---
title: "Step 2: How it runs"
description: "Session, turn, and durable steps: what you just watched, and why it survives a crash."
---

You sent one message and got one answer. Here's the model behind that, in three words.

**session** → your whole conversation (durable, can span days)
**turn** → one message you send and the work it triggers
**step** → a durable checkpoint within the turn

Each turn runs as a durable workflow, and Eve saves progress at every step. Restart in the middle of a turn and it picks up from the last completed step, without re-running your tool calls. A turn that's waiting on you (an approval, a question) resumes whenever you answer, even if that's much later.

That's why the features in the rest of this tutorial work the way they do:

- The warehouse sign-in in Step 4 parks the turn until you authorize in the browser. A few minutes is fine.
- The metric glossary in Step 6 survives across turns. State is checkpointed at step boundaries, so it sticks.
- The spend approval in Step 8 pauses the turn on your yes/no, then picks up exactly where it left off.

Your job is to author capabilities: tools, instructions, channels, skills. Eve drives the model↔tool loop and decides when a turn continues, waits, or ends. You never write that loop yourself.

→ Next: [Step 3: Query sample data](./query-sample-data)

Depth: [Execution model & durability](../advanced/execution-model-and-durability)
