Pick the Right Claude Model and Stop Overpaying
Which model for which task — a practical guide.
Anthropic's Claude comes in three tiers — Haiku, Sonnet, and Opus — each making a different tradeoff between speed, capability, and cost. Picking the wrong model for a task either wastes money (Opus on a simple classification job) or produces underwhelming results (Haiku on a complex architecture decision). Here's how to get it right.
Claude Sonnet and Claude Opus are Anthropic's two main model tiers. Sonnet is the balanced choice, offering strong performance at lower cost and higher speed. Opus is the reasoning-heavy model, best for complex analysis, nuanced writing, and tasks requiring deep strategic thinking. Most developers default to Sonnet and escalate to Opus for complex tasks.
The mental model: start with Sonnet
The most practical rule: default to Sonnet.It handles the vast majority of tasks well — coding, writing, analysis, summarization — at a speed and cost that works for most use cases. Go down to Haiku when you need to scale a high-frequency task cheaply. Go up to Opus when the task genuinely demands maximum reasoning and Sonnet's output isn't good enough.
The mistake most developers make is defaulting to Opus for everything because it feels safer. In practice, Sonnet handles 80-90% of tasks at the same quality, and you pay significantly more for Opus when it isn't warranted.
Model Deep Dives
What each model is actually good at
- Fastest response times in the Claude family
- Lowest input/output cost per token
- Ideal for classification, routing, and extraction tasks
- Customer-facing chatbots with high concurrency
- Summarization of large batches of documents
- Autocomplete and inline suggestion use cases
- Less nuanced reasoning on complex problems
- Shorter, simpler responses by nature
- Not ideal for multi-step agentic tasks
When you need AI at scale and latency or cost is the constraint, not depth of reasoning.
- Excellent at complex coding tasks and multi-file changes
- Strong reasoning and analysis — significantly better than Haiku
- Reliable at following long, detailed instructions
- Good for most content generation and writing tasks
- Competitive speed — meaningfully faster than Opus
- 200K context window handles large codebases
- Not as strong as Opus on the hardest open-ended reasoning
- Occasional gaps in nuance on the most ambiguous tasks
The default choice for almost everything. Use Sonnet unless you have a specific reason to go up or down.
- Best performance on complex, open-ended reasoning
- Strongest at multi-step planning and strategy
- Handles the most ambiguous, nuanced instructions reliably
- Deep document analysis and synthesis across 200K tokens
- Security audits, architecture reviews, legal analysis
- Content that requires strong voice and judgment
- Significantly slower than Sonnet — perceivable latency
- Higher token cost — expensive for high-volume pipelines
- Overkill for most day-to-day tasks
When the task is hard enough that Sonnet's quality isn't sufficient and the stakes justify slower, more expensive processing.
Quick Reference
Model by task type
Model routing in agent systems
In multi-agent architectures, you often want different models at different levels. A common pattern: use Opus as the orchestrator (high reasoning, plans the full task), Sonnet for specialist subagents (executes subtasks, writes code, reads docs), and Haiku for lightweight operations (classify inputs, route tasks, extract structured data).
This tiered approach gives you Opus-quality planning without paying Opus rates for every low-complexity step in the pipeline. In production agent systems, cost optimization at the model selection layer often matters as much as the prompting itself.
Frequently Asked Questions
Which Claude model should I use?
Default to Claude Sonnet for most tasks. Escalate to Opus for complex reasoning, nuanced writing, strategic analysis, and tasks requiring deep thinking. Sonnet is faster and cheaper; Opus is more capable for hard problems.
Is Claude Opus worth the extra cost?
Opus is worth it for tasks where accuracy and depth matter more than speed: complex debugging, architectural decisions, legal analysis, and creative writing that requires nuanced voice matching.
What is the difference between Sonnet and Haiku?
Sonnet is the balanced, general-purpose model. Haiku is the fastest and cheapest model, best for simple tasks like classification, extraction, and formatting. Use Haiku for high-volume, low-complexity tasks.
Can I switch between Claude models mid-conversation?
Yes. In Claude.ai you can change models between messages. In the API, you specify the model per request. A common pattern is starting with Sonnet for exploration, then switching to Opus for the final critical output.
What is Claude Sonnet best at?
Claude Sonnet is the best general-purpose Claude model for everyday tasks: drafting emails, summarizing documents, writing code, answering questions, and data analysis. It balances speed, cost, and quality for the widest range of use cases.
Learn to use every Claude model well
Track 4 covers model selection, API configuration, and agent routing end-to-end.