Chat with Claude Sonnet 5 for free
Claude Sonnet 5 is Anthropic's balanced everyday model, quick and capable with strong reasoning for the bulk of day-to-day work. Start typing, no sign-up needed.
See how Claude Sonnet 5 thinks
Pick a task and watch a sample answer stream in. Open the same prompt in Chatday when you’re ready.
The bug is in the arrow body: u.id = id assigns instead of compares, so the callback returns the assigned value and .find never matches the way you expect.
Fix it with a strict comparison:
Use === to compare. A single = is assignment, which is why you saw undefined.
What makes Claude Sonnet 5 stand out
Claude Sonnet 5 specifications
| Provider | Anthropic |
| Model family | Claude 5 series |
| Context window | 1,000,000 tokens |
| Max output | 128,000 tokens |
| Modality | Text · Vision · Code |
| Input price | $2 / 1M tokens |
| Output price | $10 / 1M tokens |
| Tool / function calling | Yes |
| Vision | Yes |
| Streaming | Yes |
| Available in Chatday | Free & Pro |
Pricing shown for reference; usage is included in your Chatday plan.
Claude Sonnet 5 vs other top models
| Model | Context | Best at | Input price | In Chatday |
|---|---|---|---|---|
| Claude Sonnet 5 | 1M | Balanced | $2/M | Free |
| Gemini 4 Argon | 1M | Frontier coding | $2/M | Free |
| GPT-6.1 | 1.1M | Agentic coding | $2/M | Free |
| Grok 4.7 | 500K | Agentic coding | $2/M | Free |
Claude Sonnet 5 questions
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Claude Opus 5.5
Claude Opus 5.5 is Anthropic's new flagship for agentic coding and knowledge work, with a 1M-token context and lower prices than Opus 5.
Chat with Claude Sonnet 5 and switch models any time.
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