# 11 Dynamic Selector

Script: `example/11_dynamic_selector.py`.

OpenRath v1.2.1 adds `flow.Selector`, an LLM-backed routing decision over
self-describing workflows. The selector returns a `Workflow`; your Python code
decides whether and when to call it.

```python
from rath import flow
from rath.session import Session

selector = flow.Selector(provider)
billing = flow.Agent(
    "Handle billing questions briefly.",
    provider,
    description="Billing, invoices, refunds, payment methods",
)
technical = flow.Agent(
    "Solve technical problems briefly.",
    provider,
    description="Installation, errors, configuration, troubleshooting",
)

session = Session.from_user_message("My invoice was charged twice.").to("local")
chosen = selector.forward(session, billing, technical)
if not isinstance(chosen, flow.EmptyWorkflow):
    session = chosen(session)
```

The same decision can drive a bounded loop:

```python
rounds = 0
while not isinstance(
    chosen := selector.forward(session, technical, billing),
    flow.EmptyWorkflow,
):
    session = chosen(session)
    rounds += 1
    if rounds >= 4:
        break
```

| API | v1.2.1 behavior |
| --- | --- |
| `Workflow(description="...")` | Stores the routing description. `Agent` and `Compressor` expose the same keyword. |
| `Selector.forward(session, *workflows)` | Returns one candidate `Workflow` or `EmptyWorkflow`; it does not return a `Session`. |
| `EmptyWorkflow.forward(session)` | Returns the same session unchanged. |
| `select_session(...)` | Returns `(zero_based_index, description)` or `(-1, "")` and does not create lineage. |

OpenRath v1.2.2 adds the `Session.text()` accessor used by the shipped example:

```python
print(session.text())  # latest non-empty assistant text, or None
```

`Selector.__init__` still accepts `on_event`, but the v1.3.0 selection call does
not forward that callback. Do not rely on streamed selector events in this
version.

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