Reduce stack pressure in session startup and config rebuilds

codex-rs/core/src/session/mod.rs

@@ -625,7 +625,7 @@ impl Codex {
         let session_source_clone = session_configuration.session_source.clone();
         let (agent_status_tx, agent_status_rx) = watch::channel(AgentStatus::PendingInit);
 
-        let session = Session::new(
+        let session = Box::pin(Session::new(
             session_configuration,
             config.clone(),
             installation_id,
@@ -647,7 +647,7 @@ impl Codex {
             parent_rollout_thread_trace,
             attestation_provider,
             multi_agent_version,
-        )
+        ))
         .await
         .map_err(|e| {
             error!("Failed to create session: {e:#}");

codex-rs/core/src/thread_manager.rs

@@ -1308,7 +1308,7 @@ impl ThreadManagerState {
             .await;
         let CodexSpawnOk {
             codex, thread_id, ..
-        } = Codex::spawn(CodexSpawnArgs {
+        } = Box::pin(Codex::spawn(CodexSpawnArgs {
             config,
             installation_id: self.installation_id.clone(),
             auth_manager,
@@ -1336,7 +1336,7 @@ impl ThreadManagerState {
             thread_store: Arc::clone(&self.thread_store),
             attestation_provider: self.attestation_provider.clone(),
             inherited_multi_agent_version: multi_agent_version,
-        })
+        }))
         .await?;
         let new_thread = self
             .finalize_thread_spawn(codex, thread_id, tracked_session_source)

codex-rs/tui/src/app/config_persistence.rs

@@ -14,19 +14,32 @@ pub(super) struct WindowsSetupPermissions {
     pub(super) workspace_roots: Vec<AbsolutePathBuf>,
 }
 
+async fn build_config_on_runtime_worker(
+    builder: ConfigBuilder,
+    error_context: String,
+) -> Result<Config> {
+    match tokio::spawn(async move { builder.build().await }).await {
+        Ok(build_result) => build_result.wrap_err(error_context),
+        Err(err) if err.is_panic() => std::panic::resume_unwind(err.into_panic()),
+        Err(err) => Err(err).wrap_err_with(|| format!("{error_context} task failed")),
+    }
+}
+
 impl App {
     pub(super) async fn rebuild_config_for_cwd(&self, cwd: PathBuf) -> Result<Config> {
         let mut overrides = self.harness_overrides.clone();
         overrides.cwd = Some(cwd.clone());
         let cwd_display = cwd.display().to_string();
-        ConfigBuilder::default()
+        let builder = ConfigBuilder::default()
             .codex_home(self.config.codex_home.to_path_buf())
             .cli_overrides(self.cli_kv_overrides.clone())
             .harness_overrides(overrides)
-            .loader_overrides(self.loader_overrides.clone())
-            .build()
-            .await
-            .wrap_err_with(|| format!("Failed to rebuild config for cwd {cwd_display}"))
+            .loader_overrides(self.loader_overrides.clone());
+        build_config_on_runtime_worker(
+            builder,
+            format!("Failed to rebuild config for cwd {cwd_display}"),
+        )
+        .await
     }
 
     pub(super) async fn rebuild_config_for_permission_profile(
@@ -38,16 +51,16 @@ impl App {
         overrides.sandbox_mode = None;
         overrides.permission_profile = None;
         overrides.default_permissions = Some(profile_id.to_string());
-        ConfigBuilder::default()
+        let builder = ConfigBuilder::default()
             .codex_home(self.config.codex_home.to_path_buf())
             .cli_overrides(self.cli_kv_overrides.clone())
             .harness_overrides(overrides)
-            .loader_overrides(self.loader_overrides.clone())
-            .build()
-            .await
-            .wrap_err_with(|| {
-                format!("Failed to rebuild config for permission profile {profile_id}")
-            })
+            .loader_overrides(self.loader_overrides.clone());
+        build_config_on_runtime_worker(
+            builder,
+            format!("Failed to rebuild config for permission profile {profile_id}"),
+        )
+        .await
     }
 
     #[cfg(target_os = "windows")]