store and expose parent_thread_id on Threads

codex-rs/analytics/src/analytics_client_tests.rs

@@ -165,6 +165,7 @@ fn sample_thread_with_metadata(
         id: thread_id.to_string(),
         session_id: format!("session-{thread_id}"),
         forked_from_id: None,
+        parent_thread_id: None,
         preview: "first prompt".to_string(),
         ephemeral,
         model_provider: "openai".to_string(),
@@ -2456,7 +2457,7 @@ fn subagent_thread_started_thread_spawn_serializes_parent_thread_id() {
         SubAgentThreadStartedInput {
             session_id: "session-root".to_string(),
             thread_id: "thread-spawn".to_string(),
-            parent_thread_id: None,
+            parent_thread_id: Some(parent_thread_id.to_string()),
             product_client_id: "codex-tui".to_string(),
             client_name: "codex-tui".to_string(),
             client_version: "1.0.0".to_string(),
@@ -2534,11 +2535,14 @@ fn subagent_thread_started_other_serializes_expected_shape() {
 
 #[test]
 fn subagent_thread_started_other_serializes_explicit_parent_thread_id() {
+    let parent_thread_id =
+        codex_protocol::ThreadId::from_string("33333333-3333-4333-8333-333333333333")
+            .expect("valid thread id");
     let event = TrackEventRequest::ThreadInitialized(subagent_thread_started_event_request(
         SubAgentThreadStartedInput {
             session_id: "session-root".to_string(),
             thread_id: "thread-guardian".to_string(),
-            parent_thread_id: Some("parent-thread-guardian".to_string()),
+            parent_thread_id: Some(parent_thread_id.to_string()),
             product_client_id: "codex-tui".to_string(),
             client_name: "codex-tui".to_string(),
             client_version: "1.0.0".to_string(),
@@ -2553,7 +2557,7 @@ fn subagent_thread_started_other_serializes_explicit_parent_thread_id() {
     assert_eq!(payload["event_params"]["subagent_source"], "guardian");
     assert_eq!(
         payload["event_params"]["parent_thread_id"],
-        "parent-thread-guardian"
+        "33333333-3333-4333-8333-333333333333"
     );
 }
 
@@ -2642,7 +2646,7 @@ async fn subagent_thread_started_inherits_parent_connection_for_new_thread() {
                 SubAgentThreadStartedInput {
                     session_id: "session-root".to_string(),
                     thread_id: "thread-review".to_string(),
-                    parent_thread_id: None,
+                    parent_thread_id: Some(parent_thread_id.to_string()),
                     product_client_id: "parent-client".to_string(),
                     client_name: "parent-client".to_string(),
                     client_version: "1.0.0".to_string(),

codex-rs/analytics/src/client_tests.rs

@@ -124,6 +124,7 @@ fn sample_thread(thread_id: &str) -> Thread {
         id: thread_id.to_string(),
         session_id: format!("session-{thread_id}"),
         forked_from_id: None,
+        parent_thread_id: None,
         preview: "first prompt".to_string(),
         ephemeral: false,
         model_provider: "openai".to_string(),

codex-rs/analytics/src/events.rs

@@ -1047,9 +1047,7 @@ pub(crate) fn subagent_thread_started_event_request(
         thread_source: Some(ThreadSource::Subagent),
         initialization_mode: ThreadInitializationMode::New,
         subagent_source: Some(subagent_source_name(&input.subagent_source)),
-        parent_thread_id: input
-            .parent_thread_id
-            .or_else(|| subagent_parent_thread_id(&input.subagent_source)),
+        parent_thread_id: input.parent_thread_id,
         created_at: input.created_at,
     };
     ThreadInitializedEvent {
@@ -1059,19 +1057,7 @@ pub(crate) fn subagent_thread_started_event_request(
 }
 
 pub(crate) fn subagent_source_name(subagent_source: &SubAgentSource) -> String {
-    match subagent_source {
-        SubAgentSource::Review => "review".to_string(),
-        SubAgentSource::Compact => "compact".to_string(),
-        SubAgentSource::ThreadSpawn { .. } => "thread_spawn".to_string(),
-        SubAgentSource::MemoryConsolidation => "memory_consolidation".to_string(),
-        SubAgentSource::Other(other) => other.clone(),
-    }
-}
-
-pub(crate) fn subagent_parent_thread_id(subagent_source: &SubAgentSource) -> Option<String> {
-    subagent_source
-        .parent_thread_id()
-        .map(|parent_thread_id| parent_thread_id.to_string())
+    subagent_source.kind().to_string()
 }
 
 fn analytics_hook_status(status: HookRunStatus) -> HookRunStatus {

codex-rs/analytics/src/reducer.rs

@@ -55,7 +55,6 @@ use crate::events::codex_hook_run_metadata;
 use crate::events::codex_plugin_metadata;
 use crate::events::codex_plugin_used_metadata;
 use crate::events::plugin_state_event_type;
-use crate::events::subagent_parent_thread_id;
 use crate::events::subagent_source_name;
 use crate::events::subagent_thread_started_event_request;
 use crate::facts::AnalyticsFact;
@@ -267,20 +266,18 @@ impl ThreadMetadataState {
         session_id: String,
         session_source: &SessionSource,
         thread_source: Option<ThreadSource>,
+        parent_thread_id: Option<String>,
         initialization_mode: ThreadInitializationMode,
     ) -> Self {
-        let (subagent_source, parent_thread_id) = match session_source {
-            SessionSource::SubAgent(subagent_source) => (
-                Some(subagent_source_name(subagent_source)),
-                subagent_parent_thread_id(subagent_source),
-            ),
+        let subagent_source = match session_source {
+            SessionSource::SubAgent(subagent_source) => Some(subagent_source_name(subagent_source)),
             SessionSource::Cli
             | SessionSource::VSCode
             | SessionSource::Exec
             | SessionSource::Mcp
             | SessionSource::Custom(_)
             | SessionSource::Internal(_)
-            | SessionSource::Unknown => (None, None),
+            | SessionSource::Unknown => None,
         };
         Self {
             session_id,
@@ -516,10 +513,7 @@ impl AnalyticsReducer {
         input: SubAgentThreadStartedInput,
         out: &mut Vec<TrackEventRequest>,
     ) {
-        let parent_thread_id = input
-            .parent_thread_id
-            .clone()
-            .or_else(|| subagent_parent_thread_id(&input.subagent_source));
+        let parent_thread_id = input.parent_thread_id.clone();
         let parent_connection_id = parent_thread_id
             .as_ref()
             .and_then(|parent_thread_id| self.threads.get(parent_thread_id))
@@ -1238,13 +1232,15 @@ impl AnalyticsReducer {
         let session_source: SessionSource = thread.source.into();
         let session_id = thread.session_id;
         let thread_id = thread.id;
+        let parent_thread_id = thread.parent_thread_id;
         let Some(connection_state) = self.connections.get(&connection_id) else {
             return;
         };
         let thread_metadata = ThreadMetadataState::from_thread_metadata(
             session_id.clone(),
             &session_source,
             thread.thread_source.map(Into::into),
+            parent_thread_id,
             initialization_mode,
         );
         self.threads.insert(

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -2328,6 +2328,7 @@ mod tests {
                     id: "67e55044-10b1-426f-9247-bb680e5fe0c8".to_string(),
                     session_id: "67e55044-10b1-426f-9247-bb680e5fe0c7".to_string(),
                     forked_from_id: None,
+                    parent_thread_id: None,
                     preview: "first prompt".to_string(),
                     ephemeral: true,
                     model_provider: "openai".to_string(),
@@ -2370,6 +2371,7 @@ mod tests {
                         "id": "67e55044-10b1-426f-9247-bb680e5fe0c8",
                         "sessionId": "67e55044-10b1-426f-9247-bb680e5fe0c7",
                         "forkedFromId": null,
+                        "parentThreadId": null,
                         "preview": "first prompt",
                         "ephemeral": true,
                         "modelProvider": "openai",

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -142,6 +142,7 @@ fn thread_resume_response_round_trips_initial_turns_page() {
             id: "thr_123".to_string(),
             session_id: "thr_123".to_string(),
             forked_from_id: None,
+            parent_thread_id: None,
             preview: String::new(),
             ephemeral: false,
             model_provider: "openai".to_string(),
@@ -3581,6 +3582,7 @@ fn thread_lifecycle_responses_default_missing_optional_fields() {
     let fork: ThreadForkResponse = serde_json::from_value(response).expect("thread/fork response");
 
     assert_eq!(start.instruction_sources, Vec::<AbsolutePathBuf>::new());
+    assert_eq!(start.thread.parent_thread_id, None);
     assert_eq!(resume.instruction_sources, Vec::<AbsolutePathBuf>::new());
     assert_eq!(fork.instruction_sources, Vec::<AbsolutePathBuf>::new());
     assert_eq!(start.active_permission_profile, None);

codex-rs/app-server-protocol/src/protocol/v2/thread_data.rs

@@ -108,6 +108,8 @@ pub struct Thread {
     pub session_id: String,
     /// Source thread id when this thread was created by forking another thread.
     pub forked_from_id: Option<String>,
+    /// The ID of the parent thread. This will only be set if this thread is a subagent.
+    pub parent_thread_id: Option<String>,
     /// Usually the first user message in the thread, if available.
     pub preview: String,
     /// Whether the thread is ephemeral and should not be materialized on disk.

codex-rs/app-server/src/bespoke_event_handling.rs

@@ -2170,6 +2170,7 @@ mod tests {
             thread_id,
             rollout_path: None,
             forked_from_id: None,
+            parent_thread_id: None,
             preview: "fallback preview".to_string(),
             name: Some("Rollback thread".to_string()),
             model_provider: "openai".to_string(),

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -4012,6 +4012,7 @@ pub(crate) fn thread_from_stored_thread(
         id: thread_id.clone(),
         session_id: thread_id,
         forked_from_id: thread.forked_from_id.map(|id| id.to_string()),
+        parent_thread_id: thread.parent_thread_id.map(|id| id.to_string()),
         preview: thread.preview,
         ephemeral: false,
         model_provider: if thread.model_provider.is_empty() {
@@ -4220,6 +4221,7 @@ fn build_thread_from_snapshot(
         id: thread_id.to_string(),
         session_id,
         forked_from_id: None,
+        parent_thread_id: config_snapshot.parent_thread_id.map(|id| id.to_string()),
         preview: String::new(),
         ephemeral: config_snapshot.ephemeral,
         model_provider: config_snapshot.model_provider_id.clone(),