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

# Graphs

> Stateful workflows — polling state machines, checkpointing, HITL interrupts, semantic routing, topic channels.

Graph examples enact recognizable workflows on top of `Graph<S>`. Sources under [`examples/graphs/`](https://github.com/0xvasanth/cognis/tree/main/examples/graphs).

| Name                      | Scenario                                                                                                         | Source                                                                                         |
| ------------------------- | ---------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| `graphs_state_machine`    | Polling loop — check up to 5 times whether an external job is done; give up if not.                              | [src](https://github.com/0xvasanth/cognis/blob/main/examples/graphs/state_machine.rs)          |
| `graphs_with_checkpoints` | Resumable 5-step ETL pipeline — extract / validate / transform / load / notify, snapshot per step.               | [src](https://github.com/0xvasanth/cognis/blob/main/examples/graphs/graph_with_checkpoints.rs) |
| `graphs_interrupts`       | HITL pause-for-approval — agent drafts an email, graph stops before the `send` node so a reviewer can approve.   | [src](https://github.com/0xvasanth/cognis/blob/main/examples/graphs/graph_interrupts_demo.rs)  |
| `graphs_semantic_router`  | Customer-support intent routing — `"refund"` → refund\_flow, `"cancel"` → cancel\_flow, else general help.       | [src](https://github.com/0xvasanth/cognis/blob/main/examples/graphs/semantic_router.rs)        |
| `graphs_topic_channels`   | Onboarding agent that collects (name, hobbies, todo) across turns — reducers per field (last\_value vs. append). | [src](https://github.com/0xvasanth/cognis/blob/main/examples/graphs/topic_channels.rs)         |

## How to run

Most graph examples are offline (no LLM needed):

```bash theme={null}
cargo run -p cognis-examples --example graphs_state_machine
cargo run -p cognis-examples --example graphs_with_checkpoints
cargo run -p cognis-examples --example graphs_interrupts
```

## See also

<CardGroup cols={2}>
  <Card title="Graphs and state" icon="diagram-project" href="/core-ideas/graphs">
    The user guide.
  </Card>

  <Card title="Checkpointing" icon="floppy-disk" href="/graph-workflows/checkpointing">
    Time travel and resume.
  </Card>

  <Card title="Patterns → HITL approval" icon="grid" href="/patterns/hitl-approval">
    Interrupts in a real flow.
  </Card>
</CardGroup>