OpenTelemetry events (#2103)

### Title

## otel

Codex can emit [OpenTelemetry](https://opentelemetry.io/) **log events**
that
describe each run: outbound API requests, streamed responses, user
input,
tool-approval decisions, and the result of every tool invocation. Export
is
**disabled by default** so local runs remain self-contained. Opt in by
adding an
`[otel]` table and choosing an exporter.

```toml
[otel]
environment = "staging"   # defaults to "dev"
exporter = "none"          # defaults to "none"; set to otlp-http or otlp-grpc to send events
log_user_prompt = false    # defaults to false; redact prompt text unless explicitly enabled
```

Codex tags every exported event with `service.name = "codex-cli"`, the
CLI
version, and an `env` attribute so downstream collectors can distinguish
dev/staging/prod traffic. Only telemetry produced inside the
`codex_otel`
crate—the events listed below—is forwarded to the exporter.

### Event catalog

Every event shares a common set of metadata fields: `event.timestamp`,
`conversation.id`, `app.version`, `auth_mode` (when available),
`user.account_id` (when available), `terminal.type`, `model`, and
`slug`.

With OTEL enabled Codex emits the following event types (in addition to
the
metadata above):

- `codex.api_request`
  - `cf_ray` (optional)
  - `attempt`
  - `duration_ms`
  - `http.response.status_code` (optional)
  - `error.message` (failures)
- `codex.sse_event`
  - `event.kind`
  - `duration_ms`
  - `error.message` (failures)
  - `input_token_count` (completion only)
  - `output_token_count` (completion only)
  - `cached_token_count` (completion only, optional)
  - `reasoning_token_count` (completion only, optional)
  - `tool_token_count` (completion only)
- `codex.user_prompt`
  - `prompt_length`
  - `prompt` (redacted unless `log_user_prompt = true`)
- `codex.tool_decision`
  - `tool_name`
  - `call_id`
- `decision` (`approved`, `approved_for_session`, `denied`, or `abort`)
  - `source` (`config` or `user`)
- `codex.tool_result`
  - `tool_name`
  - `call_id`
  - `arguments`
  - `duration_ms` (execution time for the tool)
  - `success` (`"true"` or `"false"`)
  - `output`

### Choosing an exporter

Set `otel.exporter` to control where events go:

- `none` – leaves instrumentation active but skips exporting. This is
the
  default.
- `otlp-http` – posts OTLP log records to an OTLP/HTTP collector.
Specify the
  endpoint, protocol, and headers your collector expects:

  ```toml
  [otel]
  exporter = { otlp-http = {
    endpoint = "https://otel.example.com/v1/logs",
    protocol = "binary",
    headers = { "x-otlp-api-key" = "${OTLP_TOKEN}" }
  }}
  ```

- `otlp-grpc` – streams OTLP log records over gRPC. Provide the endpoint
and any
  metadata headers:

  ```toml
  [otel]
  exporter = { otlp-grpc = {
    endpoint = "https://otel.example.com:4317",
    headers = { "x-otlp-meta" = "abc123" }
  }}
  ```

If the exporter is `none` nothing is written anywhere; otherwise you
must run or point to your
own collector. All exporters run on a background batch worker that is
flushed on
shutdown.

If you build Codex from source the OTEL crate is still behind an `otel`
feature
flag; the official prebuilt binaries ship with the feature enabled. When
the
feature is disabled the telemetry hooks become no-ops so the CLI
continues to
function without the extra dependencies.

---------

Co-authored-by: Anton Panasenko <apanasenko@openai.com>

codex-rs/core/src/otel_init.rs

@@ -0,0 +1,61 @@
+use crate::config::Config;
+use crate::config_types::OtelExporterKind as Kind;
+use crate::config_types::OtelHttpProtocol as Protocol;
+use crate::default_client::ORIGINATOR;
+use codex_otel::config::OtelExporter;
+use codex_otel::config::OtelHttpProtocol;
+use codex_otel::config::OtelSettings;
+use codex_otel::otel_provider::OtelProvider;
+use std::error::Error;
+
+/// Build an OpenTelemetry provider from the app Config.
+///
+/// Returns `None` when OTEL export is disabled.
+pub fn build_provider(
+    config: &Config,
+    service_version: &str,
+) -> Result<Option<OtelProvider>, Box<dyn Error>> {
+    let exporter = match &config.otel.exporter {
+        Kind::None => OtelExporter::None,
+        Kind::OtlpHttp {
+            endpoint,
+            headers,
+            protocol,
+        } => {
+            let protocol = match protocol {
+                Protocol::Json => OtelHttpProtocol::Json,
+                Protocol::Binary => OtelHttpProtocol::Binary,
+            };
+
+            OtelExporter::OtlpHttp {
+                endpoint: endpoint.clone(),
+                headers: headers
+                    .iter()
+                    .map(|(k, v)| (k.clone(), v.clone()))
+                    .collect(),
+                protocol,
+            }
+        }
+        Kind::OtlpGrpc { endpoint, headers } => OtelExporter::OtlpGrpc {
+            endpoint: endpoint.clone(),
+            headers: headers
+                .iter()
+                .map(|(k, v)| (k.clone(), v.clone()))
+                .collect(),
+        },
+    };
+
+    OtelProvider::from(&OtelSettings {
+        service_name: ORIGINATOR.value.to_owned(),
+        service_version: service_version.to_string(),
+        codex_home: config.codex_home.clone(),
+        environment: config.otel.environment.to_string(),
+        exporter,
+    })
+}
+
+/// Filter predicate for exporting only Codex-owned events via OTEL.
+/// Keeps events that originated from codex_otel module
+pub fn codex_export_filter(meta: &tracing::Metadata<'_>) -> bool {
+    meta.target().starts_with("codex_otel")
+}