GPT-5.3-Codex vs Kimi K3
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for GPT-5.3-Codex and Kimi K3.
GPT-5.3-Codex
GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2. It achieves state-of-the-art results...
Kimi K3
Kimi K3 is an ultra-large-scale, open-weight multimodal reasoning model from Moonshot AI. It is suited for complex coding, knowledge work, and long-horizon agentic workflows, and is particularly strong at navigating...
Technical Specifications
| Specification | GPT-5.3-Codex | Kimi K3 |
|---|---|---|
| Provider | OpenAI | Moonshot AI |
| Context Window | 400,000 tokens | 1,048,576 tokens |
| Agent Suitability | N/A | N/A |
| Time to First Token (TTFT) | N/A | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | beta |
| API Available | Yes | Yes |
| Released Date | 2026-02-24 | 2026-07-16 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.3-Codex
$1.75
Kimi K3
$3.00
Output Price per Million Tokens
GPT-5.3-Codex
$14.00
Kimi K3
$15.00
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
GPT-5.3-Codex Quirks & Gotchas
No developer gotchas reported.
Kimi K3 Quirks & Gotchas
No developer gotchas reported.