Proto Definitions

Language-agnostic protobuf definitions for PostHog services.

Structure

text

proto/
├── buf.yaml
├── kafka_assigner/       # Kafka partition assignment
└── personhog/            # Person data service
    ├── types/v1/
    ├── replica/v1/
    └── service/v1/

Consumers

Proto	Rust	Python
`personhog/`	`rust/personhog-proto` (auto via tonic)	`posthog/personhog_client/proto/generated/` (checked in)
`kafka_assigner/`	`rust/kafka-assigner-proto` (auto via tonic)	—

Updating protos

Edit .proto files in the relevant directory
Regenerate language bindings for affected consumers (see table above)
Commit generated files — CI rejects stale stubs

Python stubs (personhog only)

bash

bin/generate_personhog_proto.sh

Only needed when personhog/ protos change. Requires grpcio-tools and protoletariat (uv sync).

If you added or removed message types, update the re-exports in posthog/personhog_client/proto/__init__.py. If you added or removed RPCs, update the wrapper methods in posthog/personhog_client/client.py.

Rust

No action needed — Rust bindings regenerate on cargo build.

CI

.github/workflows/ci-proto.yml runs on proto changes:

buf lint — style and naming
buf breaking — backwards compatibility against master
Python codegen staleness check