> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wandb.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# What is the difference between @weave.op and weave.start_session?

[`@weave.op`](/weave/guides/tracking/tracing) traces individual Python functions and surfaces results in the **Traces** tab.

Weave's [agentic tracing](/weave/guides/tracking/trace-agents) (`weave.start_session`, `weave.start_turn`, `weave.start_llm`, `weave.start_tool`) models a full multi-turn agent conversation and surfaces results in the **Agents** tab.

Both are part of the same `weave` API — the right choice depends on whether you're tracing functions and pipelines, or a multi-turn agentic application.

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<Badge stroke shape="pill" color="orange" size="md">[Agents](/support/weave/tags/agents)</Badge><Badge stroke shape="pill" color="orange" size="md">[Tracing](/support/weave/tags/tracing)</Badge><Badge stroke shape="pill" color="orange" size="md">[weave.op](/support/weave/tags/weave-op)</Badge>