speed.md Codex Docs, 2026-04-16 18:31 UTC → 2026-05-12 01:59 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,

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

11rate for GPT-5.4.

10 12 

11Use `/fast on`, `/fast off`, or `/fast status` in the CLI to change or inspect13Use `/fast on`, `/fast off`, or `/fast status` in the CLI to change or inspect

12the current setting. You can also persist the default with `service_tier = "fast"` plus `[features].fast_mode = true` in `config.toml`. Fast mode is14the current setting. You can also persist the default with `service_tier =

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

13available in the Codex IDE extension, Codex CLI, and the Codex app when you16available in the Codex IDE extension, Codex CLI, and the Codex app when you

14sign in with ChatGPT. With an API key, Codex uses standard API pricing instead17sign in with ChatGPT. With an API key, Codex uses standard API pricing instead

15and you can't use Fast mode credits.18and you can't use Fast mode credits.

16 19 

17[20<VideoPlayer

18Your browser does not support the video tag.21 src="/videos/codex/fast-mode-demo.mp4"

19](/videos/codex/fast-mode-demo.mp4)22 class="[&_video]:mx-auto [&_video]:max-h-[400px] [&_video]:max-w-full [&_video]:w-auto"

23/>

20 24 

21## Codex-Spark25## Codex-Spark

22 26 

23GPT-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

24Codex-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.

25 31 

26During research preview Codex-Spark is only available for ChatGPT Pro subscribers.32During research preview Codex-Spark is only available for ChatGPT Pro subscribers.