Compare models
Claude Sonnet 5.5 vs Gemini 3.8 Flash
| Spec | Claude Sonnet 5.5 | Gemini 3.8 Flash |
|---|---|---|
| Developer | Anthropic | Google DeepMind |
| Released | September 28, 2026 | September 2, 2026 |
| Status | Current | Current |
| Inputs | Text, Images | Text, Images, Audio, Video |
| Context window | 1M tokens | 1M tokens |
| Input price / 1M tokens | $2 | $0.75 |
| Output price / 1M tokens | $10 | $3.75 |
| Open weights | No | No |
| Access | Claude apps, Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry | Gemini API, Vertex AI, Gemini app |
Claude Sonnet 5.5 in brief
Claude Sonnet 5.5 specs and pricing: Anthropic's September 2026 mid-tier model at $2/$10 per million tokens with a 1M-token context, compared with GPT-6.1 Sol and Gemini.
- Fast responses with strong reasoning
- 1M-token context and 128K output
- Same list price as GPT-6.1 Sol
Gemini 3.8 Flash in brief
Gemini 3.8 Flash specs and pricing: Google's September 2026 model with a ~1M-token multimodal context at $0.75/$3.75 per million tokens (introductory), and comparisons.
- Low introductory price
- About 1M-token multimodal context
- Strong for long-horizon software engineering and agents
Which should you choose?
Choose Claude Sonnet 5.5 if you need: customer-facing assistants that need speed; high-volume coding and data tasks; agents where latency matters.
Choose Gemini 3.8 Flash if you need: cost-sensitive production apps; multimodal document and video analysis; high-volume agent workflows.
For most teams the best test is your own workload: run the same 20–50 real prompts through both models and compare quality, speed and cost. Benchmarks published by labs use different settings and rarely match everyday use.
Frequently asked questions
Which is cheaper, Claude Sonnet 5.5 or Gemini 3.8 Flash?
At list prices, Gemini 3.8 Flash costs $0.75 per million input tokens and $3.75 per million output tokens, compared with $2 and $10 for Claude Sonnet 5.5. Discounts for caching and batch processing can change the real cost.
Which has a bigger context window?
Gemini 3.8 Flash can take in up to 1M tokens at once, versus 1M for Claude Sonnet 5.5.
Are Claude Sonnet 5.5 and Gemini 3.8 Flash open source?
Claude Sonnet 5.5 is closed: you use it through its developer’s apps or API. Gemini 3.8 Flash is closed: you use it through its developer’s apps or API.
Which model is newer?
Claude Sonnet 5.5 was released later, on September 28, 2026.
Sources
- Claude models overview — Anthropic
- Gemini API pricing — Google
- Gemini API models — Google
Written by
Luka Kušec · Editor
Editor of SI.info. Writes about Super Intelligence, technology policy and the people building frontier models.