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Claude Opus 5.5 vs Gemini 3.5 Flash

Claude Opus 5.5 leads Gemini 3.5 Flash on coding, 88.8 to 39.8 on the Vibe Coding Index, and Gemini 3.5 Flash costs 2.2x less per output token ($9.00 vs $20.00 per million). Updated October 21, 2026; 81 benchmarks have a result for both.

Replace Claude Opus 5.5 Replace Gemini 3.5 Flash
Claude Opus 5.5Anthropic
Coding
88.8
Overall
87.1
Output $/M
$20.00
78
Gemini 3.5 FlashGoogle
Coding
39.8
Overall
63.8
Output $/M
$9.00
3
vs boards won of 81 shared

Claude Opus 5.5 or Gemini 3.5 Flash: which to pick

Pick Claude Opus 5.5 for coding: it scores 88.8 on the Vibe Coding Index against 39.8 for Gemini 3.5 Flash.

Pick Gemini 3.5 Flash for output tokens 2.2x cheaper ($9.00 vs $20.00 per million) and a larger context window (1.05M against 1M tokens).

Model AClaude Opus 5.5Anthropic88.8/1005 independent benchmarksNo cost per solved taskModel BGemini 3.5 FlashGoogle39.8/1004 independent benchmarks$1.21 per solved task
Shared results
81
Claude Opus 5.5 only
28
Gemini 3.5 Flash only
31
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
Claude Opus 5.5 88.8 from 5 benchmarks, Gemini 3.5 Flash 39.8 from 4 benchmarks.
Widest category
Math, 29.3 points apart on average over 6 shared benchmarks.
Widest single gap
Terminal-Bench 4 (Vals AI): Claude Opus 5.5 65.2% against Gemini 3.5 Flash 6.1%, 78.8 points apart on a 0 to 100 scale.
Output price
Claude Opus 5.5 $20.00 against Gemini 3.5 Flash $9.00 per million output tokens, 2.2x apart.
Context window
Claude Opus 5.5 takes 1M tokens, Gemini 3.5 Flash 1.05M.

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
CategoryClaude Opus 5.5BarsGemini 3.5 FlashTies
Coding140
Intelligence20
Agentic work90
Reasoning111
Math60
Knowledge61
Web design70
General231
All shared boards783
CodingLike-for-likeSix of these boards feed the Vibe Coding Index140
Coding benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
LiveBench coding96.3%Not measuredOnly Claude Opus 5.5 measured
LMArena WebDev18071499Claude Opus 5.5
LiveCodeBench (Vals AI)Not measured87.6%Only Gemini 3.5 Flash measured
SWE-bench Verified (Vals AI)Not measured78.8%Only Gemini 3.5 Flash measured
Terminal-Bench 4 (Vals AI)65.2%6.1%Claude Opus 5.5
Vibe Code Bench (Vals AI)90.3%48.7%Claude Opus 5.5
Code migration (Vals AI)66.7%26.8%Claude Opus 5.5
ProgramBench (Vals AI)18.5%0.0%Claude Opus 5.5
IOI (Vals AI)95.1%Not measuredOnly Claude Opus 5.5 measured
Terminal-Bench 2.1 (Vals AI)87.6%74.2%Claude Opus 5.5
SWE-bench Multimodal (Vals AI)70.2%Not measuredOnly Claude Opus 5.5 measured
Vibe Code Bench 1-100 (Vals AI)30.4%Not measuredOnly Claude Opus 5.5 measured
SkillsBench (Vals AI)Not measured52.7%Only Gemini 3.5 Flash measured
CyberBench (Vals AI)74.6%Not measuredOnly Claude Opus 5.5 measured
SciCode66.9%53.9%Claude Opus 5.5
Terminal-Bench Hard (Artificial Analysis run)Not measured46.2%Only Gemini 3.5 Flash measured
FrontierCode54.6%Not measuredOnly Claude Opus 5.5 measured
FrontierSWE62.3%Not measuredOnly Claude Opus 5.5 measured
WeirdMLNot measured62.6%Only Gemini 3.5 Flash measured
MirrorCode77.4%Not measuredOnly Claude Opus 5.5 measured
ALE-Bench2147.4911.0Claude Opus 5.5
LMArena Text: coding15451493Claude Opus 5.5
LMArena Text: software and IT15381494Claude Opus 5.5
LMArena WebDev: React18551495Claude Opus 5.5
LMArena WebDev: HTML17531522Claude Opus 5.5
LMArena WebDev: from an image17531504Claude Opus 5.5
SciCode18.5%12.3%Claude Opus 5.5
Neither model has a result on the other 12 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
Intelligence benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
AA Intelligence Index57.633.6Claude Opus 5.5
Epoch Capabilities Index168.8154.9Claude Opus 5.5
Agentic workLike-for-likePublic boards, shown as published, kept out of the index90
Agentic work benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
Design Arena: agents building web apps13171202Claude Opus 5.5
Design Arena: agents building full-stack appsNot measured1197Only Gemini 3.5 Flash measured
Design Arena: agents building mobile apps13101174Claude Opus 5.5
Design Arena: agents building Android appsNot measured1184Only Gemini 3.5 Flash measured
Design Arena: agents building Godot gamesNot measured1098Only Gemini 3.5 Flash measured
Design Arena: agents building gamesNot measured1180Only Gemini 3.5 Flash measured
Design Arena: HTML slidesNot measured1142Only Gemini 3.5 Flash measured
Design Arena: PowerPoint slidesNot measured1179Only Gemini 3.5 Flash measured
Design Arena: spreadsheets1352Not measuredOnly Claude Opus 5.5 measured
LiveBench research85.0%Not measuredOnly Claude Opus 5.5 measured
LiveBench browser80.0%Not measuredOnly Claude Opus 5.5 measured
LiveBench long agentic85.0%Not measuredOnly Claude Opus 5.5 measured
SREBench (Vals AI)33.6%Not measuredOnly Claude Opus 5.5 measured
Finance Agent (Vals AI)58.6%57.9%Claude Opus 5.5
Tax Agent Bench (Vals AI)45.6%21.6%Claude Opus 5.5
Legal Research Bench (Vals AI)50.5%30.8%Claude Opus 5.5
Harvey's Legal Agent Benchmark (Vals AI)9.2%Not measuredOnly Claude Opus 5.5 measured
Excel Modeling Benchmark (Vals AI)75.9%63.5%Claude Opus 5.5
BioMysteryBench (Vals AI)79.3%Not measuredOnly Claude Opus 5.5 measured
Terminal-Bench-Science (Vals AI)47.1%5.7%Claude Opus 5.5
Vals Science Index58.7%Not measuredOnly Claude Opus 5.5 measured
Time Horizon Index (Vals AI)91.3%Not measuredOnly Claude Opus 5.5 measured
CUA-bench (Vals AI)14.0%Not measuredOnly Claude Opus 5.5 measured
Robo-bench (Vals AI)14.6%Not measuredOnly Claude Opus 5.5 measured
τ²-Bench TelecomNot measured95.6%Only Gemini 3.5 Flash measured
APEX-Agents73.5%27.5%Claude Opus 5.5
Remote Labor Index21.3%Not measuredOnly Claude Opus 5.5 measured
SpireClimb3.3%Not measuredOnly Claude Opus 5.5 measured
Vending-Bench 2$9,235$5,396Claude Opus 5.5
LMArena Search1213Not measuredOnly Claude Opus 5.5 measured
Neither model has a result on the other 11 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index111
Reasoning benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
GPQA DiamondNot measured92.7%Only Gemini 3.5 Flash measured
LiveBench reasoning92.2%Not measuredOnly Claude Opus 5.5 measured
MysteryMechanism (Vals AI)49.5%Not measuredOnly Claude Opus 5.5 measured
MMMU Pro (Vals AI)Not measured88.3%Only Gemini 3.5 Flash measured
GPQA Diamond (Artificial Analysis run)Not measured92.2%Only Gemini 3.5 Flash measured
Humanity's Last Exam (Artificial Analysis run)61.4%42.7%Claude Opus 5.5
GPQA Diamond (Epoch AI run)90.6%92.8%Gemini 3.5 Flash
ARC-AGI98.5%92.5%Claude Opus 5.5
ARC-AGI-293.3%72.1%Claude Opus 5.5
SimpleBenchNot measured76.7%Only Gemini 3.5 Flash measured
Chess puzzles67.0%45.0%Claude Opus 5.5
Mystery game puzzles71.0%32.0%Claude Opus 5.5
EBR-bench71.4%4.8%Claude Opus 5.5
LMArena Text: hard prompts15361488Claude Opus 5.5
LMArena Text: expert15491495Claude Opus 5.5
LMArena Text: hard prompts in English15351483Claude Opus 5.5
LMArena Vision: diagrams13451323Claude Opus 5.5
LMArena Vision: homework13621330Claude Opus 5.5
Neither model has a result on the other 4 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index60
Math benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
OTIS Mock AIME100.0%95.6%Claude Opus 5.5
FrontierMath, tiers 1 to 391.2%62.8%Claude Opus 5.5
FrontierMath, tier 495.0%26.8%Claude Opus 5.5
ProofBench100.0%31.0%Claude Opus 5.5
LMArena Text: math15181504Claude Opus 5.5
LMArena Text: mathematical work15161495Claude Opus 5.5
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index61
Knowledge benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
MMLU ProNot measured89.5%Only Gemini 3.5 Flash measured
LegalBench (Vals AI)Not measured83.6%Only Gemini 3.5 Flash measured
CorpFin (Vals AI)Not measured64.7%Only Gemini 3.5 Flash measured
TaxEval (Vals AI)Not measured74.4%Only Gemini 3.5 Flash measured
MortgageTax (Vals AI)Not measured68.1%Only Gemini 3.5 Flash measured
MedCode (Vals AI)49.8%55.8%Gemini 3.5 Flash
SimpleQA Verified72.2%66.2%Claude Opus 5.5
LMArena Text: science15241495Claude Opus 5.5
LMArena Text: medicine and healthcare15091483Claude Opus 5.5
LMArena Text: legal and government15181488Claude Opus 5.5
LMArena Text: business and finance14941467Claude Opus 5.5
FACTS Benchmark Suite65.3%63.1%Claude Opus 5.5
Neither model has a result on the other 6 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index70
Web design benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
Design Arena: websites13361268Claude Opus 5.5
Design Arena: UI components13921273Claude Opus 5.5
Design Arena: game dev14581263Claude Opus 5.5
Design Arena: data viz13971236Claude Opus 5.5
Design Arena: 3D14771244Claude Opus 5.5
Design Arena: all code categories13901266Claude Opus 5.5
Design Arena: SVG13331254Claude Opus 5.5
Design Arena: ASCII artNot measured1254Only Gemini 3.5 Flash measured
LiveBench design86.9%Not measuredOnly Claude Opus 5.5 measured
GeneralLike-for-likePublic boards, shown as published, kept out of the index231
General benchmarks for Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
Vals Index70.2%Not measuredOnly Claude Opus 5.5 measured
LiveBench data analysis80.3%Not measuredOnly Claude Opus 5.5 measured
Public Benefits Bench (Vals AI)70.6%59.5%Claude Opus 5.5
SAGE (Vals AI)45.8%49.9%Gemini 3.5 Flash
MedScribe (Vals AI)91.4%76.6%Claude Opus 5.5
Vals Multimodal IndexNot measured62.9%Only Gemini 3.5 Flash measured
IFBenchNot measured76.3%Only Gemini 3.5 Flash measured
Long context reasoning (AA-LCR)84.7%74.3%Claude Opus 5.5
DTBench98.9%94.7%Claude Opus 5.5
LMCA68.2%47.1%Claude Opus 5.5
Surface Evolver BenchNot measured58.1%Only Gemini 3.5 Flash measured
Furniture assembly83.3%Not measuredOnly Claude Opus 5.5 measured
LMArena Text15161482Claude Opus 5.5
LMArena Text: instruction following15371467Claude Opus 5.5
LMArena Text: creative writing15351470Claude Opus 5.5
LMArena Vision13211308Claude Opus 5.5
LMArena Text: English15191481Claude Opus 5.5
LMArena Text: non-English15071475Claude Opus 5.5
LMArena Text: Chinese15821527Claude Opus 5.5
LMArena Text: GermanNot measured1494Only Gemini 3.5 Flash measured
LMArena Text: Japanese15341486Claude Opus 5.5
LMArena Text: KoreanNot measured1448Only Gemini 3.5 Flash measured
LMArena Text: French14931490Claude Opus 5.5
LMArena Text: Spanish15081480Claude Opus 5.5
LMArena Text: Russian15171493Claude Opus 5.5
LMArena Text: PolishNot measured1516Only Gemini 3.5 Flash measured
LMArena Text: multi-turn15011481Claude Opus 5.5
LMArena Text: longer queries15321483Claude Opus 5.5
LMArena Text: writing and language15321478Claude Opus 5.5
LMArena Text: entertainment and media15151459Claude Opus 5.5
LMArena Vision: English13171305Claude Opus 5.5
LMArena Vision: ChineseNot measured1377Only Gemini 3.5 Flash measured
LMArena Vision: reading text13261317Claude Opus 5.5
LMArena Vision: humorNot measured1321Only Gemini 3.5 Flash measured
LMArena Vision: creative writing13201301Claude Opus 5.5
LMArena DocumentNot measured1463Only Gemini 3.5 Flash measured
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 Claude Opus 5.5 and Gemini 3.5 Flash
BenchmarkClaude Opus 5.5Gemini 3.5 FlashLeader
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

Claude Opus 5.5$0.014Fits in one request
Gemini 3.5 Flash$0.0060Fits in one request

Gemini 3.5 Flash costs less

Repository review

50K input + 3K output tokens

Claude Opus 5.5$0.260Fits in one request
Gemini 3.5 Flash$0.102Fits in one request

Gemini 3.5 Flash costs less

Agent loop

200K input + 10K output tokens

Claude Opus 5.5$1.00Fits in one request
Gemini 3.5 Flash$0.390Fits in one request

Gemini 3.5 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 Claude Opus 5.5 and Gemini 3.5 Flash
SpecificationAnthropic Claude Opus 5.5Google Gemini 3.5 Flash
MakerAnthropicGoogle
WeightsNo public weights listedNo public weights listed
ReleasedSeptember 22, 2026May 19, 2026
Context window1M1.05M
Input $/Mtok$4.00$1.50
Output $/Mtok$20.00$9.00
Coding index88.839.8
Independent measurements behind it54
Cost per solved taskNot computable$1.21
SourceOpenRouter listingOpenRouter listing

Questions

Is Claude Opus 5.5 better than Gemini 3.5 Flash for coding?

Pick Claude Opus 5.5 for coding: it scores 88.8 on the Vibe Coding Index against 39.8 for Gemini 3.5 Flash. Pick Gemini 3.5 Flash for output tokens 2.2x cheaper ($9.00 vs $20.00 per million) and a larger context window (1.05M against 1M tokens).

Which is cheaper, Claude Opus 5.5 or Gemini 3.5 Flash?

Claude Opus 5.5 costs $4.00 per million input tokens and $20.00 per million output tokens; Gemini 3.5 Flash costs $1.50 and $9.00. Cost per solved task is known for Gemini 3.5 Flash only.

Which has the bigger context window, Claude Opus 5.5 or Gemini 3.5 Flash?

Gemini 3.5 Flash, with 1.05M tokens against 1M.

How many benchmarks is the Claude Opus 5.5 vs Gemini 3.5 Flash comparison based on?

81 benchmarks have a result for both models as of October 21, 2026. Claude Opus 5.5's coding index rests on 5 independent benchmarks and Gemini 3.5 Flash's on 4. Where only one model has a result, the page says so instead of naming a winner.

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