diff --git a/templates/calendar/app/components/calendar/AttendeeAutocomplete.tsx b/templates/calendar/app/components/calendar/AttendeeAutocomplete.tsx
index 649701120..d4b38dd31 100644
--- a/templates/calendar/app/components/calendar/AttendeeAutocomplete.tsx
+++ b/templates/calendar/app/components/calendar/AttendeeAutocomplete.tsx
@@ -23,6 +23,7 @@ import {
 } from "@/components/ui/popover";
 import { Button } from "@/components/ui/button";
 import { cn } from "@/lib/utils";
+import { isMcpEmbedSurface } from "@/lib/mcp-embed";
 
 const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
 
@@ -446,13 +447,17 @@ export const AttendeeAutocomplete = forwardRef<
                   addPerson(person);
                 }}
               >
-                {person.photoUrl ? (
+                {person.photoUrl && !isMcpEmbedSurface() ? (
                   <img
                     src={person.photoUrl}
                     alt=""
                     className="h-8 w-8 shrink-0 rounded-full object-cover"
                   />
                 ) : (
+                  // MCP host iframes (ChatGPT / Claude) block cross-origin
+                  // googleusercontent.com contact avatars at the COEP layer
+                  // and produce console errors. Fall back to initials when
+                  // rendered in an embedded surface.
                   <span className="flex h-8 w-8 shrink-0 items-center justify-center rounded-full bg-muted text-[11px] font-medium text-muted-foreground">
                     {initialsFor(person) || (
                       <IconUserCircle className="h-4 w-4" />
diff --git a/templates/calendar/app/lib/mcp-embed.spec.ts b/templates/calendar/app/lib/mcp-embed.spec.ts
new file mode 100644
index 000000000..b861aba5d
--- /dev/null
+++ b/templates/calendar/app/lib/mcp-embed.spec.ts
@@ -0,0 +1,27 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { isMcpEmbedSurface } from "./mcp-embed";
+
+describe("isMcpEmbedSurface (calendar)", () => {
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it("returns false outside the browser", () => {
+    expect(isMcpEmbedSurface()).toBe(false);
+  });
+
+  it("detects ?embedded=1 query params (MCP iframe surface)", () => {
+    vi.stubGlobal("window", { location: { search: "?embedded=1" } });
+    expect(isMcpEmbedSurface()).toBe(true);
+  });
+
+  it("accepts the truthy 'true' legacy value", () => {
+    vi.stubGlobal("window", { location: { search: "?embedded=true" } });
+    expect(isMcpEmbedSurface()).toBe(true);
+  });
+
+  it("ignores ordinary in-app routes without the embed flag", () => {
+    vi.stubGlobal("window", { location: { search: "?date=2026-05-23" } });
+    expect(isMcpEmbedSurface()).toBe(false);
+  });
+});
diff --git a/templates/calendar/app/lib/mcp-embed.ts b/templates/calendar/app/lib/mcp-embed.ts
new file mode 100644
index 000000000..2f317e7d2
--- /dev/null
+++ b/templates/calendar/app/lib/mcp-embed.ts
@@ -0,0 +1,20 @@
+/**
+ * MCP embed surface detection for Calendar.
+ *
+ * When the Calendar UI is rendered inside an MCP host's iframe (ChatGPT /
+ * Claude.ai render `*.agent-native.com` through their own sandboxed wrapper
+ * with strict COEP/CORP headers), cross-origin third-party images
+ * (`googleusercontent.com` avatars, etc.) get blocked at the browser level
+ * and produce noisy console errors. Templates that ship images that work
+ * fine in their own UI need to gate them on this flag and fall back to
+ * a same-origin placeholder when embedded.
+ *
+ * Mirrors `templates/mail/app/lib/mcp-embed.ts` (added in PR #883). A future
+ * refactor could lift this to `@agent-native/core/client` so every template
+ * uses one helper — for now keep it template-local to match the Mail PR.
+ */
+export function isMcpEmbedSurface(): boolean {
+  if (typeof window === "undefined") return false;
+  const value = new URLSearchParams(window.location.search).get("embedded");
+  return value === "1" || value === "true";
+}
diff --git a/templates/calendar/app/pages/CalendarView.tsx b/templates/calendar/app/pages/CalendarView.tsx
index 0a3c1db4c..f9e7e050d 100644
--- a/templates/calendar/app/pages/CalendarView.tsx
+++ b/templates/calendar/app/pages/CalendarView.tsx
@@ -1,6 +1,7 @@
 import { useState, useMemo, useEffect, useCallback, useRef } from "react";
 import { Link } from "react-router";
 import { cn } from "@/lib/utils";
+import { isMcpEmbedSurface } from "@/lib/mcp-embed";
 import {
   format,
   startOfMonth,
@@ -1492,7 +1493,7 @@ function AccountAvatars() {
                   zIndex: accounts.length - i,
                 }}
               >
-                {account.photoUrl ? (
+                {account.photoUrl && !isMcpEmbedSurface() ? (
                   <img
                     src={account.photoUrl}
                     alt=""
@@ -1500,6 +1501,11 @@ function AccountAvatars() {
                     referrerPolicy="no-referrer"
                   />
                 ) : (
+                  // MCP host iframes (ChatGPT / Claude) ship strict COEP/CORP
+                  // headers that block cross-origin googleusercontent.com
+                  // avatars and produce noisy console errors. Fall back to a
+                  // same-origin initial chip when embedded. See
+                  // `templates/calendar/app/lib/mcp-embed.ts`.
                   <div className="flex h-7 w-7 items-center justify-center rounded-full bg-primary/20 text-[11px] font-semibold text-primary">
                     {account.email[0]?.toUpperCase()}
                   </div>