Breaking

Anthropic Releases Claude Sonnet 5, Adds It to Agent Arena

June 30, 2026 at 15:13 EDT

Foundation Models
AI Agents

Anthropic released its new model "Claude Sonnet 5" on June 30, 2026, calling it its "most agentic Sonnet model." The same day, it became available on Agent Arena, an evaluation platform based on real-world usage.

June 30, 2026 · Anthropic

Claude Sonnet 5: Opus-Class Agents at Sonnet Prices

Anthropic's most agentic Sonnet yet runs multi-step, long-horizon workflows — planning, browsing, and using a terminal autonomously — at speeds and costs once reserved for larger Opus models. Available immediately.

~Opus 4.8

Performance close to Opus 4.8, at a lower price

1M+

Agent Arena sessions on launch day

Default

For Free & Pro on claude.ai from day one

Token Pricing — per Million Tokens

Introductory rates run through Aug 31; standard rates from Sep 1.

INPUT

intro

standard

OUTPUT

$10

intro

$15

standard

New tokenizer raises token counts ~1.0–1.35×, but introductory pricing is designed to be cost-neutral.

An End-to-End Agentic Loop

Plan
multi-step task

→

Use Tools
browser · terminal · files

→

Verify
fix & confirm

EARLY PARTNER IMPRESSIONS

Sustained coding & debugging across complex software tasks
Completed Salesforce update + notification end-to-end
Bug investigation: repro → fix → verify in a single pass
Strong price-to-performance value

CAVEATS & SAFETY

Full autonomy can still need human judgment or approval
Risks such as tool hallucination remain
Cybersecurity guardrails enabled by default
Cyber-task capability held well below Opus 4.8

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