[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/src/context/contextual_user_message.rs

@@ -10,6 +10,7 @@ use super::InternalModelContextFragment;
 use super::LegacyApplyPatchExecCommandWarning;
 use super::LegacyModelMismatchWarning;
 use super::LegacyUnifiedExecProcessLimitWarning;
+use super::RecommendedPluginsInstructions;
 use super::SkillInstructions;
 use super::SubagentNotification;
 use super::TurnAborted;
@@ -33,6 +34,8 @@ static SUBAGENT_NOTIFICATION_REGISTRATION: FragmentRegistrationProxy<SubagentNot
 static INTERNAL_MODEL_CONTEXT_REGISTRATION: FragmentRegistrationProxy<
     InternalModelContextFragment,
 > = FragmentRegistrationProxy::new();
+static RECOMMENDED_PLUGINS_REGISTRATION: FragmentRegistrationProxy<RecommendedPluginsInstructions> =
+    FragmentRegistrationProxy::new();
 static LEGACY_UNIFIED_EXEC_PROCESS_LIMIT_WARNING_REGISTRATION: FragmentRegistrationProxy<
     LegacyUnifiedExecProcessLimitWarning,
 > = FragmentRegistrationProxy::new();
@@ -52,6 +55,7 @@ static CONTEXTUAL_USER_FRAGMENTS: &[&dyn FragmentRegistration] = &[
     &TURN_ABORTED_REGISTRATION,
     &SUBAGENT_NOTIFICATION_REGISTRATION,
     &INTERNAL_MODEL_CONTEXT_REGISTRATION,
+    &RECOMMENDED_PLUGINS_REGISTRATION,
     &LEGACY_UNIFIED_EXEC_PROCESS_LIMIT_WARNING_REGISTRATION,
     &LEGACY_APPLY_PATCH_EXEC_COMMAND_WARNING_REGISTRATION,
     &LEGACY_MODEL_MISMATCH_WARNING_REGISTRATION,

codex-rs/core/src/context/contextual_user_message_tests.rs

@@ -75,6 +75,14 @@ fn detects_internal_model_context_fragment() {
     }));
 }
 
+#[test]
+fn detects_recommended_plugins_fragment() {
+    assert!(is_contextual_user_fragment(&ContentItem::InputText {
+        text: "<recommended_plugins>\n- Google Drive (google-drive@openai-curated-remote)\n</recommended_plugins>"
+            .to_string(),
+    }));
+}
+
 #[test]
 fn detects_legacy_goal_context_fragment() {
     assert!(is_contextual_user_fragment(&ContentItem::InputText {

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

@@ -23,6 +23,7 @@ mod plugin_instructions;
 mod realtime_end_instructions;
 mod realtime_start_instructions;
 mod realtime_start_with_instructions;
+mod recommended_plugins_instructions;
 mod subagent_notification;
 mod token_budget_context;
 mod turn_aborted;
@@ -62,6 +63,7 @@ pub(crate) use plugin_instructions::PluginInstructions;
 pub(crate) use realtime_end_instructions::RealtimeEndInstructions;
 pub(crate) use realtime_start_instructions::RealtimeStartInstructions;
 pub(crate) use realtime_start_with_instructions::RealtimeStartWithInstructions;
+pub(crate) use recommended_plugins_instructions::RecommendedPluginsInstructions;
 pub(crate) use subagent_notification::SubagentNotification;
 pub(crate) use token_budget_context::TokenBudgetContext;
 pub(crate) use token_budget_context::TokenBudgetRemainingContext;

codex-rs/core/src/context/recommended_plugins_instructions.rs

@@ -0,0 +1,49 @@
+use super::ContextualUserFragment;
+use codex_tools::DiscoverableTool;
+
+const RECOMMENDED_PLUGINS_INTRO: &str = "Here is a list of plugins that are available but not installed. If the user's query would benefit from one of these plugins, use the `request_plugin_install` tool to suggest that they install it. All entries have `tool_type: plugin`; pass `plugin` as `tool_type` and the parenthesized ID as `tool_id`. For example, suggest the Google Drive plugin if the query could possibly be better answered with access to Google Drive.";
+const MAX_RECOMMENDED_PLUGINS: usize = 50;
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct RecommendedPluginsInstructions {
+    plugins: Vec<DiscoverableTool>,
+}
+
+impl RecommendedPluginsInstructions {
+    pub(crate) fn from_plugins(plugins: &[DiscoverableTool]) -> Option<Self> {
+        if plugins.is_empty() {
+            return None;
+        }
+        Some(Self {
+            plugins: plugins
+                .iter()
+                .take(MAX_RECOMMENDED_PLUGINS)
+                .cloned()
+                .collect(),
+        })
+    }
+}
+
+impl ContextualUserFragment for RecommendedPluginsInstructions {
+    fn role(&self) -> &'static str {
+        "user"
+    }
+
+    fn markers(&self) -> (&'static str, &'static str) {
+        Self::type_markers()
+    }
+
+    fn type_markers() -> (&'static str, &'static str) {
+        ("<recommended_plugins>", "</recommended_plugins>")
+    }
+
+    fn body(&self) -> String {
+        let plugins = self
+            .plugins
+            .iter()
+            .map(|plugin| format!("- {} ({})", plugin.name(), plugin.id()))
+            .collect::<Vec<_>>()
+            .join("\n");
+        format!("\n{RECOMMENDED_PLUGINS_INTRO}\n\n{plugins}\n")
+    }
+}