Summary

When a deep link targeting a channel tab includes subEntityId in the context parameter, the tab receives context.page.subPageId correctly only if the link is clicked from a different chat/channel. If the same deep link is clicked from within the target channel's own conversation, subPageId is undefined on both desktop and web clients. Mobile (iOS/Android) works correctly in all cases.

Environment

• @microsoft/teams-js: 2.53.0
• Teams clients tested: Desktop (new Teams), Web (teams.microsoft.com)
• Mobile: iOS Teams app
• Tab type: Channel (configurable) tab
• Manifest version: 1.17+

Deep link format

https://teams.microsoft.com/l/entity/<appId>/<entityId>?webUrl=<url>&label=<label>&context=<encoded-context>&groupId=<groupId>&tenantId=<tenantId>

Where context is:

{
  "subEntityId": "some-value",
  "canvasUrl": "https://example.com/teams/page?param=value",
  "channelId": "19:xxxxx@thread.tacv2"
}

Reproduction steps

1. Pin a configurable tab to channel A.
2. In the tab code, read subPageId on load:

   const ctx = await app.getContext();
   console.log('subPageId:', ctx.page.subPageId);
   

3. Post the deep link (with subEntityId in context) as a message in channel A's conversation.
4. Also post the same deep link in a different chat (e.g., a 1:1 chat or another channel).
5. Click the link from the different chat → ✅ subPageId is populated.
6. Click the link from channel A's own conversation → ❌ subPageId is undefined.
7. Click the link from channel A's conversation on mobile → ✅ subPageId is populated.

Expected behavior

context.page.subPageId should contain the subEntityId value from the deep link regardless of where the link is clicked from.

Actual behavior