GPT-5.3-Codex vs Kimi K2.6
GPT-5.3-Codex (2026) and Kimi K2.6 (2026) are agentic coding models from OpenAI and Moonshot AI. GPT-5.3-Codex ships a not-yet-sourced context window, while Kimi K2.6 ships a 262K-token context window. On SWE-bench Verified, GPT-5.3-Codex leads by 4.8 pts. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Kimi K2.6 is safer overall; choose GPT-5.3-Codex when coding workflow support matters.
Specs
| Released | 2026-02-05 | 2026-04-13 |
| Context window | — | 262K |
| Parameters | — | 1T (MoE, 32B active) |
| Architecture | decoder only | Mixture of Experts (MoE) |
| License | Proprietary | Proprietary |
| Knowledge cutoff | - | - |
Pricing and availability
| GPT-5.3-Codex | Kimi K2.6 | |
|---|---|---|
| Input price | $1.75/1M tokens | - |
| Output price | $14/1M tokens | - |
| Providers |
Capabilities
| GPT-5.3-Codex | Kimi K2.6 | |
|---|---|---|
| Vision | ||
| Multimodal | ||
| Reasoning | ||
| Function calling | ||
| Tool use | ||
| Structured outputs | ||
| Code execution |
Benchmarks
| Benchmark | GPT-5.3-Codex | Kimi K2.6 |
|---|---|---|
| SWE-bench Verified | 85.0 | 80.2 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has GPT-5.3-Codex at 85 and Kimi K2.6 at 80.2, with GPT-5.3-Codex ahead by 4.8 points. The largest visible gap is 4.8 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 vision: Kimi K2.6, reasoning mode: Kimi K2.6, tool use: GPT-5.3-Codex, structured outputs: GPT-5.3-Codex, and code execution: GPT-5.3-Codex. Both models share multimodal input 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: GPT-5.3-Codex has $1.75/1M input tokens and Kimi K2.6 has no token price sourced yet. Provider availability is 1 tracked routes versus 2. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose GPT-5.3-Codex when coding workflow support are central to the workload. Choose Kimi K2.6 when coding workflow support 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
Is GPT-5.3-Codex or Kimi K2.6 open source?
GPT-5.3-Codex is listed under Proprietary. Kimi K2.6 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, GPT-5.3-Codex or Kimi K2.6?
Kimi K2.6 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. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, GPT-5.3-Codex or Kimi K2.6?
Both GPT-5.3-Codex and Kimi K2.6 expose multimodal input. 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 reasoning mode, GPT-5.3-Codex or Kimi K2.6?
Kimi K2.6 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.
Which is better for function calling, GPT-5.3-Codex or Kimi K2.6?
Both GPT-5.3-Codex and Kimi K2.6 expose function calling. 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.
Where can I run GPT-5.3-Codex and Kimi K2.6?
GPT-5.3-Codex is available on OpenRouter. Kimi K2.6 is available on NVIDIA NIM and Moonshot AI Kimi. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Continue comparing
Last reviewed: 2026-04-27. Data sourced from public model cards and provider documentation.