What Is Claude Opus 4.5 | 76% Token Reduction Compared to Sonnet 4.5 Explained
Claude Opus 4.5 is Anthropic's flagship language model released in November 2025. It delivers three breakthroughs at once: 76% token reduction compared to Sonnet 4.5, world-leading SWE-bench scores, and pricing at one-third of its predecessor. This guide covers everything from the API model ID and how to choose the Effort parameter, to getting started on Claude.ai, Bedrock, Vertex AI, and Foundry — in the order you need to move to production as quickly as possible.
Opus 4.5 delivers Opus-grade performance at $5 input / $25 output — Sonnet-level pricing — achieving roughly 67% cost reduction compared to Opus 4.1. The long-standing price barrier to using Opus in production has finally been lifted.
The key to implementation is choosing the right Effort setting: at medium Effort, it matches Sonnet 4.5 accuracy while using 76% fewer tokens. Rather than always defaulting to high, the right approach is to assign low, medium, or high based on task cost and SLA requirements.
The API model ID is claude-opus-4-5-20251101, available on GA day across Claude.ai, the API, Bedrock, Vertex AI, and Microsoft Foundry. Combining prompt caching and batch inference can reduce effective costs even further.
目次 (10)
- What Is Claude Opus 4.5 — The Latest Flagship Released in November 2025
- What Changed from Opus 4.1 — A Revolution in Price and Efficiency
- Benchmark Performance — World-Leading Scores on SWE-bench Verified
- Pricing — A Major Reduction to $5 Input / $25 Output
- The Effort Parameter — Tune Accuracy and Cost Across Low, Medium, and High
- Key Platforms — Claude / API / AWS / Google Cloud / Azure
- Enterprise Case Studies — Palo Alto Networks, Replit, and TELUS
- Safety and Alignment — The Most Robust Release in Anthropic's History
- Positioning Against Opus 4.7 / 4.8 — Why Choose Opus 4.5 in 2026
- Summary — When to Choose Opus 4.5
What Is Claude Opus 4.5 — The Latest Flagship Released in November 2025
Claude Opus 4.5 is a flagship language model released by Anthropic on November 24, 2025. Its API model ID is claude-opus-4-5-20251101, with a context window of 200K tokens. It claims to be "world-class" in three domains — coding, autonomous tasks, and computer use — and represents the generation that finally tackled the longstanding problem of Opus models being too expensive for everyday use.
According to the official announcement, Opus 4.5 set the highest score on SWE-bench Verified, leads in 7 of 8 languages on SWE-bench Multilingual, shows significant improvement on BrowseComp-Plus (autonomous search), and achieved 29% improvement over Sonnet 4.5 on Vending-Bench (long-horizon decision-making) — updating the previous generation across the board on enterprise-oriented benchmarks. Anthropic itself describes it as "the most robustly aligned model we have ever released," also highlighting improvements in safety and prompt injection resistance.
Source: Introducing Claude Opus 4.5 (Anthropic)
What Changed from Opus 4.1 — A Revolution in Price and Efficiency
The most talked-about aspect of Opus 4.5 is not raw performance gains, but pricing strategy. According to Anthropic's announcement on Vertex AI, Opus 4.5 is offered at roughly one-third the cost of the previous-generation Opus 4.1. Specifically, while Opus 4.1 was priced at $15 input / $75 output per million tokens, Opus 4.5 comes in at $5 input / $25 output — meaning Sonnet-level pricing now carries Opus-level performance.
Efficiency has improved as well, not just price. At medium Effort, it matches Sonnet 4.5's top score in accuracy while achieving 76% fewer output tokens. At high Effort, it outperforms Sonnet 4.5 by 4.3 points while using 48% fewer output tokens. The longstanding concern — "Opus is accurate but wastes tokens, making production deployment hard to justify" — has finally been structurally resolved in this generation.
Source: Claude Opus 4.5 on Vertex AI (Google Cloud Blog)
Benchmark Performance — World-Leading Scores on SWE-bench Verified
The central selling point of Opus 4.5 is that it surpassed frontier models in coding ability. Key scores include:
- SWE-bench Verified (a coding benchmark that has AI automatically fix real GitHub issues): achieved the highest score at launch
- SWE-bench Multilingual (same code-fixing benchmark across multilingual repositories): leads in 7 of 8 languages
- Aider Polyglot (measures practical code editing ability across multiple programming languages): 10.6-point improvement over Sonnet 4.5
- BrowseComp-Plus (measures ability to autonomously search the web and synthesize answers): significant improvement on autonomous information retrieval tasks
- Vending-Bench (measures consistency of decision-making by running a vending machine business over time): 29% improvement over Sonnet 4.5 in long-horizon decision-making
It is particularly strong on multi-step, long-duration tasks. Anthropic has stated that "performance remains consistent throughout a 30-minute autonomous coding session." Also noteworthy is the meta-evaluation result: "it reaches peak performance through self-improvement in just 4 iterations — other models couldn't reach it even in 10."
Pricing — A Major Reduction to $5 Input / $25 Output
The official pricing is as follows (per million tokens, via direct API):
| Item | Price |
|---|---|
| Input tokens | $5 |
| Output tokens | $25 |
| Cache write | Additional charge on top of input price |
| Prompt cache read | Significant discount (up to 1-hour TTL on Vertex AI) |
Effective costs can be further reduced by combining prompt caching and batch inference across Vertex AI, Amazon Bedrock, and Microsoft Foundry. Vertex AI also offers a global endpoint and provisioned throughput, making it easy to balance cost and availability for enterprise workloads with predictable traffic.
The Effort Parameter — Tune Accuracy and Cost Across Low, Medium, and High
One of the most notable additions widely available in Opus 4.5 is the Effort parameter. It offers three levels — low, medium, and high — to control how deeply the model reasons, allowing the caller to adjust the tradeoff between reasoning depth and token consumption.
- Low: Prioritizes low latency. Suitable for chat interfaces and classification tasks requiring immediate response.
- Medium: Balanced. Ideal for everyday tasks, document generation, and code review.
- High: Maximizes accuracy. For long coding sessions, complex research tasks, and benchmark evaluations.
Benchmark results are published per Effort setting, and it is notable that medium Effort often reaches accuracy equal to or better than Sonnet 4.5 at its highest Effort. The right approach for the Opus 4.5 generation is not "always use high Effort," but rather to calculate the appropriate Effort level from the task's SLA and per-unit cost.
Key Platforms — Claude / API / AWS / Google Cloud / Azure
Opus 4.5 was available on the following platforms from launch day:
- Claude.ai (web / mobile app): Available to all Pro / Max / Team / Enterprise plans
- Anthropic API: Call directly with
claude-opus-4-5-20251101 - Amazon Bedrock: GA in major regions
- Google Cloud Vertex AI: GA, activate via Model Garden / Marketplace
- Microsoft Foundry (formerly Azure AI Foundry): GA, available via Foundry Models catalog
Vertex AI in particular offers full-stack integration with Agent Development Kit (ADK), Agent2Agent (A2A) protocol, and Agent Engine, making it easy for companies already on Google Cloud to adopt as a managed service.
Sources: Introducing Claude Opus 4.5 in Microsoft Foundry / Claude Opus 4.5 on Vertex AI
Enterprise Case Studies — Palo Alto Networks, Replit, and TELUS
The following are representative enterprise cases introduced in the official blog. A key distinction from the previous generation is that Opus 4.5 is being used in production, not just experimentation.
- Palo Alto Networks: Adopted Opus 4.5 in their in-house development automation platform, confirming a 20–30% improvement in code generation speed
- Replit: Updated the backend of "Replit Agent" (web app development from natural language) to Opus 4.5
- TELUS: Built the customer-facing AI platform "Fuel iX," improving decision-making quality in complex customer contexts
- Augment Code: Adopted as the core model for their AI coding assistant
Opus 4.5 is expanding into areas such as financial analysis (integrating regulatory documents, market reports, and internal data), cybersecurity (correlating logs, vulnerability databases, and threat intelligence), and office tasks (creating spreadsheets, slides, and documents) — domains that previously required Sonnet-level models due to their high token consumption.
Safety and Alignment — The Most Robust Release in Anthropic's History
Anthropic positions Opus 4.5 as "the most robustly aligned model we have ever released," claiming significant progress especially in prompt injection resistance. A System Card (November 2025 edition) was published alongside the release, covering ASL evaluations based on the Responsible Scaling Policy (RSP), risk assessments for autonomous tasks, and results from third-party evaluators.
On the Google Cloud side, managed safety mechanisms such as Vertex AI's Model Armor (prompt injection and tool contamination defenses) and AI Protection integration in Security Command Center can be combined with Opus 4.5. For enterprise deployments, designing a two-layer approach — "model-level safety + platform-level defense" — is becoming the standard pattern.
Source: Claude Opus 4.5 System Card (PDF)
Positioning Against Opus 4.7 / 4.8 — Why Choose Opus 4.5 in 2026
As of 2026, Anthropic's latest flagship is Claude Opus 4.8 (announced May 28, 2026, API model ID claude-opus-4-8), which expanded the default context window to 1M tokens. Its immediate predecessor is Claude Opus 4.7. While Opus 4.8 is the top candidate if you want the latest, there are still clear reasons to pin and stay on Opus 4.5.
- Balance of cost and stability: 4.7 / 4.8 introduced some changes in prompt behavior and context defaults along with new features; teams running existing pipelines may practically choose to stay on 4.5
- Fixed API model ID: Pinning
claude-opus-4-5-20251101ensures reproducibility of behavior in long-tail workflows - GA track record on Vertex AI / Bedrock / Foundry: After six months since release, 4.5 has a solid GA track record across all three major cloud providers, with operational know-how widely available
- Pricing: 4.5, 4.7, and 4.8 are in a similar price range (4.8 is priced on par with 4.7), and assuming prompt caching, 4.5 can be structured to have a lower read cost per token in some configurations
The practical split is: new projects or workloads needing 1M context → Opus 4.8; stable production environments where you want to lock existing behavior → Opus 4.5.
Sources: Introducing Claude Opus 4.8 (Anthropic) / Introducing Claude Opus 4.7 (Anthropic)
Summary — When to Choose Opus 4.5
Claude Opus 4.5 is the generation that answered the industry's longstanding challenge: "Opus-grade accuracy at Sonnet-grade pricing." It is the top candidate for production deployment of coding, long-horizon tasks, and enterprise autonomous processing. On the other hand, for straightforward chat responses or lightweight classification, Sonnet 4.5 / Haiku 4.5 offer better cost efficiency — so the key to leveraging Claude in 2026 is designing which layer to use Opus 4.5 at, in combination with the Effort parameter.
