GPT-5.1 vs Grok Code Fast 1
GPT-5.1 is the better default for high‑stakes, long‑context or multilingual tasks thanks to wins in faithfulness, long-context and strategic analysis. Grok Code Fast 1 is the practical pick for cost‑sensitive, agentic coding workflows where its agentic planning score (5) and visible reasoning traces matter.
openai
GPT-5.1
Benchmark Scores
External Benchmarks
Pricing
Input
$1.25/MTok
Output
$10.00/MTok
modelpicker.net
xai
Grok Code Fast 1
Benchmark Scores
External Benchmarks
Pricing
Input
$0.200/MTok
Output
$1.50/MTok
modelpicker.net
Benchmark Analysis
Across our 12-test suite GPT-5.1 wins 7 tests, Grok Code Fast 1 wins 1, and 4 tests tie. Where GPT-5.1 wins: faithfulness (5 vs 4) — GPT-5.1 is tied for 1st among 55 models on faithfulness in our rankings; long context (5 vs 4) — GPT-5.1 is tied for 1st for retrieval at 30K+ tokens while Grok ranks 38 of 55; strategic analysis (5 vs 3) — GPT-5.1 is tied for 1st on nuanced tradeoff reasoning; constrained rewriting (4 vs 3), creative problem solving (4 vs 3), persona consistency (5 vs 4), and multilingual (5 vs 4) — GPT-5.1 sits at or near top tiers in these tasks. Grok Code Fast 1 wins agentic planning (5 vs 4) and is tied for 1st for that capability in our rankings, which maps to stronger goal decomposition and failure recovery in agentic coding scenarios. Ties: structured output (4/4), tool calling (4/4), classification (4/4), safety calibration (2/2) — on these common engineering tasks both models perform equivalently in our tests. Supplementary external results: GPT-5.1 scores 68 on SWE-bench Verified and 88.6 on AIME 2025 (Epoch AI), placing it 7th on both external suites per the payload; Grok has no external SWE/AIME scores in the payload.
Pricing Analysis
Payload prices: GPT-5.1 input $1.25 / mTok and output $10 / mTok; Grok Code Fast 1 input $0.20 / mTok and output $1.50 / mTok. Using the per‑mTok prices as listed and treating 1 mTok = 1,000 tokens, a 50/50 split of input/output tokens costs per month: for 1M tokens GPT-5.1 ≈ $5,625 vs Grok ≈ $850; for 10M tokens GPT-5.1 ≈ $56,250 vs Grok ≈ $8,500; for 100M tokens GPT-5.1 ≈ $562,500 vs Grok ≈ $85,000. The output cost ratio (10 vs 1.5) is 6.6667x (payload priceRatio), so large‑volume deployments and startups should care: Grok reduces operational spend by multiple‑times versus GPT-5.1, while GPT-5.1 charges a premium for higher scores on several quality metrics.
Real-World Cost Comparison
Bottom Line
Choose GPT-5.1 if you need best-in-class faithfulness, long‑context retrieval, strategic analysis, multilingual output or constrained rewriting for high‑value content and can absorb higher compute costs. Choose Grok Code Fast 1 if you prioritize cost-efficiency at scale, agentic planning for coding agents, or want visible reasoning traces (quirk: uses_reasoning_tokens) to debug or steer generated code—it delivers similar structured output, tool calling, classification and safety calibration at a fraction of the price.
How We Test
We test every model against our 12-benchmark suite covering tool calling, agentic planning, creative problem solving, safety calibration, and more. Each test is scored 1–5 by an LLM judge. Read our full methodology.