Claude Sonnet 5.5 is Anthropic's faster, lower-cost mid-tier model for routine production work. Use it over Opus 5.5 for well-scoped web tasks, bug fixes, code review, and fast iteration where speed and volume matter more than sustained judgment. Anthropic released Opus 5.5 on September 22, 2026, then Sonnet 5.5 on September 28, 2026, according to Anthropic. That sequence makes Sonnet the practical default for everyday front-end, WordPress, Drupal, and marketing-site work, with Opus reserved for harder calls.
Table of Contents
- Which routine web work fits Sonnet best?
- Why do price and speed change the choice?
- How capable is Sonnet on code tasks?
- When should you still choose Opus?
- How should teams set the default?
Which routine web work fits Sonnet best?
Sonnet 5.5 suits defined tickets with clear acceptance criteria. Examples include fixing layout bugs, updating templates, scoping a small feature, and keeping edits easy to review. Anthropic positions Sonnet 5.5 as strongest at well-scoped everyday tasks, bug fixes, and polished documents, slides and spreadsheets, as described in the Sonnet 5.5 announcement.
For development, Anthropic says it gets up to speed on codebases and keeps changes reviewable. Use it for repeatable site maintenance and content-driven updates. Save broader architecture and ambiguous rebuilds for Opus.
Why do price and speed change the choice?
High-volume web work rewards lower cost per run. Sonnet 5.5 costs $2 per million input tokens, $10 output and $0.20 cache reads, half Opus 5.5's $4/$20 rates, according to Anthropic in the Sonnet 5.5 announcement. Output is also 30%+ faster than Sonnet 5, making it Anthropic's fastest Sonnet to date.
Opus 5.5 also improved output speed over Opus 5, but Sonnet remains the faster iteration choice for daily queues. For agencies, that means cheaper checks across many pages, themes, and client sites. Run Sonnet first for drafts, lint-level fixes, and review passes.
How capable is Sonnet on code tasks?
Sonnet 5.5 scored 70.6% on Terminal-Bench 4.0, versus 10.3% for Sonnet 5 and 66.4% for Opus 5.5, according to Anthropic. It also scored two points below Opus 5.5 on GDPval-AA real-world work, as reported in the Sonnet 5.5 announcement. That pattern means strong handling of terminal-centered coding steps, with slightly weaker performance on broader work outcomes.
Treat benchmark leads as task-specific, not a general replacement claim. For web teams, the fit is feature branches, regression fixes, and structured reviews. Keep human review for behavior changes, performance claims, and accessibility.
When should you still choose Opus?
Choose Opus 5.5 for complex, open-ended work requiring sustained judgment. Anthropic cautions it remains clearly stronger there, so Sonnet's Terminal-Bench lead does not cover the hardest web tasks.
A useful split looks like this: Anthropic reported Opus 5.5 cut load times across every page of a test web app in 39 of 40 tries without altering behavior. Use that class of sensitive optimization as an Opus job, then hand routine follow-ups back to Sonnet.
- Sonnet 5.5: bug fixes, small features, code review, template updates, document and spreadsheet polish
- Opus 5.5: unclear requirements, risky refactors, cross-page performance work, careful behavior preservation
How should teams set the default?
Make Sonnet 5.5 the default model ID for repeated jobs and fast loops. Developers can call it as `claude-sonnet-5-5` on the Claude API, Claude.ai, AWS, Google Cloud and Microsoft Foundry.
Route tickets by scope at intake: defined input and output to Sonnet, ambiguous goals to Opus. Track token use, review time, and rework rate for one month before changing the split.
