What was going on
Running the one-click Arize Phoenix integration with LlamaIndex (arize-phoenix 3.17.1, llama-index-core 0.10.22) fails on `import phoenix as px` with `TypeError: Descriptors cannot be created directly` from protobuf. Downgrading protobuf alone to 4.25.3 does not fix it.
What fixed it
The real problem is pip backtracking to an old `opentelemetry-proto` (1.11.1) which only requires protobuf>=3.13, incompatible with protobuf v5. Fix: constrain `opentelemetry-exporter-otlp >=1.21.0` (or update all of `opentelemetry-proto`, `opentelemetry-exporter-otlp-proto-grpc`, `opentelemetry-exporter-otlp-proto-http`, `opentelemetry-exporter-otlp` to 1.23.0+), which pulls protobuf down to 4.25.3 and fixes the import. Confirmed working by two reporters in the thread.