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# add_per_call_config

> Register a per-request configuration callback without replacing callbacks already set.

[ref-agentbase]: /docs/server-sdks/reference/python/agents/agent-base

[set-dynamic-config-callback]: /docs/server-sdks/reference/python/agents/agent-base/set-dynamic-config-callback

Register a per-request configuration callback, keeping any already registered.
Same signature and contract as
[`set_dynamic_config_callback()`][set-dynamic-config-callback], except that
callbacks accumulate instead of overwriting. They run in registration order
against the same ephemeral agent, so a later callback sees what an earlier one
configured and can build on or override it.

Prefer this form when composing. A base class and a subclass, or an agent and a
mixin, can each register what they own without knowing about the other. With
`set_dynamic_config_callback()` the second registration silently drops the
first.

## Parameters

**`callback`** `Callable[[dict[str, Any], dict[str, Any], dict[str, Any], Any], None]` — required

A function with the signature `(query_params, body_params, headers, agent)`.
`agent` is the ephemeral per-request copy. Configure that object, never
`self`, or the configuration leaks across callers.

---

## Returns

[`AgentBase`][ref-agentbase] -- Returns self for method chaining.

## Example

```python {6-14}
from signalwire import AgentBase

agent = AgentBase(name="dispatch", route="/dispatch")
agent.set_prompt_text("You are Ada, the dispatcher for Bayview Taxi.")

def pick_language(query_params, body_params, headers, agent):
    if query_params.get("lang") == "es":
        agent.add_language("Spanish", "es-MX", "rime.marsh")

def tag_tenant(query_params, body_params, headers, agent):
    agent.set_global_data({"tenant": query_params.get("tenant", "default")})

agent.add_per_call_config(pick_language)
agent.add_per_call_config(tag_tenant)

agent.serve()
```

> Register a per-request configuration callback without replacing callbacks already set.