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Gemini 3.8 Flash vs Grok 4.3

Gemini 3.8 Flash leads Grok 4.3 on coding, 61.6 to 37.4 on the Vibe Coding Index, and Grok 4.3 costs 1.5x less per output token ($2.50 vs $3.75 per million). Updated October 22, 2026; 95 benchmarks have a result for both.

Replace Gemini 3.8 Flash Replace Grok 4.3
Gemini 3.8 FlashGoogle
Coding
61.6
Overall
69.0
Output $/M
$3.75
95
Grok 4.3xAI
Coding
37.4
Overall
53.1
Output $/M
$2.50
0
vs boards won of 95 shared

Gemini 3.8 Flash or Grok 4.3: which to pick

Pick Gemini 3.8 Flash for coding: it scores 61.6 on the Vibe Coding Index against 37.4 for Grok 4.3.

Pick Grok 4.3 for output tokens 1.5x cheaper ($2.50 vs $3.75 per million) and a lower cost per solved task ($0.31 against $2.74).

Model AGemini 3.8 FlashGoogle61.6/1006 independent benchmarks$2.74 per solved taskModel BGrok 4.3xAI37.4/1003 independent benchmarks$0.31 per solved task
Shared results
95
Gemini 3.8 Flash only
33
Grok 4.3 only
10
Like-for-like categories
8 of 9

Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.

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
Gemini 3.8 Flash 61.6 from 6 benchmarks, Grok 4.3 37.4 from 3 benchmarks.
Widest category
Agentic work, 26.7 points apart on average over 13 shared benchmarks.
Widest single gap
Vibe Code Bench (Vals AI): Gemini 3.8 Flash 78.7% against Grok 4.3 19.4%, 59.3 points apart on a 0 to 100 scale.
Output price
Gemini 3.8 Flash $3.75 against Grok 4.3 $2.50 per million output tokens, 1.5x apart.
Context window
Gemini 3.8 Flash takes 1.05M tokens, Grok 4.3 1M.

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
CategoryGemini 3.8 FlashBarsGrok 4.3Ties
Coding170
Intelligence10
Agentic work130
Reasoning110
Math60
Knowledge100
Web design80
General290
All shared boards950
CodingLike-for-likeSix of these boards feed the Vibe Coding Index170
Coding benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
LiveBench coding82.2%Not measuredOnly Gemini 3.8 Flash measured
LMArena WebDev15851358Gemini 3.8 Flash
AA Coding Index76.342.2Gemini 3.8 Flash
LiveCodeBench (Vals AI)89.5%84.5%Gemini 3.8 Flash
SWE-bench Verified (Vals AI)80.0%71.4%Gemini 3.8 Flash
Terminal-Bench 4 (Vals AI)19.7%Not measuredOnly Gemini 3.8 Flash measured
Vibe Code Bench (Vals AI)78.7%19.4%Gemini 3.8 Flash
Code migration (Vals AI)36.5%6.8%Gemini 3.8 Flash
ProgramBench (Vals AI)1.0%0.0%Gemini 3.8 Flash
IOI (Vals AI)56.9%Not measuredOnly Gemini 3.8 Flash measured
Terminal-Bench 2.1 (Vals AI)81.3%42.0%Gemini 3.8 Flash
SWE-bench Multimodal (Vals AI)40.8%Not measuredOnly Gemini 3.8 Flash measured
Vibe Code Bench 1-100 (Vals AI)18.8%Not measuredOnly Gemini 3.8 Flash measured
SkillsBench (Vals AI)58.0%40.6%Gemini 3.8 Flash
CyberBench (Vals AI)43.8%Not measuredOnly Gemini 3.8 Flash measured
SciCode56.6%48.3%Gemini 3.8 Flash
Terminal-Bench Hard (Artificial Analysis run)Not measured37.9%Only Grok 4.3 measured
FrontierCode41.2%Not measuredOnly Gemini 3.8 Flash measured
FrontierSWE19.6%Not measuredOnly Gemini 3.8 Flash measured
WeirdML84.8%49.9%Gemini 3.8 Flash
ALE-Bench1269.7944.2Gemini 3.8 Flash
LMArena Text: coding15081415Gemini 3.8 Flash
LMArena Text: software and IT15071416Gemini 3.8 Flash
LMArena WebDev: React15771353Gemini 3.8 Flash
LMArena WebDev: HTML16161367Gemini 3.8 Flash
LMArena WebDev: from an image15931375Gemini 3.8 Flash
SciCode12.3%Not measuredOnly Gemini 3.8 Flash measured
Neither model has a result on the other 12 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
AA Intelligence Index40.924.9Gemini 3.8 Flash
Epoch Capabilities Index157.4Not measuredOnly Gemini 3.8 Flash measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index130
Agentic work benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
AA Agentic Index40.215.5Gemini 3.8 Flash
Design Arena: agents building web apps12381126Gemini 3.8 Flash
Design Arena: agents building full-stack apps12441006Gemini 3.8 Flash
Design Arena: agents building mobile apps12361058Gemini 3.8 Flash
Design Arena: agents building Android apps1078962Gemini 3.8 Flash
Design Arena: agents building Godot games1273914Gemini 3.8 Flash
Design Arena: agents building gamesNot measured1007Only Grok 4.3 measured
Design Arena: HTML slidesNot measured959Only Grok 4.3 measured
Design Arena: PowerPoint slides1153988Gemini 3.8 Flash
Design Arena: spreadsheets1022879Gemini 3.8 Flash
LiveBench research79.1%Not measuredOnly Gemini 3.8 Flash measured
LiveBench browser64.0%Not measuredOnly Gemini 3.8 Flash measured
LiveBench long agentic30.1%Not measuredOnly Gemini 3.8 Flash measured
SREBench (Vals AI)11.1%Not measuredOnly Gemini 3.8 Flash measured
Finance Agent (Vals AI)61.4%37.7%Gemini 3.8 Flash
Tax Agent Bench (Vals AI)32.1%6.2%Gemini 3.8 Flash
Legal Research Bench (Vals AI)38.9%15.4%Gemini 3.8 Flash
Harvey's Legal Agent Benchmark (Vals AI)12.1%Not measuredOnly Gemini 3.8 Flash measured
Excel Modeling Benchmark (Vals AI)72.2%18.4%Gemini 3.8 Flash
BioMysteryBench (Vals AI)62.2%Not measuredOnly Gemini 3.8 Flash measured
Terminal-Bench-Science (Vals AI)8.6%Not measuredOnly Gemini 3.8 Flash measured
Vals Science Index35.8%Not measuredOnly Gemini 3.8 Flash measured
Time Horizon Index (Vals AI)18.8%Not measuredOnly Gemini 3.8 Flash measured
CUA-bench (Vals AI)4.2%Not measuredOnly Gemini 3.8 Flash measured
τ²-Bench TelecomNot measured97.7%Only Grok 4.3 measured
APEX-Agents64.3%Not measuredOnly Gemini 3.8 Flash measured
Remote Labor Index5.8%Not measuredOnly Gemini 3.8 Flash measured
Vending-Bench 2$5,094$35Gemini 3.8 Flash
LMArena SearchNot measured1166Only Grok 4.3 measured
Neither model has a result on the other 12 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index110
Reasoning benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
GPQA Diamond94.4%91.4%Gemini 3.8 Flash
LiveBench reasoning89.3%Not measuredOnly Gemini 3.8 Flash measured
MysteryMechanism (Vals AI)36.5%Not measuredOnly Gemini 3.8 Flash measured
MMMU Pro (Vals AI)89.1%83.1%Gemini 3.8 Flash
GPQA Diamond (Artificial Analysis run)95.3%90.1%Gemini 3.8 Flash
Humanity's Last Exam (Artificial Analysis run)47.8%37.2%Gemini 3.8 Flash
GPQA Diamond (Epoch AI run)95.4%88.8%Gemini 3.8 Flash
ARC-AGI98.5%Not measuredOnly Gemini 3.8 Flash measured
ARC-AGI-289.2%Not measuredOnly Gemini 3.8 Flash measured
Chess puzzles58.0%18.0%Gemini 3.8 Flash
Mystery game puzzles47.0%Not measuredOnly Gemini 3.8 Flash measured
LMArena Text: hard prompts15091396Gemini 3.8 Flash
LMArena Text: expert15261384Gemini 3.8 Flash
LMArena Text: hard prompts in English15041402Gemini 3.8 Flash
LMArena Vision: diagrams13451241Gemini 3.8 Flash
LMArena Vision: homework13511241Gemini 3.8 Flash
Neither model has a result on the other 6 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
OTIS Mock AIME98.9%93.3%Gemini 3.8 Flash
FrontierMath, tiers 1 to 368.4%42.8%Gemini 3.8 Flash
FrontierMath, tier 422.0%14.6%Gemini 3.8 Flash
ProofBench48.0%11.0%Gemini 3.8 Flash
LMArena Text: math15321387Gemini 3.8 Flash
LMArena Text: mathematical work15191396Gemini 3.8 Flash
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100
Knowledge benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
MMLU Pro90.2%85.8%Gemini 3.8 Flash
LegalBench (Vals AI)87.0%84.5%Gemini 3.8 Flash
CaseLaw (Vals AI)Not measured79.3%Only Grok 4.3 measured
CorpFin (Vals AI)Not measured68.5%Only Grok 4.3 measured
TaxEval (Vals AI)74.5%70.8%Gemini 3.8 Flash
MortgageTax (Vals AI)65.3%48.3%Gemini 3.8 Flash
MedCode (Vals AI)48.1%38.1%Gemini 3.8 Flash
SimpleQA Verified69.7%33.2%Gemini 3.8 Flash
LMArena Text: science15231399Gemini 3.8 Flash
LMArena Text: medicine and healthcare15081384Gemini 3.8 Flash
LMArena Text: legal and government14971386Gemini 3.8 Flash
LMArena Text: business and finance14791381Gemini 3.8 Flash
FACTS Benchmark Suite69.4%Not measuredOnly Gemini 3.8 Flash measured
Neither model has a result on the other 5 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index80
Web design benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
Design Arena: websites13001196Gemini 3.8 Flash
Design Arena: UI components13161190Gemini 3.8 Flash
Design Arena: game dev13041173Gemini 3.8 Flash
Design Arena: data viz12701179Gemini 3.8 Flash
Design Arena: 3D12941124Gemini 3.8 Flash
Design Arena: all code categories13031186Gemini 3.8 Flash
Design Arena: SVG12961080Gemini 3.8 Flash
Design Arena: ASCII art12621125Gemini 3.8 Flash
LiveBench design72.7%Not measuredOnly Gemini 3.8 Flash measured
GeneralLike-for-likePublic boards, shown as published, kept out of the index290
General benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
Vals Index56.0%Not measuredOnly Gemini 3.8 Flash measured
LiveBench data analysis54.0%Not measuredOnly Gemini 3.8 Flash measured
Public Benefits Bench (Vals AI)65.3%51.7%Gemini 3.8 Flash
SAGE (Vals AI)35.1%19.7%Gemini 3.8 Flash
MedScribe (Vals AI)84.5%74.4%Gemini 3.8 Flash
Vals Multimodal IndexNot measured43.3%Only Grok 4.3 measured
IFBenchNot measured83.3%Only Grok 4.3 measured
Long context reasoning (AA-LCR)84.0%75.0%Gemini 3.8 Flash
DTBench95.7%90.7%Gemini 3.8 Flash
LMCA52.9%38.3%Gemini 3.8 Flash
Surface Evolver Bench76.9%Not measuredOnly Gemini 3.8 Flash measured
Furniture assembly31.7%Not measuredOnly Gemini 3.8 Flash measured
LMArena Text14991397Gemini 3.8 Flash
LMArena Text: instruction following14921366Gemini 3.8 Flash
LMArena Text: creative writing14881380Gemini 3.8 Flash
LMArena Vision13151229Gemini 3.8 Flash
LMArena Text: English14981404Gemini 3.8 Flash
LMArena Text: non-English14911385Gemini 3.8 Flash
LMArena Text: Chinese15531422Gemini 3.8 Flash
LMArena Text: German15011395Gemini 3.8 Flash
LMArena Text: Japanese15071379Gemini 3.8 Flash
LMArena Text: Korean14641354Gemini 3.8 Flash
LMArena Text: French14961411Gemini 3.8 Flash
LMArena Text: Spanish14871399Gemini 3.8 Flash
LMArena Text: Russian15141399Gemini 3.8 Flash
LMArena Text: Polish14971398Gemini 3.8 Flash
LMArena Text: multi-turn15031406Gemini 3.8 Flash
LMArena Text: longer queries15071393Gemini 3.8 Flash
LMArena Text: writing and language14941385Gemini 3.8 Flash
LMArena Text: entertainment and media14801370Gemini 3.8 Flash
LMArena Vision: English13181235Gemini 3.8 Flash
LMArena Vision: Chinese14161257Gemini 3.8 Flash
LMArena Vision: reading text13331235Gemini 3.8 Flash
LMArena Vision: humor13211222Gemini 3.8 Flash
LMArena Vision: recognizing thingsNot measured1217Only Grok 4.3 measured
LMArena Vision: creative writing12991237Gemini 3.8 Flash
Neither model has a result on the other 10 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for Gemini 3.8 Flash and Grok 4.3
BenchmarkGemini 3.8 FlashGrok 4.3Leader
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

Gemini 3.8 Flash$0.0026Fits in one request
Grok 4.3$0.0025Fits in one request

Grok 4.3 costs less

Repository review

50K input + 3K output tokens

Gemini 3.8 Flash$0.049Fits in one request
Grok 4.3$0.070Fits in one request

Gemini 3.8 Flash costs less

Agent loop

200K input + 10K output tokens

Gemini 3.8 Flash$0.188Fits in one request
Grok 4.3$0.275Fits in one request

Gemini 3.8 Flash 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 Gemini 3.8 Flash and Grok 4.3
SpecificationGoogle Gemini 3.8 FlashSpaceXAI Grok 4.3
MakerGooglexAI
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 2, 2026April 30, 2026
Context window1.05M1M
Input $/Mtok$0.75$1.25
Output $/Mtok$3.75$2.50
Coding index61.637.4
Independent measurements behind it63
Cost per solved task$2.74$0.31
SourceOpenRouter listingOpenRouter listing

Questions

Is Gemini 3.8 Flash better than Grok 4.3 for coding?

Pick Gemini 3.8 Flash for coding: it scores 61.6 on the Vibe Coding Index against 37.4 for Grok 4.3. Pick Grok 4.3 for output tokens 1.5x cheaper ($2.50 vs $3.75 per million) and a lower cost per solved task ($0.31 against $2.74).

Which is cheaper, Gemini 3.8 Flash or Grok 4.3?

Gemini 3.8 Flash costs $0.75 per million input tokens and $3.75 per million output tokens; Grok 4.3 costs $1.25 and $2.50. Per solved SWE-bench Verified task, Gemini 3.8 Flash costs $2.74 and Grok 4.3 $0.31.

Which has the bigger context window, Gemini 3.8 Flash or Grok 4.3?

Gemini 3.8 Flash, with 1.05M tokens against 1M.

How many benchmarks is the Gemini 3.8 Flash vs Grok 4.3 comparison based on?

95 benchmarks have a result for both models as of October 22, 2026. Gemini 3.8 Flash's coding index rests on 6 independent benchmarks and Grok 4.3's on 3. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/gemini-3-8-flash-vs-grok-4-3">LLMBenchmark.ai, Gemini 3.8 Flash vs Grok 4.3</a></p>