Claude Opus 5.5

Claude Opus 5.5 is Anthropic’s new Frontier model: as of September 22, 2026, it replaces Opus 5 and is claimed by the manufacturer to achieve Fable-5.1-level performance at 40 percent lower typical workload costs. Adaptive Thinking is active by default and controllable via effort level; the context window holds one million tokens with 128,000 output tokens. The reasoning classifier errors from Opus 5 have been fixed; only the metacognition refusal remains.

Anthropic Version 5.5 Commercial use permitted Dense 1000 K Context 06/2026 $5 / $25 per 1M

Proprietary
Frontier
Anthropic
Text
Vision
Agentic Orchestrator
Long Context
Interactive

Sovereign Risk: TODO TODO

Tool-use profile: 6 assets in detail

Comparison of asset performance (P1/P2/Combined) against the fleet average

Asset performance (radar)

Score Breakdown vs. Fleet Average

Tool-use details

Asset performance, reliability, and runtime profile

Name	P1	P2	Combined
EU License Research	100	60	76
HTTP Fetch & Extract	80	60	70
Tool Failure Handling (404)	80	35	64.3
Web Search & Tool Selection	100	80	91
URL Construction & Fetch	80	80	80
Multilingual Search & Synthesis	100	60	80

CrucibleMark evaluates tool use across 6 independent tests. Click a test name for details.

Reliability

Tool Call Valid: No
Retry: Not required
Hallucination: Detected

Reliability measures how consistently a model actually executes tool calls: Tool Call Valid schema and format accepted, Retry Required successful only after retry, Hallucination Flag fabricated tools or parameters detected. All three green means production-ready.

Runtime profile

Call 1: 2.85; First Request

MCP: 1.21; Protocol Latency

Synthesis: 14.03; Response Generation

Total: 108.54; Sum of All Phases

Token: 8443; Input + Output

Cost: $0; Cost per Run

The runtime profile shows the latency and cost metrics for the model run: Call 1 First Request, MCP Protocol Latency, Synthesis Response Generation, Total sum of all phases, supplemented by Token input and output and Cost cost per run.

Tool-use profile

Claude Opus 5.5 achieves a Combined Score of 76.9 (Good) in the tool-use benchmark: P1 Execution 90, P2 Synthesis 62.5, fleet average 68.2.

Strongest test: Tool Failure Handling (404) (64.3). Weakest test: Web Search & Tool Selection (91). The spread between these two tests is -26.7 points.

Reliability status: Tool Call Valid No, Retry Not required, Hallucination Detected.

This data-driven auto-review is compiled from the available tool-use benchmark data. Once a detailed LLM-generated analysis (GPT-5.4) is available, it will automatically replace this template. The raw data and full methodology are documented in the GitHub project.