Anthropic
Claude Opus 5.5
Claude Opus 5.5 is a Anthropic model with 1M context, $4 in / $20 out per million tokens, last verified September 26, 2026. Open weights: no. Public-board scores are linked to the publisher; vendor-only figures stay in the watch-out, not on the board.
Claude Opus 5.5 is Anthropic's default model for agentic coding and knowledge work — Anthropic says it performs near Fable 5.1 on most work at about 40% lower running cost than Opus 5, and it leads the Artificial Analysis Intelligence Index v4.3.2.
Catalog record checked September 26, 2026Individual provider fields may change
| Specification | Claude Opus 5.5 |
|---|---|
| Provider | Anthropic |
| Tier | Frontier |
| Context window | 1M |
| Max output | 128K |
| Input / 1M tokens | $4 |
| Output / 1M tokens | $20 |
| Weights | Closed |
| Parameters | Not disclosed |
| Reasoning levels | adaptive |
| Modalities | text, image |
| API model id | claude-opus-5-5 |
| Released | September 22, 2026 |
Pricing tiers: $4/$20 per MTok, no long-context surcharge. Cache reads $0.20; 5-minute cache writes $5, 1-hour writes $8. Batch $2/$10; Fast mode $8/$40. Batches API allows 300K output with the output-300k-2026-03-24 beta header. Knowledge cutoff Jun 2026; retirement not before 2027-09-22.
Verified evidence
Published benchmark results
Each result keeps its source and measurement date visible. A missing benchmark is not treated as a zero.
| Benchmark | Score | Measured | Source |
|---|---|---|---|
| Artificial Analysis Intelligence Index [max] | 57.6 | 2026-09-26 | Artificial Analysis · View source |
| Humanity's Last Exam [max] | 61.4 | 2026-09-26 | Artificial Analysis Humanity's Last Exam (independent, 2,158 text-only questions) · View source |
| Terminal-Bench 4.0 [max] | 59.6 | 2026-09-26 | Artificial Analysis Terminal-Bench 4.0 (independent AA run, part of Intelligence Index v4.3.2) · View source |
| Terminal-Bench 4.0 [xhigh] | 66.4 | 2026-09-22 | Anthropic — Claude Opus 5.5 announcement (vendor; conflicts with AA's independent 59.6 — harness difference preserved) · View source |
Best for
- Complex agentic coding
- Enterprise knowledge work
- Default frontier model
Watch out
History
Claude Opus 5.5 timeline
Release and status events for this model that passed two-source verification — dated, sourced, and linked.
- Claude Opus 5.5ReleaseSeptember 22, 2026
Anthropic ships Claude Opus 5.5 at $4/$20 per MTok (cheaper than Opus 5's $5/$25) with a 1M-token context, and its docs now say to start new work with it. It leads the Artificial Analysis Intelligence Index v4.3.2 (57.6) and CursorBench 4.0 (57.8% at Max effort).
Anthropic — Claude Opus 5.5
Source receipts
Catalog figures for this model were checked against the following sources.
- Anthropic — Claude Opus 5.5 (accessed 2026-09-26)
- Anthropic docs — Opus 5.5 overview (1M context, 128K output) (accessed 2026-09-26)
- Anthropic pricing (claude-opus-5-5 $4/$20, cache reads $0.20) (accessed 2026-09-26)
- Artificial Analysis — Intelligence Index v4.3.2 (Opus 5.5 #1) (accessed 2026-09-26)
Common questions
Claude Opus 5.5
Answered from the verified figures on this page rather than general guidance.
How much does Claude Opus 5.5 cost per million tokens?
What is Claude Opus 5.5's context window?
What is Claude Opus 5.5 best for?
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