Claude Mythos Preview vs Gemini 3 Flash Preview
Claude Mythos Preview (2026) and Gemini 3 Flash Preview (2025) are frontier reasoning models from Anthropic and Google DeepMind. Both ship a 1M-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 18.5 pts. On pricing, Gemini 3 Flash Preview costs $0.50/1M input tokens versus $25/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3 Flash Preview is ~4900% cheaper at $0.50/1M; pay for Claude Mythos Preview only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | Gemini 3 Flash Preview |
|---|---|---|
| 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 | 3 tracked |
| Shared benchmarks | SWE-bench Verified leader | 2 shared |
Decision tradeoffs
- Claude Mythos Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 18.5 points.
- Claude Mythos Preview uniquely exposes Reasoning in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Gemini 3 Flash Preview has the lower cheapest tracked output price at $3/1M tokens.
- Gemini 3 Flash Preview has broader tracked provider coverage for fallback and route flexibility.
- Local decision data tags Gemini 3 Flash Preview 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 Preview
$1,150
Cheapest tracked route/tier: GCP Vertex AI
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 Preview; plan for SDK, billing, or endpoint changes.
- Gemini 3 Flash Preview is $122/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for Gemini 3 Flash Preview 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 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 |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Restricted | Restricted |
| Knowledge cutoff | 2025-12 | 2025-01 |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | Gemini 3 Flash Preview |
|---|---|---|
| Input price | $25/1M tokens | $0.50/1M tokens |
| Output price | $125/1M tokens | $3/1M tokens |
| Providers |
Capabilities
| Capability | Claude Mythos Preview | Gemini 3 Flash Preview |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | No |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Mythos Preview | Gemini 3 Flash Preview |
|---|---|---|
| SWE-bench Verified | 93.9 | 75.4 |
| Google-Proof Q&A | 94.6 | 89.4 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Claude Mythos Preview at 93.9 and Gemini 3 Flash Preview at 75.4, with Claude Mythos Preview ahead by 18.5 points; Google-Proof Q&A has Claude Mythos Preview at 94.6 and Gemini 3 Flash Preview at 89.4, with Claude Mythos Preview ahead by 5.2 points. The largest visible gap is 18.5 points on SWE-bench Verified, 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. Both models share vision, multimodal input, JSON / Tool use, and JSON / 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 listed provider, while Gemini 3 Flash Preview lists $0.50/1M input and $3/1M output tokens on the cheapest listed provider. A 70/30 input-output blend puts Gemini 3 Flash Preview lower by about $53.75 per million blended tokens. Availability is 2 providers versus 3, so concentration risk also matters.
Choose Claude Mythos Preview when coding workflow support are central to the workload. Choose Gemini 3 Flash Preview when coding workflow support, lower 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 Preview?
Claude Mythos Preview supports 1M tokens, while Gemini 3 Flash Preview 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 Preview?
Gemini 3 Flash Preview is cheaper on listed token pricing. Claude Mythos Preview costs $25/1M input and $125/1M output tokens. Gemini 3 Flash Preview costs $0.50/1M input and $3/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Mythos Preview or Gemini 3 Flash Preview open source?
Claude Mythos Preview is listed under Proprietary. Gemini 3 Flash Preview 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 Preview?
Both Claude Mythos Preview and Gemini 3 Flash Preview 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 Preview?
Both Claude Mythos Preview and Gemini 3 Flash Preview 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 Preview?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. Gemini 3 Flash Preview is available on GCP Vertex AI, OpenRouter, and Google AI Studio. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-10-17. Data sourced from public model cards and provider documentation.