GPT-5.1 Codex Max vs Kimi K2 Thinking Turbo
GPT-5.1 Codex Max (2025) and Kimi K2 Thinking Turbo (2025) compare a coding-specialized model against a standalone API model. GPT-5.1 Codex Max ships a not-yet-sourced context window, while Kimi K2 Thinking Turbo ships a 262k-token context window. On pricing, Kimi K2 Thinking Turbo costs $1.15/1M input tokens versus $1.25/1M 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: GPT-5.1 Codex Max is coding-specialized model, while Kimi K2 Thinking Turbo is standalone API model. Choose based on workflow fit before reading any benchmark or price row as decisive.
Decision scorecard
Local evidence first| Signal | GPT-5.1 Codex Max | Kimi K2 Thinking Turbo |
|---|---|---|
| Product type | Coding-specialized model | Standalone API model |
| Best for | custom coding agents, code generation, and tool loops | general production evaluation |
| Decision fit | Coding, Agents, and Vision | Long context |
| Context window | — | 262k |
| Cheapest output | $10/1M tokens | $8/1M tokens |
| Provider routes | 2 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- GPT-5.1 Codex Max has broader tracked provider coverage for fallback and procurement flexibility.
- GPT-5.1 Codex Max uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags GPT-5.1 Codex Max for Coding, Agents, and Vision.
- Kimi K2 Thinking Turbo has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Kimi K2 Thinking Turbo has the lower cheapest tracked output price at $8/1M tokens.
- Local decision data tags Kimi K2 Thinking Turbo for Long context.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
GPT-5.1 Codex Max
$3,500
Cheapest tracked route/tier: OpenRouter
Kimi K2 Thinking Turbo
$2,920
Cheapest tracked route/tier: Vercel AI Gateway
Estimated monthly gap: $580. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
- Kimi K2 Thinking Turbo is $2/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
- Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
- GPT-5.1 Codex Max is $2/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.1 Codex Max adds Vision, Multimodal, and Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-11-19 | 2025-11-06 |
| Context window | — | 262k |
| Parameters | — | 1T (32B active) |
| Architecture | - | - |
| License | Proprietary | MIT(OSI) |
| Openness | Proprietary | Open source |
| Commercial use | Commercial use with conditions | Commercial use allowed |
| Knowledge cutoff | 2024-09 | - |
Pricing and availability
| Pricing attribute | GPT-5.1 Codex Max | Kimi K2 Thinking Turbo |
|---|---|---|
| Input price | $1.25/1M tokens | $1.15/1M tokens |
| Output price | $10/1M tokens | $8/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.1 Codex Max | Kimi K2 Thinking Turbo |
|---|---|---|
| Vision | Yes | No |
| Multimodal | Yes | No |
| Reasoning | Yes | No |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | No |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: GPT-5.1 Codex Max, multimodal input: GPT-5.1 Codex Max, reasoning mode: GPT-5.1 Codex Max, function calling: GPT-5.1 Codex Max, tool use: GPT-5.1 Codex Max, and structured outputs: GPT-5.1 Codex Max. Both models share the core language-model surface, 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, GPT-5.1 Codex Max lists $1.25/1M input and $10/1M output tokens on the cheapest tracked provider, while Kimi K2 Thinking Turbo lists $1.15/1M input and $8/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Kimi K2 Thinking Turbo lower by about $0.67 per million blended tokens. Availability is 2 providers versus 1, so concentration risk also matters.
Choose GPT-5.1 Codex Max when coding workflow support and broader provider choice are central to the workload. Choose Kimi K2 Thinking Turbo when provider fit 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 is cheaper, GPT-5.1 Codex Max or Kimi K2 Thinking Turbo?
Kimi K2 Thinking Turbo is cheaper on tracked token pricing. GPT-5.1 Codex Max costs $1.25/1M input and $10/1M output tokens. Kimi K2 Thinking Turbo costs $1.15/1M input and $8/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GPT-5.1 Codex Max or Kimi K2 Thinking Turbo open source?
GPT-5.1 Codex Max is listed under Proprietary. Kimi K2 Thinking Turbo is listed under MIT. 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, GPT-5.1 Codex Max or Kimi K2 Thinking Turbo?
GPT-5.1 Codex Max has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for multimodal input, GPT-5.1 Codex Max or Kimi K2 Thinking Turbo?
GPT-5.1 Codex Max has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for reasoning mode, GPT-5.1 Codex Max or Kimi K2 Thinking Turbo?
GPT-5.1 Codex Max has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run GPT-5.1 Codex Max and Kimi K2 Thinking Turbo?
GPT-5.1 Codex Max is available on OpenRouter and Vercel AI Gateway. Kimi K2 Thinking Turbo is available on Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-04. Data sourced from public model cards and provider documentation.