Claude

Claude (by Anthropic) is OpenAI's main competitor. It is famous for its large context window (200k+), low hallucination rates, and "Artifacts" UI.

When to Use

• Coding: Claude 3.5 Sonnet is widely considered the best coding model in 2025.

• Long Context: Analyzing massive PDFs or codebases.

• Safety: Enterprise-grade safety guardrails.

Core Concepts

Models

• Opus: The smartest, largest model.

• Sonnet: The sweet spot. Fast and incredibly capable.

• Haiku: Fast and cheap.

Artifacts

A UI feature (now an API pattern) where the model generates standalone content (React components, SVGs) in a side window.

Computer Use

Claude can interact with a computer GUI (moving mouse, clicking) via API.

Best Practices (2025)

Do:

• Use Sonnet for Dev: It beats GPT-4o in many coding benchmarks.

• Use XML Tags: Claude loves <instructions> and <context> tags in prompts.

• Prefill Responses: Guide Claude by prefilling the {"role": "assistant", "content": "{"} to force JSON.

Don't:

• Don't ignore System Prompts: Claude relies heavily on strong system instructions.

References

• Anthropic Documentation