[codex-analytics] thread events (#15690)

- add event for thread initialization
- thread/start, thread/fork, thread/resume
- feature flagged behind `FeatureFlag::GeneralAnalytics`
- does not yet support threads started by subagents

PR stack:
- --> [[telemetry] thread events
#15690](https://github.com/openai/codex/pull/15690)
- [[telemetry] subagent events
#15915](https://github.com/openai/codex/pull/15915)
- [[telemetry] turn events
#15591](https://github.com/openai/codex/pull/15591)
- [[telemetry] steer events
#15697](https://github.com/openai/codex/pull/15697)
- [[telemetry] queued prompt data
#15804](https://github.com/openai/codex/pull/15804)


Sample extracted logs in Codex-backend
```
INFO     | 2026-03-29 16:39:37 | codex_backend.routers.analytics_events | analytics_events.track_analytics_events:398 | Tracked analytics event codex_thread_initialized thread_id=019d3bf7-9f5f-7f82-9877-6d48d1052531 product_surface=codex product_client_id=CODEX_CLI client_name=codex-tui client_version=0.0.0 rpc_transport=in_process experimental_api_enabled=True codex_rs_version=0.0.0 runtime_os=macos runtime_os_version=26.4.0 runtime_arch=aarch64 model=gpt-5.3-codex ephemeral=False thread_source=user initialization_mode=new subagent_source=None parent_thread_id=None created_at=1774827577 | 
INFO     | 2026-03-29 16:45:46 | codex_backend.routers.analytics_events | analytics_events.track_analytics_events:398 | Tracked analytics event codex_thread_initialized thread_id=019d3b84-5731-79d0-9b3b-9c6efe5f5066 product_surface=codex product_client_id=CODEX_CLI client_name=codex-tui client_version=0.0.0 rpc_transport=in_process experimental_api_enabled=True codex_rs_version=0.0.0 runtime_os=macos runtime_os_version=26.4.0 runtime_arch=aarch64 model=gpt-5.3-codex ephemeral=False thread_source=user initialization_mode=resumed subagent_source=None parent_thread_id=None created_at=1774820022 | 
INFO     | 2026-03-29 16:45:49 | codex_backend.routers.analytics_events | analytics_events.track_analytics_events:398 | Tracked analytics event codex_thread_initialized thread_id=019d3bfd-4cd6-7c12-a13e-48cef02e8c4d product_surface=codex product_client_id=CODEX_CLI client_name=codex-tui client_version=0.0.0 rpc_transport=in_process experimental_api_enabled=True codex_rs_version=0.0.0 runtime_os=macos runtime_os_version=26.4.0 runtime_arch=aarch64 model=gpt-5.3-codex ephemeral=False thread_source=user initialization_mode=forked subagent_source=None parent_thread_id=None created_at=1774827949 | 
INFO     | 2026-03-29 17:20:29 | codex_backend.routers.analytics_events | analytics_events.track_analytics_events:398 | Tracked analytics event codex_thread_initialized thread_id=019d3c1d-0412-7ed2-ad24-c9c0881a36b0 product_surface=codex product_client_id=CODEX_SERVICE_EXEC client_name=codex_exec client_version=0.0.0 rpc_transport=in_process experimental_api_enabled=True codex_rs_version=0.0.0 runtime_os=macos runtime_os_version=26.4.0 runtime_arch=aarch64 model=gpt-5.3-codex ephemeral=False thread_source=user initialization_mode=new subagent_source=None parent_thread_id=None created_at=1774830027 | 
```

Notes
- `product_client_id` gets canonicalized in codex-backend
- subagent threads are addressed in a following pr

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

@@ -32,6 +32,7 @@ use codex_app_server_protocol::CancelLoginAccountParams;
 use codex_app_server_protocol::CancelLoginAccountResponse;
 use codex_app_server_protocol::CancelLoginAccountStatus;
 use codex_app_server_protocol::ClientRequest;
+use codex_app_server_protocol::ClientResponse;
 use codex_app_server_protocol::CodexErrorInfo as AppServerCodexErrorInfo;
 use codex_app_server_protocol::CollaborationModeListParams;
 use codex_app_server_protocol::CollaborationModeListResponse;
@@ -179,6 +180,7 @@ use codex_arg0::Arg0DispatchPaths;
 use codex_backend_client::Client as BackendClient;
 use codex_chatgpt::connectors;
 use codex_cloud_requirements::cloud_requirements_loader;
+use codex_core::AnalyticsEventsClient;
 use codex_core::AuthManager;
 use codex_core::CodexAuth;
 use codex_core::CodexThread;
@@ -403,6 +405,7 @@ pub(crate) struct CodexMessageProcessor {
     auth_manager: Arc<AuthManager>,
     thread_manager: Arc<ThreadManager>,
     outgoing: Arc<OutgoingMessageSender>,
+    analytics_events_client: AnalyticsEventsClient,
     arg0_paths: Arg0DispatchPaths,
     config: Arc<Config>,
     cli_overrides: Arc<RwLock<Vec<(String, TomlValue)>>>,
@@ -433,6 +436,8 @@ struct ListenerTaskContext {
     thread_manager: Arc<ThreadManager>,
     thread_state_manager: ThreadStateManager,
     outgoing: Arc<OutgoingMessageSender>,
+    analytics_events_client: AnalyticsEventsClient,
+    general_analytics_enabled: bool,
     thread_watch_manager: ThreadWatchManager,
     fallback_model_provider: String,
     codex_home: PathBuf,
@@ -455,6 +460,7 @@ pub(crate) struct CodexMessageProcessorArgs {
     pub(crate) auth_manager: Arc<AuthManager>,
     pub(crate) thread_manager: Arc<ThreadManager>,
     pub(crate) outgoing: Arc<OutgoingMessageSender>,
+    pub(crate) analytics_events_client: AnalyticsEventsClient,
     pub(crate) arg0_paths: Arg0DispatchPaths,
     pub(crate) config: Arc<Config>,
     pub(crate) cli_overrides: Arc<RwLock<Vec<(String, TomlValue)>>>,
@@ -519,6 +525,7 @@ impl CodexMessageProcessor {
             auth_manager,
             thread_manager,
             outgoing,
+            analytics_events_client,
             arg0_paths,
             config,
             cli_overrides,
@@ -531,6 +538,7 @@ impl CodexMessageProcessor {
             auth_manager,
             thread_manager,
             outgoing: outgoing.clone(),
+            analytics_events_client,
             arg0_paths,
             config,
             cli_overrides,
@@ -2086,6 +2094,8 @@ impl CodexMessageProcessor {
             thread_manager: Arc::clone(&self.thread_manager),
             thread_state_manager: self.thread_state_manager.clone(),
             outgoing: Arc::clone(&self.outgoing),
+            analytics_events_client: self.analytics_events_client.clone(),
+            general_analytics_enabled: self.config.features.enabled(Feature::GeneralAnalytics),
             thread_watch_manager: self.thread_watch_manager.clone(),
             fallback_model_provider: self.config.model_provider_id.clone(),
             codex_home: self.config.codex_home.clone(),
@@ -2318,6 +2328,17 @@ impl CodexMessageProcessor {
                     sandbox: config_snapshot.sandbox_policy.into(),
                     reasoning_effort: config_snapshot.reasoning_effort,
                 };
+                if listener_task_context.general_analytics_enabled {
+                    listener_task_context
+                        .analytics_events_client
+                        .track_response(
+                            request_id.connection_id.0,
+                            ClientResponse::ThreadStart {
+                                request_id: request_id.request_id.clone(),
+                                response: response.clone(),
+                            },
+                        );
+                }
 
                 listener_task_context
                     .outgoing
@@ -3796,6 +3817,15 @@ impl CodexMessageProcessor {
                     sandbox: session_configured.sandbox_policy.into(),
                     reasoning_effort: session_configured.reasoning_effort,
                 };
+                if self.config.features.enabled(Feature::GeneralAnalytics) {
+                    self.analytics_events_client.track_response(
+                        request_id.connection_id.0,
+                        ClientResponse::ThreadResume {
+                            request_id: request_id.request_id.clone(),
+                            response: response.clone(),
+                        },
+                    );
+                }
 
                 self.outgoing.send_response(request_id, response).await;
             }
@@ -4403,6 +4433,15 @@ impl CodexMessageProcessor {
             sandbox: session_configured.sandbox_policy.into(),
             reasoning_effort: session_configured.reasoning_effort,
         };
+        if self.config.features.enabled(Feature::GeneralAnalytics) {
+            self.analytics_events_client.track_response(
+                request_id.connection_id.0,
+                ClientResponse::ThreadFork {
+                    request_id: request_id.request_id.clone(),
+                    response: response.clone(),
+                },
+            );
+        }
 
         self.outgoing.send_response(request_id, response).await;
 
@@ -6984,6 +7023,8 @@ impl CodexMessageProcessor {
                 thread_manager: Arc::clone(&self.thread_manager),
                 thread_state_manager: self.thread_state_manager.clone(),
                 outgoing: Arc::clone(&self.outgoing),
+                analytics_events_client: self.analytics_events_client.clone(),
+                general_analytics_enabled: self.config.features.enabled(Feature::GeneralAnalytics),
                 thread_watch_manager: self.thread_watch_manager.clone(),
                 fallback_model_provider: self.config.model_provider_id.clone(),
                 codex_home: self.config.codex_home.clone(),
@@ -7071,6 +7112,8 @@ impl CodexMessageProcessor {
                 thread_manager: Arc::clone(&self.thread_manager),
                 thread_state_manager: self.thread_state_manager.clone(),
                 outgoing: Arc::clone(&self.outgoing),
+                analytics_events_client: self.analytics_events_client.clone(),
+                general_analytics_enabled: self.config.features.enabled(Feature::GeneralAnalytics),
                 thread_watch_manager: self.thread_watch_manager.clone(),
                 fallback_model_provider: self.config.model_provider_id.clone(),
                 codex_home: self.config.codex_home.clone(),
@@ -7102,6 +7145,8 @@ impl CodexMessageProcessor {
             outgoing,
             thread_manager,
             thread_state_manager,
+            analytics_events_client: _,
+            general_analytics_enabled: _,
             thread_watch_manager,
             fallback_model_provider,
             codex_home,