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/Cargo.toml

@@ -21,6 +21,7 @@ members = [
     "protocol-ts",
     "rmcp-client",
     "responses-api-proxy",
+    "otel",
     "tui",
     "utils/readiness",
 ]
@@ -55,6 +56,7 @@ codex-protocol = { path = "protocol" }
 codex-protocol-ts = { path = "protocol-ts" }
 codex-rmcp-client = { path = "rmcp-client" }
 codex-tui = { path = "tui" }
+codex-otel = { path = "otel" }
 codex-utils-readiness = { path = "utils/readiness" }
 core_test_support = { path = "core/tests/common" }
 mcp-types = { path = "mcp-types" }
@@ -103,6 +105,11 @@ mime_guess = "2.0.5"
 multimap = "0.10.0"
 nucleo-matcher = "0.3.1"
 openssl-sys = "*"
+opentelemetry = "0.30.0"
+opentelemetry_sdk = "0.30.0"
+opentelemetry-otlp = "0.30.0"
+opentelemetry-appender-tracing = "0.30.0"
+opentelemetry-semantic-conventions = "0.30.0"
 os_info = "3.12.0"
 owo-colors = "4.2.0"
 path-absolutize = "3.1.1"
@@ -144,9 +151,11 @@ toml_edit = "0.23.4"
 tracing = "0.1.41"
 tracing-appender = "0.2.3"
 tracing-subscriber = "0.3.20"
+tracing-test = "0.2.5"
 tree-sitter = "0.25.9"
 tree-sitter-bash = "0.25.0"
 ts-rs = "11"
+tonic = "0.13.1"
 unicode-segmentation = "1.12.0"
 unicode-width = "0.2"
 url = "2"