android, desktop, ios: show clear error when saving group profile fails (#7090)

The API.Error branch in apiUpdateGroup rendered "$r.err", printing the API.Error object reference plus a literal ".err" instead of the error message. Use "${r.err.string}" so the actual error is shown.

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt

@@ -2289,7 +2289,7 @@ object ChatController {
     return when {
       r is API.Result && r.res is CR.GroupUpdated -> r.res.toGroup
       r is API.Error -> {
-        AlertManager.shared.showAlertMsg(generalGetString(errorTitle), "$r.err")
+        AlertManager.shared.showAlertMsg(generalGetString(errorTitle), "${r.err.string}")
         null
       }
       else -> {

plans/2026-06-17-fix-group-garbled-error.md

@@ -0,0 +1,27 @@
+# Fix garbled error when saving group profile (member admission)
+
+## Problem
+
+Saving a group profile change — e.g. enabling member admission (Review = "All") from Group preferences → Member admission — can fail with an unreadable alert:
+
+```
+chat.simplex.common.model.API$Error@3ea295c.err
+```
+
+The user sees an object reference instead of the actual error, so there is no way to tell what went wrong.
+
+## Cause
+
+In `apiUpdateGroup` the `API.Error` branch builds the alert message with `"$r.err"` (`SimpleXAPI.kt:2292`). In a Kotlin string template `"$r.err"` interpolates `r.toString()` — and `API.Error` has no custom `toString`, so it yields `chat.simplex.common.model.API$Error@<hash>` — then appends the literal text `.err`. The meaningful message (`r.err.string`) is never read.
+
+This surfaces whenever the core rejects the update. A concrete trigger is a **desynced member role**: the client shows the Save controls because `groupInfo.isOwner` is true, but the core's `assertUserGroupRole gInfo GROwner` (`Commands.hs:3840`) disagrees and returns `CEGroupUserRole`. The display bug then hides which error it was.
+
+## Fix
+
+Render the error message instead of the object reference:
+
+```kotlin
+AlertManager.shared.showAlertMsg(generalGetString(errorTitle), "${r.err.string}")
+```
+
+One-line change in `SimpleXAPI.kt`. This is the only occurrence of the `"$r.err"` pattern in the codebase. The underlying core rejection is unchanged — but it is now shown clearly to the user.