feat(showcase): dynamic-approval demo flow — decision outputs feed the next stage's expression approvers (#3447)

The lead reviewer picks the co-signers in their decision (decisionOutputs);
the co-sign node resolves them at entry from vars.lead_review.next_reviewers.
Browser-dogfooded end to end: dialog renders the declared output field, the
decide body nests outputs, and the co-sign slate resolves to the picked ids.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: os-zhuang

examples/app-showcase/src/automation/flows/dynamic-approval.flow.ts

@@ -0,0 +1,68 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+import { defineFlow } from '@objectstack/spec';
+
+/**
+ * #3447 P2 dogfood: dynamic approver routing end to end.
+ *
+ * Two-stage approval where the FIRST approver picks the second stage's
+ * approvers in their decision (`decisionOutputs`), and the second stage
+ * resolves them at node entry from an `expression` approver over `vars.*` —
+ * no record-field detour. Trigger: retitling an announcement (an otherwise
+ * approval-free object, so this demo never collides with the expense/invoice/
+ * project approval flows — the service dedupes pending requests per record).
+ */
+export const DynamicApprovalFlow = defineFlow({
+  name: 'showcase_dynamic_approval',
+  label: 'Announcement Dynamic Approval',
+  description: 'Lead reviewer picks the co-signers in their decision; the co-sign step resolves them at entry.',
+  type: 'autolaunched',
+  status: 'active',
+  nodes: [
+    {
+      id: 'start',
+      type: 'start',
+      label: 'On Announcement Retitled',
+      config: {
+        objectName: 'showcase_announcement',
+        triggerType: 'record-after-update',
+        condition: 'title != previous.title',
+      },
+    },
+    {
+      id: 'lead_review',
+      type: 'approval',
+      label: 'Lead Review',
+      config: {
+        // The seeded admin holds the org-membership `owner` tier, so the demo
+        // routes stage 1 to them without hard-coding a user id.
+        approvers: [{ type: 'org_membership_level', value: 'owner' }],
+        behavior: 'first_response',
+        lockRecord: true,
+        // The lead hands the co-signers to the flow with their decision.
+        decisionOutputs: ['next_reviewers'],
+      },
+    },
+    {
+      id: 'co_sign',
+      type: 'approval',
+      label: 'Co-sign',
+      config: {
+        // Resolved at node entry from the lead's decision outputs (#3447 P2).
+        approvers: [{ type: 'expression', value: 'vars.lead_review.next_reviewers' }],
+        behavior: 'unanimous',
+        lockRecord: true,
+        onEmptyApprovers: 'fail',
+      },
+    },
+    { id: 'approved', type: 'end', label: 'Approved' },
+    { id: 'rejected', type: 'end', label: 'Rejected' },
+  ],
+  edges: [
+    { id: 'e1', source: 'start', target: 'lead_review' },
+    { id: 'e2', source: 'lead_review', target: 'co_sign', label: 'approve' },
+    { id: 'e3', source: 'lead_review', target: 'rejected', label: 'reject' },
+    { id: 'e4', source: 'co_sign', target: 'approved', label: 'approve' },
+    { id: 'e5', source: 'co_sign', target: 'rejected', label: 'reject' },
+  ],
+});

examples/app-showcase/src/automation/flows/index.ts

@@ -1,6 +1,7 @@
 // Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
 
 import { defineFlow } from '@objectstack/spec';
+import { DynamicApprovalFlow } from './dynamic-approval.flow';
 
 /**
  * Task Completed → Notify — an autolaunched, record-triggered flow that fires
@@ -1620,4 +1621,6 @@ export const allFlows = [
   ResilientSyncFlow,
   ProjectEscalationFlow,
   InboundTaskWebhookFlow,
+  // #3447 P2 dogfood: expression approvers + decision outputs, end to end.
+  DynamicApprovalFlow,
 ];