[codex] [3/4] Activate endpoint plugin recommendations (#27704)

Summary\n- Await endpoint recommendation selection while constructing
each authenticated turn, removing the first-turn cache race.\n- Snapshot
and filter endpoint candidates once per turn, then use that same set for
the bounded contextual user fragment, tool exposure, and exact install
validation.\n- Keep recommendation selection ephemeral: do not persist
recommendation state in or gate resumed threads on prior context.\n-
Hide the legacy list tool in endpoint mode and preserve legacy discovery
unchanged when the endpoint is disabled or unavailable.\n- Keep remote
plugin and connector app identities out of model-visible context and
attach them only to Codex-owned elicitation metadata.\n\nStack\n- 3/4,
based on #28400.\n- Endpoint client and cache: #28399.\n- Generalized
suggestion presentation: #28400.\n- Install-schema follow-up:
#28403.\n\nValidation\n- \n- \n- \n- \n- Full : 2,649 passed and 88
environment-dependent tests failed because this sandbox cannot write ,
nest Seatbelt, or locate auxiliary test binaries.

codex-rs/core-plugins/src/manager.rs

@@ -57,6 +57,8 @@ use codex_config::ConfigLayerStack;
 use codex_config::clear_user_plugin;
 use codex_config::set_user_plugin_enabled;
 use codex_config::types::PluginConfig;
+use codex_config::types::ToolSuggestDisabledTool;
+use codex_config::types::ToolSuggestDiscoverableType;
 use codex_core_skills::SkillMetadata;
 use codex_core_skills::config_rules::SkillConfigRules;
 use codex_core_skills::config_rules::skill_config_rules_from_stack;
@@ -71,6 +73,9 @@ use codex_plugin::app_connector_ids_from_declarations;
 use codex_plugin::prompt_safe_plugin_description;
 use codex_protocol::protocol::HookEventName;
 use codex_protocol::protocol::Product;
+use codex_tools::DiscoverablePluginInfo;
+use codex_tools::DiscoverableTool;
+use codex_tools::filter_request_plugin_install_discoverable_tools_for_client;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_plugins::PluginSkillRoot;
 use std::collections::HashMap;
@@ -114,6 +119,15 @@ impl PluginsConfigInput {
     }
 }
 
+/// Inputs used to select endpoint-backed plugin install candidates.
+pub struct RecommendedPluginCandidatesInput<'a> {
+    pub plugins_config: &'a PluginsConfigInput,
+    pub loaded_plugins: &'a PluginLoadOutcome,
+    pub auth: Option<&'a CodexAuth>,
+    pub disabled_tools: &'a [ToolSuggestDisabledTool],
+    pub app_server_client_name: Option<&'a str>,
+}
+
 #[derive(Clone, PartialEq, Eq)]
 struct FeaturedPluginIdsCacheKey {
     chatgpt_base_url: String,
@@ -997,6 +1011,59 @@ impl PluginsManager {
         mode
     }
 
+    /// Returns endpoint recommendations eligible for installation in the current client.
+    /// `None` selects the legacy discovery workflow.
+    pub async fn recommended_plugin_candidates_for_config(
+        &self,
+        input: RecommendedPluginCandidatesInput<'_>,
+    ) -> Option<Vec<DiscoverableTool>> {
+        let RecommendedPluginsMode::Endpoint { plugins } = self
+            .recommended_plugins_mode_for_config(input.plugins_config, input.auth)
+            .await
+        else {
+            return None;
+        };
+        if plugins.is_empty() {
+            return Some(Vec::new());
+        }
+
+        let installed_plugin_ids = input
+            .loaded_plugins
+            .plugins()
+            .iter()
+            .map(|plugin| plugin.config_name.as_str())
+            .collect::<HashSet<_>>();
+        let disabled_plugin_ids = input
+            .disabled_tools
+            .iter()
+            .filter(|tool| tool.kind == ToolSuggestDiscoverableType::Plugin)
+            .map(|tool| tool.id.as_str())
+            .collect::<HashSet<_>>();
+
+        let candidates = plugins
+            .into_iter()
+            .filter(|plugin| {
+                !installed_plugin_ids.contains(plugin.config_id.as_str())
+                    && !disabled_plugin_ids.contains(plugin.config_id.as_str())
+            })
+            .map(|plugin| {
+                DiscoverableTool::from(DiscoverablePluginInfo {
+                    id: plugin.config_id,
+                    remote_plugin_id: Some(plugin.remote_plugin_id),
+                    name: plugin.display_name,
+                    description: None,
+                    has_skills: false,
+                    mcp_server_names: Vec::new(),
+                    app_connector_ids: plugin.app_connector_ids,
+                })
+            })
+            .collect();
+        Some(filter_request_plugin_install_discoverable_tools_for_client(
+            candidates,
+            input.app_server_client_name,
+        ))
+    }
+
     fn cached_recommended_plugins_mode(
         &self,
         cache_key: &RecommendedPluginsCacheKey,