feat: add skill injected counter metric (#9575)

codex-rs/core/src/codex.rs

@@ -2812,10 +2812,11 @@ pub(crate) async fn run_turn(
             .await,
     );
 
+    let otel_manager = turn_context.client.get_otel_manager();
     let SkillInjections {
         items: skill_items,
         warnings: skill_warnings,
-    } = build_skill_injections(&input, skills_outcome.as_ref()).await;
+    } = build_skill_injections(&input, skills_outcome.as_ref(), Some(&otel_manager)).await;
 
     for message in skill_warnings {
         sess.send_event(&turn_context, EventMsg::Warning(WarningEvent { message }))

codex-rs/core/src/skills/injection.rs

@@ -4,6 +4,7 @@ use std::path::PathBuf;
 use crate::instructions::SkillInstructions;
 use crate::skills::SkillLoadOutcome;
 use crate::skills::SkillMetadata;
+use codex_otel::OtelManager;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::user_input::UserInput;
 use tokio::fs;
@@ -17,6 +18,7 @@ pub(crate) struct SkillInjections {
 pub(crate) async fn build_skill_injections(
     inputs: &[UserInput],
     skills: Option<&SkillLoadOutcome>,
+    otel: Option<&OtelManager>,
 ) -> SkillInjections {
     if inputs.is_empty() {
         return SkillInjections::default();
@@ -40,6 +42,7 @@ pub(crate) async fn build_skill_injections(
     for skill in mentioned_skills {
         match fs::read_to_string(&skill.path).await {
             Ok(contents) => {
+                emit_skill_injected_metric(otel, &skill, "ok");
                 result.items.push(ResponseItem::from(SkillInstructions {
                     name: skill.name,
                     path: skill.path.to_string_lossy().into_owned(),
@@ -47,6 +50,7 @@ pub(crate) async fn build_skill_injections(
                 }));
             }
             Err(err) => {
+                emit_skill_injected_metric(otel, &skill, "error");
                 let message = format!(
                     "Failed to load skill {name} at {path}: {err:#}",
                     name = skill.name,
@@ -60,6 +64,18 @@ pub(crate) async fn build_skill_injections(
     result
 }
 
+fn emit_skill_injected_metric(otel: Option<&OtelManager>, skill: &SkillMetadata, status: &str) {
+    let Some(otel) = otel else {
+        return;
+    };
+
+    otel.counter(
+        "codex.skill.injected",
+        1,
+        &[("status", status), ("skill", skill.name.as_str())],
+    );
+}
+
 fn collect_explicit_skill_mentions(
     inputs: &[UserInput],
     skills: &[SkillMetadata],