Released: January 2026
Context Window: 200,000 tokens (~150,000 words)
Architecture: Dense transformer with Constitutional AI training
Position: Anthropic’s flagship reasoning and coding model
Claude Opus 4.5 delivers the industry’s highest verified SWE-bench score at 80.9%. At $5 per million input tokens, it costs 8x more than budget alternatives—but that premium buys the best reasoning quality for complex software engineering and safety-critical applications.
Who this is for: Teams where errors are expensive, researchers needing maximum reasoning depth, and enterprises requiring SOC 2 compliance.
The bottom line: You’re paying 5-8x more for a 4-5 point SWE-bench improvement. Only makes sense when error costs exceed API costs.
Key Capabilities
Extended Thinking Mode
Opus 4.5 can engage deeper reasoning chains for complex problems. When enabled, the model performs more thorough analysis—critical for architectural decisions and safety-critical reasoning. Adds latency but improves accuracy on hard tasks.
Constitutional AI & Safety
Anthropic’s safety training reduces harmful outputs and improves calibration. Less likely to hallucinate on critical tasks, making it the default choice for healthcare, financial compliance, and legal analysis.
Enterprise Trust
SOC 2 Type II certified with HIPAA BAA availability. Zero data retention for enterprise agreements. Available via AWS Bedrock, Google Vertex AI, and Azure AI Foundry.
Benchmarks
| Benchmark | Score | Context |
|---|---|---|
| SWE-bench Verified | 80.9% | Software engineering tasks (source) |
| Context Window | 200K tokens | ~150,000 words (source) |
Comparison: Opus 4.5’s 80.9% SWE-bench leads all models—4.1 points ahead of Kimi k2.5 (76.8%) and 2.9 points ahead of Gemini 3 Flash (78.0%). GPT-5.2 trails at 80.0%.
Note: Anthropic does not publish MMLU or GPQA scores, focusing on software engineering benchmarks.
Pricing
API Pricing
| Usage Type | Price per 1M tokens |
|---|---|
| Input | $5.00 |
| Output | $25.00 |
| Batch (50% discount) | $2.50 input / $12.50 output |
Cost comparison: Opus 4.5 costs 8x more than Kimi k2.5 or Gemini 3 Flash ($3/1M). A 500K output session costs $12.50 vs $1.50 with budget alternatives.
Subscription Plans
| Plan | Monthly Cost | Opus 4.5 Messages | Best For |
|---|---|---|---|
| Pro | $20 | ~100 | Individual developers, light usage |
| Max-5x | $100 | ~500 | Small teams, daily workflows |
| Max-20x | $200 | ~2,000 | Heavy users, enterprise workloads |
Break-even: 100 typical messages (10K input + 2K output each) costs $2,500 at API pricing—making the Pro plan ($20) a 99% savings.
Free Access
Important: Claude Opus 4.5 does not offer a free tier. No trial credits or free API access.
Alternatives to evaluate before subscribing:
- Kimi k2.5 — Free via Kilo Code (1 week) or OpenCode Zen
- Gemini 3 Flash — Free input tokens via Google AI Studio
- Claude Pro trial — $20 first month
If you don’t need that final 3-4% of reasoning performance, start with free alternatives.
When to Choose Opus 4.5
Choose Opus 4.5 when:
- Maximum reasoning quality is critical — That 4% SWE-bench gap matters for safety-critical systems
- Error costs exceed API costs — Healthcare, financial compliance, legal analysis
- Enterprise compliance required — SOC 2, HIPAA BAA, zero data retention
- Already in Claude ecosystem — Using Claude Code or Max plan
- Reputation is on the line — Customer-facing features or published research
Consider alternatives when:
- Budget matters — Kimi k2.5 delivers 95% capability at 1/8th the cost
- High-context workflows — Gemini 3 Flash offers 1M context (5x larger)
- Need cached pricing — GPT-5.2 Pro offers 90% discount on repeated context
- Exploratory work — Start with free tiers
See Premium Tier LLM Comparison for head-to-head analysis with GPT-5.2 Pro.
Limitations
No cached pricing: Unlike GPT-5.2 Pro’s 90% discount on repeated context, Opus 4.5 offers no caching.
Context size: 200K tokens vs Gemini 3 Flash’s 1M (5x larger) and GPT-5.2’s 400K (2x larger).
Rate limits: Entry-tier API keys have conservative TPM limits.
Safety filters: Occasionally over-refuses on edge cases.
Price premium: At $25/1M output, large requests can cost hundreds. Budget alternatives offer 95% capability at 12% the cost.
Related Resources
Free Access Guides:
- Free Frontier Stack — Kilo Code and OpenCode setup
- Kimi k2.5 — 76.8% SWE-bench, free access
- Gemini 3 Flash — 78% SWE-bench, free inputs
Paid Options:
- Premium Tier Comparison — vs GPT-5.2 Pro
- Smart Spend Guide — Subscription vs API break-even
Terms:
- Claude Max Terms — Enterprise details
- Claude Pro Terms — Consumer limitations
Last updated: January 30, 2026. Pricing from Anthropic. Verify before large workloads.