diff --git a/examples/tsconfig.json b/examples/tsconfig.json
index 8350c33e..828e281f 100644
--- a/examples/tsconfig.json
+++ b/examples/tsconfig.json
@@ -7,5 +7,5 @@
     "noEmit": true,
     "skipLibCheck": true
   },
-  "include": ["generated/**/*.ts", "generated-rq/**/*.ts", "verify.test.ts"]
+  "include": ["generated/**/*.ts", "generated-rq/**/*.ts", "verify.test.ts", "type-assertions.ts"]
 }
diff --git a/examples/type-assertions.ts b/examples/type-assertions.ts
new file mode 100644
index 00000000..541474df
--- /dev/null
+++ b/examples/type-assertions.ts
@@ -0,0 +1,183 @@
+// Compile-time assertions: generated inferred types must contain no unknown in named fields.
+//
+// Why: the existing property test checks generated source text for the "unknown" substring.
+// That proxy does NOT catch #383: a bare `z.lazy(() => ...): z.ZodType` collapses z.infer<>
+// to unknown without the word "unknown" appearing in source. This file checks the INFERRED
+// TypeScript types directly, recursively, at compile time.
+//
+// Zod v4 `.passthrough()` emits `{ [k: string]: unknown }` as an index signature on the
+// inferred type (the $loose config). That is intentional and must NOT be flagged. The
+// NamedKeys helper filters out wide string/number index signatures so only explicitly
+// declared named properties are checked.
+//
+// Note on mutually recursive types (Holiday <-> Province): TypeScript 6's conditional type
+// evaluator returns `boolean` (not `false`) when it encounters a recursive cycle, regardless
+// of depth-limiting tricks. `[boolean] extends [false]` is false, so AssertNoUnknown would
+// produce a false positive on these clean interfaces. For those types we use (a) Pick<> over
+// the non-cyclic leaf fields to exercise the full machinery, and (b) a direct IsUnknownExact
+// check for the z.infer<> result (the specific regression shape for #383).
+
+import type { z } from 'zod'
+import type { Holiday, Province } from './generated/canada_holidays/models.js'
+import {
+  HolidaySchema,
+  ProvinceSchema,
+  RootSchema,
+  ErrorSchema,
+} from './generated/canada_holidays/schemas.js'
+import type { Email, Attachment, Domain, DomainRecord } from './generated/resend/models.js'
+import {
+  EmailSchema,
+  AttachmentSchema,
+  DomainSchema,
+  DomainRecordSchema,
+} from './generated/resend/schemas.js'
+import type { ArtistObject, TrackObject, AudioFeaturesObject } from './generated/spotify/models.js'
+import {
+  ArtistObjectSchema,
+  TrackObjectSchema,
+  AudioFeaturesObjectSchema,
+} from './generated/spotify/schemas.js'
+
+// ---------------------------------------------------------------------------
+// Type machinery
+// ---------------------------------------------------------------------------
+
+type IsAny<T> = 0 extends 1 & T ? true : false
+type IsUnknownExact<T> = IsAny<T> extends true ? false : unknown extends T ? true : false
+// Real declared keys only: drop the wide string/number index signature from passthrough.
+type NamedKeys<T> = {
+  [K in keyof T]: string extends K ? never : number extends K ? never : K
+}[keyof T]
+type DeepHasUnknown<T> =
+  IsUnknownExact<T> extends true
+    ? true
+    : IsAny<T> extends true
+      ? false
+      : T extends (...args: never[]) => unknown
+        ? false
+        : T extends readonly (infer E)[]
+          ? DeepHasUnknown<E>
+          : T extends object
+            ? true extends { [K in NamedKeys<T>]-?: DeepHasUnknown<T[K]> }[NamedKeys<T>]
+              ? true
+              : false
+            : false
+
+// If T has no unknown in named fields, this is `true`.
+// If T leaks unknown in a named field, this becomes `{ __UNKNOWN_LEAKED__: T }`, so `= true` fails to compile.
+type AssertNoUnknown<T> = [DeepHasUnknown<T>] extends [false] ? true : { __UNKNOWN_LEAKED__: T }
+
+// ---------------------------------------------------------------------------
+// #383: canada_holidays cyclic schemas
+//
+// HolidaySchema and ProvinceSchema are annotated as `z.ZodType<Holiday>` and
+// `z.ZodType<Province>` with z.lazy() to handle the mutual cycle. Before #383,
+// a bare `z.lazy(() => z.object(...)): z.ZodType` collapsed z.infer<> to unknown.
+// After #383 the type parameter is explicit, so z.infer<> resolves to the full
+// interface.
+//
+// Because Holiday <-> Province form a mutual cycle, TypeScript 6's conditional type
+// evaluator returns `boolean` for DeepHasUnknown<Holiday>, causing a false positive
+// with AssertNoUnknown. We handle this with two complementary checks:
+// (a) AssertNoUnknown over Pick<> of each type's non-cyclic leaf fields (exercises the
+//     full machinery and confirms individual field types are concrete).
+// (b) A direct IsUnknownExact assertion proving z.infer<typeof HolidaySchema> is NOT
+//     the `unknown` top-level type, which is exactly the regression shape for #383.
+//
+// RootSchema and ErrorSchema are non-cyclic, so they use AssertNoUnknown directly.
+// ---------------------------------------------------------------------------
+
+// (a) Non-cyclic leaf fields of Holiday and Province
+const _holidayLeafFields: AssertNoUnknown<
+  Pick<Holiday, 'date' | 'federal' | 'id' | 'nameEn' | 'nameFr' | 'observedDate'>
+> = true
+const _provinceLeafFields: AssertNoUnknown<
+  Pick<Province, 'id' | 'nameEn' | 'nameFr' | 'sourceEn' | 'sourceLink'>
+> = true
+
+// (b) Top-level: z.infer<typeof HolidaySchema> must NOT be `unknown` (the #383 regression shape).
+// HolidaySchema: z.ZodType<Holiday> -- z.infer<> gives Holiday, not unknown.
+type _HolidayInferredIsNotUnknown =
+  IsUnknownExact<z.infer<typeof HolidaySchema>> extends false ? true : never
+type _ProvinceInferredIsNotUnknown =
+  IsUnknownExact<z.infer<typeof ProvinceSchema>> extends false ? true : never
+const _holidayInferNotUnknown: _HolidayInferredIsNotUnknown = true
+const _provinceInferNotUnknown: _ProvinceInferredIsNotUnknown = true
+
+// Non-cyclic synthesized response schemas: full AssertNoUnknown applies.
+const _rootInferred: AssertNoUnknown<z.infer<typeof RootSchema>> = true
+const _errorInferred: AssertNoUnknown<z.infer<typeof ErrorSchema>> = true
+
+// ---------------------------------------------------------------------------
+// #390: resend nullable arrays and object-null nullable fields
+//
+// EmailSchema.bcc / cc / reply_to were previously emitted as nullable arrays
+// that collapsed to `unknown | null` in z.infer<>. After the fix they are
+// `z.array(z.string()).optional()`, which infers to `string[] | undefined`.
+// DomainSchema and DomainRecordSchema cover the object-null nullable case:
+// fields like `status` and `ttl` are nullable primitives (string | null), not unknown.
+// ---------------------------------------------------------------------------
+
+const _emailModel: AssertNoUnknown<Email> = true
+const _emailInferred: AssertNoUnknown<z.infer<typeof EmailSchema>> = true
+const _attachmentModel: AssertNoUnknown<Attachment> = true
+const _attachmentInferred: AssertNoUnknown<z.infer<typeof AttachmentSchema>> = true
+const _domainModel: AssertNoUnknown<Domain> = true
+const _domainInferred: AssertNoUnknown<z.infer<typeof DomainSchema>> = true
+const _domainRecordModel: AssertNoUnknown<DomainRecord> = true
+const _domainRecordInferred: AssertNoUnknown<z.infer<typeof DomainRecordSchema>> = true
+
+// ---------------------------------------------------------------------------
+// Breadth: spotify (no z.unknown() fields anywhere in this example)
+//
+// Covers unions (PlaylistTrackObjectSchema uses union([TrackObjectSchema, EpisodeObjectSchema])),
+// nested objects (ArtistObject has followers and images arrays), and numeric primitives
+// (AudioFeaturesObject). All three have rich schemas with zero z.unknown() usage.
+// ---------------------------------------------------------------------------
+
+const _artistModel: AssertNoUnknown<ArtistObject> = true
+const _artistInferred: AssertNoUnknown<z.infer<typeof ArtistObjectSchema>> = true
+const _trackModel: AssertNoUnknown<TrackObject> = true
+const _trackInferred: AssertNoUnknown<z.infer<typeof TrackObjectSchema>> = true
+const _audioFeaturesModel: AssertNoUnknown<AudioFeaturesObject> = true
+const _audioFeaturesInferred: AssertNoUnknown<z.infer<typeof AudioFeaturesObjectSchema>> = true
+
+// ---------------------------------------------------------------------------
+// Self-tests: prove DeepHasUnknown actually fires
+//
+// Rule: @ts-expect-error suppresses the compile error. If the assertion does NOT
+// produce an error (i.e. DeepHasUnknown returned false when it should return true),
+// TypeScript reports "Unused '@ts-expect-error' directive" and typecheck fails.
+// That is the guard that makes these tests non-vacuous.
+// ---------------------------------------------------------------------------
+
+// 1. Named field containing unknown nested in an array: must be flagged.
+//    DeepHasUnknown<_L1>: _L1.a = {b: unknown[]} -> .b = unknown[] -> element = unknown -> true.
+interface _L1 {
+  a: { b: unknown[] }
+}
+// @ts-expect-error - _L1 has unknown nested in a named array property
+const _teeth1: AssertNoUnknown<_L1> = true
+
+// 2. Unknown inside a union member of a named field: must be flagged.
+//    DeepHasUnknown<{u: string | {deep: unknown}}>: distributes to false | true = boolean.
+//    [boolean] extends [false] = false, so AssertNoUnknown = { __UNKNOWN_LEAKED__ }.
+//    The @ts-expect-error is satisfied; if the detector ever stopped flagging unknowns
+//    in unions, TypeScript would instead return `true` here and the directive would be
+//    unused, failing the typecheck.
+// @ts-expect-error - the union member { deep: unknown } leaks unknown
+const _teeth2: AssertNoUnknown<{ u: string | { deep: unknown } }> = true
+
+// 3. Whole-type unknown: must be flagged. This is exactly the pre-#383 shape
+//    where z.infer<z.ZodType> without a type parameter collapsed to unknown.
+// @ts-expect-error - the top-level type IS unknown
+const _teeth3: AssertNoUnknown<unknown> = true
+
+// 4. Passthrough-like type with wide index signature: must PASS without @ts-expect-error.
+//    NamedKeys<_Loose> = only 'a' (the string index signature is excluded), so
+//    DeepHasUnknown checks only `a: string` which is not unknown.
+//    This proves the passthrough catchall is correctly ignored: without NamedKeys the
+//    index `[k: string]: unknown` would be checked and every generated schema would fail.
+type _Loose = { a: string } & { [k: string]: unknown }
+const _teeth4: AssertNoUnknown<_Loose> = true