Claude Mythos Preview vs Gemini 3 Flash
Claude Mythos Preview (2026) and Gemini 3 Flash (2025) are frontier reasoning models from Anthropic and Google DeepMind. Claude Mythos Preview ships a 1m-token context window, while Gemini 3 Flash ships a 1m-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 15.9 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Claude Mythos Preview is safer overall; choose Gemini 3 Flash when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Gemini 3 Flash |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | multimodal apps, tool-calling agents, and long-context analysis |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 1m |
| Cheapest output | $125/1M tokens | $3/1M tokens |
| Provider routes | 2 tracked | 4 tracked |
| Shared benchmarks | SWE-bench Verified leader | 3 shared |
Decision tradeoffs
- Claude Mythos Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 15.9 points.
- Claude Mythos Preview uniquely exposes Reasoning and Structured outputs in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Gemini 3 Flash has the lower cheapest tracked output price at $3/1M tokens.
- Gemini 3 Flash has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Gemini 3 Flash for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Mythos Preview
$51,250
Cheapest tracked route/tier: Anthropic
Gemini 3 Flash
$1,150
Cheapest tracked route/tier: Replicate API
Estimated monthly gap: $50,100. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Claude Mythos Preview and Gemini 3 Flash; plan for SDK, billing, or endpoint changes.
- Gemini 3 Flash is $122/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning and Structured outputs before moving production traffic.
- No overlapping tracked provider route is sourced for Gemini 3 Flash and Claude Mythos Preview; plan for SDK, billing, or endpoint changes.
- Claude Mythos Preview is $122/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Mythos Preview adds Reasoning and Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-01 | 2025-12-17 |
| Context window | 1m | 1m |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-12 | 2025-01 |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | Gemini 3 Flash |
|---|---|---|
| Input price | $25/1M tokens |
|
| Output price | $125/1M tokens |
|
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Gemini 3 Flash |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | No |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | No |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Mythos Preview | Gemini 3 Flash |
|---|---|---|
| SWE-bench Verified | 93.9 | 78.0 |
| Google-Proof Q&A | 94.6 | 90.4 |
| τ-bench | 89.2 | 71.5 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Claude Mythos Preview at 93.9 and Gemini 3 Flash at 78, with Claude Mythos Preview ahead by 15.9 points; Google-Proof Q&A has Claude Mythos Preview at 94.6 and Gemini 3 Flash at 90.4, with Claude Mythos Preview ahead by 4.2 points; τ-bench has Claude Mythos Preview at 89.2 and Gemini 3 Flash at 71.5, with Claude Mythos Preview ahead by 17.7 points. The largest visible gap is 17.7 points on τ-bench, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on reasoning mode: Claude Mythos Preview and structured outputs: Claude Mythos Preview. Both models share vision, multimodal input, function calling, and tool use, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Claude Mythos Preview lists $25/1M input and $125/1M output tokens on the cheapest tracked provider, while Gemini 3 Flash lists tiered pricing: 0-200,001t is $0.50/1M input and $3/1M output; 200,001t+ is $0.50/1M input and $3/1M output. A 70/30 input-output blend puts Gemini 3 Flash lower by about $53.75 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 2 providers versus 4, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support are central to the workload. Choose Gemini 3 Flash when coding workflow support, lower cheapest-tier input-token cost, and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Claude Mythos Preview or Gemini 3 Flash?
Claude Mythos Preview supports 1m tokens, while Gemini 3 Flash supports 1m tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Claude Mythos Preview or Gemini 3 Flash?
Claude Mythos Preview lists $25/1M input and $125/1M output tokens on the cheapest tracked provider. Gemini 3 Flash lists tiered pricing: 0-200,001t is $0.50/1M input and $3/1M output; 200,001t+ is $0.50/1M input and $3/1M output. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Gemini 3 Flash open source?
Claude Mythos Preview is listed under Proprietary. Gemini 3 Flash is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Claude Mythos Preview or Gemini 3 Flash?
Both Claude Mythos Preview and Gemini 3 Flash expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Claude Mythos Preview or Gemini 3 Flash?
Both Claude Mythos Preview and Gemini 3 Flash expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Claude Mythos Preview and Gemini 3 Flash?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Gemini 3 Flash is available on Replicate API, GCP Vertex AI, Google AI Studio, and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-06-15. Data sourced from public model cards and provider documentation.