Anthropic Claude Sonnet 5 vs Sonnet 4.6 vs Opus 4.8: Agentic Coding Benchmarks, API Pricing, and Cost-Performance Tradeoffs Compared

Benchmark

Anthropic team published a benchmark table comparing Sonnet 5, Sonnet 4.6, and Opus 4.8. Sonnet 5 beats its predecessor in every tested category. It closes much of the gap to Opus 4.8.

On agentic coding (SWE-bench Pro), Sonnet 5 scores 63.2%. Sonnet 4.6 scored 58.1%. Opus 4.8 still leads at 69.2%.

On computer use (OSWorld-Verified), Sonnet 5 posts 81.2% against Sonnet 4.6’s 78.5%. On Terminal-Bench 2.1, it reaches 80.4% versus 67.0%.

On Humanity’s Last Exam with tools, Sonnet 5 hits 57.4%. That nearly matches Opus 4.8 at 57.9%.

There is one place where Sonnet 5 edges ahead. On the GDPval-AA v2 knowledge-work benchmark, it scores 1,618 against Opus 4.8’s 1,615.

Effort Levels: Where the Real Tradeoff Lives

The cost-performance story is the most important part for developers. Sonnet 5 is a strict improvement over Sonnet 4.6 across every effort level. The clearest value appears at low and medium effort.

At those levels, Sonnet 5 delivers quality that earlier Sonnet pricing could not buy. Opus 4.8 remains the accuracy leader at the top of the range.

A practical routing policy follows from this. Send most agentic coding, tool use, and knowledge work to Sonnet 5. Reserve Opus 4.8 for accuracy-critical tasks. Keep Haiku 4.5 for high-volume, latency-sensitive calls.

Use Cases: Where Sonnet 5 Fits

Early access partners described concrete workflows. Their reports map to common engineering jobs.

• Multi-step software engineering: One tester asked Sonnet 5 to investigate a bug. It wrote a reproducing test, implemented the fix, then confirmed the bug returned without the change. It did this in a single pass.
• Brownfield debugging: Another partner ran it on hard pull requests. The model traced failures to their root causes. It shipped durable fixes rather than symptom patches.
• Business automation: Zapier handed it a two-part job. It updated Salesforce account tiers, then sent a launch email to enterprise contacts. It finished the task end to end.
• Computer-use agents: Pace runs insurance workflows like submission intake and loss runs. Its agents act on the operational systems teams already use.
• Data exploration: ClickHouse agents query live data and produce insights on the fly. Faster reasoning means faster time-to-insight for analysts.

Comparison Table

Sonnet 5’s introductory pricing runs through August 31, 2026. Standard pricing of $3/$15 begins after that date. Standard prompt caching (cache reads at 0.1x input) and the 50% Batch API discount also apply. Per token, Sonnet 5 undercuts GPT-5.5 and Gemini 3.1 Pro, but costs more than Gemini 3.5 Flash. Anthropic lists a 1M-token context window for Sonnet 5 in its launch post. It does not publish context figures for the other models here.

Coding Example: Calling Sonnet 5

The API call mirrors any other Anthropic model. You change the model string to claude-sonnet-5.

import anthropic

client = anthropic.Anthropic()  # reads ANTHROPIC_API_KEY

message = client.messages.create(
    model="claude-sonnet-5",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Find the race condition in worker.py and ship a tested fix."}
    ],
)

print(message.content[0].text)

Strengths and Weaknesses

Strengths:

• Improves on Sonnet 4.6 in every benchmark category Anthropic tested
• Near-Opus 4.8 quality on several evaluations, at lower per-token prices
• Edges Opus 4.8 on the GDPval-AA v2 knowledge-work benchmark
• Lower hallucination, sycophancy, and undesirable-behavior rates than Sonnet 4.6
• Drop-in API change: you only swap the model string

Weaknesses:

• Opus 4.8 still wins on the hardest accuracy-critical tasks
• At xhigh effort, cost can exceed Opus 4.8 at similar quality
• The new tokenizer can raise token counts by up to 1.35 times
• Cyber capability is intentionally low; use Opus for sanctioned cyber work
• Standard pricing of $3/$15 arrives after August 31, 2026

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