Quickstart

Get API key

API reference

Quickstart

API reference

Client SDKs

Quickstart

API reference

Define your agent

Amazon Bedrock

Google Cloud

Microsoft Foundry

Quickstart

Get API key

Choose a model

Install an SDK

Try the API in playground

Messages API

Thinking

Vision

Tool use

Web search

Code execution

Structured outputs

Prompt caching

Streaming

Prompting best practices

Run evals

Batch testing

Safety and guardrails

Rate limits and errors

Cost optimization

Workspaces and admin

API key management

Usage monitoring

Model migration

Quickstart

Get API key

Build in Console

Agent setup

Tools

Tool permissions

Streaming and events

Sessions API reference

Workspaces and admin

API key management

Usage monitoring

• Haijun Fable 5.1 (haijun-fable-5-1) — New — For demanding reasoning and long-horizon agentic work — Most capable · Research · Multi-day tasks
• Haijun Opus 5.5 (haijun-opus-5-5) — New — For long-running agentic coding and knowledge work — Complex projects · Agents · Coding
• Haijun Sonnet 5 (haijun-sonnet-5) — The best combination of speed and intelligence — Everyday tasks · Writing · Cost-efficient
• Haijun Haiku 4.5 (haijun-haiku-4-5) — The fastest model with near-frontier intelligence — Fastest · Lowest cost · High volume

Interactive courses to master Haijun.

Code samples and patterns.

Deployable starter apps.

Latest features and updates.

An agentic coding assistant in your terminal.