#27388 [Bug] arize_phoenix callback spans not exported from proxy chat completions in v1.83.10
## Bug description
When LiteLLM proxy v1.83.10 is configured with `arize_phoenix` as a `success_callback`, the callback IS invoked on each successful chat completion (verified via DEBUG logs), but the spans created inside `ArizePhoenixLogger._handle_success` never reach the Phoenix OTLP endpoint. The `BatchSpanProcessor` worker on the dedicated TracerProvider does not flush these spans even after extended idle time and even with aggressive BSP env-var tuning.
## Environment
- LiteLLM image: `ghcr.io/berriai/litellm-database:v1.83.10-stable` - Deployment: Helm chart in Kubernetes (EKS), proxy mode (FastAPI/uvicorn, async) - Phoenix: self-hosted `arize-phoenix` 14.2.0 (helm chart 6.0.7), auth enabled, OTLP HTTP endpoint at `http://arize-phoenix-svc...:6006/v1/traces` - Python 3.13
## Configuration
```yaml litellm_settings: success_callback: - arize_phoenix ```
Env vars set: - `PHOENIX_COLLECTOR_HTTP_ENDPOINT=http://arize-phoenix-svc...:6006/v1/traces` - `PHOENIX_API_KEY=<system api key>` (Phoenix has `enableAuth: true`)
## What works
- Phoenix endpoint reachable and accepts POSTs to `/v1/traces` (200 OK) - API key validates correctly - `ArizePhoenixLogger` initializes: …