Claude Opus vs Sonnet vs Haiku: Choosing the Right Model for Each Task

The Claude Model Family in 2026

Anthropic's Claude model family consists of three tiers: Opus (the most capable), Sonnet (balanced capability and cost), and Haiku (fastest and most affordable). Each tier exists because different tasks have fundamentally different requirements for intelligence, speed, and cost.

Choosing the right model per task is not just an optimization; it is a requirement for building economically viable AI products. A system that uses Opus for everything will work well but cost 10-30x more than one that routes intelligently across the model family.

Model Specifications Comparison

Specification	Claude Opus 4	Claude Sonnet 4	Claude Haiku 4
Context window	200K tokens	200K tokens	200K tokens
Max output	32K tokens	16K tokens	8K tokens
Input cost (per MTok)	$15.00	$3.00	$0.80
Output cost (per MTok)	$75.00	$15.00	$4.00
Speed (tokens/sec)	~60-80	~80-120	~150-200+
Extended thinking	Yes	Yes	Yes
Tool use	Yes	Yes	Yes
Vision	Yes	Yes	Yes

Note: Pricing and specifications reflect approximate values as of early 2026. Check Anthropic's pricing page for current figures.

When to Use Each Model

Claude Opus: The Expert Reasoner

Opus excels at tasks requiring deep reasoning, nuanced judgment, and complex multi-step analysis. Use it when getting the answer wrong has significant consequences.

Best suited for:

• Complex code generation requiring architectural decisions
• Legal document analysis with nuanced interpretation
• Mathematical proofs and formal reasoning
• Multi-step research synthesis from large document sets
• High-stakes decision support where accuracy is paramount
• Creative writing requiring sustained coherence over long outputs

Real-world example: Financial risk assessment

# Opus for complex financial analysis
response = client.messages.create(
    model="claude-opus-4-20250514",
    max_tokens=8096,
    thinking={"type": "enabled", "budget_tokens": 10000},
    messages=[{
        "role": "user",
        "content": f"""Analyze this company's 10-K filing and assess:
1. Liquidity risk based on current ratio trends
2. Revenue concentration risk across customer segments
3. Regulatory exposure in each operating jurisdiction
4. Comparison with industry peers on key financial ratios

Filing data:
{filing_data}

Peer comparison data:
{peer_data}"""
    }]
)

Claude Sonnet: The Workhorse

Sonnet handles the vast majority of production tasks. It offers strong reasoning, good coding ability, and reliable instruction following at a fraction of Opus cost.

Best suited for:

• Standard code generation, refactoring, and bug fixes
• Content generation (articles, summaries, documentation)
• Data extraction and transformation
• Conversational AI with tool use
• Multi-step agent workflows
• Code review and analysis
• Most business-logic tasks

Real-world example: Agentic coding assistant

# Sonnet for the core agent loop
response = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=8096,
    system="You are a coding assistant. Use tools to read, search, and edit code.",
    tools=coding_tools,
    messages=messages
)

Claude Haiku: The Speed Specialist

Haiku is purpose-built for tasks where speed and cost matter more than deep reasoning. It is remarkably capable for its size and is the right choice for any task that a competent junior developer or analyst could handle.

Best suited for:

• Classification and routing (intent detection, categorization)
• Data extraction from structured or semi-structured text
• Simple question answering from provided context
• Input validation and preprocessing
• Summarization of short-to-medium texts
• Translation and format conversion
• High-volume, low-complexity tasks

Real-world example: Request classification and routing

# Haiku for fast classification
response = client.messages.create(
    model="claude-haiku-4-20250514",
    max_tokens=128,
    messages=[{
        "role": "user",
        "content": f"""Classify this support request into one category.
Categories: billing, technical, account, general

Request: {user_message}

Respond with only the category name."""
    }]
)

Cost Analysis: The Case for Model Routing

Consider a customer support agent that handles 100,000 requests per day. Each request involves classification, retrieval, response generation, and quality checking.

Without model routing (all Sonnet):

Step	Calls/day	Avg tokens (in+out)	Cost/day
Classification	100K	500 in + 50 out	$225
Retrieval query	100K	800 in + 200 out	$540
Response generation	100K	2000 in + 500 out	$1,350
Quality check	100K	1500 in + 100 out	$600
Total			$2,715/day

With model routing (mixed):

Step	Model	Calls/day	Cost/day
Classification	Haiku	100K	$60
Retrieval query	Haiku	100K	$144
Response generation	Sonnet	100K	$1,350
Quality check	Haiku	100K	$160
Total			$1,714/day

Savings: 37% ($1,001/day or $365K/year) with zero quality degradation on the routed steps.

Implementing a Model Router

from enum import Enum

class TaskComplexity(Enum):
    LOW = "low"
    MEDIUM = "medium"
    HIGH = "high"
    CRITICAL = "critical"

MODEL_MAP = {
    TaskComplexity.LOW: "claude-haiku-4-20250514",
    TaskComplexity.MEDIUM: "claude-sonnet-4-20250514",
    TaskComplexity.HIGH: "claude-sonnet-4-20250514",
    TaskComplexity.CRITICAL: "claude-opus-4-20250514",
}

def route_model(task_type: str, context: dict) -> str:
    """Select the appropriate model based on task characteristics."""

    # Classification, extraction, validation -> Haiku
    if task_type in ("classify", "extract", "validate", "summarize_short"):
        return MODEL_MAP[TaskComplexity.LOW]

    # Standard generation, analysis, coding -> Sonnet
    if task_type in ("generate", "analyze", "code", "converse"):
        # Upgrade to Opus for very long or complex inputs
        input_length = context.get("input_tokens", 0)
        if input_length > 50000:
            return MODEL_MAP[TaskComplexity.HIGH]
        return MODEL_MAP[TaskComplexity.MEDIUM]

    # Critical decisions, legal, financial -> Opus
    if task_type in ("legal_review", "financial_analysis", "safety_critical"):
        return MODEL_MAP[TaskComplexity.CRITICAL]

    # Default to Sonnet
    return MODEL_MAP[TaskComplexity.MEDIUM]

Cascade Pattern: Start Cheap, Escalate When Needed

An advanced strategy is to start with a cheaper model and only escalate to a more capable one if the output does not meet quality thresholds.

async def cascade_generate(prompt: str, quality_threshold: float = 0.8) -> dict:
    """Try Haiku first, escalate to Sonnet, then Opus if needed."""
    models = [
        "claude-haiku-4-20250514",
        "claude-sonnet-4-20250514",
        "claude-opus-4-20250514",
    ]

    for model in models:
        response = await async_client.messages.create(
            model=model,
            max_tokens=4096,
            messages=[{"role": "user", "content": prompt}]
        )

        output = response.content[0].text
        quality_score = await evaluate_quality(output, prompt)

        if quality_score >= quality_threshold:
            return {
                "output": output,
                "model_used": model,
                "quality_score": quality_score,
                "escalated": model != models[0]
            }

    # Return best effort from Opus
    return {
        "output": output,
        "model_used": models[-1],
        "quality_score": quality_score,
        "escalated": True
    }

In practice, the cascade pattern handles 60-70% of requests with Haiku, 25-30% with Sonnet, and only 3-5% with Opus, resulting in average per-request costs that are 50-60% lower than using Sonnet for everything.

Summary

Model selection is a first-class engineering decision. Opus provides the highest reasoning quality for complex, high-stakes tasks. Sonnet handles the majority of production workloads with a strong balance of capability and cost. Haiku delivers exceptional speed and value for classification, extraction, and high-volume low-complexity tasks. The biggest cost optimization in any AI system is not prompt engineering or caching; it is routing each task to the cheapest model that can handle it reliably.