diff --git a/apps/api/src/services/proposalService.js b/apps/api/src/services/proposalService.js
index 86b9e68003..5d5b229a08 100644
--- a/apps/api/src/services/proposalService.js
+++ b/apps/api/src/services/proposalService.js
@@ -5,7 +5,7 @@ export async function listProposals() {
 }
 
 export async function createProposal(payload) {
-  const proposal = { id: `prp_${Date.now()}`, ...payload };
+  const proposal = { id: `prp_${Date.now()}`, ...payload, createdAt: new Date().toISOString() };
   proposals.push(proposal);
   return proposal;
 }
diff --git a/apps/api/src/tests/proposalService.test.js b/apps/api/src/tests/proposalService.test.js
new file mode 100644
index 0000000000..3d0815a150
--- /dev/null
+++ b/apps/api/src/tests/proposalService.test.js
@@ -0,0 +1,15 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { createProposal } from "../services/proposalService.js";
+
+test("createProposal adds a server-side createdAt timestamp", async () => {
+  const proposal = await createProposal({
+    coverLetter: "I can deliver this project.",
+    bidAmount: 300,
+    estDuration: "1 week",
+    createdAt: "2000-01-01T00:00:00.000Z"
+  });
+
+  assert.match(proposal.createdAt, /^\d{4}-\d{2}-\d{2}T/);
+  assert.notEqual(proposal.createdAt, "2000-01-01T00:00:00.000Z");
+});