[BUG] BETA_TRACING_ENDPOINT ignores OTEL_EXPORTER_OTLP_PROTOCOL: headless sessions (desktop app, claude -p) silently drop all events and traces

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet (related: #82629, #35105)
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

With ENABLE_BETA_TRACING_DETAILED=1 and BETA_TRACING_ENDPOINT set, non-interactive sessions (Claude desktop app, claude -p, SDK / stream-json) export metrics but no events (logs) and no traces. Interactive terminal sessions with the same settings export all three normally.

The beta path replaces the logs and traces exporters with OTLP/HTTP (protobuf) exporters posting to ${BETA_TRACING_ENDPOINT}/v1/logs and /v1/traces, and ignores OTEL_EXPORTER_OTLP_PROTOCOL. If BETA_TRACING_ENDPOINT is the same gRPC endpoint as OTEL_EXPORTER_OTLP_ENDPOINT (a natural choice, e.g. http://localhost:4317), every events/traces export fails. Only metrics, which stay on the regular gRPC exporter, get through.

The failure is silent. Nothing is shown unless you run with --debug-file, and the collector reports no refused records because nothing valid arrives. In our case, every Claude desktop session disappeared from an events-based dashboard, while CLI sessions kept working.

In non-interactive mode the beta path is on whenever both variables are set. In interactive mode it is also behind a feature gate/allowlist (see #82629), which is why the two modes behave differently with identical settings.

What Should Happen?

One of:

• the beta exporters honour OTEL_EXPORTER_OTLP_PROTOCOL (or a dedicated BETA_TRACING_PROTOCOL);
• the docs state that BETA_TRACING_ENDPOINT must be an OTLP/HTTP endpoint (e.g. :4318, not :4317);
• export failures are surfaced (a warning), rather than only in --debug-file.

Error Messages/Logs

[ERROR] [3P telemetry] OTEL diag error: {"message":"Parse Error: Expected HTTP/, RTSP/ or ICE/","code":"HPE_INVALID_CONSTANT","reason":"Expected HTTP/, RTSP/ or ICE/","rawPacket": "\^@\^@\^F\^D\^@..."}

(The raw packet is an HTTP/2 SETTINGS frame from the gRPC port answering an HTTP/1.1 request. Seen 3x per run in --debug-file; no getOtlpLogExporters line is logged on this path.)

Steps to Reproduce

1. Run an OTLP collector with gRPC on :4317 and HTTP on :4318 (e.g. grafana/otel-lgtm).
2. ~/.claude/settings.json:

``json
{
"env": {
"CLAUDE_CODE_ENABLE_TELEMETRY": "1",
"OTEL_METRICS_EXPORTER": "otlp",
"OTEL_LOGS_EXPORTER": "otlp",
"OTEL_TRACES_EXPORTER": "otlp",
"OTEL_EXPORTER_OTLP_PROTOCOL": "grpc",
"OTEL_EXPORTER_OTLP_ENDPOINT": "http://localhost:4317",
"ENABLE_BETA_TRACING_DETAILED": "1",
"BETA_TRACING_ENDPOINT": "http://localhost:4317"
}
}
``

1. Run headless, keeping stdin open ~25 s so the log batch can flush before exit:

``sh
( echo '{"type":"user","message":{"role":"user","content":"reply with just: ok"}}'; sleep 25 ) \
| claude -p --input-format stream-json --output-format stream-json --verbose --debug-file d.log
``

1. Result: metrics arrive, 0 log records and 0 spans arrive, and d.log has the HPE_INVALID_CONSTANT errors above (reproduced 3/3, on 2.1.281 and 2.1.283).
2. Change only BETA_TRACING_ENDPOINT to http://localhost:4318: events and traces arrive (24 events + 1 trace, 2/2 runs).
3. Or disable the beta path with --settings '{"env":{"ENABLE_BETA_TRACING_DETAILED":"","BETA_TRACING_ENDPOINT":""}}': events arrive over gRPC (getOtlpLogExporters: types=["otlp"], protocol=grpc … First logs export: SUCCESS).

Note for anyone reproducing: unsetting the variables in the shell (env -u) is not enough, because the env block in settings.json re-applies them inside the process.

Claude Model

Not model-specific.

Is this a regression?

I don't know

Claude Code Version

2.1.283 (CLI) and 2.1.281 (bundled with Claude desktop 2.9939.2)

Platform

Claude subscription (Team)

Operating System

macOS (27.0.0, arm64)

Terminal/Shell

Claude desktop app (headless Claude Code), and claude -p from Terminal.app / zsh

Additional Information

• Related: #82629 (these variables are undocumented; the expected format of BETA_TRACING_ENDPOINT is unstated) and #35105 (OTel not exported in pipe/stream-json mode; possibly the same root cause if those users had the beta flags set).
• Workaround: set BETA_TRACING_ENDPOINT to the collector's OTLP/HTTP endpoint (http://localhost:4318).