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Head-to-head comparison

Claude Opus 5.5 vs Gemini 3.5 Flash Lite

Claude Opus 5.5 (Anthropic) and Gemini 3.5 Flash Lite (Google) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 28 September 2026

As of 28 September 2026, Claude Opus 5.5 holds the stronger ModelCap Index position (#1 vs #28); and Gemini 3.5 Flash Lite is 8× cheaper per output token ($2.50/1M vs $20.00/1M).

Which should you choose?

Choose Claude Opus 5.5 if…

  • you want the stronger overall ModelCap Index position — #1 against #28 (88.4 vs 71.5 points).
  • you want provider choice — 5 listed API providers against 2.
  • Arena coding is your yardstick — 1547 against 1503.
  • ARC-AGI-2 is your yardstick — 93.3% against 10.3%.
  • AA Intelligence Index is your yardstick — 57.6 against 22.2.
  • AA Humanity's Last Exam is your yardstick — 61.4% against 18.8%.
  • you want the more recently listed model — Claude Opus 5.5 was listed 22 September 2026, Gemini 3.5 Flash Lite 21 July 2026.

Choose Gemini 3.5 Flash Lite if…

  • API cost matters — $2.50/1M output tokens against $20.00/1M, about 8× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.30/1M against $4.00/1M.

Claude Opus 5.5 vs Gemini 3.5 Flash Lite: specs, pricing and context

Specification comparison of Claude Opus 5.5 and Gemini 3.5 Flash Lite
FieldClaude Opus 5.5AnthropicGemini 3.5 Flash LiteGoogle
ModelCap Index position#1#28
Index score88.471.5
EvidenceMeasuredMeasured
Input price / 1M tokens$4.00$0.30
Output price / 1M tokens$20.00$2.50
Context window1M tokens1M tokens
Max output tokens128K66K
API providers listed52
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileText, Image, Video, File, Audio
First listed22 September 202621 July 2026
PublisherAnthropicGoogle

Evidence: 4 public benchmark observations across 4 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Opus 5.5 vs Gemini 3.5 Flash Lite

Public benchmark boards where Claude Opus 5.5 or Gemini 3.5 Flash Lite has a published result
BoardClaude Opus 5.5Gemini 3.5 Flash LiteLeads
Arena codingArena (LMArena)15471523–1571High15031496–1510Claude Opus 5.5
ARC-AGI-2ARC Prize Foundation93.3%High10.3%HighClaude Opus 5.5
AA Intelligence IndexArtificial Analysis57.6Reasoning22.2ReasoningClaude Opus 5.5
AA Humanity's Last ExamArtificial Analysis61.4%Adaptive Reasoning, Max Effort, Default Fallback18.8%ReasoningClaude Opus 5.5

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Opus 5.5 vs Gemini 3.5 Flash Lite: common questions

Is Claude Opus 5.5 better than Gemini 3.5 Flash Lite?

Claude Opus 5.5 ranks higher on the ModelCap Index as of 28 September 2026: #1 against #28. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals do not overlap, but the aggregate Index does not predict performance on every task; compare the relevant benchmark configurations before choosing.

Is Claude Opus 5.5 cheaper than Gemini 3.5 Flash Lite?

Gemini 3.5 Flash Lite is cheaper on output tokens: $2.50/1M against $20.00/1M. Input tokens are $4.00/1M for Claude Opus 5.5 and $0.30/1M for Gemini 3.5 Flash Lite. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $18.00 for Claude Opus 5.5 versus $1.85 for Gemini 3.5 Flash Lite. Gemini 3.5 Flash Lite costs 89.7% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

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

Both publish a 1M-token context window.

Which is better for coding, Claude Opus 5.5 or Gemini 3.5 Flash Lite?

Arena coding: Claude Opus 5.5 1547, Gemini 3.5 Flash Lite 1503 — Claude Opus 5.5 leads.

Are Claude Opus 5.5 and Gemini 3.5 Flash Lite open-weight models?

Claude Opus 5.5: API only. Gemini 3.5 Flash Lite: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Opus 5.5 and Gemini 3.5 Flash Lite?

ModelCap currently lists 5 API providers for Claude Opus 5.5 and 2 for Gemini 3.5 Flash Lite, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Opus 5.5 vs Gemini 3.5 Flash Lite comparison?

Every figure comes from the sealed ModelCap dataset published 28 September 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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