Model
claude-opus-4.8
Claude Opus 4.8, released in May 2026 just 41 days after Opus 4.7, was an interim upgrade to the generally available line at unchanged pricing, which Anthropic said was more likely to flag uncertainty in its own work. It introduced Dynamic Workflows, a research-preview feature for coordinating hundreds of parallel subagents on codebase-scale migrations, and later served as the fallback model when the more capable Fable 5 was pulled offline.
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- Models & capabilities 7
- Safety & alignment 2
- Benchmarks & progress 1
- Security & misuse 1
- Government & policy 1
Anthropic launches Claude Opus 5
Anthropic said the model came close to its flagship Fable 5 on several benchmarks at half the price, while costing the same as its Opus 4.8 predecessor.
Models & capabilities
Claude Opus 5 system card published
Anthropic reports Opus 5 shows no new concerning alignment properties and assesses overall alignment risk as very low, alongside a model-welfare discussion.
Safety & alignment · Models & capabilities
METR proposes 'expenditure horizon' measure
The metric prices AI agents against human effort in dollars per unit of progress; on a public speed-optimisation task, frontier agents matched roughly $3,300 of skilled human labour.
Benchmarks & progress
SpaceXAI releases Grok 4.5
Built on a 1.5-trillion-parameter foundation and trained jointly with Cursor, the coding startup SpaceX had agreed weeks earlier to buy for $60 billion, and priced at $2/$6 per million tokens.
Models & capabilities
Anthropic launches Claude Sonnet 5
Priced at $3/$15 per million input/output tokens against Opus 4.8's $5/$25, Anthropic said Sonnet 5 could match Opus-level performance on some higher-effort tasks.
Models & capabilities
Anthropic launches Claude Tag for Slack
The tool runs as a shared, persistent agent per channel rather than a private per-user chat; Anthropic said its own product team already generated 65% of its code through an internal version.
Models & capabilities
Commerce Department orders Anthropic to take Fable 5 and Mythos 5 offline worldwide
Amazon researchers had reported a technique bypassing Fable 5's safeguards; Anthropic disputed the order's rationale and said less capable models showed the same weakness.
Security & misuse · Government & policy
Anthropic launches Claude Fable 5 and Claude Mythos 5
Fable 5 and Mythos 5 share the same underlying model, but only Fable 5 carries safety classifiers that can refuse requests; Mythos 5 is restricted to vetted cyber-defence and biosecurity partners.
Models & capabilities · Safety & alignment
Anthropic releases Claude Opus 4.8
The upgrade arrived just 41 days after Opus 4.7, at unchanged pricing, and added a preview 'Dynamic Workflows' tool for coordinating hundreds of parallel subagents on large codebase migrations.
Models & capabilities