LLM Reference

GPT-5.1 Codex vs Kimi K2.6

GPT-5.1 Codex (2025) and Kimi K2.6 (2026) are agentic coding models from OpenAI and Moonshot AI. GPT-5.1 Codex ships a 400k-token context window, while Kimi K2.6 ships a 262k-token context window. On pricing, Kimi K2.6 costs $0.73/1M input tokens versus $1.25/1M 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.

Kimi K2.6 is ~71% cheaper at $0.73/1M; pay for GPT-5.1 Codex only for coding workflow support.

Decision scorecard

Local evidence first
SignalGPT-5.1 CodexKimi K2.6
Best forcustom coding agents, code generation, and tool loopscustom coding agents, code generation, and tool loops
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window400k262k
Cheapest output$10/1M tokens$3.49/1M tokens
Provider routes2 tracked9 tracked
Shared benchmarks0 shared0 shared

Decision tradeoffs

Choose GPT-5.1 Codex when...
  • GPT-5.1 Codex has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • GPT-5.1 Codex uniquely exposes Code execution in local model data.
  • Local decision data tags GPT-5.1 Codex for Coding, RAG, and Agents.
Choose Kimi K2.6 when...
  • Kimi K2.6 has the lower cheapest tracked output price at $3.49/1M tokens.
  • Kimi K2.6 has broader tracked provider coverage for fallback and route flexibility.
  • Kimi K2.6 uniquely exposes Reasoning in local model data.
  • Local decision data tags Kimi K2.6 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 Kimi K2.6

GPT-5.1 Codex

$3,500

Cheapest tracked route/tier: OpenRouter

Kimi K2.6

$1,457

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $2,044. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

GPT-5.1 Codex -> Kimi K2.6
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • Kimi K2.6 is $6.51/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Code execution before moving production traffic.
  • Kimi K2.6 adds Reasoning in local capability data.
Kimi K2.6 -> GPT-5.1 Codex
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • GPT-5.1 Codex is $6.51/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Reasoning before moving production traffic.
  • GPT-5.1 Codex adds Code execution in local capability data.

Specs

Specification
Released2025-12-012026-04-20
Context window400k262k
Parameters—1T
ArchitectureDecoder OnlyMixture of Experts
LicenseProprietaryMITOSI-approved
OpennessProprietaryOpen source
WeightsNot releasedAvailable·Moonshot Modified MIT License
CodeUnknownAvailable·Moonshot Modified MIT License
Commercial useCommercial use: conditionalCommercial use: permitted
Knowledge cutoff2024-092025-04

Pricing and availability

Pricing attributeGPT-5.1 CodexKimi K2.6
Input price$1.25/1M tokens$0.73/1M tokens
Output price$10/1M tokens$3.49/1M tokens
Providers
OpenRouterVercel AI Gateway
Cloudflare Workers AINVIDIA NIMMoonshot AI KimiFireworks AIOpenRouterMicrosoft Foundry

Capabilities

CapabilityGPT-5.1 CodexKimi K2.6
VisionYesYes
MultimodalYesYes
ReasoningNoYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesNo
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

No shared benchmark scores are currently available for this pair.

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