On May 22, 2025, Anthropic released Claude 4. It includes two models: Sonnet and Opus.
We looked into both models to understand what’s changed and how they hold up for real conversational use cases, especially if you're building or managing agents inside Kaily.
Overall, Claude 4 brings better reasoning, stronger memory, and more natural replies. These changes can impact how well your agents handle complex tasks or long conversations. That said, not every upgrade needs your attention. Here's a quick look at what's different and whether Claude makes sense for your AI agent setup.
The new models in town
Claude 4 comes in two versions.
Claude 4 Sonnet
The efficient model designed for speed and everyday agent tasks. Available for free on Claude.ai and through most integrations.
Claude 4 Opus
The premium model built for complex reasoning and high-stakes applications. Requires a paid subscription and costs more per request.
Here’s what’s new across both models
- Larger input capacity
Claude 4 can take in long documents, chat histories, or product catalogs in one go. This helps if your agents rely on big knowledge sources. - Better at logic and instructions
It handles conditions, branching paths, and layered rules more accurately than before. - Smoother language
Replies feel more natural and easier to read. Good for support, onboarding, and customer-facing flows. - Improved consistency
Claude is less likely to lose track or repeat itself during long or complex tasks.
- Advanced problem-solving
Opus delivers step-by-step analytical reasoning for complex problems, similar to more deliberate thinking processes that break down multi-faceted challenges systematically.
What this means for builders
For most Kaily users, Claude 4 Sonnet will be the practical choice. It handles standard support flows, user onboarding, and guided selling efficiently while keeping costs manageable.
Claude 4 Opus becomes valuable when accuracy and deep reasoning outweigh speed concerns.
When to choose Sonnet:
- Customer support and FAQ handling
- Product onboarding sequences
- Processing standard knowledge bases and help articles
- Multi-step workflows with straightforward logic
When to choose Opus:
- Legal or compliance document review
- Technical specification analysis
- Complex troubleshooting that requires systematic reasoning
- Training on unstructured or noisy conversation data
- High-stakes decisions where errors are costly
Claude 4 vs GPT-4o
If you're using GPT-4o today, you might be wondering whether switching to Claude 4 changes anything. Both models are strong, but they’re optimized for slightly different things.
Claude 4 leans toward context depth and consistency. GPT-4o is faster and slightly more flexible in open-ended tasks. For Kaily, the choice depends on what kind of experience you want your agent to deliver — speed and variety, or stability and tone.
<table>
Area
Claude 4 Sonnet
GPT-4o
Speed
Fast
Faster
Cost
Moderate
Lower (in most tools)
Long inputs
Very good
Also strong
Reasoning
Consistent
Strong, slightly more flexible
Tone
Natural and calm
More varied, sometimes robotic
Multimodal (images, voice)
Not supported
Fully supported
Access and setup
If you're using Kaily, you can choose Claude 4 Sonnet or Opus directly when setting up your agent. Just select your preferred model in the Configuration panel.
Claude 4 is available in two versions:
- Sonnet is free to use on Claude.ai and is available through most integrations.
- Opus is part of Claude Pro, which requires a paid subscription.
Both models can be used with APIs via Anthropic, Amazon Bedrock, and Google Vertex AI.
Final take
Claude 4 is a solid step forward, especially if you're building agents that need to read, reason, or respond with more nuance. But it’s not essential for everyone.
If you’re already using GPT-4o models, there’s no urgent need to switch. If you’re building for depth, tone, or longer inputs, Claude might be the better fit and worth testing.
You can try both Sonnet and Opus inside Kaily today. Let us know what you think. Happy building!
