Released: January 2026
Context Window: 200,000 tokens (~150,000 words)
Architecture: Dense transformer with Constitutional AI training
Position: Historical Opus reference; no longer the current flagship lane
Claude Opus 4.5 was the January 2026 Opus reference point for this site. Do not read this page as the current premium-model ranking. As of July 2026, use Opus 4.8 as the practical Claude premium baseline, keep restored Fable 5 as a guarded 2x-cost escalation to revisit only after route, retention, and safeguard checks, and compare GPT-5.5 when OpenAI tooling, cached input, or long-context economics fit better.
Who this is for: Readers checking historical Opus 4.5 pricing/benchmark context, or maintaining older pages that still link to Opus 4.5.
The bottom line: Keep Opus 4.5 facts historical. For current buying decisions, start with the Premium LLM Comparison and the Fable 5 decision guide.
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) |
Historical comparison: Opus 4.5’s 80.9% SWE-bench was a strong January 2026 coding signal against then-current Kimi k2.5 and Gemini 3 Flash rows. Do not use that line as a current “best model” claim; current premium routing should compare Sonnet 5, Opus 4.8, restored-but-guarded Fable 5, and GPT-5.5 against live provider docs and your own tasks.
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) is about $10 at pure API list pricing before tool overhead, caching effects, and subscription-message accounting. Subscriptions can still be better for interactive Claude Code or claude.ai work, but do not treat plan messages as direct API-token equivalents.
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:
- Free coding alternatives — Current limited-time Zen models, API trials, and local lanes; verify the live roster
- 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
Treat Opus 4.5 as historical when:
- Maintaining older content that references the January 2026 Opus launch.
- Comparing why a workflow moved from Opus 4.5 to Opus 4.8, GPT-5.5, or Fable 5 after account access and compliance checks pass.
- Checking the $5/$25 Opus pricing anchor that still applies to current Opus 4.8 in Claude API docs.
Consider alternatives when:
- Budget matters — test GLM-5.2 or Kimi K2.7 Code on the same repository task
- High-context workflows — compare current 1M-context lanes against the exact workload
- Need cached pricing — GPT-5.5 offers cached-input pricing on supported lanes
- Exploratory work — Start with free tiers
See Premium Tier LLM Comparison for the current Fable, Opus, Sonnet, and GPT-5.5 escalation ladder.
Limitations
Historical cache context: Use current Claude pricing documentation for cache-write and cache-hit rates instead of carrying forward an old comparison row.
Context size: 200K tokens vs current 1M-class Claude Fable/Opus/Sonnet docs and GPT-5.5’s separate short-context and long-context pricing lanes.
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. Lower-cost models need task-level evaluation; token price does not establish a percentage of Opus capability.
Related links
Free Access Guides:
- Free Frontier Stack — Kilo Code and OpenCode setup
- Kimi K3 — newest Kimi flagship and 1M-context eval lane
- Kimi K2.7 Code — cheaper Kimi coding API lane
- GLM-5.2 — current long-context value lane to test
Paid Options:
- Premium Tier Comparison — Fable, Opus, Sonnet, and GPT-5.5
- Claude Fable 5 decision guide — Restricted access, guardrails, and 2x Opus pricing
- Smart Spend Guide — Subscription vs API break-even
Terms:
- Claude Max Terms — Enterprise details
- Claude Pro Terms — Consumer limitations
Last updated: July 2, 2026. Opus 4.5 details remain historical; current premium routing should compare Sonnet 5, Opus 4.8, restored-but-guarded Fable 5, and GPT-5.5 against live provider docs.