Model comparison
Claude Sonnet 5.5 vs Gemini 3.1 Pro
Claude
GeminiCompare published specifications, vendor API list prices and measured Borg performance. Both models are included in Borg.
Claude Sonnet 5.5
Gemini 3.1 Pro
Included in Borg
At a glance
| Specification | Claude Sonnet 5.5 | Gemini 3.1 Pro |
|---|---|---|
| Provider | Anthropic | |
| Release | 2026-09-28 Vendor source | 2026-02-19 Vendor source |
| Context | 1,000,000 tokens Vendor source | 1,048,576 tokens Vendor source |
| Modalities | Input: text, image; output: text | Input: text, image, video, audio, pdf; output: text |
| Reasoning / thinking modes | Yes / Not published | Yes / Not published |
| Open weights | No | No |
| Vendor API list price / 1M tokens | $2 input / $10 output | $2 input / $12 output Rates for prompts of at most 200,000 tokens; longer prompts cost more. |
| Borg | Included in Borg subscription | Included in Borg subscription |
Anthropic
GoogleMeasured on Borg
Metrics are not directly comparable to vendor benchmark claims. Models served different requests; this is observed gateway traffic, not a controlled head-to-head test.
Time to first token (gateway proxy)
No published measurement for this model.
Output tokens per second (whole turn)
No published measurement for this model.
| Metric | Claude Sonnet 5.5 | Gemini 3.1 Pro |
|---|---|---|
| Time to first token (gateway proxy) p50 | 2640 ms (35971 samples) | Not published |
| Tokens per second (end to end) p50 | 76.7 output tokens per second (86888 samples) | Not published |
| Request success rate | Not published | Not published |
| Coding bench pass rate | Not published | Not published |
Measurement window, samples and methodology
The fleet reference is the median of published model medians, not a request-weighted result. Prompt lengths, reasoning settings and traffic differ between models.
Claude Sonnet 5.5: Measured on Borg: SearchAtlas AI Gateway production request logs. 30-day window ending 2026-10-08; 94296 requests. Minimum 100 samples per published request metric.
Gemini 3.1 Pro: Measured on Borg: SearchAtlas AI Gateway production request logs. 30-day window ending 2026-10-08; 278 requests. Minimum 100 samples per published request metric.
Completion speed covers the whole turn including queueing and reasoning time; it is not a streaming tokens-per-second figure.
- Time to first token (gateway proxy): time until the first streamed response event reaches the gateway; our closest available measure of time to first token
- Tokens per second (end to end): tokens per second, end to end: provider-reported output tokens divided by the whole turn's elapsed time, including queueing and reasoning; not a streaming per-token rate
How to choose
Claude Sonnet 5.5 is listed for well-scoped bug fixes and code reviews, whereas Gemini 3.1 Pro is listed for complex software engineering. Choosing between Claude Sonnet 5.5 and Gemini 3.1 Pro requires checking published specifications against observed Borg traffic for your workflow.
Key differences
| Spec | Claude Sonnet 5.5 | Gemini 3.1 Pro |
|---|---|---|
| Context window | 1,000,000 tokens Vendor source | 1,048,576 tokens Vendor source Larger context |
| Reasoning modes | Yes / Not published | Yes / Not published |
| Release date | 2026-09-28 Vendor source | 2026-02-19 Vendor source |
| API price input / 1M | 2 | 2 Rates for prompts of at most 200,000 tokens; longer prompts cost more. |
| API price output / 1M | 10 Lower listed rate | 12 Rates for prompts of at most 200,000 tokens; longer prompts cost more. |
| Time to first token (gateway proxy) | 2640 ms (35971 samples) | Not published |
| Output tokens per second (whole turn) | 76.7 output tokens/s (whole turn) (86888 samples) | Not published |
| Request success | Not published | Not published |
| Coding bench | Not published | Not published |
FAQ
How do Claude Sonnet 5.5 and Gemini 3.1 Pro compare for coding?
Claude Sonnet 5.5 has a Borg coding benchmark of not published; Gemini 3.1 Pro has not published. The Claude Sonnet 5.5–Gemini 3.1 Pro coding comparison cannot establish an overall winner from this small test alone.
How quickly do Claude Sonnet 5.5 and Gemini 3.1 Pro start responding on Borg?
Borg median first response for Claude Sonnet 5.5 is 2,640 ms; for Gemini 3.1 Pro it is not published. The Claude Sonnet 5.5–Gemini 3.1 Pro gateway medians are observations, not guaranteed latency for individual requests.
What are the API prices for Claude Sonnet 5.5 and Gemini 3.1 Pro?
The listed API rate for Claude Sonnet 5.5 is $2 input / $10 output per 1M tokens; for Gemini 3.1 Pro it is $2 input / $12 output per 1M tokens. Neither Claude Sonnet 5.5 nor Gemini 3.1 Pro has its Borg subscription charge represented by those provider API rates. Claude Sonnet 5.5 vendor source · Gemini 3.1 Pro vendor source