Anthropic’s Claude 4.5 family has set a new bar for AI in 2025, with Claude Opus 4.5 launching on November 24 as the “best model in the world for coding, agents, and computer use.” But its sibling, Claude Sonnet 4.5, offers near-frontier smarts at a fraction of the cost and latency. If you’re choosing between raw power and practical efficiency—whether for dev workflows, agentic apps, or research—this comparison has you covered.
We’ve analyzed benchmarks, real-world tests, pricing, and user feedback to break down the differences. Opus 4.5 edges out in high-stakes tasks like complex refactors, while Sonnet 4.5 shines for everyday speed. By the end, you’ll know which to pick (spoiler: Sonnet for most users).
Overview: What Are Claude Opus 4.5 and Sonnet 4.5?
Both models are part of Anthropic’s Claude 4.5 lineup, trained with constitutional AI for safety and reliability. They share a 200K token context window, multimodal capabilities (text + images), and support for extended thinking with tools like web search or code execution. Released in late 2025, they build on Claude 3.5 with better planning, fewer hallucinations, and agentic prowess.
- Claude Sonnet 4.5: The balanced workhorse—fast, affordable, and capable for most tasks. Ideal for interactive apps, quick coding, and high-volume use. It’s available on free tiers and powers tools like Claude Code for seamless dev integration.
- Claude Opus 4.5: The premium powerhouse—optimized for maximum intelligence on tough problems. Excels in sustained, multi-hour workflows like autonomous agents or deep codebases. It’s slower but more token-efficient on complex jobs.
In short: Sonnet is your reliable daily driver; Opus is the turbocharged specialist.
Head-to-Head: Key Differences in Performance and Features
We compared them across benchmarks, speed, coding, agents, and more. Opus pulls ahead on raw capability, but Sonnet closes the gap impressively—often within 3-5% on key metrics—while being 40-60% faster and cheaper.
Benchmark Breakdown
Opus dominates in coding and agentic tests, but Sonnet holds its own for general intelligence.
| Benchmark | Opus 4.5 | Sonnet 4.5 | Winner | Notes |
|---|---|---|---|---|
| SWE-bench Verified (Coding) | 80.9% | 77.2% | Opus | Opus resolves real GitHub issues with fewer iterations; Sonnet is close for daily fixes. |
| Terminal-bench (Agent Tasks) | 63.1% | 60.2% | Opus | Opus in Claude Code leads for terminal automation; Sonnet faster for quick scripts. |
| GPQA Diamond (Reasoning) | 74.9% | 70.0% | Opus | Opus better on novel problems; Sonnet sufficient for 90% of queries. |
| MMMLU (Multimodal) | 87.4% | 85.4% | Opus | Both handle images well; Opus edges in nuanced analysis. |
| Vending-Bench 2 (Long-Horizon Planning) | $4,967 | $3,850 | Opus | Opus 23% better at strategic simulations; Sonnet cost-effective for lighter planning. |
| WeirdML (Edge Cases) | 63.7% | 47.7% | Opus | Huge Opus lead on unusual ML tasks. |
Speed & Efficiency: Sonnet generates ~2-3x faster (low latency for chats/tools), while Opus uses 19% fewer tokens overall on complex tasks—balancing cost for pros.
Features Comparison
Both support parallel tool use, memory files, and “thinking summaries” to condense reasoning. But:
- Coding: Opus produces “surgical” refactors with elegant architecture; Sonnet is exploratory but pragmatic—great for vibe-coding prototypes.
- Agents & Planning: Opus excels in long-horizon tasks (e.g., 7-hour refactors); Sonnet handles multi-step agents efficiently without overkill.
- Multimodal & Tools: Tied—both analyze images, run code, and browse. Opus better at file memory for sustained work.
- Reliability: Opus 65% less prone to shortcuts; both self-correct hallucinations well.
Use Cases: When to Choose Opus vs Sonnet
- Pick Sonnet 4.5 If: You’re building interactive apps, need quick iterations, or scale affordably. Perfect for: Daily dev (code reviews, prototypes), chatbots, content generation, or education. It’s the “sweet spot” for 80% of users.
- Pick Opus 4.5 If: You tackle high-stakes complexity like enterprise refactors, scientific sims, or autonomous agents. Ideal for: Frontier R&D, long-running workflows, or precision coding where first-try accuracy matters.
Real-world example: In a blog app build, Opus created more maintainable code with fewer parts; Sonnet was faster but needed tweaks.
Pricing and Accessibility
| Model | Input ($$ /MTok) | Output ( $$/MTok) | Free Tier? | Plans |
|---|---|---|---|---|
| Sonnet 4.5 | $3 | $15 | Yes (limited) | Pro ($20/mo): Unlimited; API scalable |
| Opus 4.5 | $5 | $25 | No (Pro+ only) | Pro ($20/mo): Access; Team ($30/user/mo): Collab |
Opus is 66% pricier but more token-efficient on hard tasks—net ~50% cost hike. Both via claude.ai, API, Bedrock, or Vertex AI. Sonnet’s free access democratizes it.
User Feedback: What Builders Are Saying
Feedback is glowing for both, but Opus wins raves for “trustworthy” depth, while Sonnet earns love for speed.
- On X: “Opus 4.5 in Claude Code is RIDICULOUSLY GOOD for agents—63.1% on Terminal Bench.” Another: “Sonnet 4.5 closes the gap to Opus at a fraction of the price—pragmatic sweet spot.”
- Reddit/Forums: Devs note Opus’s “surgical fixes” vs. Sonnet’s “exploratory” style; one benchmark solver hit 95% with Opus on CORE-Bench.
- Real Tests: In app builds, Opus auto-created tools like salary calculators; Sonnet felt “light and fast” post-Opus trials. Gripes: Opus’s cost “murders bank balances” for casual use.
Overall sentiment: Opus for pros (4.9/5); Sonnet for all (4.7/5).
Pros and Cons: Quick Verdict
Sonnet 4.5
- Pros: Blazing speed, low cost, accessible; near-Opus performance for most tasks.
- Cons: Slightly less accurate on edge cases.
Opus 4.5
- Pros: Unrivaled coding/agents, token efficiency on complexity; “senior engineer” reliability.
- Cons: Higher latency/cost; overkill for basics.
Conclusion: Sonnet for Speed, Opus for Supremacy
In 2025’s AI arms race, Claude Sonnet 4.5 is the smart default—efficient and capable for 90% of workflows. Upgrade to Opus 4.5 only if you need that extra edge in coding marathons or agentic innovation. Start with Sonnet on claude.ai; test Opus via Pro for high-impact projects.
Which are you using? Drop thoughts below. For more, check our Opus 4.5 Review or Best AI Coding Tools.
Frequently Asked Questions
Opus 4.5 is the smarter model — it wins almost every head-to-head benchmark (SWE-bench 80.9% vs 77.2%, Terminal-bench 63.1% vs 60.2%, GPQA Diamond 74.9% vs 70%). The gap is noticeable on complex refactors, long-horizon planning, and edge-case reasoning.
No. Opus 4.5 is exclusive to Pro ($20/mo) and higher plans. Sonnet 4.5 is available on the free tier (with daily limits) and fully unlimited on Pro.
Opus 4.5. It creates more coherent architecture, better folder structure, and fewer bugs in one shot. Sonnet is fine for prototypes but often needs more manual cleanup.