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Specifications
Specifications and pricing as served by Composite
Model ID
openai/gpt-5.3-codex:fast-reasoning
Provider
Azure
Context window
400,000 tokens
Accepts
text, image, file
Returns
text
Input price
$2.19 per million tokens
Output price
$17.5 per million tokens
Prompt caching
Supported — cached input is billed at the provider's cache rate, on credits and plans alike
Web search
$0.0125 per result
Thinking
Optional - see "OpenAI: GPT-5.3-Codex (fast) (Reasoning) (Reasoning)" in the catalog to turn it on by default
Moderated
Yes - by the provider
Cost on a monthly plan
About 28 plan credits per typical call (8k in, 1k out)
Routing endpoints
1
Use OpenAI: GPT-5.3-Codex (fast) (Reasoning) in JanitorAI or SillyTavern
Make a Composite API key and type openai/gpt-5.3-codex:fast-reasoning as the model name. JanitorAI takes the full URL https://composite.lucidity.sh/v1/chat/completions; SillyTavern, ChubAI, Agnai and RisuAI take https://composite.lucidity.sh/v1. It runs on credits, a plan, or your own provider key.
This model has not carried enough traffic on Composite yet to publish a success rate, a latency figure or a traffic rank. The numbers appear here once it has.
Pricing
$2.19 per million tokens input · $17.5 per million tokens output
Credits pay the provider’s price plus 25%; cache hits cost less.
On a monthly plan, a typical call (8k tokens in, 1k out) uses about 28 plan credits, at the provider's own price.
Provider
Azure
Roleplay fit
This is an OpenAI model, a dependable baseline with broad instruction-following and consistent formatting across long conversations.
Context behavior
With a 400,000-token context window, it can hold a long-running roleplay or a full lorebook in memory without losing earlier plot details, so it suits multi-session campaigns and character cards with heavy backstory.
Cost for regular use
It sits in the mid-range on price, a reasonable pick for regular roleplay use without going for the cheapest option available.
From the provider
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...