use std::sync::Arc;use codex_core::config::Config;use codex_extension_api::AgentSpawnFuture;use codex_extension_api::AgentSpawner;use codex_extension_api::ExtensionFuture;use codex_extension_api::ExtensionRegistryBuilder;use codex_extension_api::ThreadLifecycleContributor;use codex_extension_api::ThreadStartInput;use codex_protocol::ThreadId;/// Guardian extension dependencies supplied by the host at construction time.#[derive(Clone, Debug)]pub struct GuardianExtension<S> {    agent_spawner: S,}impl<S> GuardianExtension<S> {    /// Creates a guardian extension with its host-provided agent spawn helper.    pub fn new(agent_spawner: S) -> Self {        Self { agent_spawner }    }    /// Delegates one guardian-owned subagent spawn request to the host helper.    pub fn spawn_subagent<'a, R>(        &'a self,        forked_from_thread_id: ThreadId,        request: R,    ) -> AgentSpawnFuture<'a, <S as AgentSpawner<R>>::Spawned, <S as AgentSpawner<R>>::Error>    where        S: AgentSpawner<R>,    {        self.agent_spawner            .spawn_subagent(forked_from_thread_id, request)    }}/// Thread-local guardian state captured when the host starts a thread.#[derive(Clone, Copy, Debug)]pub struct GuardianThreadContext {    forked_from_thread_id: ThreadId,}impl GuardianThreadContext {    /// Returns the thread that future guardian subagents should fork from by default.    pub fn forked_from_thread_id(&self) -> ThreadId {        self.forked_from_thread_id    }}impl<S> ThreadLifecycleContributor<Config> for GuardianExtension<S>where    S: Send + Sync,{    fn on_thread_start<'a>(        &'a self,        input: ThreadStartInput<'a, Config>,    ) -> ExtensionFuture<'a, ()> {        Box::pin(async move {            let Ok(forked_from_thread_id) = ThreadId::from_string(input.thread_store.level_id())            else {                return;            };            input.thread_store.insert(GuardianThreadContext {                forked_from_thread_id,            });        })    }}/// Installs the guardian contributors into the extension registry.pub fn install<S>(registry: &mut ExtensionRegistryBuilder<Config>, agent_spawner: S)where    S: Send + Sync + 'static,{    registry.thread_lifecycle_contributor(Arc::new(GuardianExtension::new(agent_spawner)));}