fix: signal handle dataMessage.reaction safely (#637) (thanks @neist)

CHANGELOG.md

@@ -35,6 +35,7 @@
 - iOS/Android: enable stricter concurrency/lint checks; fix Swift 6 strict concurrency issues + Android lint errors (ExifInterface, obsolete SDK check). (#662) — thanks @KristijanJovanovski.
 - iOS/macOS: share `AsyncTimeout`, require explicit `bridgeStableID` on connect, and harden tool display defaults (avoids missing-resource label fallbacks).
 - Telegram: serialize media-group processing to avoid missed albums under load.
+- Signal: handle `dataMessage.reaction` events (signal-cli SSE) to avoid broken attachment errors. (#637) — thanks @neist.
 - Docs: showcase entries for ParentPay, R2 Upload, iOS TestFlight, and Oura Health. (#650) — thanks @henrino3.
 
 ## 2026.1.9

src/signal/monitor.ts

@@ -144,6 +144,20 @@ function resolveSignalReactionTargets(
   return targets;
 }
 
+function isSignalReactionMessage(
+  reaction: SignalReactionMessage | null | undefined,
+): reaction is SignalReactionMessage {
+  if (!reaction) return false;
+  const emoji = reaction.emoji?.trim();
+  const timestamp = reaction.targetSentTimestamp;
+  const hasTarget = Boolean(
+    reaction.targetAuthor?.trim() || reaction.targetAuthorUuid?.trim(),
+  );
+  return Boolean(
+    emoji && typeof timestamp === "number" && timestamp > 0 && hasTarget,
+  );
+}
+
 function shouldEmitSignalReactionNotification(params: {
   mode?: SignalReactionNotificationMode;
   account?: string | null;
@@ -404,8 +418,11 @@ export async function monitorSignalProvider(
       }
       const dataMessage =
         envelope.dataMessage ?? envelope.editMessage?.dataMessage;
-      const reaction =
+      const reaction = isSignalReactionMessage(envelope.reactionMessage)
-        envelope.reactionMessage ?? dataMessage?.reaction ?? null;
+        ? envelope.reactionMessage
+        : isSignalReactionMessage(dataMessage?.reaction)
+          ? dataMessage?.reaction
+          : null;
       const messageText = (dataMessage?.message ?? "").trim();
       const quoteText = dataMessage?.quote?.text?.trim() ?? "";
       const hasBodyContent =