Tool input type of unkown

Product Help LangChain
1

I am trying to use zod 4 with tools in my langgraph application however im loosing all my type inference on the input to my tool.


import { tool } from “@langchain/core/tools”;
import { z } from “zod/v4”;

//(parameter) input: unknown
const testTool = tool(async (input, config) => {
...
  }, 
  {
    name: ‘test’,
    description: ‘test’,
    schema: z.object({
      testKey: z.string()
    })
})

I see that there seems to be support for zod4 but can track down the issue causing this


//@langchain/core/dist/tools/index.d.ts
export declare function tool<SchemaT extends ZodStringV3, ToolOutputT = ToolOutputType>(func: RunnableFunc<InferInteropZodOutput<SchemaT>, ToolOutputT, ToolRunnableConfig>, fields: ToolWrapperParams<SchemaT>): DynamicTool<ToolOutputT>; export declare function tool<SchemaT extends ZodStringV4, ToolOutputT = ToolOutputType>(func: RunnableFunc<InferInteropZodOutput<SchemaT>, ToolOutputT, ToolRunnableConfig>, fields: ToolWrapperParams<SchemaT>): DynamicTool<ToolOutputT>;
export declare function tool<SchemaT extends ZodObjectV3, SchemaOutputT = InferInteropZodOutput<SchemaT>, SchemaInputT = InferInteropZodInput<SchemaT>, ToolOutputT = ToolOutputType>(func: RunnableFunc<SchemaOutputT, ToolOutputT, ToolRunnableConfig>, fields: ToolWrapperParams<SchemaT>): DynamicStructuredTool<SchemaT, SchemaOutputT, SchemaInputT, ToolOutputT>;
export declare function tool<SchemaT extends ZodObjectV4, SchemaOutputT = InferInteropZodOutput<SchemaT>, SchemaInputT = InferInteropZodInput<SchemaT>, ToolOutputT = ToolOutputType>(func: RunnableFunc<SchemaOutputT, ToolOutputT, ToolRunnableConfig>, fields: ToolWrapperParams<SchemaT>): DynamicStructuredTool<SchemaT, SchemaOutputT, SchemaInputT, ToolOutputT>;
export declare function tool<SchemaT extends JSONSchema, SchemaOutputT = ToolInputSchemaOutputType<SchemaT>, SchemaInputT = ToolInputSchemaInputType<SchemaT>, ToolOutputT = ToolOutputType>(func: RunnableFunc<Parameters<DynamicStructuredToolInput<SchemaT>["func"]>[0], ToolOutputT, ToolRunnableConfig>, fields: ToolWrapperParams<SchemaT>): DynamicStructuredTool<SchemaT, SchemaOutputT, SchemaInputT, ToolOutputT>;

Package versions
“@langchain/core”: “^0.3.72”,
“@langchain/langgraph”: “^0.4.8”,
“@langchain/openai”: “^0.6.9”,
“zod”: “^4.1.5”,

Any help would be appreciated