fix: drop session span at end of the session (#9126)

codex-rs/core/src/tasks/regular.rs

@@ -29,8 +29,10 @@ impl SessionTask for RegularTask {
         cancellation_token: CancellationToken,
     ) -> Option<String> {
         let sess = session.clone_session();
-        let run_turn_span =
-            trace_span!(parent: sess.services.otel_manager.current_span(), "run_turn");
+        let run_turn_span = trace_span!("run_turn");
+        sess.services
+            .otel_manager
+            .apply_traceparent_parent(&run_turn_span);
         run_turn(sess, ctx, input, cancellation_token)
             .instrument(run_turn_span)
             .await

codex-rs/otel/src/lib.rs

@@ -17,7 +17,6 @@ use codex_protocol::ThreadId;
 use serde::Serialize;
 use std::time::Duration;
 use strum_macros::Display;
-use tracing::Span;
 
 #[derive(Debug, Clone, Serialize, Display)]
 #[serde(rename_all = "snake_case")]
@@ -42,7 +41,6 @@ pub struct OtelEventMetadata {
 #[derive(Debug, Clone)]
 pub struct OtelManager {
     pub(crate) metadata: OtelEventMetadata,
-    pub(crate) session_span: Span,
     pub(crate) metrics: Option<MetricsClient>,
     pub(crate) metrics_use_metadata_tags: bool,
 }

codex-rs/otel/src/traces/otel_manager.rs

@@ -23,7 +23,6 @@ use std::time::Duration;
 use std::time::Instant;
 use tokio::time::error::Elapsed;
 use tracing::Span;
-use tracing::trace_span;
 use tracing_opentelemetry::OpenTelemetrySpanExt;
 
 pub use crate::OtelEventMetadata;
@@ -41,14 +40,8 @@ impl OtelManager {
         auth_mode: Option<AuthMode>,
         log_user_prompts: bool,
         terminal_type: String,
-        session_source: SessionSource,
+        _session_source: SessionSource,
     ) -> OtelManager {
-        let session_span = trace_span!("new_session", conversation_id = %conversation_id, session_source = %session_source);
-
-        if let Some(context) = traceparent_context_from_env() {
-            let _ = session_span.set_parent(context);
-        }
-
         Self {
             metadata: OtelEventMetadata {
                 conversation_id,
@@ -61,14 +54,15 @@ impl OtelManager {
                 app_version: env!("CARGO_PKG_VERSION"),
                 terminal_type,
             },
-            session_span,
             metrics: crate::metrics::global(),
             metrics_use_metadata_tags: true,
         }
     }
 
-    pub fn current_span(&self) -> &Span {
-        &self.session_span
+    pub fn apply_traceparent_parent(&self, span: &Span) {
+        if let Some(context) = traceparent_context_from_env() {
+            let _ = span.set_parent(context);
+        }
     }
 
     pub fn record_responses(&self, handle_responses_span: &Span, event: &ResponseEvent) {