diff --git a/.changeset/lazy-terminal-run-data.md b/.changeset/lazy-terminal-run-data.md
new file mode 100644
index 0000000000..17ee9e1daf
--- /dev/null
+++ b/.changeset/lazy-terminal-run-data.md
@@ -0,0 +1,6 @@
+---
+"@workflow/world": patch
+"@workflow/core": patch
+---
+
+Accept lazy completed and failed runs whose payload is represented by a remote reference.
diff --git a/packages/core/src/runtime/run.ts b/packages/core/src/runtime/run.ts
index 02a6459a70..f7488766b5 100644
--- a/packages/core/src/runtime/run.ts
+++ b/packages/core/src/runtime/run.ts
@@ -291,7 +291,12 @@ export class Run<TResult> {
         }
 
         if (run.status === 'failed') {
-          throw new WorkflowRunFailedError(this.runId, run.error);
+          // Terminal run data can be returned lazily, so the error payload
+          // may not be materialized. Fall back to a generic message.
+          throw new WorkflowRunFailedError(
+            this.runId,
+            run.error ?? { message: 'Workflow run failed' }
+          );
         }
 
         throw new WorkflowRunNotCompletedError(this.runId, run.status);
diff --git a/packages/world/src/runs.test.ts b/packages/world/src/runs.test.ts
new file mode 100644
index 0000000000..e4d912808b
--- /dev/null
+++ b/packages/world/src/runs.test.ts
@@ -0,0 +1,27 @@
+import { describe, expect, it } from 'vitest';
+import { z } from 'zod';
+import { WorkflowRunSchema } from './runs.js';
+
+describe('WorkflowRunSchema', () => {
+  it('accepts terminal runs without materialized payloads', () => {
+    const completedSchema = WorkflowRunSchema.options[2];
+    const failedSchema = WorkflowRunSchema.options[3];
+    const run = {
+      runId: 'wrun_1',
+      deploymentId: 'dpl_1',
+      workflowName: 'workflow_1',
+      createdAt: new Date(),
+      updatedAt: new Date(),
+      completedAt: new Date(),
+    };
+
+    expect(completedSchema.shape.output).toBeInstanceOf(z.ZodOptional);
+    expect(failedSchema.shape.error).toBeInstanceOf(z.ZodOptional);
+    expect(
+      WorkflowRunSchema.safeParse({ ...run, status: 'completed' }).success
+    ).toBe(true);
+    expect(
+      WorkflowRunSchema.safeParse({ ...run, status: 'failed' }).success
+    ).toBe(true);
+  });
+});
diff --git a/packages/world/src/runs.ts b/packages/world/src/runs.ts
index 248bbe1176..989c2eb021 100644
--- a/packages/world/src/runs.ts
+++ b/packages/world/src/runs.ts
@@ -99,7 +99,7 @@ export const WorkflowRunSchema = z.discriminatedUnion('status', [
   // Completed state - output can be v1 or v2 format
   WorkflowRunBaseSchema.extend({
     status: z.literal('completed'),
-    output: SerializedDataSchema,
+    output: SerializedDataSchema.optional(),
     error: z.undefined().optional(),
     completedAt: z.coerce.date(),
   }),
@@ -107,7 +107,7 @@ export const WorkflowRunSchema = z.discriminatedUnion('status', [
   WorkflowRunBaseSchema.extend({
     status: z.literal('failed'),
     output: z.undefined().optional(),
-    error: StructuredErrorSchema,
+    error: StructuredErrorSchema.optional(),
     completedAt: z.coerce.date(),
   }),
 ]);