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Codex context management: setup and usage

Open your Codex config.toml and add this line at the top, before any [section] headers:

features.context_management.experimental_mode = true

Save, restart Codex, and start a new task. If the setting already exists, change it to true instead of adding it again. Official instructions

Where to find the file

The default paths are:

  • macOS / Linux: ~/.codex/config.toml
  • Windows: %USERPROFILE%\.codex\config.toml

In the IDE extension, open the gear menu and select Codex Settings → Open config.toml. You can create a missing file yourself; make sure it is not saved as config.toml.txt. If you use a custom configuration directory, check the location your client actually reads. Configuration docs

If the file already has a [features.context_management] section, edit it there:

[features.context_management]
experimental_mode = true

Use one form, not both. Pasting the full dotted setting beneath an unrelated section header makes it part of that section.

What it does

During long tasks, Codex normally needs to compact earlier conversation into a summary. This experiment uses notes and history search: it carries key details across context windows and can look up earlier messages and tool results from the same task. Feature reference

It is worth considering if you regularly run longer tasks that revisit earlier decisions. For a few questions or a small edit, there is little reason to change your setup just for this.

The model guide describes GPT-6 Astra with ChatGPT Plus / Pro and excludes Business and Enterprise at launch. The configuration reference also lists Pro Lite. The descriptions differ, so check availability for your account and client. Minimum client versions have not been verified here. Model guide, configuration reference

If nothing changes

Check these first:

  • Your sign-in method and client support the feature.
  • The setting is in the right section and is not duplicated.
  • Project settings, a profile, or CLI options are not overriding it. Configuration precedence
  • You restarted and created a new task.

A successful startup does not prove activation. We confirmed window transitions in the enabled test through runtime records; remembering an earlier detail alone is not proof. We also found that CLI 0.150.1 rejects this setting while 0.153.3 recognizes it. This does not establish 0.153.3 as the minimum supported version.

To turn it off, change the existing true to false, restart, and start a new task. See the Codex FAQ for other questions.

Updated 2026-09-05