- Who it helps
- Developers evaluating a model on longer or multi-step tasks.
- Availability
- The September 28 launch page describes availability and effort settings. Account eligibility and provider-specific limits still apply.
What is available
A useful evaluation pairs output quality with the amount of work and review needed. A higher effort setting can change both latency and usage.
A useful first check
Choose a task with an inspectable final artifact and record the effort setting, corrections and total usage. Keep the same acceptance checks across models.
What you can do
- Choose a task with an inspectable final artifact and record the effort setting, corrections and total usage. Keep the same acceptance checks across models.
Where the evidence stops
The release page was read. No inference, benchmark replication or provider billing test was run.
Sources read. The cited pages were read on October 17, 2026 UTC. No external product workflow or model inference was executed.
Sources & further reading
Web · official
Claude Sonnet 5.5 ↗
Read the release description, including effort controls. Task quality and costs depend on the selected workload.
Anthropic · page checked 2026-10-17 · Published 2026-09-28
More sources reviewed (1)
Web · analysis
The Batch, issue 375 ↗
Read the October 16 issue in the browser after web indexing returned stale content. Audited its four news stories and opening letter; background model names were treated as context.
DeepLearning.AI · page checked 2026-10-17
Coverage note: The listed sources establish the scope of this check. A matching original X post and a complete cross-platform comparison were unavailable.
The record over time (1)
Dated source checks and published explanations. An observation date can differ from the original release date.
Claude Sonnet 5.5 is Anthropic’s model release for coding and other substantial work, with controls over reasoning effort.