speed.md Codex Docs, 2026-03-09 00:34 UTC → 2026-05-02 06:45 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.

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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.

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11Enable it by typing `/fast`. It’s available in Codex IDE Extensions, Codex13Use `/fast on`, `/fast off`, or `/fast status` in the CLI to change or inspect

12CLI, and the Codex app when you sign in with ChatGPT. With an API key, Codex14the current setting. You can also persist the default with `service_tier = "fast"` plus `[features].fast_mode = true` in `config.toml`. Fast mode is

13uses standard API pricing instead and you can’t use `/fast`.15available in the Codex IDE extension, Codex CLI, and the Codex app when you

16sign in with ChatGPT. With an API key, Codex uses standard API pricing instead

17and you can't use Fast mode credits.

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16Your browser does not support the video tag.20Your browser does not support the video tag.

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19## Codex-Spark23## Codex-Spark

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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,25GPT-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.26near-instant, real-time coding iteration. Unlike fast mode, which speeds up a

27supported model at a higher credit rate, Codex-Spark is its own model choice

28and has its own usage limits.

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24During research preview Codex-Spark is only available for ChatGPT Pro subscribers.30During research preview Codex-Spark is only available for ChatGPT Pro subscribers.