fix(models): use implementAsync for async z.function occurrences

Author: matejchalk

packages/models/src/lib/implementation/function.ts

@@ -1,8 +1,49 @@
 import { z } from 'zod/v4';
 import type { $ZodFunction } from 'zod/v4/core';
 
+// https://zod.dev/v4/changelog?id=zfunction
+// https://github.com/colinhacks/zod/issues/4143#issuecomment-2931729793
 // https://github.com/matejchalk/zod2md?tab=readme-ov-file#function-schemas
-export function convertZodFunctionToSchema<T extends $ZodFunction>(factory: T) {
+
+/**
+ * Converts Zod v4 function factory (returned by `z.function`) to Zod schema.
+ *
+ * Supports asynchronous functions. For synchronous functions, you can use {@link convertSyncZodFunctionToSchema}.
+ *
+ * @param factory `z.function({  input: [...], output: ... })`
+ * @returns Zod schema with compile-time and runtime validations.
+ */
+export function convertAsyncZodFunctionToSchema<T extends $ZodFunction>(
+  factory: T,
+) {
+  return z
+    .custom()
+    .transform((arg, ctx) => {
+      if (typeof arg !== 'function') {
+        ctx.addIssue(`Expected function, received ${typeof arg}`);
+        return z.NEVER;
+      }
+      return factory.implementAsync(arg as Parameters<T['implementAsync']>[0]);
+    })
+    .meta({
+      // enables zod2md to include function signature in docs
+      $ZodFunction: factory,
+    });
+}
+
+/**
+ * Converts Zod v4 function factory (returned by `z.function`) to Zod schema.
+ *
+ * **IMPORTANT!** Use for synchronous functions only. For asynchronous functions use {@link convertAsyncZodFunctionToSchema}.
+ *
+ * @throws `Encountered Promise during synchronous parse. Use .parseAsync() instead.` if used with async functions.
+ *
+ * @param factory `z.function({  input: [...], output: ... })`
+ * @returns Zod schema with compile-time and runtime validations.
+ */
+export function convertSyncZodFunctionToSchema<T extends $ZodFunction>(
+  factory: T,
+) {
   return z
     .custom()
     .transform((arg, ctx) => {

packages/models/src/lib/runner-config.ts

@@ -1,9 +1,9 @@
 import { z } from 'zod/v4';
 import { auditOutputsSchema } from './audit-output.js';
-import { convertZodFunctionToSchema } from './implementation/function.js';
+import { convertAsyncZodFunctionToSchema } from './implementation/function.js';
 import { filePathSchema } from './implementation/schemas.js';
 
-export const outputTransformSchema = convertZodFunctionToSchema(
+export const outputTransformSchema = convertAsyncZodFunctionToSchema(
   z.function({
     input: [z.unknown()],
     output: z.union([auditOutputsSchema, z.promise(auditOutputsSchema)]),
@@ -23,7 +23,7 @@ export const runnerConfigSchema = z
 
 export type RunnerConfig = z.infer<typeof runnerConfigSchema>;
 
-export const runnerFunctionSchema = convertZodFunctionToSchema(
+export const runnerFunctionSchema = convertAsyncZodFunctionToSchema(
   z.function({
     output: z.union([auditOutputsSchema, z.promise(auditOutputsSchema)]),
   }),