[HIGH] Group message send failure silently discards the typed message

[KruGoL]

Summary

GroupChatModule.sendMessage in the SDK never throws on publish failure — it catches and returns null (verified in the installed SDK: logger.error("GroupChat", "Failed to send message", error); return null). The mutation wraps it as return !!message, so it resolves with false instead of rejecting; onSuccess runs unconditionally and clears the input (setMessageInput('')), and the global mutation onError toast never fires. The user's typed group message is gone with zero feedback.

Where

src/components/chat/hooks/useGroupChat.ts:367.

Fix (app-side, immediate)

In mutationFn: if (!message) throw new Error('Failed to send message') so the global onError toast fires and onSuccess (input clearing) is skipped. Apply the same guard to the mini-chat/DM send flows and to deleteMessage/kickUser/createGroup (all fail silently today).

Companion SDK improvement (optional)

The proper upstream fix is for GroupChatModule.sendMessage (and the moderation methods) to surface failures — throw, or return a typed { ok: false, error } — instead of swallowing them and returning null. Tracked separately in the SDK repo.

Found by multi-agent audit @ main b477d4d; adversarially verified.

[KruGoL]

Merged into the audit-fixes-2026-07 integration branch (fix/group-send-throw-on-null).

Done (send path — the data-loss bug):

• New shared guard src/components/chat/utils/requireSent.ts turns a silent null SDK result into a rejection. The group send mutation now calls it, so on failure onSuccess (which cleared the input) is skipped and the global onError toast fires — the typed message is preserved.
• sendMessage catches the rejection and returns false so the click handler doesn't also raise an unhandled rejection (was a duplicate Sentry report).
• 5 unit tests for requireSent. Full suite green (392), tsc + lint clean. No wallet/storage change.

Deliberately out of scope (follow-ups):

• Moderation actions (deleteMessage/kickUser/deleteGroup) also fail silently, but the SDK returns boolean false there (verified: deleteGroup → return false), so they need a throw-on-falsy guard, not the null-only requireSent.
• DM / mini-chat send flows (a separate audit finding).

The SDK-side proper fix (methods should signal failure instead of returning null/false) is still worth a companion issue in the sphere-sdk repo.