Learning 004: A Temporal client interceptor is also every worker's interceptor

• Date: 2026-10-10
• Source: system-feedback
• Work item: issue-3

What happened

build_worker passed TracingInterceptor() and connect() also gave it to the client. Temporal prepends client interceptors that implement the worker interface to every worker built on that client, so each activity produced two StartActivity and two RunActivity spans. The trace looked plausible until the demo's trace was counted against the activity history.

Learning

Register a Temporal interceptor in exactly one place; when the client carries it, the worker must not add another. Count spans against the authoritative record (Temporal history) in at least one test.

Action

build_worker adds the interceptor only when the client has none; tests/integration/o11y asserts one RunActivity:invoke_llm span per LLM step.