speed.md Codex Docs, 2026-03-18 00:36 UTC → 2026-05-07 17:08 UTC

5Codex offers the ability to increase the speed of the model for increased5Codex offers the ability to increase the speed of the model for increased

6credit consumption.6credit consumption.

7 7 

8Fast mode is currently supported on GPT-5.4. When enabled, speed is increased8Fast mode increases supported model speed by 1.5x and consumes credits at a

9by 1.5x and credits are consumed at a 2x rate.9higher rate than Standard mode. It currently supports GPT-5.5 and GPT-5.4,

10 10consuming credits at 2.5x the Standard rate for GPT-5.5 and 2x the Standard

11Enable it by typing `/fast`. It’s available in Codex IDE Extensions, Codex11rate for GPT-5.4.

12CLI, and the Codex app when you sign in with ChatGPT. With an API key, Codex12 

13uses standard API pricing instead and you can’t use `/fast`.13Use `/fast on`, `/fast off`, or `/fast status` in the CLI to change or inspect

14 14the current setting. You can also persist the default with `service_tier =

15[15"fast"` plus `[features].fast_mode = true` in `config.toml`. Fast mode is

16Your browser does not support the video tag.16available in the Codex IDE extension, Codex CLI, and the Codex app when you

17](/videos/codex/fast-mode-demo.mp4)17sign in with ChatGPT. With an API key, Codex uses standard API pricing instead

18and you can't use Fast mode credits.

19 

20<VideoPlayer

21 src="/videos/codex/fast-mode-demo.mp4"

22 class="[&_video]:mx-auto [&_video]:max-h-[400px] [&_video]:max-w-full [&_video]:w-auto"

23/>

18 24 

19## Codex-Spark25## Codex-Spark

20 26 

21GPT-5.3-Codex-Spark is a separate fast, less-capable Codex model optimized for near-instant, real-time coding iteration. Unlike fast mode, which speeds up GPT-5.4 at a higher credit rate,27GPT-5.3-Codex-Spark is a separate fast, less-capable Codex model optimized for

22Codex-Spark is its own model choice and has its own usage limits.28near-instant, real-time coding iteration. Unlike fast mode, which speeds up a

29supported model at a higher credit rate, Codex-Spark is its own model choice

30and has its own usage limits.

23 31 

24During research preview Codex-Spark is only available for ChatGPT Pro subscribers.32During research preview Codex-Spark is only available for ChatGPT Pro subscribers.