diff --git a/packages/workflow-utils/src/__tests__/llm-extract.test.ts b/packages/workflow-utils/src/__tests__/llm-extract.test.ts
index 5d7464e..b96af35 100644
--- a/packages/workflow-utils/src/__tests__/llm-extract.test.ts
+++ b/packages/workflow-utils/src/__tests__/llm-extract.test.ts
@@ -108,7 +108,7 @@ describe("llmExtract", () => {
     expect(result.error.kind).toBe("schema_validation_failed");
   });
 
-  it("dryRun skips fetch and returns an empty stub value", async () => {
+  it("dryRun skips fetch and returns schema-shaped stub values", async () => {
     const fetchMock = vi.fn();
     vi.stubGlobal("fetch", fetchMock);
 
@@ -125,6 +125,6 @@ describe("llmExtract", () => {
     if (!result.ok) {
       return;
     }
-    expect(result.value).toEqual({});
+    expect(result.value).toEqual({ n: 0 });
   });
 });
diff --git a/packages/workflow-utils/src/__tests__/schema-defaults.test.ts b/packages/workflow-utils/src/__tests__/schema-defaults.test.ts
new file mode 100644
index 0000000..a045571
--- /dev/null
+++ b/packages/workflow-utils/src/__tests__/schema-defaults.test.ts
@@ -0,0 +1,59 @@
+import { describe, expect, it } from "vitest";
+import { z } from "zod";
+
+import { schemaDefaults } from "../schema-defaults.js";
+
+describe("schemaDefaults", () => {
+  it("fills nested objects with primitive placeholders", () => {
+    const schema = z.object({
+      meta: z.object({
+        id: z.string(),
+        count: z.number(),
+        flag: z.boolean(),
+      }),
+    });
+    expect(schemaDefaults(schema)).toEqual({
+      meta: { id: "", count: 0, flag: false },
+    });
+  });
+
+  it("uses empty arrays for array fields", () => {
+    const schema = z.object({
+      roles: z.array(z.object({ name: z.string(), level: z.number() })),
+    });
+    const out = schemaDefaults(schema) as { roles: { name: string; level: number }[] };
+    expect(out.roles).toEqual([]);
+    expect(out.roles.map((r) => r.name)).toEqual([]);
+  });
+
+  it("uses the first enum value", () => {
+    const schema = z.object({
+      status: z.enum(["pending", "done", "failed"]),
+      code: z.nativeEnum({ A: 1, B: 2 }),
+    });
+    expect(schemaDefaults(schema)).toEqual({
+      status: "pending",
+      code: 1,
+    });
+  });
+
+  it("sets optional fields to undefined and omits exactOptional keys", () => {
+    const schema = z.object({
+      req: z.string(),
+      maybe: z.string().optional(),
+      exact: z.string().exactOptional(),
+    });
+    expect(schemaDefaults(schema)).toEqual({
+      req: "",
+      maybe: undefined,
+    });
+    expect(Object.keys(schemaDefaults(schema) as object).includes("exact")).toBe(false);
+  });
+
+  it("respects .default()", () => {
+    const schema = z.object({
+      n: z.number().default(42),
+    });
+    expect(schemaDefaults(schema)).toEqual({ n: 42 });
+  });
+});
diff --git a/packages/workflow-utils/src/index.ts b/packages/workflow-utils/src/index.ts
index 513c627..1cbf361 100644
--- a/packages/workflow-utils/src/index.ts
+++ b/packages/workflow-utils/src/index.ts
@@ -11,6 +11,7 @@ export {
   type LlmExtractOptions,
   type LlmProvider,
 } from "./llm-extract.js";
+export { schemaDefaults } from "./schema-defaults.js";
 export {
   nerveCommandEnv,
   spawnSafe,
diff --git a/packages/workflow-utils/src/llm-extract.ts b/packages/workflow-utils/src/llm-extract.ts
index ab78e66..9be735f 100644
--- a/packages/workflow-utils/src/llm-extract.ts
+++ b/packages/workflow-utils/src/llm-extract.ts
@@ -1,6 +1,8 @@
 import { type Result, err, ok } from "@uncaged/nerve-core";
 import { toJSONSchema, type z } from "zod";
 
+import { schemaDefaults } from "./schema-defaults.js";
+
 export type LlmProvider = {
   baseUrl: string;
   apiKey: string;
@@ -102,7 +104,7 @@ export async function llmExtract<T>(
 ): Promise<Result<T, LlmError>> {
   const dryRun = resolveLlmExtractDryRun(options);
   if (dryRun) {
-    return ok({} as T);
+    return ok(schemaDefaults(options.schema) as T);
   }
 
   const rawJsonSchema = toJSONSchema(options.schema) as Record<string, unknown>;
diff --git a/packages/workflow-utils/src/schema-defaults.ts b/packages/workflow-utils/src/schema-defaults.ts
new file mode 100644
index 0000000..384b3ea
--- /dev/null
+++ b/packages/workflow-utils/src/schema-defaults.ts
@@ -0,0 +1,190 @@
+import type { z } from "zod";
+
+type ZodTypeAny = z.ZodType;
+
+type Def = Record<string, unknown> & { type: string };
+type TypeHandler = (schema: ZodTypeAny, def: Def) => unknown;
+
+function isPlainObject(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function isZodExactOptional(s: ZodTypeAny): boolean {
+  return s.constructor.name === "ZodExactOptional";
+}
+
+function resolveDefaultValue(defaultValue: unknown | (() => unknown)): unknown {
+  if (typeof defaultValue === "function") {
+    return (defaultValue as () => unknown)();
+  }
+  return defaultValue;
+}
+
+function mergeIntersection(left: unknown, right: unknown): unknown {
+  if (isPlainObject(left) && isPlainObject(right)) {
+    return { ...left, ...right };
+  }
+  return right;
+}
+
+function defaultsForObject(_schema: ZodTypeAny, def: Def): unknown {
+  const shape = def.shape as Record<string, ZodTypeAny> | undefined;
+  if (shape === undefined) {
+    return {};
+  }
+  const out: Record<string, unknown> = {};
+  for (const key of Object.keys(shape)) {
+    const child = shape[key];
+    const cdef = child.def as { type: string };
+    if (cdef.type === "optional") {
+      if (isZodExactOptional(child)) {
+        continue;
+      }
+      out[key] = undefined;
+    } else {
+      out[key] = schemaDefaultsInner(child);
+    }
+  }
+  return out;
+}
+
+function firstUnionOption(_schema: ZodTypeAny, def: Def): unknown {
+  const options = def.options as readonly ZodTypeAny[] | undefined;
+  if (options === undefined || options.length === 0) {
+    return null;
+  }
+  return schemaDefaultsInner(options[0]);
+}
+
+function defaultsFromNullable(_schema: ZodTypeAny, _def: Def): unknown {
+  return null;
+}
+
+function defaultsFromInner(_schema: ZodTypeAny, def: Def): unknown {
+  const inner = def.innerType as ZodTypeAny | undefined;
+  if (inner === undefined) {
+    return null;
+  }
+  return schemaDefaultsInner(inner);
+}
+
+function defaultsForPipe(_schema: ZodTypeAny, def: Def): unknown {
+  const out = def.out as ZodTypeAny | undefined;
+  if (out === undefined) {
+    return null;
+  }
+  return schemaDefaultsInner(out);
+}
+
+function defaultsForIntersection(_schema: ZodTypeAny, def: Def): unknown {
+  const left = def.left as ZodTypeAny | undefined;
+  const right = def.right as ZodTypeAny | undefined;
+  if (left === undefined || right === undefined) {
+    return null;
+  }
+  return mergeIntersection(schemaDefaultsInner(left), schemaDefaultsInner(right));
+}
+
+function defaultsForTuple(_schema: ZodTypeAny, def: Def): unknown {
+  const items = def.items as readonly ZodTypeAny[] | undefined;
+  if (items === undefined) {
+    return [];
+  }
+  return items.map((item) => schemaDefaultsInner(item));
+}
+
+function defaultsForLazy(schema: ZodTypeAny, def: Def): unknown {
+  const inner =
+    (schema as { _zod?: { innerType?: ZodTypeAny } })._zod?.innerType ??
+    (def.getter as (() => ZodTypeAny) | undefined)?.();
+  if (inner === undefined) {
+    return null;
+  }
+  return schemaDefaultsInner(inner);
+}
+
+function defaultsForPromise(_schema: ZodTypeAny, def: Def): unknown {
+  const inner = def.innerType as ZodTypeAny | undefined;
+  if (inner === undefined) {
+    return Promise.resolve(null);
+  }
+  return Promise.resolve(schemaDefaultsInner(inner));
+}
+
+function firstEnumValue(_schema: ZodTypeAny, def: Def): unknown {
+  const entries = def.entries as Record<string, string | number> | undefined;
+  if (entries === undefined) {
+    return null;
+  }
+  const values = Object.values(entries);
+  return values[0] ?? null;
+}
+
+function firstLiteralValue(_schema: ZodTypeAny, def: Def): unknown {
+  const values = def.values as unknown[] | undefined;
+  if (values === undefined || values.length === 0) {
+    return null;
+  }
+  return values[0];
+}
+
+const TYPE_HANDLERS: Record<string, TypeHandler> = {
+  string: () => "",
+  number: () => 0,
+  boolean: () => false,
+  bigint: () => 0n,
+  date: () => new Date(0),
+  symbol: () => Symbol(),
+  undefined: () => undefined,
+  null: () => null,
+  void: () => undefined,
+  any: () => null,
+  unknown: () => null,
+  never: () => undefined,
+  nan: () => Number.NaN,
+  array: () => [],
+  object: defaultsForObject,
+  record: () => ({}),
+  map: () => new Map(),
+  set: () => new Set(),
+  enum: firstEnumValue,
+  literal: firstLiteralValue,
+  optional: () => undefined,
+  nullable: defaultsFromNullable,
+  default: (_s, def) => resolveDefaultValue(def.defaultValue as unknown | (() => unknown)),
+  prefault: (_s, def) => resolveDefaultValue(def.defaultValue as unknown | (() => unknown)),
+  nonoptional: defaultsFromInner,
+  catch: defaultsFromInner,
+  success: () => false,
+  readonly: defaultsFromInner,
+  union: firstUnionOption,
+  xor: firstUnionOption,
+  intersection: defaultsForIntersection,
+  pipe: defaultsForPipe,
+  transform: () => null,
+  tuple: defaultsForTuple,
+  lazy: defaultsForLazy,
+  promise: defaultsForPromise,
+  file: () => new File([], ""),
+  function: () => null,
+  custom: () => null,
+  template_literal: () => "",
+};
+
+/**
+ * Produces a structurally valid placeholder that mirrors primitive/array/object
+ * shape for a Zod schema. Used for `llmExtract` dry runs so downstream code
+ * (e.g. `.roles.map`) does not throw on `undefined` fields.
+ */
+export function schemaDefaults(schema: z.ZodType): unknown {
+  return schemaDefaultsInner(schema as ZodTypeAny);
+}
+
+function schemaDefaultsInner(schema: ZodTypeAny): unknown {
+  const def = schema.def as Def;
+  const run = TYPE_HANDLERS[def.type];
+  if (run === undefined) {
+    return null;
+  }
+  return run(schema, def);
+}