Add codex update command (#19933)

## Why

Addresses #9274

Running `codex update` currently starts an interactive Codex session
with `update` as the prompt. That is a rough edge for users who expect a
direct self-update command after seeing the existing update notice, and
it forces them to copy the suggested package-manager command manually.

## What changed

- Added a top-level `codex update` subcommand.
- Reused the existing install-channel detection and update command
runner that the TUI already uses for update prompts.
- Exposed the update-action lookup from `codex-tui` so the CLI can
invoke the same behavior.
- Added CLI coverage to ensure `codex update` is parsed as a subcommand
instead of becoming an interactive prompt.

## Verification

- `cargo test -p codex-cli`
- `cargo test -p codex-tui update_action::tests`

codex-rs/cli/src/main.rs

@@ -134,6 +134,9 @@ enum Subcommand {
     /// Generate shell completion scripts.
     Completion(CompletionCommand),
 
+    /// Update Codex to the latest version.
+    Update,
+
     /// Run commands within a Codex-provided sandbox.
     Sandbox(SandboxArgs),
 
@@ -615,6 +618,25 @@ fn run_update_action(action: UpdateAction) -> anyhow::Result<()> {
     Ok(())
 }
 
+fn run_update_command() -> anyhow::Result<()> {
+    #[cfg(debug_assertions)]
+    {
+        anyhow::bail!(
+            "`codex update` is not available in debug builds. Install a release build of Codex to use this command."
+        );
+    }
+
+    #[cfg(not(debug_assertions))]
+    {
+        let Some(action) = codex_tui::get_update_action() else {
+            anyhow::bail!(
+                "Could not detect the Codex installation method. Please update manually: https://developers.openai.com/codex/cli/"
+            );
+        };
+        run_update_action(action)
+    }
+}
+
 fn run_execpolicycheck(cmd: ExecPolicyCheckCommand) -> anyhow::Result<()> {
     cmd.run()
 }
@@ -998,6 +1020,14 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
             )?;
             print_completion(completion_cli);
         }
+        Some(Subcommand::Update) => {
+            reject_remote_mode_for_subcommand(
+                root_remote.as_deref(),
+                root_remote_auth_token_env.as_deref(),
+                "update",
+            )?;
+            run_update_command()?;
+        }
         Some(Subcommand::Cloud(mut cloud_cli)) => {
             reject_remote_mode_for_subcommand(
                 root_remote.as_deref(),
@@ -1890,6 +1920,12 @@ mod tests {
         assert!(matches!(cli.subcommand, Some(Subcommand::Plugin(_))));
     }
 
+    #[test]
+    fn update_parses_as_update_subcommand() {
+        let cli = MultitoolCli::try_parse_from(["codex", "update"]).expect("parse");
+        assert!(matches!(cli.subcommand, Some(Subcommand::Update)));
+    }
+
     #[test]
     fn plugin_marketplace_remove_parses_under_plugin() {
         let cli =

codex-rs/cli/tests/marketplace_upgrade.rs

@@ -30,7 +30,7 @@ async fn marketplace_upgrade_no_longer_runs_at_top_level() -> Result<()> {
         .args(["marketplace", "upgrade"])
         .assert()
         .failure()
-        .stderr(contains("unexpected argument 'upgrade' found"));
+        .stderr(contains("unrecognized subcommand 'upgrade'"));
 
     Ok(())
 }

codex-rs/cli/tests/update.rs

@@ -0,0 +1,24 @@
+use anyhow::Result;
+use predicates::str::contains;
+use std::path::Path;
+use tempfile::TempDir;
+
+fn codex_command(codex_home: &Path) -> Result<assert_cmd::Command> {
+    let mut cmd = assert_cmd::Command::new(codex_utils_cargo_bin::cargo_bin("codex")?);
+    cmd.env("CODEX_HOME", codex_home);
+    Ok(cmd)
+}
+
+#[cfg(debug_assertions)]
+#[tokio::test]
+async fn update_does_not_start_interactive_prompt() -> Result<()> {
+    let codex_home = TempDir::new()?;
+
+    codex_command(codex_home.path())?
+        .arg("update")
+        .assert()
+        .failure()
+        .stderr(contains("`codex update` is not available in debug builds"));
+
+    Ok(())
+}

codex-rs/tui/src/lib.rs

@@ -171,6 +171,8 @@ mod tui;
 mod ui_consts;
 pub(crate) mod update_action;
 pub use update_action::UpdateAction;
+#[cfg(not(debug_assertions))]
+pub use update_action::get_update_action;
 mod update_prompt;
 #[cfg(any(not(debug_assertions), test))]
 mod update_versions;

codex-rs/tui/src/update_action.rs

@@ -59,7 +59,7 @@ impl UpdateAction {
 }
 
 #[cfg(not(debug_assertions))]
-pub(crate) fn get_update_action() -> Option<UpdateAction> {
+pub fn get_update_action() -> Option<UpdateAction> {
     UpdateAction::from_install_context(InstallContext::current())
 }