Anthropic SDK

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TypeScript

npm install @anthropic-ai/sdk

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
	apiKey: null,
	authToken: process.env.PHASEO_API_KEY,
	baseURL: "https://api.phaseo.app",
});

const message = await client.messages.create({
	model: "anthropic/claude-sonnet-4.5",
	max_tokens: 512,
	messages: [{ role: "user", content: "Reply with only: ok" }],
});

console.log(message.content);

​

Python

pip install anthropic

import os
from anthropic import Anthropic

client = Anthropic(
    auth_token=os.environ["PHASEO_API_KEY"],
    base_url="https://api.phaseo.app",
)

message = client.messages.create(
    model="anthropic/claude-sonnet-4.5",
    max_tokens=512,
    messages=[{"role": "user", "content": "Reply with only: ok"}],
)

print(message.content)

​

Notes

• Use the root host https://api.phaseo.app; Anthropic clients append /v1/messages.
• Pass the key as authToken (auth_token in Python), which sends Authorization: Bearer on every SDK version. Phaseo doesn’t accept x-api-key, which apiKey sends before @anthropic-ai/sdk 1.0 and anthropic 2.0.
• apiKey: null stops older TypeScript SDKs from also sending your ANTHROPIC_API_KEY. Python SDKs before 0.98 send it whenever it is set, so upgrade or remove it from environments that call Phaseo.
• Use Anthropic Messages for endpoint details.
• Native Anthropic tool shapes can work where Phaseo supports them, but cross-provider server tools should use Phaseo tool names.
• If a workflow depends on streamed tool loops, test it before production rollout because Anthropic-compatible clients are stricter about tool event ordering.

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Related

• Claude Code
• Anthropic Messages
• Tool Calling