Claude Opus 4.8 vs Gemini 3.8 Flash: a data-driven comparison

Side-by-side comparison

Criterion	Claude Opus 4.8	Gemini 3.8 Flash
Developer	Anthropic	Google DeepMind
Released	May 28, 2026	September 2, 2026
Capability index	83.4 / 100	83.7 / 100
Input price	$5	$0.75
Output price	$25	$3.75
Cost of a typical task	$0.15	$0.023
Context window	1,000,000 tokens	1,048,576 tokens
Maximum output	128,000 tokens	65,536 tokens
Reasoning mode	Yes	Yes
Tool calling	Yes	Yes
Accepted inputs	text, image, PDF	text, image, video, audio, PDF
Open weights	No	No
Knowledge cutoff	January 2026	Not disclosed

What are we comparing?

This comparison pits two mid-range models, balancing quality and cost against each other: Claude Opus 4.8 and Gemini 3.8 Flash, one from Anthropic, the other from Google DeepMind. The first dates from May 28, 2026, the second from September 2, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

What the benchmarks say

On our capability index, Claude Opus 4.8 scores 83.4 out of 100 and Gemini 3.8 Flash 83.7. The gap is too small to separate them.

On the 5 benchmarks reported for both, Claude Opus 4.8 wins 2 times and Gemini 3.8 Flash 3:

GPQA Diamond (PhD-level science questions): Claude Opus 4.8 91%, Gemini 3.8 Flash 95.4%
OTIS Mock AIME (competition mathematics problems): Claude Opus 4.8 98.3%, Gemini 3.8 Flash 98.9%
FrontierMath (very hard research-level mathematics): Claude Opus 4.8 80%, Gemini 3.8 Flash 68.4%
FrontierCode (advanced programming tasks): Claude Opus 4.8 46.5%, Gemini 3.8 Flash 41.2%
APEX-Agents (professional tasks carried out by an agent): Claude Opus 4.8 48.9%, Gemini 3.8 Flash 64.3%

Budget

Claude Opus 4.8 costs $5 per million input tokens and $25 per million output tokens; Gemini 3.8 Flash costs $0.75 and $3.75.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.15 with Claude Opus 4.8 versus $0.023 with Gemini 3.8 Flash. Gemini 3.8 Flash is 6.7 times cheaper, a gap that adds up quickly over 1,000 tasks: $127.5 difference.

Run the numbers with your own volumes in the agent cost calculator.

Context and capabilities

Gemini 3.8 Flash reads more in one go: 1,048,576 tokens of context (roughly 1,573 pages), versus 1,000,000 for Claude Opus 4.8.

Reasoning mode: Claude Opus 4.8 yes, Gemini 3.8 Flash yes. Tool calling: Claude Opus 4.8 yes, Gemini 3.8 Flash yes. Image input: Claude Opus 4.8 yes, Gemini 3.8 Flash yes.

Neither publishes its weights: both are used through an API.

In short

Our reading of the data:

Choose Gemini 3.8 Flash for a lower cost and a more recent release.

This verdict relies on public figures; it does not replace a trial on your own tasks.

Frequently asked questions

Claude Opus 4.8 or Gemini 3.8 Flash: which is better?

On our index (Epoch AI data), Claude Opus 4.8 scores 83.4 and Gemini 3.8 Flash 83.7 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

Gemini 3.8 Flash. To read 20,000 tokens and write 2,000, expect $0.15 with Claude Opus 4.8 and $0.023 with Gemini 3.8 Flash (prices as of October 22, 2026).

Which one has the larger context window?

Gemini 3.8 Flash, with 1,048,576 tokens versus 1,000,000.

Can I run Claude Opus 4.8 or Gemini 3.8 Flash on my own servers?

No: both are closed models, available through an API.

Claude Opus 4.8 or Gemini 3.8 Flash: which to choose?