[codex-analytics] add compaction analytics event (#17155)

- event for compaction analytics
- introduces thread-connection and thread metadata caches for data
denormalization, expected to be useful for denormalization onto core
emitted events in general
- threads analytics event client into core (mirrors approved
implementation in #16640)
- denormalizes key thread metadata: thread_source, subagent_source,
parent_thread_id, as well as app-server client and runtime metadata)
- compaction strategy defaults to memento, forward compatible with
expected prefill_compaction strategy

1. Manual standalone compact, local
`INFO | 2026-04-09 17:35:50 | codex_backend.routers.analytics_events |
analytics_events.track_analytics_events:526 | Tracked
codex_compaction_event event params={'thread_id':
'019d74d0-5cfb-70c0-bef9-165c3bf9b2df', 'turn_id':
'019d74d0-d7f6-7c81-acc6-aae2030243d6', 'product_surface': 'codex',
'app_server_client': {'product_client_id': 'CODEX_CLI', 'client_name':
'codex-tui', 'client_version': '0.0.0', 'rpc_transport': 'in_process',
'experimental_api_enabled': True}, 'runtime': {'codex_rs_version':
'0.0.0', 'runtime_os': 'macos', 'runtime_os_version': '26.4.0',
'runtime_arch': 'aarch64'}, 'trigger': 'manual', 'reason':
'user_requested', 'implementation': 'responses', 'phase':
'standalone_turn', 'strategy': 'memento', 'status': 'completed',
'active_context_tokens_before': 20170, 'active_context_tokens_after':
4830, 'started_at': 1775781337, 'completed_at': 1775781350,
'thread_source': 'user', 'subagent_source': None, 'parent_thread_id':
None, 'error': None, 'duration_ms': 13524} | `

2. Auto pre-turn compact, local
`INFO | 2026-04-09 17:37:30 | codex_backend.routers.analytics_events |
analytics_events.track_analytics_events:526 | Tracked
codex_compaction_event event params={'thread_id':
'019d74d2-45ef-71d1-9c93-23cc0c13d988', 'turn_id':
'019d74d2-7b42-7372-9f0e-c0da3f352328', 'product_surface': 'codex',
'app_server_client': {'product_client_id': 'CODEX_CLI', 'client_name':
'codex-tui', 'client_version': '0.0.0', 'rpc_transport': 'in_process',
'experimental_api_enabled': True}, 'runtime': {'codex_rs_version':
'0.0.0', 'runtime_os': 'macos', 'runtime_os_version': '26.4.0',
'runtime_arch': 'aarch64'}, 'trigger': 'auto', 'reason':
'context_limit', 'implementation': 'responses', 'phase': 'pre_turn',
'strategy': 'memento', 'status': 'completed',
'active_context_tokens_before': 20063, 'active_context_tokens_after':
4822, 'started_at': 1775781444, 'completed_at': 1775781449,
'thread_source': 'user', 'subagent_source': None, 'parent_thread_id':
None, 'error': None, 'duration_ms': 5497} | `

3. Auto mid-turn compact, local
`INFO | 2026-04-09 17:38:28 | codex_backend.routers.analytics_events |
analytics_events.track_analytics_events:526 | Tracked
codex_compaction_event event params={'thread_id':
'019d74d3-212f-7a20-8c0a-4816a978675e', 'turn_id':
'019d74d3-3ee1-7462-89f6-2ffbeefcd5e3', 'product_surface': 'codex',
'app_server_client': {'product_client_id': 'CODEX_CLI', 'client_name':
'codex-tui', 'client_version': '0.0.0', 'rpc_transport': 'in_process',
'experimental_api_enabled': True}, 'runtime': {'codex_rs_version':
'0.0.0', 'runtime_os': 'macos', 'runtime_os_version': '26.4.0',
'runtime_arch': 'aarch64'}, 'trigger': 'auto', 'reason':
'context_limit', 'implementation': 'responses', 'phase': 'mid_turn',
'strategy': 'memento', 'status': 'completed',
'active_context_tokens_before': 20325, 'active_context_tokens_after':
14641, 'started_at': 1775781500, 'completed_at': 1775781508,
'thread_source': 'user', 'subagent_source': None, 'parent_thread_id':
None, 'error': None, 'duration_ms': 7507} | `

4. Remote /responses/compact, manual standalone
`INFO | 2026-04-09 17:40:20 | codex_backend.routers.analytics_events |
analytics_events.track_analytics_events:526 | Tracked
codex_compaction_event event params={'thread_id':
'019d74d4-7a11-78a1-89f7-0535a1149416', 'turn_id':
'019d74d4-e087-7183-9c20-b1e40b7578c0', 'product_surface': 'codex',
'app_server_client': {'product_client_id': 'CODEX_CLI', 'client_name':
'codex-tui', 'client_version': '0.0.0', 'rpc_transport': 'in_process',
'experimental_api_enabled': True}, 'runtime': {'codex_rs_version':
'0.0.0', 'runtime_os': 'macos', 'runtime_os_version': '26.4.0',
'runtime_arch': 'aarch64'}, 'trigger': 'manual', 'reason':
'user_requested', 'implementation': 'responses_compact', 'phase':
'standalone_turn', 'strategy': 'memento', 'status': 'completed',
'active_context_tokens_before': 23461, 'active_context_tokens_after':
6171, 'started_at': 1775781601, 'completed_at': 1775781620,
'thread_source': 'user', 'subagent_source': None, 'parent_thread_id':
None, 'error': None, 'duration_ms': 18971} | `

codex-rs/core/src/compact_remote.rs

@@ -5,12 +5,18 @@ use crate::Prompt;
 use crate::codex::Session;
 use crate::codex::TurnContext;
 use crate::codex::built_tools;
+use crate::compact::CompactionAnalyticsAttempt;
 use crate::compact::InitialContextInjection;
+use crate::compact::compaction_status_from_result;
 use crate::compact::insert_initial_context_before_last_real_user_or_summary;
 use crate::context_manager::ContextManager;
 use crate::context_manager::TotalTokenUsageBreakdown;
 use crate::context_manager::estimate_response_item_model_visible_bytes;
 use crate::context_manager::is_codex_generated_item;
+use codex_analytics::CompactionImplementation;
+use codex_analytics::CompactionPhase;
+use codex_analytics::CompactionReason;
+use codex_analytics::CompactionTrigger;
 use codex_protocol::error::CodexErr;
 use codex_protocol::error::Result as CodexResult;
 use codex_protocol::items::ContextCompactionItem;
@@ -29,8 +35,18 @@ pub(crate) async fn run_inline_remote_auto_compact_task(
     sess: Arc<Session>,
     turn_context: Arc<TurnContext>,
     initial_context_injection: InitialContextInjection,
+    reason: CompactionReason,
+    phase: CompactionPhase,
 ) -> CodexResult<()> {
-    run_remote_compact_task_inner(&sess, &turn_context, initial_context_injection).await?;
+    run_remote_compact_task_inner(
+        &sess,
+        &turn_context,
+        initial_context_injection,
+        CompactionTrigger::Auto,
+        reason,
+        phase,
+    )
+    .await?;
     Ok(())
 }
 
@@ -46,17 +62,44 @@ pub(crate) async fn run_remote_compact_task(
     });
     sess.send_event(&turn_context, start_event).await;
 
-    run_remote_compact_task_inner(&sess, &turn_context, InitialContextInjection::DoNotInject).await
+    run_remote_compact_task_inner(
+        &sess,
+        &turn_context,
+        InitialContextInjection::DoNotInject,
+        CompactionTrigger::Manual,
+        CompactionReason::UserRequested,
+        CompactionPhase::StandaloneTurn,
+    )
+    .await
 }
 
 async fn run_remote_compact_task_inner(
     sess: &Arc<Session>,
     turn_context: &Arc<TurnContext>,
     initial_context_injection: InitialContextInjection,
+    trigger: CompactionTrigger,
+    reason: CompactionReason,
+    phase: CompactionPhase,
 ) -> CodexResult<()> {
-    if let Err(err) =
-        run_remote_compact_task_inner_impl(sess, turn_context, initial_context_injection).await
-    {
+    let attempt = CompactionAnalyticsAttempt::begin(
+        sess.as_ref(),
+        turn_context.as_ref(),
+        trigger,
+        reason,
+        CompactionImplementation::ResponsesCompact,
+        phase,
+    )
+    .await;
+    let result =
+        run_remote_compact_task_inner_impl(sess, turn_context, initial_context_injection).await;
+    attempt
+        .track(
+            sess.as_ref(),
+            compaction_status_from_result(&result),
+            result.as_ref().err().map(ToString::to_string),
+        )
+        .await;
+    if let Err(err) = result {
         let event = EventMsg::Error(
             err.to_error_event(Some("Error running remote compact task".to_string())),
         );