Feature: forward extra args (custom model_provider / profile) to every codex launch #418

Problem

Today the plugin only forwards --model and --effort to Codex, and the app-server is always spawned as a bare codex app-server (see plugins/codex/scripts/lib/app-server.mjs). There is no way to pass Codex global overrides such as:

• -c model_provider=<id> to select a custom provider
• --profile <name>
• other -c key=value config overrides

The only workaround is editing ~/.codex/config.toml / .codex/config.toml, which is awkward when you want a plugin-specific provider (e.g. routing the plugin through a LiteLLM/proxy provider) without changing your global Codex defaults.

Proposed solution

Add a CODEX_PLUGIN_CC_ARGS environment variable. When set, its value is tokenized (shell-style) and prepended to every codex invocation the plugin makes — the app-server runtime spawn and the availability checks. For example:

export CODEX_PLUGIN_CC_ARGS='-c model_provider=litellm'

results in the plugin running codex -c model_provider=litellm app-server.

This keeps the change opt-in, requires no per-command flags, and reuses Codex's own config-override surface.

Notes

• Read at runtime start; a session that already has a shared runtime needs a fresh session for new values to take effect.
• I have an implementation ready and will open a PR referencing this issue.