# gpt-5.3-codex — API, Pricing & Context Window \\| Vivgrid

gpt-5.3-codex on Vivgrid: OpenAI's Codex-tuned coding model on the Responses API, with a 400K context window and geo-distributed acceleration.

`gpt-5.3-codex` is OpenAI's Codex-optimized coding model, tuned for agentic software engineering: editing files, running tools, and iterating in a loop. It is served on the **Responses API** (`/responses`), the surface that Codex and similar coding CLIs expect.

With a **400K-token context window** and geo-distributed acceleration across **AMER and EMEA**, it delivers low-latency, long-horizon coding sessions on Vivgrid through a single API key.

## Specifications

|     |     |
| --- | --- |
| **Provider** | OpenAI |
| **Model ID** | `gpt-5.3-codex` |
| **Best for** | Coding |
| **Context window** | 400,000 tokens |
| **Max output** | 128,000 tokens |
| **Modalities** | Text, Image |
| **Tool / function calling** | Yes |
| **Knowledge cutoff** | 2025-08 |
| **Acceleration** | ⚡ Geo-Distributed — AMER, EMEA |

## Pricing

Pricing in USD per 1M tokens, matching the provider's rates.

| Input | Cached input | Output |
| --- | --- | --- |
| $1.75 | $0.175 | $14.00 |

## Quick start

Call `gpt-5.3-codex` through Vivgrid's unified, OpenAI-compatible endpoint. Get an API key from the [Vivgrid Console](https://console.vivgrid.com/).

```
curl https://api.vivgrid.com/v1/responses \
  -H "Authorization: Bearer $VIVGRID_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.3-codex",
    "input": "Refactor this function and explain the change.",
    "stream": true
  }'
```

## Ideal use cases

- Codex CLI and other Responses-API coding agents
- Iterative, tool-driven software engineering tasks
- Repository-scale edits within a 400K-token budget
- Pipelines that benefit from streamed, incremental output

## Related models

- [gpt-5.2-codex](/content/docs/models/gpt-5.2-codex/index.html) — the prior Codex generation
- [gpt-5.1-codex-max](/content/docs/models/gpt-5.1-codex-max/index.html) — extended-effort Codex variant
- [gpt-5.5](/content/docs/models/gpt-5.5) — flagship model on the Chat Completions API