[codex] Initialize exec-server OpenTelemetry at startup (#25019)

## Summary

- Initialize stderr tracing and the configured OpenTelemetry provider
for local and remote `codex exec-server` startup.
- Instrument the local and remote server entrypoints with a root runtime
span.
- Keep raw Noise environment, registration, and stream identifiers out
of exported spans while preserving them in local debug events.
- Keep telemetry setup in a focused CLI module instead of growing the
top-level command entrypoint.

## Stack

- Previous: none (`#27058` has merged)
- Next: #27466

## Validation

- `just test -p codex-exec-server --lib` (139 passed)
- `just test -p codex-cli --test exec_server` (3 passed)
- `just bazel-lock-check`
- `just fix -p codex-exec-server -p codex-cli`
- `just fmt`

---------

Co-authored-by: Richard Lee <richardlee@openai.com>

codex-rs/cli/src/exec_server_telemetry.rs

@@ -0,0 +1,41 @@
+use tracing_subscriber::EnvFilter;
+use tracing_subscriber::prelude::*;
+
+const DEFAULT_ANALYTICS_ENABLED: bool = false;
+const DEFAULT_LOG_FILTER: &str = "error,opentelemetry_sdk=off,opentelemetry_otlp=off";
+const OTEL_SERVICE_NAME: &str = "codex-exec-server";
+
+pub(crate) fn init(
+    config: Option<&codex_core::config::Config>,
+) -> Result<impl Send + Sync, Box<dyn std::error::Error>> {
+    let fmt_layer = tracing_subscriber::fmt::layer()
+        .with_writer(std::io::stderr)
+        .with_filter(stderr_env_filter());
+    let otel = match config {
+        Some(config) => codex_core::otel_init::build_provider(
+            config,
+            env!("CARGO_PKG_VERSION"),
+            Some(OTEL_SERVICE_NAME),
+            DEFAULT_ANALYTICS_ENABLED,
+        ),
+        None => Ok(None),
+    };
+    let provider = otel.as_ref().ok().and_then(Option::as_ref);
+    codex_core::otel_init::record_process_start(provider, OTEL_SERVICE_NAME);
+
+    let otel_logger_layer = provider.and_then(|otel| otel.logger_layer());
+    let otel_tracing_layer = provider.and_then(|otel| otel.tracing_layer());
+    let _ = tracing_subscriber::registry()
+        .with(fmt_layer)
+        .with(otel_tracing_layer)
+        .with(otel_logger_layer)
+        .try_init();
+    tracing::callsite::rebuild_interest_cache();
+    otel
+}
+
+fn stderr_env_filter() -> EnvFilter {
+    EnvFilter::try_from_default_env()
+        .or_else(|_| EnvFilter::try_new(DEFAULT_LOG_FILTER))
+        .unwrap_or_else(|_| EnvFilter::new("error"))
+}

codex-rs/cli/src/main.rs

@@ -49,6 +49,7 @@ mod app_cmd;
 #[cfg(any(target_os = "macos", target_os = "windows"))]
 mod desktop_app;
 mod doctor;
+mod exec_server_telemetry;
 mod marketplace_cmd;
 mod mcp_cmd;
 mod plugin_cmd;
@@ -1692,6 +1693,9 @@ async fn run_exec_server_command(
             .environment_id
             .ok_or_else(|| anyhow::anyhow!("--environment-id is required when --remote is set"))?;
         let config = load_exec_server_config(root_config_overrides, strict_config).await?;
+        let _otel = exec_server_telemetry::init(Some(&config))
+            .inspect_err(|err| eprintln!("Could not create otel exporter: {err}"))
+            .ok();
         let auth_provider =
             load_exec_server_remote_auth_provider(&config, &base_url, cmd.use_agent_identity_auth)
                 .await?;
@@ -1706,12 +1710,15 @@ async fn run_exec_server_command(
         codex_exec_server::run_remote_environment(remote_config, runtime_paths).await?;
         Ok(())
     } else {
-        if strict_config {
-            // Local exec-server startup does not consume Config, but strict
-            // mode should still reject unknown fields before opening a listener.
-            let _validated_config =
-                load_exec_server_config(root_config_overrides, strict_config).await?;
-        }
+        let config_result = load_exec_server_config(root_config_overrides, strict_config).await;
+        let config = if strict_config {
+            Some(config_result?)
+        } else {
+            config_result.ok()
+        };
+        let _otel = exec_server_telemetry::init(config.as_ref())
+            .inspect_err(|err| eprintln!("Could not create otel exporter: {err}"))
+            .ok();
         let listen_url = cmd
             .listen
             .as_deref()

codex-rs/cli/tests/exec_server.rs

@@ -1,6 +1,7 @@
 use std::path::Path;
 
 use anyhow::Result;
+use predicates::prelude::PredicateBooleanExt;
 use predicates::str::contains;
 use tempfile::TempDir;
 
@@ -33,3 +34,17 @@ foo = "bar"
 
     Ok(())
 }
+
+#[test]
+fn local_exec_server_ignores_invalid_config_without_strict_config() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    std::fs::write(codex_home.path().join("config.toml"), "not valid toml = [")?;
+
+    let mut cmd = codex_command(codex_home.path())?;
+    cmd.args(["exec-server", "--listen", "stdio"])
+        .assert()
+        .success()
+        .stderr(contains("not valid toml").not());
+
+    Ok(())
+}