Claude Mythos Preview vs GPT-5.2 Codex
Claude Mythos Preview (2026) and GPT-5.2 Codex (2025) are agentic coding models from Anthropic and OpenAI. Claude Mythos Preview ships a 1M-token context window, while GPT-5.2 Codex ships a not-yet-sourced context window. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing. The goal is to make the tradeoff clear before deeper testing.
Claude Mythos Preview is safer overall; choose GPT-5.2 Codex when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Claude Mythos Preview | GPT-5.2 Codex |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, Agents, and Vision |
| Context window | 1M | — |
| Cheapest output | $125/1M tokens | - |
| Provider routes | 2 tracked | 0 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Claude Mythos Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Claude Mythos Preview has broader tracked provider coverage for fallback and procurement flexibility.
- Claude Mythos Preview uniquely exposes Structured outputs in local model data.
- Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
- Local decision data tags GPT-5.2 Codex for Coding, Agents, and Vision.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Claude Mythos Preview
$51,250
Cheapest tracked route: Anthropic
GPT-5.2 Codex
Unavailable
No complete token price in local provider data
Cost delta unavailable until both models have sourced input and output token prices.
Switch friction
- No overlapping tracked provider route is sourced for Claude Mythos Preview and GPT-5.2 Codex; plan for SDK, billing, or endpoint changes.
- Check replacement coverage for Structured outputs before moving production traffic.
- No overlapping tracked provider route is sourced for GPT-5.2 Codex and Claude Mythos Preview; plan for SDK, billing, or endpoint changes.
- Claude Mythos Preview adds Structured outputs in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-04-07 | 2025-12-18 |
| Context window | 1M | — |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-12 | - |
Pricing and availability
| Pricing attribute | Claude Mythos Preview | GPT-5.2 Codex |
|---|---|---|
| Input price | $25/1M tokens | - |
| Output price | $125/1M tokens | - |
| Providers | - |
Capabilities
| Capability | Claude Mythos Preview | GPT-5.2 Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | No |
| Code execution | Yes | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on structured outputs: Claude Mythos Preview. Both models share vision, multimodal input, reasoning mode, and function calling, 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.
Pricing coverage is uneven: Claude Mythos Preview has $25/1M input tokens and GPT-5.2 Codex has no token price sourced yet. Provider availability is 2 tracked routes versus 0. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose Claude Mythos Preview when coding workflow support and broader provider choice are central to the workload. Choose GPT-5.2 Codex when coding workflow support are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency. For teams standardizing a stack, that distinction is often the difference between a benchmark win and a reliable deployment.
FAQ
Is Claude Mythos Preview or GPT-5.2 Codex open source?
Claude Mythos Preview is listed under Proprietary. GPT-5.2 Codex 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 GPT-5.2 Codex?
Both Claude Mythos Preview and GPT-5.2 Codex expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Claude Mythos Preview or GPT-5.2 Codex?
Both Claude Mythos Preview and GPT-5.2 Codex expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for reasoning mode, Claude Mythos Preview or GPT-5.2 Codex?
Both Claude Mythos Preview and GPT-5.2 Codex expose reasoning mode. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for function calling, Claude Mythos Preview or GPT-5.2 Codex?
Both Claude Mythos Preview and GPT-5.2 Codex expose function calling. 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 GPT-5.2 Codex?
Claude Mythos Preview is available on Anthropic and Microsoft Foundry. GPT-5.2 Codex is available on the tracked providers still being sourced. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-16. Data sourced from public model cards and provider documentation.