Frontend RPC

frontend_rpc calls a handler your web page registered, sends it a payload, waits for its answer, and can publish fields out of that answer. Use it to let the agent fill in a form, highlight a product, navigate the page, or read state only the browser has. It works on web calls only.

{
  "kind": "frontend_rpc",
  "config": {
    "method": "fill_signup_form",
    "payload": { "name": "{{args.full_name}}", "email": "{{args.email}}" },
    "timeout": 5
  },
  "silent": true,
  "publish_fields": [{ "path": "ok", "key": "filled", "store": "tooldata" }]
}

The handler in the page, registered with useTalqingRpcHandlers from @talqing/react inside your Talqing call context:

import { useTalqingRpcHandlers } from "@talqing/react";

function CallSurface() {
  useTalqingRpcHandlers({
    fill_signup_form: async ({ payload }) => {
      const fields = JSON.parse(payload);
      const ok = form.setValues(fields);
      return JSON.stringify({ ok });
    },
  });
  return <SignupForm />;
}

Config

Field	Type	Default	Meaning
`method`	string	required	The handler name, matching `^[A-Za-z_][A-Za-z0-9_.-]*$`, so `cart.add` is valid
`payload`	any JSON	`null`	Templated, then sent to the handler
`timeout`	number, seconds	`5`	Above 0, at most 60

Like http and code, it takes silent, publish_fields and background_execution.

The contract with the page

The agent sends one RPC method, talqing.frontend_rpc, with the envelope {"method": "...", "payload": ...}. The browser SDK registers that method when you call useTalqingRpcHandlers and dispatches on method; you never register talqing.frontend_rpc yourself.

A handler receives { payload }, where payload is the JSON-encoded payload string, and must return a string.
The answer is parsed as JSON and becomes the operation’s result. A string that is not JSON becomes {"result": "<the string>"}, so "ok" is still publishable.
A "*" key catches every method with no handler of its own and receives the whole envelope as its payload.
Throw TalqingRpcError(code, message) from @talqing/client to choose the error code the agent sees.

useTalqingFrontendRpcs() registers a catch-all that records the latest payload per method and answers "ok", for a debug panel while building.

When it fails

Each of these fails the operation, and on_error decides what happens next. For cosmetic effects like a highlight, on_error: "continue" is usually right.

Situation	Error
No handler for that method	RPC error `1404`, `No frontend RPC handler registered for <method>`
The handler throws	RPC error `1500` with its message
No answer within `timeout`	The RPC times out
A text conversation	`frontend_rpc is unavailable for text runs`
A phone call, or no browser connected	`frontend_rpc has no connected web client participant`
Several browsers in the call	`frontend_rpc has multiple web clients but no target identity`

None of these is caught at publish, because one tool can be attached to a web agent and a phone agent. If the tree should branch on a handler’s outcome, return it in the answer instead of throwing. For one-way UI effects, background_execution: true sends the call without waiting; nothing is published. In a test run the operation is simulated and reports the method and resolved payload. Testing the handler itself needs a web call.

Web call features

Frontend actions alongside images and screen share.

React SDK

useTalqingRpcHandlers and the other hooks.

Get started

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Guides

Config

The contract with the page

When it fails

Next

Web call features

React SDK

​Config

​The contract with the page

​When it fails

​Next

Web call features

React SDK

Config

The contract with the page

When it fails

Next