LLM Reference

Claude Mythos Preview vs GPT-5.2 Codex

Claude Mythos Preview (2026) and GPT-5.2 Codex (2025) compare a standalone API model against a coding-specialized model. Claude Mythos Preview ships a 1m-token context window, while GPT-5.2 Codex ships a 400k-token context window. On SWE-bench Verified, Claude Mythos Preview leads by 21.1 pts. On pricing, GPT-5.2 Codex costs $1.75/1M input tokens versus $25/1M for the alternative. This page treats the result as workflow and deployment fit, not a universal model winner.

Treat this as a product-type comparison: Claude Mythos Preview is standalone API model, while GPT-5.2 Codex is coding-specialized model. Choose based on workflow fit before reading any benchmark or price row as decisive.

Decision scorecard

Local evidence first
SignalClaude Mythos PreviewGPT-5.2 Codex
Product typeStandalone API modelCoding-specialized model
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentscustom coding agents, code generation, and tool loops
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m400k
Cheapest output$125/1M tokens$14/1M tokens
Provider routes2 tracked2 tracked
Shared benchmarksSWE-bench Verified leader1 shared

Decision tradeoffs

Choose Claude Mythos Preview when...
  • Claude Mythos Preview holds a shared-benchmark lead on SWE-bench Verified, ahead by 21.1 points.
  • Claude Mythos Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • Local decision data tags Claude Mythos Preview for Coding, RAG, and Agents.
Choose GPT-5.2 Codex when...
  • GPT-5.2 Codex has the lower cheapest tracked output price at $14/1M tokens.
  • Local decision data tags GPT-5.2 Codex 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.

Lower estimate GPT-5.2 Codex

Claude Mythos Preview

$51,250

Cheapest tracked route/tier: Anthropic

GPT-5.2 Codex

$4,900

Cheapest tracked route/tier: Vercel AI Gateway

Estimated monthly gap: $46,350. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Mythos Preview -> GPT-5.2 Codex
  • No overlapping tracked provider route is sourced for Claude Mythos Preview and GPT-5.2 Codex; plan for SDK, billing, or endpoint changes.
  • GPT-5.2 Codex is $111/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
GPT-5.2 Codex -> Claude Mythos Preview
  • 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 is $111/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.

Specs

Specification
Released2026-05-012025-12-18
Context window1m400k
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-122025-08

Pricing and availability

Pricing attributeClaude Mythos PreviewGPT-5.2 Codex
Input price$25/1M tokens$1.75/1M tokens
Output price$125/1M tokens$14/1M tokens
Providers
AnthropicMicrosoft Foundry
Vercel AI GatewayOpenAI API

Capabilities

CapabilityClaude Mythos PreviewGPT-5.2 Codex
VisionYesYes
MultimodalYesYes
ReasoningYesYes
Function callingYesYes
Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Mythos PreviewGPT-5.2 Codex
SWE-bench Verified93.972.8

Deep dive

On shared benchmark coverage, SWE-bench Verified has Claude Mythos Preview at 93.9 and GPT-5.2 Codex at 72.8, with Claude Mythos Preview ahead by 21.1 points. The largest visible gap is 21.1 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 is close: both models cover vision, multimodal input, reasoning mode, function calling, and tool use. That makes context budget, benchmark fit, and provider maturity more important than a simple checklist. If your application depends on one integration detail, verify it against the provider route you plan to use, not just the base model listing.

For cost, Claude Mythos Preview lists $25/1M input and $125/1M output tokens on the cheapest tracked provider, while GPT-5.2 Codex lists $1.75/1M input and $14/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts GPT-5.2 Codex lower by about $49.58 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.

Choose Claude Mythos Preview when coding workflow support and larger context windows are central to the workload. Choose GPT-5.2 Codex when coding workflow support and lower input-token cost 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 GPT-5.2 Codex?

Claude Mythos Preview supports 1m tokens, while GPT-5.2 Codex supports 400k 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 GPT-5.2 Codex?

GPT-5.2 Codex is cheaper on tracked token pricing. Claude Mythos Preview costs $25/1M input and $125/1M output tokens. GPT-5.2 Codex costs $1.75/1M input and $14/1M output tokens. Provider discounts or batch pricing can still change the final bill.

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.

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 Vercel AI Gateway and OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.

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Last reviewed: 2026-06-30. Data sourced from public model cards and provider documentation.