diff --git a/src/types/templates.ts b/src/types/templates.ts
index c76f5d6..0713b2a 100644
--- a/src/types/templates.ts
+++ b/src/types/templates.ts
@@ -42,92 +42,90 @@ const BaseTemplateSchema = z.object({
   updatedAt: UnixTimestampSchema.optional().describe("Date last updated"),
 });
 
-export const EmailTemplateSchema = BaseTemplateSchema.extend({
+const campaignDataFieldsSchema = z
+  .record(z.string(), z.any())
+  .optional()
+  .describe(
+    "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
+  );
+
+// Content fields for each template type, shared between response and param schemas
+const EmailContentFields = {
+  subject: z.string().optional().describe("Subject"),
+  preheaderText: z.string().optional().describe("Preheader text"),
+  fromName: z.string().optional().describe("From name"),
+  fromEmail: z
+    .string()
+    .optional()
+    .describe("From email (must be an authorized sender)"),
+  replyToEmail: z.string().optional().describe("Reply to email"),
+  ccEmails: z.array(z.string()).optional().describe("CC emails"),
   bccEmails: z.array(z.string()).optional().describe("BCC emails"),
+  html: z.string().optional().describe("HTML contents"),
+  plainText: z.string().optional().describe("Plain text contents"),
   cacheDataFeed: z
     .boolean()
     .optional()
     .describe("Cache data feed lookups for 1 hour"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
+  dataFeedIds: z
+    .array(z.number())
     .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
-  ccEmails: z.array(z.string()).optional().describe("CC emails"),
+    .describe("Ids for data feeds used in template rendering"),
   dataFeedId: z
     .number()
     .optional()
     .describe(
-      "[Deprecated - use dataFeedIds instead] Id for data feed used in template rendering"
+      "[Deprecated - use dataFeedIds instead] ID for data feed used in template rendering"
     ),
-  dataFeedIds: z
-    .array(z.number())
-    .optional()
-    .describe("Ids for data feeds used in template rendering"),
-  fromEmail: z
-    .string()
+  mergeDataFeedContext: z
+    .boolean()
     .optional()
-    .describe("From email (must be an authorized sender)"),
-  fromName: z.string().optional().describe("From name"),
+    .describe(
+      "Merge data feed contents into user context, so fields can be referenced by {{field}} instead of [[field]]"
+    ),
   googleAnalyticsCampaignName: z
     .string()
     .optional()
     .describe("Google analytics utm_campaign value"),
-  html: z.string().optional().describe("HTML contents"),
   linkParams: z
     .array(z.any())
     .optional()
     .describe("Parameters to append to each URL in html contents"),
-  mergeDataFeedContext: z
-    .boolean()
-    .optional()
-    .describe(
-      "Merge data feed contents into user context, so fields be referenced by {{field}} instead of [[field]]"
-    ),
-  metadata: z.any().optional().describe("Metadata"),
-  plainText: z.string().optional().describe("Plain text contents"),
-  preheaderText: z.string().optional().describe("Preheader text"),
-  replyToEmail: z.string().optional().describe("Reply to email"),
-  subject: z.string().optional().describe("Subject"),
-});
+  campaignDataFields: campaignDataFieldsSchema,
+};
 
-export const SMSTemplateSchema = BaseTemplateSchema.extend({
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
+const SMSContentFields = {
+  message: z.string().optional().describe("SMS message"),
+  imageUrl: z.string().optional().describe("Image URL"),
   googleAnalyticsCampaignName: z
     .string()
     .optional()
     .describe("Google analytics utm_campaign value"),
-  imageUrl: z.string().optional().describe("Image Url"),
   linkParams: z
     .array(z.any())
     .optional()
     .describe("Parameters to append to each URL in contents"),
-  message: z.string().optional().describe("SMS message"),
   trackingDomain: z.string().optional().describe("Tracking Domain"),
-});
+  campaignDataFields: campaignDataFieldsSchema,
+};
 
-export const PushTemplateSchema = BaseTemplateSchema.extend({
+const PushContentFields = {
+  message: z.string().optional().describe("Push message"),
+  title: z.string().optional().describe("Push message title"),
   badge: z.string().optional().describe("Badge to set for push notification"),
   buttons: z
     .array(z.any())
     .optional()
     .describe("Array of buttons that appear to respond to the push. Max of 3"),
+  sound: z.string().optional().describe("Sound"),
+  payload: z
+    .record(z.string(), z.any())
+    .optional()
+    .describe("Payload to send with push notification"),
   cacheDataFeed: z
     .boolean()
     .optional()
     .describe("Cache data feed lookups for 1 hour"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
   dataFeedIds: z
     .array(z.number())
     .optional()
@@ -139,7 +137,7 @@ export const PushTemplateSchema = BaseTemplateSchema.extend({
       "Deep Link. A mapping that accepts two optional properties: 'ios' & 'android' and their respective deep link values"
     ),
   interruptionLevel: z
-    .string()
+    .enum(["passive", "active", "time-sensitive", "critical"])
     .optional()
     .describe(
       "An interruption level helps iOS determine when to alert a user about the arrival of a push notification"
@@ -154,11 +152,6 @@ export const PushTemplateSchema = BaseTemplateSchema.extend({
     .describe(
       "Merge data feed contents into user context, so fields can be referenced by {{field}} instead of [[field]]"
     ),
-  message: z.string().optional().describe("Push message"),
-  payload: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe("Payload to send with push notification"),
   relevanceScore: z
     .number()
     .optional()
@@ -171,23 +164,17 @@ export const PushTemplateSchema = BaseTemplateSchema.extend({
     .describe(
       "Rich Media URL. A mapping that accepts two optional properties: 'ios' & 'android' and their respective rich media url values"
     ),
-  sound: z.string().optional().describe("Sound"),
-  title: z.string().optional().describe("Push message title"),
   wake: z
     .boolean()
     .optional()
     .describe(
       "Set the content-available flag on iOS notifications, which will wake the app in the background"
     ),
-});
+  campaignDataFields: campaignDataFieldsSchema,
+};
 
-export const InAppTemplateSchema = BaseTemplateSchema.extend({
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
+const InAppContentFields = {
+  html: z.string().optional().describe("Html of the in-app notification"),
   expirationDateTime: z
     .string()
     .optional()
@@ -200,7 +187,6 @@ export const InAppTemplateSchema = BaseTemplateSchema.extend({
     .describe(
       "The in-app message's expiration time, relative to its send time. Should be an expression such as now+90d"
     ),
-  html: z.string().optional().describe("Html of the in-app notification"),
   inAppDisplaySettings: z
     .record(z.string(), z.any())
     .optional()
@@ -214,8 +200,21 @@ export const InAppTemplateSchema = BaseTemplateSchema.extend({
     .record(z.string(), z.any())
     .optional()
     .describe("Web In-app Display settings"),
+  campaignDataFields: campaignDataFieldsSchema,
+};
+
+export const EmailTemplateSchema = BaseTemplateSchema.extend({
+  ...EmailContentFields,
+  metadata: z.any().optional().describe("Metadata"),
 });
 
+export const SMSTemplateSchema = BaseTemplateSchema.extend(SMSContentFields);
+
+export const PushTemplateSchema = BaseTemplateSchema.extend(PushContentFields);
+
+export const InAppTemplateSchema =
+  BaseTemplateSchema.extend(InAppContentFields);
+
 export type EmailTemplate = z.infer<typeof EmailTemplateSchema>;
 export type SMSTemplate = z.infer<typeof SMSTemplateSchema>;
 export type PushTemplate = z.infer<typeof PushTemplateSchema>;
@@ -348,6 +347,12 @@ export type GetTemplateByClientIdResponse = z.infer<
 const BaseTemplateParamsSchema = z.object({
   name: z.string().optional().describe("Template name"),
   locale: z.string().optional().describe("Template locale"),
+  isDefaultLocale: z
+    .boolean()
+    .optional()
+    .describe(
+      "Sets the locale associated with the request content as the template's default"
+    ),
   messageTypeId: z.number().optional().describe("Message type ID"),
   creatorUserId: z.string().optional().describe("Creator user ID"),
   campaignId: z.number().optional().describe("Associated campaign ID"),
@@ -363,58 +368,6 @@ const UpdateTemplateParamsSchema = BaseTemplateParamsSchema.extend({
   templateId: z.number().describe("Template ID to update"),
 });
 
-// Content field objects for each template type
-const EmailContentFields = {
-  subject: z.string().optional().describe("Email subject"),
-  fromName: z.string().optional().describe("From name"),
-  fromEmail: z.email().optional().describe("From email"),
-  html: z.string().optional().describe("HTML content"),
-  plainText: z.string().optional().describe("Plain text content"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
-};
-
-const SMSContentFields = {
-  message: z.string().optional().describe("SMS message content"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
-};
-
-const PushContentFields = {
-  message: z.string().optional().describe("Push notification message"),
-  title: z.string().optional().describe("Push notification title"),
-  badge: z.number().optional().describe("Badge count"),
-  sound: z.string().optional().describe("Sound file"),
-  payload: z.record(z.string(), z.any()).optional().describe("Custom payload"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
-};
-
-const InAppContentFields = {
-  html: z
-    .string()
-    .optional()
-    .describe("HTML content of the in-app notification"),
-  campaignDataFields: z
-    .record(z.string(), z.any())
-    .optional()
-    .describe(
-      "Campaign-level data fields available as {{field}} merge parameters during message rendering. These fields are overridden by user and event data fields of the same name."
-    ),
-};
-
 // Email template upsert (create or update by clientTemplateId)
 export const UpsertEmailTemplateParamsSchema =
   UpsertTemplateParamsSchema.extend(EmailContentFields);
diff --git a/tests/integration/templates.test.ts b/tests/integration/templates.test.ts
index 80c87ff..9593b75 100644
--- a/tests/integration/templates.test.ts
+++ b/tests/integration/templates.test.ts
@@ -33,6 +33,7 @@ describe("Template Management Integration Tests", () => {
       name: uniqueId("Test-Email-Template"),
       clientTemplateId: uniqueId("test-email-template"),
       subject: "Integration Test Email",
+      preheaderText: "Integration test preheader",
       fromName: "Alex Newman",
       fromEmail: "alex.newman@iterable.com",
       html: "<html><body><h1>Test Email</h1><p>Hello {{firstName}}!</p><p><a href='{{unsubscribeUrl}}'>Unsubscribe</a></p></body></html>",
@@ -200,7 +201,14 @@ describe("Template Management Integration Tests", () => {
         templateId,
         name: `${originalData.name} (Updated)`,
         subject: `${originalData.subject} (Updated)`,
+        preheaderText: "Updated preheader",
       }),
+      verifyGet: (template: any, originalData: any) => {
+        expect(template.preheaderText).toBe(originalData.preheaderText);
+      },
+      verifyUpdate: (template: any) => {
+        expect(template.preheaderText).toBe("Updated preheader");
+      },
       proofData: (templateId: number, recipientEmail: string) => ({
         templateId,
         recipientEmail,
@@ -260,7 +268,15 @@ describe("Template Management Integration Tests", () => {
         createData,
         updateData,
         proofData,
+        ...rest
       }) => {
+        const verifyGet = (rest as any).verifyGet as
+          | ((template: any, originalData: any) => void)
+          | undefined;
+        const verifyUpdate = (rest as any).verifyUpdate as
+          | ((template: any) => void)
+          | undefined;
+
         describe(`${type} Templates`, () => {
           it(`should create, get, update, and delete ${type.toLowerCase()} template`, async () => {
             const templateData = createData();
@@ -274,6 +290,7 @@ describe("Template Management Integration Tests", () => {
 
               const getResponse = await waitForTemplate(templateId, getMethod);
               expect(getResponse.templateId).toBe(templateId);
+              verifyGet?.(getResponse, templateData);
 
               const updateParams = updateData(templateId, templateData);
               await withTimeout((client as any)[updateMethod](updateParams));
@@ -283,6 +300,7 @@ describe("Template Management Integration Tests", () => {
                 getMethod
               );
               expect(updatedTemplate.name).toBe(updateParams.name);
+              verifyUpdate?.(updatedTemplate);
 
               const deleteResponse = await withTimeout(
                 client.deleteTemplates({ ids: [templateId] })
diff --git a/tests/unit/templates.test.ts b/tests/unit/templates.test.ts
index cc3e163..fd7a8e5 100644
--- a/tests/unit/templates.test.ts
+++ b/tests/unit/templates.test.ts
@@ -16,7 +16,13 @@ import {
   SendTemplateProofParamsSchema,
   SMSTemplateSchema,
   UpdateEmailTemplateParamsSchema,
+  UpdateInAppTemplateParamsSchema,
+  UpdatePushTemplateParamsSchema,
+  UpdateSMSTemplateParamsSchema,
   UpsertEmailTemplateParamsSchema,
+  UpsertInAppTemplateParamsSchema,
+  UpsertPushTemplateParamsSchema,
+  UpsertSMSTemplateParamsSchema,
 } from "../../src/types/templates.js";
 import { createMockClient, createMockTemplate } from "../utils/test-helpers";
 
@@ -184,19 +190,23 @@ describe("Template Management", () => {
           templateId: 12345,
           name: "Test Email Template",
           subject: "Test Subject",
+          preheaderText: "Preview text here",
           fromName: "Test Sender",
           fromEmail: "test@example.com",
+          replyToEmail: "reply@example.com",
           html: "<html><body>Test</body></html>",
           plainText: "Test",
           createdAt: 1640995200000,
           updatedAt: 1640995200000,
           cacheDataFeed: true,
           mergeDataFeedContext: false,
+          dataFeedId: 42,
+          dataFeedIds: [42, 43],
         };
 
-        expect(() =>
-          EmailTemplateSchema.parse(validEmailTemplate)
-        ).not.toThrow();
+        const result = EmailTemplateSchema.parse(validEmailTemplate);
+        expect(result.preheaderText).toBe("Preview text here");
+        expect(result.dataFeedId).toBe(42);
 
         // Test required fields
         expect(() =>
@@ -430,6 +440,171 @@ describe("Template Management", () => {
     });
   });
 
+  describe("Upsert/Update Param Schema Validation", () => {
+    describe("Email param schemas accept all content fields", () => {
+      const fullEmailParams = {
+        name: "Test Email",
+        subject: "Subject",
+        preheaderText: "Preview text",
+        fromName: "Sender",
+        fromEmail: "sender@example.com",
+        replyToEmail: "reply@example.com",
+        ccEmails: ["cc@example.com"],
+        bccEmails: ["bcc@example.com"],
+        html: "<html><body>Test</body></html>",
+        plainText: "Test",
+        cacheDataFeed: true,
+        dataFeedIds: [1, 2],
+        dataFeedId: 1,
+        mergeDataFeedContext: false,
+        googleAnalyticsCampaignName: "campaign-1",
+        linkParams: [{ key: "utm_source", value: "iterable" }],
+        campaignDataFields: { field1: "value1" },
+        isDefaultLocale: true,
+      };
+
+      it("should accept all email fields on upsert", () => {
+        const result = UpsertEmailTemplateParamsSchema.safeParse({
+          ...fullEmailParams,
+          clientTemplateId: "test-email",
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should accept all email fields on update", () => {
+        const result = UpdateEmailTemplateParamsSchema.safeParse({
+          ...fullEmailParams,
+          templateId: 12345,
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should include preheaderText in parsed output", () => {
+        const result = UpsertEmailTemplateParamsSchema.safeParse({
+          clientTemplateId: "test",
+          preheaderText: "Check out our latest deals!",
+        });
+        expect(result.success).toBe(true);
+        if (result.success) {
+          expect(result.data.preheaderText).toBe(
+            "Check out our latest deals!"
+          );
+        }
+      });
+    });
+
+    describe("SMS param schemas accept all content fields", () => {
+      const fullSMSParams = {
+        name: "Test SMS",
+        message: "Hello!",
+        imageUrl: "https://example.com/image.png",
+        googleAnalyticsCampaignName: "sms-campaign",
+        linkParams: [{ key: "utm_source", value: "iterable" }],
+        trackingDomain: "track.example.com",
+        campaignDataFields: { field1: "value1" },
+        isDefaultLocale: false,
+      };
+
+      it("should accept all SMS fields on upsert", () => {
+        const result = UpsertSMSTemplateParamsSchema.safeParse({
+          ...fullSMSParams,
+          clientTemplateId: "test-sms",
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should accept all SMS fields on update", () => {
+        const result = UpdateSMSTemplateParamsSchema.safeParse({
+          ...fullSMSParams,
+          templateId: 12345,
+        });
+        expect(result.success).toBe(true);
+      });
+    });
+
+    describe("Push param schemas accept all content fields", () => {
+      const fullPushParams = {
+        name: "Test Push",
+        message: "Hello!",
+        title: "Title",
+        badge: "1",
+        buttons: [{ identifier: "btn1", action: "openApp" }],
+        sound: "default",
+        payload: { key: "value" },
+        cacheDataFeed: false,
+        dataFeedIds: [1],
+        deeplink: { ios: "myapp://home", android: "myapp://home" },
+        interruptionLevel: "time-sensitive" as const,
+        isSilentPush: false,
+        mergeDataFeedContext: true,
+        relevanceScore: 0.75,
+        richMedia: { ios: "https://example.com/img.png" },
+        wake: true,
+        campaignDataFields: { field1: "value1" },
+        isDefaultLocale: true,
+      };
+
+      it("should accept all push fields on upsert", () => {
+        const result = UpsertPushTemplateParamsSchema.safeParse({
+          ...fullPushParams,
+          clientTemplateId: "test-push",
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should accept all push fields on update", () => {
+        const result = UpdatePushTemplateParamsSchema.safeParse({
+          ...fullPushParams,
+          templateId: 12345,
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should reject invalid interruptionLevel values", () => {
+        const result = UpsertPushTemplateParamsSchema.safeParse({
+          clientTemplateId: "test",
+          interruptionLevel: "invalid-value",
+        });
+        expect(result.success).toBe(false);
+      });
+    });
+
+    describe("InApp param schemas accept all content fields", () => {
+      const fullInAppParams = {
+        name: "Test InApp",
+        html: "<div>Hello!</div>",
+        expirationDateTime: "2026-12-31 23:59:59",
+        expirationDuration: "now+90d",
+        inAppDisplaySettings: { position: "center" },
+        inboxMetadata: {
+          title: "Inbox Title",
+          subtitle: "Subtitle",
+          icon: "https://example.com/icon.png",
+        },
+        payload: { key: "value" },
+        webInAppDisplaySettings: { position: "top-right" },
+        campaignDataFields: { field1: "value1" },
+        isDefaultLocale: false,
+      };
+
+      it("should accept all in-app fields on upsert", () => {
+        const result = UpsertInAppTemplateParamsSchema.safeParse({
+          ...fullInAppParams,
+          clientTemplateId: "test-inapp",
+        });
+        expect(result.success).toBe(true);
+      });
+
+      it("should accept all in-app fields on update", () => {
+        const result = UpdateInAppTemplateParamsSchema.safeParse({
+          ...fullInAppParams,
+          templateId: 12345,
+        });
+        expect(result.success).toBe(true);
+      });
+    });
+  });
+
   describe("Template Preview", () => {
     describe("previewEmailTemplate", () => {
       it("should preview email template with user data", async () => {