Constant CODEX_TOOL_FEATURES 

const CODEX_TOOL_FEATURES: &[&str];

Codex features that each add a tool to the model’s request. /btw disables every one of them. Checked against the pinned CLI (0.154.0, codex features list) by capturing the request it sends: with these off, plus --ignore-user-config and web_search="disabled", the only tool left is request_user_input, which exec mode refuses to run (“request_user_input is not supported in exec mode”).