Claude Mythos 5.1 vs Gemini 3.8 Flash
Claude Mythos 5.1 and Gemini 3.8 Flash are closely matched at 45.1 and 51.2 on the LLM Stats Score. Gemini 3.8 Flash is 13.3x cheaper per token.
Anthropic · Google · Updated for 2026
Which is better?
Claude Mythos 5.1 and Gemini 3.8 Flash are closely matched on the overall LLM Stats Score at 45.1 and 51.2.
In the 1 individual benchmarks reported for both models, Claude Mythos 5.1 wins 1; this is a narrower head-to-head signal than the composite indexes.
On price, Gemini 3.8 Flash is roughly 13.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Gemini 3.8 Flash also accepts a larger context window (1,048,576 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Mythos 5.1
- you value its reported benchmark strengths — it wins 1 of 1 exact shared results
Choose Gemini 3.8 Flash
- cost matters — it's about 13.3x cheaper per token
- you process long inputs — it offers a 1,048,576 token context window
- you want the most recent training data — it shipped Sep 2026
At a glance
The differences that matter most.
Individual benchmarks
1 reported for Claude Mythos 5.1 · 13 for Gemini 3.8 Flash
Claude Mythos 5.1 outperforms in 1 benchmarks (Terminal-Bench 4.0), while Gemini 3.8 Flash is better at 0 benchmarks.
Claude Mythos 5.1 significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Mythos 5.1 ($10.00/1M tokens) is 13.3x more expensive than Gemini 3.8 Flash ($0.75/1M tokens).
For output processing, Claude Mythos 5.1 ($50.00/1M tokens) is 13.3x more expensive than Gemini 3.8 Flash ($3.75/1M tokens).
In conclusion, Claude Mythos 5.1 is more expensive than Gemini 3.8 Flash.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Gemini 3.8 Flash accepts 1,048,576 input tokens compared to Claude Mythos 5.1's 1,000,000 tokens. Claude Mythos 5.1 can generate longer responses up to 128,000 tokens, while Gemini 3.8 Flash is limited to 65,536 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Mythos 5.1 and Gemini 3.8 Flash support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Mythos 5.1
Gemini 3.8 Flash
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Mythos 5.1 was released on 2026-09-01, while Gemini 3.8 Flash was released on 2026-09-02.
Gemini 3.8 Flash is 0 month newer than Claude Mythos 5.1.
Sep 1, 2026
1 weeks ago
Sep 2, 2026
6 days ago
1d newerKnowledge Cutoff
When training data ends
Gemini 3.8 Flash has a documented knowledge cutoff of 2026-03-31, while Claude Mythos 5.1's cutoff date is not specified.
We can confirm Gemini 3.8 Flash's training data extends to 2026-03-31, but cannot make a direct comparison without Claude Mythos 5.1's cutoff date.
—
Mar 2026
Provider Availability
Claude Mythos 5.1 is available from Anthropic. Gemini 3.8 Flash is available from Google.
Claude Mythos 5.1
Gemini 3.8 Flash
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Mythos 5.1 and Gemini 3.8 Flash side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Mythos 5.1 vs Gemini 3.8 Flash.