feat: show runtime metrics in console (#10278)

Summary of changes:

- Adds a new feature flag: runtime_metrics
  - Declared in core/src/features.rs
  - Added to core/config.schema.json
  - Wired into OTEL init in core/src/otel_init.rs

- Enables on-demand runtime metric snapshots in OTEL
  - Adds runtime_metrics: bool to otel/src/config.rs
  - Enables experimental custom reader features in otel/Cargo.toml
  - Adds snapshot/reset/summary APIs in:
    - otel/src/lib.rs
    - otel/src/metrics/client.rs
    - otel/src/metrics/config.rs
    - otel/src/metrics/error.rs

- Defines metric names and a runtime summary builder
  - New files:
    - otel/src/metrics/names.rs
    - otel/src/metrics/runtime_metrics.rs
  - Summarizes totals for:
    - Tool calls
    - API requests
    - SSE/streaming events

- Instruments metrics collection in OTEL manager
  - otel/src/traces/otel_manager.rs now records:
    - API call counts + durations
    - SSE event counts + durations (success/failure)
    - Tool call metrics now use shared constants

- Surfaces runtime metrics in the TUI
  - Resets runtime metrics at turn start in tui/src/chatwidget.rs
- Displays metrics in the final separator line in
tui/src/history_cell.rs

- Adds tests
  - New OTEL tests:
    - otel/tests/suite/snapshot.rs
    - otel/tests/suite/runtime_summary.rs
  - New TUI test:
- final_message_separator_includes_runtime_metrics in
tui/src/history_cell.rs

Scope:
- 19 files changed
- ~652 insertions, 38 deletions


<img width="922" height="169" alt="Screenshot 2026-01-30 at 4 11 34 PM"
src="https://github.com/user-attachments/assets/1efd754d-a16d-4564-83a5-f4442fd2f998"
/>

codex-rs/otel/tests/suite/snapshot.rs

@@ -0,0 +1,120 @@
+use crate::harness::attributes_to_map;
+use crate::harness::find_metric;
+use codex_app_server_protocol::AuthMode;
+use codex_otel::OtelManager;
+use codex_otel::metrics::MetricsClient;
+use codex_otel::metrics::MetricsConfig;
+use codex_otel::metrics::Result;
+use codex_protocol::ThreadId;
+use codex_protocol::protocol::SessionSource;
+use opentelemetry_sdk::metrics::InMemoryMetricExporter;
+use opentelemetry_sdk::metrics::data::AggregatedMetrics;
+use opentelemetry_sdk::metrics::data::MetricData;
+use pretty_assertions::assert_eq;
+use std::collections::BTreeMap;
+
+#[test]
+fn snapshot_collects_metrics_without_shutdown() -> Result<()> {
+    let exporter = InMemoryMetricExporter::default();
+    let config = MetricsConfig::in_memory(
+        "test",
+        "codex-cli",
+        env!("CARGO_PKG_VERSION"),
+        exporter.clone(),
+    )
+    .with_tag("service", "codex-cli")?
+    .with_runtime_reader();
+    let metrics = MetricsClient::new(config)?;
+
+    metrics.counter(
+        "codex.tool.call",
+        1,
+        &[("tool", "shell"), ("success", "true")],
+    )?;
+
+    let snapshot = metrics.snapshot()?;
+
+    let metric = find_metric(&snapshot, "codex.tool.call").expect("counter metric missing");
+    let attrs = match metric.data() {
+        AggregatedMetrics::U64(data) => match data {
+            MetricData::Sum(sum) => {
+                let points: Vec<_> = sum.data_points().collect();
+                assert_eq!(points.len(), 1);
+                attributes_to_map(points[0].attributes())
+            }
+            _ => panic!("unexpected counter aggregation"),
+        },
+        _ => panic!("unexpected counter data type"),
+    };
+
+    let expected = BTreeMap::from([
+        ("service".to_string(), "codex-cli".to_string()),
+        ("success".to_string(), "true".to_string()),
+        ("tool".to_string(), "shell".to_string()),
+    ]);
+    assert_eq!(attrs, expected);
+
+    let finished = exporter
+        .get_finished_metrics()
+        .expect("finished metrics should be readable");
+    assert!(finished.is_empty(), "expected no periodic exports yet");
+
+    Ok(())
+}
+
+#[test]
+fn manager_snapshot_metrics_collects_without_shutdown() -> Result<()> {
+    let exporter = InMemoryMetricExporter::default();
+    let config = MetricsConfig::in_memory("test", "codex-cli", env!("CARGO_PKG_VERSION"), exporter)
+        .with_tag("service", "codex-cli")?
+        .with_runtime_reader();
+    let metrics = MetricsClient::new(config)?;
+    let manager = OtelManager::new(
+        ThreadId::new(),
+        "gpt-5.1",
+        "gpt-5.1",
+        Some("account-id".to_string()),
+        None,
+        Some(AuthMode::ApiKey),
+        true,
+        "tty".to_string(),
+        SessionSource::Cli,
+    )
+    .with_metrics(metrics);
+
+    manager.counter(
+        "codex.tool.call",
+        1,
+        &[("tool", "shell"), ("success", "true")],
+    );
+
+    let snapshot = manager.snapshot_metrics()?;
+    let metric = find_metric(&snapshot, "codex.tool.call").expect("counter metric missing");
+    let attrs = match metric.data() {
+        AggregatedMetrics::U64(data) => match data {
+            MetricData::Sum(sum) => {
+                let points: Vec<_> = sum.data_points().collect();
+                assert_eq!(points.len(), 1);
+                attributes_to_map(points[0].attributes())
+            }
+            _ => panic!("unexpected counter aggregation"),
+        },
+        _ => panic!("unexpected counter data type"),
+    };
+
+    let expected = BTreeMap::from([
+        (
+            "app.version".to_string(),
+            env!("CARGO_PKG_VERSION").to_string(),
+        ),
+        ("auth_mode".to_string(), AuthMode::ApiKey.to_string()),
+        ("model".to_string(), "gpt-5.1".to_string()),
+        ("service".to_string(), "codex-cli".to_string()),
+        ("session_source".to_string(), "cli".to_string()),
+        ("success".to_string(), "true".to_string()),
+        ("tool".to_string(), "shell".to_string()),
+    ]);
+    assert_eq!(attrs, expected);
+
+    Ok(())
+}