diff --git a/extensions/whatsapp/src/inbound.media.test.ts b/extensions/whatsapp/src/inbound.media.test.ts
index 54cb537ac4a..392551e9703 100644
--- a/extensions/whatsapp/src/inbound.media.test.ts
+++ b/extensions/whatsapp/src/inbound.media.test.ts
@@ -100,6 +100,7 @@ vi.mock("./session.js", async () => {
     sendPresenceUpdate: vi.fn().mockResolvedValue(undefined),
     sendMessage: vi.fn().mockResolvedValue(undefined),
     readMessages: vi.fn().mockResolvedValue(undefined),
+    groupFetchAllParticipating: vi.fn().mockResolvedValue({}),
     updateMediaMessage: vi.fn(),
     logger: {},
     user: { id: "me@s.whatsapp.net" },
diff --git a/extensions/whatsapp/src/inbound/monitor.ts b/extensions/whatsapp/src/inbound/monitor.ts
index f30eb0efe88..c539fd5c6c6 100644
--- a/extensions/whatsapp/src/inbound/monitor.ts
+++ b/extensions/whatsapp/src/inbound/monitor.ts
@@ -531,6 +531,20 @@ export async function monitorWebInbox(options: {
     handleConnectionUpdate as unknown as (...args: unknown[]) => void,
   );
 
+  void (async () => {
+    try {
+      const groups = await sock.groupFetchAllParticipating();
+      if (shouldLogVerbose()) {
+        logVerbose(`Hydrated ${Object.keys(groups ?? {}).length} participating groups on connect`);
+      }
+    } catch (err) {
+      const error = String(err);
+      inboundLogger.warn({ error }, "failed hydrating participating groups on connect");
+      inboundConsoleLog.warn(`Failed hydrating participating groups on connect: ${error}`);
+      logVerbose(`Failed to hydrate participating groups on connect: ${error}`);
+    }
+  })();
+
   const sendApi = createWebSendApi({
     sock: {
       sendMessage: (jid: string, content: AnyMessageContent) => sendTrackedMessage(jid, content),
diff --git a/extensions/whatsapp/src/monitor-inbox.streams-inbound-messages.test.ts b/extensions/whatsapp/src/monitor-inbox.streams-inbound-messages.test.ts
index 60ecc2feb62..63b9f8c81f5 100644
--- a/extensions/whatsapp/src/monitor-inbox.streams-inbound-messages.test.ts
+++ b/extensions/whatsapp/src/monitor-inbox.streams-inbound-messages.test.ts
@@ -6,6 +6,7 @@ import {
   InboxOnMessage,
   buildNotifyMessageUpsert,
   getAuthDir,
+  getSock,
   installWebMonitorInboxUnitTestHooks,
   startInboxMonitor,
   waitForMessageCalls,
@@ -126,6 +127,54 @@ describe("web monitor inbox", () => {
     await listener.close();
   });
 
+  it("hydrates participating groups once after connect", async () => {
+    const { listener, sock } = await startInboxMonitor(vi.fn(async () => {}) as InboxOnMessage);
+
+    expect(sock.groupFetchAllParticipating).toHaveBeenCalledTimes(1);
+
+    await listener.close();
+  });
+
+  it("continues when group hydration fails on connect", async () => {
+    const sock = getSock();
+    sock.groupFetchAllParticipating.mockRejectedValueOnce(new Error("no groups"));
+
+    const { listener } = await startInboxMonitor(vi.fn(async () => {}) as InboxOnMessage);
+
+    expect(sock.groupFetchAllParticipating).toHaveBeenCalledTimes(1);
+    expect(sock.sendPresenceUpdate).toHaveBeenCalledWith("available");
+
+    await listener.close();
+  });
+
+  it("does not block inbound listeners while group hydration is pending", async () => {
+    let resolveHydration!: () => void;
+    const sock = getSock();
+    const pendingHydration = new Promise<Record<string, never>>((resolve) => {
+      resolveHydration = () => resolve({});
+    });
+    sock.groupFetchAllParticipating.mockImplementationOnce(() => pendingHydration);
+    const onMessage = vi.fn(async () => {
+      return;
+    });
+
+    const { listener } = await startInboxMonitor(onMessage as InboxOnMessage);
+    sock.ev.emit(
+      "messages.upsert",
+      buildNotifyMessageUpsert({
+        id: nextMessageId("pending-hydration"),
+        remoteJid: "999@s.whatsapp.net",
+        text: "ping",
+        timestamp: 1_700_000_000,
+        pushName: "Tester",
+      }),
+    );
+    await waitForMessageCalls(onMessage, 1);
+
+    resolveHydration();
+    await listener.close();
+  });
+
   it("deduplicates redelivered messages by id", async () => {
     const onMessage = vi.fn(async () => {
       return;
diff --git a/extensions/whatsapp/src/monitor-inbox.test-harness.ts b/extensions/whatsapp/src/monitor-inbox.test-harness.ts
index e53e69aa2f3..831d6be5fb8 100644
--- a/extensions/whatsapp/src/monitor-inbox.test-harness.ts
+++ b/extensions/whatsapp/src/monitor-inbox.test-harness.ts
@@ -39,6 +39,7 @@ export type MockSock = {
   sendPresenceUpdate: AnyMockFn;
   sendMessage: AnyMockFn;
   readMessages: AnyMockFn;
+  groupFetchAllParticipating: AnyMockFn;
   updateMediaMessage: AnyMockFn;
   logger: Record<string, unknown>;
   signalRepository: {
@@ -65,6 +66,7 @@ function createMockSock(): MockSock {
     sendPresenceUpdate: createResolvedMock(),
     sendMessage: createResolvedMock(),
     readMessages: createResolvedMock(),
+    groupFetchAllParticipating: vi.fn().mockResolvedValue({}),
     updateMediaMessage: vi.fn(),
     logger: {},
     signalRepository: {
diff --git a/test/mocks/baileys.ts b/test/mocks/baileys.ts
index e88dfbcb261..85e7b45b06e 100644
--- a/test/mocks/baileys.ts
+++ b/test/mocks/baileys.ts
@@ -21,6 +21,7 @@ export type MockBaileysSocket = {
   sendPresenceUpdate: ReturnType<typeof vi.fn>;
   sendMessage: ReturnType<typeof vi.fn>;
   readMessages: ReturnType<typeof vi.fn>;
+  groupFetchAllParticipating: ReturnType<typeof vi.fn>;
   user?: { id?: string };
 };
 
@@ -138,6 +139,7 @@ export function createMockBaileys(): {
       sendPresenceUpdate: vi.fn().mockResolvedValue(undefined),
       sendMessage: vi.fn().mockResolvedValue({ key: { id: "msg123" } }),
       readMessages: vi.fn().mockResolvedValue(undefined),
+      groupFetchAllParticipating: vi.fn().mockResolvedValue({}),
       user: { id: "123@s.whatsapp.net" },
     };
     setImmediate(() => ev.emit("connection.update", { connection: "open" }));