Claude Sonnet 5.5 is Anthropic's mid-tier LLM in the Claude 5.5 family — optimized for speed, intelligence balance, and cost efficiency with a 1M token context window.
curl https://api.venice.ai/api/v1/chat/completions \
-H "Authorization: Bearer $VENICE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-sonnet-5-5",
"messages": [{ "role": "user", "content": "Explain quantum tunneling simply." }]
}'Overview
Claude Sonnet 5.5 is Anthropic's next-generation mid-tier language model, succeeding Sonnet 5. Released on September 28, 2026 as the second model in the Claude 5.5 family, it delivers improved reasoning, code generation, and efficiency over its predecessor while maintaining a 1M token context window and fast response times.
On Venice, Claude Sonnet 5.5 runs under an anonymized privacy tier — your prompts are never stored, profiled, or reused. You get full access to its reasoning, vision, and tool capabilities without sacrificing privacy, and without any personal data tied to your sessions. This is permissionless, uncensored AI with zero retention.
Agent quickstart
The API is OpenAI-compatible: change the base URL and the model id and existing client code works unchanged.
curl https://api.venice.ai/api/v1/chat/completions \
-H "Authorization: Bearer $VENICE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-sonnet-5-5",
"stream": true,
"messages": [{ "role": "user", "content": "Draft the release note." }]
}'curl https://api.venice.ai/api/v1/chat/completions \
-H "Authorization: Bearer $VENICE_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "claude-sonnet-5-5",
"messages": [{ "role": "user", "content": "Find the rate limits." }],
"tools": [{
"type": "function",
"function": {
"name": "search_docs",
"description": "Search the API documentation.",
"parameters": {
"type": "object",
"properties": { "query": { "type": "string" } },
"required": ["query"]
}
}
}],
"tool_choice": "auto"
}'import os
from openai import OpenAI
client = OpenAI(
api_key=os.environ["VENICE_API_KEY"],
base_url="https://api.venice.ai/api/v1",
)
resp = client.chat.completions.create(
model="claude-sonnet-5-5",
messages=[{"role": "user", "content": "Build without permission."}],
)
print(resp.choices[0].message.content)Specifications
Assessment
Use cases
Prompting
Use explicit mode selection (e.g., 'use reasoning mode') to activate advanced thinking.
Attach multiple images and refer to them numerically ('see image 1') for clarity.
Include URLs in prompts when you want up-to-date information — web search is enabled.
Structure requests for JSON output with a clear schema description to leverage structured response support.
Break down complex tasks into steps — the model handles multi-step reasoning well.
For code tasks, specify the language and environment to improve accuracy.
Alternatives
| Model | Best for | Context | Open weights | Price (Venice) |
|---|---|---|---|---|
| Claude Sonnet 5.5 | Speed-intelligence balance | 1M tokens | No | $3.75 in · $18.75 out / 1M |
| Claude Fable 5.1 | Highest reasoning performance | 1M tokens | No | $12 in · $60 out / 1M |
| Claude Opus 5 | High-end reasoning & coding | 1M tokens | No | $6 in · $30 out / 1M |
| Claude Sonnet 4.6 | Legacy balance | 1M tokens | No | $3.60 in · $18 out / 1M |
| DeepSeek V4.1 Flash | Budget high-speed use | 1M tokens | Yes | $0.38 in · $1.50 out / 1M |
Choose Claude Sonnet 5.5 when you need a reliable balance of speed, intelligence, and cost for daily professional work — better than budget models on complex tasks, more affordable than Opus or Fable.
Pricing
Billed per token on Venice: $3.75 per 1M input tokens and $18.75 per 1M output tokens.
New Venice accounts include a free daily allowance and 500 welcome credits — no credit card required.
Getting a key
Create a key in API settings. Nothing else is required to start.
Export it as VENICE_API_KEY so the snippets above run unedited.
Point an existing OpenAI client at https://api.venice.ai/api/v1. The scheme is part of the value: an OpenAI client given a bare host does not resolve it.
Pass claude-sonnet-5-5 as the model and send the request.
FAQ
Claude Sonnet 5.5 is Anthropic's mid-tier AI model, released on September 28, 2026 as part of the Claude 5.5 family. It features a 1M token context window, enhanced reasoning, code generation, and multimodal capabilities, designed for a balance of speed and intelligence.
Anthropic released Claude Sonnet 5.5 on September 28, 2026, the second model in its Claude 5.5 family. It is available on Venice now, with requests proxied anonymously and no prompts stored.
No. Claude Sonnet 5.5 is a proprietary model from Anthropic. It is not open source, does not have open weights, and cannot be self-hosted. Access is via API with usage-based pricing.
On Venice, Claude Sonnet 5.5 is priced at $3.75 per million input tokens and $18.75 per million output tokens. Cached input is billed at $0.38 per million, reducing costs for repeated queries.
Yes. The model supports multiple image inputs in JPEG, PNG, WebP, and PDF formats, with a maximum file size of 10MB per image. This enables document parsing, visual analysis, and multimodal reasoning.
Yes. The model supports function calling, structured JSON output, web search, and reasoning modes, enabling integration into automated workflows, agents, and data-driven applications.
Claude Opus 5 is more powerful for complex reasoning and coding tasks, but slower and more expensive. Sonnet 5.5 offers a better balance for everyday use, offering strong performance at half the cost. Use Opus for critical agent workflows, Sonnet for daily productivity.
One key, free to start, no credit card.