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GPT-5.1-Codex-Mini vs Grok 4.20

Updated October 21, 2026. 16 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-5.1-Codex-Mini Replace Grok 4.20
GPT-5.1-Codex-MiniOpenAI
Coding
No data
Overall
20.4
Output $/M
$2.00
1
Grok 4.20xAI
Coding
33.3
Overall
25.7
Output $/M
$2.50
15
vs boards won of 16 shared

Decision reading

Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; GPT-5.1-Codex-Mini has none, so the two cannot be ranked on coding.

GPT-5.1-Codex-Mini has the edge where output tokens cost 1.3x less, and where the benchmark that matters is Terminal-Bench, where it leads.

Model AGPT-5.1-Codex-MiniOpenAINot benchmarked1 independent benchmarkNo cost per solved taskModel BGrok 4.20xAI33.3/1002 independent benchmarks$0.72 per solved task
Shared results
16
GPT-5.1-Codex-Mini only
6
Grok 4.20 only
38
Like-for-like categories
6 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
GPT-5.1-Codex-Mini not benchmarked, Grok 4.20 33.3 from 2 benchmarks.
Widest category
Agentic work, 30.1 points apart on average over 1 shared benchmark.
Widest single gap
τ²-Bench Telecom: GPT-5.1-Codex-Mini 62.9% against Grok 4.20 93.0%, 30.1 points apart on a 0 to 100 scale.
Output price
GPT-5.1-Codex-Mini $2.00 against Grok 4.20 $2.50 per million output tokens, 1.3x apart.
Context window
GPT-5.1-Codex-Mini takes 400K tokens, Grok 4.20 2M.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryGPT-5.1-Codex-MiniBarsGrok 4.20Ties
Coding11
Intelligence01
Agentic work01
Reasoning02
Web design08
General02
All shared boards115
CodingLike-for-likeSix of these boards feed the Vibe Coding Index11
Coding benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
LMArena WebDev1244Not measuredOnly GPT-5.1-Codex-Mini measured
LiveCodeBench (Vals AI)Not measured84.3%Only Grok 4.20 measured
SWE-bench Verified (Vals AI)Not measured72.2%Only Grok 4.20 measured
Vibe Code Bench (Vals AI)Not measured4.1%Only Grok 4.20 measured
Code migration (Vals AI)Not measured0.3%Only Grok 4.20 measured
Terminal-Bench 2.1 (Vals AI)Not measured44.2%Only Grok 4.20 measured
LiveCodeBench (Artificial Analysis run)83.6%Not measuredOnly GPT-5.1-Codex-Mini measured
Terminal-Bench Hard (Artificial Analysis run)33.3%37.9%Grok 4.20
Terminal-Bench61.6%57.3%GPT-5.1-Codex-Mini
WeirdMLNot measured52.3%Only Grok 4.20 measured
LMArena WebDev: HTML1253Not measuredOnly GPT-5.1-Codex-Mini measured
Neither model has a result on the other 27 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
Intelligence benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
AA Intelligence Index20.425.7Grok 4.20
Epoch Capabilities IndexNot measured152.1Only Grok 4.20 measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
Design Arena: agents building web appsNot measured1144Only Grok 4.20 measured
Design Arena: agents building full-stack appsNot measured1054Only Grok 4.20 measured
Design Arena: agents building mobile appsNot measured1090Only Grok 4.20 measured
Design Arena: agents building Android appsNot measured1052Only Grok 4.20 measured
Design Arena: agents building Godot gamesNot measured1089Only Grok 4.20 measured
Design Arena: HTML slidesNot measured1180Only Grok 4.20 measured
Finance Agent (Vals AI)Not measured28.5%Only Grok 4.20 measured
Tax Agent Bench (Vals AI)Not measured7.0%Only Grok 4.20 measured
Legal Research Bench (Vals AI)Not measured13.9%Only Grok 4.20 measured
Excel Modeling Benchmark (Vals AI)Not measured11.7%Only Grok 4.20 measured
τ²-Bench Telecom62.9%93.0%Grok 4.20
Vending-Bench 2Not measured$4,663Only Grok 4.20 measured
Neither model has a result on the other 27 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index02
Reasoning benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
GPQA DiamondNot measured88.6%Only Grok 4.20 measured
MMMU Pro (Vals AI)Not measured83.5%Only Grok 4.20 measured
GPQA Diamond (Artificial Analysis run)81.3%91.1%Grok 4.20
Humanity's Last Exam (Artificial Analysis run)18.5%34.5%Grok 4.20
ARC-AGINot measured89.5%Only Grok 4.20 measured
ARC-AGI-2Not measured65.1%Only Grok 4.20 measured
Neither model has a result on the other 15 boards here
MathDirectional onlyPublic boards, shown as published, kept out of the index3 boards, none shared
Math benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
AIMENot measured96.5%Only Grok 4.20 measured
AA Math Index91.7Not measuredOnly GPT-5.1-Codex-Mini measured
AIME 2025 (Artificial Analysis run)91.7%Not measuredOnly GPT-5.1-Codex-Mini measured
Neither model has a result on the other 10 boards here
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
Knowledge benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
MMLU ProNot measured86.3%Only Grok 4.20 measured
LegalBench (Vals AI)Not measured77.7%Only Grok 4.20 measured
CaseLaw (Vals AI)Not measured54.4%Only Grok 4.20 measured
CorpFin (Vals AI)Not measured63.7%Only Grok 4.20 measured
TaxEval (Vals AI)Not measured74.1%Only Grok 4.20 measured
MortgageTax (Vals AI)Not measured45.4%Only Grok 4.20 measured
MedQA (Vals AI)Not measured94.5%Only Grok 4.20 measured
MedCode (Vals AI)Not measured32.2%Only Grok 4.20 measured
MMLU Pro (Artificial Analysis run)82.0%Not measuredOnly GPT-5.1-Codex-Mini measured
Neither model has a result on the other 8 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index08
Web design benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
Design Arena: websites11111229Grok 4.20
Design Arena: UI components10811199Grok 4.20
Design Arena: game dev10921192Grok 4.20
Design Arena: data viz10961217Grok 4.20
Design Arena: 3D9881193Grok 4.20
Design Arena: all code categories10941221Grok 4.20
Design Arena: SVG9781164Grok 4.20
Design Arena: ASCII art11041174Grok 4.20
Neither model has a result on the other 1 board here
GeneralLike-for-likePublic boards, shown as published, kept out of the index02
General benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
SAGE (Vals AI)Not measured38.2%Only Grok 4.20 measured
MedScribe (Vals AI)Not measured63.4%Only Grok 4.20 measured
Vals Multimodal IndexNot measured39.1%Only Grok 4.20 measured
IFBench67.9%81.2%Grok 4.20
Long context reasoning (AA-LCR)66.7%69.0%Grok 4.20
DTBenchNot measured90.1%Only Grok 4.20 measured
LMCANot measured38.7%Only Grok 4.20 measured
CL-benchNot measured22.2%Only Grok 4.20 measured
CL-bench LifeNot measured11.9%Only Grok 4.20 measured
Neither model has a result on the other 37 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-5.1-Codex-Mini and Grok 4.20
BenchmarkGPT-5.1-Codex-MiniGrok 4.20Leader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

GPT-5.1-Codex-Mini$0.0013Fits in one request
Grok 4.20$0.0025Fits in one request

GPT-5.1-Codex-Mini costs less

Repository review

50K input + 3K output tokens

GPT-5.1-Codex-Mini$0.018Fits in one request
Grok 4.20$0.070Fits in one request

GPT-5.1-Codex-Mini costs less

Agent loop

200K input + 10K output tokens

GPT-5.1-Codex-Mini$0.070Fits in one request
Grok 4.20$0.275Fits in one request

GPT-5.1-Codex-Mini costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of GPT-5.1-Codex-Mini and Grok 4.20
SpecificationOpenAI GPT-5.1-Codex-MiniSpaceXAI Grok 4.20
MakerOpenAIxAI
WeightsNo public weights listedNo public weights listed
ReleasedNovember 13, 2025March 31, 2026
Context window400K2M
Input $/Mtok$0.25$1.25
Output $/Mtok$2.00$2.50
Coding indexNot benchmarked33.3
Independent measurements behind it12
Cost per solved taskNot computable$0.72
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-5.1-Codex-Mini better than Grok 4.20 for coding?

Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; GPT-5.1-Codex-Mini has none, so the two cannot be ranked on coding. GPT-5.1-Codex-Mini has the edge where output tokens cost 1.3x less, and where the benchmark that matters is Terminal-Bench, where it leads.

Which is cheaper, GPT-5.1-Codex-Mini or Grok 4.20?

GPT-5.1-Codex-Mini costs $0.25 per million input tokens and $2.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. Cost per solved task is known for Grok 4.20 only.

Which has the bigger context window, GPT-5.1-Codex-Mini or Grok 4.20?

Grok 4.20, with 2M tokens against 400K.

How many benchmarks is the GPT-5.1-Codex-Mini vs Grok 4.20 comparison based on?

16 benchmarks have a result for both models as of October 21, 2026. GPT-5.1-Codex-Mini's coding index rests on 1 independent benchmark and Grok 4.20's on 2. Where only one model has a result, the page says so instead of naming a winner.

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