# Claude Mythos 5.1 vs Gemini 3.8 Flash

> Side-by-side benchmark comparison for Claude Mythos 5.1 and Gemini 3.8 Flash across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/claude-mythos-5-1-vs-gemini-3-8-flash
- Last updated: October 17, 2026

- Shared sourced benchmarks: 1
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: Claude Mythos 5.1 and Gemini 3.8 Flash share only 1 sourced benchmark row.

## Summary

- Only 1 shared sourced benchmark row is available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- Claude Mythos 5.1 has the lower published output-token price.

## Model Snapshot

| Property | Claude Mythos 5.1 | Gemini 3.8 Flash |
|----------|----------|----------|
| Creator | Anthropic | Google |
| Type | Proprietary | Proprietary |
| Reasoning | Reasoning | Reasoning |
| Context | 1M | 1M |
| Independent public score (not head-to-head) | null | 69.25 |
| Benchmarks Covered | 1 | 31 |
| Pricing (input/output) | Pricing unavailable / Pricing unavailable | $0.75 / $3.75 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 65.9 (Supported · #16/128)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| Terminal-Bench 4.0 | 60.90% | 19.10% | Claude Mythos 5.1 |
| Finance Agent v2 | Coming soon | 61.4% | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 89.4% | Coming soon |
| OSWorld 2.0 | Coming soon | 59.0% | Coming soon |
| Terminal-Bench 2.1 (Vals) | Coming soon | 81.3% | Coming soon |
| ApprenticeBench | Coming soon | 24% | Coming soon |
| Hermes Index | Coming soon | 38.1% | Coming soon |
| Hermes Bench | Coming soon | 62.2% | Coming soon |
| MazeBench | Coming soon | 4% | Coming soon |

### Coding

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 61 (Supported · #17/150)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| DeepSWE | Coming soon | 73.8% | Coming soon |
| Terminal-Bench 2.1 | Coming soon | 89.4% | Coming soon |
| CursorBench 3.2 | Coming soon | 69.2% | Coming soon |
| LiveCodeBench (Vals) | Coming soon | 89.5% | Coming soon |
| SWE-bench (Vals) | Coming soon | 80.0% | Coming soon |
| FrontierSWE v2 | Coming soon | 19.6% | Coming soon |
| CursorBench 4.0 | Coming soon | 39.6% | Coming soon |
| Bug Hunt Bench | Coming soon | 18.0 fixes | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 74.3 (#17/28)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| ARC-AGI-1 | Coming soon | 98.50% | Coming soon |
| ARC-AGI-2 | Coming soon | 89.2% | Coming soon |
| ARC-AGI-3 | Coming soon | 10.4% | Coming soon |

### Multimodal & Grounded

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 87.3 (#9/54)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| CharXiv w/o tools | Coming soon | 86.2% | Coming soon |
| LVBench | Coming soon | 87.1% | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 73.5 (Supported · #13/184)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| HLE-Verified | Coming soon | 54.9% | Coming soon |
| LABBench2 | Coming soon | 86.2% | Coming soon |
| BioMysteryBench (human-solvable) | Coming soon | 88.8% | Coming soon |
| BioMysteryBench (human-difficult) | Coming soon | 56.5% | Coming soon |
| GPQA Diamond (Vals) | Coming soon | 94.4% | Coming soon |
| MMLU-Pro (Vals) | Coming soon | 90.2% | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: Coming soon

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| Gray Swan IPI (15 attempts) | Coming soon | 5.5% | Coming soon |

### Mathematics

- Winner: Insufficient shared evidence
- Claude Mythos 5.1 public-lane score: Coming soon
- Gemini 3.8 Flash public-lane score: 69.7 (Unranked · 2 rankable rows)

| Benchmark | Claude Mythos 5.1 | Gemini 3.8 Flash | Winner |
|-----------|-----------|-----------|--------|
| FrontierMath v2 (Tiers 1-3) | Coming soon | 68.421% | Coming soon |
| FrontierMath v2 (Tier 4) | Coming soon | 21.951% | Coming soon |

## FAQ

### Is there enough evidence to pick between Claude Mythos 5.1 and Gemini 3.8 Flash?

Not yet. The models share only 1 sourced benchmark row, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [Claude Mythos 5.1 vs Claude Mythos 5](/compare/claude-mythos-5-vs-claude-mythos-5-1)
- [Gemini 3.8 Flash vs Claude Mythos 5](/compare/claude-mythos-5-vs-gemini-3-8-flash)
- [Claude Mythos 5.1 vs Claude Mythos Preview](/compare/claude-mythos-5-1-vs-claude-mythos-preview)
- [Gemini 3.8 Flash vs Claude Mythos Preview](/compare/claude-mythos-preview-vs-gemini-3-8-flash)

## Explore More

- [Claude Mythos 5.1 profile](/models/claude-mythos-5-1)
- [Gemini 3.8 Flash profile](/models/gemini-3-8-flash)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)