diff --git a/contracts/README.md b/contracts/README.md
index 42656c32..635501b1 100644
--- a/contracts/README.md
+++ b/contracts/README.md
@@ -80,6 +80,11 @@ decision `experimentRevision`, and closed Platform campaign shapes. SDK types
 follow each change on covered operations; feature evaluation stays excluded. `cloud-api-supplements.json` pins the Graph-compatible
 catalog and Flow encryption routes to the same commit.
 
+API PR #377, merged in this snapshot, rejects invalid project-template
+drafts with 400 before submission. The typed `MessagingClient.templates.submit`
+method makes one network attempt, including when callers supply an idempotency
+key or retry override; the route declares no replay contract.
+
 The merged Campaigns failed-state follow-up updates the `campaign.failed`
 reason example and the public archive/delete `409` descriptions. It changes no
 operation fingerprint or SDK method mapping.
diff --git a/packages/typescript/README.md b/packages/typescript/README.md
index 4fa4366f..7dbc3613 100644
--- a/packages/typescript/README.md
+++ b/packages/typescript/README.md
@@ -315,10 +315,19 @@ const created = await messaging.templates.create("support", {
 await messaging.templates.preview("support", created.data.data.id, {
   values: { name: "Grace" },
 });
+
+await messaging.templates.submit("support", created.data.data.id, {
+  session: "number_123",
+});
 ```
 
 Keep this client on the server. Browser builders use an application-owned
 route, such as `createTemplateBuilderRoute` from `@polymorfa/nextjs`.
+Submission validates the saved definition before making one provider attempt.
+A successful response records the submission; it does not establish approval.
+If the request times out or loses its response, read the Number's template
+catalog before deciding whether another submission is needed. Local preview
+does not ask Meta to validate the template.
 
 ## Flow drafts and provider lifecycle
 
diff --git a/packages/typescript/src/messaging/templates.ts b/packages/typescript/src/messaging/templates.ts
index 3cec7d87..ab317f69 100644
--- a/packages/typescript/src/messaging/templates.ts
+++ b/packages/typescript/src/messaging/templates.ts
@@ -90,6 +90,7 @@ export class TemplatesResource {
     });
   }
 
+  /** Submit once. If the response is lost, read the Number's template catalog before another attempt. */
   submit(
     projectSlug: string,
     templateId: string,
@@ -101,6 +102,7 @@ export class TemplatesResource {
       path: `${templatePath(projectSlug, templateId)}/submit`,
       body,
       ...options,
+      maxNetworkRetries: 0,
     });
   }
 }
diff --git a/packages/typescript/test/cloud-templates.test.ts b/packages/typescript/test/cloud-templates.test.ts
index 951051a2..3d768cd8 100644
--- a/packages/typescript/test/cloud-templates.test.ts
+++ b/packages/typescript/test/cloud-templates.test.ts
@@ -163,6 +163,29 @@ describe("Cloud templates", () => {
     },
   );
 
+  it("submits a project template draft to Meta once, even with a retry override", async () => {
+    const server = await startTestServer(() => ({
+      status: 500,
+      body: JSON.stringify({
+        error: { code: "internal_error", message: "Outcome unknown" },
+      }),
+    }));
+    servers.push(server);
+    await expect(
+      client(server).templates.submit(
+        "support",
+        "tpl/1",
+        { session: "number_123" },
+        { idempotencyKey: "customer-key", maxNetworkRetries: 3 },
+      ),
+    ).rejects.toMatchObject({ status: 500 });
+    expect(server.requests).toHaveLength(1);
+    expect(server.requests[0]!.method).toBe("POST");
+    expect(server.requests[0]!.path).toBe(
+      "/messaging/projects/support/templates/tpl%2F1/submit",
+    );
+  });
+
   it("returns a catalog failure instead of an empty successful list", async () => {
     const server = await startTestServer(() => ({
       status: 502,