service channel; omit to use the default
  // @ts-expect-error provider is a SeaWhale AI extension, not in the OpenAI SDK types
  provider: { channel: 'direct' },
})

for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content ?? '')
}