GPT-5.3 Codex

Premium

OpenAICodinggpt-5.3-codex

OpenAI’s most capable agentic coding model.

Capabilities

Tool callingVisionJSON modePrompt cache

Recommended for

agentic coding
code generation
repo-scale refactoring

Using this model through Conduix

Call it by its id, or let a routing alias pick it as part of a governed, cross-provider chain with automatic failover.

Direct model idgpt-5.3-codex

Reached by these routing aliases:

code-premiumprimary pick · GPT-5.3 Codex → Claude Opus 4.8 → Claude Sonnet 5
code-balancedfallback #1 · Claude Sonnet 5 → GPT-5.3 Codex → Codestral
agentic-codeprimary pick · GPT-5.3 Codex → Claude Sonnet 5 → Kimi K2.7 Code (Together)

Routing relationships are operational — chains adapt to provider availability and your org's policy — not a contractual guarantee that a specific model serves a given request.

Get started

Conduix is OpenAI-API-compatible — point any OpenAI SDK at https://api.conduix.ai/v1 and pass gpt-5.3-codex as the model.

from conduix import Conduix

client = Conduix(api_key="cx_live_YOUR_KEY")  # base URL is built in

response = client.chat.completions.create(
    model="gpt-5.3-codex",
    messages=[{"role": "user", "content": "Hello, Conduix!"}],
)
print(response.choices[0].message.content)

Tool calling: Pass a tools array and the model calls your functions.
Vision: Accepts image inputs — add image_url parts to a message.
JSON mode: Set response_format for guaranteed-valid JSON output.
Prompt cache: Repeated prompt context is billed at a reduced rate.

The response's x-conduix-model-served header tells you exactly which model answered. See the quickstart for keys, headers, and usage.