Which is cheaper, Gemini 3.8 Flash and GPT-6.1 Terra?

Gemini 3.8 Flash has the lowest input price. Per 1M input tokens: Gemini 3.8 Flash from $0.75 and GPT-6.1 Terra from $1.00.

Which has the larger context window, Gemini 3.8 Flash and GPT-6.1 Terra?

GPT-6.1 Terra has the largest context window: Gemini 3.8 Flash 1,048,576 tokens and GPT-6.1 Terra 1,050,000 tokens.

Can I switch between Gemini 3.8 Flash and GPT-6.1 Terra without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (google/gemini-3.8-flash, openai/gpt-6.1-terra).

Gemini 3.8 Flash vs GPT-6.1 Terra

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

Estimate monthly cost for these models

Gemini 3.8 Flash Googlegoogle/gemini-3.8-flash

GPT-6.1 Terra OpenAIopenai/gpt-6.1-terra

Creator

Google

OpenAI

Released

Sep 2, 2026

Oct 26, 2026

Context window

1.05M

Max output

66K

128K

Input / 1MLowest provider price

$0.75

$1.00

Output / 1MLowest provider price

$3.75

$5.00

Providers

IntelligenceArtificial Analysis index

30.5

51.0

Accepts

Text, Image, Audio, Video, Files

Text, Image, Files

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

Gemini 3.8 Flash vs GPT-6.1 Terra: summary

Gemini 3.8 Flash and GPT-6.1 Terra are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Gemini 3.8 Flash, from Google, has a 1,048,576-token context window, costs from $0.75/1M input and $3.75/1M output tokens across 2 providers and scores 30.5 on the Artificial Analysis Intelligence Index.

GPT-6.1 Terra, from OpenAI, has a 1,050,000-token context window, costs $1.00/1M input and $5.00/1M output tokens and scores 51.0 on the Artificial Analysis Intelligence Index.

Gemini 3.8 Flash is the cheapest on input, 1.3× cheaper than the next model, GPT-6.1 Terra has the largest context window and GPT-6.1 Terra scores highest for intelligence.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="google/gemini-3.8-flash", messages=[...]) # or client.chat.completions.create(model="openai/gpt-6.1-terra", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis