docs(groups): explain reading other bots' messages via admin and bot-to-bot mode

docs/aliases.md

@@ -177,20 +177,20 @@ so they stay valid. They are sent back as entities rather than re-rendered as
 markup, which avoids escaping and re-parsing content the user never wrote as
 markup.
 
-**Another bot's message cannot be saved.** Telegram's own rule: *"Bots will not
-be able to see messages from other bots regardless of mode."* The reply arrives
-with its content stripped, so there is nothing to store and no setting that
-would change it.
+**Another bot's message needs group setup.** By default Telegram strips another
+bot's message out of a reply, so there is nothing to store. It arrives intact
+once the bot has Bot-to-Bot Communication Mode enabled and is a group admin; see
+[Group setup](deploy-coolify-selfhosted.md#4-group-setup).
 
 Every refusal for a message that could not be *read* — as opposed to one whose
-kind is unsupported — ends with the same advice, because it is the only thing
-that works: **forward it into the chat and reply to your copy.** A forwarded
+kind is unsupported — ends with the same advice, because it works without any
+setup: **forward it into the chat and reply to your copy.** A forwarded
 copy is a new message sent by a user, so it arrives intact. Three shapes reach
 that advice, and they are told apart deliberately:
 
 | What arrived | Answer |
 | --- | --- |
-| Reply from a sender marked as a bot | Telegram does not let bots read other bots' messages |
+| Reply from a sender marked as a bot | Telegram hid that bot's message; admin rights plus Bot-to-Bot Communication fix it |
 | Reply with a message id but no content field at all | That message reached me with no content |
 | No reply attached at all | Reply to the message you want to save — and if you did, Telegram did not pass it along |
 

docs/deploy-coolify-selfhosted.md

@@ -205,6 +205,30 @@ truth, so no separate command-menu file or manual registration step is
 required. See [Command discovery](../README.md#command-discovery) for how the
 menu text is built.
 
+## 4. Group setup
+
+By default a bot in a group runs in privacy mode. It receives only commands
+addressed to it, replies to its own messages, and service messages, and it
+cannot read messages sent by other bots. That breaks two things:
+
+- A bare `/command` typed as a reply to another bot's message is routed to that
+  other bot. Address this bot explicitly, as `/command@<this bot>`.
+- `/addsticker` and `/alias` replying to another bot's message (for example, an
+  image another bot posted) get the reply with its content stripped.
+
+To make both work in a group:
+
+1. In @BotFather, enable **Bot-to-Bot Communication Mode** for this bot.
+2. Promote the bot to **admin** in the group. Admins receive every message, so
+   no permissions beyond the defaults are needed.
+
+Disabling privacy mode in BotFather (`/setprivacy`) is the alternative to admin
+rights, but Telegram applies it only after the bot is removed from the group and
+added back. Admin rights take effect immediately. Verified on 2026-10-09:
+`/addsticker@<this bot>` replying to another bot's image failed with privacy
+mode off and the bot not re-added, and worked once the bot was promoted to admin.
+See Telegram's [privacy mode and bot-to-bot rules](https://core.telegram.org/bots/features#privacy-mode).
+
 ## Operations
 
 The live deployment is the Coolify container and MongoDB is the sole system of

docs/sticker-packs.md

@@ -113,6 +113,10 @@ exactly 512px with the aspect ratio preserved, uploaded as a PNG, and then
 added — attributed to the pack owner, matching the set it is about to join.
 Sources above 2 MB, or with either side above 4096px, are rejected.
 
+**Replying to another bot's image** works only after the
+[group setup](deploy-coolify-selfhosted.md#4-group-setup); otherwise Telegram
+strips the image out of the reply.
+
 ## Video and GIF
 
 A replied video, GIF, animation or video note is downloaded and transcoded with