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Head-to-head comparison

Gemini 3.8 Flash vs GPT-6 Astra

Gemini 3.8 Flash (Google) and GPT-6 Astra (OpenAI) 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 9 September 2026

As of 9 September 2026, GPT-6 Astra holds the stronger ModelCap Index position (#1 vs #7); and Gemini 3.8 Flash is 13.3× cheaper per output token ($3.75/1M vs $50.00/1M).

Which should you choose?

Choose Gemini 3.8 Flash if…

  • API cost matters — $3.75/1M output tokens against $50.00/1M, about 13.3× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.75/1M against $10.00/1M.

Choose GPT-6 Astra if…

  • you want the stronger overall ModelCap Index position — #1 against #7 (93.7 vs 82.2 points).
  • LMArena Agent is your yardstick — 12.5% against 4.0%.
  • AA Intelligence Index is your yardstick — 52.8 against 41.2.
  • AA Terminal-Bench 2.1 is your yardstick — 88.4% against 87.6%.
  • AA Humanity's Last Exam is your yardstick — 54.7% against 47.8%.
  • Terminal-Bench 4.0 is your yardstick — 58.2% against 19.1%.
  • you want the more recently listed model — GPT-6 Astra was listed 4 September 2026, Gemini 3.8 Flash 2 September 2026.

Gemini 3.8 Flash vs GPT-6 Astra: specs, pricing and context

Specification comparison of Gemini 3.8 Flash and GPT-6 Astra
FieldGemini 3.8 FlashGoogleGPT-6 AstraOpenAI
ModelCap Index position#7#1
Index score82.293.7
EvidenceMeasuredMeasured
Input price / 1M tokens$0.75$10.00
Output price / 1M tokens$3.75$50.00
Context window1M tokens1M tokens
Max output tokens66K128K
API providers listed22
Weight accessAPI onlyAPI only
Input modalitiesText, Image, Video, File, AudioFile, Image, Text
First listed2 September 20264 September 2026
PublisherGoogleOpenAI

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: Gemini 3.8 Flash vs GPT-6 Astra

Public benchmark boards where Gemini 3.8 Flash or GPT-6 Astra has a published result
BoardGemini 3.8 FlashGPT-6 AstraLeads
Arena codingArena (LMArena)15371521–1553High—Only one result
LMArena AgentLMArena4.0%2.1%–6.0%High12.5%10.4%–14.7%MaxGPT-6 Astra
ARC-AGI-2ARC Prize Foundation—95.0%MaxOnly one result
ARC-AGI-3ARC Prize Foundation—62.7%MaxOnly one result
AA Intelligence IndexArtificial Analysis41.2intelligence-index:v4.3:high52.8intelligence-index:v4.3:maxGPT-6 Astra
AA Terminal-Bench 2.1Artificial Analysis87.6%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="Gemini 3.8 Flash (high)":reasoning=true88.4%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="GPT-6 Astra (max)":reasoning=trueGPT-6 Astra
AA Humanity's Last ExamArtificial Analysis47.8%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Gemini 3.8 Flash (high)":reasoning=true54.7%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GPT-6 Astra (max)":reasoning=trueGPT-6 Astra
Terminal-Bench 4.0Terminal-Bench (Laude Institute)19.1%15.7%–22.5%mini-SWE-agent · High58.2%55.4%–61.0%Codex · MaxGPT-6 Astra

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.

Gemini 3.8 Flash vs GPT-6 Astra: common questions

Is Gemini 3.8 Flash better than GPT-6 Astra?

GPT-6 Astra ranks higher on the ModelCap Index as of 9 September 2026: #1 against #7. 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 overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Gemini 3.8 Flash cheaper than GPT-6 Astra?

Gemini 3.8 Flash is cheaper on output tokens: $3.75/1M against $50.00/1M. Input tokens are $0.75/1M for Gemini 3.8 Flash and $10.00/1M for GPT-6 Astra. 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 $3.38 for Gemini 3.8 Flash versus $45.00 for GPT-6 Astra. Gemini 3.8 Flash costs 92.5% 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, Gemini 3.8 Flash or GPT-6 Astra?

Both publish a 1M-token context window.

Which is better for coding, Gemini 3.8 Flash or GPT-6 Astra?

AA Terminal-Bench 2.1: Gemini 3.8 Flash 87.6%, GPT-6 Astra 88.4% — GPT-6 Astra leads. Terminal-Bench 4.0: Gemini 3.8 Flash 19.1%, GPT-6 Astra 58.2% — GPT-6 Astra leads.

Are Gemini 3.8 Flash and GPT-6 Astra open-weight models?

Gemini 3.8 Flash: API only. GPT-6 Astra: 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 Gemini 3.8 Flash and GPT-6 Astra?

ModelCap currently lists 2 API providers for Gemini 3.8 Flash and 2 for GPT-6 Astra, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Gemini 3.8 Flash vs GPT-6 Astra comparison?

Every figure comes from the sealed ModelCap dataset published 9 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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