Type●Since v1.6

WhenPredicate

Predicate controlling whether a given tool call triggers an interrupt.

Receives a ToolCallRequest and returns true to interrupt or false to auto-approve the tool call.

The request is constructed with tool set to undefined and runtime set to the node-level Runtime, so it reflects the batch (afterModel) context rather than a per-call tool execution. In "per_call" mode the predicate runs in wrapToolCall and receives the real request, with tool set.

In both modes the predicate runs again when the run resumes, so it must return the same answer for the same call. If it returns false on resume, the reviewer's answer is skipped and the tool runs, even if they rejected it.

WhenPredicate: z.infer<typeof WhenFunctionSchema>

Example

import { type WhenPredicate } from "langchain";

// Only interrupt delete_file calls targeting /etc
const when: WhenPredicate = (request) =>
  String(request.toolCall.args.path ?? "").startsWith("/etc");

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WhenPredicate

Example

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WhenPredicate

Example