Claude 3.5 Sonnet was Anthropic’s mid-2024 flagship model — the release that significantly closed the gap between Claude and GPT-4o and established Claude as a serious competitor for daily professional use. Here’s what it was, how it compared at launch, and where it fits in the current model lineup.
claude-sonnet-4-6). If you’re building something new, use the current Sonnet model. If you’re maintaining a system built on Claude 3.5, check Anthropic’s deprecation schedule for transition timing.
Claude 3.5 Sonnet: What It Was
Claude 3.5 Sonnet launched in June 2024 and was Anthropic’s strongest model at the time — outperforming Claude 3 Opus on most benchmarks while being significantly faster and cheaper. This made it an unusual release: the mid-tier model in a new generation beating the top-tier model from the previous generation. It set the pattern for how Anthropic structures model generations.
At launch, Claude 3.5 Sonnet scored at the top of industry benchmarks on graduate-level reasoning, coding, and mathematics. It was the first Claude model to support computer use — the ability to see and interact with computer interfaces — in beta.
Model Generations: Where 3.5 Sonnet Fits
| Model | Generation | Status |
|---|---|---|
| Claude 3 Opus / Sonnet / Haiku | Claude 3 (early 2024) | Deprecated / legacy |
| Claude 3.5 Sonnet / Haiku | Claude 3.5 (mid 2024) | Superseded |
| Claude Sonnet 4.6 | Claude 4.x (current) | ✅ Current production default |
| Claude Opus 4.6 | Claude 4.x (current) | ✅ Current flagship |
Why Claude 3.5 Sonnet Was a Landmark Release
Before 3.5 Sonnet, the conventional wisdom was that Claude Opus was the model you reached for on serious tasks, accepting higher cost and slower speed. Claude 3.5 Sonnet changed that calculus — it was fast enough to use as a daily driver and capable enough to replace Opus on most tasks. The cost savings were substantial for anyone running high-volume API workloads.
The release also marked Claude’s first serious push into coding benchmarks — it scored highly on SWE-bench, a test of real-world software engineering tasks, which attracted significant developer attention and migration from GPT-4o.
Claude 3.5 Sonnet vs. Current Models
The current Claude Sonnet 4.6 builds on what Claude 3.5 Sonnet established, with improvements across reasoning, coding, instruction-following, and context handling. If you were a Claude 3.5 Sonnet user, the upgrade path is straightforward — switch the model string and expect better performance across most tasks.
For current model strings and specs, see Claude API Model Strings — Complete Reference. For a comparison of current Sonnet vs. Opus, see Claude Opus vs Sonnet: Which Model Should You Use?
Frequently Asked Questions
Is Claude 3.5 Sonnet still available?
Claude 3.5 Sonnet has been superseded by Claude Sonnet 4.6. Anthropic maintains older models for a period after new releases but eventually deprecates them. Check Anthropic’s model documentation for current availability and any deprecation notices for Claude 3.5 Sonnet API strings.
What was the Claude 3.5 Sonnet API model string?
The Claude 3.5 Sonnet model strings were claude-3-5-sonnet-20240620 and the later version claude-3-5-sonnet-20241022. If you have production systems using these strings, verify their current availability in Anthropic’s model documentation and plan migration to current model strings.
Should I upgrade from Claude 3.5 Sonnet to the current Sonnet?
Yes. Claude Sonnet 4.6 outperforms Claude 3.5 Sonnet across most tasks. Migration is typically straightforward — update the model string in your application and test your core use cases. The current model string is claude-sonnet-4-6.
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