bug: codex module ignores CODEX_HOME when writing configuration

[Edd88-pixel]

Current Behavior

The coder-labs/codex module writes its configuration to $HOME/.codex/config.toml, even when CODEX_HOME points to another directory.

Codex reads its user configuration from $CODEX_HOME/config.toml. As a result, the module can finish successfully while writing settings that the CLI does not use. This affects workspaces that store Codex state in a custom or persistent directory: the module's model settings, MCP servers, trusted projects and AI Gateway configuration are written to the wrong location.

Steps to Reproduce

1. Set CODEX_HOME=/home/coder/state/codex in the environment used by both the module's install script and the Codex CLI.
2. Create that directory and a config.toml containing model_reasoning_effort = "high".
3. Configure the module with base_config_toml = "model_reasoning_effort = \"medium\"" and start the workspace.
4. Check both configuration files: $HOME/.codex/config.toml contains the module's medium setting, while $CODEX_HOME/config.toml still contains high.

Expected Behavior

The module should write its configuration under CODEX_HOME when it is set to a non-empty value, and use $HOME/.codex otherwise.

Currently, populate_config_toml() hardcodes the default path rather than following Codex's configuration directory.

[linear-code]

REG-124

[matifali]

Is this a documented upstream behavior? Does codex CLI support that?

[Edd88-pixel]

Yes, the CLI supports it. The official docs confirm that CODEX_HOME controls where Codex reads config.toml, defaulting to ~/.codex. Our module currently hardcodes that default path

[kdcokenny]

hey @Edd88-pixel, are you working on this? happy to pick it up if not

[Edd88-pixel]

Hey @kdcokenny, feel free to pick it up!