Gemini 3.1 Pro preview vs Xai Grok 4.1 Fast Reasoning

Name: Xai Grok 4.1 Fast Reasoning
Brand: Google Vertex AI
Price: 0.200000 USD

Gemini 3.1 Pro preview vs Xai Grok 4.1 Fast Reasoning: Xai Grok 4.1 Fast Reasoning is cheaper by 96% on average. Gemini 3.1 Pro preview from Google Vertex AI (1,048,576-token context, reasoning, tool calls) vs. Xai Grok 4.1 Fast Reasoning from Google Vertex AI (2,000,000-token context, reasoning, tool calls). Use Agent Command Center to A/B both in shadow mode and pick the winner per workload.

Side-by-side cost

Live workload comparison

Same workload run through both models. The cheaper one is highlighted.

Input tokens / request3,000

02,000,000

Output tokens / request400

0200,000

Requests / day5,000

01,000,000

Gemini 3.1 Pro preview

Google Vertex AI

$1,644/mo

Input $2.00/M · Output $12.00/M

Xai Grok 4.1 Fast ReasoningCheaper

Google Vertex AI

$122/mo

Input $0.200/M · Output $0.500/M

At this workload, Xai Grok 4.1 Fast Reasoning is 93% cheaper than Gemini 3.1 Pro preview — a savings of $1,522/month ($18,263/year).

Production recipe — Agent Command Center

strategy: cost-optimized
primary:
  model: xai-grok-4-1-fast-reasoning
  provider: vertex-ai
fallback:
  model: gemini-3-1-pro-preview
  provider: vertex-ai
shadow: { sample_rate: 0.05 }   # mirror 5% of traffic to compare quality live

Get started free →Routing docs ↗

	Gemini 3.1 Pro preview Google Vertex AI	Xai Grok 4.1 Fast Reasoning Google Vertex AI
Input price	$2.00/M	$0.200/M
Output price	$12.00/M	$0.500/M
Context window	1,048,576	2,000,000
Max output	65,536	2,000,000
Function calling	✓	✓
Vision	✓	✓
Audio input	✓	—
Reasoning	✓	✓
Prompt caching	✓	—
Structured output	✓	✓
Pricing verified	May 12, 2026	May 12, 2026