diff --git a/src/addons/thunderbird/src/background.js b/src/addons/thunderbird/src/background.js
index 4e61284a..97eb301e 100644
--- a/src/addons/thunderbird/src/background.js
+++ b/src/addons/thunderbird/src/background.js
@@ -2,6 +2,30 @@ import { buildMeetingMessage } from "./lib/meeting-message.js";
 
 console.log("[meeting-link] background loaded at", new Date().toISOString());
 
+(async () => {
+  try {
+    console.log("[meeting-link] browser.calendar exists?", !!browser.calendar);
+    if (browser.calendar) {
+      console.log("[meeting-link] calendar namespace keys:",
+        Object.keys(browser.calendar));
+    }
+
+    // Try the most basic read call — list configured calendars.
+    // The exact method name varies between experiment versions; we'll
+    // try the common one first.
+    if (browser.calendar.calendars?.query) {
+      const calendars = await browser.calendar.calendars.query({});
+      console.log("[meeting-link] calendars found:", calendars.length, calendars);
+    } else {
+      console.warn("[meeting-link] calendars.query not present — namespace shape:",
+        browser.calendar);
+    }
+
+  } catch (err) {
+    console.error("[meeting-link] calendar probe failed:", err);
+  }
+})();
+
 // Hardcoded for Spike 1. Spike 2 replaces this with a fetch() to your API.
 const STUB_MEETING_DATA = {
   url: "https://meet.example.com/m/abc-123-xyz",
@@ -21,4 +45,4 @@ browser.runtime.onMessage.addListener(async (msg) => {
       return { ok: false, error: String(err.message || err) };
     }
   }
-});
\ No newline at end of file
+});
diff --git a/src/addons/thunderbird/src/manifest.json b/src/addons/thunderbird/src/manifest.json
index 492da617..0da0f82b 100644
--- a/src/addons/thunderbird/src/manifest.json
+++ b/src/addons/thunderbird/src/manifest.json
@@ -18,5 +18,24 @@
     "default_popup": "popup/popup.html",
     "default_icon": "icons/icon-32.png"
   },
-  "permissions": ["compose"]
-}
\ No newline at end of file
+  "permissions": ["compose"],
+  "experiment_apis": {
+    "calendar_provider": {
+      "schema": "experiments/calendar/schema/calendar-provider.json",
+      "parent": {
+        "scopes": ["addon_parent"],
+        "paths": [["calendar", "provider"]],
+        "script": "experiments/calendar/parent/ext-calendar-provider.js",
+        "events": ["startup"]
+      }
+    },
+    "calendar_calendars": {
+      "schema": "experiments/calendar/schema/calendar-calendars.json",
+      "parent": {
+        "scopes": ["addon_parent"],
+        "paths": [["calendar", "calendars"]],
+        "script": "experiments/calendar/parent/ext-calendar-calendars.js"
+      }
+    }
+  }
+}